As previously mentioned I’ve used off-road motorbike rear shocks and bell cranks. I plan on having bell crank suspension both front and rear.
Most Haynes Roadsters or Locosts have outboard coilover shock absorbers. Some people think that going inboard with shock absorbers is all about sprung weight, aerodynamics and looks. There is far more to it than that. By using cantilevers, the spring rate can actually be increased the more the suspension moves. Much the same as adding an anti-roll bar does. Wide spread usage on race cars and motorbikes since the 70’s suggests it’s worth investigating.
I’ve not changed a lot here, basically some of the tubes have been angled or triangulated, some of the brackets have been shortened and one extra brace added. I’m no expert at FEA (I just go by colour), but there are now no areas at the rear that show significant flex. Ages ago, I modelled the standard rear end and that seemed ‘OK’, but without adding much weight I’ve gain significant rigidity.
The aim is to get a rising spring rate during roll – see Cantilever Suspension
A lot of motorbikes have some quite pretty, lightweight and strong bell cranks. They have needle roller bearing and really look the part (Haynes Roadster Bling!).
If you chose a coilover shock from a off-road motorbike the spring rates will be far closer to what you can use on a road car (roughly 300lbs). Sports bikes have spring rates approaching 1000lbs!
For the rear (where there is more room) I have gone for so rather large DRZ400 shocks. They’ll be too big for the front, so I’m still looking for suitable front units.