I have,what may be,a very rare possibly unheard of situation with my 67 hornet crank! I am at present testing for end float after spending a small fortune getting to this point. Ive had a dummy bearing made up to the precise dimensions of the roller with the exception of the bore which allows the crank to slide thus mimicking the movement of the roller cage. Well thats the theory anyway! It works very well in practice with everything tightened and level etc it gives a reading of 18thou. Thats no shim cup or shims! My new shim cup measures 33thou and the originals were 25thou im told. So you seei have a problem in that i wouldn't be able to fit one in! Any one heard of such a conundrum? Would i be ok running without, and using thicker shims and getting as close as i can? Any advice gratefully recieved. Thanks Dave.
Sounds dodgy to me. Maybe you need referring to AC12?
;)
AC 12? Thought that was to do with dodgy coppers!
:) :) :) :)
With the shim cup and correct shims Done by the manual method. My engine was absolutely solid.
So I left the shim cup out. Its running fine but whether it was a good decision or not????????????
I've just put a non original crank into a second engine and even without shims it locked up tight. I sent it to SRM and they machined a couple of thou off the timing side flange of the crank. I meant to take a pic but forgot. Turns beautifully.
Don't know if this helps.
Mike 8) 8) 8) 8)
Thanks Mike for the info. It just goes to show every ones different! Its one never ending learning curve. ???
:) :) :)
Something that I forget is that I put extra shims in to take up the "slack" when I didn't fit the cup.
Mike 8) 8) 8)
Hi,
I am not too sure of the details but there are differences between early and late cranks to do with timing side thrust washers and the change from ball to roller mains.
I think it is that the earlier cranks to not fit straight in later cases but later cranks can be used in earlier cases without machining. Shimming still necessary though.
Dave.
:) :) :) :)
I understand that to be the situation as well. I intend to get in touch with SRM in the next couple of days and have a general chat about this these points. As well as this discussion I'm not really sure whether shims are needed if you fit a roller bearing on the drive side etc.
Something else comes to mind. At some stage BSA changed the normal ball bearing for one on which the OD of the inner boss is increased. I THINK that the shim cups won't go properly over the larger boss, that in truth is probably what caused my earlier problem.
Smile, either that or cry.
Mike 8) 8) 8) 8)
a very easy solution is to make a shim and place it under the bearing outer in the casing.unfortunately there is always someone who is against the idea and knows best.
Hi,
I think there was thread on the Forum a while ago about cranks and the changes made.
It is my understanding that unless you have the needle roller timing side conversion shims are still need to control the end float. Even with the conversion it could still be necessary to have a shim to ensure the full engagement of the main bearing rollers in their track. I have seen modifications whereby the crank is locked to the drive side using an out rigger bearing but that looks quite complicated.
When the change was made from ball to roller main bearing I believe that the crank journal remained the same but the crank overall was reduced in width to accommodate the timing side thrust washer.
Shimming under the main bearing outer race sounds like a viable alternative. The only problem I can see is that if there is a bit of trial and error getting the shimming right then the outer race needs to be removed several times and this is not really ideal in an aluminium housing. The crank is far more robust for this. Also, if quite a thick shim is needed the outer race will be held slightly proud of the case. Would this leave a small part of the bearing unsupported by the case and potentially prone to
stress and cracking?
Dave.
Wait, your shim cup is 33 thousands? No.
The way the shim cup fits it seats on the bearing inner so it's whole width is not applied to your needed end float.
Only the thickness on the shim cup metal itself will factor into the float.
Then BSA offered 3,5 and 10 thousand shims that fit inside the cup as needed to result in 1.5 -3 thousand end float if I remember correctly.
Don't get cute and shoot for less float than that. You will have problems.
The cup is not actually required but the crank has a radius so if you buy shims elsewhere they have to have an inner diameter larger than the radius.
Without the cup though, the shims may kind of shift around and not be ideal.
I think I discovered three but at least two different shim cup sizes fitting different bearings inners so check with your vendor.
Wondered if someone might think that! Im aware how the cup fits and what it's purpose is. I can assure you the actual metal thickness is .033 the overall depth very much more! I checkedwith SRM and they were a little surprised as the originals should be around 25 thou. Still to much to sort my problem. Thanks to all for your thoughts and suggestions. Dave
Hi All,
Have a read of this. It may make things clearer or perhaps not.
https://www.classicbritishspares.com/blogs/news/early-vs-late-cranks
Dave.
Quote from: Dibble on 29 Apr, 2021, 08:34
Wondered if someone might think that! Im aware how the cup fits and what it's purpose is. I can assure you the actual metal thickness is .033 the overall depth very much more! I checkedwith SRM and they were a little surprised as the originals should be around 25 thou. Still to much to sort my problem. Thanks to all for your thoughts and suggestions. Dave
So the cup came from SRM ? Maybe ask around at other vendors. Mine was 18 thou. Maybe you'll find one you can use alone with no shims to make up your float.
I had an early crank and late cases along with other anomalies and need to shim 60 thou worth. I skipped the shim cup.
No the cup came from another well known supplier. Theres one thing if ever i get round to actually using it, should last a while! ;D
Right! You could file/grind/sand it down to the size you need?