Crankshaft repair, advice sought.

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kommando said:
I have corrected my post ref the driveside bearing, still John Hudson (not Nelson) recommended reducing the fit to a siding fit on both sides on the main bearing journals to allow for easier subsequent dismantling as detailed in the NOC Commando Notes.

You'll need to frequently dismantle if you follow John Hudson's advice.
Just as a by the way, I've used an old feelr guage for shim stock to get exactly what I wanted. Jim, diesel cranks get welded all the time and if they have the right oven to temper them it should not be a problem. You would not want that done in a shop without the right equipment though.
Reggie said:
Just out of interest Flo where would I get a metal shim for this job, as I am intrigued as that sounds a possible cheap fix?
Most bearing supply shops or machine shops sell shim stock in sheets. Cookie's idea of using a feeler gauge sounds good as you can get the exact thickness although you may have a problem getting a long enough one.
JimC said:
kommando said:
I have corrected my post ref the driveside bearing, still John Hudson (not Nelson) recommended reducing the fit to a siding fit on both sides on the main bearing journals to allow for easier subsequent dismantling as detailed in the NOC Commando Notes.

You'll need to frequently dismantle if you follow John Hudson's advice.

John Hudson (or Tim Stevens) does not actually appear to give that advice in the NOC Service notes for the drive side bearing, -not that I can find anyway! Tim Stevens does recommend doing it on the timing side (see paper pages 4, 14 & 34 of the service notes ... _Notes.pdf ).

However John does say in his NOC engine rebuild video (this pre-dates the Mick Hemmings NOC video) that the shafts should be "eased down" with emery tape if the fit was found to be too tight?
And if you watch his video where he attempts to extract an inner bearing race from a crankshaft with a bearing puller, and a chunk of bearing lip breaks off because the race was too tight on the shaft, then I think it can be understood why he would recommend doing this!
I agree with LAB about John saying that the shaft should be eased but not to a point where the bearing is loosely sliding over the shaft . 15 years ago John stayded at my place for 3 wheeks to show to our NOC members how to dissmantle and rebuild a Commando engine .The engine he rebuild then had its bearings on very tight and he did ease that shaft down to a point where the bearing went on by slightly tapping with a copper hammer .This was the drive side .That engine was thrashed for about 30.000km before it came apart again for inspection when bought by me and those bearings were still spot on .Btw no shims were used to clear out end-float although I always do shim on engines witch are to be revved.
John also radiused everything so no sharp edges could be found on anything(bolts bores castings crank etc).When I asked him why his reply was.NOW IT BELONGS TO SOMEBODY.He was a real gentleman and i learned a lot from him.
You may wish to consider electroless nickel. It is uniform in thickness unlike electro plating where high areas build up thicker than corners, etc. You can specify the exact build up you want and no post machining operations would be necessary. I have used this to build up undersized cores in my injection molding operation with great sucess. Mold Tech in Alabama also offers this service and the price is very reasonable. The process will not affect the integrity of the crank. I have included the opening paragraph from the Micro plating web site.

Micro Plating applies high precision electroless nickel plating and composite nickel coatings for industrial applications requiring, corrosion protection, high hardness, wear resistance, uniform thickness, and increased dry lubricity. Parts can also be masked and plated to salvage worn or mis-machined surfaces. Typical substrates plated include carbon steel, stainless steel, copper alloys and aluminum alloys. Typical thicknesses range from .0001"- 3" thick for mild corrosion protection up to .0035" thick for maximum corrosion protection in harsh environments or part salvage. With 100% coverage and uniform thickness, electroless nickel provides protection that few coatings can match. With a maximum processing temperature of 190ºF all substrates remain unaffected.

Chuck Poe
750 Commandos
I would avoid any plating process on a crankshaft. They are by their nature highly stressed components and hydrogen embrittlement is a real danger.
Electroless nickel is bot immune to embrittlement either.
I had the same problem some years ago on a Nourish crank that had the mainshaft slightly undersize, only .001" or so, as I recall. I had the area where the race fits hard chrome plated just enough to get to the low end of the original .0001" - .0004" fit. Because the plating was so thin, no grinding was required. The platers have enough knowledge about their plating rates to be able to get the specified thckness of chrome by adjusting the time in the plating bath. Also, with such thin plating, there is no risk of hydrogen embrittlement, as there would be if you ground the shaft undersize and built up a significant amount of chrome.

It worked perfectly, and the crank is still in use on a 920 race engine today.

I wouldn't suggest copper plating. I was told by the plating company, who had extensive experience with repairing crankshafts, that it would work for a while, but was too soft for a long-term repair.

I've also tried the Locktite bearing mount, and had the same experience. It won't hold for long.

Metal spray would also probably work, but I haven't tried it myself. From sprayed parts I've seen, it is rough enough that you would probably have to polish or grind it down to size.

Thank you all for the varied and learned replies. Certainly food for thought :? :shock: :?

bpatton wrote;
You didn't mention if this is the same bearing from the last rebuild or a new one

It was the same bearing. I will have to get around to measuring the bearing and the crank shoulder to see which item is definately at fault, but I am fairly sure it is the crank. Unfortunately, I have been a bit busy with work for the last few days to do this. I had never thought of the bearing possibly being undersize. The crank shoulder is very shiny where it has been spinning as you may suspect, and there is what could be described as "a flake of metal" missing. I will have to inspect more closely to double check this, possibly it has been hard chromed before?. I can't inspect at tthe moment as I am writing from work.

I'll take it to the local engineers probably next week and see what they advise. I have heard of turning the shaft down and putting a sleeve on before as comnoz says he has done, I was just concerned about weakening the shaft, but by all acounts, most remedies seem to have some trade off.

Thanks again.
I hesitate to weigh in here, with all the excellent advice, but hard chrome on undersize crank bearing journals and grinding the plating to size is the traditional repair in industrial motors.

Industrial crankshaft grinders usually have hard chrome facilities on site. As long as they have a grinder small enough for a comparatively small Norton crank, this job would probably be easy and fairly cheap. The only caveat is to make sure they maintain the shoulder to journal radius, otherwise, snap!

Don't ask me how I know!

Take the factory diameter specs. A good shop can get within .0002" of the mean dia.
This just shows you the many ways to skin a cat doesn't it? It may depend on what type of factors you have nearby and what friends you have. Since I have many friends in the big diesel rebuilding business I'd probably drop it off with a pal to fix, no matter which way you go I'd think it would work.
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