Rebuild bill determined by availability of VP2 k-series bearings

[Peter Carmichael]

Minister and Caterham can both supply the Vanderwell VP2 lead-indium bearings for the k-series. Minister's website quotes 118.80+VAT for a set.

 

I don't yet have confirmation that bearings are available for a 10 thou ground crank and I am waiting to hear from Minister.

 

If anybody knows of a confirmed supplier of undersize bearings, please let me know.

 

In the meantime, the crank is going to have to be ground to remove the surface damage, which it looks like 10thou will clear up easily - not sure what that means for the nitriding. Once ground it can be crack tested. These steps involve modest costs. Whether I can reuse it is down to bearing availability.

 

It may come to having to get a new crank, while the bearing industry catches up with the market opportunities presented by my attrition rate for fancy engine componentry. The block is modified for the oil paths in the Doug Kiddie crank, so I have to get another of the same (DKE has one on the shelf although I would want to know that it isn't Rob Walker's reject which has marginally out of spec crank pins), although I suppose it might be possible to run a crossdrilled crank with all grooved bearings for the mains so a Farndon would do. I suppose I could revert to the Rover and limit my revs to 8500, but I can not really see the point.

 

I am picking up the head on Thursday to strip it and inspect for any need for new valves. The inlet guides are being replaced, so there will be some seat refacing, valve lapping and a reshim at the end of all this work.

 

My timescales extend.

[R2D2]

Grinding 10 thou will remove the nitrided layer from the face of the journal so some of the wear resistance will be lost in this area.

 

The other benefit of nitriding is to improve the fatigue life of the crank by creating compressive stresses in key regions of the crank.

 

If the crank is EN40B and it has been correctly heat treated you should be able to re-nitride it without too much concern.

 

To fully develop the hardness needed after nitriding the component need to be hardened and tempered. This usually involves quenching in oil from 850degC and then tempering at 600/650DegC (approx).

 

This process usually causes quite a lot of distortion and is usually carried out in a rough machined condition.

 

The component is then "stabilised". This involves holding at a temperature of 575 DegC for at least a couple of hours. Final machining is then carried out. (Possibly a small grinding allowance is left on the journal but only a couple of thou.)

 

Nitriding then takes place at 550 DegC. nitriding leaves a "white layer" on the surface of the part which is usually removed by grinding.

 

If your crank has had the relevant stabilising process it should be quite safe to re-nitride. I would leave a thou or two on the journals re-nitride and then re-grind. The heat treatment shouldn't cause any more distortion and it is unlikely that you will overharden any other parts of the crank.

 

Sorry to bang on but I thought it was worth some explanation.

 

Edited by - chris flavell on 22 May 2001 16:39:03

[EFA]

Peter,

 

Doug and SRE both told me the nitriding is 20 thou deep, so you will have 15 thou remaining after the 5 thou deep (10 total) regrind.

 

 

 

Arnie Webb

The Fat Bloke blush.gif in a Fast Temporarily Indisposed Vauxhall wink.gif

 

See the R500 eater here

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[Tony Martyr]

Part of my misspent apprenticeship was spent in the nitriding shop of a gear manufacturer were post treatment honing and grinding were the norm. The benefit for crank shafts is that it gives a hard and toughened skin that is resistant to scuffing but if you keep the lubrication film you don't use it. The hardness progressively decreases after about 10 thou (imp) but the exact thickness depends on the section. Further hardness from quenching I have never done because of the distortion - the benefit of nitriding is its low distortion and normalising function. certainly post treatment grinding is required.

The 'Nitralloy' or En40 steel is a high strength steel and the forged version correctly tempered makes a good crank untreated. I would get a VPH check on the crank after remedial grinding and unless it is down to base hardness use it as is. I would certainly get it Magnaflux crack detected. Not dye penetrant.

[Rob Walker]

Peter the VP2 big end shells are only available in the one size Grade B. Glacier manufacuter -.010" and -.020" I understand. These are only in the standard plated material however. If you e-mail me off list I will give you full details of the crank DKE made for me. Caterham can supply you with a Farndon fully crossdrilled lightweight crank. This should present no installation problems as your block will only have been modded to take the tangs on the grooved shells. You will need to run 5 grooved on the top in any case. The Farndon crank is also 3Kg lighter than the DKE.

 

Edited by - Rob walker on 23 May 2001 07:10:16

[Peter Carmichael]

Rob,

 

Its not quite as simple as that, I'm afraid. The space for the offset tang on the plain bearing shells has been filled in to avoid the shells wandering sideways so I cannot fit the plain halves of the bearings. The rotational location of the shells is provided by a pin - one of the pair of bearings is drilled to accept the pinning.

 

With the Farndon is it it not a matter of running four (not five) grooved on top??

 

Despite the cross drilling, I suppose I could run the crank on grooved all round. The cross drilling would be to no purpose then.

 

The extra 3kg is an interesting consideration. Yes the Kiddie crank is heavy. That, I presume translates into more rigidity which is a good thing. It is possible that DOug is just being a bit cautious about the counterweight arrangement. The main bearings on my engine are just fine, so the grooved all round arrangement is ok with a stiff crank. The extra weight is irrelevant to the matter of inertia because I have proved able to get the inertia down with the clutch/flywheel arrangement. I have no need to go lower on inertia.

 

In that case I just have 3 extra kilos to lug around.

[Rob Walker]

3 , 4 or 5 on top that is the question????????? I am currently waiting patiently for Jez Coates to clear this one up. Minister have confirmed that they build the R500 with the standard Rover bearing configuration namely 3 grooved top mains on 2,3&4 and 7 plain on all the rest. On examination of the crank this bearing configuration effectively blocks off the oil feeds from 1main to 1 BE and 5 main to 4 BE which has confused me. I have contacted Farndon who have confirmed that the crank design was to run with a continous oil feed throughout the crank. So it seems as if its a trade off oil feed against greater bearing surface area/load bearing capacity. Aren`t you glad you left all this to Roger King.

 

The DKE crank I had made was not crossdrilled on either mains or crank pins. It had pin to main drillings and had a small groove machined around the mains to maintain oil feed to the big ends.

[Peter Carmichael]

From what I remember you telling me about your DKE experience, it was not the best and does not relate to my past experience.

 

I do know that in any machining process, having a definitive drawing to start with is crucial, including clear definition of all relevant tolerances. The quality checking of the drawing is the reponsibility of the engine builder, unfortunately, but it is a lot cheaper than quality checking the finished article and finding it to be wrong.

 

The DKE crank I had was according to a numbered drawing that I have not only checked over, but have also proven. If I get another DKE crank I will specify it to conform to the same drawing, rather than go through the process of checking the suitability of a drawing in detail again. (I am working on the physics of the reaction forces in the main bearings with relation to the amount of counter weighting to convince myself that the extra weight of the kiddie crank is saving my main bearings from getting a bashing.)

 

As regards your Farndon crank...

 

... you have four big ends and five mains. Ascertain where the ickle hole from each big end goes and you will get the answer to your bearing questions, surely.

[Rob Walker]

Peter,

 

One would think so, but it does not seem to be that simple.