Which differential for a scratchbuild?

[eschaider]

Bob's point about the IRS housing mount front and rear is significant. For best results you need to mount both the front and back of the diff with mounts of similar hardness or the give of the softer mount will damage the more solidly mounted, mount.

Delrin is somewhere between a polyurethane mount and a solid mount. The ring and pinion meshing sound and ever so slight vibration is an undesirable side effect (for some) of a solid mounted IRS unit. These folks usually go to a polyurethane mount that, while quieter will unfortunately deteriorate with age. A better choice is Delrin. Delrin is a much more robust material with good life expectancy and relatively easy to machine.

The other choice is UHMW polyethylene (UHMWPE). Don't let the polyethylene part of the name scare you off. The UHMW part of the name means Ultra High Molecular Weight. UHMWPE is a type of polyolefin. It is made up of extremely long chains of polyethylene, which all align in the same direction. It derives its strength largely from the length of each individual molecule chain and the chain to chain overlap. The molecules are very long allowing for large overlaps providing the ability to sustain larger shearing (and compressive) forces molecule to molecule.

Outside the scientific community UHMWPE is used for composite plates in personal and vehicular armour. It will provide impressively good mounting strength while also attenuating some of the vibration and gear meshing sound that possibly delrin (If you are sensitive) or solid mounting with steel, might transfer to the drivers ears or seat of the pants.

Although it is not inexpensive, it is readily available. Amazon sells it in both sheet, rectangular bar and round bar form. You can also find it in most industrial and scientific supply houses.


Ed