Do-It-Ourselves Plastic Trikester
The Plastic Trikester is essentially the same design as the PLASTIC-X except that it uses a 5" x 1" caster rather than a pneumatic 6.5" x 2". In addition, the Plastic Trikester does NOT use a through axle. It is designed to use the standard wheelchair 1/2" quick release axle. I think a through axle is more sturdy for rough terrain. Therefore, I consider the Plastic Trikester to be a hybrid wheelchair (like a hybrid bicycle) to be best used on pavement, dirt, grass, and gravel, but not really rough terrain.
I am currently using my Plastic Trikester for "running" road races.
5" x 1" Solid Caster vs. 6.5" x 2" Pneumatic Caster
Shorter or No Legs
The 6.5" x 2" caster tenders to flutter/vibrate on pavement at higher speeds while the 5"x 1" does not vibrate at high speeds. Vibration is only an issue for smooth surfaces, uneven surfaces (off-road) do not cause vibration.
The 5" x 1" caster should be made of rubber rather than plastic for a quieter ride.
Home Depot - $25
Amazon - $18
The Quick Release Axle
1/2" Axle Receiver
The axle receiver is made out of 1" punched square tube which was drilled to create two 1/2" holes for the wheelchair axle. It is bolted to the side of the frame as show. I added an additional 3"x1"x13.5" cross-brace to increase rigidity (not shown).
I have NOT done extensive stress testing on this design except for long pushes on paved bike paths where it performs very well.