Steering head bearings (2013)

Tintin · Feb 21, 2013

L.A.B. said:
40 Nm or 4 Nm, the tab washer would prevent the nut from loosening....wouldn't it?

A thread fixation needs a certain tightening torque which is specified by the designer in order to fulfill what he intended. So IMHO a 4Nm tightening torque is already loose. A tab washer prevents the nut from rotating but not really from loosening.

Do you have any actual evidence the nut will come loose unless tightened to the listed torque figure?

Do you honestly question this? Sorry, but that's rather pointless. There is a sh*tload of evidence for this fact probably back from the days when threads were invented. A nut with insufficient pre-load will come loose. A tab washer is a loss-prevention device and not intended to maintain clamping forces. A threaded fixation loses a lot of clamping force by very, very little rotation, less than the inevitable backslash of a tab washer. If you don't believe me just go the next place were they teach mechanical engineering.

Apparently, a locknut (counter nut) according to you, would be a suitable 'engineering' solution, yet a tab washer is not?

Do you understand the fundamental difference between a locknut and a tab washer regarding the contact forces at the thread and at the contact faces between the adjacent parts and what that means for maintaing a proper pre-load? If you do then the question is rather odd. If you don't then the answer is simply yes.

Tim

L.A.B. · Feb 21, 2013

Tintin said:
L.A.B. said:

40 Nm or 4 Nm, the tab washer would prevent the nut from loosening....wouldn't it?

Click to expand...

A thread fixation needs a certain tightening torque which is specified by the designer in order to fulfill what he intended. So IMHO a 4Nm tightening torque is already loose.

But we are discussing this in relation to taper roller bearings in the 71-on assembly using the nut to alter preload so the actual torque figure is irrelevant.

The bearing/nut assembly would still loosen as the taper bearings wore, and a locknut in place of the tab washer won't prevent that.

Tintin said:
Do you have any actual evidence the nut will come loose unless tightened to the listed torque figure?

Click to expand...

Do you honestly question this? Sorry, but that's rather pointless. There is a sh*tload of evidence for this fact probably back from the days when threads were invented. A nut with insufficient pre-load will come loose.

Basically what you are saying is that any fastener not tightened to the manufacturer's torque figure will loosen which, certainly after many years of tightening fasteners I've never found to be true.

B.Rad · Feb 21, 2013

hello All.

vigorous debate this one hey. A request for bearing numbers has drifted into 2 pages now about the science of clamping forces. reminds me of the recent thread about perambulators and perambulation. I thought perambulations were something freemasons did.

I say again Pommy John, and Mr LAB sound like practical people . Racing people seem to know what does not work real quick.

Tintin, this is not the space shuttle. You dont need a spacer on tapered roller bearings, (front wheel bearings on cars), if you use balls you need a spacer. the length of this spacer may be in microns but this is overkill. Not all have access to surface grinders or do you grind by hand. I have made tab washers of a very complicated design for turbines whose sole purpose is to keep the nut tight. not to stop loss of the part.

My experience in working with design engineers or draughtsmen (there is a difference) i find that sometimes (regularly) the the design tolerances are too tight for achievable shop production. gearing is a good example, especially if the tolerances were applied by a computer program.

Well thats my 2 bob worth. This could go on forever. It is a storm in a teacup

I am going back for a look at a real interesting subject, what Comnoz did to the fullauto head. Now there is practical achievement of the highest order and requiring some design to get it right .. No second chances with that kind of work.. That kind of work I find fascinating. Beyond my ability though.

Kind regards to everyone
Bradley

Tintin · Feb 21, 2013

L.A.B. said:
But we are discussing this in relation to taper roller bearings in the 71-on assembly using the nut to alter preload so the actual torque figure is irrelevant.

No, it isn't. In order to stay tight under certain load conditions there is a certain torque figure - depending e.g. very much on thread pitch. Up to 1970 it is 28TPI, 1971 onwards it is 14TPI. What a coincidence..... If you abuse a clamping nut for adjusting you completely ignore this. If you fail to implement alternative countermeasures the nut will alter its position under the applied load-case and therefore drastically alter its pre-load, the more coarse the larger this effect will be. What were the TPI figures? If your countermeasure is a tab washer this effect will be less than witout any device but with a locknut or a spacer it will be far less than with a tab washer.

The bearing/nut assembly would still loosen as the taper bearings wore, and a locknut in place of the tab washer won't prevent that.

"Wear" is happening in all setups and under normal circumstances far slower than "settlement".... :roll:

Basically what you are saying is that any fastener not tightened to the manufacturer's torque figure will loosen which, certainly after many years of tightening fasteners I've never found to be true.

Sorry, But I'll leave the hair splitting to you if you don't mind. If a nut is insufficiently tightened it will come lose. Period. How far of the manufacturer's numbers are from this in each and every case I really don't care. If 40Nm is specified 4Nm is way off. From my many years of engineering on all kinds of vehicle systems I find this very much to be true.

As this discussion feels as friutless as the "last vs. latest Commando" thingie it's EOD4me now. Just replacing the BBs with TRBs and using the tab washer might work but is bad engineering practise. A locknut or a spacer are far superior. If you disagree I simply don't care, sorry.

Tim

Tintin · Feb 21, 2013

B.Rad said:
Racing people seem to know what does not work real quick.

:mrgreen: Thanks! You know what I do for a living? Oh, it's not space shuttles.

You dont need a spacer on tapered roller bearings, (front wheel bearings on cars),

Funny, the last few cars I had a closer look at had ACRB with a spacer for wheel bearings.

if you use balls you need a spacer.

For a completely different reason and with a completly different design idea behind.

the length of this spacer may be in microns but this is overkill.

I think you got me wrong there. I did not say "machine this to that length plusminus a few microns", I said that the correct preload will be within a few microns. The softer the "spring" the larger the tolerance.

Tim

L.A.B. · Feb 21, 2013

Tintin said:
L.A.B. said:

But we are discussing this in relation to taper roller bearings in the 71-on assembly using the nut to alter preload so the actual torque figure is irrelevant.

Click to expand...

No, it isn't. In order to stay tight under certain load conditions there is a certain torque figure

Which again, as the intention is to preload taper roller bearings with no spacer between the bearings the torque figure is still basically irrelevant.

Tintin said:
If 40Nm is specified 4Nm is way off.

I think perhaps you missed my point, what I meant was that when the nut is used to preload taper roller bearings (no spacer) then the torque required is likely to be less than the standard amount, I didn't actually mean "4Nm" only as an example that the tab washer would still perform exactly the same function as it does with the standard ball bearing and spacer setup.

Tintin said:
Basically what you are saying is that any fastener not tightened to the manufacturer's torque figure will loosen which, certainly after many years of tightening fasteners I've never found to be true.

Click to expand...

Sorry, But I'll leave the hair splitting to you if you don't mind. If a nut is insufficiently tightened it will come lose.

I suggest you try putting the 'book' down and start using some spanners for a change, it may alter your opinion?

Tintin said:
Just replacing the BBs with TRBs and using the tab washer might work but is bad engineering practise.

It does work, as I expect a number of our membership have already proved, perhaps it's not good engineering but is a workable arrangement.

Tintin said:
A locknut or a spacer are far superior. If you disagree I simply don't care, sorry.

I know you won't care, but yes, oddly enough, I don't entirely agree.

Edit:

Tintin said:
Apart from the point that the manual states 40Nm for this nut plus the tab washer?

In the Front Forks/Steering section of the factory manual, it states that the stem nut should be tightened to: "15 lb/ft (207 kg/m)" so 20.4 Nm. and then tabbed with the washer.

Dkt26 · Feb 21, 2013

I suggest you try putting the 'book' down and start using some spanners for a change, it may alter your opinion?

I know you won't care, but yes, oddly enough, I don't entirely agree.

[/quote]

Ouch!! Tintin, you need some ice for that burn???

MikeG · Feb 21, 2013

ludwig said:
I know that in some Mercedes rear axles ( differentials ) a compressible spacer is used , a kind of tube with a bulge in the middle . the nut has to be tightened to a specific value to get the correct preload on the tapered bearings . The spacer can only be used once .
A little too much torque and you can start all over again , with a new spacer tube ..

Otherwise known as a crush collar-lots of US built cars use em as well.

Back to my original question and findings.....Why would the old lower bearing show such wear and none on the upper?
Just curious.

L.A.B. · Feb 21, 2013

MikeG said:
Back to my original question and findings.....Why would the old lower bearing show such wear and none on the upper?
Just curious.

Corrosion?

Although sealed, there's probably more chance of water getting into the lower bearing.

L.A.B. · Feb 21, 2013

ludwig said:
L.A.B. said:

..It does work, as I expect a number of our membership have already proved, perhaps it's not good engineering but is a workable arrangement..

Click to expand...

Maybe ok for a 100 mls a year bike ?.
The loose nut will wear the threads and preload will be lost soon enough .
I for one would not do any serious milage with that kind of ' arrangement ' ..

What "loose" nut?

If the nut is used to preload the taper roller bearings (and then tabbed) it must obviously remain at least moderately tight while there is some preload on the bearings.

For the "adjuster" nut to become loose, all preload would have to be removed from the taper roller bearings, therefore the bearings would also be loose, which I expect the rider would notice.

Tintin · Feb 22, 2013

Dkt26 said:
Ouch!! Tintin, you need some ice for that burn???

Burn? Which burn? You mean the most lame and oldest attempt of an insult known to any engineer? IMHO there is proper craftsmen, technicians and engineers on one side and bodgers on the other. TRBs with the original coarse thread nut and a tab washer is a bodge job. So how could I be insulted? :twisted:

Tim

Chris · Feb 22, 2013

Hi

I agree with Tintin. Could I achieve the levels he does? Probably not.
Then again, I now only use tapers 3205 on my featherbeds & on standard bearings on my Commandos.
Practical & easy are the two reasons. Tapers for the featherbeds cause I couldnt stand dropping the balls all over the garage & standard set up for the Commando because I couldnt tell the difference & the standard bearings were a lot cheaper.

Chris

Tintin · Feb 22, 2013

Chris said:
Could I achieve the levels he does? Probably not.

On a Norton, yes you could. Easily. I am really not talking about space age technology. In this example all you'd need is a tube, be able to grind it with a certain rectangularity and some patience. Insert the TRBs, measure the distance of the rings, figure out the length plus a few hundreths - and then it will be a few iterations of installing it, feeling the play, grinding the tube, installing it etc. I've used this kind of solution maybe three or four times in new designs I did - not Norton related - and it went without saying that the mechanic who had to install my designs went through exactly this procedure to dial-in bearing pre-load via grinding the spacer. It was completely self-evident for them to do so as it was self-evident for me to rely on their experience and knowledge. This is something well within the reach of anybody who has average metal-working skills and is able to work methodologically and systematically. It could even be done with a hacksaw, a file and a good square.

Tim

L.A.B. · Feb 22, 2013

ludwig said:
L.A.B. said:

What "loose" nut?
.

Click to expand...

Maybe you should do some reading up about the fysics behind nuts and bolts .
' Elasticity' is a key word .
You can start here :
http://www.boltscience.com/

Read it, years ago, thanks.

Elasticity' is a key word

Indeed it is, and if someone were to do the calculation, I think they may discover the torque figure required to prevent that nut from 'self-loosening' would be far higher than 15 ft.lb/20Nm (or even 30 ft lb/40Nm) stated in the manual.

http://www.boltscience.com/pages/twonuts.htm

Seems to show that a locknut is not always as effective as some would have us believe.

marinatlas · Feb 22, 2013

Hi, about the TRB , should the spacer rest on the inner part or the outer part ......?

Tintin · Feb 22, 2013

L.A.B. said:
Seems to show that a locknut is not always as effective as some would have us believe.

If you knew what you were talking about you would have been able to understand why your "evidence" is completely useless to prove your point here. But from what I've learned here you apparently do not know what your are talking about and the ability to use a spanner obviously is not a sufficient proof of understanding how threads work in detail. This is so pointless I am really amazed by the grade of pointlessness.

Tim

Tintin · Feb 22, 2013

marinatlas said:
Hi, about the TRB , should the spacer rest on the inner part or the outer part ......?

The inner races so the inner dia of the spacer is (slightly bigger than) the outer dia of the stem. The outer races are positioned in the headstock so the spacer takes the majority of the clamping force when the nut is tightened. The idea of the spacer is to have a high clamping force together with low pre-load. Without the spacer either the load on the bearings gets to high or the load on the thread to low.

Tim

L.A.B. · Feb 22, 2013

Tintin said:
If you knew what you were talking about you would have been able to understand why your "evidence" is completely useless to prove your point here. But from what I've learned here you apparently do not know what your are talking about and the ability to use a spanner obviously is not a sufficient proof of understanding how threads work in detail.This is so pointless I am really amazed by the grade of pointlessness.

Oh well, I think will continue to not know what I'm talking about and carry on using the tab washer. :wink:

rpatton · Feb 22, 2013

MikeG said:
Back to my original question and findings.....Why would the old lower bearing show such wear and none on the upper?
Just curious.

Because the lower bearing takes all of the axial load. The upper bearing floats, just see's radial forces.

MikeG · Feb 22, 2013

Thank You!!!!!

But it has been entertaining, and educational too.
MikeG

Steering head bearings (2013)

Tintin

L.A.B.

Moderator

B.Rad

Tintin

Tintin

L.A.B.

Moderator

Dkt26

MikeG

L.A.B.

Moderator

L.A.B.

Moderator

Tintin

Chris

Tintin

L.A.B.

Moderator

marinatlas

Tintin

Tintin

L.A.B.

Moderator

rpatton

MikeG