The no weld crank forward was fairly successful but I decided to try perfecting the bike with some cutting and brazing. The original bike was an old High Sierra Schwinn mountain bike. One of the more serious shortcomings of this rendering of the bike was its tendency to pop wheelies on takeoff. The seat sits almost over the rear axle. The bike did not handle badly but I figured sooner or later I would forget which bike I was on and end up being dumped on the pavement.
My plan was to stick pretty close to dimensions on one of RANS new models they offer taller riders called the Sequoia ( http://www.ransbikes.com/Sequoia.htm ). Wheelbase on crank forward number 3 came out 53". It is very stable and comfortable. I'm still messing with the handlebar setup--I have a set of RANS B38 bars I may try on it. I plan to paint it dark green similar to the original mountain bike's color--the fork will probably not get repainted at all.
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Crank forward bikes are considerably simpler to build than recumbent bikes as the origingal steering angle and bottom bracket position can be retained thus eliminating fork bending and cutting on the down tube. Basically the seat ends up about 6 or 8 inches back and the chain stays are extended about 7". I keep about 5" of the old seat post for mounting a front derailler and attach a new seat tube to the base of the old one and angle it back at something closer to 50 degrees rather than the original 70 degrees. Mountain bikes seem to be better suited to conversion into crank forwards but I think an old road bike could be cut up for this purpose. Crank Forward bikes make great commuter bikes and city cruisers whereas recumbents are probably a better choice for longer road trips.
3 comments:
Very nice. Looks like you solved the problem of weight distribution over the rear tire while giving the rider a comfortable body position for the average ride. I've been thinking about building a freak bike but was always concerned about putting most of the body mass over the rear wheel, especially at the height involved for that type of bike.
What type of welding technology do you recommend for a new builder with steel frames?
New builders working with steel frames are usually advised to use brazing for bike building. Brazing is one of the easier methods to produce strong joints and is about as economical as any system to get started in. Joint strength is very good when done reasonably well. Plain brass is about half the strenght of Cro-mo steel so fillets only need be twice that of the thickness of tube wall material. For folks that have a mig welder and are comfortable with using, low end bikes with thick tubing can be nicely done but thinwall Cro-mo in the .035" range would require very fine wire and a skilled welder.
Forrest
Thanks for the input!! Keep on truckin"!!!
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