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Layshaft Woes


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Hi Mike,

metal spray or chrome plating and then grind to final finish would work.

Better still buy a replacement shaft (not expensive) get it it harness tested (not expensive) and then if too soft get it Nitride hardened

 

Be careful when doing the hardness test. If you do the normal Rockwell 'C' it will apply a load of 150Kg and not only measure the surface but more significantly the parent metal. With case hardening you really only want to measure the top .010 or so. So use a superficial HT that applies apprx 1 or 2 KG.

Most airfields will have some engineering that can do it.

 

Roger

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Roger: For me if Rimmers are not playing ball! I would be looking at going to the Small Claims Court for a consequential damages claim. I know from my 20 claims that I have done to date, yet to loose one that will soon focus Rimmers on this claim. Directors do not like being shown up as bad boys! By the way this part is easily made by a competent machine shop, we are not in the Rocket Science area here. Note: the TR Gear Box Guru has a copy of the BL drawing for this part, so you s/b be able to get a copy off him? The only other point make it out of EN40B grind to 0.002 to 0.003" oversize and nitride harden it to a depth of 0.020" and finish grind to size. Simple.

 

Bruce.

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I would not use sprayed layers, like High Velocity Oxy Fuel (HVOF), it tends to scale off under load.

I agree to do what Bruce lined out; final grinding after nitriding, since this treatment will give (slight) deformations.

Question is if the average TR enthusiast should need to worry about this!

Waldi

Edited by Waldi
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Hello

This Laygear has run about 30,000 km. in 3 years.

Then total failure.

Diameter incorrect.

Hardness not correct.

Supplier Laygear is from Germany

Oil was changed every year.

75w / 90

Unfortunately, this is not an individual case.

 

 

Regards

Ralf

Ralf: Do you know where these were made? I have measured an old BL one in an unworn area and it comes out at 13/16" old bar stock, which is 20.6375 mm o/d. So your figure shown looks to be 0.010" approx. under size? Therefore, I would still go back to your supplier? But looking at the damage was it ever harden?

 

Bruce

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When I returned to the TR fold a couple of years ago after a 20 year absence I was both amazed and delighted at the availability of reproduction parts, having spent the last 2-3 years rebuilding BUO using said parts I can now say that I'm disappointed and angry at how shoddy a number of these parts are. Not sure what is worse not having the repro parts, so you tend to look after/refurb the old parts when they fail, or having access to reproduction parts that sort of fit/sort of do the job.

 

BTW Anybody fitted the reproduction headlamp bowl kit from Moss recently...............they need to provide kevlar gloves in the kit to protect your hand from the razor sharp (literally) edges. :angry:

Edited by Graham
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Roger I would happily take my hacksaw to Rimmers if it were closer not sure they would appreciate that though, when I get a chance I will fill out the parts quality for it may help others in the future.

 

I now know that the design of the lay gear bearings is not up to the task but the gearboxes must have originally performed adequately for a good milage before the layshaft was worn through the hardening, so does it mean that hardening techniques back in the day were better than now, surely as an engineering feat it can't be that hard a task. (no pun intended)

 

Chris

Chris: my lay shaft which was original BL was 44 years old and had done 96k. before it wore the hardening on one end! Apart from the hardness issue, if you go for the 3 needle bearings mod to the lay gear as per Stag and a lay shaft from ORS, I am told that these parts will last well past 100k!

 

Bruce.

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Chris: my lay shaft which was original BL was 44 years old and had done 96k. before it wore the hardening on one end! Apart from the hardness issue, if you go for the 3 needle bearings mod to the lay gear as per Stag and a lay shaft from ORS, I am told that these parts will last well past 100k!

 

Bruce.

Bruce they obviously made things to last back then but I bet they were made to a tight budget at the same time.

Niall spoke of ORS earlier in the thread looking on the web I see Revington TR also do an uprated kit.

 

Ralf that was how I found mine in 2016 had owned the car about a year didn't think I would be doing it all again now.

 

I would love to have the hardness tested if I can find somewhere to have it done.

 

Chris

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Hi Chris,

there are a great number of companies all over the country doing NDT and Hardness testing.

Just google Hardness testing or NDT Facilities.

 

Where abouts are you. Most small airfields have an NDT facility.

 

For case hardening you need a superficial testing machine (apprx 1 - 2 KG force. Not the full Rockwell 150Kg)

 

Roger

Edited by RogerH
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Let the supplier know that there are many forum readers aware of this issue. Let us know what their final response is. Power to the people!

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Hi Chris,

would it be worth getting another new one and hack sawing one the counter. Could be interesting.

 

Roger.

Hi Roger! I have just come back from local machine shop. I gave my old lay shaft of 44 years of use and 96k miles! The hardness layer was starting to wear through on one end only, the usual place. He is RR Aerospace approved, he spoke to another company that makes gear box parts and they would not use EN40B steel nitrided as needle roller bearings do not like this type of hardening, as it has a habit of wearing them out very quickly, this was based on their own experience with an old 1930s gear box. They would still go for the best case hardening steel with a depth of .010" minimum hardening.

 

Bruce.

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Hi Roger and Bruce,

I would not know the difference either, to be honest.

Needle bearings can run against hard chromed shafts, bronze bearings, ...

Maybe material selection has to do with friction, the needles should be rolling, not sliding?

Did you talk to google?

Best regards,

Waldi

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Hi Waldi,

had a quick look through Google but I think it is such an obscure problem if it exists.

It did show that Nitriding produces a very thin layer of some odd stuff that may need removing.

 

However Nitrided crank shafts have no problem in their shells.

 

Roger

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Hello

 

if the tread is lapped after nitriding everything is done. It is exactly the same process as on a crankshaft. Gas nitriding is more suitable for the surface. nitrating salt bath is not so nice in the surface. slightly abrasive in the surface without lapping. is rarely made here in Germany. not so good for the environment.

 

Best regards

Ralf

Edited by Schnippel
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