Russell Brown

R2AK 2018

Recommended Posts

This forum is the perfect place to help each other with all the challenges of this race. Navigation, communication, safety, and pedal drive systems.

My new pedal drive will use the Rick Willoughby system where the prop is on the end of a long flexible shaft. On my boat, the shaft will be almost 10 feet long and made from 5/16"spring stainless rod. I'm pretty sure that it was Rick that discovered that propellers are self-aligning and that as long as the shaft is not straight, a long flexible shaft can work. In his speed-record style boats there is one strut holding the shaft that is molded over a piece of Teflon tube. The strut can be folded up to bring the prop clear of the water. In my case, I may need more than one strut, but the idea is to be able to deploy the system by just dropping the shaft instead of having to insert the whole system through the slot and dogging it to the cockpit floor. Also, the chain will be well above the water, so a complicated sealed fairing will not be required.

My new system will be based around a pylon mounted to (and going through) the cockpit floor which will have the upper bearing, cranks and big sprocket near the upper end and the lower bearing mounted just below the cockpit floor so that the lower bearing, sprocket, and flexible shaft are below the underwing and accessed by the slot in the floor that the chain goes through.

I was exploring belt drive for the new system, but may stick with chain because of the better gearing options. My old system used a custom 73 tooth upper sprocket and a 13 tooth sprocket at the lower end. A 16" diameter x 14" pitch prop was recommended by my friend Brandon who used a program to predict the optimal gearing and prop size. I'll see if I can get a link to that program.

To make my whole system more complicated, I'll be mounting a winch and sheeting control base to the top end of my pylon. My boat has around-the-boom furling and reefing, so the main sheet comes from the end of the boom and it's hard to keep the sheet close enough to quickly release it. The screecher and spinnaker sheets will go the the winch (on the pylon) and the main sheet will cleat just behind the winch. The tiller has to pass under the main sheet and behind the pylon, so it will be a bit complicated, but my boat is very tender and I have had one too many panicked moments diving for the main sheet. With the new system, all bit the jib sheets will be very close to the driver.

One of the main challenges of my new system will be coming up with a bearing for the bottom sprocket. I'll use a bicycle bottom bracket bearing (and bicycle cranks) for the top bearing, but the bottom bearing will have to take the axial loads of the chain tension and the thrust of the propeller. I'll obviously need a custom fitting for the bearing that holds the sprocket (as I did with the old unit), but the new unit will have the shaft attached as well (probably through a universal joint, though there will be only a small amount of angle change between the shaft and the bearing). Any ideas about what kind of stock bearing I could use? Ideally it would be mounted flat to the aft face of the pylon with the shaft facing aft.

I'll share the details of this system as it develops.

  • Like 2

Share this post


Link to post
Share on other sites

So you are building a system similar to the one that was on Big Broderna?

I'd stick with chain drive, bicycle belt drive is not that mature of a system and is still finiky to make reliable.  Chains are cheap and will last the duration of the trip and are reliable and more efficient.

You want an angular contact bearing, they are designed for radial and axial loads.  A cheap and easy way to get them is to use a threadless bicycle headset for a 1" steerer.  This will press fit into a 1.25" x 0.035" steel tube and let you run a 1" shaft inside them.  You'd mount the lower bike cog to one side of the shaft and the universal joint to the other.  This is an example: https://www.universalcycles.com/shopping/product_details.php?id=48110

You would need a small lip on one side of the shaft that holds the bearing race in place, but it would be trivial to machine a clamp-on version from a shaft collar.

The other more common size would be for a 1.125" shaft.

I might have a spare (I used to build bikes frames as a hobby and be a bike mechanic, I have a basement machine shop full of bike parts) that I could send you.  

Share this post


Link to post
Share on other sites
On 1/8/2018 at 4:04 PM, Ishmael said:

I have never heard of anyone in the R2AK not being totally open  badass.

 

Share this post


Link to post
Share on other sites
1 hour ago, Russell Brown said:

I'm pretty sure that it was Rick that discovered that propellers are self-aligning and that as long as the shaft is not straight, a long flexible shaft can work.

Rick didn't discover it but he saw someone who had done it and copied it.

Then won an endurance speed record utilizing it.

He talks a lot about it on boatdesign.net in a "pedal power boats" thread.

  • Downvote 1

Share this post


Link to post
Share on other sites
3 hours ago, Russell Brown said:

My new pedal drive will use the Rick Willoughby system where the prop is on the end of a long flexible shaft.

This guy?  Many prototypes.  Image below is "V14".

http://www.rickwill.bigpondhosting.com/
https://www.youtube.com/user/RickWilloughby/videos
http://www.rickwill.bigpondhosting.com/V14.htm

V14_Port_Bow-s.thumb.jpg.7b58a39e269266d6a7032b7b503e36ed.jpg

 

This one (below) showed up as a Rick Willoughby pedal drive.  Not sure the boat (Team Take Me To The Volcano) finished in 2016?

Quote

I can't sail too hard on these with only 150 lbs buoyancy so...  (at 4:10)

 

  • Like 1

Share this post


Link to post
Share on other sites
On 1/6/2018 at 2:19 AM, galacticair said:

 

Curious about your viewpoint -- can you elaborate?  Tiring yes, but insane/risky, I'm not sure about.  All the big east coast distance races are on trapeze cats (Worrell, Tybee, Texas), as are the Hobie challenges.  On the Inter 20 we did have some initial problems with chafe in the trapeze height adjustment that led to several MOB in SF Bay (good practice), but we fixed that.  Though in the end we did have wings -- those were comfy and great downwind especially.

 It is all boils down to how tired you are at the end. All classical long distance races are more or less just a chain of day races. There is well defined finish and a rest period after a day. 

Adventure racing is different. It is about how far you can push yourself after the day is over. So, being less tired translates into less mistakes and more miles. 

The ability of thinking straight deteriorates quite dramatically along with tiredness setting in. 

Although I look at wings vs trapeze debate from solo sailor perspective.  Danger of solo trapezing is much greater than that of two-up team.  

At the dawn of Watertribe races I did EC on old wooden A-cat. Trapezing and all. I don’t want to repeat the experience. I also contemplated to do it on Nacra F17, way better boat for conditions, but I just didn’t feel I would be able to control it in all possible scenarios  and I couldn’t bring myself up to modifying my expensive racing toy. 

We did 2016 UF Challenge on Nacra 20 with wings and it was much more pleasant ride. 

So. Wings are safer. Sanity -insanity discussion is sort of moot at the greater scale of things :)

 

going back to to the current topic.

What is collective wisdom on Mirage drives for big boats? Do they work? I have seen quite a few pics with transom platforms and mirage drives fit. Success? Failure?

Share this post


Link to post
Share on other sites

taper roller bearings with a flanged housing will work fine. 

Share this post


Link to post
Share on other sites
8 hours ago, CrazyR said:

What is collective wisdom on Mirage drives for big boats? Do they work? I have seen quite a few pics with transom platforms and mirage drives fit. Success? Failure?

Good question. My boat will use two of them. I think the Mirage drives are particularly good for heavier boats. They can make a good amount of bollard pull. At higher speeds nothing beats a good prop. The Mirage drives are more efficient at lower speeds. There is a marketing video by Hobie showing one Mirage drive versus a two person kayak in a tug-o-war, but I have yet to see videos showing the Mirage drive besting props in any distance race. Another way to look at it, the Mirage drive is essentially a two foot diameter prop where the blades oscillate through ~120 degrees instead of continuously rotate - which is why they have such good low speed thrust.

Share this post


Link to post
Share on other sites

Umm bollard pull is when the boat is not moving. Speed = 0.  i design (among other things) tugboats. You pitch a tugboat prop for max bollard pull, and whatever free running speed you get is what you get after the prop is designed for zero speed condition.

I don't think it's very accurate to compare them to 2' diameter props. At the end of each stroke when the blade flips over to the opposite angle of attack there will be a period of low/zero/low thrust. So you are losing thrust at that point.

I would be surprised if a well designed prop was less efficient at any speed. Paddles are not props and are not very efficient. Otherwise ships everywhere would have with little flippers or paddle shaped fins moving in a oscillating motion. The closest the Mirage is to a commercially available product is a Voith Schneider drive. It uses vertical fins that are mounted on a horizontal disc in the hull. As the disc rotates, the fins angle of attack changes and you get thrust. They are about 80% as good as a decent prop.

The key to efficiency is the biggest, slowing turning prop you can reasonably fit. Hull/drive geometry usually dictates that.

If you look at human powered aircraft (Gossamer Albatross etc), they used props bigger than a Cessna, but were powered by < 1 HP. Cessnas would use bigger props but hitting the ground and cost probably limit them, as well as the requirement for a heavy gearbox to slow down the prop from engine RPM.

Share this post


Link to post
Share on other sites

For all those looking at pedal drive systems and associated propellers, I would take a good look at Graupner folding props: http://www.espritmodel.com/graupner-cam-folding-propellers.aspx.

The blades are thinner and lighter which is more efficient under low inflow conditions than even the ACP-E series. Given that they fold they are also more damage tolerant.

 

Share this post


Link to post
Share on other sites
22 hours ago, Alex W said:

So you are building a system similar to the one that was on Big Broderna?

I'd stick with chain drive, bicycle belt drive is not that mature of a system and is still finiky to make reliable.  Chains are cheap and will last the duration of the trip and are reliable and more efficient.

You want an angular contact bearing, they are designed for radial and axial loads.  A cheap and easy way to get them is to use a threadless bicycle headset for a 1" steerer.  This will press fit into a 1.25" x 0.035" steel tube and let you run a 1" shaft inside them.  You'd mount the lower bike cog to one side of the shaft and the universal joint to the other.  This is an example: https://www.universalcycles.com/shopping/product_details.php?id=48110

You would need a small lip on one side of the shaft that holds the bearing race in place, but it would be trivial to machine a clamp-on version from a shaft collar.

The other more common size would be for a 1.125" shaft.

I might have a spare (I used to build bikes frames as a hobby and be a bike mechanic, I have a basement machine shop full of bike parts) that I could send you.  

I never saw the system on Broderna, but now I wish I had. Was it a flexible shaft?

Your idea of using a head set bearing is brilliant and the unit that you linked to looks like it could work. A 1" shaft could work for mounting both the shaft and the small sprocket.

I'm happy to get your reinforcement on using chain instead of a belt. I know that the gear ratios I used last time worked and I don't want to mess with that. Finding the large chain ring is another puzzle. Somebody makes them, but I think they are custom. The video of "Take me to the Volcano" that Proa posted shows a large chain ring. Does anyone know how to get in touch with Matt Johnson? It would be nice to have a chain ring made that was a bit tougher than my old one because it will be prone to damage.

As with my old unit, the first step is to gather all the parts. That's what I'm doing now. Thanks to everyone who posted ideas and links. It helps a lot.

 

Share this post


Link to post
Share on other sites

Russell - the chainring is a custom. Nothing more than 57 tooth in off the shelf.  For One off CNC chainring you can look into these guys:  https://www.emachineshop.com/  You can use their specialized (free) CAD software to design it.

Or get Paul to draw you a big chain ring and have a local CNC shop fab it. You can cut it from steel rather than aluminum for toughness/damage resistance. If you go with aluminum it might make sense to make the inner half of the diameter thicker on one side to give it extra rigidity (sp). Pretty easy to machine it flat on a mill, just more machine time.

Share this post


Link to post
Share on other sites

Big chainrings need to be thicker as Zonker suggested.  Paragon Machine Works used to make them 20 years ago (they don't anymore) and would use 4mm (or maybe 3/16") thick 7075 aluminum that was milled down just where the chain rode on it.

If you can't find a CNC shop in PT that can make the chainring try talking to CycleFab in Seattle.  It is a custom machine shop that specializes in odd-ball bike stuff.  I'm friends with them and might be able to help convince them on a one-off project.  http://www.cyclefab.net/.  Garth is the one to talk to, he does most of the CNC and is a big bike nerd.  If huge off the shelf chainrings are still available somewhere they'll know where to get them.  Last time I looked I could find 60t, but not larger.

I took some photos of the Big Broderna pedal drive system when I stopped in PT last year, I'll post one tomorrow (it's on a computer that is at home).

Update: Greenspeed has some extra large chainrings at large pricing (in AU$, would be cheaper in USD): http://www.greenspeed.com.au/gsparts.html

 

Share this post


Link to post
Share on other sites
2 hours ago, Zonker said:

Nothing more than 57 tooth in off the shelf.

I haven't even begun to look but found these folks on page one of search results - many standard sizes listed, up to 125 teeth:

https://ablproducts.com/sprockets.htm
https://ablproducts.com/40-chain-sprocket.html

Hard to believe custom parts are needed?  I'm still inclined toward gears instead of a chain, though I like the long drive shaft idea instead of bevel gears at the prop.

drll.jpg.739c2190baa775316230a97e41836a78.jpg

Share this post


Link to post
Share on other sites

Those are for industrial sprockets though, not bike ones.  The chain will be a lot heavier and you'll have to make an adapter to mount them onto standard bicycle cranks.  By the time you make the adapter you might as well have made a custom chainring.

Share this post


Link to post
Share on other sites

The shaft on the HELIX PD™ isn't really long enough for bridge deck mounting, designed as it is for thru-hull mounting in a kayak.  Might be adaptable to a longer shaft?  Or the pedals used to power a long trailing Willoughby-style drive shaft.  Maybe the HELIX factory can sponsor an R2AK racer and offer long shaft conversion kits?

From the Helix PDTM Owner’s Manual:

WS_16_17_Helix_PD_Owners_Manuals.jpg.f6e6835f3f16fc0bc23d12cda6adfce6.jpg

One way or another, a chainless pedal solution is appealing to me.

Share this post


Link to post
Share on other sites
4 hours ago, Zonker said:

Nothing more than 57 tooth in off the shelf.

Any reason not to use a 10 Tooth Drive Sprocket ($7.87 on Amazon) with a 57 tooth chain sprocket to get a ratio (5.7) very nearly the same as Russell's 73/13 = 5.62?   (1.5% higher)  Having one custom made, if necessary, would be cheaper than a 73 tooth chain sprocket.

Quote

The 10 Tooth Drive Sprocket is what the motor chain on your 2-stroke 48cc or 66/80cc motorized bike engine rides on

DS10.jpg

Share this post


Link to post
Share on other sites
15 hours ago, Zonker said:

Umm bollard pull is when the boat is not moving. Speed = 0.  i design (among other things) tugboats. You pitch a tugboat prop for max bollard pull, and whatever free running speed you get is what you get after the prop is designed for zero speed condition.

I don't think it's very accurate to compare them to 2' diameter props. At the end of each stroke when the blade flips over to the opposite angle of attack there will be a period of low/zero/low thrust. So you are losing thrust at that point.

I would be surprised if a well designed prop was less efficient at any speed. Paddles are not props and are not very efficient. Otherwise ships everywhere would have with little flippers or paddle shaped fins moving in a oscillating motion. The closest the Mirage is to a commercially available product is a Voith Schneider drive. It uses vertical fins that are mounted on a horizontal disc in the hull. As the disc rotates, the fins angle of attack changes and you get thrust. They are about 80% as good as a decent prop.

The key to efficiency is the biggest, slowing turning prop you can reasonably fit. Hull/drive geometry usually dictates that.

Thanks for describing what bollard pull is, I'm not sure what point you were trying to make. Are you suggesting that Hobie has designed for max bollard pull? I mentioned bollard pull because the Mirage drive can develop more thrust than other systems at zero or low speeds. That means that it should do well on a heavier boat especially when against the wind and chop. If you can construct a custom pedal drive that swings a larger diameter prop then that would be even better, but for commercially available pedal systems, I think that the Mirage drive is going to be the best choice on boats that are heavier than... say a touring kayak. 

I do think it is accurate to compare them to 2' diameter props. Obviously they would not perform as well as a "proper" prop. They are made of flexible material and there is a period at the end of each stroke where they produce no thrust. When they are producing thrust they are rotating around a longitudinal axis just like a regular propeller - unlike the Voith Schneider drive system.  They are not paddles. During the power stroke they perform exactly as a propeller does, albeit with a less than optimum foil shape.

 

Share this post


Link to post
Share on other sites

Here is an off-the-shelf system http://www.h2proped.com/

I've never used it but I'm posting it because it looks adaptable to a variety of boat types and cockpit configurations with the flex drive. At $750.00 for a complete system it seems priced fairly too. I like that the gearing is compact. I can't comment on it's efficiency obviously, but the drive leg looks clean.

Alex W.'s posts are accurate and helpful on bike part specs.  There are many specs to consider if building your own system, and as Alex just pointed out you'll want to stick with a 3/32" pitch chain, chainrings and cogs. Also consider crank length, bolt pattern, BB spindle type and shell, pedal cadence targeted by gearing, etc, etc. I think Kim Bottles did a bunch of work on a pedal system a while back.

I have used the Mirage system and the low end torque does feel strong and I agree that might be a good thing on a relatively heavy sailboat. Installation, however, would be difficult on most sailboats.

Good luck to this year's competitors!

 

p1110301-2_orig.thumb.jpg.e1c625a49f3b926bfbec9a71444dd415.jpg

Share this post


Link to post
Share on other sites

Either one of those would be extremely entertaining in Seymour Narrows in a 25-knot northerly.

Share this post


Link to post
Share on other sites
25 minutes ago, Ishmael said:

Either one of those would be extremely entertaining in Seymour Narrows in a 25-knot northerly.

Those two craft should be in the Olympics. That's entertaining as hell. For Seymour Narrows against a big headwind you'd have to lay flat in the fin boat and hope the tide carries you along, and just go into sinker mode on the Aqua Skipper, or maybe try the one leg out straight move, that looked aero.

Share this post


Link to post
Share on other sites
3 hours ago, ProaSailor said:

Any reason not to use a 10 Tooth Drive Sprocket ($7.87 on Amazon) with a 57 tooth chain sprocket to get a ratio (5.7) very nearly the same as Russell's 73/13 = 5.62?   (1.5% higher)  Having one custom made, if necessary, would be cheaper than a 73 tooth chain sprocket.

 

Efficiency on 10t chain sprockets is a lower.  There are tests for this in old HPVA journals because the bike speed record holders (in enclosed recumbent bikes) also run into issues getting high enough gearing. I don't remember the numbers, just the rule of thumb that 11t efficiency is bad and 10t is even worse.  They usually use a jack shaft to compound two chain systems. 

Having said that: I have a 56t ring that I'll also give to any r2ak racer (Russ gets first dibs) if they want to try this approach. 

Share this post


Link to post
Share on other sites

Here is the chain drive efficiency article:  http://www.ihpva.org/HParchive/PDF/hp50-2000.pdf 

52-11 at high output (175w, 60rpm) is 95.5% efficient, 52-15 is 97.5% efficient.  That is a pretty big difference, but it doesn't show us how small changes matter.  It isn't linear, 52-21 is 98.2% efficient.  60rpm is slow and it seems to be worse at high RPMs. 

Considering that the pedal drive shouldn't get days of use on most boats it might be a reasonable tradeoff.  It also seems like a larger prop would allow for a lower gear to be used. 

Share this post


Link to post
Share on other sites
1 hour ago, lasal said:

I have used the Mirage system and the low end torque does feel strong and I agree that might be a good thing on a relatively heavy sailboat. Installation, however, would be difficult on most sailboats.

 

Hobie came up with standup variation of the mirage drive recently. It called Mirage Eclipse.  Installing such variant isn’t all that difficult in theory. Just add two feet long platform to transom to fit the drive(s) in. There is a problem with weight distribution, of course.

just an idea...

 

 

Share this post


Link to post
Share on other sites

I'm a bit dumbfounded at all the pedal drive information that has been posted since I left for work this morning. I agree that I should have a custom chain ring made. I would like to make it robust. Probably still aluminum, but thicker than standard and beveled at the teeth. When I figure out what size to shoot for, I'll ask for help with the design. Alex W, are you willing? I won't go smaller than 13 teeth for the lower sprocket and if I want to use similar prop diameter & pitch, I'll probably end up with at least a 65 tooth chain ring. I was a bit lugged down before ( about 60 RPM), so I think I could go a bit smaller on the chain ring.

I have a shop neighbor that could CNC cut and bevel the chain ring. Paul Zeusche, who make the connective hardware for our nesting dinghies can probably be talked into fabricating the lower bearing shaft and associated hardware. 

I would really like to see a photo of Broderna's system if you have one Alex. Last time I saw Broderna, they were parked on the tip of Saturna with a pedal drive failure. I made the mistake of trying to pedal over a big current hump right there and as a result I didn't much feel like pedaling for the rest of the trip. i did come fairly close to catching them at the end of the following day though.

 

Share this post


Link to post
Share on other sites
31 minutes ago, olsurfer said:

Was wondering when the jack-shaft option would surface. When we raced out at Battle Mt you needed ridiculously high gears (250 inches) for top speed and low enough gears to get the bike rolling. Having a wide selection of gears is a plus to match the gearing with your energy level. The issue might be enough room for the jack-shaft assembly on a boat.

Here's my old carbon/kevlar monocoque front wheel drive speedbike 'Coyote' I built. I had the jackshaft system that allowed me to have 50 different gears to choose from. It worked for me cuz I was the first guy over 50 years old to go faster than 50mph in the world. As far as I know, my Coyote is still the fastest streetable streamliner in the world. There are way faster streamliners nowdays but they are so specialized you can only ride them on a closed race course and you need help starting and stopping. I needed no help riding mine and have ridden over 50,000 miles on the dog!

Dean.Coyote.wheeltape.jpg

coyote.jpg

th.jpg

Dean, Is that you? That's the coolest bike that I have ever seen. What does it feel like going 50 on a bicycle?

I have been doing a bit of internet searching myself and I found what is by far the coolest pedal drive system I have ever seen. I'm kidding, kind of... https://www.youtube.com/watch?v=Dne6h_hQfUc

 

Share this post


Link to post
Share on other sites
On 1/10/2018 at 7:21 PM, Russell Brown said:

This forum is the perfect place to help each other with all the challenges of this race. Navigation, communication, safety, and pedal drive systems.

My new pedal drive will use the Rick Willoughby system where the prop is on the end of a long flexible shaft. On my boat, the shaft will be almost 10 feet long and made from 5/16"spring stainless rod. I'm pretty sure that it was Rick that discovered that propellers are self-aligning and that as long as the shaft is not straight, a long flexible shaft can work. In his speed-record style boats there is one strut holding the shaft that is molded over a piece of Teflon tube. The strut can be folded up to bring the prop clear of the water. In my case, I may need more than one strut, but the idea is to be able to deploy the system by just dropping the shaft instead of having to insert the whole system through the slot and dogging it to the cockpit floor. Also, the chain will be well above the water, so a complicated sealed fairing will not be required.

My new system will be based around a pylon mounted to (and going through) the cockpit floor which will have the upper bearing, cranks and big sprocket near the upper end and the lower bearing mounted just below the cockpit floor so that the lower bearing, sprocket, and flexible shaft are below the underwing and accessed by the slot in the floor that the chain goes through.

I was exploring belt drive for the new system, but may stick with chain because of the better gearing options. My old system used a custom 73 tooth upper sprocket and a 13 tooth sprocket at the lower end. A 16" diameter x 14" pitch prop was recommended by my friend Brandon who used a program to predict the optimal gearing and prop size. I'll see if I can get a link to that program.

To make my whole system more complicated, I'll be mounting a winch and sheeting control base to the top end of my pylon. My boat has around-the-boom furling and reefing, so the main sheet comes from the end of the boom and it's hard to keep the sheet close enough to quickly release it. The screecher and spinnaker sheets will go the the winch (on the pylon) and the main sheet will cleat just behind the winch. The tiller has to pass under the main sheet and behind the pylon, so it will be a bit complicated, but my boat is very tender and I have had one too many panicked moments diving for the main sheet. With the new system, all bit the jib sheets will be very close to the driver.

One of the main challenges of my new system will be coming up with a bearing for the bottom sprocket. I'll use a bicycle bottom bracket bearing (and bicycle cranks) for the top bearing, but the bottom bearing will have to take the axial loads of the chain tension and the thrust of the propeller. I'll obviously need a custom fitting for the bearing that holds the sprocket (as I did with the old unit), but the new unit will have the shaft attached as well (probably through a universal joint, though there will be only a small amount of angle change between the shaft and the bearing). Any ideas about what kind of stock bearing I could use? Ideally it would be mounted flat to the aft face of the pylon with the shaft facing aft.

I'll share the details of this system as it develops.

You may also want to check out parts from RC Inboard racing boats.   The old school transom drives used flex shafts, like you were describing as well as thrust bearings that you are looking for.   Most now are straight shafts for surface piercing drives with the prop half in the water.  The big models use motors originally from weed eaters, so the hardware should be scaled up to the size you are looking for.

Example website for parts:

https://www.bonzisports.com/hardware/out-drive

Stumbling

 

 

Share this post


Link to post
Share on other sites

Russell, have you looked into glass bearings for the underwater drive?  This peddle boat deal is fascinating, but it seems that you gain so much speed sailing that every effort should be directed toward the wind.  Good luck.  Aloha, Guerdon.

Share this post


Link to post
Share on other sites
7 hours ago, lasal said:

Here is an off-the-shelf system http://www.h2proped.com/

I've never used it but I'm posting it because it looks adaptable to a variety of boat types and cockpit configurations with the flex drive. At $750.00 for a complete system it seems priced fairly too. I like that the gearing is compact. I can't comment on it's efficiency obviously, but the drive leg looks clean.

I have used the Mirage system and the low end torque does feel strong and I agree that might be a good thing on a relatively heavy sailboat. Installation, however, would be difficult on most sailboats.

The Proped with its flex cable, two 90 degree gearboxes and belt drive has got to be the least efficient pedal drive available - but easiest to install. I agree that the Mirage drives are not easy to install, especially into a sailboat. 

Here is an example of a novel solution for mounting a mirage drive; 

 

mirage transom.jpg

Share this post


Link to post
Share on other sites
On 1/10/2018 at 12:00 PM, CrazyR said:

Adventure racing is different. It is about how far you can push yourself after the day is over. ... The ability of thinking straight deteriorates quite dramatically along with tiredness setting in. 

...At the dawn of Watertribe races I did EC on old wooden A-cat. Trapezing and all. I don’t want to repeat the experience. ... We did 2016 UF Challenge on Nacra 20 with wings and it was much more pleasant ride. 

So. Wings are safer. Sanity -insanity discussion is sort of moot at the greater scale of things :)...

Good points on tiredness and how it relates to wings vs. trapeze on a beach cat -- that's definitely how we thought on the Nacra 20 last year. Having wings made it a lot more tolerable over 7.5 days especially since we weren't stopping much (I think we spent only ~15hrs on land in total, all weather/tides related).  

That's some serious adventure experience you have!  Must explain the screename... You should try R2AK on a beach cat, you could beat our time by a lot (there's lots of room to improve it, though weather always is the X factor).

Share this post


Link to post
Share on other sites
3 hours ago, galacticair said:

That's some serious adventure experience you have!  Must explain the screename... You should try R2AK on a beach cat, you could beat our time by a lot (there's lots of room to improve it, though weather always is the X factor).

I’m more of “let’s try something nobody have done yet” crowd than the speedy one. Although my observations shows that participants are generally on the spectrum. 

Now aside from the course itself, I need to solve a problem of commute from east coast and back, no more than a month of vocation time, and limited budget. Hmm. It looks like a Challenge. 

Share this post


Link to post
Share on other sites

Here is the Big Broderna pedal drive:

P1080744-X5.jpg

P1080745-X5.jpg

It looks like they a flexible shaft in a bent rigid housing that got it to the right place.  That's a little different than what I remembered, but still interesting to see.

I took photos of a bunch of boats last year at the PT pre-party, trying to see how they were doing human powered propulsion when I could:

http://photos.alexwetmore.org/Sailing/R2AK-2017-Boats/i-JQLFgM7

I'm happy to help with figuring out how to fit bike parts into sailing.  I'll send you a PM with my contact info too.

 

Share this post


Link to post
Share on other sites

Wow, I thought that my 2.2 lengths of chain was a lot. Broderna had chain running all the way across the cockpit from one unit to the other and then another chain running down to the unit. Thanks for the photos. That was the day I had my mast up and down 8 times.

Having seen the long, flexible shaft used on the Willoughby style systems, does anyone have reservations about them? My reasons again for going that direction is that it will be very fast to deploy and retract, the chain will be out of the water, and the resistance will be lower than having the prop on the end of a leg or strut. I never could find it, but my friend Brandon was telling me about an underwater video taken looking back at the shaft and prop while pedaling up a shallow river. The prop was bouncing off of rocks and the shaft was bending to stay in the wake of the boat when turning. 

It's a bit counterintuitive to put a propeller on the end of a long noodle, (I never would have thought of it) but it's one of those things that could be way better than one would imagine, even for a pretty big boat that needs a reliable system.

Thanks again for all the help and ideas...

Share this post


Link to post
Share on other sites

Here is a great program for figuring out the optimized propeller size, rpm and geometry. https://www.mh-aerotools.de/airfoils/javaprop.htm It was recommended by Rick Willouby and he has directions somewhere online to help set it up properly.

Attached are some a pictures of custom props we machined up, and the old and new peddle drive seats we put on Felix.... the old one we lent to the Bird Brothers last year on Mama tried.

The drive unit itself has two helical bevel gears and a shaft between them and looks like an outboard drive.  Its also very similar to the unit that Mad Dog used.  The bevel gear units are very industrial and rated for continuous use at the torque we have them under... but they are not rated for saltwater and thus some care needs to be given to them.  They are very efficient and we can manage 4 knots for an hour or so if you switch ped;ers often.  3.5 knots is a better long distance pace that we can do pretty much indefinitely by switching off every hour. Our max speed under pedal drive alone is 6 knots... but that is only for a few long seconds. 

One of the things that is really nice about this type of setup is that it can be deployed or retracted at a moments notice.  To give an idea of what this is like this is what happened on our boat- When the wind is blowing 0-4 knots we found ourselves constantly going in and out of motor sailing mode.  In 0-2 knots of breeze we are mostly pedaling and getting 3-4 knots.  If we get a little more wind, 2-3 knots, then we are motor sailing and barely putting any pedaling effort into it but still getting 4-6 knots of boat speed.  With 4+ knots of wind we retract the drive and are sailing 5-6 knots+.  Our rule of thumb was that we never would let boat speed drop bellow 4 knots...if it did we would put in the pedal drive and keep our speed up.  All in all it is a really cool and fun dynamic to play with while sailing in the light stuff.

 

 

new props.jpg

seat2.jpg

Pedal Drive 2.jpg

Share this post


Link to post
Share on other sites

The other thing we found is that by having the prop forward facing it is much less apt to catch weeds.  There is a lot of floating eel grass on the course which loves to get caught on all the underwater appendages.  The forward facing blades seem to fling the eel grass aside as opposed to getting caught and spinning around the hub.

Share this post


Link to post
Share on other sites
2 hours ago, foiledagain said:

The drive unit itself has two helical bevel gears and a shaft between them and looks like an outboard drive.  Its also very similar to the unit that Mad Dog used.  The bevel gear units are very industrial and rated for continuous use at the torque we have them under... but they are not rated for saltwater and thus some care needs to be given to them.  They are very efficient and we can manage 4 knots for an hour or so if you switch ped;ers often.  3.5 knots is a better long distance pace that we can do pretty much indefinitely by switching off every hour. Our max speed under pedal drive alone is 6 knots... but that is only for a few long seconds. 

[...SNIP...]

seat2.jpg

Pedal Drive 2.jpg

Very cool.  Does the small chain sprocket spin a bevel gear that turns the driveshaft to the prop?  Do you mind telling us how many teeth you have in your two sprockets, and/or the gear ratio between them?  Custom parts?  Is there any further gear reduction (multiplication?) between bevel gears to achieve an overall ratio in the range {5 to 5.6) that Russell is talking about?  Any photo of those top bevel gears?  Video of deploy/retract and in use?  Oh, here it is:

Looks like it worked well.  Quiet.  ;)

Share this post


Link to post
Share on other sites

What is the efficiency like of the bevel gear systems?  I also wonder what the efficiency loss is of flexible drive shafts.

There really isn't any reason for the cyclist to face forward and sitting sideways (like on Big Broderna) makes the system easier to design.

Share this post


Link to post
Share on other sites

I hadn't seen that video yet... thanks!

We have a 5-1 ratio for our boat.... but their really is an optimized prop diameter and rpm for every boat depending on the power needed to go a certain speed that you are optimizing for.

The helical bevel gears are one to one and have a 2% loss per unit.  The straight bevel gears are more like 5% loss for a one to one--- we used those the first year and helical the second year.

Share this post


Link to post
Share on other sites

The good helical bevel gear units are pretty pricey.... around $200 each.  The rest of the bits we made or boughtt from MSC direct.  With two bevel gears you could sit sideways or forward facing although forward facing makes it a lot easier to design in the kick up mechanism

I really liked Russell's drive unit from last year because it was so simple and the parts were off the shelf bike components.

Share this post


Link to post
Share on other sites
4 hours ago, Russell Brown said:

Wow, I thought that my 2.2 lengths of chain was a lot. Broderna had chain running all the way across the cockpit from one unit to the other and then another chain running down to the unit. Thanks for the photos. That was the day I had my mast up and down 8 times.

Having seen the long, flexible shaft used on the Willoughby style systems, does anyone have reservations about them? My reasons again for going that direction is that it will be very fast to deploy and retract, the chain will be out of the water, and the resistance will be lower than having the prop on the end of a leg or strut. I never could find it, but my friend Brandon was telling me about an underwater video taken looking back at the shaft and prop while pedaling up a shallow river. The prop was bouncing off of rocks and the shaft was bending to stay in the wake of the boat when turning. 

It's a bit counterintuitive to put a propeller on the end of a long noodle, (I never would have thought of it) but it's one of those things that could be way better than one would imagine, even for a pretty big boat that needs a reliable system.

Thanks again for all the help and ideas...

I would be concerned with fatiguing of the flexible shaft, as well as the strut that is holding the thrust bearing.   Engineering types can calculate up the fatigue wear on the shafts and struts, but you really don't know until you try.   I would think you would want to have a spares from your output drive all the way back (or forward, depending on orientation) to the propeller.   The strut would have to be beefier than the Willoughby pictures to be a little more debris resistant.

I would think something more like a long-tail/mud-motor out drive would be a more robust system:

HomePage_Longtail.jpg

There would be a lot of lightening involved to come up with a more sailboat friendly drive, and I would also have some floatation built in to the cavitation plate.   You could even have a universal or flex plate at the top and let it float up and down on the water.   Again, this is designed to screw itself through a range of fluids from water to mud.   A R2Ak outdrive could be much lighter, yet be able to ride up and over a dead head (floating tree, not a floating trippy person) with no damage to the strut or prop.

Stumbling

Share this post


Link to post
Share on other sites
1 hour ago, foiledagain said:

The helical bevel gears are one to one and have a 2% loss per unit.  The straight bevel gears are more like 5% loss for a one to one--- we used those the first year and helical the second year.

"per unit" means per pair?  2% at the sprocket bevel pair and 2% at the prop bevel pair = 4% total?

51 minutes ago, foiledagain said:

The good helical bevel gear units are pretty pricey.... around $200 each.  The rest of the bits we made or boughtt from MSC direct.  With two bevel gears you could sit sideways or forward facing although forward facing makes it a lot easier to design in the kick up mechanism

I really liked Russell's drive unit from last year because it was so simple and the parts were off the shelf bike components.

Four bevel gears = $800?  Or is it $200 per pair?  That custom 73 tooth chain ring Russell used must cost a few bucks, eh?

I can see (I think) how the small sprocket axle works as the pivot for the kick up mechanism...?  Using a long trailing shaft instead of your vertical strut, Is there any way to drive that top bevel system directly with pedals at 5:1, without a chain?

Share this post


Link to post
Share on other sites

The bevel gear units were about $200 each and two were needed for the drive=$400

The chain ring was donated from another pedal boat project

From what I can tell the flex shafts are very well proven-  A few human powered world records have been set on them, and Matt from Team Take me to the Volcano used one last year to get to Victoria in second place. For these drives they have one bevel gear that the shaft connects to. Rick W has really thought these drives through and also has the practical experience from people using his designs.  The flex shaft that Russell was talking about is a special Stainless alloy that --more ling a spring steel-- that can take the cyclical bending. 

Share this post


Link to post
Share on other sites

They do make bevel gears with reduction gears.  I have seen an off the shelf 2:1 and 4:1 unit but they need to be the next size up to handle the torque.... thus they go from being a 2.2 lbs unit to a 9 lbs unit and the price goes from ~$200 to ~ $800 each.

Share this post


Link to post
Share on other sites
16 minutes ago, foiledagain said:

They do make bevel gears with reduction gears.  I have seen an off the shelf 2:1 and 4:1 unit but they need to be the next size up to handle the torque.... thus they go from being a 2.2 lbs unit to a 9 lbs unit and the price goes from ~$200 to ~ $800 each.

Ouch!  Thanks very much.  Good info.

Share this post


Link to post
Share on other sites

I have a Rick Willoughby designed and built electric belt driven driveshaft on my Proa. And we have talked about pedal drives and even combo drives, where you can switch between electric motor or pedals or use both.

To help answer some of the general queries on this thread:

The main reason why most drive Shaft systems are one offs on yachts is because all the kayak gear is too short shafted to be of any real use. And their durability under heavy loads over long hours of use is suspect.

Nothing wrong with belt drives, but they do come in standard lengths and therefore limits you r design options. A chain drive you can make any length you want.

Chain/belt drives are a lot cheaper than gearbox drives. But gearbox/Shaft drives mean that you can design them to rotate the head/pedals around so that you can pedal normally (ie not back pedal) on either side or go fore and aft, like Felix.

If you have a strut drive setup, through a hole in the cockpit floor, you are limited to a two bladed props, and is complicated/fiddly to deploy/ lift up frequently, as you would need to in R2AK. If your prop jams in the  wrong place or you have weed/ debris which stops you from lifting the leg out to clear it, it means you have to go over the side to sort it. In Seymour Narrows?

In principle, what Russell is trying to do is the way to go. A long shaft rigid or flexing/curved, trailing out the back makes it easy to lift and drop. And clear debris or repair anything at the prop end. And you can try wide bladed and 3 or even 4 .bladed props if you want/need to.

Russell, if you want Rick’s contact details, PM me. Brandon can give you them as well.... You should also look a at some of the Brazilian web sites for long tail gear, pretty agricultural, but they even do fold up drives. You might be able to cannibalise some bits for your purposes. And finally have a good look also Bad Kitty’s setup. Theirs is surface piercing, but could be made to work “conventionally”.

i would be interested to hear what Zonker thinks of surface piercing prop setups like Bad Kitty’s?

And I would be interested to know how well flexible curved shafts work in reverse?

Rob

Share this post


Link to post
Share on other sites
1 hour ago, Sidecar said:

And finally have a good look also Bad Kitty’s setup. Theirs is surface piercing, but could be made to work “conventionally”.

i would be interested to hear what Zonker thinks of surface piercing prop setups like Bad Kitty’s?

I was looking at these photos of Bad Kitty's pedal drive, cropped here from these images in Alex W's folder (above):

They have an extra seat forward, near the dagger board on each side, with pedals below a hatch.  Unclear if it's direct drive or there is gearing somewhere?

P1080728-c.thumb.jpg.96c8dc4396ab143061762121a298129a.jpgP1080727-c.thumb.jpg.e4ddb8756ef42057732bb8225ce1080a.jpg

Russell, you are in the top-right corner of the last photo...  too big to add here, see next post.  See links for high resolution.
http://photos.alexwetmore.org/Sailing/R2AK-2017-Boats/i-cz3jdgB/A

Share this post


Link to post
Share on other sites
1 minute ago, ProaSailor said:

I was looking at these photos of Bad Kitty's pedal drive, cropped here from these images in Alex's folder (above):

They have a seat on each side with pedals below a hatch.  Unclear if it's direct drive or there is gearing somewhere?

P1080728-c.thumb.jpg.96c8dc4396ab143061762121a298129a.jpgP1080727-c.thumb.jpg.e4ddb8756ef42057732bb8225ce1080a.jpg

For what its worth, my naval architect friend, who has designed pedal driven race boats, says you want the largest diameter, slow turning prop you can accommodate.

Share this post


Link to post
Share on other sites
6 minutes ago, Left Shift said:

For what its worth, my naval architect friend, who has designed pedal driven race boats, says you want the largest diameter, slow turning prop you can accommodate.

On that basis, for the same overall prop depth, surface piercing is the way to go? Rick Willoughby won’t agree. Hence my query to Zonker....

Share this post


Link to post
Share on other sites

Bad Kitty's drive was really cool!  I am 90% certain it was 1:1 ratio which simplifies things.  I also like the way that there is no extra junk in the water and all they have to do to dissengage it is to stop the prop horizontal to the water...but they would lift it up further when really sailing.  I heard it can throw up quite a bit of spray though in the wrong conditions and I would really like to hear an expert chime in on the drag penalty for that.  From my memory, surface piercing drives have a sweet spot in efficiency above 30 knots.... but maybe in this low power application it is efficient.?

Share this post


Link to post
Share on other sites

I am guessing, but it looks as though Bad Kitty’s setup can/could be made to be lifted tight under the tramp, so minimal drag when compared to the ease of deploy/retract?

Share this post


Link to post
Share on other sites
21 minutes ago, Sidecar said:

 

This dosn't really line up with the numbers java prop spits out... in java prop you will see that the efficiency starts to plateau-- for Felix the optimal diameter is around 24" but the efficiency starts to plateau way before that so that the 20" prop we have is within .8% of the efficiency of the 24" one.  Everything on a boat is a compromise.

Share this post


Link to post
Share on other sites

Totally agree about everything being a compromise.... As I said above, I can see how you could do A Bad Kitty set up conventionally.

Is Javaprop set up to deal with surface piercing? Half the tropical world seems to use surface piercing long tails in isolated places where fuel isn’t easily obtainable or cheap. I don’t know, hence the question.

What do the Bad Kitty guys have to say? They aren’t exactly inexperienced and uninformed, they must have based their final choice on something? Maybe they tried it conventionally as well?

Share this post


Link to post
Share on other sites
46 minutes ago, Sidecar said:

Totally agree about everything being a compromise.... As I said above, I can see how you could do A Bad Kitty set up conventionally.

Is Javaprop set up to deal with surface piercing? Half the tropical world seems to use surface piercing long tails in isolated places where fuel isn’t easily obtainable or cheap. I don’t know, hence the question.

What do the Bad Kitty guys have to say? They aren’t exactly inexperienced and uninformed, they must have based their final choice on something? Maybe they tried it conventionally as well?

Ya!   I would really like the numbers to work out for the Bad Kitty type of drive because it is very elegant and could work for a lot of different boats.

Javaprop dosn't work for surface piercing props...I think a prediction software that could predict this would be pretty advanced.  It would be simpler to just go out and measure the forces directly.  You could do this by pulling the boat with a digital scale to measure resistance at different speeds, and then compare that to the power at the pedals using one of those power meter pedals that bike racers train with.  

Share this post


Link to post
Share on other sites

BK's drive is 1:1 and very simple, which is nice. The bonus is that they can have "gears" by adjusting how much of the blade is in the water.

My main concern when I first saw it was the blade eventually snapping off at the base as it's quite thin and subject to cyclic loading an appeared to be flexing quite a bit but it looks like they have it figured out ;)
I also wonder what it feels like as you wouldn't have a steady resistance. At some point there is nothing in the water, which I am sure they have aligned to be when the crank is in line with the legs of the "engine".

It seems to work well enough!

Share this post


Link to post
Share on other sites

I think that the mastermind behind Bad Kitty's system said that one of the advantages of the surface piercing propellers is that the resistance is aligned with the pedals so that the prop clears the water at the point when the power is the lowest. I don't know much about the compromises, but after watching the system in action I wasn't attracted to it. There's a bit of thrashing going on.

I'd like to send a link to this thread to Rick and see what he has to say about it all. Whether I do a stiff shaft, or a flexible one, I think the same drive unit can be used. I could use a carbon tube for the drive shaft, but then a universal joint would be used at an angle that could induce some power loss. I don't want any more power loss (or cost) than I can afford and I can't afford much of either.

Share this post


Link to post
Share on other sites
3 hours ago, Sidecar said:
3 hours ago, Left Shift said:

For what its worth, my naval architect friend, who has designed pedal driven race boats, says you want the largest diameter, slow turning prop you can accommodate.

On that basis, for the same prop depth, surface piercing is the way to go? Rick Willoughby won’t agree. Hence my query to Zonker....

More than two blades would be better for surface piercing, wouldn't it?  Consistent surface area in the water at all times, like a conventional prop.  Just guessing.

The shock to those delicate blades of entering and leaving the water must waste some energy?

Share this post


Link to post
Share on other sites

....when pedalling you kind of using stored energy (food) - could there be an possibility to store electric energi in batteries in various ways - but it has to be made underway - not charged from land?  Solar panels - wind or water generators when sailing.... When we see the technical development that goes in to the pedal-drives - one can take it one step further?  Then we are talking an electric engine (no engines).

 

Maybe this will ruin the hole R2AK concept - so it could be another challenge - but it could lead to nice devlopments -and maybe even attract some money (again ruin the concept)...  or develope it...

 

Edited by SeaGul
more stupid ideas

Share this post


Link to post
Share on other sites
16 minutes ago, SeaGul said:

....when pedalling you kind of using stored energy (food) - could there be an possibility to store electric energi in batteries in various ways - but it has to be made underway - not charged from land?  Solar panels - wind or water generators when sailing.... When we see the technical development that goes in to the pedal-drives - one can take it one step further?  Then we are talking an electric engine (no engines).

 

Maybe this will ruin the hole R2AK concept - so it could be another challenge - but it could lead to nice devlopments -and maybe even attract some money (again ruin the concept)...  or develope it...

 

I like the idea, have thought of it myself but from what I have heard it would be a real hard sell. It would just be far too easy to add some solar or battery power to it. I do know there are at least a couple others that would love to have a category for electrics in R2AK.

Share this post


Link to post
Share on other sites
5 hours ago, ProaSailor said:

More than two blades would be better for surface piercing, wouldn't it?  Consistent surface area in the water at all times, like a conventional prop.  Just guessing.

The shock to those delicate blades of entering and leaving the water must waste some energy?

With absolutely no knowledge of props, conventional or surface piercing, I would intuitively agree that a 3, 4 or even more bladed surface piercing prop must help to even out power/resistance  and cadence surges.

What I like about the BK set up is the prop accessibility off the back plus the ability to use it with either surface piercing OR conventional props and any kind of prop you think is best as well. The front end can be belt or chain or gearbox driven to your preference or budget.

Russell, I have passed on a link to Rick Willoughby. I am pretty sure he will respond,......

Share this post


Link to post
Share on other sites
35 minutes ago, W9GFO said:

I like the idea, have thought of it myself but from what I have heard it would be a real hard sell. It would just be far too easy to add some solar or battery power to it. I do know there are at least a couple others that would love to have a category for electrics in R2AK.

As indicated in my original post # 154, I believe it is possible to have a combi drive system, one which can run electrically only, pedal only or both together. Also by freewheeling the prop whilst sailing, battery charging as well. I have this capability already in very limited form on my Proa.

Once I have the Proa’s sailing side sorted out, I intend to return to a Mk2 version drive shaft which is capable of doing it all.

Imagine doing R2AK with the motor removed/disabled and then do the return trip with it reconnected? All in the one unit.

This link gives a clue as to how it might be done, all in the space of a bike frame:

http://www.oz-ebikes.com/1800w_kit.htm

Changing gears to suit loads and recharging limits seems to be the way to go, but I am sure that there will eventually be much more eloquent solutions?

Share this post


Link to post
Share on other sites

i was thinking of an electric hybrid solution too...they make an electric bike add on kit where the motor lives in the area of the chainring that would be pretty easy to bolt on.  The controller could do the rest.  Of course it would only be for cruising and not r2ak legal.

Surging is a problem with waterborne pedal drives.  You can feel this and hear it while pedalling on the water and the prop is constantly changing rpm because during the peak of your power stroke you are puttimg more power to the pedals which makes the prop spin faster, while at the low you naturally slow down.  So the power is pulsed. A three or four blade prop will not help...its more about the biomechanics of pedalling.  This pulsing causes inefficiency because it is in effect changing the angle of attack of the foiled prop, going in and out of its efficient range. The easiest way to help this would be to conect two pedalers and offset their power strokes.  Also you could add a flywheel to balance out the pulses. Pro cyclers spend lots of training time learning how to spin efficiently and I guess one could train yourself to spin on the water but it is a lot harder.  On a road bike your momentum and spinning wheels act like a huge flywheel that help to even this out whereas on the water there is very little flywheel effect.  It also is a lot more of an efficiency loss because of the changing angles of attack the the prop blades are going through.  It would be analogous to sailing on a constant heading while the boat is surging in speed... the sails would never be trimmed properly because of the changing apparent wind.  So another efficiency tweak could be to have a varriable pitch prop matched to the power stroke somehow.

Share this post


Link to post
Share on other sites

Shimano had a product line back in the 80's called the "Biopace" crank which used eccentric chainrings that effectively changed the gear ratio a bit as you turned the pedals to offset the lack of biomechanical leverage when the crank arm are vertical on a bike. It wasn't a big help in practice but a similar concept could conceivably do a lot with the cyclic loads of a wave piercing prop. 

Share this post


Link to post
Share on other sites
5 hours ago, foiledagain said:

i was thinking of an electric hybrid solution too...they make an electric bike add on kit where the motor lives in the area of the chainring that would be pretty easy to bolt on.  The controller could do the rest.  Of course it would only be for cruising and not r2ak legal.

Surging is a problem with waterborne pedal drives.  You can feel this and hear it while pedalling on the water and the prop is constantly changing rpm because during the peak of your power stroke you are puttimg more power to the pedals which makes the prop spin faster, while at the low you naturally slow down.  So the power is pulsed. A three or four blade prop will not help...its more about the biomechanics of pedalling.  This pulsing causes inefficiency because it is in effect changing the angle of attack of the foiled prop, going in and out of its efficient range. The easiest way to help this would be to conect two pedalers and offset their power strokes.  Also you could add a flywheel to balance out the pulses. Pro cyclers spend lots of training time learning how to spin efficiently and I guess one could train yourself to spin on the water but it is a lot harder.  On a road bike your momentum and spinning wheels act like a huge flywheel that help to even this out whereas on the water there is very little flywheel effect.  It also is a lot more of an efficiency loss because of the changing angles of attack the the prop blades are going through.  It would be analogous to sailing on a constant heading while the boat is surging in speed... the sails would never be trimmed properly because of the changing apparent wind.  So another efficiency tweak could be to have a varriable pitch prop matched to the power stroke somehow.

Fascinating.  Very insightful.  A flywheel is the right idea but to be useful:

  1. it would have to be heavy and
  2. you need a way to add power to the flywheel from a surging power source (the pedals).

The electric hybrid equivalent of a flywheel would be a battery (or capacitor?) capable of driving an electric motor at constant speed very briefly - just a few seconds to smooth out the irregular input from the pedals that charge the battery.  For cruising, pedal power could be supplemented by solar and wind.

Share this post


Link to post
Share on other sites
1 hour ago, IStream said:

Shimano had a product line back in the 80's called the "Biopace" crank which used eccentric chainrings that effectively changed the gear ratio a bit as you turned the pedals to offset the lack of biomechanical leverage when the crank arm are vertical on a bike. It wasn't a big help in practice but a similar concept could conceivably do a lot with the cyclic loads of a wave piercing prop. 

I had a set, they were very weird but it might work well on the water at lower, more sustainable RPM's.

Rick may comment.

If he does, he'll say flex-shaft with a two bladed, "square",  folding prop all the way for light boats.

Huge benefits for water strikes in both flex-shaft and folding-prop.

Especially for light boats. No thrust bearing required, just lots of sea trials!

Less square for the big-boys (heavy boats).

The adjustable pitch props are nice for sea-trial tweeking.

Several good one's available in the R/C airplane section of your Internet shopping sites.

 

  • Downvote 1

Share this post


Link to post
Share on other sites

PS wrote:

  1. it would have to be heavy (flywheel)

Not necessarily. If the weight is carried on the outer perimeter.  Much more effective and doesn't need to be nearly as heavy.

But who wants to add weight to a racing boat... not me.

There are better solutions. 3/8 inch flex shaft is one of them.

  • Downvote 1

Share this post


Link to post
Share on other sites
1 hour ago, BarfBag said:

I had a set, they were very weird but it might work well on the water at lower, more sustainable RPM's.

Rick may comment.

If he does, he'll say flex-shaft with a two bladed, "square",  folding prop all the way for light boats.

Huge benefits for water strikes in both flex-shaft and folding-prop.

Especially for light boats. No thrust bearing required, just lots of sea trials!

Less square for the big-boys (heavy boats).

The adjustable pitch props are nice for sea-trial tweeking.

Several good one's available in the R/C airplane section of your Internet shopping sites.

 

Do not use Shimano bio-pace they are all wrong and damage the knees..  The oval rings of today are a different beast, are set up 90-degrees of what the old biopace were.  If you want to go this route, watch the Qring videos on you tube that are made by Rotor out of Spain. (search Rotor Qring).  I have used them for 3 years and have had more consistent wattage output when  in the saddle than with round rings.

Share this post


Link to post
Share on other sites
17 minutes ago, DHFiend said:

Do not use Shimano bio-pace they are all wrong and damage the knees..  The oval rings of today are a different beast, are set up 90-degrees of what the old biopace were.  If you want to go this route, watch the Qring videos on you tube that are made by Rotor out of Spain. (search Rotor Qring).  I have used them for 3 years and have had more consistent wattage output when  in the saddle than with round rings.

On a pedal boat?

What gearing, what prop, what shaft?

Share this post


Link to post
Share on other sites
57 minutes ago, DHFiend said:

Do not use Shimano bio-pace they are all wrong and damage the knees..  The oval rings of today are a different beast, are set up 90-degrees of what the old biopace were.  If you want to go this route, watch the Qring videos on you tube that are made by Rotor out of Spain. (search Rotor Qring).  I have used them for 3 years and have had more consistent wattage output when  in the saddle than with round rings.

 

Share this post


Link to post
Share on other sites
1 hour ago, DHFiend said:

Do not use Shimano bio-pace they are all wrong and damage the knees..  The oval rings of today are a different beast, are set up 90-degrees of what the old biopace were.  If you want to go this route, watch the Qring videos on you tube that are made by Rotor out of Spain. (search Rotor Qring).  I have used them for 3 years and have had more consistent wattage output when  in the saddle than with round rings.

I wasn't suggesting that Biopace was appropriate, just that an eccentric chainring designed in conjunction with the prop could yield a system that's both easier to pedal and produces higher power.

Share this post


Link to post
Share on other sites
4 hours ago, ProaSailor said:

A flywheel is the right idea but to be useful:

  1. it would have to be heavy and
  2. you need a way to add power to the flywheel from a surging power source (the pedals)

A flywheel on the prop shaft might be a good idea using a standard (advanced!?) mountain bike "super hub" to handle #2 above ("engagement"):

Superhubs: High Engagement, Silent & Low Friction

https://www.kappiuscomponents.com/collections/hubs  (Kappius: "1.5 degrees over 240 engagement points")

https://project321.com/product-category/bicycle/bicycle-hubs/
https://project321.com/new-drive-system/

Quote

Our standard 6×2 driver (6 pawls with 2 pawl engagement) boasts 216 points of engagement (1.66°).

 

Share this post


Link to post
Share on other sites

How can I git me some of that zero friction?

Share this post


Link to post
Share on other sites

Those qrings look great...I like how you can adjust them. It would not take long to see how well it works... I may have to try one out.

(the surging problem is not just an issue with surface piercing props... and I dont think a flex shaft eliminates it)

Share this post


Link to post
Share on other sites

Surface Piercing Props:  I've only used them on fast boats a few times. They are attractive for fast boats because:

- no appendage drag
- bigger prop diameter possible
- can eliminate the rudder (drag) if the drive steers as well

Cons:

- require a deep reduction ratio gearbox ($$/heavy) to get the big prop diameter
- costly
- conventional props won't work with them
- design knowledge is less so harder to get the right prop
- cost
- reverse performance can be poor
- poor start up performance (especially poor acceleration for low powered craft)

I suspect for human powered boats the "big prop diameter/low drag" is what makes them attractive

But if somebody came to me tomorrow and asked for design help, I would never use them because (a) I don't understand them well enough (b) I don't think available small off the shelf props are right for them (c) I don't think the flow regime for 4 knot props is right for a surface piercer. Generally they are also at a shallower angle of attack which is great for efficiency but harder to achieve from a multi beam/bridgedeck.


 

Share this post


Link to post
Share on other sites

Here is a video I took at the 2016 start in Victoria of Bad Kitty's splashy but seemingly well sorted prop system:

https://www.dropbox.com/s/qyo242dvhnrwi15/Bad_Kitty_Drive_2016.m4v?dl=0

It's too bad we can't see the boats start at a line just in order to see how the drive systems perform in the first kilometer or so. As it is it's basically a reverse grid where the fast boats from Port Townsend end up farthest in at the dock in Victoria and then are last to leave. I need post some more of these videos. I have an amazing one from Ogden Point of 2016 winners and overall record holder Mad Dog Racing on the M32 going ridiculously faster than everyone else in light air. I shall try to edit some clips together for YouTube.

Share this post


Link to post
Share on other sites

think that Hello... eh Bad Kitty splashing props will be a problem when you try to sneak up on something or someone...

 

The M32 is the tool for someone who like to suffer and are in for win or disaster...but they did break some masts before they  learn to handle that weapon..

Share this post


Link to post
Share on other sites

Hello Ace, Welcome to the forum! This seems like a pretty good place to get lots of perspectives on whatever questions you might have.

Because the race starts later this year, there could be less wind, which would give the advantage to the boats that are the easiest to human power. It seems that there are now 3 small and slippery trimarans entered solo.

I haven't entered yet. I have until Monday. Oh shit, that's tomorrow.

Share this post


Link to post
Share on other sites

Thank you for the welcome Russell. I just completed my application after realizing it was the 14th today.

Now there are no more excuses. :)

Daniel

Share this post


Link to post
Share on other sites
On 13/01/2018 at 2:24 PM, Russell Brown said:

 

I'd like to send a link to this thread to Rick and see what he has to say about it all. Whether I do a stiff shaft, or a flexible one, I think the same drive unit can be used. I could use a carbon tube for the drive shaft, but then a universal joint would be used at an angle that could induce some power loss. I don't want any more power loss (or cost) than I can afford and I can't afford much of either.

Russ

I have had a look through the thread.  The selection of drive and related engineering depends on many factors.  The curved shaft is a great option for an easily driven hull.  There is a good deal of detail in shaft selection and the connections with a curved shaft.  Fatigue criteria is a key selection criteria for the shaft.  Nearly all the racing boats using curved shaft that I have been involved with are using 5/16 (8mm) 17-7 stainless steel or purpose wound carbon shafts.  These two links show how I mount the shaft on a typical pedal boat - one video looking back and the other looking:

https://1drv.ms/v/s!Aq1iAj8Yo7jNgmnfhahhl-v6uanC

https://1drv.ms/v/s!Aq1iAj8Yo7jNgmisUcwqtv_qtj-h

These clips show a carbon shaft.  It is 12OD and 8ID.  Its torsional stiffness is 50% higher than an 8OD 17-7 stainless shaft.  It is about 1/3rd the weight of the stainless shaft.  It is highly compliant in bending due to the way it is wound - basically double bias cloth folded into a tube.  

Other features of this drive are the folding prop, the belt drive with 2X ratio, purpose made gearbox having 2.5X ratio, prop strut that takes thrust but allows for inspection and easy weed removal.  Clearly the prop is easy lifted out of the water to reduce drag if the boat was powered by a kite or sail.  However the folding prop does not have a lot of drag anyhow. In motor sailing mode when the blades are deployed it tends to want to drive the legs unless it is braked and the blades then fold.

Matt Johnson uses the same prop but we have not yet upgraded his drive to a belt with the 2.5X gearbox.  He is using a Mitrpak R-101 box with a massive chainring.  You can see the top of the chainring in this clip:

https://1drv.ms/v/s!Aq1iAj8Yo7jNgjUOddCx0NEH6S4K

We have a few of the purpose made boxes in use but my partner that supplies them from his Chinese factory has asked me to stop selling them because he is concerned I will sell the entire stock before he gets the Chines boat built.  He supplies the folding props that I sell.

The issues with a curved shaft are fatigue life and buckling collapse.  The 17-7 has a 10E7 fatigue strength of 560MPa.  So providing the stress range is less than this it will give good life.  I think there are now more than a dozen 17-7 shafts that have completed the MR340 and two have done the distance twice.  I have done over 500km with the carbon shaft I am now using.  It is intended for a high performance boat so the high torsional stiffness is a key requirement.

If there is no prop thrust bearing and strut that can absorb thrust, all the thrust it taken as compression in the small diameter shaft.  It is possible to run the shafts without a strut but the compression load increases the stress compared with just torque and cyclic bending stress.  With very high thrust applications the shaft actually becomes unstable in buckling and that overcomes the blade alignment forces and the prop wanders all over the place.

For pedal drives on an 8t catamaran I fitted a combination of Mitrpak boxes to large model aircraft props after observing the buckling issue with a curved shaft.  The eventual fold down drive legs were very effective.  Two people could sustain around 2.5kts. The first year on they gave considerable advantage up the Derwent in light, flukey winds.  In the photo below you can see the pedal drives folded up with the big two bladed prop resting on the seat back.  The first iteration were drop-in drives and there were times when the pedallers could not not slow the prop down to release cleats when they were motor sailing.  The idea of the prop thrusting against the transom then folding up when unloaded was an essential to avoid that condition.

To determine the best option takes some calculations and consideration of options.  The curved shaft is a great solution for easily driven craft.  However it needs to be engineered if it is going to be reliable.  My partner is still going through the production engineering steps for our commercial pedal boat but I have been fabricating belt drives for various boats.  I have included some links to photos of my fabricated drives that make use of Mitrpak R-102 boxes.  I provide drilling templates for these at no cost for non-commercial use.  I can supply any parts that you cannot acquire or make yourself.  Each one is specifically designed for the intended application.

https://1drv.ms/i/s!Aq1iAj8Yo7jNgVKzn6dDgCqYUUZo

https://1drv.ms/i/s!Aq1iAj8Yo7jNgmqGwrnfngs3Lvjq

https://1drv.ms/i/s!Aq1iAj8Yo7jNgmsi7dNbShlcAnhT

https://1drv.ms/i/s!Aq1iAj8Yo7jNgkwx3y3gKYkL8PN_

The design of the fabricated unit has evolved as we have evolved the design for the production unit:

https://1drv.ms/i/s!Aq1iAj8Yo7jNgmzqDE8DJsv_IEH-

Sadly the production unit remains a pretty picture.  

If you want to get into detail on a pedal drive for a specific application it is best to email me:

rickwill@bigpond.net.au

 

Peccadillo_3peaks.png

  • Like 2

Share this post


Link to post
Share on other sites