Author Topic: Drive side main bearing  (Read 1607 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
1961 Super Rocket
1963 RGS (ongoing)

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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.
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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

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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.
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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!

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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
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020 (if it's not cancelled and we are free to move about by then). Watch website at https://www.gentlemansride.com for details.

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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.
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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 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020 (if it's not cancelled and we are free to move about by then). Watch website at https://www.gentlemansride.com for details.

Offline 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
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
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Online Colsbeeza

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Re: Drive side main bearing
« Reply #13 on: 08.04. 2020 06:06 »
Gents - The COVID lockdown *sad2* this week has got me started on reassembling the A10 after many idle months *roll*. The Driveside Roller Bearing in my 1960 Flash is unfamiliar, and I am considering whether to replace it for a known brand. It has markings OE and 2n06 and nothing else but is to NF206 specs. I got this bearing in the 1990s and cannot remember where from, but likely C&D or D/Fly. It has an unsymmetrical metal cage like in the attached NSK image. Is my bearing familiar to any Forum members? I have no idea what Clearance it is but the ā€œnā€ may mean Normal or CN. I had to work the Inner a bit to get it to slide in, so I guess that the Clearance is probably CN or C2. It has only 12 rollers of 7.5mm width, whereas the ones Muskrat referred to (Reply #4) from Bearing Revolutions is for an NF206 with C3 clearance, and has at least 15 rollers if the image is for that bearing. I suspect that 12 rollers is enough for a standard Flash.
The photo before it was removed from the crank by the machinist before crank balancing shows that I had it the wrong way around, but much easier to get something behind it for removal. If I were to reinstall it correctly, the large diameter side of the cage is almost touching the flywheel, with very little space to get anything behind it or behind the rollers. Unlike Zanders problem the Inner can go either way into the Outer with no offset between the surfaces of the inner and outer. I wonder whether the cage shape acts as an oil slinger favoring the largest side?
The motor has only 80 miles on it, so I am not overly concerned about patterning wear on the bearing. The Inner is a tight fit on the crank. It would not push on cold but slid on OK after sitting in boiling water and off again (quickly). The crank condition is good. If I reinstall it, I am thinking I would put it back in the way it came out. ie the inner reversed for removal tool access.
I am wondering whether to reinstall it or to lash out for a well-known brand with guaranteed C3 Clearance? Problem is cost *conf2* ā€“ I would like to buy three ā€“ One to Install, One to grind the inner for a loose fit for shim setting, and a third for a spare to make sure it is availability for a future rebuild.  Opinions most welcome.!!
Colsbeeza
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Re: Drive side main bearing
« Reply #14 on: 08.04. 2020 10:03 »
When I saw that post from duTch I had a happy moment. Then realised it was from two years ago :(