Author Topic: Crankshaft side play/shims etc  (Read 3957 times)

Offline BSA500

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Re: Crankshaft side play/shims etc
« Reply #60 on: 26.11. 2015 09:11 »
Just my experience, but every time my shims have been destroyed the cush nut was NOT loose. It has never come loose EVER. Not sure where that leaves me  *sad2*. I shall be trying the loctite and getting the play down to 1 thou to give me fighting chance.

Offline chaterlea25

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Re: Crankshaft side play/shims etc
« Reply #61 on: 26.11. 2015 20:11 »
Hi All,
Guys !!!
If the shims break up and fall to the sump, then the cush drive nut is no longer clamping the bearing inner  *ex*

Suppose BSA500 loses his 29-3 =26 thou of shims, then the cush drive sleeve/spacer/ bearing inner combination
is shorter by 26 thou therefore the nut is loose by the amount of lost shims

If I could not afford to have the crank repaired
I would fit the shims between the bearing outer and crankcase instead

John
1961 Super Rocket
1963 RGS (ongoing)

Online bsa-bill

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Re: Crankshaft side play/shims etc
« Reply #62 on: 26.11. 2015 22:05 »
Quote
I would fit the shims between the bearing outer and crankcase instead

these would have to be shims the size of the bearing outer not the inner , is that right
All the best - Bill
1961 Flash - stock, reliable, steady, fantastic for shopping
1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

Offline chaterlea25

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Re: Crankshaft side play/shims etc
« Reply #63 on: 26.11. 2015 23:05 »
HI Bill
Quote
these would have to be shims the size of the bearing outer not the inner , is that right

Yes.

John
1961 Super Rocket
1963 RGS (ongoing)

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Re: Crankshaft side play/shims etc
« Reply #64 on: 27.11. 2015 00:44 »
I'm going to throw in a BUT here.
The shims in their proper position are (supposed to) held tight by the cush nut. If placed between the outer race and the crankcase the only thing holding is the fit of the outer in the case. I've seen more loose outers than inners.  *dunno*
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
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Re: Crankshaft side play/shims etc
« Reply #65 on: 27.11. 2015 01:01 »

 I've had timeout due to data blowout, but sneaking in a looksee here and there...

 A couple of things to note;

 BSA 500 hasn't lost shims on this excursion, that was the previous one (1500miles ago)...
   I had a thought that maybe the shim got caught up on the radius of the journal/web and then dislodged (maybe that's been suggested); I set mine vertical with the web supported on a 'bench', that way I figured it has a better chance of staying concentric.

  I'm also presuming that the raised 'landing for the bearing inner is intact...?  I discovered mine to be worn below the web due to a slipping inner, to the point where I also discovered I'd also had to machine the journal (~29mm) and add a thin sleeve with matching radius, which seems ok after ~9000 miles. I had to add extra shim to bring the worn web back to positive. (Cranks were/are scarce in my part of the world too!)
 With regard to the inner slipping on the journal(which may not be relevant here), I had a thought that if the journal/web radius matched the radius on the bearing inner, it should help hold it concentric.
 
  With shims behind the outer, would be essential to ensure they seat properly in the case of a radius in the housing, which could change the dynamics. I considered shims in there would set the outer closer to the web, but just had a look at a used bearing, and it seems to have plenty difference between inner and outer faces, so should not be an issue anyway

 aaah, Musky rounded me up...and like he and others say, the nut should hold them tight, and even if it does come loose, it should only go as far as the split-pin and still have spring tension on it (not ideal- especially if the spring breaks like mine did), and I can't see why the friction of the rollers would be greater than the friction of the assembly

  Stuff to doo...
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline East_Coast_BSA

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Re: Crankshaft side play/shims etc
« Reply #66 on: 27.11. 2015 02:38 »
aaah, Musky rounded me up...and like he and others say, the nut should hold them tight, and even if it does come loose, it should only go as far as the split-pin and still have spring tension on it (not ideal- especially if the spring breaks like mine did), and I can't see why the friction of the rollers would be greater than the friction of the assembly

  Stuff to doo...

The spring doesn't hold pressure on the race, the spring holds pressure on the sprocket.  It's outside of the assembly being torqued.  The nut bottoms out on the spline sleeve, that's what provides the pressure to the inner race.  It's all stacked up on the crank and the nut compresses everything.  You are torquing a solid stack of components.   

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Re: Crankshaft side play/shims etc
« Reply #67 on: 27.11. 2015 20:46 »

 Yes E_C_B, I know that, but what I mean is there is spring tension on the sliding-bush/cam which in turn pushes on the sprocket which pushes on the collar of the inner sleeve and then the bearing inner race (not ideal).

 I wrote it as an afterthought bubble 'cos Musky posted while I was writing.
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Online RichardL

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Re: Crankshaft side play/shims etc
« Reply #68 on: 03.08. 2018 17:02 »
Almost shy to ask a shim question here, having read so much on it, written so much on it, and been given so much good advice. Nonetheless, I don't recall this question being asked by me or anyone else, and if it has, there is too much info to sift through to find it. 

Question is: Should we target an allowance for the minimum amount of side play before installing shims? I want to tell my machinist to dress the face of the new T.S. bushing so the crank is not locked up when the cases are assembled. I don't think it would be good if the play (without shims) was, say, 0.004".  That would mean the shim (or shim stack) might be just 2-3 thou thick. Arguments for specially machined thick shims seem to support the notion that such a thin shim, by itself, is a recipe for shim destruction. ("Well, Richard, if you get your bearing on right, tight to the web and with the shim sandwiched between and (maybe) Loctited, the shim should be fine, you dummy."  Then I say, "Well, yes it should, so why bother with custom-made thick shims?")

Any thoughts?

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline chaterlea25

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Re: Crankshaft side play/shims etc
« Reply #69 on: 03.08. 2018 18:54 »
Hi Richard
Assuming the machinist is going to make a new bush from the "solid"
The casing bores are very often gone "out of round" and oversize leading to oil leakage between the bush and case
if a "bought" bush is used
If the machinist assembles the crank and drive side bearing without shims into the drive side case
it should not be too difficult to measure the thickness needed on the flange of the timing side bush to (at first ) give negative  endfloat, then skim the bush face to .000-003end float
If the machinist is very confident that they could hit zero endfloat they could machine the bush flange to that thickness
before fitting

That would be the absolute best engineering solution (blueprinting) and no shims required

John
1961 Super Rocket
1963 RGS (ongoing)

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Re: Crankshaft side play/shims etc
« Reply #70 on: 03.08. 2018 22:05 »
G'day Richard, John.
My thinking would be to give it 1 to 1.5 thou endfloat to allow oil to lubricate the thrust faces.
I'll be doing this on the A7 rebuild (when I get a roundtuit).
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7

Offline chaterlea25

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Re: Crankshaft side play/shims etc
« Reply #71 on: 03.08. 2018 22:09 »
Here ya go
1961 Super Rocket
1963 RGS (ongoing)

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Re: Crankshaft side play/shims etc
« Reply #72 on: 04.08. 2018 04:24 »
I have a sense that asking the machinist to take on perfect crankshaft endplay without shims would lead to quite a lot of extra cost from that machinist.

Back to my original question: if you must use shims, what minimum thickness would you choose for shim stability?

I'm going to remove the old bush and measure ovality.  If it's a problem I'll have to return my phosphor bronze part and see about getting one with an oversized OD, or having one made. I have neither the lathe nor the skills.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

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Re: Crankshaft side play/shims etc
« Reply #73 on: 04.08. 2018 05:14 »
G'day Richard.
The thinnest shim I have is 1.5 thou and would be happy to use that as long as the bearing is snug on the shaft and the cush nut is done up correctly. Once we get into big #'s (20+) I'd suspect something not right. A single shim is preferable to a stack but IF assembled dry and correct a stack will work fine.
Yes a lot of extra $$$ to make a bush with the thrust face a measured thickness. If the case is out of round a bush will need to be made anyway (I don't know of oversize off the shelf).
Another way of thinking is the motor was designed with a bush thrust thickness of a certain thickness. Everything revolves around this. OK the thrust face will wear over time (amount depends on time/lubrication) or the crank grinder may face the thrust surface of the crank. If we're only talking a few thou it can be taken up on the bearing side.
Check the case. If OK throw the new bush in and shim as we have done for 60+ years.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7

Offline coater87

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Re: Crankshaft side play/shims etc
« Reply #74 on: 04.08. 2018 12:04 »
 Richard,

 I know a lot of machinists.

 Explain to him everything you know you need out of the set-up, what numbers would be perfect, dont tell him how to do it, and then let him go.

 These guys get bored to tears cutting the same parts over and over and over.

 Your project could be an exciting challenge to the guy. In the least its a break from cutting air over hydraulic solenoid adapter plates or automatic dog food dispenser door hinges *smiley4*

 Lee
Central Wisconsin in the U.S.