amphibious bike

[sareena1204]

Dear Expert,
What is the feasability of building an amphibious bike? I googled it already, and didn't get very many responses that I really liked. I want to build it so it can be used for emergency flood situations to escape to higher grounds.

I've been talking to others (mostly adults) and trying to see what they think. So far, I've been kind of demotivated to continue brainstorming about this idea. I would love some feedback. Thanks!
Sareena

[EDS]

Hi Sareena,

What's an amphibious bike?

I could imagine a couple different versions: a bike that's meant to be driven along the ground through waist high water, or a bike that somehow floats on water, or a bike that attaches itself to a small boat and drives a propeller.

What did you have in mind?

best,
Erik

[sareena1204]

I got the idea from the Bombay floods that recently happened, and thought of building a bike that can ride on water and on land as means of escaping to higher land.

I was more thinking of a bike that floats on water that moves because of a propellar. I'm really confused. I like the idea, I just don't know where to go with it.

Also, what subjects should I look into for my research? As I said before, I've googled amphibious bike and didn't come up with something along my idea. It was more for beachtime activities is what I saw. I want to make something that can be manufactured cheap and be sold to flood-prone areas.

Thanks alot,
Sareena

[EDS]

Hello,

It's not clear to me exactly what your project involves. Are you just designing the bicycle on paper? Are you actually going to build one? If so, would a scale model work? Also, what sort of tools do you have at your disposal, and how much time and money are you willing to spend on this? Building a working full size model is a pretty serious undertaking, even for someone with plenty of tools and shop experience. (But that isn't to say you shouldn't try it.)

Depending on what your teacher expects, I suspect the research for this project would largely involve something other than looking at other people's versions of amphibious bikes, although you should certainly do that too.

On the economics side of things, you may want to consider what you would need in order to make your bike commercially accessible to your proposed customers. How much can they spend on a bike? What requirements must a bike satisfy in order to be useful? For example, if they peddle for tens of kilometers every day to work, then adding a bunch of extra weight to the bike could be a real problem. If they mostly use their bikes to pull trailers a few hundred meters to the center of town, that may not be an issue. How many bikes are there per family today?

In the end, you'll probably want to show that your bike is a better solution than the alternatives. For example, keeping everyone's existing bikes and mass producing a cheap aluminum motorboat and some inflatable rafts for every village, or building a big elevated concrete island in every town center.

On the engineering side of things, you'll want to know something about how boats work. How much volume will you have to displace in order to keep a person safely afloat? If you assume something about the shape of the boat and the type of propeller, how fast could someone travel through the water peddling at a reasonable bicycle speed? (Is it fast enough to beat the speed of floodwaters?) How much extra weight will the bike need to carry around when it's an ordinary bicycle?

One problem you'll almost certainly face is that a bicycle rider on land has a very high center of mass. (Most of the weight of the person+vehicle is high off the ground, making it easy to tip over.) When you're riding, it's easy to keep yourself balanced so that you don't tip over. But as a boat, you'll need to find some way to make the bike sit very low in the water and or give it a wide base. Starting with something like a recumbent bike might be easier.


Keep in mind that there's a long history of designs for amphibious vehicles that turned out not to be practical. Most of them end up being more expensive and less able than a pair of separate land and water vehicles. Outside of military and a hand full of hovercraft ferries, there aren't very many amphibious vehicles in use today except for recreational toys. The compromises one has to make in order to build vehicle "good enough" on both land and sea usually means it performs far less well than a dedicated vehicle would in either environment.

But that isn't to say that it's a bad project idea. You might be able to come up with something really useful. And even if not, it still could be worthwhile as a fun and educational project. One thing to consider is whether, "there's no feasible way to make an economically viable amphibious bike" is an okay conclusion for your project, since there's a chance that's what you'll discover. (If you ask me, showing in detail that a product idea won't work is just as important as coming up with one that will. But, your teacher may not agree with that.)

best,
Erik

[sareena1204]

EDS,
I do want to actually build a prototype once I've gotten all my dimensions down. Right now I'm just brainstorming different projects and happened to like this one in particular. I would be able to access tools if this happens to be the one I settle on.

Encompassing everything to consider, I don't know if I'm still very enthusiastic about this project anymore. I'll have to see when I sit down to do more brainstorming.

Thank you so much for your help! It's really going to help me in what I want to do!
Sincerely,
Sareena