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Re: Superblend replacement ball bearing ? [Re: Pete R - R.I.P.] #400901
10/27/11 6:34 am
10/27/11 6:34 am
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Posts: 2,571
Oztralia
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Oztralia
Originally Posted by Pete R

The outer race is not actually skidding in the housing when the engine is hot (or it shouldn't be).It's rolling around inside a housing only slightly bigger than itself.At 0.001" clearance,it would appear to rotate in the housing about 2 revolutions per minute,with the engine at 6000 rpm.This might be a good thing for bearing life.The major forces are not always happening on the same spot on the outer race.


Where did this detail of 2 rpm @ 6000 rpm come from ??


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Re: Superblend replacement ball bearing ? [Re: bon] #401079
10/28/11 11:38 am
10/28/11 11:38 am
Joined: Aug 2001
Posts: 1,330
Hamilton, Mass. USA
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Dave Comeau Offline

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I will jump in at this point for my 2c worth.
The timing side crank/bearing would NOT move in it's bore because it is alway being pulled to the right by the oil pump gear.
Will it spin... Yes I would not doubt it one bit, since I also see the burnishing on the outside of the bearing race.
I also highly prefer a roller bearing over a ball any day...it is for a rather moot reason but I HATE to take out the ball outer race from the case over and over when splitting a motor as potentially burnishing the cases and working the bore bigger. A roller/superblend stays in the case untouched unless removing it is part of the job.
With the spec end float as .010 and the commonly accepted lower end of .005, I would NEVER build an engine (at room temp) under .005 end float. My engines are anticipated to be started at well under room temp and I would not purposly risk having the cases shrink down on the crank and binding the end of the rollers until warmed up.
I would have to really be convinced that shiming a crank a few thou to "centralize" the crank for alignment purposes was worth it because at present it is only fairy dust to me.

A counter sunk screw in the perifery of the bearing to keep it from spinning (ala dunstall) seems the only practical solution if it seems to be a problem that really needs a solution. My dunstall built atlas did not have that mod... :bigt


dynodave
BSA 3 1961-1963
Ducati 3 1992-2002
Norton many 1951-1975
87 Serv-Equip 100HP MC brake dynamometer,
Re: Superblend replacement ball bearing ? [Re: bon] #401099
10/28/11 2:45 pm
10/28/11 2:45 pm
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bon Offline OP
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I'd agree with the idea that cases which are 40 or 50 years old at this stage have probabily had their bearing housings worn by repeated removal and installation of bearings during rebuilds, but it would be interesting to ask the various people who make updated engine cases for racing what they think of all this, most of them seem to cnc machine casings from billet rather then cast them. If they were cast it would be possible to have cast in steel bearing housings, or as the cases are of heavier section metal to include a retaining plate recess machined into the sides of the cases.

Re: Superblend replacement ball bearing ? [Re: bon] #401102
10/28/11 2:50 pm
10/28/11 2:50 pm
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Greece
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kostas Offline
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Greece
Hey bon what have you do with the roller bearing from the drive side?I read that you fit norton crank in Triumph cases.

Re: Superblend replacement ball bearing ? [Re: bon] #401112
10/28/11 4:16 pm
10/28/11 4:16 pm
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bon Offline OP
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Hey kostas

I am putting a commando 850 90 degree crank into triumph pre- unit cases, i was just going to put the crank in as a normal 360 degree crank but seen what chris ( 76 degree) has done with his engine, i have access to machine tools so said why not. I am going to reduce the diameter of the outer race of the superblend bearing in a cylindrical grinder so neither the crank cases or crank main shafts will have to be altered.

Re: Superblend replacement ball bearing ? [Re: bon] #401133
10/28/11 6:01 pm
10/28/11 6:01 pm
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Greece
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Greece
Yes I did the same in unit cases much better to grind the outer race than grind the shaft!Good luck with your project cheers kostas!

Re: Superblend replacement ball bearing ? [Re: kostas] #401162
10/28/11 7:30 pm
10/28/11 7:30 pm
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Posts: 44
Pueblo Co.
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comnoz Offline
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I have had two bad experiances with a shim getting loose between the inner race and the crankshaft. One was a 750 racebike that just wore into the shim and spit it out where it was found in the sump screen. The other was a streetbike I purchased. When I tore the motor down I found it had a spring steel shim that had been loose between the drive side bearing and the crank. It had spun there long enough to cut a 1/16" groove in the shaft. Jim

Re: Superblend replacement ball bearing ? [Re: Rohan] #401166
10/28/11 7:54 pm
10/28/11 7:54 pm
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Pueblo Co.
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comnoz Offline
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Originally Posted by Rohan
[
Where did this detail of 2 rpm @ 6000 rpm come from ??



C of the bore minus the c of the bearing over the c of the bore times 6000 means the bearing would be rotating approx.2 rpm at .001 clearance. Jim

Last edited by comnoz; 10/28/11 8:04 pm.
Re: Superblend replacement ball bearing ? [Re: bon] #401170
10/28/11 8:36 pm
10/28/11 8:36 pm
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Boston, Massachusetts
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John Healy Offline
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Oh yeh, of course the dreaded C!


Re: Superblend replacement ball bearing ? [Re: John Healy] #401181
10/28/11 10:27 pm
10/28/11 10:27 pm
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Pueblo Co.
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comnoz Offline
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Re: Superblend replacement ball bearing ? [Re: comnoz] #401193
10/28/11 11:44 pm
10/28/11 11:44 pm
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Oztralia
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Oztralia
Originally Posted by comnoz

C of the bore minus the c of the bearing over the c of the bore times 6000 means the bearing would be rotating approx.2 rpm at .001 clearance.


Surely this depends on the internal friction in the bearing ?
Different oils could easily influence this too.

It could be spinning at 2 rpm per month, and we'd be none the wiser !? Never mind that it shouldn't be spinning at all...



Re: Superblend replacement ball bearing ? [Re: bon] #401200
10/29/11 12:12 am
10/29/11 12:12 am
Joined: Mar 2005
Posts: 10,218
Boston, Massachusetts
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John Healy Offline
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But, Jim you are assuming the the outer race of the NU306 roller is staying square to the bore as the crank is flexing and is free to rotate. And I think we can agree these vertical twins cranks flex. As the crank flexes, the movement is transmitted to the outer bearing race cocking it in the bore. This alone is enough to prevent the bearing from freely rotating even though, through abnormal heat collection in the crankcase, it might not still be a press fit in the bore. This action can add enough leverage during heavy detonation to break the cases. Not unheard of in a Norton.

At certain temperatures and adverse conditions (detonation) I can certainly see movement in a roller, but because of the cocking of the bearing in the bore, I would expect to see the galling, or fretting, exhibited in your picture by the second bearing from the left, and exhibited on others a bit less.
Sure, the others to the far right show signs of a little rotation, but it wasn't constant rotation.

Only the left most bearing shows the polishing typical of near constant rotation. I think you would need more than .001" clearance to see that type of damage from constant rotation. I suspect that bearing was loose in the case when it was removed and required little, if any, heat to remove.

What do you think?
John


Re: Superblend replacement ball bearing ? [Re: John Healy] #401206
10/29/11 1:21 am
10/29/11 1:21 am
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Pueblo Co.
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comnoz Offline
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John,
I certainly assume that the bearing is likely to wobble a bit in the bore. If you look at the outside of the bearing you can see the edges of the bearing are polished more than the center which I have taken to mean the bearing likely cocks with the flexing of the crank.
I certainly measure the interferance before assembly. Of the motors I have rebuilt I can only remember one that I replaced the cases because of wear in the main bearing bores. It was a very high milage 750 and had other problems or I may have attemted a repair. The od of the bearings wear more than the case as one would expect as the oxides that cause the wear are embedded in the softer material and slide against the harder surface causing wear.
I really would not expect constant motion. It would surely depend on a lot of things such as temp , load and rpm. I would expect the most rotation during coast down from a high rpm. That would be when the counter-rotating orbit of the crankshaft would be at it's highest and pressure loading would be at it's lowest. Of course it's all just speculation. All I know for sure is they are never in the same place when I remove them as they are when I install them. Jim

Last edited by comnoz; 10/29/11 5:07 pm.
Re: Superblend replacement ball bearing ? [Re: comnoz] #406120
11/28/11 9:35 pm
11/28/11 9:35 pm
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Posts: 94
Lancashire UK
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Lancashire UK
Hi, I've just read this thread first to last, and unless I missed it, did anyone answer the original question? Personally I use a superblend on the driveside and a full complement ballrace M306C3 on the timing side, this has worked much better for me than any other combination I tried.
This other debate seems to be of the'how-many-angels-can-dance-on-the-head-of-a-pin' type, very interesting but ultimately academic.

Last edited by oilyrag; 11/28/11 9:36 pm.

Oil is always cheaper than metal
Re: Superblend replacement ball bearing ? [Re: oilyrag] #406159
11/29/11 12:14 am
11/29/11 12:14 am
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Seeing as the 306 bearing is larger in its load carrying capacity then the bearing that triumph use in their similar twin, which is mj 1 1/8 e off the top of my head, i don't see why it wouldn't work. The reason i asked the question originally was i wanted to use the timing side bearing to locate the crank axially.

Re: Superblend replacement ball bearing ? [Re: bon] #406629
12/01/11 9:15 pm
12/01/11 9:15 pm
Joined: May 2007
Posts: 94
Lancashire UK
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Lancashire UK
Quote
Does anyone know the make or number of the ball bearing used sometimes to replace the superblend on the timing side of norton commando cranks ? It has more ball then normal 9 or 10 i think and has higher load carrying capacity then usual.



Quote
Seeing as the 306 bearing is larger in its load carrying capacity then the bearing that triumph use in their similar twin, which is mj 1 1/8 e off the top of my head, i don't see why it wouldn't work. The reason i asked the question originally was i wanted to use the timing side bearing to locate the crank axially.



Yes well thats why I did it, too, but I don't want to claim that it was my idea, Paul Dunstall recommended it back in the early 70's.



Oil is always cheaper than metal
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