Why ball bearing mains?

Why would anybody want to use anything but roller (Superblend) style bearings for the main bearings in a Norton big twin.

At the risk of starting an opinion war, I would like to hear some of the pro's and con's of the choices. I see the primary options are 1.) Superblend for both sides, 2.) ball bearings for both sides or 3.) a Superblend type for the drive side and a ball type for the timing side. I guess I am trying to flush out the rationale for any given choice which can range from keeping it original, this is the way we always did it, serviceability, absolute need or ????????????

Keep in mind that the Superblend style solution was either not known, not needed and/or not available in the early years of the Norton big twins.

Beats me, The myth that a ball bearing locates the crankshaft is just that. Look at the outside of any used main bearing and you will see it has been rotating in the cases. If it can rotate then it can float from side to side also.
The only time I have seen a used main bearing that did not show signs of rotation was a C3 bearing in a Maney case. Jim

comnoz said:

Beats me, The myth that a ball bearing locates the crankshaft is just that. Look at the outside of any used main bearing and you will see it has been rotating in the cases. If it can rotate then it can float from side to side also.
The only time I have seen a used main bearing that did not show signs of rotation was a C3 bearing in a Maney case. Jim

Click to expand...

Sorry Jim,
If I understand you correctly you want to mount two superblend?.
Well, if i use two superblend i must fit two shim, one for ude, or only one?
Thanks.
Ciao.
Piero

case. Jim[/quote]

Sorry Jim,
If I understand you correctly you want to mount two superblend?.
Well, if i use two superblend i must fit two shim, one for ude, or only one?
Thanks.
Ciao.
Piero[/quote]

I would recommend two superblends.

You can shim it on one or both sides if you want.

Shimming is not really needed for most street applications. None of them were shimmed from the factory -with ball or roller bearings.

If the case is worn where the bearing has been rotating then a shim may be needed. I would not like to see end play getting much more than 1mm.

If you are building a racebike then shimming to place the crank journals directly under the centerline of the piston is a good idea. Jim

By the way, if you do shim for endplay you want to use the shims that go in the case before the outer race, not on the crank. The small shims that fit on the crank are notorious for coming out and getting ground up in the motor. Jim

In My Honest Opinion! OK?

First off let me say I have superblend in both sides and shimmed to 10 thou. I have a tendency to run up to red line once in a while. I have a hot street machine and with some talent and experience this was a viable option for me but still questionable whether it is absolutely needed.

Shimming is a pain for a good mechanic and daunting for a novice. For the most part, superblends in both side can be considered as overkill and the variable of shimming makes it ALMOST illogical.

It's the drive side that takes the load and I think the Combat really made this issue surface. Along with the upgraded machining of the later cases and the roller bearing in the drive side, did the issue settle down to an acceptable level.

I think someone must have come to a conclusion and said "what's good for the goose is good for the gander" and shimming needs became evident. I wonder with who and how this originally came about.

This being said, the practice (superblend in both side) is now all to common and almost considered as a standard way to go about it. It is it's obsolute necessity that will feed the fire of this opinion war.

For what it's worth, I don't like shimming the gearbox either. I feel failure here comes from abuse, with clutchless shifting and hard downshifting as the culprets. But that's another topic.

comnoz said:

By the way, if you do shim for endplay you want to use the shims that go in the case before the outer race, not on the crank. The small shims that fit on the crank are notorious for coming out and getting ground up in the motor. Jim

Click to expand...

Further to Jim's post, shimming on the crankshaft I have seen instance where the shims went "off center" and crept up the filet radius.

From a trial and error standpoint for shimming I consider pulling the inner race somewhat destructive which leaves the outer race the only viable option where with moderate heat on the cases, the outer races drop out.

I seem to recall shims were readily available from a standard stockist such as McMaster Carr and/or bearing supply outlet.

Also, Jim mentioned shimming two types of shimming, one is to take up radial "slack" due to worn or wallowed out cases and one to set end float to an acceptable level. Furthermore, I see no reason why the Superblend type would wallow out cases as the crankshaft is allowed to float (within limits) and once the outer races are in-place they cannot be pulled out during operation. On the other hand, with one or two ball type bearings, something has to give and that is where I suspect the wear and tear on the main bearing bosses in the cases occurs.

pvisseriii said:

In My Honest Opinion! OK?

First off let me say I have superblend in both sides and shimmed to 10 thou.

Click to expand...

Dear Sir,
It means you fittted o both ide two 0,10 shims?.
Regards.
Thanks.
Ciao.
Piero

pierodn said:

pvisseriii said:

In My Honest Opinion! OK?

First off let me say I have superblend in both sides and shimmed to 10 thou.

Click to expand...

Dear Sir,
It means you fittted o both ide two 0,10 shims?.
Regards.
Thanks.
Ciao.
Piero

Click to expand...

No, what that means is that I have .010" end ply on the the crankshaft. I do not recall the shims that are installed but I believe a .010 and a .005 for a total of .015, both in the drive side. That was my best first quess and luckily it was spot on.

Setting the outer race should be done sparingly as every attempt degrades the machined surfaces. Heat is your best friend. Use a little to place the race in place. When removing the race turn the case over and heat the case around the bearing till it drops out. I did this cycle at least once to verify the end play and then add the loctite bearing adhesive for final assembly

comnoz said:

Beats me, The myth that a ball bearing locates the crankshaft is just that. Look at the outside of any used main bearing and you will see it has been rotating in the cases. If it can rotate then it can float from side to side also.
The only time I have seen a used main bearing that did not show signs of rotation was a C3 bearing in a Maney case. Jim

Click to expand...

Any reason why Matt uses a high capacity ball on the timing side then? I'm pretty sure that's what went into my rebuilt engine. Difference of opinion? Just curious.

Shimming t o control radial slack sounds very strange to me. Manx nortons are fitted with secured steel sleeves for that purpose , and I cannot see the sense in shimming superblends. I use one at each end of the crank so it can flex without destroying the cases or the bearings, and the timing side bearing is locked to the crank by the timing gear and the nut so the end float is controlled by the barrel shaped rollers in the superblend bearing on that side . The drive sprocket is on a taper, so doesn't end load the bearing on that side. The only reason I would shim the crank would be in case the timing side bearing moved in the cases. I don't shim anyway, if the crank moves to the max either way no end loading of anything occurs. The clearances at the rod little ends is sufficient.

Well maybe the oil pump and cases or crank were not designed for a plain bush which might not tolerate crank flex as much as narrower regular roller element bearing,

There were two rationales for the ball bearings, 1, to ease factory assembly vs the shimming, which we know Norton would of skipped any way, 2, the early 750 drag races used a pre-superblend barrel shaped roller on DS and a more ball filled TS bearing that fixed the crank from shifting - so their hi rpm crank whiplash flex could be taken up some by TS balls and let thin side DS case flex take up what it could on that side with bigger load bearing bearing. This is what Ms Peel ran wild with in her prime but now doing duty in Wes's '71 about 4 yr and two ring jobs so far. The only issue with balls I've been able to glean is they can wear out faster than a roller and trap the crank in case till your good friend heat loosens the grip, ploP.

@acotrel

Radial shimming is not a common industrial practice but is used as a stop gap when clearances get out of spec. If bearings are that loose on a Norton twin I would be looking to replace the cases and/or weld/repair them.

I think you nailed it when you said you use Superblends on both sides so that the cases are not destroyed.

When using two Superblends, the timing side bearing is not locked to the crank by the timing gear and the nut, only the inner race.

With a timing side ball bearing the ball bearing is locked to the crank by the timing gear and the nut. In this situation (in the ideal world) any expansion or contraction of the engine cases due to temperature change would be accommodated by the Superblend on the drive side but how would you know what clearance you would have on the drive side? There's no easy way to determine or set end float.

Snorton74 said:

comnoz said:

Beats me, The myth that a ball bearing locates the crankshaft is just that. Look at the outside of any used main bearing and you will see it has been rotating in the cases. If it can rotate then it can float from side to side also.
The only time I have seen a used main bearing that did not show signs of rotation was a C3 bearing in a Maney case. Jim

Click to expand...

Any reason why Matt uses a high capacity ball on the timing side then? I'm pretty sure that's what went into my rebuilt engine. Difference of opinion? Just curious.

Click to expand...

He gave that up some time ago. Jim

Here is a picture of some main bearings removed from engine rebuilds over a couple years. None of them were raced- just street bikes. Notice how all of them have scatches around the outer race. They got there because the bearing was turning in the bore. At normal operating temperature the bearing no longer has an interference fit and it will move around in the case.
The only way to use a ball bearing to control the end play is to use screws and washers or a retainer to keep the bearing from moving sideways in the case. Jim



They also have wear on the sides of the bearing.

comnoz said:

At normal operating temperature the bearing no longer has an interference fit and it will move around in the case.
The only way to use a ball bearing to control the end play is to use screws and washers or a retainer to keep the bearing from moving sideways in the case. Jim

Click to expand...

I recall reading about the pinning the bearing modification (Dunstall?) but do not recall if it called out for doing both sides. The problem I see with doing a both sides with ball bearings is that the cases and bearings will go in a bit of a bind with temperature change.

Jim, that's why I pin the main bearing outer races (a la Dunstall) on race engines now. They might still loosen up with use, but at least I know they aren't turning.



Ken

Ask Peter Turner (O.N.O.A.) how he feels about spinning outer races in 828 cases. Really hurt his plans for this past 2012 season. Yes ,heat is your friend (and bearing freezing) , honestly have never measured end float on my bottom end rebuilds but have ALWAYS replaced any original bearings with the Superblends ,and yes removal of inner race such a pain resorted to Dremel cutoff tool and a smack . To answer the original thread question : Norton cheaped out then (costs ,availabilities and supplys and old stock )- but now we don't have to do we ?

lcrken said:

Jim, that's why I pin the main bearing outer races (a la Dunstall) on race engines now. They might still loosen up with use, but at least I know they aren't turning.

Ken

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How do you machine the indent in the bearing ?

I recall reading about the pinning the bearing modification (Dunstall?) but do not recall if it called out for doing both sides. The problem I see with doing a both sides with ball bearings is that the cases and bearings will go in a bit of a bind with temperature change.[/quote]

You sure wouldn't want to do both sides with ball bearings. Dunstall just did the timing side.
I think he did two or three retainers like the one in Ken's picture. Jim