Triumph back rod holes ?

[mjbarnes]

My Triumph D2 back rod does not have the helical oil grooves, so maybe it was swapped with an older rod at some time in past. But why are there these two holes at one end? There is a single centre hole at the other end.

[phonojim]

Frow says that the D2 should have the spiral oil groove, but mine does not have it either. As far as the offset hole in the end of the rod, mine also has that but I have no idea why.

[JerryVan]

In manufacturing, when we grind diameters of shafts, such as these, we commonly add a "drive hole" in the end of the shaft in order to "drive", or rotate it, as the grinding wheel removes material from the diameter. The "drive dog" would engage with the hole, or with a pin sticking into the hole.

[phonogfp]

In manufacturing, when we grind diameters of shafts, such as these, we commonly add a "drive hole" in the end of the shaft in order to "drive", or rotate it, as the grinding wheel removes material from the diameter. The "drive dog" would engage with the hole, or with a pin sticking into the hole.

Thanks Jerry! I've always wondered about that extra hole.

George P.

[mjbarnes]

I add my thanks for the explanation.

[JerryVan]

You're both welcome. Realize, I don't state this as a known fact, but it certainly aligns with common manufacturing practice.