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Re: Crankshaft shimming [Re: CarpeDiem] #791538 11/28/19 11:43 am
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NickL Offline
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The cranks are different widths definitely, as for the machining you've got me thinking now maybe the later ones are wider.....
but either way they need checking when putting the old crates together. Note that the flange on the timing side bearing is
thicker on the early type as well. Many of the ones i've worked on have been put together with mismatched odds and sods.
If you go through the exercise of centreing the crank etc it all comes to light and can be corrected with spacers/shimming.
Allowing any crank to be fitted in any set of cases with any bearing type. Blimey, i never expected the Spanish Inquisition................................
https://www.youtube.com/watch?v=HqF_nPbX_Ow


The coefficient of expansion of casting alley vs chrome-steel is at least 1.8-1 so the bearing will expand far less at 100 deg
when both materials are heat soaked, the case, as it is a larger mass will take a little longer to get there.
https://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html

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Re: Crankshaft shimming [Re: Allan Gill] #791543 11/28/19 2:03 pm
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""From a previous experience with the same motor, I was having bearing cages crush, despite there being enough clearance to clear the crank, there was insufficient clearance when hot, power was being sapped and the needle roller was being crushed down onto the bearing cage. (creating more clearance was the mechanical change was made, this was before fitting the ball bearing DS bearing)

An example of heat coeff for steel vs alloy can be seeing if you drop a crank case in a warm heat soaked over vs putting in an oven then turning it on. If the oven is heat soaked the aluminium should expand more rapidly than the steel (bearing) and the bearing will drop out. Put them both in a cold oven and turn the heat on and they will both expand at the same rate, you stand as much chance the bearing dropping out then as you do with the cases at room temperature. The crank and cases will both heat at a similar rate.""



Mr.Gill All of the engineers I know will call this nonsense..


Arnstein

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Re: Crankshaft shimming [Re: CarpeDiem] #791544 11/28/19 3:17 pm
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Allan Gill Offline
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Which bit, you've selected a large piece so please elaborate?

If your referring to the cases in the oven then try it!!!

If your referring to my example then please see the thread I did at the time. Lightning resto .
a small epset below:

Originally Posted by Allan Gill

I think when I had this apart last time I must have decided I didn't want to do it again. As it took a good bit of effort separating some of the parts. The barrels were well glued to the crank case.

I eventually got the cases separated the timing side was stuck within the needle rollers and whilst they rotated around its centre they would not leave the crank. So enlisting a rubber (peg) mallet, and drifting against the crank case I managed to seperate the two.

Sure enough the setup had crushed, despite it having free movement at the initial build stage. But instead of cracking the bearing outer cage, it crushed it, forcing the needle rollers to a taper and damaging the surface on the sleeve. It had also worn a recess into the crank web in the process.

[Linked Image from i1182.photobucket.com]

[Linked Image from i1182.photobucket.com]

Luckily I have another full width replacement sleeve.

The new bearing is much narrower, and I have retaining ring to take up the additional distance.
The new bearing is needle only. And does not incorporate the ball race which controls end float. Which is not required because of the out rigger plate I have on the drive side.

[Linked Image from i1182.photobucket.com]

I milled the raised part which would normally locate the thrust washer (a little crude but it does the job)

[Linked Image from i1182.photobucket.com]

fitted the new bearing

[Linked Image from i1182.photobucket.com]

and fitted the bronze ring, which may not be required

[Linked Image from i1182.photobucket.com]


I hope to find that this is where I have been loosing HP and top speed.

the cam bushings in the inner timing case will have to be reamed out to accept the 0.878" diameter (which must have escaped QC on its day of manufacture) standard being 0.874" so I now need to come across a ball bearing to fit the DS case cam bush and an adjustable reamer.

I am going to measure the original 68 crank and the OIF crank (now in use) and note the differences


beerchug
Re: Crankshaft shimming [Re: CarpeDiem] #791548 11/28/19 4:41 pm
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Thermal conductivity of 360 aluminum is 150 W/(m K) and 5% chrome steel is 40 W/(m K).
https://www.engineeringtoolbox.com/thermal-conductivity-metals-d_858.html
Putting the case in a heated oven (bake, not broil, so it is the air doing the heating) the aluminum has a greater surface area than the bearing race so presumably the heat will conduct through the aluminum faster than the steel and expand at a faster rate than just the difference in linear expansion coefficient. It might be an interesting experiment with an IR camera to see the difference in temperature of the bearing and case in the oven. Possibly use a temperature crayon.
Allen, could it be the whipping of the crank is causing the ends of the rollers to dig into the race and flair the race? Needle bearings do not take shaft misalignment well.
The cam bush problem is unclear. It is now 0.878", standard is 0.874" and you have to ream it out further?

Re: Crankshaft shimming [Re: CarpeDiem] #791549 11/28/19 5:23 pm
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The even more whipping prone Norton twin crank works better with 20 to 25 end float, as the mains journal get to high revs they get wider on one edge so you need the space for this. The 'superblend' marketing term Norton came up with was just the normal roller bearing industry incremental design change of added crown on the edge of the rollers so they did not dig in, not a spherical roller. Now the question is did they add extra crown to needle rollers, I doubt they did so a shorter needle roller will have an easier life with a whippy crank. Be worth asking the needle roller makers if they do a extra crown on the needle bearing version in the A65 size.

Re: Crankshaft shimming [Re: CarpeDiem] #791558 11/28/19 7:58 pm
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Dave, the reference to the oven is how I normally get bearings or bushes out of a case, the bearings normally just drop out with no assistance.

You could be right on the needle roller, although the edge of the needle roller showed signs of crushing, it looked to have over heated in one spot and had cracked around the edge. I won’t rule out cracking but the bearing with the original crank didn’t have this and the different needle roller that I use now and sits further into the case hasn’t caused a problem either. The difference in the crank was when Devimead did the original crank they machines off the .020” step/thrust face from the crank web. The new crank didn’t get this despite the engineer having the original as a pattern. It’s worth adding also that the original crank in the same cases with the same bearing type had a lot more than 0.020” end float. I think the 1st and 3rd picture shows the bearing damage. The new bearing being sunk into the case further probably gives more room for whipping at the cheek end of the crank.

The mega cycle cam measured .004” over side on the timing side of the case only when compared to 3 other cams and to the drive side end. I needed to run a reamer through the timing side bushes until I had sufficient clearance.


beerchug
Re: Crankshaft shimming [Re: Allan Gill] #791565 11/28/19 10:20 pm
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Originally Posted by Allan Gill
the reference to the oven is how I normally get bearings or bushes out of a case, the bearings normally just drop out with no assistance.
Allan, I've seen a quite reasonable argument that it is better to start with a cold oven to avoid the risk of distorting fine features of the aluminium alloy part, so I've taken to using that approach. The article was in reference to die cast Japanese engines, which do have much finer casting features than our BSAs, so I can also appreciate the merits of your pre-heated oven approach.

It does take much longer, and possibly a slightly higher temperature, for the bearing to drop out with the initially cold oven, so I may well go back to pre-heating.

Re: Crankshaft shimming [Re: CarpeDiem] #791569 11/28/19 11:46 pm
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Before i rant on,,,, i have the greatest respect for Kommando's knowledge regarding bearings and mechanical engineering.
He's forgotten more than i'll ever know on the subject. I also wish to state that i am not intentionally
out to offend or upset anyone, my approach apparently tends to do this.

Compared to the norton crank, the a65 unit has nowhere near as much flex.
If you look at the journal diameters and 74 mm stroke plus it's one piece forged construction it's evident.
There are hundreds (maybe thousands) of needle roller converted a65 a70 variations around.
There are even more standard bushed motors around too.
I've put together some pretty rough end fed ones and never seen that problem before.
Indeed i've built some rough ones myself and raced them with some success.
I've also run a norton 360 deg crank in an a65 with needle timing side as well as 76 and 68 and 180 versions.

I doubt very much that whipping or flexing of the crank caused that problem on Alans motor.
It would have shown up when i used a 360 norton crank far more so than on Alan's standard a65 one.

I've just looked up the bsa specified end float it's 1.5-3 thou.
That means at running temp of say 90 degs? it will be at least 5 thou probably a fair bit more.

For that bearing to have chewed into the crank like that i'd be looking for something more than
a thou or so extra endfloat. The main bore alignment and individual bearing bores as to parallel
would be first.
Just my 2c.

Re: Crankshaft shimming [Re: CarpeDiem] #791570 11/29/19 12:20 am
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That bearing looks like it failed because of excess preload, caused by the 20 thou step on the crank.


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Re: Crankshaft shimming [Re: gavin eisler] #791587 11/29/19 4:35 am
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Originally Posted by gavin eisler
That bearing looks like it failed because of excess preload, caused by the 20 thou step on the crank.


Yes i see that but surely he would have noticed when assembling that the crank was tight or no clearance at all.
The one hot spot indicates misalignment or even a slightly bent crank. Even so it must have been very tight to turn on assembly.
Surprising it didn't push the needle race through the timing side casting as there is only a thin lip there when machined for a needle race.

Re: Crankshaft shimming [Re: CarpeDiem] #791591 11/29/19 7:32 am
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I have to admit Nick that when I first got the motor back from the machine shop (crank fitted but not rods etc) the motor would spin fine with the outrigger on but was stiff to turn without the out rigger. After having the work done at a place where their work is usually of a very high standard I never gave it another thought. On hind sight I would have taken it back and said to machine the crank as per the original, but I carried on building surrendering to someone with more knowledge on engineering. Obviously tightening the outrigger nut was pulling the case somewhat allowing for more clearance. Which is why the crank could spin....

But would that then pull back when the case is up to temperature or has the crank grown?


beerchug
Re: Crankshaft shimming [Re: CarpeDiem] #791592 11/29/19 8:37 am
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In my experience the hot end float is always greater, i've measured it a few times.
Post mortems like this are always difficult especially when being done with no 'body'.


I remember Alex saying he had a similar thing on his bike where the drive side bearing
pushed out through the case. This has happened on one bike i worked on but it was due
to timing side thrust washer coming adrift and wedging down in between the crank and case,
that pushed the drive side bearing out. I suspect that was due to too much end float allowing
the washer to come adrift, but that motor was built so badly it's hard to say.

Re: Crankshaft shimming [Re: NickL] #791595 11/29/19 11:31 am
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kommando Online Content
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Originally Posted by NickL
Before i rant on,,,, i have the greatest respect for Kommando's knowledge regarding bearings and mechanical engineering.
He's forgotten more than i'll ever know on the subject. I also wish to state that i am not intentionally
out to offend or upset anyone, my approach apparently tends to do this.


No offence taken wink , just throwing out a grain of sand in case it draws out a potential solution. Too much knowledge can sometimes limit your thoughts from personal experience. Will continue to add the odd grain now and again.

Re: Crankshaft shimming [Re: CarpeDiem] #791600 11/29/19 1:07 pm
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Joining the conversation; I originally used a combination bearing on both A10 crank and Norton crank in my motor, with the Norton crank the combination bearing would move, I had countersunk screws trying to hold that bearing and it wouldn't stay put. To try to fix it meant splitting the cases, why I went to a straight heavy series Nkis 30 roller and used the outrigger bearing to control end float and crank position. If it stuffed up it was just under the primary cover and easy to get at, no more splitting cases.

It masks the timing marks so before fitting the head I set the engine at where I want a cyl to fire and drill through a hole in the bearing mount into the alternator and mark both cyl positions for strobing doing one big and one little can differentiate between left and right cyls or putting red paint in one hole if they are drilled the same.

The NKIS 30 I first fitted was std clearance a little crush of the case and it was a bit tight fitting, years later I had it apart and checked main bearings, The Norton Drive side roller had excess up and down play, the needle roller was still a bit tight. So I replaced both, the needle roller this time in C3 clearance to account for the slight crush. That type of needle roller has never moved in the case, and I expect because it's not the bearing taking side thrust. While the outrigger bearing is fully captured and cannot move.

I've seen another type of roller conversion stuff up because the L/ends were pushed out of the rods because the crank was so far to one side and the rods were pushing hard against the piston bosses.


mark
Re: Crankshaft shimming [Re: CarpeDiem] #791655 11/29/19 11:37 pm
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NickL Offline
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I rather liked these https://www.skf.com/uk/products/rol...edle-roller-bearings/productid-NKXR%2035

Didn't use the radial roller, made a bronze thrust washer. So limiting speed was NA. Available in c3.
We used to cut a small notch in the flange and pin it for anti rotation.
Did the job very well but an expensive bearing.

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