Author Topic: How to make a new gearbox shaft seal  (Read 986 times)

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Offline ThomasC11

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How to make a new gearbox shaft seal
« on: February 15, 2016, 08:05:41 am »
Hi all! Attached is a pdf about how to make a new gearbox shaft seal. The original one on the back primary cover is often damaged introducing significant oil loss. Cheers, Thomas
1946 BSA C11
1937 Sunbeam Model 9
... and a dented Opel

Offline chaterlea25

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Re: How to make a new gearbox shaft seal
« Reply #1 on: February 15, 2016, 07:43:40 pm »
Hi Thomas,
I dont think that the original setup had any felt seal fitted??
Any improvements would be welcome
You have mimicked the setup that is used on the bigger A, B & M models
On these the bolts that hold the sliding plate have little shoulders on them thet locates the plate but still lets it slide for adjustment
On those a felt ring is fitted to a recess in the rear cover, sandwiched between the sliding plate and case(this doesnt work very well :( )
An alternative is a cork ring or a type of soft rubber is available
the sliding plate runs on a reverse scroll on the clutch adaptor, again a not so clever idea as the fit is not tight

You can see all the bits on this ebay search
http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2060353.m570.l1313.TR0.TRC0.H0.Xbsa+sliding+plate.TRS0&_nkw=bsa+sliding+plate&_sacat=0

An aftermarket alloy sliding plate is available that has a lip seal and a bronze bush to keep the seal centered, this is probably the best solution

Regards
John
 

Offline ThomasC11

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Re: How to make a new gearbox shaft seal
« Reply #2 on: February 15, 2016, 09:29:43 pm »
Hi John, that is an interesting input. I was indeed inspired by the solution for the A, B & M model. However, touching the gearshaft remains possible if it the plate not fastened. So, I applied regular bolts but not those with a shoulder. As I wrote, the felt washers were just an assumption. This guess is not important for my idea, though, because I waived the bad original design entirely. A second problem is the collar at the A, B & M model. The space between back plate and primary back cover is really small and I am not sure if this works without touching one of the parts. Your are certainly right with a cork ring or soft rubber (I asked for a rubber ring at a local dealer). Maybe a lip seal and a bronze bush are a better solution, or a leather ring. I simply don't know. Overall, a new seal remains a delicate affair and it is not too easy to find a really good solution. After some hundred miles I will know how good my idea was.  ;D

Cherio, Thomas
1946 BSA C11
1937 Sunbeam Model 9
... and a dented Opel

Offline Dstep

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Re: How to make a new gearbox shaft seal
« Reply #3 on: April 12, 2016, 04:33:47 pm »
Hi Thomas,
Great write up, you do very nice presentations of your ideas. I have saved them all, thanks very much.
Read the comments between you and John which started me thinking of how to fix my C11. Don't know if what I came up with will work any better than your design, but it was easier for me to make. John mentioned a bronze bushing on the shaft, so I just made a brass shield that fits the output shaft and fits between the two hubs. Didn't try to add any seals as there is not much room to spare.  Photos don't show it, but I added a 1/16" diameter pin at the very edge of the disc, that protrudes 1/16" and contacts the shield to keep the disc from spinning. The disc just rides the shaft (0.004" clearance) and the transmission can be adjusted easily without removing the chain cover.
I also added a stiffener plate to the chain housing where it bolts to the engine. Really helps to make the assembly very rigid.

David
'52 BSA C11
'50 BSA B34
'67 MGB Roadster
'00 Kawasaki W650

Offline chaterlea25

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Re: How to make a new gearbox shaft seal
« Reply #4 on: April 12, 2016, 08:22:30 pm »
Hi,
Quote
I also added a stiffener plate to the chain housing where it bolts to the engine. Really helps to make the assembly very rigid.

Great idea David  8) 8)
 
John

Offline ThomasC11

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Re: How to make a new gearbox shaft seal
« Reply #5 on: April 13, 2016, 07:09:12 pm »
That is indeed a nice idea, David! It may well be an even better solution than mine. Thank you for your encouragement. My intention are texts easy to read as a motivation for others to find better solutions. I would never claim that my considerations are the best. And what you do not write down never happened, I would say.

Maybe you and some of our colleagues could write their own texts (or take them from our forum), write them in WORD and send them to me. Then I could use the LATEX editing language (as I did for my texts) and combine them to a small "How To..." booklet with pictures. I mean, I can already contribute five texts. Just a quick idea...

Cheers, Thomas
1946 BSA C11
1937 Sunbeam Model 9
... and a dented Opel