Mechanical/Electrical Off-Season Projects

[Tytus Gerrish]

Originally Posted by geeknerd99

Several things, all at once. I have more involvement in some than other:

1 (My pet project): Lead my 4-man (actually 3-man and 1-lady) team in designing and constructing a pair of tandem recumbent bicycles from the ground up.

2: Finish hovercraft prototypes and make 4 people's worth of rideable hovercrafts

3: Redesign and mount air cannons onto aforementioned vehicles.

The tandem bicycle idea is the one that's gonna really get off the ground (hopefully it'll stay on the ground once its built ). I've been studying many designs of both tandem and recumbent bicycles, as well as a few existing designs. Me and my electron-cough-design team are all convinently learning how to TIG weld right now too....

i like your thinking

[KenWittlief]

I mentioned in another thread last year that I was working on ideas for a recumbent bike, and I would post my plans when I got around to building one.

Well its taken almost a year, but I finally did get around to it. I dont have specific plans drawn up because the way I put the bike together it more of less depends on the existing bike frames that you start with, and how tall you are to figure out where to put the pedals, seat back... So I have not drawn up detailed plans

but I think the description and photos is enough of a starting point that anyone with a bunch of bike parts laying around and access to a flux wire welder could do something similar.

So here is the link: http://members.aol.com/wittlief/HMLAT/HMLAT.htm

[geeknerd99]

That is freakin' beautiful.

We're planning on using aluminum tubing and building it from the ground up. Right now, we're still in the CAD phase of the design though. And by CAD, I mean "Crap, Another Dud" phase.

The problem with a recumbent tandem is that it'll practically have the wheelbase of an 18-wheeler. Theres a few out there, but they all seem to cost in the 4000 range, and some cheat and have 3 wheels!

Also, since we wanna do this right, and in one shot (expensive, and hopefully only once), we're taking our grand ol' time. Besides, we don't have much else to do before build season anyways.

Alternatively, it looks like the budget for the bike's aluminum tubing might be deferred over to aluminum tubing for a hovercraft and 3-5 shopvacs instead. We'll see. Either one will carry 2 people. The hovercraft is still in sketch phase right now.

[KenWittlief]

I've been doing a little web research on bicycle frames and I now think that alum may not be the best choice for a bike that will see a lot of use and mileage. From what I have read, steel tubing has a threshold of stress (bending and twisting), below which you can literally stress it repeatedly forever and it will bend back (spring-like) and will never fail. Aluminum is not like that. Even a small bit of stress on an alum frame causes stress fatigue, and eventually it will simply break - and break completely with out warning.

Im not sure how correct that assesment is, because the mast and frame on my Hobiecat are aluminum, and the boat is 23 years old, and the mast bends noticably (intentionally) when you sail it. Maybe it will snap in half someday.

But I do know from working on FIRST robots that if you bend aluminum enough to deform it, you usually can only bend it back once, and the next time it bends it will fail. So Im thinking maybe chrome-moly steel tubing would be best for a custom recumbent frame. I would hate to put a lot of time and money into a custom frame and have something as simple as the wind blowing it off the kickstand causing possibly catastrophic damage.

It has also occurred to me there is another easy way to make a long frame recumbent bike frame. I made the one I have now, the way I did, because I wasnt sure where the pedals and seat would end up, but now I could build something similar by extending a standard diamond frame by about two feet. If you cut the top tube and extend it with a straight steel tube, and miter cut the tube from the pedals to the fork head, and extend it to match the new angle, you would have a frame with the same dimensions of the bike I have now. All you need to do then is weld the pedal cluster up in the new location, and add the underseat handlebars, and seatback.

I photoshopped this to see what it will look like. Check in the HMLAT directory on my aol ftp site for bridgestone.jpg and bridgestoneA.jpg to get an idea of what Im talking about. If I were to build a second bike like the one I have now, I think that is the way I would go (if I didnt build a whole frame from scratch).

One thing I have not found a good solution for: making a long frame recumbent adjustable for differnet size people. If you move the seat forward and back you need to move the understeat steering too. The other option would be to make the pedal cluster position adjustable, but then you need to take up the chain slack somehow. I dont have a solution in mind for either approach. So far my bike plans led you to a bike specifically designed for one person. Anyone else who is not the same height would have a difficult time riding it.

[eshteyn]

Building a drive system for our cart, put a chair on it for the driver and thinking of making a trailer for personnel transport