WW1 Thornycroft restoration

[Old Bill]

The pitting is a ring just level with the top of the piston. Unfortunately, the piston was on the down stroke with the crank at about four o'clock so although the scraper ring will remain below, the top rings will run over it every time.

 

The pitting is quite deep so a +30 thou cut (60 thou on the bore) might not take it out. There isn't enough metal there to re-line it to orignal size as it is only around 1/4" thick just below the water jacket and we don't know what the corrosion has done inside. I must have a word with the cylinder coating people mentioned by Thumper above and see what they can do. I don't think we can metal spray the bore but it might be possible to build the piston up to match. I know there is a metal spraying expert on this site who might be able to offer some advice.

 

This job is going to need some serious consideration before cutting metal!

 

Steve

[Asciidv]

The cylinder bore coating process which has been referred to is less than 100 microns thick, is depositied electrolytically and essentially is only a plating. Not really suitable for building up such deep corrosion. The most common of this type of coating is 'Nicasil'. Very successful on two stroke racing cylinders where I first used it, but a total disaster for Jaguar when they used it on there V8 car engiines in the 1990's. (High sulphur petrol dissolved the coating resulting in 1000's of engines having to be replaced under warranty).

 

It is a problem, but I am sure Steve will overcome it, even if it means casting a new block!

Edited April 21, 2012 by Asciidv

[Thumpercross85]

Agreed, these coatings are thin and need to be correctly specified for the substrate & fuel, but when used in conjunction with welding etc to repair heavy damage first (eg broken circlips scoring barrels) can result in very impressive rescues of apparent basket case jobs. Having said that it is only one avenue to look at, and as others have suggested, various liner options may also be a very good solution depending on the wall thickness available in the original casting. The best answer will perhaps become apparent after showing the cylinder to a few of the guys who specialise in this kind of work but one thing is for sure, this engine will live again one way or another I have no doubt!

[Ted170]

Is it possible to use a smaller piston? If the casting is too thin to allow a liner to the original size, is it possible to bore to the possible maximum in the casting and then put a liner, whose walls are thick enough, gaining the thickness from the internal diameter, smaller piston? I guess the weight would be easy to achieve in this case, but maybe there would be some other problems?

[mattinker]

From memory, dry liners are 1.5 to 2 mm thick, with a band around the top of the cylinder, 3 to 4 mm thick. What diameters are the bores? It wouldn't surprise me if they are a standard imperial size. I'd take the cylinder and a good piston to some one who does reboreing, they may well be able to bore out and fit a standard liner from something else. Heavy pitting at the bottom of the cylinder would behind a dry liner would not be a problem. Even if the cylinder walls are thin, which I doubt, from that era, a dry liner shouldn't be a problem.

 

Regards, Matthew

[Great War truck]

With the ongoing discussions and deliberations relating to the corroded cylinder, we thought it appropriate to get it cleaned up now so that if (when) it goes on for re-boring, then it will at least be clean for the machinist to handle and there will be no delay.

Our usual procedure with this sort of thing is to get the oil and grease off first of all in a sort of paraffin bath - and then give it a good wire brushing.

The first two pictures show the block before we worked on it - but when it became cleaner, another problem became apparent - there is a crack in the block! Whatever next? We have had this problem before with the FWD and no doubt we can deal with it again!

 

 

 

 

 

 

To make life easier for the machinist when (if) it comes to re-boring, then we decided to remove the 5/16" Whit studs from the top of the cylinders to leave a flat surface. The studs were all absolutely solid and the only way to move these was by drilling them out.

 

 

[Great War truck]

It is difficult to drill out studs accurately "freehand", and in case anybody is not familiar with a way of doing it accurately, then this is the what we do!

We are dealing with 5/16" Whit studs here and first of all, they need to be cut back so that there is only 1/8" left protruding. We use a Dremel with a cutting disc for that purpose. We make up a jig (in this case) from an old bit of 1/2" steel bar - drill it right through initially 1/8" and then counter bore that hole to 5/16" for about half of the depth of the bar.

That 5/16" section will then fit over the remaining bit of the stud - and you can then drill the stud initially with an 1/8" drill - the jig will hold it accurately in the centre! That hole can then be gradually opened to tapping size is needs be and re-tapped. With a bit of care, you will be able to pick up the original thread with the tap.

That leaves the remains of the two pet cocks broken off in the top, and the two 1/4" studs just visible which retained a small bit of 1/8" steel bar designed to stop the Inlet Valve Retainers from rotating undone, to get out. And then there is the other Block!

In the last photograph of this series, you will notice the cleaning paraffin still leaching out from the crack in the Block over the Exhaust port.

 

 

 

 

 

[mattinker]

I like your stud drilling jig!

 

Have you heard of this kind of cold repair for Cast Iron?

 

http://www.locknstitch.com/Metal_Stitching.htm

 

 

Regards, Matthew

[Gordon_M]

Crying out for a stitch / Metallock repair, for sure. Might be worth getting the whole casting penetrant checked, as these things run quite a distance and you only want to do it once.

 

I think the largest repair of this type I've seen was a set of cast railway buffers by a train which had impacted them - totally destroyed but had to be pieced back together - not sure why as you would have thought they could just have replaced them.

[N.O.S.]

I like your stud drilling jig! ....

 

So do I - it is the simplest of solutions but I don't reckon I'd ever have come up with it! I guess this is the result of years of restoration of vehicles where few or no parts are available - ingenuity and lateral thinking is the order of the day :cool2:

[42 chevy]

Help with a clarification on a term: "Parafin bath" and "plus gas" I assume plus gas is a penatrating oil but I am at a loss on parafin bath. Thanks from the other side of the pond.

 

As always, brilliant work, always look forward to updates from your crew.

 

John G

[Minesweeper]

Just a different language! What we know as "Paraffin" - you Americans call ""Kerosene"! I wonder why that should be? Just one of those funny things from history, I guess!

 

"Plus Gas" is a penetrating oil and we have found it to be the best one that we have come accross. I guess there must be other brands - but this one seems to work the best for us!

 

Tony

[42 chevy]

Tony;

 

Thanks for the clarification on terms. I use KROIL brand penatrating oil with good results and SEA FOAM "deep creep" as well.

 

John G

[AUSSIE TD-40]

dont be to hasty to bore out or fit a smaller liner. The vintage engine blokes have repaired bores using JB WELD epoxy and then honed it out with good results.

The crack in the water jacket could be frost damage? or rust pushing out? think you will need the open it up there to have a look, best repair that is safe is gas brazing.

 

 

Jake

[nz2]

I have seen engine bores suffering similar pitting damage welded as a repair.

It was a skilled operator, with lots of pre heat to the block. I don't recall the type of rod or exact method used , but it was not a one off application, this chap having revived a number of vintage vehicle engines over the years.

A lot of people may frown at the idea, however it can be done.

Doug

[mattinker]

Interesting the different aproaches! personally, I wouldn't use heat!

 

Regards, Matthw

[Old Bill]

dont be to hasty to bore out or fit a smaller liner. The vintage engine blokes have repaired bores using JB WELD epoxy and then honed it out with good results.

 

Jake

 

That is an interesting one. How does the epoxy cope with the heat? I have tried looking at the JB Weld website but keep getting a German dating agency!

 

Steve

[Johnny]

According to their website, JB Weld is good for 260 Celcius /500 Fahrenheit. http://jbweld.net/faq.php

 

A quick google search brought up these links to bore repairs using it.

These seem to be mostly tractors, steam and stationary engines, but possibly not too dissimilar to yours!! :-X

http://www.steamengine.com.au/index.php/ic/faq/166-fixing-cylinder-bore-pits-with-jb-weld

 

http://www.mytractorforum.com/showthread.php?t=80087

 

http://www.smokstak.com/forum/showthread.php?t=39486

 

As your damage looks to be quite a way down the bore, and it's water cooled then heat may not be too much of an issue.

Is it below the travel of the rings? That may be a factor.

Edited April 25, 2012 by Johnny

[alixcompo]

So anyway.... How did you get on with the dating agency..? If any of them have a sister, mother, grandmother I could make up a 4some.....

 

 

(The work on the trucks is just awesome)

[wrward]

I have been following this thread with great interest. Another epoxy system to consider is the Devcon line of filled maintenance epoxies. They show steel filled as well as ceramic wear resistant grades. The Super 3000 grade shows heat resistance to 300C/572F and excellent gasoline resistance.

 

 

http://www.itw-devcon.co.uk/index.php?/devcon_mro/epoxy_maintenance_repair_and_overhaul_systems/devcon_hr_super_3000/

 

Keep up the fantastic work

[Asciidv]

My own experience of JB Weld is that it appeared to be no better than any of the other epoxies currently available. I used it on the external surface of a White and Poppe engine block which had turned porous. Within a season it had broken away from the surface, possibly due to differential expansion rates.

[Richard Farrant]

I have mentioned a product before on other threads, and that is Belzona. they have a range of products, which are used in heavy industry for repairs, quite often on engines. Because of the numerous types, it is worth contacting their technical people. Preparation is they key to these remedies. Luckily the lower part of the bore suffers less wear normally.

[broken arrow]

Hi,

Had some contact with Quintiq as Shoeburyness today and afterwards went on there site and looked at there historic images, look at picture 21, A J type THORNYCROFT with 13pndr 9cwt AA gun, picture taken at the range in 1917.

:-)

[Old Bill]

Another nice pic for the collection. Thanks for the tip-off.

 

Steve

[Great War truck]

Dad has been back at it after 2 or 3 days doing other things!

The first objective was to complete the removal of the remaining two studs and the broken Pet Cocks from the top of the first cylinder block. The one Pet cock was broken off at a level flush with the top of the cylinder - and with the hole in the centre already there, it appeared to be a prime customer for an "Easyout Screw Extractor" to remove it. And whilst the extractor screwed in very nicely, it became solid with the remnants of the Pet Cock showing no sign of moving at all. We certainly did not wish risking breaking off the Extractor in the remains of the Pet Cock as that would have made it even more difficult to get out - so the alternative was to drill it out using increasingly bigger drills each time until it became easy to knock the empty shell of the Pet Cock over with a punch and lift it out with snipe nose pliers. This left the thread undamaged in the Block but it needed to be cleaned up with a tap - 1/4" BSP and the 3/16" hole below it into the top of the cylinder cleared as that was totally blocked as well.

The other Pet Cock had already gone but the threaded hole for it was also blocked and needed clearing with progressively larger drills until it was possible to put a tap in it to clean up the thread and then a 3/16" drill through the bottom of the tapped hole into the top of the cylinder as that hole was also blocked.

That just left the two broken off 1/4" studs in the top and these were drilled out with an appropriate jig as described a few days ago.

 

 

 

 

 

There are still more corroded studs to remove from the first block, but we are just a little concerned that the second block might also be in a poor condition, so we decided to temporarily put the first block to one side - give the second block a quick initial clean so that we could see with what we are going to be faced with there.

These two pictures show the Block before cleaning and as it came off the Crank Case. More broken and corroded studs to deal with!