Worcester Boilers Eating PCB's

[geoff]

Up to the point where I've taken the money ...

[Andy Champ]

Well, it's the _second_ cam belt at 60K (5 year interval, not mileage based) but the only breakdown I've ever had was fixed with a new battery. So I can live without the 6k oil and brake shoe changes I used to do on my first car. A bit later than the 60s though.

Andy

[Dave Plowman (News)]

That's nonsense. I have the BMC workshop manual for the Sprite/Midget here and there's no such recommendation in the service section. Nor was it needed - I thrashed the bollox off mine for over 50,000 miles and it was fine.

Nor is there any point in changing bearing shells anyway as the crank wears too. You re-grind and fit oversize bearings.

The Midget didn't have adjustable wheel bearings. And the clutch actuation hydraulic. Many of the other things you mention were common to most makes.

[The Natural Philosopher]

Well yes, if you do it every 50K. Otherwise you do NOT need to grind the shaft. The bearings are soft white metal, the crank is super hard forged steel. In the spitire I would drop the sump, and a big end, and if there was the slightest hit of rock in the ends or any copper showing through the shells, do the bigends there and then, and it was just possible to do the mains with the engine in the car as well. By doing that I managed nearly 80K on that engine after a rebuild with no signs of crank wear.

Maybe it was a spitfire I am thinking of where the stated service interval for bearings was 15k or so.

IIRC you couldn't get the sump off a Spridget with the engine in place.

I wasn't being midget specific at that point: talking about generic routine servicing on 60's cars. Although I am fairly sure the midget FRONT axle bearings were indeed tapered roller and adjustable with a castellated nut and a split pin..but was working on so many MGBs, spitfires, midgets and lord knows what else around then, and it was a long time ago.

>

[Dave Plowman (News)]

The Midget was never fitted with white metal shells. Those were discontinued (on the A Series engine) in the '50s with the change to full flow oil filtration.

But the fact still is that a hard and softer bearing material wear fairly evenly. There is no point in just replacing shells. Especially since the crank doesn't wear evenly.

And it would have done the same if you'd left well alone. 80K wasn't out of the question by the '60s as oils and filtration had improved dramatically from the '50s.

The MGB didn't have adjustable bearings either.

[The Other Mike]

So I guess we'll never know...

[N_Cook]

Corporation has been working with our supply chain partners to find alternative lead-free solder solutions which do not contain tin (and therefore not at risk for tin pest problems). Potential substitutes include the addition of bismuth and antimony; however no long term scientific studies have been performed to determine if the use of bismuth or antimony do in fact eliminate the generation of tin pest in lead-free solder and in fine, whether their use would in fact adversely impact the environment . In addition, many printed circuit board manufacturers do not have sufficient scientific experience and tests results analysis in the use of these materials. In order to ensure reliable long term operation in a refrigeration system in which the equipment must operate, studies and reliability degradation tests must be performed on the use of lead free solder in low temperature environments and refrigeration systems.

To understand the phenomenon of tin pest it is necessary to understand the actual chemical change to solder when lead is removed and replaced with high er levels of tin. Tin is a metal that is allotropic, meaning that it has different crystal structure under varying conditions of temperature and pressure. Tin has two allotropic forms. "Normal" or white beta tin has a stable tetragonal crystal structure with a density of 7.31g/cm3. Upon cooling below about 13 degree C, beta tin turns extremely slowly into alpha tin. "Grey" or alpha tin has a cubic structure and density of only

5.77g/cm3. Alpha tin is also a semiconductor, not a metal. This transformation and resulting expansion of tin from white to grey essentially causes tin objects, such as solder, to crumble. .......

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Dave Plowman (News)" saying something like:

Cobblers. Replacing shells is a service item on many big diesels.

[The Other Mike]

On some engines you can't even (officially) grind the crank due to heat / surface treatments.

[Dave Plowman (News)]

Didn't know an MG Midget was a big diesel.

[N_Cook]

If normal tin stays above 13 deg then no tin pest will occur. It only takes one crystal to act as a seed , produced when the temp drops below 13 deg C though raises again. The die is cast. Then its a matter of how much cold/warm cycling or extremes of cold that determine how much and how fast it turns to powder. This is an extreme depiction , thinner specimens happens quicker, normal UK temperatures slower

[Grimly Curmudgeon]

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Dave Plowman (News)" saying something like:

It also applied to many smaller petrol engines.

[Dave Plowman (News)]

Not in my experience and I've been around car engines for a long long time.

The idea of ever changing shells as a service operation is nonsense. Of course, someone with a bee in their bonnet could change good shells and claim it was worth it. But by the time they do need changing the crank also needs grinding.

All rather pointless these days since this part of the engine will last the life of the car - generally.

[Andy Dingley]

[[citation-needed]]

Fiat Twin Cams, 1960s vintage - one of (the first?) the first mass production engines to use a nitrided crankshaft, and of course in those days lubricants and shell metallurgy were rather poorer. The bearing shells (mains and big ends), as explicitly stated in the owner's manual, are a service item at 25k miles. At 75k the crankshaft should be inspected and possibly (the manual suggests likely) required to be lightly re-ground. The nitrided crank could permit two regrindings (i.e. an estimated life of 225k), provided that the regrinding was limited in depth.

[The Natural Philosopher]

How nice to find something useful being done at a university.

[The Natural Philosopher]

yes..there is some process that case hardens it isn't there.

[The Natural Philosopher]

Haynes said to so it so I did, and got more out of that engine than any one before ..

That is true, today.

Only a few commercial diesels that really do half a million miles might be expected to have a shell change at 250,000.

[Dave Plowman (News)]

Haynes? The usual take it to your garage bit?

I'd rather believe the BL workshop manual.

[Jules Richardson]

Hopefully better than Triumph ones, which were riddled with errors and inconsistencies :-)

[Dave Plowman (News)]

They all are. But nothing compared to Haynes.