not every idea is a good idea

[jesusgatos]

I went to a bike swap meet on Saturday and I came home with a BOB trailer that I didn't have any particular need or use for, but I picked it up for $30. I was planning on making a simple rack for it, but then I thought I had a better idea. What if I cannibalized the BOB trailer and mounted an engine on a trailer behind a bike?

It would be really neat to have an engine that you could hook up to a bike without needing to make any real modifications to the bike. The BOB trailer attaches with a quick-release to the back axle, and the only other thing I'd need to do it mount the throttle tube to the handlebars.

I was originally just going to mount a little engine on the BOB trailer, but after talking with my brother about it, we agreed that cutting up a little Honda XR50 was a much better idea (I'm honestly not sure why). Those 50's get about 80mpg though, and they can easily do 40mph. Sounded like a great way to get around town, and I'd be able to ride it on bike paths since it's only 50cc's and would not legally be considered a motor-vehicle.

I looked into this online and found out that people have been making pusher trailers since the 1930's. There's a website dedicated to mopeds (motoredbikes.com) where pusher trailers are frequently discussed and there are even a couple of companies selling pusher trailers. Why hadn't I seen any of these things before? What a great idea.

So Sunday morning I went over to a Pat's house and picked up his XR50 (thanks Pat!). I spent the afternoon disassembling it and thinking about the easiest way to attach it to the front half of the BOB trailer.



I sliced the head tube off the XR50 on Monday afternoon.



Today I cut the BOB trailer apart, sleeved it to make a new head tube and welded it into place. I took the bike and trailer for a pedal before I went down to the bike shop to buy a longer throttle cable. I was already starting to think that maybe this was a bad idea.





I made a new throttle cable using a modified tandem brake cable and length of brake cable housing. Then I partially reassembling the bike (just enough so that it would run), I fired it up and took it for a spin.



YES, this was a bad idea. The XR50 'wags the dog' so severely that it's almost impossible to control the bike if you try go faster than 20-25mph. Testing didn't last very long. I took it off a sweet jump in front of our house. Crashed and burned.





It's really top-heavy and the BOB trailer parts that I used are nowhere sturdy enough to hold up to this type of use. I think the basic idea might work if I mounted the engine (a lot) lower, replaced the BOB trailer parts with heavier-duty components, and added some type of steering damper between the bike and the trailer. Changing the angle of the head tube might make it handle better too, but I'm not sure where to even start.

I think the best thing to do at this point might be to buy a new XR50 frame.

Or maybe it's time to finally build an XR50/mountain bike hybrid....

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[therail]

HAHA, cool. Nice SC, btw.

[jesusgatos]

Yeah, my wife was NOT happy about me using her bike as the test mule.

[fathead]

Sorry Jesse, but your fired.
Please gather up your personel belongings and clean out your desk.
Jennifer in the H.R. Dept will have your check waiting for you.

[chadmcneilfiberglass]

This has allready been done by a guy I know- gary kirkpartick. He even did a charity ride from san diego to canada a few yars ago.

http://dragnfly.org/benefit_ride.htm

[jesusgatos]

I'll be the first to say it: BAD IDEA (implied in the title of this thread). Thought it'd be good for a laugh.

Good luck with the patents. I looked around online over the weekend and people have been building all different types of pusher trailers since the 1930's.

[Thumpcraft]

http://projectm85.com
http://fxbikes.com

Mountain bike small engine type rides

[jesusgatos]

I hadn't seen that Porject 85 website before. That's the kid that originally posted some pics and info on an Aprila forum or something, right? I had a chance to ride an FX bike a couple of years ago. That's probably the direction that I'll head with this, but I've already got a big-wheel CR80 with an XR100 engine in it, and it's almost exactly the same size as a mountain bike but way burlier. I've either got to buy a new frame or build one though, right?

[Moss2]

You truly have too much time on your hands. But if you are going to spend more effort on it is seems like you would want to raise the pivot up higher above the bikes rear wheel and angle it forward. An imaginary line down the pivot would fall somewhere in front of the rear tire contact patch so it has a little caster. Ive seen some trailers that pivot behind the bikes seat tube also. Just some ideas,(not neccessarily good ones) have fun!

[jesusgatos]

I work really hard to make so much free time. Thanks for the constructive input.