My family was at a recent family reunion. While there, one of the cousins had a an interesting looking contraption. It was a swingbike?!!?!? A bike that had two pivot joints in it. I tried riding it while I was there, but didn't have much luck, as the terrain was rather hilly, and somewhat hard to learn on. He told me that it was something that had been around for quite some time, and the design wasn't necessarily anything new, just fun.
Upon arriving back home, I decided to do a little bit of looking around on the internet, and see what I could find out about said bikes. There was a company that produced these bikes in the early 70's, but they never really caught on. There is also a company making these today, called americasbikecompany.com. The original swingbike, and the newer swingbike design, while the same are rather different in design. The original swingbike design was almost more of a unicycle type thing where they pedals were in front of the pivot point by quite a bit. The newer design bikes have the pedals kind of below the pedals. I looked at both designs, and by luck I reckoned that it would be easier for me to build the latter type design, because it could essentially be built with one bike, and a donor bike that would provide the head tube. (NOTE: Look around on the internet for "swingbike", and you'll pretty quickly see the two types of designs that I'm talking about, and what the differences are)
Step 1: Starting point...
These are the things that are required to build this project:
One complete bike. Can be multiple geared, or single speed. I suppose that any size bike would work for this.
One donor bike to get the front forktube, headtube and all hardware from
Heavy walled tubing, or possibly solid round bar (I used 1.25" OD x .375W tubing)
Some plate steel for making the pivot mount (I used 11GA (.120 thick))
Cut off wheel, or way to cut tubing
Die grinder (helps with shaping fishmouths)
Welder (arc, MIG or TIG)
Variety of wrenches to dis-assemble and re-assemble bike
Sharpie or marking device
My cost to build this was more or less nothing, other than the cost of welding gas and wire. I was able to scrounge for the main donor bike, and I've had the second donor bike laying around for several years. At most, I would think that you should be out less than $50 for everything.
As for difficulty, I wouldn't say that this is really a hard project, but it does require a few metal working tools that not everyone might have, or have access to. So, I put the difficulty level at the middle of the range because of that. My total time to build the bike was about 16 hours in all.
Let's get this thing started. This is the only pic that I have of the donor bike, and I don't have any pics of the second donor bike at all. My main bike is a 26" run of the mill cheapo Murray MTB. But, this isn't just any old MTB, this is an Ultra Terrain Extreme! My donor bike was a gem as well. It was a built-for-Kmart bike, and it was ALL PRO. I actually kind of felt a little bad cutting up that bike because it was a brazed together frame, from back in the day, so it was probably a pretty decent bike as far as that goes.
Psh... I got over that pretty quickly though. ;)
My first step was to disassemble my main donor bike, and get to a bare frame. After that, I cut the frame at the arrows indicated as close to the downtube as I could. I wanted the remaining tubes to be as long as possible. In this case, a slightly stretched out bike won't be a bad thing.
Before cutting it apart, I also measured the angle between the upper main tube, and the lower main tube. I needed to know what this angle was, because I am going to cut the LOWER tube at some point, and make it parallel with the top tube.
After making all of the cuts to the main bike, the resultant pieces can be seen in the third photo. Notice that the top and lower main frame tubes are now parallel to each other. The lower tube ended up being mitered very close to the front headtube, and that was fine, since I knew from the measurement I took above what the angle was. I did it this way, rather than cutting these off front head tube, because again, I wanted these tubes to be as long as possible, and this was a good way to recycle these tubes without needing to add more tubing into the project, which I didn't really have anyway.