| Converting a BMX bike to a Recumbent bike | ||||||||||||||||||||||||||
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Or - Building the "JunkBike" |
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| By Warren Beauchamp | ||||||||||||||||||||||||||
| I had been thinking about building a bike that I can use without worrying about
"things happening" to it for some time now. Typically recumbents are quite
expensive, and the mono-tube designs do not lend themselves to being locked up. I had read
bits and pieces on the IHPVA mail list about people building 'bents from BMX bikes, and
this past summer spotted a beaten looking BMX bike in the one of the neighbors garbage. I
also received a '70's vintage 10 speed from a friend at work. Together these bikes (and an
assortment of other parts from previously donated or garbage-picked bikes) will become
(before your very eyes) the JunkBike! The criteria to building the bike, is, well, to uh,
not spend any money. 6/98 - I stripped the parts off the BMX bike, and hacked the crank and assorted tubes from the 10 speed. Hmm. Heavy bike + heavy bike = heavy bike. OK, so it will be a training bike. It sits in wait for building season (winter). 12/98 - I removed the junk hubs from the el-cheapo steel rims, and rebuilt the wheels using an aluminum front hub, and a 5 speed rear hub from an old 10-speed. I had to spread the forks out a little to get the new hubs to fit. Miraculously, I was able to re-use the BMX spokes.
After measuring my X-seam (the distance from the seat back to the bottom of my foot, I was able to size the boom tube. The nice thing about re-using the frame tubes and crank from an old 10-speed is that the front derailure tube is already there. I also cut and mitered (with a file) another tube to use as a brace.
1/98 - I took a trip to Bill Murphy's to braise on the tubing. Remember to take the paint off at least 5" from the welds. I didn't, and stunk up Bill's basement pretty well. Here's the bike with the tubing braised on, and a rear derailure. Hey! It's beginning to look like a recumbent!
I decided to use some junk BMX side pull brakes, and reject mountain bike brake levers. Perfectly serviceable! I dug out some old Suntour derailures from the junk box, as well as a Suntour friction shifter. The heavy steel cottered crank came from the bright orange donor 10-speed. I originally was going to use the old knobby BMX tires, but then decided as I already had a pair of Primo Comet 406 tires languishing around the house, I may as well use them. I'm using the plywood seat that I originally built for the Barracuda racing bike. Because of the relatively high bottom bracket, I was able to get away with no idlers on the power side, and only 1 idler on the non-power side. I cut the idler down from a skate wheel. Here's the bike after I added all that stuff to it.
As shown in the picture above, the back of the seat is supported by telescoping aluminum tubing. The 3/8" OD solid aluminum rod fits nicely inside the 1/2" OD aluminum tube available from Home Depot. Below are some shots showing the welds and the hand made idler wheel.
I hacked off the top of the BMX handlebar mount, and was able to use a chrome-moly tube from a previous project as the new handlebar "up-tube". Below is a shot of the head tube stub, which I will clamp the handlebar up-tube to.
2/99 After adding handlebars, brake and derailleur cables and tweaking the chain line, It was time to ride it. And the verdict is.... It's actually a well behaved and altogether pleasant bike to ride. It handles well, accelerates well, and is as comfortable as plywood with a layer of foam on top can be. Due to the retro-grungy shifters, it shifts well too. It weighs a lot less than I thought it would as well, coming in at 36lbs. Is it fast? I don't know yet...
I know... You're thinking, hey! It needs paint! I'm still considering that. I think I've got part of a can of silver spray paint lurking somewhere... Here are the costs for building this bike:
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