Crank movement

BERT said:
If you are considering shimming the outer races and if you measure the end float before you disassemble the crankcases and the outer races are not fully seated ( which is possible if they are rotating in the crankcases), I think you will get a false reading trying to determine the shimmage.
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Of course that is right, but you may misunderstand my intent.

I have nothing to suggest the bearings are rotating.

I am simply observing that the end float seems more than I remember. I think it is useful to check that, no more.

It isn't something that should change in use. But a bang on the end of the drive side may have had an impact!!

(really I think this is unlikely, but I will check)

If I do decide to change the bearings for any reason, I will need to start again!
 
I'm beginning to wish I had kept quiet too, but I did say I haven't measured it!

Well I have now!! 0.012"

....so frankly, I shall stop worrying about it.

Or more realistically, I shall move on to the next thing to worry about!!

Yes, it is an age thing!

I will as a background task keep looking for bearing outer style shims, most likely an off the shelf shim like the VW ones. Mainly to be ready for the eventual main bearing replacement. It'll happen one day!
 
worntorn said:
I'm beginning to wish I hadn't mentioned the subject of outer bearing rotation in cases, especially if people believe I'm misquoting or " taking things out of context". As I recall, it was just an observation by Jim and not anything to get concerned about for regular roadbike use.
The thought was that this is something that occurs now and then , for example on a hot day with a hot engine at high rpm in 2nd gear just before shifting, perhaps the outer race turns a turn or two.
There is no damage left behind, just the sign of some small amount of rotation.

This is not the discussion I had in mind, but the last sentence conveys the same info. A hot case that expands sufficiently for the outer race to " float". While it is floating its not hard to imagine it might turn once or twice.




No end float

At normal operating temps there is no interference fit to the bearings, they are free to float. With a used case the sun could easily heat the case to where there is no interference fit. That is why guys who install a timing side ball bearing thinking it will locate the crank are doing...
www.accessnorton.com www.accessnorton.com
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MFB said:
comnoz said:
At normal operating temps there is no interference fit to the bearings, they are free to float. With a used case the sun could easily heat the case to where there is no interference fit.

That is why guys who install a timing side ball bearing thinking it will locate the crank are doing nothing unless they install screws to hold the bearing stationary in the bore. Jim
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Exactly. And that's the main worry you have IMO. Jim has talked about spun bearings in the past (probably many times).
I devoured a lot of good advice from this forum when I was in the process of rebuilding my engine, and I'd say that what Jim doesn't know about engines isn't worth knowing.

If the bearing starts to spin it will wear the case and get even looser.

John Hudson's engine building notes recommend using bearing retaining compound to prevent bearing spin. He claims that the factory used it on new engines and I suppose he would know.

My cases showed signs of minor spin - I'd bet they all do.

I chose to fit my bearings with Loctite 641 bearing retainer.

While you have the engine on the bench, it's something worth looking into.

Cheers
Martin
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Actually rather than spinning in the case due to drag I suspect the bearing rolls around the inside of a hole that is slightly larger than the bearing OD. This roll is in reaction to the imbalance force which rotates in the opposite direction to the crank. This causes the bearing to roll slowly in the same direction as the crank rotates. Since the rolling is actually very slow little damage is done.
I have tried installing the bearings with 641 and on the next diss-assembly found no signs of locktite and the bearings had moved from where they were when assembled.
I did use JB weld the last time I put my lower end together but I don't know if it held. I really doubt that it did. Jim
 
Nigel wrote - "
Maney cases are much, much thicker in this area, and (I imagine) machined to tighter tolerances, and they’re not 50+ years old. So I’d hope Maney cases would be better with regards to this.".
I don't think the thickness helps with this.
I was advised by Molnar and others in the know to stake my super strong/ thickened 1360 cases for high rpm use. The cam makes max bhp at 6500 so it does see 7000 rpm.

Molnar routinely stakes mainbearings in the Manx engines as well. Of course those are magnesium, but it shows that bearing staking is widely done in race engines, and it works.
I did not stake the 920 as it is a stock cam midrange road engine with max torque at about 5200 rpm, max bhp at 5900.
Glen
 
I think this thread is dead, but...

Just to see what supply was like, and for future bearing changes, I ordered a couple of VW shims, using the first link from Seeley920.

0.010" and 0.008" thick, other thicknesses available.

I measure them at 70.04mm OD and 53.96mm ID

So pretty close to 70/54. But not the 70/58 that TW has made.

My guess would be that if you have Old Britts supplied shims, they will measure pretty close!

Anyone got them? Done that?
 
SteveA said:
I think this thread is dead, but...

Just to see what supply was like, and for future bearing changes, I ordered a couple of VW shims, using the first link from Seeley920.

0.010" and 0.008" thick, other thicknesses available.

I measure them at 70.04mm OD and 53.96mm ID

So pretty close to 70/54. But not the 70/58 that TW has made.

My guess would be that if you have Old Britts supplied shims, they will measure pretty close!

Anyone got them? Done that?
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Hello Steve,
I have ordered a shim set from Old Britts, to fine tune the crankshaft end play. I have already put small Dia, shims behind the inner race after new FAG superblends (made in India). The large Dia. are very useful, because I'm very reluctant to pull out the inner race (interference fit of .0005''). The large shims dimension are 70X57 (measured with a caliper).
The measured end play is .007'' which is within Old Britt's specs (.005-.010). I haven't read consensus about the specs. Some say .010-.030, other ( John Hudson/NOC) not to worry too much as long there is some float. My local machinist's opinion is that the Norton crankshaft isn't long enough to vary much under heat. Any one have ever tested the crankshaft elongation under heat???It's far beyond my skills.
Sergio:)
 
Yes, the OP appears to have checked out, but this thread shows how much interest there is in this issue. So, I'm posting these pictures of my solutions to the bearing looseness problems, from a few years back. To be fair, this example is from a well thrashes short stroke 750 race engine, and might be overkill for a street bike. But it definitely keeps the bearing from spinning. :) Like other members here, I have tried Loctite and found it didn't last. My first fix was the one recommended by Dunstall in his tuning book, a hardened washer fitting into a notch ground in the outer race

Crank movement


That worked well for several years of racing, but eventually the bearing to case fit became loose again, so I tightened it up by fitting a bronze sleeve, but also still using the locking washer. I haven't yet used these cases, but the bronze sleeve is a pretty standard fix for a hammered out bearing race, so I'm pretty confident it will hold up. Just have to get around to building this engine again. So many projects, so little time.

This is a picture of the cases with the sleeve installed and finish bored.

Crank movement


Ken
 
From an engineering perspective, is there any difference between pressing in a bronze sleeve versus an oversized bearing? The forces expanding the aluminum case would be about the same. This assumes an oversize bearing is available, but this could be accomplished through plating the outer shell. Just thinking about options.
 
Stephen Hill said:
From an engineering perspective, is there any difference between pressing in a bronze sleeve versus an oversized bearing? The forces expanding the aluminum case would be about the same. This assumes an oversize bearing is available, but this could be accomplished through plating the outer shell. Just thinking about options.
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No, and in Industry maintenance dept's get the bearing OD copper plated as their preferred method, if the plating is too thick then its soft enough to reduce using emery cloth until you get it to size which could not be done with chrome. Platers know how to shield the bearing innards so they do not get plated.
 
kommando said:
No, and in Industry maintenance dept's get the bearing OD copper plated as their preferred method, if the plating is too thick then its soft enough to reduce using emery cloth until you get it to size which could not be done with chrome. Platers know how to shield the bearing innards so they do not get plated.
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That would work. I've copper plated the inside of the inner race to make up for wear on the crankshaft snout, but never tried it with the outer bearing. There are a couple of reasons I prefer the bronze sleeve. It corrects any out-of-round conditions in the crankcase bearing bore, and the bronze sleeve is a considerably harder material than the copper plating. But it is a considerably more complex fix than copper plating. There are clearly more ways than one to approach this problem. The simplest (but most expensive) fix is new crankcases. In the example I showed above, I had already put a lot of effort into welding and machining the cases for reinforcement, and wanted to salvage them instead of starting over.

Ken
 
lcrken said:
That would work. I've copper plated the inside of the inner race to make up for wear on the crankshaft snout, but never tried it with the outer bearing. There are a couple of reasons I prefer the bronze sleeve. It corrects any out-of-round conditions in the crankcase bearing bore, and the bronze sleeve is a considerably harder material than the copper plating. But it is a considerably more complex fix than copper plating. There are clearly more ways than one to approach this problem. The simplest (but most expensive) fix is new crankcases. In the example I showed above, I had already put a lot of effort into welding and machining the cases for reinforcement, and wanted to salvage them instead of starting over.

Ken
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I sleeved both races in a set of MK3 cases I was using for racing. It had 2 advantages. 1. It corrected the fit for the bearings. 2. It allowed me to get the main bearings in line with each other. One side was .025" lower than the other. They were a very low mileage matched pair of cases, so left the factory like that. It's not uncommon if you look at how high the pistons come compared to each other above the bore (on a 750).
 
Not meaning to interrupt discussion on sleeving, and getting back to loctite: would it make a difference if the loctite was only applied to the bottom(weightbearing) quadrant of the bearing housing to allow for the different thermal expansion of the steel and alloy to repeatedly happen? Just looking at lazy options...
 
kommando said:
and not logged on since 5th June !!!
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I guess the ragging he got for his 1/8" comment drove him away....

Whereas, I will just have to live with worrying about too much end float and then actually measuring it right in range!
 
A lot of your input SteveA is being noted by myself.
Sorry that I gave you an Angry to one of your posts, I fell asleep while reading and the tablet slipped in my fingers.
Don't take it to heart
Back to end float, I have 0.018" which is just over the max. 0.015" which is in the book. As I will be splitting the cases I would like to take it down to a max of 0.010" or thereabouts.
Should the shims be installed under the timing main bearing shell if none are under the inner bearing on the crank?
Or should the required distance be split e.g. 0.004" on both sides? Naturally it will depend on how the bearings are shimmed at the time being.
 
Woody850 said:
A lot of your input SteveA is being noted by myself.
Sorry that I gave you an Angry to one of your posts, I fell asleep while reading and the tablet slipped in my fingers.
Don't take it to heart
Back to end float, I have 0.018" which is just over the max. 0.015" which is in the book. As I will be splitting the cases I would like to take it down to a max of 0.010" or thereabouts.
Should the shims be installed under the timing main bearing shell if none are under the inner bearing on the crank?
Or should the required distance be split e.g. 0.004" on both sides? Naturally it will depend on how the bearings are shimmed at the time being.
Click to expand...
I was curious about the angry...haven't had one of those before :oops:

I would leave it at 0.018" too, like others have said...it's a lot of work for a really small issue.

The concern that people have with the small shims behind the inner race is the possibility of them squeezing out.

Note that both Norman White and the late Mick Hemmings would have shimmed them this way for decades, so it can't be that bad a risk in most cases!

But, timing side only, because whatever the risk of a shim 'squeezing out' it is going to be higher on the drive side!
 
SteveA said:
I was curious about the angry...haven't had one of those before :oops:

I would leave it at 0.018" too, like others have said...it's a lot of work for a really small issue.

The concern that people have with the small shims behind the inner race is the possibility of them squeezing out.

Note that both Norman White and the late Mick Hemmings would have shimmed them this way for decades, so it can't be that bad a risk in most cases!

But, timing side only, because whatever the risk of a shim 'squeezing out' it is going to be higher on the drive side!
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Also note, prior to using rollers in both sides, the timing side race was a ball race. No lateral float to speak of so no shims.

Meaning that the timing side is the side that does the side to side location, so it seems to me logical to shim that side! It has the pump worm tightened onto it to keep stuff located.

Or does someone know different?
 
IMHO which side to shim is unanswerable with the info we have. I would not shim it but if I did my goal would be to get both rods as close as possible centered in their cylinders and the end float as small as possible with no binding at the lowest temperature the engine might encounter.

1) Assemble cases with crank and rods and install cylinders with no pistons.
2) Put the engine in a freezer overnight
3) Accurately measure the crank end float
4) Let it warm to room temperature
5) Accurately measure the crank end float
6) Push the crank and both rods to the timing side and measure the rod to cylinder wall gap in both cylinders.
7) Push the crank and both rods to the drive side and measure the rod to cylinder wall gap in both cylinders.

With those measurements, you can determine the amount of shim to put on each side of the crank to center both rods in their cylinders (as much as possible) while achieving the desired end float.

Alternatively, if you trust that the cases and crank were optimally made (I don't), you can cheat and shim half the desired amount on both sides.

Alternatively, if you believe that the crank and cases didn't change from the days when the timing side had a ball bearing (I have no idea), then the shims should only go on the drive side.
 
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