Author Topic: Drive side main bearing  (Read 546 times)

Offline Zander

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Drive side main bearing
« on: 18.06. 2017 17:02 »
Bear with me folks, I'll keep this as short as possible!
After a bit of a break from the rebuild, today I resumed by dressing the cases with wellseal and assembling it, after which I checked the end clearance which was way out, so I took it apart to see where I'd gone wrong. My first thought was the thickness of the sealant, although I put it on sparingly with a brush. Eventually, I did a dry assembly ( no sealant), prior to which for some reason I put engineers blue on the face of the main bearing outer race then got the clearance to two thou.  Took it apart and found a perfect circle of blue on the crank shaft web.  Then I REALLY started lookin!  On the old bearing I removed, both faces of the inner and outer races are flush, however, the new bearing outer race projects over the inner by 0.013" i.e. The inner face which butts up against the shims, is recessed, which means the outer is uncomfortably close to the c/shaft.web, and I need 0.013" packing Just to bring the two faces level.
THEN I can address the end clearance issue.  Please put me out of my misery and tell me I'm missing the piggin obvious!!  Both bearings ar NF206, although one is designated W (NSK) and the other ETNP6CN  which is an RHP.
'59 GF

Online Greybeard

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Re: Drive side main bearing
« Reply #1 on: 18.06. 2017 17:15 »
 *warn* Warning, this could be utter rubbish:  *warn*

I seem to have read about people putting shims under the outer bearing race instead of under the inner race. I don't know why. Have you had a good look to see if the crankcase bearing hole is clear?

Offline Zander

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Re: Drive side main bearing
« Reply #2 on: 18.06. 2017 17:31 »
Crank case housing is fine, with the outer race properly in place.The problem is definitely with the bearing due to the inner thrust face that goes up against the shims being 0.013" below the outer housing face.  Probably not explaining myself very well here, I'm confused!!!!!!!!!  But thanks for the prompt *wink2*
'59 GF

Online chaterlea25

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Re: Drive side main bearing
« Reply #3 on: 18.06. 2017 20:45 »
Hi,
It seems you were sold a bad bearing?
Inner and outer should be inline

John
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Offline muskrat

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Re: Drive side main bearing
« Reply #4 on: 18.06. 2017 21:25 »
G'day Zander.
I agree John. Bet you got it cheap on flebay. The proper ome should be a C3.
https://www.bearingrevolution.co.uk/nf-206-c3_-nf_series-cylindrical-roller-bearing-with-a-30mm-_-premium-range-11081
Quick google found this.
Cheers
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Offline Zander

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Re: Drive side main bearing
« Reply #5 on: 19.06. 2017 06:28 »
Good morning, folks.
No, bearing came from a very reliable and reputable source.  I wouldn't put cheap crap in the heart of the engine.  Removed outer this morning. Inner and outer overall widths are the same,  and fitting inner and outer together shows that the inner is protruding from the rear of the bearing by the same amount, so problem is probably in the thickness of rear flange. Strange, but unfortunately true.
The RHP bearing I removed seems a more substantial beast than the new one.  The rollers ars a bigger diameter, and they're wider, too. I shall try to get one of those, I think. 
'59 GF

Offline cyclobutch

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Re: Drive side main bearing
« Reply #6 on: 19.06. 2017 12:35 »
Hi,
It seems you were sold a bad bearing?
Inner and outer should be inline

John

That would be my thinking also. I worked at the RHP plant in Chelmsford through the back half of the 70s and into the 80s - I'm sure we wouldn't have been producing carp like that.
Various, including ...
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Online Greybeard

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Re: Drive side main bearing
« Reply #7 on: 19.06. 2017 15:29 »
...I worked at the RHP plant in Chelmsford through the back half of the 70s and into the 80s - I'm sure we wouldn't have been producing carp like that.

Deffo something fishy about it!

Offline cyclobutch

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Re: Drive side main bearing
« Reply #8 on: 19.06. 2017 15:54 »
...I worked at the RHP plant in Chelmsford through the back half of the 70s and into the 80s - I'm sure we wouldn't have been producing carp like that.

Deffo something fishy about it!

Yeah - swims around the edge of some overly enthusiastic firewall rules.
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Online RichardL

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Re: Drive side main bearing
« Reply #9 on: 07.12. 2018 04:42 »
I have a bad feeling of having asked this question before, but a worse feeling about getting this wrong.

When we speak of "Clearance at main-bearing bush should be 0.001"-0.0015","  I have always assumed that means the difference in diameters. but, taken literally it could be interpreted as meaning the difference in radii, or 0.002" to 0.003" difference in diameter. The important thing is how should my machinist take it? Same question for rod journals.

Finally, if 0.001" - 0.0015" "clearance" are not good values, please let me know.

Not quite what was meant by "Loose lips sink ships," but could apply.

Thanks,

Richard L
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Offline muskrat

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Re: Drive side main bearing
« Reply #10 on: 07.12. 2018 08:51 »
G'day Richard.
The confusion lies with end float and crank to bush clearance. 1 to 1.5 thou" on the diameter and end float good for both.
Cheers
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Online RichardL

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Re: Drive side main bearing
« Reply #11 on: 07.12. 2018 13:07 »
Thanks for the input  Muskrat. It confirms to me that "clearance" is a confusing term for these  measurements. Not that my objections will change anything, but "difference" would seem a better word to use when we refer to diameter No one ever says "oil film thickness," which really seems to describe "clearance" (it seems to me, at least).

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.

Online duTch

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Re: Drive side main bearing
« Reply #12 on: 07.12. 2018 19:18 »

 
Quote
........ No one ever says "oil film thickness," which really seems to describe "clearance" (it seems to me, at least).....

 That's what was written on the assessment/quote I had from the machine shop for my big-ends
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