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Regound TR4 Crankshaft - Maximum?


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Hi all, taken crankshaft from my TR4 for reground. The crankshaft has been reground before to 30thou under and the engineer doesn’t recommend taking anymore off. Does anyone have experience or advise on the subject thanks Brian.

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Morning Brian,

and welcome to our forum.

I've altered the title of your post to better identify the subject, hopefully this will get you more resonses, and will alos aid further

searchs in the future.

Hope this is OK?

 

John.

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  • John Morrison changed the title to Regound TR4 Crankshaft - Maximum?

Well, the 1st question is can you get 40thou under bearing shells ?

2nd would be is the crank case hardened, & if so how deep.

If yes to 1, & no to 2 then I guess it should be OK.

Bob

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As Bob says should be ok.

If it’s any help I won the TR Register championship on a standard Triumph crankshaft with -20 mains and big ends ground to -60 ( yup).

With the crankshaft throw being offset ground on the big ends to increase the length of stroke. ( hence -60). The crankshaft was lightened and balanced and Nitrited also. The car won the championship the year after also after the bearings were replaced (as the norm with race cars.) 
I did use a 6000 rev limit ( self imposed) with a 6500 rev limiter in case of “ red mist”, maybe you are thinking of increasing the rev limit. ?

Mick Richards

Oh!…-60 shells ? Massey Ferguson is your friend.

Edited by Motorsport Mickey
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1 hour ago, Lebro said:

 

2nd would be is the crank case hardened, & if so how deep.

Bob

Generally the cranks are not hardened.

These folk should stock whatever shells you need - and do the machining if required.

Moss have 11 brand new cranks (just arrived)  on the shelf - not cheap but very good.

TRactor parts   https://www.acornservicestractorparts.com/acatalog/4_cylinder_Petrol___TVO__80__85mm.html

Roger

Edited by RogerH
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The moss new cranks are £1449 and are a very good reproduction of the original.

The tractor cranks are £450 - this includes bearings and gaskets. 

It does not have the cross drilling on the big end journal

The rear crank oil seal is a very large lip seal that will fit the TR block with no issues.  I think the Chris Marx lip seal will fit.

No need for a forged steel crank.

Roger

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Has anyone cross drilled the big end on a tractor crank?
I wasn't after a new crank but interested what the difference was between the tractor and TR crank and what justifies the £1k difference in price between the two.

As for the 2 forged options it would take a whole lot of persuasion that these are justifiable on a road car given that many racers might struggle to get that past the domestic paymistress!

 

 

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Hi Andy

 the £1K difference between the TRactor crank and that of the Moss is down to quality.

The TRactor crank is fully manufactured in India for a bowl of curry. And is pretty good.

The Moss crank is cast and rough machined in India and then precision machined in Wolverhampton = expensive.  And is very good.

They are only the odd thou difference here and there but to make it as per TRiumph it costs money.

 

Roger

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About 6 years ago when I was rebuilding my engine I sent a PM to an Australian member (Trumpy3) about the use of Ferguson tractor pistons in the TR engine as I had read he, and other TR owners in Australia, had used such items because the high import duty (I think) of car parts in Australia. Agricultural vehicle parts had a much lower tax

I asked because I had just bought a set of tractor pistons and liners and wondered if I had made a mistake.

He said "no problem" and that although the tractor pistons had 4 (5?) piston rings he only ever used the top 3 and did not have problems. He also said (I think) that he used tractor crankshafts.

He used to race with this setup and had around 140BHP and reved  to 5800.
He did not mention cross drilling, but maybe I should PM him again to try to get a bit more info.


I see the tractor rear oil seals are £7ish and I wonder if all that is required is a mod to the two ally "Scroll things" that bolt to the block in order to get the seal to fit.
The tractor crank has no scroll that has to be machined off.

Charlie.

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1 hour ago, RogerH said:

Hi Andy

 the £1K difference between the TRactor crank and that of the Moss is down to quality.

The TRactor crank is fully manufactured in India for a bowl of curry. And is pretty good.

The Moss crank is cast and rough machined in India and then precision machined in Wolverhampton = expensive.  And is very good.

They are only the odd thou difference here and there but to make it as per TRiumph it costs money.

 

Roger

Given the difference in cost I am surprised Moss don't get the machining done in India.

I know we all berate the quality of parts but it should be possible to get things machined to the required standard in India in the same way we talk down Chinese quality when the real problem is the specification and price demanded by the customer.

However £1000 for final machining seems quite a lot. perhaps I am over simplifying it but what are they doing on that final machining? Journal grindings to specific size, balancing or is it more than that?

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Hi Andy,

I followed this project from start to finish and know that Moss were seriously concerned about the final quality if completed in India.

We did some very clever things to ensure it would be spot on - cheap was not on the agenda.

I agree that in theory you get what you pay for. But if the project was fully completed in India what final cost would be acceptable AND what would paying customers think

when they see 'Made in India' on the box.

We were trying to get the product to cost around £1000 over the counter. 

This may have been sensible in 2013 (project start) but as time went on various costs  went up.

So by the time the cranks were ready for sale (apprx 2019) the cost was apprx £1200. For a quality piece of kit this is a very good price.

Over the next three years the price has gone up another £250.

So we have a significant piece of the car - costing £1450.  If you do not have one  how far will your £30,000 TR get down the road..

Cranks are slowly disappearing. So like the  4 pot cylinder head we/Moss  have secured another part that will keep the cars on the road.

 

Roger

 

Roger

 

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26 minutes ago, Andy Moltu said:

I know we all berate the quality of parts but it should be possible to get things machined to the required standard in India in the same way we talk down Chinese quality when the real problem is the specification and price demanded by the customer.

However £1000 for final machining seems quite a lot.

And that would effectively remove our choice of price v quality Andy, and result in two cheap-and-cheerful parts and nothing better. You already have the cheaper option to buy if you want. 

£1k more for a quality part seems entirely reasonable to me given the costs of setting up for small batches, doing it right, and of paying people a decent living wage. 

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That wasn't the question.

If it's essentially the same crank with the final machining done in the UK, I was wondering what specific machining is done. Given that there is a certain price for a crank regrind, a price for balancing. Are they reshaping the webs, putting on a scroll?

Is the casting blank significantly different quality to the tractor item or the same one with different finish?

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Hi Andy,

 

The Indians machined all the surfaces down to within 1 or 2mm of the correct size

from memory the following happens in the UK machining -

The UK Workshop  then took all bearing surfaces down to the finished dims and the ground to a perfect surface.

The webs were machined to the drawing dims

The scroll then cut in. The scroll is standard. The Chris Marx lip seal can also be used.

The oil galleries then drilled into position and grub screws fitted

Big end journals cross drilled.

The whole thing is then balanced

I'm sure I've left stuff out

Roger

 

 

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The Ferguson tractor had its engine limited to about 2000 rpm.  If you tootle around in your TR using a maximum of about 3500, a tractor crankshaft would likely survive a very long time.

However, if you use the TR's performance as intended, then you really need a cross-drilled crank because, as was demonstrated when testing the modified Vanguard engine, you are asking for trouble.  Read my 2-part article in TR Actions 241 & 242 (March & May 2010) for details.

Roger and Ian Brown were the Spares Development Fund (SDF) guys who undertook this project.  The work involved the testing of the quality of the material of the crank, having it laser-scanned to ensure engineering drawings were produced such that it would be dimensionally correct, and that the cross-drillings and other features were replicated faithfully.   The project was then handed to Moss so that ALL who might need a proper TR crank would be able to purchase from a trusted source - it's not just TRs which use TR engines.

What you will get with the new crank from Moss is a product at least as good as the original TR crank.

Ian Cornish

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Just asking out of interest what the difference was.  Partly from remembering spending some of my student summers working on a farm driving a Triumph engined tractor and wondering what the differences were. (Had to make do with a Spitfire back then)

Interesting how prices go up. Also surprised that the engineering couldn't be completed in India.

When the remade cranks came out there was only around £300 difference from a forged crank.

3 or 4 years old that has grown to £900. 

Hopefully mine has a bit of life in it. Forgot I was still running in, hitting 6000rpm when overtaking a Tuareg that pulled out in front of me!

 

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Hi Andy,

cranks haven't been forged for a very long time.

Fully machined billet steel or cast as per the TR crank.

If you wanted the Moss crank machined in India to the UK standard it would cost not a lot less.  You pay for what you get.

 

Roger

 

 

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On 5/16/2022 at 12:56 PM, Motorsport Mickey said:

As Bob says should be ok.

If it’s any help I won the TR Register championship on a standard Triumph crankshaft with -20 mains and big ends ground to -60 ( yup).

With the crankshaft throw being offset ground on the big ends to increase the length of stroke. ( hence -60). The crankshaft was lightened and balanced and Nitrited also. The car won the championship the year after also after the bearings were replaced (as the norm with race cars.) 
I did use a 6000 rev limit ( self imposed) with a 6500 rev limiter in case of “ red mist”, maybe you are thinking of increasing the rev limit. ?

Mick Richards

Oh!…-60 shells ? Massey Ferguson is your friend.

Mick,

How does this work in practice, is the stroke increased at BDC, rod length & piston stock.

Andy

 

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1 hour ago, andyhall said:

Mick,

How does this work in practice, is the stroke increased at BDC, rod length & piston stock.

Andy

 

There are different approaches Andy, the crankshaft has it's bigend  reground within the limits of it's bearing core dimension, ie standard or -10 whatever. Taking the centre of the big end further away from the actual centre of the crankshaft. So you need to source larger big end shells that will still work with the finished big end bearing surface, in my case -60 Massey Ferguson. The crank offset using standard length rods and piston compression heights (machined to work with the block deck height) and has the effect of increasing the stroke.  

Try this youtube for descriptions of rad ratio.

https://www.youtube.com/watch?v=C_YNn3ZkJmU

Mick Richards

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You would not believe what was done to those Lambrettas that used to come out of India (or maybe they do!) so am pleased that these crankshafts are finished off in the UK. I am sure that if Roger says they are as good as original then they will be.

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