Crankshaft drive side wear (solution?)

There are a number of engine repair companies around who can do hot metal spraying (or Thermal Spraying) onto worn crankshaft journals and then regrind them to bearing size. It is not cheap.....generally £50 plus per worn chunk. But cheaper than hunting down a crankshaft and getting that up to specification.

Checkout this UTube link for a demo on how it is done and marvel at Mr Fixit wearing full protective gear except in probably the most vunerable of places.

Is it too far gone for Loctite bearing fit? That is what they make it for.

Previously steve_leece wrote:

Hi all just aquired a 72 Combat engine 750 project.Whilst renewing the rear sprocket,i decided to replace the gearbox sprocket aswell.When all disassembled i found tiny up and down movement on the cranshaft. Oh dear! On total strip down to investigate i have found that the crank has been fitted with superblend bearings ,but that the inner race on the drive side was spinning on the crank. After removing the race i discovered that the shaft miced in at 29.94mm and had been centre punched to acheive a tight fit on the race, however this had worn smooth,hence the play.My question is. Is this a new crank or retrievable with some fancy engineering.

Cheers Steve

I once had the exact same problem on a Triumph. I measured the crankshaft to be between .003" and .0035" too small for the bearing. I got some .002" steel sheet (shim stock) and cut a piece out that wrapped around the bearing area then I pressed the bearing on. This gave me an interference fit. If I had had the money I would have got it repaired properly but I didn't. I don't remember any further problems with that crankshaft but it was a long time ago.

Here is a link to Loctite 641. They say "maximum gap 0.1mm" (0.004") and it looks like your gap is only 1/3 of that. Should be ideal. Probably.

Use loctite, not bearing fit, you want to use the Retainer grade. much stronger, 638 the number i think.

regards

peter

Peter - would '638' make it too difficult to remove? Does it really need the higher strength and temperature rating? Just curious...It does look like 638 will fill a bigger gap but 641 is for where disassembly is required.I have used 641 a couple of times but not taken them apart yet!

Greetings,

Pretty sure most Locktite products (Henlke) do not like Acetone or heat. judicious application of a hot air gun usualy does the trick.

http://www.loctitesolutions.co.uk/uk/productgallery/retaining/loctite-638.html

Data sheet here:

http://tds.loctite.com/tds5/docs/638-EN.PDF

Good luck & regards Steve

I had a similar problem on an Atlas crank some years ago and resolved it sucessfully using Loctite 648.

However if your 'superblends' have a C3 internal clearance, they rely on the inner race to be an interferrence fit on the crank journal to achieve the correct running clearance. You may find you still have some slight play after you have 'glued' the inner race on. If this is the case a bearing with either a standard internal clearance or even C1 should resolve the problem.

hi steve

check out T and L engineering they're in the bedford area

top men for metal spraying, we've been using them professionally for years for reclaiming crankshafts from the veteran/pre/post war days,

otherwise you can try hard chroming, cheaper than a new crankshaft surely

steve

Previously steve_leece wrote:

Previously james_brierley wrote:

I had a similar problem on an Atlas crank some years ago and resolved it sucessfully using Loctite 648.

However if your 'superblends' have a C3 internal clearance, they rely on the inner race to be an interferrence fit on the crank journal to achieve the correct running clearance. You may find you still have some slight play after you have 'glued' the inner race on. If this is the case a bearing with either a standard internal clearance or even C1 should resolve the problem.

Hi James youv'e got me there, could you enlighten please on the C3 and C1 bearings please . The timing side is as tight as a drum with the interference fit .If the C1 is smaller than C3 i machining may be the answer.

Cheers Steve Hi Steve, The C clearance will not alter the fit to the shaft as its the clearance between the inner and outer parts of the bearing. The clearance is afected if the bearing is a tight fit ON the shaft or IN the case.I have a problem with a rough running gearbox bearing which is too tight in the case,. A bigger C fit will solve this.

Previously steve_leece wrote:

Previously james_brierley wrote:

I had a similar problem on an Atlas crank some years ago and resolved it sucessfully using Loctite 648.

However if your 'superblends' have a C3 internal clearance, they rely on the inner race to be an interferrence fit on the crank journal to achieve the correct running clearance. You may find you still have some slight play after you have 'glued' the inner race on. If this is the case a bearing with either a standard internal clearance or even C1 should resolve the problem.

Hi James youv'e got me there, could you enlighten please on the C3 and C1 bearings please . The timing side is as tight as a drum with the interference fit .If the C1 is smaller than C3 i machining may be the answer.

Cheers Steve

Hi Steve,

As Robert just stated in his reply the higher the C number the greater the internal clearance between inner and out races for the rollers (or balls) to 'rattle' around on. You fit the outer race to the crankcase by heating the case up, when it cools down it will effectively crush the bearing and slighly reduce the internal diameter. Similarly when you drift the inner race onto the crankshaft, because it's a tight fit (or not in your case) it will slightly expand. The net result is a reduced running clearance for the rollers. With a C3 bearing the design boys at Norton calculated that this net clearance would be correct for a running engine.

Hope this helps Jim