Over a year ago I signed off of this list, so I could finish my 2WD delta winter trike before snow fell. Well, it didn't happen, so one year behind schedule, I'm back.
Monday I got it to the point where it can be ridden. I'll put on a hundred miles or so of running errands as a shakedown, so I can be sure where to put braze-ons, racks etc. and debug chain management before painting. Only a winter of use will tell for sure, but it works better than I had hoped on dry pavement. With no camber or toe-in it rolls pretty well, even with aggressive knobbies.
My goals were; - Seat height compatible with night riding in traffic. - 2WD with the power going to the tire with traction (ie. freewheels, not differential) - 75% rearward weight distribution and room for a fairing behind front wheel. - 10" (254mm) of tiller, 1/4" (6mm) of trail (laden) - 451 front wheel so I can run narrow (1" to 1-3/8") knobbies on the front. - Keep the project cheap; Total cost so far is about $150, but I'm sure I have better access to used/freebie parts than most folks.
It's not meant to go fast, but to keep going when other bikes are huddled safely in their garages.
I figured that posting pix "as-is" would be more interesting than after I paint over my mistakes.
http://www.bikesmithdesign.com/temp/Profile.jpg 53Kb Overview of the trike, with me looking really cute, squinting into the sun.
http://www.bikesmithdesign.com/temp/Jackshaft.jpg 58Kb The BMX freewheels are mounted on threaded units from a Lightfoot trike. The right side gear reduction is 19-24 while the left is 18-23 meaning that the right wheel is geared a tiny bit higher than the left. This is to counteract any tendency to ride down off the road crown. 8/9 speed freehub outer shell mounted in Center of 3/4" jackshaft. I had worried that using freewheels instead of one-way clutches would act funny when drive shifts from one wheel to the other. The inside wheel gets the drive in turns, but when weaving the bike, the transition is seamless. Homemade bearing carriers and derailleur hanger. Seat and mounts are temporary. Final seat will sit 40-45 mm lower.
http://www.bikesmithdesign.com/temp/Rear.jpg 76Kb Plenty of places for cargo boxes, racks or whatever. I'd rather have narrower rear knobbies for snow and ice, but I won these in a drawing and I'm a bit on the frugal side. The wide track and rearward weight bias allow a higher seat. The front section of the frame and the seat are canted 1.5 degree to the left so they are approximately vertical when riding on the right side of a crowned road.
http://www.bikesmithdesign.com/temp/LeftRear.jpg 56Kb Shows custom dropouts and Canti pivots (inside ones are boxed for strength). The BMX freewheels are so out of round that I had trouble with rear chains derailling. So I added delrin guides. Now that I know where the guides have to be, I'll replace all the ugly clamp-on bits with a nice braze-on. Secondary chains run well inside of the tires so a corroplast fender panel can come down between them.
http://www.bikesmithdesign.com/temp/Front.jpg 61Kb The long front center, 22" (56cm) aids weight distribution and allows me to keep the front wheel outside of a fairing (experienced winter riders will understand why). The shallow head angle is needed to avoid excess tiller, so I needed a ton of fork offset (rake) to avoid excess trail. Steers great
http://www.bikesmithdesign.com/temp/ForkCrown.jpg 38Kb One way to shorten a MTB fork and give it 5-3/4" (146mm) of rake. I have a plan to cause a front brake to be actuated only when both rears are used at once, so I can use brake steering in really slippery conditions, but have all 3 for stopping. If it works I'll post.
http://www.bikesmithdesign.com/temp/StemAdj.jpg 38Kb The bike is too wide to get through a doorway, so the the stem folds back allowing it to be carried through doors sideways. Final seatback will also fold, forward. Bottom curved slot is where for/aft adjustment is made so that using the QR doesn't alter adjustment. Tape and clamps for cables are temporary, till I determine where to put braze-ons.
Thursday, 29 January 2009