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