PRIMITIVE ENGINEERING - Sport Utility Bike

So here we have it. Just put the two chains together to compensate for the additional distance.

Click for a larger Image.

My old derailleur no longer bolts up to the new fork - so now this is a two speed (front derailleur). I'm going to try the mountain bike derailleur later, but I found a nice gear ratio I like. The chain is a little finicky - a little tuning and debugging will fix that (propping on the derailleur as shown helped a lot - tensioner to come). As of right now, I only have use of my front brakes - not the safest, but now I'm not worries of falling over my handlebars from hitting my fronts too hard. All and all, I'm happy with how it came out. I preserved my rake angle, so steering is the same other than requiring a little wider turns if you don't want your rear wheel to roll over something.

I look forward to making racks, carring people and hopefully adding some suspension. Oh, and don't give me any crap about the seat ;)

PRIMITIVE ENGINEERING - Sport Utility Bike
Proof of Concept
October 6, 2006
I first started this by bending bits of metal hangars to see what kind of tube bends I'll need. Then I asked myself - how can I make this easier. Lucky for me, my other bikes were sitting nearby. The goal for this build is to extend the wheelbase of of my road bike and create a space to haul cargo, people and whatever else without the use of a trailer. Last year, I won an auction on a mountain bike for $3. It was missing a wheel and seat and its rear wheel bearing was shot. I improvised for awhile with it, but it was not a very enjoyable bike. By contrast, my road bike has been well worth the $35 purchase price at a garage sale about five years ago. It could use a tune-up, seat and a few other things, but it has served me well despite that it was kept outside for two years (college).
The first thing done was a test fit. Will my road bike wheel fit the rear triangle of the mountain bike and will the axle match the dropout distance. Lucky me, it fits perfectly and with a little modification, I can use the brake bosses. Once the fit was tested, disassembly began. The derailleur, brakes, shock/damper, crank/pedals, and pivot axis were removed/unbolted. The yellow rear triangle came off without problem. To make things even easier, I found that the crank axle fits on the dropouts of my road bike! The fit is a little tight - only a few threads grabbed on, but that's enough for me at the moment.	Test Fit The project is going way too smooth.
Now the tough part. In order to make this work, we need to prevent that crank axle from spinning (other than any suspension motion). A bar will be placed from where the old suspension coil/damper attached to the bracket that the kickstand bolts onto.
I wanted to find a clevis joint so that I could use that coil/damper. But no such luck at the local home improvement stores OR a Harley Davidson dealer. Solution? 1/2 steel "weld pipe" from Lowes. I also picked up a 3" grade 5 bolt to replace the original bolt holding the kickstand on (the same bolt that will be used as an attachment point for the new member). I drilled two holes in the pipe using my $15 harbor freight drill and a wood drill bit that was too small (where the hell did my bits go? I say). I may have ruined that bit, but I was eager to get moving on this. One set of holes are for the triangle mount and the other is on an angle to mount to the kickstand bolt. This member will be under compression and is going to put a lot of shear on that bolt (reasoning for grade 5 quality).
So here we have it. Just put the two chains together to compensate for the additional distance. Click for a larger Image. My old derailleur no longer bolts up to the new fork - so now this is a two speed (front derailleur). I'm going to try the mountain bike derailleur later, but I found a nice gear ratio I like. The chain is a little finicky - a little tuning and debugging will fix that (propping on the derailleur as shown helped a lot - tensioner to come). As of right now, I only have use of my front brakes - not the safest, but now I'm not worries of falling over my handlebars from hitting my fronts too hard. All and all, I'm happy with how it came out. I preserved my rake angle, so steering is the same other than requiring a little wider turns if you don't want your rear wheel to roll over something. I look forward to making racks, carring people and hopefully adding some suspension. Oh, and don't give me any crap about the seat ;)

Total Cost of New Parts: ~10 \|\| Time: ~1.5hr \|\| Primitive Engineering \|\| Talk about this project!