Julian Edgar, 50, has been writing about car modification and automotive technology for nearly 25 years. He has owned cars with two, three, four, five, six and eight cylinders; single turbo, twin turbo, supercharged, diesel and hybrid electric drivelines. He lists his transport interests as turbocharging, aerodynamics, suspension design and human-powered vehicles.
Damping
As many of you will know, on my recumbent pedal trike I use a Firestone airbag for rear springing. This air spring has major advantages over other springing approaches but as it has little intrinsic damping, external damping is needed.
The rear damper is an ex-R1 Yamaha motorcycle steering damper. This is an unusual design for a motorbike steering damper in that it runs an external passage connecting the sides of the piston. The piston is a loose fit in the bore. The damping action in standard form is provided by the oil passing through the bypass passage, and also making its way past the loose piston. (I assume that the steering damper can be tuned in its action by placing restrictors in the bypass passage.)
To make the steering damper suitable for use as a suspension damper, I modify a plug in the external passage and insert in this passage a one-way valve. This allows free-er flow of oil on bump and more restriction to flow on rebound. Bump damping is therefore provided by the oil flowing in the bypass passage around the open valve and also around the piston, and rebound damping by the oil flow past the piston only.
This gives the desired asymmetric bump/rebound damping.
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