Tuesday, 12 January 2021

Model A - First Impressions of a Clutch

Isn’t it a bit early to be looking at the clutch on that bike, when you have so many others in the pipeline I hear you ask? Well, yes it is, but a while back I lost one of the tank bolts on the W/NG - you might remember I made a new one; I am diverting myself with lathe jobs as a distraction from all the welding on the QR50, and part of the lathe work is to collect the bits for the gear control on the Model A, and to do that I need to mount the tank - which is another lathe job, as one or two of the bolts are missing - so I need the tank mounting rubbers for that too, and I also want to trial fit the tank on the FH and I have no rubbers...

So what I need to do is to get an order for Jeff Hunter Engineering, who will supply all the rubber bits and what I am going to do is order as much of the rubber as I can, for all three Ariels. And this is where the clutch comes in - the Sturmey Archer clutch in the Model A has a rubber shock absorber in the clutch and this is bound to need some attention:


So let’s have a look. It’s very easy to get to as in 1930 Ariel were not using the fully enclosed and sealed primary drive, and my primary cover is off awaiting time on the welding bench:


Clearly, two of the retaining bolts, springs and spring cups are missing. Those bolts actually have screwdriver slots under that muck.

Under the pressure plate, the basket and centre are very good indeed:


The plates are reasonable too, but I wasn’t expecting Ferodo linings:


The parts list clearly shows a cork lined clutch:


Yet if we look in the Sturmey Archer book from the period, there is a Ferodo option for the three plate clutch. Interesting.


We’ll have to replicate these parts, though I wonder if they have been intentionally omitted. Ferodo clutches of the period can be quite heavy - the one on my W/NG is much less pleasant than the cork clutch on the SQ4, for example.


Still, it will be a long time before we have to deal with that problem.





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