The next bike I build will be a “swing” bike.
Swing bikes are an interesting concept. The basic idea is to have the top tube section act a bit like a a fence door. The bike can steer on the front end or the rear end for a unique riding experience.
This bike is for Tim. he used to have a swing bike from another builder but it cracked. My plan is to build him a similar design but with improved materials and fabrication. We want this bike to be more then just an “art” project. Tim plans to use it for his daily commuting and as such the bike will be built up with gears and must be strong enough for real world use.
Tim’s old swing bike…
On Tim’s prior bike the seat tube failed so on our build I want to have a much stronger seat tube.
On bicycle tubing the tubes are created with different wall thickness on the ends and in the middle. Bicycle tubing works great because tubes don’t really need to be thick across the entire length because stress from welding only occurs at the joints and as such you only really need the thick walls for 2-3 inches around the joints. Bicycle tubing is great stuff but the way the wall thickness is setup the builder is really locked into a traditional sized and shaped bike.
For the swing bike, the seat tube and top tubes will be sized and welded much differently then a normal bicycle frame. We need the option of putting a nice solid weld in the middle of the seat tube. The bike will not have a traditional down tube and the top tubes on it need to be a bit shorter then you would normally find. Since the goal is strength rather then saving weight some 4130 straight gauge for special tubes makes sense. The bike will still be reasonably light because I am simply using slightly thicker walls then thick section of a normal bicycle frame tube.
I ordered a good bit of 4130 from an aircraft supply shop. This will be a unique off-the-wall build and as such I want to have a wide assortment of tubes around to try out ideas.
Next weekend I will light up the torch on this stuff.
This build will be lots of fun because it is so different from a normal bike.