My latest project is a short wheel base (SWB) recumbent bike. This bike is actually being built for someone, and most of the the work has been done, but now I need to work on the seat. Once that is done, I can hook up the cables so that the brakes and shifters work. I haven't yet come up with a name for this bike, so for now I'll just call it the Recumbent Mk I.
Here is what I started with. I took a 24 inch women's frame that seemed to be functioning. The main thing is that the tires were usable. The black frame in the front was needed for the bottom bracket. I ended up chucking the crankset as it was not compatible with the chain that I would be using. I took off yet another part from my chopper. At this point, the chopper is probably destined for the recycling center.
I chopped off the lower tube on the BMX bike that I got. I figured I could just weld the tube with bottom bracket intact to the head tube of the donor bike. It worked out pretty well.. I'm grinding the welds from the bottom bracket. in this photo.
I carved out a "fish mouth" in the black frame, but found it was wider than the head tube. So I welded the top and bottom of the tube to the head tube, then I hammered the sides to the head tube. Once they touched, I welded the rest of the joint. I then ground down all the welds a bit so that it looks pretty smooth in the area. Later I'd mess up what was otherwise a beautiful joint. I welded a pulley to route the chain in the wrong place so I ripped it off. Along came a piece of the black frame right around the joint.
The frame is taking shape. I put the parts back on the frame, and began to work on the chain run. I was about half a chain too short, so I headed off to get some more chain from the bike co-op. I also got two pulleys and a peice of wood for the seat. The pulleys rotate on bolts that I welded to the frame. I welded the head of each bolt to the frame, and then slipped a pulley over each. I was planning to weld a nut to each bolt to finish it off, but I think I'll get a nylock nut instead so that I can remove the pulleys should the need arise. I screwed a peice of wood a couple of conduit straps, then sawed off the ends of the screws. I carefully began to put my weight on the "seat." It broke in two. I thought the wood was kinda iffy. I looked around to see what else I could come up with.
I grabbed some conduit and made seat. I figured I could cover it later, but for now, I could ride the bike. I found my knees hit the handle bars, so I welded an extension to the old bars. Thats the long black bar coming out of the head tube. I figured I'd ride the bike around the block, so I just wrapped the cables around the handle bar. I soon found the seat too wide and long. Its also leaned to far back. The final problem was that the bike had no rear shifter, so it was locked in high gear. It made starting very challenging. Once I got going though, I found that the old seat tube was poking me in the back. I'll relocate the seat first, then maybe I'll chop the post down to size. The rats nest of cables was in my sight line, which was kinda wierd. I may end up lowering the handle bars, but I'll wait and see what the recipient of this bike wants.
Here my friend Ben rides the recumbent past me. I ended up sawing off the old seat. I went down to a bike shop and grabbed a really wide bike seat. I tried to weld the post mount to the frame, so that the seat could be tilted front and back. I was in a hurry though, and threw snow onto the weld to cool it down so that I could sit on it. I don't think I let the weld cool enough though, as the metal still seemed soft. Or maybe something that is designed to clamp around a round tube can be welded to a bike frame. I ended up welding the seat directly to the frame. The seat is not moveable now, but it seems to be at a good angle.
I then made a seat back out of conduit, and welded that to the bike. On the first ride, I decided to head to Ace to pick up some lock nuts for the idler pulleys. I also changed the handle bar angle a bit as they were hitting my knees. The bike is clearly not for someone my size. I began to get used to the responsive steering, and since I had hooked up the gears, it was much easier to ride. I so far have tested 10 of the possible 15 speeds. I haven't tried the smallest chain ring and don't recommend it. The chain runs over the steel pulleys, and makes quite a bit of noise. I could probably have made quieter pulleys out of roller blade wheels, but I wasn't about to ride all over town looking for an open thrift store on Sunday evening. The seat back really needed something, as the frame was really uncomfortable. I ended up find a large thin peice of wood. It makes things so much better. I also moved the seat a bit.
I slipped the chain onto the largest ring and Ben took it for a spin, hoping to catch up with a couple of riders. I'm not sure if he did, but when he popped back into site, he was keeping up with a seriuos looking cyclist who didn't seem to appreciate this odd bike grinding along beside him. Ben kept up with him for quite a ways, and I'd say both were going 15-20. I didn't get a photo, but it was pretty funny. As for handling, it is extremely responsive. I could get it to turn a circle in less space then a bike trail. Ben was executing U-turns like a pro in no time. He remarked it was like a biplane. I'm not sure what exactly he meant, but he was having a blast. I'm sure if it was properly sized, he would have not returned it. I tried a no handed run, but I don't think its possible. The slightest amount of lean puts it in a turn. The handle bars are used to keep the thing upright more than a normal bike, which can be ridden hands free. However, I find that the steering is really light. In the future, I'd like to try under seat steering, but I'm not sure how well this bike would work like that. It would also add quite a bit to the cost to buy the needed hardware. I still need to dress a few welds, and add some paint to the welds to keep them from rusting.