Ive added the wheels & engine and loaded it down to about where it’ll be at rest, with me in it. Ground clearance is 3 inches. I’ll be adding some welded gussets to the extruded ally angle, and some tabs to attach the arms of the watts linkage to, which looks to be ideally situated vertically, at the forward end of the square framework, in the middle. that’s about 1.75inches below the axle centreline. I can set it lower by anything up to another inch and a half by setting it horizontal and mounting it under the frame.
The rubber bands will connect to the square frame, and loop to transverse ally tubes held via U bolts on the underside of the ally.
As many people will point out, rubber bands are great in one direction but rubbish in another. If I were to leave it at this point, I’d have just one more job todo and that would be to paint ‘miss deathtrap’ down the side….
So I’m not doing that.
As far as I can tell, suspension as a whole is a complex 3D process, with many variables, and dynamically changing loads that ideally need to be balanced out.
From a guitar makers perspective, it’s almost exactly like designing a tremolo bridge system for a guitar. Lots of dynamically changing loads that need to be balanced out and damped so the system reliably returns to an adjustable zero point, with dynamics and feel to be adjustable by the end user.
Also needs to account for different playing conditions, heavy/light strings, different scale lengths and tunings etc….
Various solutions exist, consisting of all sorts of leaf spring, coil spring in tension, coil spring in compression, and torsion bar designs…
All this needs to be fitted to a lightweight, resonant yet quite astonishingly strong and by turns, rigid and flexible structure….
Omg it’s a racing car isn’t it?
Heheheheeh…
So anyways. Just like on a guitar tremolo, The springing forces need to be balanced in both directions… so they can take heavy deflections in various axes and return to an adjustable loaded zero point with a suitable sort of damping action…so in this case, positive (upwards) deflections of the axle are taken care of by rubber bands… negative (downwards) deflections are taken care of by a couple of conical rubber dampers, situated under the square structure, facing up.
The more towards the centre line these dampers are situated, the livelier the suspension will be.
The more towards the chassis rails, the more rigid it will be.
The cones will be adjustable vertically via way of shims, and horizontally via a selection of mounting holes, from centreline outwards…. At ‘loaded neutral’ ie with me in the car but not going anywhere, the cones will be positively but not excessively loaded. I’m expecting to find a sweet spot with them both closer to the centre line rather than towards the chassis rails.
The cones are available in a huge number of sizes, hardness ratings, spring rates, materials, maximum weight ratings etc. Mine are rated at 116 kg each, and 57 shore hardness, natural rubber and M8 stud mounting. Roughly 50 by 50mm.
This entire idea was inspired by the various works of Alec Issigonis (rubber bands and conical rubber springs anyone?) and also several excellent phone conversations with Rhys, hopefully once I post the pics it should make a bit more sense. Anyways. I reckon it’ll either corner like its on rails or else I’m going straight into the hedge at the end of our lane on first test run….