Slimline Dominator rear drum/sprocket

hi Tom

LAN atlas sprocket will fir the same as early commandos!

Fit a 3/8" wide Dominator rear sprocket. Lots of Domis have them fitted (mine included). Not sure if a Commando one would do.Gordon.

I'm pretty sure I've a Commando one on my 58 Dommie as the studs are UNF so you would need to change the sleeve nuts as well.

Here's an interesting problem! I'm the proud owner of a Triton, which consists of a 1960 Dominator 88 with a Triumph 6T Thunderbird engine & 'box. I've noticed recently that the front (gearbox output) sprocket is worn and needs to be replaced - however, the standard Triumph sprocket is 3/8" wide, whereas the rear sprocket on my bike (which is correct for this machine) is only 1/4" wide! I've not removed the front sprocket yet to see what 'modification' the builder made - however, the bike is currently running a 1/4" chain.

I think I have two options:

• machine the new front sprocket down to 1/4" thick
• obtain a new rear drum with a 3/8" sprocket (ideally 42 tooth)

My question is whether it's possible to fit one of the later Commando drums (which I see were fitted with 3/8" sprockets) to my Dominator rear wheel? I'd quite like to convert to a 3/8" chain, as the 1/4" chain looks a bit weedy tbh.

I'd be really interested to hear your opinions on this one!

hello well if you need a 3/8 sprocket and drum I have one in very good order and you can buy this of me for £20 how much the post will cost I will have too fin out. Yours Anna J Dixon Email annajeannette@btinternet.com

I have just checked the drum from my Domi (1/4" sprocket) and it has 7/16" 26TPI threads.

The confusion might be coming from the fact that 7/16" is sometimes listed as both 26 TPI and 20 TPI for 'cycle threads'. What we commonly refer to as 'cycle thread' is really BSC (or BSCy) and this is, I believe, a sub-set of the range of threads known as CEI (Cycle Engineer's Institute). Effectively, BSC is a 'rationalised' version of CEI (ie with the odd sizes/pitches removed). However, most 'cycle threads' in common usage are 26TPI. One exception I know of is the primary chaincase nut as I think this is 1" 20 TPI.

Finally, both BSC and CEI are 60 degree thread forms (compared to 55 degree for Whitworth and BSF). 60 degree is also used for metric and UNF threads.

So, in conclusion, perhaps the Commando drum has 7/16" UNF (20TPI) threads - but would this not be 3/8" sprocket?

Hello Tom is Sorted with rear sprocket 1/4x3/8 He bought one of Me his bike maybe a Triton but well sorted triton have fun yours Anna j