Building a BMX - Recumbent conversion bike
Converting a BMX bike to a Recumbent bike

Or - Building the "JunkBike"

By Warren Beauchamp
This was one of my first bike projects, from 1998. I had been thinking about building a bike that I can use without worrying about "things happening" to it for some time now. Typically recumbent bicycles 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.

6/1998 - 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).

12/1998 - 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.

 

junkbike1.jpg (6011 bytes)
junkbike2.jpg (5720 bytes) 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.
1/1999 - 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 derailleur. Hey! It's beginning to look like a recumbent! junkbike3.jpg (7185 bytes)
junkbike4.jpg (7387 bytes) 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.  Here are some shots showing the welds and the hand made idler wheel. junkbike5.jpg (10608 bytes)
junkbike6.jpg (7284 bytes) 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.

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...

 

junkbike7.jpg (7406 bytes)


Here are the costs for building this bike:

Item

Costs

'China" BMX donor bike $0
"Atala" Donor 10 speed bike $0
Wheels, hubs, spokes $0
Derailleur's, brakes, shifters $0
Seat About $10 - reused from previous project
Tires, Tubes About $40 - reused from previous project
Handlebars About $3 worth of tubing - from previous project
Chain 3 chains, $24 .
Idler About $2.50 - Made from skate wheel
Rear seat stays $8 worth of aluminum tubing
Welding costs About $5 for gas, rods, chunks of metal.
TOTAL well under $100...

CODA: This was a fun and relatively easy bike building project. I did not end up riding it much , so I sold it to Gary Toy.

 

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