This resulted in a diagram of the different layouts I found:
View attachment 713223
Red represents the spring, blue the arm/structure, orange the pivot point, green the roadwheels, purple the gear/arm structure (where applicable), and brown the bogie structure (where applicable) which pivots on the blue point. Although only shown for the direct unit, any of these layouts can have 2-wheel bogies in place of roadwheels. This, plus whether the unit is mounted inside or outside the armored structure, leads to some extra designations to distinguish the variants of these layouts:
- Bogie: All roadwheels in a layout are replaced by 2-wheel bogies (i.e. the Medium Mark I's suspension)
- Semi-Bogie: Only applies to dual layouts with 2 roadwheels per unit, 1 roadwheel is replaced by a 2-wheel bogie while the other road wheel is left as it is (mainly used on the Cruiser Mark I/II/Valentine)
For normal roadwheels, there is no prefix
For mounting location:
- Internal: The entire suspension including roadwheels is covered by armor (i.e. Churchill, Matilda II)
- Semi-internal: The suspension springs are inside the armored hull, but the roadwheels and roadwheel arms are outside (i.e. Christie)
- External: The entire suspension is attached to the outside of the armored hull (i.e. Horstmann)
External mounting is assumed if there is no prefix.
For the types of possible springs I found at least:
- Elliptical spring (Never used, but it does qualify as pushing in a straight line, so why not)
- Coil spring
- Solid rubber
- Volute spring
- Belleville washers
- Hydrogas piston
- Hydropneumatic piston
Under this system, for example, a
Matilda II suspension would be classified as an Internal bogie dual horizontal bell crank using a coil spring.
If comparing just layout and spring type combinations, then a table can be made of all possible suspensions, including existing ones:
Existing suspensions in this system are external and using normal roadwheel unless otherwise mentioned.
Also, the Citroën 2CV seems to have a suspension almost identical to the Japanese "scissors" suspension- that being dual inverted horizontal bell crank using coil springs.
Since all of those layouts (except the direct unit) represent levers in some fashion, the lengths of the arms can be adjusted to provide any given travel for any given spring compression, and the springs themselves can be adjusted in length, to provide whatever suspension performance is required. But for some combinations this may require impractically large suspension arms and/or springs, or the given springs can't be made large enough (volute). This is likely why many of these hypothetical suspensions don't exist OTL.