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Chain adjustment question


Hello Folks

I have a question about chain adjustment. I'm about to put a new chain and poss. rear sprocket on my Bike and have come across a few difficulties. I'm trying to follow service sheet 609 and it seems the fixings/bolts described aren't the same as on my M20 although the quality of the drawings in that sheet are pretty poor and difficult to distinguish parts clearly.

The drawings suggest i have a nut on the offside end of the axle. It seems like i have an axle with a square shaped end, is this normal? On the nearside the doc suggests there should be 2 nuts; 1 to unlock the cam adjuster and 1 to rotate the cam. I seem to only have 1 weird shaped or worn nut.

I'd appreciate if anyone could look at the 3 pics to see if this looks normal or if something is missing/wrong. I undid that locknut OK but the square section bolted on the offside is very tight. Once the nearside nut is undone should tat be free or does that screw into something as well? I don't want to start giving that square thing abuse when i should be doing something else. The small offset adjusting screw and locknut came away easily and is free and not touching the axle.

PXL-20220402-170503374
PXL-20220402-170427277
PXL-20220402-170356224

cheers

Neil

email (option): nlhclarke@gmail.com

Re: Chain adjustment question

That doesn't look like a WM20 frame and wheel. This is what an M series hub should be like. Ron

Scan-rear-hub

email (option): ronpier@talk21.com

Re: Chain adjustment question

Neil,

Your wheel fitted is a later crinkle hub type which i don't think were fitted to rigid frames. It may have the rigid brake plate but i cannot tell from your pictures. The frame is a sidecar frame with the cast lugs at each side. Could be post war frame or one from a RAF contract, what year is your frame?

Re: Chain adjustment question

Hello Tim

That connects with a comment made I previous owner who said it had a side car and was removed and disposed of years ago. It is a 1947/8 model. I have frame and engine numbers somewhere, I believe that you can look such things up.

Do think this crinckle hub is consistent with these years? It is a rigid frame alright.

Cheers
Neil

email (option): nlhclarke@gmail.com

Re: Chain adjustment question

Neil,

I'm no expert on these crinkle hubs but i thought they were used with the plunger frames not the rigid frame. Your frame is the same as my XM20 frame with the cast sidecar lugs so it sounds like your frame year is correct. The rigid wheel hub and spindles are as Ron posted and its completely different to your crinkle hub. I can also see you have some kind of cranked brake plate anchor which is incorrect.

Re: Chain adjustment question

Just for interest sake, since you mentioned the RAF Tim. The wartime sidecar frames have the rear lug on the left side only. Ron

email (option): ronpier@talk21.com

Re: Chain adjustment question

Noted, thank you Ron.

Re: Chain adjustment question

Crinkle hubs were used on plunger and swinging arm frames for various models but not on rigid frames..There are some differences between the various types...I fitted one to my rigid B33 and retained the original brake plate from the rigid wheel..From your photos it appears that is not the case with your bike as a torque arm is visible...Ian

email (option): ian@wright52.plus.com

Re: Chain adjustment question

Hello Folks

I thought I'd upload a few more pics that might help identify my rear hub/sprocket arrangement for certain, although it sounds like it is the 'crinkle hub' type. Yet again this bike seems to veer away from what would be a standard. This might explain why I needed a 3/8" chain rather than the standard 1/4"

The brake plate seems to have a few holes cut into it which look a bit odd as seem to expose the brake shoe 'cavity' to the elements?

The sprocket has 46 teeth which i believe is standard not the sidecar 49T one

PXL-20220405-162328516

PXL-20220405-162241909

PXL-20220405-162044933

PXL-20220405-161703058

PXL-20220405-161650063

The axle nut is also pretty worn and I need to get a new one so I can tighten it securely, can anyone tell me what size thread that is on the shaft, I presume it is a Whitworth or AF type? I'm not that familiar with imperial measurements.

Also the drive side bearing is pretty rough and needs changing. Would this bearing be relatively standard (I hesitate to use that word !) on M20 hubs?


Cheers
Neil

email (option): nlhclarke@gmail.com

Re: Chain adjustment question

Neil I think you will need to ID the hub before looking for parts. Drags show exploded diagrams of all the hubs. Yours looks like a none complete/standard version of this to me?

https://draganfly.co.uk/product-category/bsa/sparesparts-for-bsa-a710-b3133-c101112-m202133/wheels-abcm/rear-wheel-abcm/11-splined-rear-hub-1949-55-plunger-swinging-arm-abm/

Can I ask what the small glass bottle is for? Oil catch? Ron

email (option): ronpier@talk21.com

Re: Chain adjustment question

It looks like a swinging arm crinkle hub wheel from a 1954 onwards A7/A10...They had the wider 3/8" chain whereas the singles had the narrower one..The brake plate and some other parts have been modified...(the brake plate possibly for previous use on a plunger model...) Frankly, it all looks a bit of a 'lash up' and either it should be modified to fit and function correctly or better, be replaced with the correct set up...

Before considering returning to a standard set up check to determine whether the width of the rear frame forks have been modified...Ian

email (option): ian@wright52.plus.com

Re: Chain adjustment question

Thanks for then replies folks !. I think 'lash up' is putting it very politely, I could think of a few other choice phrases! What with my non-standard carb as well, I'm expecting to find a good few more. I suppose that is part of the entertainment we get from these projects.

Although it would be good to get it back to standard it looks like getting a whole new wheel/brake complete etc would be the simplest way to go. Seeing i have just got a new chain and it fits nice and snug to my wheel sprocket, I'm inclined to keep it this way for a bit or until I come across the correct parts at a bargain price.

On subject of converting to standard, I was going to check fork gap to see if the frame dimensions are as on that service sheet 710. However the gap is very difficult to read on my copy. It is not symmetrical and comprised of 4" drive side plus 3 and ?/12" on non drive side but cant read the fraction to get the proper gap !! Do you happen to know what the correct fork gap is?

Ron, that little glass bottle appears connected to a crankcase pipe; probably the breather? Again, is this a common feature or another example of my rogue vehicle ?

cheers
Neil

email (option): nlhclarke@gmail.com

Re: Chain adjustment question

I was referring to the gap where the wheel spindle fits through the frame...It's not unheard of for that to be altered on one or both sides when an alternative wheel spindle to the standard one is used...Ian

email (option): ian@wright52.plus.com

Re: Chain adjustment question

The frame spec is here Neil. http://www.wdbsa.nl/BSA%20frame%20alignment%20tool.htm

The glass bottle is not normal but I have seen oil mist collect receptacles before, even a Coke can. Ron

email (option): ronpier@talk21.com

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