Floating ebike

I saw http://endless-sphere.com/forums/viewtopic.php?f=39&t=48016 this thread. Some guy advertising his kickstarter thing.

It reminded me of a few things I had seen in the past. One of them is called a shuttle-bike. Convert a bicycle into a paddle raft. It's pretty freakin awesome in my mind, it honestly stands only a step or two below the ebike concept, at least in potential usefulness (earth is more water than land). The rear wheel spins the propeller with a little contraption.

http://www.gizmag.com/go/2505/

I also saw a sort of very cheap version of this shuttle-bike. http://www.gizchina.com/2010/04/02/480-yuan-refundable-bike-boat-conversion/

The bridge is out? Meh. I'll just cruise across the water with my ebike powered raft. MRRRRRRRRRRROOOOOOWWWWWWWWWWWW Now alls I need is a cover for that propeller.

The only thing I like more about the cheap 5 gallon water jug option thing is that it would be substantially harder to sink, take on water or spring a leak in one of those plastic water jugs compared to the thin plastic of the shuttle bike. There is an obvious weight tradeoff, but those the brakes.

Wow, this actually inspires a serious use for the reverse feature I sometimes see on some ebikes. No brakes on the water, but if you could move the propeller in reverse, which you could with an ebike reverse, that'd do. Win!

I live very near a lake and have been scheming about a pedal boat for some time.

I have assumed that a normal upright bike with a rider on it is too top-heavy to make a good basis for a personal boat. The pontoons or hull(s) would have to be so big and widely spaced as to be intractable.

Paddle wheels based on bike wheels are inefficient. The only advantage there is that we already have bike wheels and understand how to implement them. Having looked at paddle wheels, small waterjets, and air props, I decided a water prop was the way to go. Maybe even a large scale RC airplane prop used as a water prop. Shaft drive bicycles offer a reasonable existing solution for how a set of pedals might be used to drive a prop.



I've been thinking along the lines of something that is trailerable by a bicycle, which ideally could carry the bike aboard. Perhaps wheels on the upper side of the boat would work as road wheels when the boat is turned upside-down. Likewise the trailer tongue could be permanently fixed in place, as long as it's above the water when the boat is afloat.

Recumbent rider position makes sense for a boat to a degree it never does for a bike. It permits good weight distribution and stability in a hull of minimum overall size. Less hull in the water means more speed for the same power, all else equal. And boats do almost as well with the modest power that recumbent position promotes as they do with the greater power that upright position enables, because their drag increases so dramatically with speed.

For minimum complexity and maximum utility, I'm guessing a twin hull would work best . The platform suspended in between the pontoons provides a fair amount of space for rider, bike, and gear, and within its weight limits a twin hull is the most stable layout available. So I have been on the lookout for pontoons, canoes, or even plastic barrels that are available to me and cheap enough to experiment with.

Electric propulsion would change many of my assumptions in this project. It offers an opportunity to simplify and maybe even reduce the cost of the machines, if you don't require the boat to be pedal powered. Because if the boat is only e-powered, it could be built to use the same battery as the e-bike (swap the battery over or just plug into the bike), and that lifts all the constraints on boat construction that arise from accommodating pedal drive. It could be a little flat-bottomed jon boat with a modified trolling motor and a set of mounts for the bike, for instance. Simple and easy. Or you could optimize for efficiency, use a racing shell with an outrigger, and yield more range and speed for the same battery energy than if you were helping with the pedals on a draggier boat.

Part of what is the appeal of ebikes is, you are pretty close to impossible to become stranded. If you were to do away with the option of pedaling to create propulsion on a raft, unless you had some good paddels, you'd have a serious problem on hand when/if you ran out of battery power. I think you may want to look into the shuttle bike a little more deeply. A critical detail you likely missed was that it converts the spinning of the wheel into the spinning of a water propeller. https://www.youtube.com/watch?v=eZiJMilYMG0

As far as assuming the upright wouldn't be satisfactory, your assumption is incorrect. It would really depend on the design of course. But both of the examples of this floating ebike concept I have shown use uprights and they didn't seem to end up in the water. Of course, I am sure it's possible, and you are right about the lower center of gravity, but if you make the source of floatation a bit wider, tipping would likely never be an issue.

Chalo said:

For minimum complexity and maximum utility, I'm guessing a twin hull would work best . The platform suspended in between the pontoons provides a fair amount of space for rider, bike, and gear, and within its weight limits a twin hull is the most stable layout available. So I have been on the lookout for pontoons, canoes, or even plastic barrels that are available to me and cheap enough to experiment with.

Click to expand...

It honestly sounds like you describing exactly what has been shown in the two bicycle boat concepts I provided links to.

bowlofsalad said:

As far as assuming the upright wouldn't be satisfactory, your assumption is incorrect.
...., but if you make the source of floatation a bit wider, tipping would likely never be an issue..

Click to expand...

..and for similar reasons, you would also need to make the floats longer in order to control the "pitch" ( fore -aft) stability.

Watch https://www.youtube.com/watch?v=eZiJMilYMG0

I've always wanted to build me one of these when I grow up...
http://www.recumbent-gallery.eu/amphibian-velomobile-from-czech-republic/

Hillhater said:

bowlofsalad said:

As far as assuming the upright wouldn't be satisfactory, your assumption is incorrect.
...., but if you make the source of floatation a bit wider, tipping would likely never be an issue..

Click to expand...

..and for similar reasons, you would also need to make the floats longer in order to control the "pitch" ( fore -aft) stability.

Click to expand...

It has been done with some degree of success, but the bike-boats I have seen made that way were longer than I'd want to trailer from a bike, and too wide to ride on top of a car in their assembled state.

Lower the rider, and the extents of the hull can become much smaller, even at the same displacement.

The SBK Shuttle-bike might work for a very short. lightweight person. But just looking at it you can see it has a weight distribution issue. It's a very lightweight boat without a ballasted keel and with the preponderance of the weight centered several feet off the water. Even if it does not tend to tip when standing still, it will want to tip in a turn.

The Chinese jug bike I expect is just as ridable as that girl's face suggests.

Here's a video I found of a guy who built an amphibious 'bent. Look how much more compact, but still plenty stable, this layout is compared to a person sitting on top of a regular bike sitting on top of a raft:

[youtube]79K_pP36fjU[/youtube]

That really isn't a whole lot different than the other designs I showed, except his design is crap. Some of his bicycle is completely submerged. Chain, wheels, and all kinds of vital components on a bicycle shouldn't be fully submerged in water unless you don't care about silly things like rust and broken things.

I still don't think you get this, but one of those designs (shuttle bike) uses the tire to spin a wheel which then spins the propeller that is in the water. You can put a recumbent on any of these designs, the recumbent part isn't special.

There is a phrase that applies very well here, the jack of all trades is master of none. I would much rather have a recumbent with the shuttle bike converter in a pannier than his boat/bike. I Applaud this mans desire to engineer, but I dislike his design.

I don't know the weight limit of the shuttle bike, but I have trouble agreeing with your perspective on it in general. It seemed plenty fine to me for both weight and balance. I don't know what sort of weight you have in mind, but it seems likely it would need to be pretty intense to totally sink that thing. I also think it would be pretty hard to tip. They don't have the yellow inflated balloon parts very close to the bike from my perspective. After a little searching, I found "The Shuttle-Bike can safely carry a load of 275 pounds; in rescue conditions, even someone weighing nearly 450 pounds could be transported to safety."

I would much rather have a raft that you place the bicycle upon than that specialized bicycle contraption he has going on.

Personally, and I think for many ebike setups, that weight limit would be satisfactory. But I am sure for some it might be too little. To be honest, not all bikes can sustain a weight of much more than that shuttle bike can.

I just love the idea of carrying something that weighs a couple of pounds with you so you could ferry yourself across a body of water.

My point was not about any of the qualities of the 'bent boat except its size and apparent stability. It's tiny compared to any of the upright-bike-on-top watercraft I have ever seen, and less tippy. All else equal, lower center of mass is better on water.

That probably precludes breaking it all down into one little bag and riding away on a normal bike, though. A normal bike only gets so low, even if parts of it touch the water like that Chinese jug bike. So if collapsibility and employing a normal bike are the measures of success, the Shuttle-Bike is the most successful aquatic bike I have seen yet.