Handbike and 20 inch wheels?

Discussion in 'Introduce Yourself' started by handbiker, May 18, 2008.

  1. handbiker

    handbiker New Member

    Hello, first post newbie here from the UK.

    I've literally only just found out about motored bikes and am pretty excited about the possibilities.

    I use a handbike (I'm in a wheelchair following a climbing accident a couple years ago) which is a pretty unique three wheeled number with 20 inch wheels.

    I just wondered if 20 inches is too small for a motor, I have disc brakes so am assuming that the chain/sprocket type engine wouldn't be possible and I'd have to go with the belt drive option. But dont think the wheel would be big enough.

    Also not entirely related to motored bikes, but relevant to the engines, I paraglide by sitting in a small buggy and getting someone to throw me off a mountain, which is way more fun than it sounds. While I'm in the air and flying it's great, but on the ground I am completely reliant on someone either pushing the buggy for me, or bringing over my wheelchair for me. I want to fit a small motor to the buggy to allow me to get around independently at the landing sites. Would a 40cc engine have enough torque to do this by itself.

    Thanks for any help.

    Last edited by a moderator: May 18, 2008

  2. Easiest way to go would be a friction drive. I believe on those the size of the wheel does not matter. If you go chain or belt you can always gear tall to compensate for the 20 inch wheel. Rack mount is a definite must.
    WELCOME to MBc! Please post progress. This would be interesting indeed.
    Looks like throttle can go right there with your brake lever.
    Where you at?
    Last edited by a moderator: May 18, 2008
  3. SimpleSimon

    SimpleSimon Active Member

    An interesting problem. I will assume a few things - 1) you need good torque to climb slopes over uneven ground; 2) either you, or a friend, is competent to do a little basic mechanicing (never met an outdoorsy type who wasn't); 3) you want a reasonable range.

    So, a gas whizzer type engine setup is your best option. Attached hereto is a quick and dirty sketch of a suggestion - use a whizzer engine mounted on a rack begind you driving a jackshaft, with the small pulley from that driving the spoke mounted whizzer drive ring. I don't know the diameter of the typical spoke mounted whizzer driven belt pulley , but I suspect it is larger than can be fitted to a 20 inch wheel. Get somebody to fab up a smaller ring, sized so it can function as a driven pulley, then fit a drive belt, and away you go. Obviously, select your various pulley sizes as appropriate to arrive at a reasonable compromise of speed/torque.

    (Many details omitted for clarity and speed)

    Attached Files:

  4. datz510

    datz510 Member

    For the para gliding application, torque is going to be a function of gearing. If you don't need to move the buggy fast (like 5mph or 10mph max), you can gear it down and move a mountain with the thing! With a lightweight engine, it should work nicely for what you want to do!

    Welcome to MBc! Look forward to seeing your motored builds!
  5. graucho

    graucho Active Member

    Hi Andy. Welcome to MBc!
    Cool bike. I know you would cruise with a 40cc engine.

    If you search and are unable to find your answers, don't hesitate to post your question. Someone will steer you to a link, or reply to your question. Were here for each other! Enjoy! :grin:
    Here's a great crash course post "link" to get you started.
    Last edited: May 19, 2008
  6. handbiker

    handbiker New Member

    Thanks for the help and guidance. I'll be sure to have a look through the noob guide, which is just what I need as I have no idea about engines at all.

    Ideally I'd love to have some kind of recumbent motored handcycle that I could use to fly the paraglider and tour with on the ground but I think that is aiming too high for now.

    Hopefully I will figure something out for my current handbike though.

    Regarding the paragliding buggy, I'm thinking of getting a kite buggy similar to the ones in this gallery and trying to fix a small motor to it so that I can possibly launch independently and get around upon landing.

    Weight is a huge factor and trying to keep it to a minimum is the biggest problem. I had been looking at 5hp engines but there are too heavy so these smaller engines look great.

    Is it feasible to adapt an 'off the shelf' motored bike set up, probably a 40cc onto one of these buggies as the sole means of propulsion and have it move me around, slow speed isnt a problem at all.
  7. datz510

    datz510 Member

    It depends what kinda speed you need for launch whether you could use it to launch with. On the ground, definitely not a problem. These little engines have the power to push a 70-90lb bicycle with 200lb rider along at 30-40mph easily. That buggy looks to be extremely light in comparison.

    Looking at the buggy photos, its absolutely possible to motorize one of those. You may need to cut the rear axle housing and fit a chain drive sprocket somewhre in the middle to drive one or both rear wheels. This could put the engine right behind your seat which is gonna be necessary for balance.

    As far as weight is concerned, the cheap chinese 2 stroke kit weighs around 20-23lb for everything. a half gallon of gas is 4 more pounds, but my guess is that you wont need a half gallon to do what you need to do on the ground.

    I'd look into adapting a rack mount drivetrain to the buggy. That will give you the compactness that you need. An HT 2 stroke engine could work, but they can be a bear to start. I would do a remote pull start for whatever engine you install so you can start it without having to contort too much.
    Last edited: May 19, 2008
  8. ZMX

    ZMX New Member

    Wow, I applaud your tenacity at not letting your injury keep you down.

    Anyway, for the first question, small wheels won't affect your ability to stay mobile.

    I'm going to recommend a four-stroke engine for these reasons:

    1. No mixing of gas. It's a pain in the *** to carry two fuel types, and if you run out on a trail, it's just another thing to worry about in a difficult environment.

    2. More engine reliability. Less chance of failure means your method of transportation won't be compromised (once again especially if it's in a forest).

    3. Better powerband. If you're wanting to go up a lot of hills, you'll need lots of torque no matter how fast the engine is spinning, and four-strokes have the advantage here.

    I'd also recommend a chain drive for the best reliability under torque. Belt and friction drives can slip - especially when wet.
  9. BoltsMissing

    BoltsMissing Active Member

    Welcome to MBc

    Interesting project, hope it works out for you.

    All the Best