Pedal Powered Boats

Has anyone contemplated the idea of linear action pedals as oposed to rotary action? The mechanism could be placed lower in the boat along with a lower seat position. The pedals could be mounted on linear bearings or alternatively lever mounted. The mechanical details of this variation aside, what are the implicationss about the possible differences in human output?

 

Yes, there are some descriptions and photos of linear pedals way back in this mammoth thread. One or two systems have been built, I believe that there was at one time a commercial available linear pedal system. I suppose the Hobie system falls into this category, too, although the pedals go back and forth on an arc, rather than a linear slide.

 

Human powered subs have tried them in order to save space. It didn't work out to be very beneficial.

-Tom

 

Tom,

Why?

 

I have some description of the drive train on page 74 post #1108. The chain is a standard bicycle 1/2" x 3/32" multi-speed chain. The front chain ring is 52T driving a 16T sprocket. My gear box was free. I mounted the 16T sprocket onto a gear head that I salvaged from a broken Husqvarna straight shaft string trimmer. The gear head is a 13:19 ratio making my overall ratio 4.75 shaft revolutions per one rotation at the pedals. I started out with a 14T sprocket but the 16T puts me into a better RPM range. I started out with a 1/4" stainless steel drive shaft then upgraded it to a homemade carbon fiber drive shaft that I described in post #1140 on page 76. The new drive shaft lets me deliver more power to the prop. I started out with an APC 16x16 prop which is a little small for my boat. I changed it out for an APC 20x15E prop that I like much better. One issue is the gear head is about 55 degrees not 90 degrees. I twisted my chain about 25 degrees so the drive shaft leaves the gear head at 80 degrees with respect to the cranks and 10 degrees with respect to forward motion. The prop works well except when I get into a lot of weeds. I'd like to make a folding prop so I can coast a few seconds, shed the weeds then resume pedaling.

Pedal height: You are mounting between two hulls so you could mount the pedals a lot lower than I did.

Does that make sense? Let me know if you have questions.

Dave

 

I don't recall but have a feeling that it was a lack of significant gain for space saved. A poor cost/benefit result shall we say. You could research it via Google though.
Sorry my memory doesn't serve me (us) any better.

-Tom

 

I was probably over thinking the general concept of providing human power. The use of rum toddies affects some of us in that way.

The rotary pedal mechanism (bicycle gear) causes the user to pivot the ankles during a pedal cycle. Also there is a null point during the rotation when the pedal lever is pointing directly away from the human. OK, that stuff does not seem to bother the cyclists. Ergonomic ruminations; be gone with ya'. As noted, I was over thinking. Now back to the old drawing board.

 

I tried a Hobie drive once for about half an hour and found the fore and aft motion hard to adapt too. I much prefer to pedal in circles. My feet that is!

Glen

 

Plus, you can train up to an increased cadence which bodes well for horse power.

Okay, power, whatever...

-Tom

 

Carbon fiber flex shaft drive train

I took some pictures of my drive train. Because my boat is large (28' with up to 10 people) I need a fair amount of torque when driving the APC 20x15E prop. Refer to my post #1325 and earlier posts for the description. I epoxied the gear head to a mounting bracket. I had the gear head bolted to the bracket into a threaded hole in the gear head's casing but that pulled out on one of our excursions. So I thickened epoxy with aerosil and bonded the gear head to the bracket. On the closeup of the gear head you should be able to see the pullley I use to feed the slightly twisted chain to the 16T sprocket. I made the spinner out of PVC pipe - cementing three different sizes together. A 3/8" stainless steel threaded rod is bonded to the carbon fiber shaft. I use the threaded rod to mount the prop and spinner.

Dave

 

This guy wishes he had some rotary action: http://www.youtube.com/watch?v=chYalZeEu2o

 

well you got me youtubing off on some weird tangent and
it does have peddle power so this isn't too far off course.
What some guys will do for a little bit of freedom!

 

Dave,
Wow, thanks for all the detailed pictures! Did I remember correctly that you had a free wheeling gear? That seems to be rare from what I've seen? Looks like you got yourself a new seat too! I'll be studying these pics for awhile ......

 

freewheel or track cog

I epoxied a threaded freewheel hub to the string trimmer gear head. Then I threaded on a 14T 3/32" track cog. That gave me forward or reverse thrust. To use reverse you need a strut to keep the prop oriented correctly. If you have a free swimming flex shaft drive the prop dives when you go in reverse. The 14T cog resulted in slightly too high a gear ratio for my setup. I unscrewed the track cog and threaded on a 16T single speed freewheel. My freewheel hub will also accept 5 to 8 speed thread on freewheels. On a bicycle multiple gears are a big advantage for going up/down hills or with head/tail winds. On a boat you don't really need the complexity of multiple gears unless your load changes a lot. I attached pictures of a single speed track cog, single speed freewheel and a 6 speed freewheel.

Dave

 

Coach:

Thanks for the details and pics of your very clever drive system!

As regards the folding prop, you should be able to make one from the large 20 X 15E prop. Some RC model chaps have made them for flying purposes if you look around on google. They used channel aluminum on the drive shaft and simply shaped the prop hub into a flattish rectangular box then put pins through where they wanted the prop to fold back, then cut apart. It might be necessary to reinforce the shaped hub box with a nestling channel or box aluminum epoxied to the shaped hub for water applications.... Attach a couple of shaped cone fairings and shave the hinge arms so they don't protrude and you're done. This will give you an idea of how it works, but you would have to shave down the hinge arms to match the fairing cone: http://masterairscrew.com/12x8foldingpropeller.aspx

Hope this helps.

Porta