The BSA A7-A10 Forum

Technical => Clutch, Primary, Gearbox => Topic started by: Brian on 11.05. 2010 01:48

Title: Plunger Clutch
Post by: Brian on 11.05. 2010 01:48
This may be of interest to owners of plunger and rigid models.

The plunger A10 I am currently working on had a worn and damaged bearing in the clutch, the outer race is removeable but unobtainable and the inner is part of the hub.

I bought a 6807 bearing which has dimensions of 47mm OD, 35mm ID and 7mm wide. I left the old outer in the chainwheel but turned it out to accept the 47mm OD of the bearing. I then made up a sleeve that fitted over the original inner but had a outer dia of 35mm to accept the new bearing. The original bearing is 1/4" wide (6.35mm) whereas the new bearing is 7mm, the difference gives clearance on either side.

The bearing is sealed and I have left it sealed, I am confident the grease in it will be sufficient plus it seals the plates from the oil in the chain case.

I just have to rivet it all back together and hopefully that will be one more problem solved. I put the basket in the mill and faced off the fingers. You can do this with a file and I have many times but by doing it in the mill the distance between each finger is exact so the plates will load evenly. A new set of springs and Surflex plates and all should be well.
Title: Re: Plunger Clutch
Post by: orabanda on 11.05. 2010 05:03
Good work!
Title: Re: Plunger Clutch
Post by: beezalex on 11.05. 2010 14:19
Very nice.  I did a similar conversion on my A65 belt drive clutches since they run dry but I hadn't thought about the benefits to the plunger clutch.
Title: Re: Plunger Clutch
Post by: muskrat on 11.05. 2010 19:31
That's a nice job Brian, and seems so simple. I will use that next time the '51 clutch is apart. Thanks.
Title: Re: Plunger Clutch
Post by: olev on 17.05. 2010 12:11
I'm about to rebuild a clutch just like yours.
The 6807 ball bearing looks interesting.
I know stuff all about bearings but notice this thing has load ratings of
Dynamic - 480 Kgf and Static - 390 Kgf.
Will this bearing be doing serious work?
Do you think its good enough?
& where do you get your surflex plates?
Title: Re: Plunger Clutch
Post by: Brian on 17.05. 2010 12:51
Olev, I get my plates from RectoryAntiques in the UK, you can find them on e-bay.

I thought a fair bit about the load capability of the bearing as its not as substantial as the original but this bearing is only in use while the clutch is dis-engaged so I think it will be ok. Its one of those things that time and a few thousand miles will tell. If the inner and outer races of your original are ok I would just put new rollers in and stick with that but if, like mine, they are worn or damaged then you have to find an alternative. I would have preffered a roller bearing but none are available in the width required.

Here's a link to the plates.