Experimental Delta Recumbent Trike
Recumbent = lying down (or at least sitting and leaning back). This results in increased comfort and reduced air drag and pedalling effort.
Delta = a tricycle with 1 wheel at the front and two at the back.
Most pedal recumbent trikes follow the "Tadpole" scheme, with two wheels at the front and one at the back. The downside for a homegrown construction is the difficulty of building the steering mechanism and getting effective (ie, front-wheel) braking. Still, it can be done, eg, Tim Smith's trike. Standard bike wheels are designed to be supported on both sides, and do not have axles stiff enough for single-side mounting as used on commercial tadpole trikes and all cars. Tim Smith gets around this by using 20 inch rear wheels from BMX bikes, as these have a thicker, stiffer axle.
The tadpole also has the disadvantages (from my reading, not from experience!) of a very long chain run and a tendency to scrub the front tyres.
On the other hand, the simple delta type, with rear-wheel steering, has a reputation for getting unstable in corners at speed, and downhill at speed, which rather tends to offset its simpler construction. Google for "jouta trike", "raven trike", "Gthun" and "forelle trike" to see some.
Well hopefully if I ever get to build it, the frame will be straight, not twisted, but my idea for a design has two twists that are not in the typical deltas
Here's a (very) rough sketch plan view and a side view
The twists are
While on holiday earlier this year I made a cardboard model as an amusement. Here are some photos
The wheels are made of 2 shallow cardboard cones taped and glued together. The tyres are slices from a yellow balloon.
The motor is actually the chassis of a $2 toy model car I picked up a few years ago. Stuck on with U-Tac (sticky putty - think of Blu-Tack). Rubber band for drive to the front wheel.
Here is a short movie of it running in a wide circle at speed. You can see how the lean steering works. Hopefully on a real one, the moving of the rider's mass into the centre of the turn will offset the over-steering tendency (along with a powerful enough steering mechanism, and probably a steering damper. Trike Model at speed
This page tardus.net/deltaTrike.html Last updated: 09 Aug 2021