General => Douglas Motorcycles - General Discussion => Topic started by: Keith on 19 Jul 2019 at 07:49

Title: Reproduction rear sprockets for CWs
Post by: Keith on 19 Jul 2019 at 07:49
I mentioned in an earlier post that a friend (and his brother) are working on reproducing the rear sprocket for the CWs. The project is progressing well and this week I received the first one to check the fit of the splines and also the teeth for specification. The sprocket fitted perfectly on the 4 hubs that I have and the teeth are machined to Renold 110044 chain specification.

The offset 'dish' has not be applied yet but the sprocket has been returned to have that done. We are still discussing the actual amount of dish required as the only genuine sprockets we have access to are badly worn and somewhat mangled. We have had input from a couple of members with their own sprocket dish specs, but there is still a fair amount of variation. Does anyone have actual engineering specs for the sprocket?

Anyway, here are the pics of the prototype I received. The quality of the finish and engineering speaks for itself. The finish is a fine bead-blast. Once all machining and shaping is complete then the teeth will be hardened.

More updates soon!   :P

Title: Re: Reproduction rear sprockets for CWs
Post by: eddie on 19 Jul 2019 at 08:09
          May I make an observation? As the sprocket rim is supported by 6 'Y' shaped legs, when the dish is pressed into it, it may pull the outer rim inwards in 6 places. Having dished the trial sprocket - check that it is still truly round - you may need to do the forming of the dish prior to cutting the sprocket teeth.

  Also, any heat treatment of the teeth may result in more distortion - in practice, teeth left in the soft state are almost as durable as hardened teeth - so the extra work and problems may mean the soft option is better ( especially as high milages are less likely these days).

Title: Re: Reproduction rear sprockets for CWs
Post by: Keith on 19 Jul 2019 at 09:57
Hi Eddie, yes all good points.

We had some discussion as to the best way to do the dish and as it was going to be relatively easy to make the male/female die the guys are going to give that a try first. The actual amount of the dish will probably also affect the success or failure of pressing. But it was acknowledged that they may have to be machined from a thicker block in the long run if die pressing does not work. Watch this space!

I'll pass on your point about hardening as well.

Thanks, Keith...
Title: Re: Reproduction rear sprockets for CWs
Post by: Keith on 06 Aug 2019 at 02:06
I now have the sprocket back with the offset done. In my case I only needed about 6mm for correct alignment with the gearbox sprocket. There was no distortion as a result of the dishing process and the sprocket tracks perfectly with no wobble. The spline was unaffected by the process and the teeth maintained their correct alignment. I specified Renold 110044 chain specs and the new chain I have fits perfectly. I made a new locking ring for the sprocket which you can see in the pics.

So a great result and I'm really impressed with the quality. I'm not having the teeth hardened and I'm not plating it either since the bike is in mostly original unrestored condition and I'll let the sprocket weather naturally (which won't take long in my subtropical seaside location!)

Title: Re: Reproduction rear sprockets for CWs
Post by: Keith on 27 Aug 2019 at 10:29
I've just received a second CW rear sprocket which has been manufactured slightly differently by changing the machining sequence. It's just another part of the R&D going into these sprockets to make sure that they are the best that modern CNC can produce. It also came with a new locking ring which was created from my rather poor original. It fits the sprocket and the hub thread perfectly.

I know that other CW owners are desperate for these and some have already contacted me. They will be made available soon directly from the manufacturer, so hang in there!


Title: Re: Reproduction rear sprockets for CWs
Post by: Keith on 10 Dec 2019 at 23:19
Hi Everyone,

Good news! - the sprockets are now available direct from the manufacturers "Buyold Engineering".  :D
This is from their website which lists current available sprockets and prices:

Buyold Engineering is a small Machine Shop based in South East Queensland, Australia, owned and operated by two brothers who are vintage enthusiasts with a passion for delivering quality.

We pride ourselves on manufacturing items that exceed our customers’ expectations and specialise predominately in pre-war motorcycle sprockets.

The website link is:

Title: Re: Reproduction rear sprockets for CWs
Post by: Ben K on 11 Dec 2019 at 10:41
Many thanks Keith,

Much appreciate all the help you have put in testing the sprockets for us and providing the invaluable feedback. They have now been tested on three different bikes and the fitment is excellent on each.

Just as a note, we are taking a bit of well-earned time off over Xmas, so any sprocket orders wont be filled until the end of January 2020.

Please feel free to drop us a line if you want a chat over that period - we are very happy to talk sprockets at any time.

Many thanks
Ben and Phil
Title: Re: Reproduction rear sprockets for CWs
Post by: Keith on 17 Apr 2020 at 23:06
The new primary sprockets for the CW arrived this week from BuyOld Engineering. They came vacuum wrapped to prevent rust flashing during shipping and it also keeps the parts nicely secure especially when small parts like the rivets are included. The parts were up to the very high manufacturing standard I've come to expect from Phil and Ben. The clutch sprocket is also available in 12-rivet format for the EWs. The cush drive sprocket fits both.

I'm also showing the old and the new sprockets side-by-side.

Cheers, Keith...

Title: Re: Reproduction rear sprockets for CWs
Post by: graeme on 21 Apr 2020 at 07:25
Somebody got their money's worth out of the front sprocket!  :o  :lol: