Design Overview
Recycling
In my opinion the problem with today's diamond frame bikes
revolves around the placement of the components not the quality
of the parts. As much as possible I try to use existing 2nd hand
bike parts, not just because it's easier but also to save money.
In our country (and I suspect in many) these can be sourced at
garage sales, tip shops and charity shops. I also find that as
other see the work being done they target you with their surplus
machines. Using old bike parts can be challenging at first as you
have less control on what your working with but I find it a very
rewarding process.
Design pitfalls
It seems to me to be a given that when people build a
recumbent cycle they stray from the existing designs adding at
least a few of their new ideas. If you're one of these people
here's few tips to keep in mind.
Trikes
- Be careful with the seat to crossmember distance on
tadpole style trikes. The rider's calf muscles and heels
sweep an arch that can easily interfere with the
crossmember. On many machines it's almost too late to
change this after it is welded up and can make for an
unrideable cycle. I know of one builder that had to move
the seat forward because of this that really became a
problem as it only had a rear brake and braking
performance was compromised further - also more
(unsightly) structural material to mount the seat.
- There's a lot of force on the crosmember on a trike. If
you choose to have a main boom pass on the same line as
the crossmember I'd suggest you cut the boom for the fit
not the crossmember.
Bikes
- Seat to steering neck to bottom-bracket distance on SWB
bikes can be tricky to get right. Heel to front tyre
interference can be a problem in a turn, Knee to
handlebar clearance on above seat steering machines are
critical - it's nearly impossible to ride if your knees
are hitting the bars and raising the bars too high really
can look funny. (sit and beg)
All
- Chain route needs to be predicted in the design before
cutting out the material. In fact one could argue the
whole machine ought be designed around the chain route,
especially if it a low machine.
The lower number of guide rollers means less weight, less
friction drag and less fabrication work. With under seat
steering the handlebars and sometimes control rods pass
near the chain - also the chain rises and falls with the
different size cogs selected which can end with
interference. Remember the chain moves sideways too as it
goes from the larger to the smaller cogs and can easily
interfere with the frame on it's full inside path. If you
modify/totally fabricate the rear drive end be sure the
chain clears the chainstays (forks) in all gears,
especially the smaller cogs.
- It's very rewarding experience carrying through your own
design to completion and finding it works as intended but
I would suggest for your first project using an already
proven design. There's a lot to learn, especially if
you're also learning a welding process for the project
too and many things crop up that are very hard to
predict/forsee till you've had some experience.
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Last Updated Friday, 30 January 2009