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Triumph back rod holes ?
Posted: Tue Dec 31, 2024 2:30 pm
by 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.
Re: Triumph back rod holes ?
Posted: Tue Dec 31, 2024 8:05 pm
by 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.
Re: Triumph back rod holes ?
Posted: Tue Dec 31, 2024 8:12 pm
by 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.
Re: Triumph back rod holes ?
Posted: Tue Dec 31, 2024 8:46 pm
by phonogfp
JerryVan wrote: Tue Dec 31, 2024 8:12 pm
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.
Re: Triumph back rod holes ?
Posted: Wed Jan 01, 2025 6:42 pm
by mjbarnes
I add my thanks for the explanation.
Re: Triumph back rod holes ?
Posted: Wed Jan 01, 2025 7:42 pm
by JerryVan
You're both welcome. Realize, I don't state this as a known fact, but it certainly aligns with common manufacturing practice.