The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Frame => Topic started by: Russ on 27.07. 2021 12:33
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On my 51, A10 Plunger the two "Rear spindle clamp lugs" are not identical. The off side one is correct, being part number 67-4126. This side has the grease nipple on the outside of the spindle clamp. The "slot", for want of a better word, which the axle passes through and allows it to be adjusted to tension the chain is 1 -5/8" long on this side.
The near side spindle clamp is part number 67-4125, but their is no number on the actual part. The grease nipple on this side is on the rear of the spindle clamp? The "Slot" on this side is 2 -1/8" long. When fitted in the frame the front of both spindle clamps sit approximately the same distance from the spring shrouds, allowing for 1950's B.S.A production standards.
As the near side clamp is longer it naturally extends further rear ward of the frame than the off side. Trevor and WoZZa both have Plunger units but theirs have the grease nipple on the near side clamp mounted on the outside.(mine being on the rear). Also Trevor's clamps have the same "Slot" sizes as mine.
Are mine a matched pair? Are they the correct ones for a 51, A10? Why is the grease nipple on my near side clamp mounted on the rear? If they are correct, why is the near side "slot" longer than the off side?
Cheers Russ
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Hey Russ
Just been out to have a look at mine, which both have the grease nipple on the rear of the casting but the slot n the drive side casting is a 1/2" longer than the timing side.
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Someone will be along in a minute to explain the grease nipples.
Curious; are you leaving the springs and covers like that?
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Thanks Minto. Perhaps they all have a longer slot on the drive side for some reason?
No Greybeard I am not leaving them this way. I am just setting them up to ensure all is well before final painting.
Thanks Guys
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My 51 A10 plunger has both grease nipples on the side. Of course no clue if this are still the original parts.
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Hi Russ, pretty sure they all have the longer slot on the drive side.
I have a spare ‘off side’ one with the nip out the back if you want it to match, mate.
I’ll try for a photo, but the phone camera files are normally too large.
Cheers Thomas.
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I don't have the exact year, but the nipple position was changed from side to rear after a couple of years. I imagine side nipples were getting kicked off or were damaging footwear. My 1955 machine has rear-facing nips.
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Mine has the outward facing nips and they also can damage shins. I can personally vouch for the fact that it hurts too.. *sad2*
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Mine has the outward facing nips and they also can damage shins. I can personally vouch for the fact that it hurts too.. *sad2*
If they are a problem I think you could remove them and put small screws in. Put them back in only to regrease.
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Russ, I'm glad you posted this, I've always wondered about the reason I have such a massive difference in the amount of adjustment in the chain tensioner screws either side of my bike to get the wheels aligned, I thought that the frame might have been distorted from pulling a chair for years. I think this might be the answer.
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Would like to know; are these sort of items cast steel, (I know they would not be cast iron), or are they forgings?
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GB, I don’t know for sure what BSA’s engineers chose but from my own involvement in metalworking/ automotive manufacturing I would say likely to be ductile iron castings as these are cheaper, lighter and easier to produce than cast steel. The main drawback with ductile iron would be its poor weldability but if these lugs are brazed into the frame tubes then no problem. Ductile iron castings mechanical properties compare well with steel in most respects and can also be further heat treated as required. Steel forging would be the best choice for highly stressed, major safety related items and can be welded if required but are significantly more expensive and difficult to produce. The issue is not so much the raw materials which are essentially similar but forgings require significant additional processing, heating and higher temps so added time and energy costs. In addition added machining costs, difficulty and time again. As I said though I have no knowledge of what choices BSA themselves made in this regard maybe someone on here can enlighten us as it is an interesting subject and a good question.
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If they are a problem I think you could remove them and put small screws in. Put them back in only to regrease.
What, and suffer abuse from the mythical rivet-counters? As with most painful things, you learn not to do it after the first time..(well, other than marriage, anyway..) ;)
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As Greybeard said it appears the 51 year had the nips on the side and were changed to the rear about 53. Trevor is currently searching for his original early parts book to confirm this.
It appears I have a 53 near side and a 51 off side. Thomas thanks for the offer but Trevor had generously offered to swap me one with side nipple. I am sure they are both identical, except for the position of the nipple. I just like the idea of having the correct part for the year.
Thanks for everyone's input.
Cheers Russ
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Mines a 52 but has them rear facing, of course though they may have been replaced with later parts.
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Yes, the early plunger model has nipples on the side to grease anyone passing. Later versions '52/53 have nipples to the rear. For the application here I would rule out a simple casting and surmise them to be forgings, which are the same for all years, differing only in the position of the drillings for the grease nipples. The spindle slot lengths are different on each side. The chain side positions the hub to tension the final drive chain. The slot on the other side then allows plenty of leeway to centre the wheel. From experience it takes several goes to get it right. If greasing passers by is a problem, substitute the nipples for blanking plugs and teach critics a few new words, about going away and multiplying.
As for setting up, anyone capable of tuning a guitar from scratch will have no problem, its the same principle. Chain tension and alignment and wheel centralisation are all inter-related, just like guitar strings....perfect tuning until you re-check that bottom E. Then round you go again.
Part numbers. 67-4125. Nearside, brake drum side.
67-4126. Offside, right hand side.
On these carriers, Grease Nipples face to the rear, info taken from October 1953 parts catalogue.
Swarfy.