Introduction: Recumbent Bike
Front wheel drive, rear suspension lowracer...
Recumbents offer less drag, and the rider's position makes use of powerful leg and back muscles.
I chose the front wheel drive arrangement to minimise the chain length, and to see how it would work.
I had concerns that the bike would not steer, but there is plenty of flexibility in the chain, and at anything above a very low speed (where you usea large steering angle) there was no problem.
Step 1: Find an Old Bike, Get All the Useful Bits Off It.
All the parts other than the main frame (the silver bit) are taken from scrap bikes. I used a front fork and steering tube from a kid's bike (make sure the kid is not looking).
I cut the steering tube off the frame with an angle grinder, and cleaned it up so it was just a tube. This will be welded into the new frame.
The rear forks are from a Saracen AWOL. They have a little bit of suspension which is useful on a recumbent since you can't use your legs to absorb bumps like you do on an ordinary upright bike.
Again these were cut from the original frame with an angle grinder, ready to be welded into the new frame.
Brakes, derailleur, pedals etc were also scrounged. Bottom bracket was also cut from an old frame ready to weld to the new one.
Step 2: Scratch Your Head Lots, Work Out a Good Shape, Weld Up Some Steel.
To decide the shape for the frame I drew out a profile of me sitting in a position that felt comfortable, and then added the frame around that.
My aim was to make a rideable bike that was as low as possible (to minimise drag and look cool) but you can make you'r to suit your preferred riding position.
The frame is made of square section mild steel tubing, cut to the right angles with a hacksaw and welded back together. I used a cheap arc welder, but if you have access to a MIG welder that will give better results..
Cut a hole for the steering tube, the bottom bracket (now a 'front bracket') to hold the pedals and for the tube that supports the rear suspension pivot, and weld these in place.
For good steering the steering tube needs to be at the right angle, but will tolerate some small errors in position.
Holes were cut through the frame at the idler pulley positions, and bolts were welded through these holes, leaving the thread extending out, ready to mount the pulleys onto.
Step 3: Making the Seat
The seat is made of several laminations of thin plywood, glued together using a frame and as much pressure as possible. Epoxy would have been good for this because it is gap filling and needs less pressure, but it is expensive.
The seat is bolted to two brackets that are welded to the bike frame.
The shape for the contours of the seat was a best guess, and is very comfortable. Some thin padding may be useful... Perhaps a camping mattress.
Step 4: Try It Out.
Go try it out!!
Step 5: Fall Off Because It's Damn Hard to Ride!
Getting started on this bike takes some practise, and you need to get oe pedal in a vertical position and give it a good push to immediately get some speed up.
Starting uphill is very hard.
Once you get some speed it's easy to balance, just like on a conventional bike.
Step 6: When You Get That Hang of It It's Fast and Fun.
My bike is a little low geared because of the small front wheel, and is very heavy because of the mild steel tubing (carbon fibre anyone?).
At one point I was cycling ten miles or so to work, and the recumbent was as fast as a conventional bike overall. With higher gearing I think it would go faster on the straight bits and downhill, and would be faster overall.
Going uphill is painfull though, although practise does build up the right muscles.