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Author Topic: Big funny piston rings  (Read 2480 times)

mikenash

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Big funny piston rings
« on: March 28, 2020, 03:53:21 AM »
Hi guys

Our local machinist just failed Common Sense 101 (or at least his worker did)

I bought a 5slash6/1 recently with a long history of hard work on the farm.  Bottom end started out as a 3/1 maybe in the late '30s . . .

When I tore it down it turned out to have a +40 thou alloy piston (kinda an 8/1 now i guess) and the top ring groove was pretty worn.  I managed to buy some ring groove spacers in a suitable size as the 4&1/2 inch piston size was common in Bedford trucks & some other a half-century ago

So I calculated the clearance etc for the ring+spacer, WROTE IT ON THE PISTON WITH A PICTURE and gave it to the machinist we use at work.  He as been bloody good up until now

For whatever reason, he left it to a worker to do who mistook the vertical dimension for a lateral dimension and machined what could only be called A Very Big Groove into the piston

By the time I got it back it was one of those "what's done is done" situations

His solution was to accept that the piston now has a very big ring groove and to get a Very Big Ring machined by a bloke who makes one-off piston rings . . .

See pics?

What do you guys reckon the implications are?  I'd be interested to hear from some experienced folks

Cheers

broncodriver99

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Re: Big funny piston rings
« Reply #1 on: March 28, 2020, 06:59:44 AM »
That's a very big ring. Would suit a locomotive just fine. Does your 3-5-6/1 happen to be called the Dursley Express?

On a positive note there is likely little chance you will break that ring due to a cylinder ridge.
« Last Edit: March 28, 2020, 07:03:00 AM by broncodriver99 »

listard-jp2

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Re: Big funny piston rings
« Reply #2 on: March 28, 2020, 03:50:41 PM »

What do you guys reckon the implications are?  I'd be interested to hear from some experienced folks


Depends alot on what sort of wear ridge you already have in the cylinder bore, and where the top edge of the top ring is now in relation to the wear ridge (if you have any bore wear).

A company called Cords piston rings (in the UK) used to make piston rings for use in worn bores, and the top ring incorporated a 'ridge dodger'

Another alternative for you to consider would be to see my ebay listing of oversize Lister CS pistons (UK manufactured)  https://www.ebay.co.uk/itm/LISTER-CS-NOS-GENUINE-NOS-HEPOLITE-COVENTRY-PISTON-BACO-OVERSIZE-VA-6-1-8-1-/254185213781

mikenash

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Re: Big funny piston rings
« Reply #3 on: March 28, 2020, 10:36:49 PM »
Yes.  Good call.  No ridge - I have given it a hone and it's worn/loose but OK for an old CS

In the Current Emergency I'm not sure how internet sales are working?  However the company I work for is "essential" in the current lockdown so we have courier deliveries etc

If you wanted to look at a $$ figure inclusive of delivery to NZ for a cast +40 thou piston and rings, I'd be happy to consider it?

PM me if you like?  Appreciated.  Thanks

listard-jp2

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Re: Big funny piston rings
« Reply #4 on: March 29, 2020, 09:16:45 AM »
/\ If your interested, just do a Buy It Now on the ebay listing, and it will be shipped to you using the ebay global seller program.

No problem with ebay sales in the UK at present, sales are depressed, but are still happening.

dieselspanner

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Re: Big funny piston rings
« Reply #5 on: March 29, 2020, 01:40:56 PM »
Hi Mike

eBay Sale seem to be running OK as far as deliveries to the Pyrenees go. I'd guess a lot of vendors are small outfits that work from home. With the current situation I'm starting to catch up on all the 'projects' and bits are still arriving from the UK.........

As for the ally piston, I may have the answer, My 3/5/6/8 - 1 bitza started out as a 3-1 hopper cooled in 1934, according to the info plate. It arrived with the 5/6 - 1 top end and that's how I put it back together

When I ran it up it was tramping up and down the workshop like guardsman on rum. I stripped it down again went through the 38ac balancing routine and a couple of others for good measure, It looked like it needed masses of weight on the flywheels.

I sent off to Dev Precision, Rajkot, and within the week an ally 8 - 1 piston arrived, complete with rings, I fitted it and it ran up with no vibration whatsoever.

It starts to throw it's self around just under 700 rpm, where I have it at 630 it's as sweet as, under any load

I did ask on here, at the time, if there is any difference between the flywheels of the 3 -1 and the larger, later, CS but never got an answer. There's a significant weight difference between the ally and the iron piston so I'd bet a slab of beer there's something in the theory!

The Cs has been laid up for a couple of years, but if the C19 lockdown gets extended, in France, it'll be getting dug out for the fitting of the Land Rover starter motor I scrounged up a couple of years back.

I've caught up on the honeydew list and SWMBO would rather I was 100m away in my 'man barn', if I 'forget' my phone I'm guaranteed at least 3 hours of peace!

Stay safe, one and all,

Cheers Stef
Tighten 'til it strips, weld nut to chassis, peen stud, adjust with angle grinder.

cujet

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Re: Big funny piston rings
« Reply #6 on: March 29, 2020, 08:04:43 PM »
I've seen piston rings doubled up, much like the Total Seal rings. That generally does not work all that well, but it can work.

People who count on their fingers should maintain a discreet silence

mikenash

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Re: Big funny piston rings
« Reply #7 on: March 30, 2020, 07:36:31 AM »
/\ If your interested, just do a Buy It Now on the ebay listing, and it will be shipped to you using the ebay global seller program.

No problem with ebay sales in the UK at present, sales are depressed, but are still happening.

OK.  Cool.  I have ordered one of the 6/1 +40 thou pistons and that will give me a good spare at a reasonable price

My delivery address says "essential irrigation spares"  That's because, with the Covid virus, our country is in lockdown apart from essential industries - of which mine is one.  If the labelling says "essential" chances are couriers will deliver it.  If not . . . hmmmm . . .

I guess we'll see

Thanks for the various advice around rings etc here and there as well

listard-jp2

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Re: Big funny piston rings
« Reply #8 on: March 31, 2020, 09:31:00 PM »
/\ Your piston was posted today PM, you will be advised by ebay when it enters the global shipping program.


mikenash

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Re: Big funny piston rings
« Reply #9 on: April 01, 2020, 08:29:54 AM »
lol.  Thanks  :)