WW1 Thornycroft restoration

Yes, that is something that we have thought about in depth - but we do not think that it is something that we cannot cope with. I think it best that I leave it to Steve to fully set out our thinking as he will be able to reply to your question in greater detail and far better than I can!

Tony

I'm guessing the best way forward would be to try to achieve similar compression ratios (or similar max. pressures) - but how.....if they were individual heads it would be so easy!

By far the safest solution would be to reline all four bores.

You may even be able to pick up four suitable pistons and bore the liners to suit these. As there are no balance weights on the crankshaft it would not matter whether the pistons were alloy or cast. The only critical measurements are the distance from the gudgeon pin centre to the piston crown and the position of the scraper ring at bottom dead centre.

A commercial engine overhaul specialist should have a list of piston size data that may help you.

John

Well, that was unobservant of me! No idea - perhaps the initials of the Foundry that cast it?

 

Tony

Looking over the two M4 engines I have here, only one pair of cylinders has any similar casting marks. However it is not FN but what appears to be a symbol of Thornycroft.

7 2

_______

l

1 l 9

l

The vertical line of the T is a continuous line which I can't reproduce here. The 19 matches to that of the year this chassis was manufactured.( 1919) The 72 could be a casting date or code.

There are no markings on the neighbouring pair of cylinders, however there is noticeable a slight change in casting shape to this flanged area. I wonder if a set of cylinders has been replaced at some point in time.

This change is not evident on the other M4 engine, with both cylinder blocks being identical.

Did Thornycroft buy in castings of engines? For a company that produced such a number of vehicles for use in the war time, could these be cast as spares issue?

I am currently researching JAC ( Cattons Foundry) as their casting mark is about some parts on Thornycroft chassis parts and rear axle parts.

Who were FN? (Aside from the rifle manufacturer)

Doug :-)

By far the safest solution would be to reline all four bores. .......

John

Yes, at least the engine will be as balanced as the original. I'm guessing balancing was not a great concern in these old engines?

According to the Hampshire County Council web page Hantsweb http://www3.hants.gov.uk/thornycroft/lorries/basingstoke-factory.htm Thornycroft brought in castings and forgings from outside suppliers although they did machine them at the Basingstoke factory.

With most companies engaged on war work the demand for military equipment far outstripped the companies normal peace time production so probably during WW1 Thornycroft were being supplied by more than one foundry. Some form of identification would be required to trace the supplier so that any issues with unsatisfactory castings could be addressed before the next batch was supplied.

Sorry I can’t help with who FN might have been.

John

By far the safest solution would be to reline all four bores.

John

Yes, ideally, we would do all four. However, two of the bores are pretty good so I would rather leave them alone beyond honing them. This is a very large, low speed (1400rpm max) engine of only 40 hp so I think that a slight mis-match will make no discernable difference. I remain to be proven wrong, of course! In that case, the unmodified block could be lifted straight off the top of the crank case disturbing only the water pipes and manifolds. It could be machined and new pistons fitted to the rods without too much effort so I plan to go that way.

The pistons will be fun. I will make up a pattern and get them cast locally in iron. The fun bit will be machining the gudgeon pin hole as the lathe has only 2 1/16" over the cross slide so that is the maximum distance I can bore the gudgeon pin hole below the crown. I haven't measured the pistons yet to see what they are. I may be going, cap in hand, to see a pal who has just bought a new milling machine. You soon find out who your friends are in this game!

Steve

we made several years ago liners from GGG70 for a continental four cylinder engine which was bored out so often that it had developped a big hole to the water jacket. GGG70 is that kind of cast iron with a strength of 70 kgs/mm2.

It can be obtained with "ball" type and "lamellae"-type of carbon inclusions and for a combustion engine it gave in full

eight hour shifts some 14 years of troublefree use. The bores were cut out and the CCC barrel was pressed in with an edge

at the top pressed down by the cylinderhead and its gasket. Then the bore was remachined to its original dimensions, and a new original piston used. The liner thickness measured just over one (1) millimeter after the boring. GGG70 is a typical German nomenclature for the redeveloped high tensile strength cast irons.

2) when you have a crack in a casting why not weld it with a high strength wire ith a Tig welder? We have had always good results altough sometimes some hardening of th casting. Anyway very handy to make several parts from stainless, copper and gun metal. Even for soldering.

Anyway good luck with the beatiful resauration. Ours on the GMC slowed down a bit as a damaged my right hand a little, so I amtyping this with one finer on th left hand

kind regards

spitty

Thanks Spitty. It is great to have the benefit of your experience. I do hope you haven't hurt yourself too badly or that it puts you off old vehicles!

Welding is still an option and I have been fortunate to have the offer of a friend to do it. His plan is to warm the blocks very slightly and then use Nickle rods in short bursts to avoid putting too much heat into the job. At the moment, I really don't want to risk getting them hot but I am keeping the offer up my sleeve.

I have taken the day off today and have been to see Slinden with the blocks.Mr Russell was very helpful and said that there will be no problem stitching the cracks we can see. However, he has recommended that the water jacket be pressure tested with air to 20psi and soapy water to find any other cracks before starting the job. If there are any cracks in the combustion chamber, he would have to weld those and would rather tackle the whole job in one go. I have, therefore, brought the blocks home again in order that we can make up some blanking plates. He says that stitching costs about £100- per inch so I can see a substantial bill coming!

Steve :-)

Hmm, well he's the expert I suppose. I wouldn't let him go any higher than 20 psig, though ...

Useful to have a handle on the cost per inch these days. The block that was stitched for me had a crack over two feet long when he dye penetrant tested it ......

Hmm, well he's the expert I suppose. I wouldn't let him go any higher than 20 psig, though ...

 

Useful to have a handle on the cost per inch these days. The block that was stitched for me had a crack over two feet long when he dye penetrant tested it ......

Steve

Slinden services come highly recommended, they repaired the cylinder casting for a friends traction engine by fusion welding, similarly Cast Iron Welding services in Coalville, a bit closer to you were also very good at the same process on another friends cylinder casting.

The guy who had his cylinder done at Coalville initially tried stitching in situ, (we are talking 200psi steam), it leaked. Then he tried arc welding in situ (also leaked and cracked more), eventually he had to take it off the boiler and it was sucessfully fusion welded, the trouble is the earlier attempted repairs made the final bill more!, it actually got to the point that he may as well have had a pattern made and cast a new one the amount of money he spent on the job.

My advice is to say to Slinden that you do not want them to attempt anything unless they are 100% confident it will work. That is you would rather they didn't just 'have a go' or 'try something'. Tell them you want it done once, or not at all.

The fusion welded option will work, but costs a lot of money, and you will need to remachine most of it afterwards.

I've seen the metalock stitching process in action, whilst it seems to work, I cannot see how making the crack bigger, belting in a bit of tapered metal in that is trying to split the casting in two, and making new and similar flaws in the casting perpendicular to the crack is ever going to make a strong and permanent job.

Frankly I'd prefer to affix a sheet of copper over the external crack with some goo and some tapped holes and cheese headed screws to hold it all down, a thouroughly period repair.

The good thing about your cracks is that the pressure of the water is likely to be small. Are they actually leaking? small cracks often rust up? Another old remedy is salamoniac and cast iron dust in the water.

There was no sign of any water seepage through the cracks!

Tony

I had a leaking three inch long external frost crack in a Crossley water jacket and my only concern was the crack extending and circling round until a cast piece could drop out, which looked likely.

My preferred choice was to have it metal stitched to mechanically stop it from becoming a problem.

The process was very reasonable at about fifty pounds and to my mind relatively risk free.

I was advised to use a radiator sealant in addition to the metal stitching, the repair has worked well and has removed a nagging worry!

Metal stitching is a very old process and is currently being used regularly on the arms of dough mixing machines for which it is the most effective repair available.

Down the road a large mill steam engines cast base which had cracked has also been repaired in this way.

I hope this helps, but if do not have a leak and it stays this way when hot you should be OK.

Tom

There is a cooling system sealant called 'K seal' this has been known to fix leaking head gaskets and is a favorite of the motor trade. Scary (that it might be in the used car you bought last week) but very effective.

Hmm, well he's the expert I suppose. I wouldn't let him go any higher than 20 psig, though ... QUOTE]

 

Yes, that pressure frightens me too. It was never a pressurised system and I would hate to blow the sides out at this stage. I think softly-softly should be the motto here and top out at 10psi.

 

In all honesty, we could just leave them and live with the leakage but as the engine is so far down, it seems sensible to do everything now. I wish we had with the FWD as the cracks there leak as soon as the engine is operating and the silencer fills with water overnight if the system is left full. Don't stand close behind it when first starting in the morning!

 

Thanks Alix. I hadn't heard of that one.

 

Steve

Father took the opportunity today to get some bits sand blasted. Not all will be required immediately but the “blanking plates” to go on the sides of the cylinder water jackets will be required in connection with the planned pressure test. One of the cylinder side plates has a pin hole in it –it appears that the casting has just corroded away in that one place but that can be drilled out slightly larger and either tapped for a screw or drilled for an iron rivet.

The cleaned bits have been given a coat of Bondaprimer to stop fresh rusting.

What a great thread and your restoration is amazing! Doesn't it annoy you when you send something away to be sand-blasted or bead-blasted and when you get it back they have not quite removed all the rust? How much more time would it take for the blaster to go that little bit further and do the job properly? I hate it when that happens and usually send it back to be done properly. But then I am obsessive about rust.

What a great thread and your restoration is amazing! Doesn't it annoy you when you send something away to be sand-blasted or bead-blasted and when you get it back they have not quite removed all the rust? How much more time would it take for the blaster to go that little bit further and do the job properly? I hate it when that happens and usually send it back to be done properly. But then I am obsessive about rust.

Frankly cast iron is best left as it is. You often get a harder skin formed as the outer metal cools in the form, and this skin gives better protection and is less porus.

I expect those of you who have machined raw castings have found this hard skin in iron.

Grit blasting removes some of the skin.

All you really need to do with cast iron is to clean thoroughly, degrease, perhaps a light emery for a key and paint. Any surface oxidation present will not progress once painted. The covering of oxide actually protects the iron in a simlar way to the rust on weathering steel.

Steel is different kettle of fish however!

In an engineering recipe book I have, dated 1890, is the following for 'Steam Cement', a paste to repair cast iron castings

Iron filings, free from rust, 50 parts;

flowers of sulphur, 2;

pulverised hydrochlorate of ammonia,1;

These ingredients are mixed with water or urine, so as to make a solid and homogenous paste, which is used in the joints of steam boilers or flaws in castings. The cement swells and perfectly closes the joints.

There you are then.

Your 'blanking' plates appear to be aluminium (alloy?) and similar to my Leyland equivalents that are severely corroded with deep pitting on the inside. How would you prepare these for replacement? Would you consider an aluminium epoxy over a corrosion treatment? It could be machined flat. Alternatively, fibre glass? I have the same problem with the radiator bottom tank. Any thoughts? Robert

Your 'blanking' plates appear to be aluminium (alloy?) and similar to my Leyland equivalents that are severely corroded with deep pitting on the inside. How would you prepare these for replacement? Would you consider an aluminium epoxy over a corrosion treatment? It could be machined flat. Alternatively, fibre glass? I have the same problem with the radiator bottom tank. Any thoughts? Robert

No, they are not ali - all cast iron!

Your description of your Radiator problems is exactly the same as we encountered with the Dennis -very deep pitting within the top and bottom tanks and we were resolved at the time just to repair them - which we did by cleaning out all the aluminium oxide, plating the inside of the tanks and then sealing the gaps between the new plates and the old original aluminium tanks with Devcon, an aluminium putty. And then finally painting the whole of the inside with a couple of coats of an expoxy resin. We thought that there was no way of water penetrating through that lot again!

Now these aluminium radiators seem to be the perfect recipe for corrosion - a mixture of aluminium, copper and brass (unlike metals) - and then with the whole thing being continually flushed through with hot water when working so that you have an electrolytic reaction. At the time that we were dealing with this, an experienced friend who had previously dealt with other aluminium radiators said that we were wasting our time and that we would never be able to repair an aluminium radiator - the best thing to do was to make new tanks.

And although we were confident that the job was done and completed successfully, we found that he was right! Numerous fresh leaks - mainly pinholes appeared which we were temporarily able to seal from outside - and which are quite unsightly and we just wondered how that could have happened after all that trouble was taken.

So, on the list to do, is to make patterns for new top and bottom tanks to be cast as replacements. The whole story of this is related "chapter and verse" on the Dennis thread.

I am not sure what your plates look like, but if they are just plain aluminium, could you not cut some aluminium sheet to suit? If they are lettered or have a pattern of some kind cast in them, then bite the bullet and make a pattern and have some new ones cast!

Over the years, we have been collecting bits for the "Thorny" and waiting for us to get around to the job, we have all the new castings for a new Radiator - as we did not have an original!

Tony

Tony, how did moisture get between the Devcon and the top tank? Can you tell me the page number on the Dennis thread? Thanks. (I found the short Dennis rad. thread. The inside of that radiator looks familiar...)

Tony, how did moisture get between the Devcon and the top tank? Can you tell me the page number on the Dennis thread? Thanks. (I found the short Dennis rad. thread. The inside of that radiator looks familiar...)

Look at Page 3 - 27 Feb 2006 onwards - those early photos are not very good. And then look at Page 141 - 25 Apl 2011 onwards.

I would have thought that it would have been impossible for water to get through all that "fortification" - especially in the early stages of running - but it did!

Tony

Used to have similar porosity problems on a variety of castings we made for the Post Office. We sent them all to Glasgow where a company called CASTINGITE soaked them in some sort of sealant which penetrated and sealed any pores.

That was years back, may well not be in business any more, but did the job in those days.

Alas, no more;

http://ukdata.com/company/00495285/CASTINGITE-(SCOTLAND)-LIMITED

Another option

I will be sending a porous aluminium sump to these people next winter

http://www.impregnation.co.uk/catalog/sectors/automotive.htm

not expensive

Tom