Lotus Elan

Does heating hub damage rear bearings?

PostPost by: simonknee » Mon Jun 14, 2010 8:26 am

Hi all,

Since I was 1000+ miles I went on a long shake-down run to Devon and back this weekend. It was moderately eventful but the main issue as I came back into London last night was a cyclical rubbing noise from the rear left. It did not diminish with braking. Was mainly noticable as you slow down to a junction. I was repeating at once per wheel revolution. It was late so I just put the car in garage last night and fell asleep watching F1 on iPlayer.

This winter I re-did the whole rear with Spyder CV/donut system. This included sending the hub carriers to Spyder to fit the new axles (Kelvedon hi-spec jobs) and bearings. My tools and I were only just up to removing the hubs. The axles I could not.

Unfortunately I reassembled using coppa-slip. This resulted in an annoying creak from the hubs. The cause of this is cavitation as the moving grease causes a vacuum (well known from bicycle cranks but I was not thinking). Spyder advised to take off, remove grease and valve-grind the stub and hub. However I could not get the rear left hub off again. Using a small Sealy Hydraulic puller (I'm bolt-on wheels not spinners) and applying heat from a butane torch just made the coppa slip bubble out a bit. I tourqued the hub nut back to 100lb/ft and squeak went away.

So now after a 1250 miles I have a troublesome cyclical noise. Could the heat that 5 minutes with butane can apply have damaged the bearings? Any other thoughts/wisdom on the matter?

I will be investigating further this evening...
Simon
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PostPost by: richardcox_lotus » Mon Jun 14, 2010 1:01 pm

Before pulling apart things have you jacked the rear of the car up & manually spun a wheel ?
My Sprint sometimes get a noise - from my Handbrake pad rubbing.

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PostPost by: GrUmPyBoDgEr » Mon Jun 14, 2010 1:31 pm

Please excuse me if I've misread your Post.
As I understand it:-

1. You fitted your existing Hubs to new Shafts with Coppaslip & without grinding in the Shafts to Hubs.

2. An unsuccessful attempt was made to remove the LH hub from the Shaft using heat & a puller in order to retrospectively perform the grinding in process.

So the LH Shaft & Hub have not been matched together by "grinding in"?
This must be done to assure that both surfaces match in order to transfer the driving & braking forces.
For the same reason no form of lubricant should be applied to the surfaces of the taper.
I think you must address this quickly.

Yes the heat you applied could have caused damage to the Bearing(s)
IMHO Heat should only be applied if necessary during the dismantling of old Hubs, never during assembly!
This is controversial as I know that some recommend heating the Hub prior to fitting to get
"an extra tight fit";
I consider it superfluous & could cause difficulty in removing the Hubs at a later date due to the more highly loaded "shrink fit" that has been achieved.

That could be the cause of the noise you describe but no doubt further investigation at the Weekend will point you in the right direction.

Good luck
John

PS there was a recent thread (Headed TTR------) where the subject of Hub fitting was discussed.
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PostPost by: simonknee » Mon Jun 14, 2010 2:26 pm

Please bear in mind that it is pre-emptivee post. I do hope it is the handbrake caliper or similar.

You are correct in 1. and 2. John. However if you do not heat how the hell do you get them off!
Perhaps all you knock-on folks have it easy. This job is a real b'stard with mine.

I have one of these: http://www.sealey.co.uk/PLPageBuilder.a ... uctid=7267

It's a 10tonne hub puller. Without heat it did nothing. With heat after about 5 mins the whole affair flies across your garage with a bang. Except it didn't on my new axles (only lhs tried).

I don't seem to have a problem with getting a tight fit. What has occurred is that it is not a perfect fit and the creak is the sound of cavitation in the grease. Why do I need to do this asap? What catastrophe awaits? eek!

Maybe I should drive to Spyder so they can get them off!

Simon
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PostPost by: paddy » Mon Jun 14, 2010 2:46 pm

Simon, where are you?

I got a puller from a Triumph specialist that fits the bolt-on hubs, like the big red one here: http://www.rimmerbros.co.uk/Item--i-GRID010703

One of mine had all the signs of never having been apart in 40-odd years and it took a lot to get it off - lots of force and also lots of heat. The hub, after it came off, was well in excess of 100C. Without the monster puller it would never have come apart.

Don't be gentle :)

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PostPost by: billwill » Mon Jun 14, 2010 3:37 pm

From your posting it is not clear how much assembly Syder did and how much you did and which fittings have coppaslip on them.

Did Spyder do the taper fit part of the reassembly?
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PostPost by: simonknee » Mon Jun 14, 2010 3:53 pm

Sorry for confusion, I did most of the work.

I sent Spyder the hub carriers with axles in but hubs off.
They pressed out the old axles and bearings and pressed in new ones.
They used new Kelvedon axles including milling a groove for the type 16 circlip.

I re-assembled the whole kit.
It is when putting the hubs (the things with four wheel studs in 'em) back on the tapered axles (with a locking pin) that I used coppaslip.
Unfortunately did not know about no grease and grinding the things until I spoke to Andy at Spyder after the event.

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PostPost by: gerrym » Mon Jun 14, 2010 5:04 pm

Simon, a few things to bear in mind:-

1/ the hub to axle should have been lapped together. Not sure how one would grind it. As John says, assembly should be dry
2/ should not be any great harm done, so dismantle and start again.
3/ if the bearing is gone, again no great harm but don't rush into the job just yet until there are definite signs of rumbling/roughness etc.
4/ If the taper is now so loose that its slipping on drive then it should come off no problems.

On the cavitation side of things, familiar with this on propellers and pump suctions but never heard this used to describe action of grease! Do you have any more symptoms on this

Regards

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PostPost by: billwill » Tue Jun 15, 2010 12:55 am

How is this lapping operation done?
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PostPost by: simonknee » Tue Jun 15, 2010 6:34 am

Investigated last night, easy to fix...

Erm, the other reason that you might get a nasty cyclical rubbing noise might be because you have a not so tight couple of wheel nuts :oops:

To answer a few questions in the thread...

Bearings worry over for now however i do need to sort these hubs/axles. The grinding (lapping) was advised by Spyder using valve grinding paste and rotating the hub on the axle. I have realised that I didn't copaslip the whole thing - just the locking pin. However I _will_ get them off to grind them.

My boss and I are keen cyclists and as soon as I described it to him he goes "oh that's cavitation in the grease" There was much debate in bike forums about using grease when fitting cranks (bits with pedals on the end) to bottom brackets (axle) - you can do the nut up tighter. However you get a creak as you pedal after a while. If you assembled them completely dry then there is no creak. The sound is caused by air rushing in to fill a cavity caused as the grease squirming around inside the joint.

Finally, my hubs are not loose at all, that is the problem :D . A 10 tonne press and 5 minutes of hand-held butane torch heat did not shift it. I think I shall go to somebody with a bigger press so that they can be removed without heat or a hammer. Seems a shame to knacker my brand new bearings. I have taken them off once - when I first disassembled the rear end. So I know it can be done and it did take a lot of pressure and heat. However they refuse to budge from the new axles.
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PostPost by: GrUmPyBoDgEr » Tue Jun 15, 2010 10:17 am

gerrym wrote:Simon, a few things to bear in mind:-

1/ the hub to axle should have been lapped together. Not sure how one would grind it. As John says, assembly should be dry
2/ should not be any great harm done, so dismantle and start again.
3/ if the bearing is gone, again no great harm but don't rush into the job just yet until there are definite signs of rumbling/roughness etc.
4/ If the taper is now so loose that its slipping on drive then it should come off no problems.

On the cavitation side of things, familiar with this on propellers and pump suctions but never heard this used to describe action of rease! Do you have any more symptoms on this

Regards

Gerry


Sorry, been away from "the Island" for too long so the Terminology gets mixed up at times.
Yes I meant "lapping in"
But 'aint the English language formidable? To lap in those parts you use "grinding Paste"

In the good old days on Bike's those things were called Cotterless Crank Sets.
The Crank & Chainwheel fit onto the tapered Square shaft of the "Bottom Bracket Bearing" & pulled up tight via a Centre Bolt (modern cheapies with a Nut)
Here again the use of Grease is a misuse on a Joint that should be made dry.

(I use my Bike's more than my Elan :) )

Cheers
John
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