Broken gudgeon pin - the update...

Broken gudgeon pin - the update...

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itiejim

Original Poster:

1,821 posts

204 months

Tuesday 6th October 2009
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Following my rather worrying discovery of a couple of disintegrating gudgeon pins http://www.pistonheads.com/gassing/topic.asp?h=0&a... I have an update:

I contacted the pistone manufacturer, AE and sent the piston and pin back to them for analysis.

They have examined, cross-sectioned and tested the pin at 0.1mm depths and accept that, to coin a popular phrase, they're st. The surface harness on the outside is OK, but the inside of the bore is massively under hardened.

They also noted that the end grind on the pin is very rough and that there is a crudely fashioned chamfer on the end of each pin which would also tend to weaken the pin.

I can only praise AE for their efforts and professionalism, unfortunately (for me) they state that the pin is not of their manufacture. Apparently it is extruded, a process they do not use, and also the internal bore is 1 mm larger than their design.

So, a couple of things:

1. AE has put me in touch with Pankl racing, a company which makes high quality products, including pins for all of the teams on the current F1 grid. They have agreed to provide me with a set of pins at a very competitive price. If anyone else is rebuilding an AJP I'd really recommend changing the pins, or at least examining them very closely. Certainly if they have any of the same characteristics of mine I would bin them immediately!

2. If anyone else has suffered from pin failure I'd be very keen to see a pin, clarify whether it's the same as mine and see if we can identify the origin. I was very lucky not to suffer catastrophic failure, however, I appreciate that others might not have been so lucky and I feel that there is a strong case for a bit of compo!

Sorry for the long post, but I thought that people might be pleased to hear the facts.


ridds

8,192 posts

243 months

Tuesday 6th October 2009
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Fantastic response from AE.

I'd be keen to hear about the price of these new pins.

julian64

14,317 posts

253 months

Tuesday 6th October 2009
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My cynic spidey sense is tingling.

If I only had a pound for the number of times a so called professional has rubbished another professionals work.

Ends up being a game of who you believe.

It does however pose the following questions.

If the gudgeon pins are as bad as you say, why isn't this a fairly common theme on the 1900 odd Cerbs that had them put it?

If most Cerbs seem to be doing all right on their current gudgeon pins then why didn't yours?

Need the answers to both questions before I go stripping down my engine to replace parts that may not have a problem frown

itiejim

Original Poster:

1,821 posts

204 months

Tuesday 6th October 2009
quotequote all
To be fair to AE, the pins went to them on the assumption that they were theirs. Therefore I don't really go with the "rubbishing other peoples work" thing. The engineer who oversaw the work was open and honest and conducted hardness testing throughout the thickness of the pin. It was only when AE sent the pin off to their supplier for confirmation that the pin had come from them that we discovered that they could not have produced them due to the processes used.

Having spoken to a few well known specialists, I am not the fist to come across pin failure. One specialist uses different pistons altogether, whilst another has an alternative gudgeon pin (not taper bored) which seems to have solved the problem.

I don't think for a moment that all Cerbs have this issue, however, neither do I think that mine is alone. I suspect that TVR either ended up with a duff batch, (perhaps AE outsourced the supply of pins in a time of need?) or alternatively they (TVR) bodged another pin to fit. Speaking to the guy from AE he wondered whether they were Jag pins which had been shortened. This would explain the rough ground ends and also the lack of hardening in the centre of the bore, which apparently was standard on some Jags a few years ago.

I wasn't suggesting that everyone go out and change their pins as a matter of course. I just suggested that if you're rebuilding an engine then extra attention should be paid to this (normally bomb proof) component. I would also go so far as to advise extreme caution if your engine starts making a load related tappety noise - my excess of caution has certainly turned a huge bill into merely a large one!

Ridds - YHM.

julian64 said:
My cynic spidey sense is tingling.

If I only had a pound for the number of times a so called professional has rubbished another professionals work.

Ends up being a game of who you believe.

It does however pose the following questions.

If the gudgeon pins are as bad as you say, why isn't this a fairly common theme on the 1900 odd Cerbs that had them put it?

If most Cerbs seem to be doing all right on their current gudgeon pins then why didn't yours?

Need the answers to both questions before I go stripping down my engine to replace parts that may not have a problem frown

plasticman

897 posts

250 months

Tuesday 6th October 2009
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I would also like to know the price and weight of the pankl pins , thanks , David

Bob Pistons

1 posts

112 months

Thursday 20th November 2014
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I know this topic is old, but I came across it by accident and realised I was the engineer at AE to whome the pins were returned. Just to clarify for those worried about the pins in their engines. The pins in this instance had obviously been crudely modified with very rough almost serrated ends and had clearly been bored out removing the case hardening in the bore of the pins. So just a bit of free advice if you want a lightweight pin it is not safe to take an existing pin and bore it out or shorten it. The reason is that the case hardening in the bore of the pin induces compressive stresses in the surface, this has a massive benefit on the fatigue life of the pin. Remove this layer and the pin will fail unless it is extremely lightly loaded. So if you have pins in your engine which have been bored out, after hardening, to make them lighter then I would change them before they fail. If you want a lightweight pin have one made from scratch in the correct material (class L,M or N) etc to ISO18669-1 and have a HT to give correct case depth core hardness etc and go for a growth limited pin.

aide

2,276 posts

163 months

Thursday 20th November 2014
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Epic first post!

Welcome and thank you for sharing.

Best wishes
Aide

jamieduff1981

8,022 posts

139 months

Thursday 20th November 2014
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Agreed - that's a very useful input. Thank you smile

steve320ise

159 posts

142 months

Friday 21st November 2014
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Thank for your fantastic input, so just to clarify on this. the pin you looked at had been modified which caused the problem, if so the standard unmolested pins should be fine, I have all my new bits here now and im going to start to assemble the engine so if there are any issues with them now is the time to put them right, cheers Steve