WW1 Thornycroft restoration

[Great War truck]

 

 

 

This was removed, revealing one of the two thrust bearings which has seen better days.

 

 

Then it was a case of waggling off the clutch spring centre, remembering that it was still hot!

 

[Great War truck]

The other bearing could now be seen, also a bit past it.

 

 

 

 

These will need replacing of course. We have had a look in our ‘useful huge bearings’ box but to no avail. Does anyone, by any chance, have a spare (or even two) LT2 1/2” thrust ball race that they might be prepared to part with please? It is 2 1/2” bore by 1” thick.

 

Father took all of the bits for sand blasting but this has shown up a crack between two of the bolts.

 

 

 

Now here, we would like some advice please. The crack didn’t stop the vehicle running. However, now we know it is there. It only goes through the steel and the iron hub behind is sound. The steel is 3/16” thick and will probably weld without much bother. However, the risk is that it will distort with the heat and we will end up with a wobbly clutch. Would you weld it or leave it alone? Finally, Father has primed everything to keep the rust at bay.

 

[Asciidv]

Well, I am going to vote Conservative - leave well alone!

 

 

Barry.

[racer]

Good evening gentlemen,

 

I would consider fitting a steel plate ring under the bolts and then rivet together or add intermittent "stitch" welds around its OD, just to strengthen the original material and dissipate the load.

 

I would also like to thank you for such an interesting restoration thread.

 

 

Andy

1925 Napier Lion

1913 Chalmers racer

[David Herbert]

I would be concerned that the cracking is more extensive than you can see. It is obviously caused by fatigue from the clutch being pulled in and out rather than the torque and if that bit cracked how far behind is the rest? Are you sure it is weldable? I wonder if it is quite a high carbon steel to give an almost spring steel and if so you could be causing more cracks by welding.

 

If it is easy to file it may well be weldable in which case I would consider cutting out the centre about an inch outside the bolts so as to get away from the area that has failed. Weld a disk of say 10mm mild steel in flush with the front (concave) face with a nice big mig weld on the inside first, then grind out the joint on the front and fill with more mig weld. Then the inside face of the new bit can be machined back to the correct shape to fit on the flange having centred it from the outside of the pressing. The holes can be drilled using the flange as a guide. The centre will then be a little thicker than originaly so should be tougher. It shouldn't be too hard to find someone with a big enough lathe to skim and bore the new centre and if set up carefully it will be dead true.

 

If on the other hand it is hard I think I would tend to leave it and drive gently.

 

Good luck

 

David

[Hoseman]

Good evening gentlemen,

 

I would consider fitting a steel plate ring under the bolts and then rivet together or add intermittent "stitch" welds around its OD, just to strengthen the original material and dissipate the load.

 

I would also like to thank you for such an interesting restoration thread.

 

 

Andy

1925 Napier Lion

1913 Chalmers racer

 

I could see this working, nice tight fit round the centre spigot OD and out past the holes with good tack welds to hold all together, pulling it all in. A fabricator friend makes new arms and buckets for excavators and has just started using a new type of steel. cant remember what its called but he only needs 1/3 of the thickness for same strength, Welds great and less weight too! He can build an arm for a 20ton excavator using 10mm steel onstead of 30mm!!!!!!

Find out the name and post it for everyone.

[mattinker]

I would be concerned that the cracking is more extensive than you can see. It is obviously caused by fatigue from the clutch being pulled in and out rather than the torque and if that bit cracked how far behind is the rest? Are you sure it is weldable? I wonder if it is quite a high carbon steel to give an almost spring steel and if so you could be causing more cracks by welding.

David

 

I agree with David about the cause. I would be very surprised if it is hardened steel. It's after all running in a warm environment! I'm not sure that adding a ring and tacking it on isn't just putting a weakening ring of welds further out. I would suggest, if it "passes" the file test for steel, to avoid deformation, either heat up the whole thing before welding, or weld short lengths and let it cool between welds. You have nice weed burner and I seem to remember a forge!

 

I think, a good weld repair would be sufficient for your uses!

 

Just don't blame me if it breaks!

 

Regards, Matthew

[fesm_ndt]

First off you need to ascertain the extent of cracking which is a very simple NDT job. MPI would be the easiest but PT (penetrant testing) would be cheap. As I think it's going up to the left also.

 

A very cheap way of doing a test is to put some red auto trannie fluid on it for half an hour. Wipe the surface clean then poweder on some talcum powder. The oil will blot out of the cracks. The PT mentioned above is a lot more refined but the same concept.

 

I am somewhat less conservative when discussing cracks. Depending on the material a proportion of stress raising occurs. If you hang 1 ton off a flat bar, you have 1 ton throughout the bar. If you have a perfectly smooth reamed hole in the same bar a stress raiser is produced and can raised the stress at that point 6 times (varies with materials). Anyway with a hole you have 6 tons. With a sharp notch you end up with upto to a million times stress raiser, hence cracks tend to grow also why on aircraft we tend to drill a hole at the end of a crack to slow down propagation.

 

To add another problem to what you have is like said above it does look like fatigue cracking which can occur well below the materials yield strength.

 

If it is easilly weldable i would machine the hole lot out and weld a new boss in there. But I am conservative

 

As it's low reving, low cyclic loads a cheaper option would be to, find them, full penweld them from each side and machine it smooth and re drill the holes

 

Putting something over it, with it still underneath will not stop the propagation.

 

The whole mystery about it is did the fatigue cracking occur over a forty/fifty year life span or did it occur over a shorten span as from looking at it (from the outside), it is impossible to determine the rate of propagation. If you do do a simple repair, yu may want to try a simple balance check on some rails.

[Gordon_M]

General agreement here that you need to crack check it, MPI or Dye Penetrant. I'd guess you'd see enough crack that you would want to take it off and fix it, presumably full penetration weld from one side, followed by grinding it out from the other side and building it up there before machining / grinding flat.

 

Here's a question for you. Why did it crack, and why there? If this was a truck with an electric starter, where the engine always tended to stop in the one position and then get starter engagement at exactly the same point every time, I could see why it might crack in one location, but presumably this truck doesn't have that luxury.

 

Is it already distorted ? It might not just be cracked, but might be showing a crack where the housing has tried to pull away from the centre fixing. Might be worth lathing it for a quick concentricity / distortion check first.

[Jerrykins]

Were it I, I would machine a circa 2'' wide annular disc to the approx thickness of the existing bolt heads. Weld the disc to the outer diameter of the plate. Drill matching holes through the new disc from the existing holes in the plate. Countersink drill the annular disc and fit counter sunk bolts. Thus beefing up the assembly without upsetting the material where the cracking is underway. Jerry

[ajmac]

If you can confirm that the crack only travels between the two bolt holes I would be inclined to leave it alone, it has relieved the stress that caused it and won't go any further.

[monty2]

WAUUUUWW !! what a job don't believe that any JEEP restorer would go to such a trouble to get a wreck restored even if it is a prototype of the Bantam or Ford GP.

 

SUPER keep watching it .

[Minesweeper]

What a wonderful lot of replies and thank you all for them! I really do not know what we will decide to do and that is very much down to Steve to make the final decision - as the Professional Mechanical Engineer amongst us!

 

One thing that we have not mentioned is that we have a spare clutch - I cannot remember where it came from - but it remains in a similar state to the current one when we first started on it, with all of its fittings still on it - and that too is in a heavily rusted condition. So it might be sensible first of all to separate that one from its fittings - get it sand blasted and have a good look at it. If it is sound, then that would appear to be the answer!

 

Tony

[Chrisg]

Lt 2 1/2 shouldn't be a problem will check on Monday

[Minesweeper]

Lt 2 1/2 shouldn't be a problem will check on Monday

 

Thanks Chris!

 

Tony

[fesm_ndt]

Fatigue was not really understood until post war and the Comet investigations. Interestingly enough the UK standards on this damage mechanisms are the world leading ones.

 

I would be interesting to see the other clutch as to see if it was cracked the same as I doubt the balancine and maching would of been much different at the time. Old stuff is generally over engineered and can take a lot more damage with newer material and less material a half a thou crack becomes critical.

 

[Minesweeper]

Fatigue was not really understood until post war and the Comet investigations. Interestingly enough the UK standards on this damage mechanisms are the world leading ones.

 

I would be interesting to see the other clutch as to see if it was cracked the same as I doubt the balancine and maching would of been much different at the time. Old stuff is generally over engineered and can take a lot more damage with newer material and less material a half a thou crack becomes critical.

 

[/QUOTE]

What an interesting and informative film that is - really worth watching! Thank you!

 

I'll see if I can get some pictures of the second clutch to you later!

 

Tony

[GeePig]

.... Old stuff is generally over engineered and can take a lot more damage with newer material and less material a half a thou crack becomes critical.

 

 

Older stuff having larger masses is also a problem, because the forces that are generated at any particular speed are also greater, meaning any cracks will propagate faster. What I find interesting is considering why some things survive while the majority don't - were they the best parts, or the failed parts that got replaced and abandoned, or new parts that never found a use? Was that crack something that went unnoticed, or was something that someone meant to do something about, sometime...

[Great War truck]

Here are some pictures of the other clutch – the last picture in this sequence shows the equivalent area to the cracked part in the original one after a quick wire brushing. There does not appear to be any cracking there – so perhaps we are saved from a further lot of trouble! It will have to be properly cleaned to make sure that it is sound.

 

 

 

 

[Gordon_M]

Interesting. Note the R showing that hub and housing are assembly marked either for operation, concentricity, or balance.

 

It does look to be in better order.

[fesm_ndt]

Older stuff having larger masses is also a problem, because the forces that are generated at any particular speed are also greater, meaning any cracks will propagate faster. What I find interesting is considering why some things survive while the majority don't - were they the best parts, or the failed parts that got replaced and abandoned, or new parts that never found a use? Was that crack something that went unnoticed, or was something that someone meant to do something about, sometime...

 

That is an interesting point as often the hardest part is determining the cause and in if it is in some industries you have to find the exact cause. There is a bit of give and take as older stuff generally ran at lower speeds, with lower cyclic loading. On the other hand older materials were generally of a lower quality.

 

Newer stuff is engineered with much less margin for error as the materials are better, the QA/QC is better and the fabrication is to a higher standard but can operate at much higher cyclic loads. The odd thing about this statement is that it was perhaps a correct statement 20 years ago, but much manufacturing has moved from the original areas to areas where materials, QA/QC and fabrication are all poorer.

 

 

Here are some pictures of the other clutch – the last picture in this sequence shows the equivalent area to the cracked part in the original one after a quick wire brushing. There does not appear to be any cracking there – so perhaps we are saved from a further lot of trouble! It will have to be properly cleaned to make sure that it is sound.

 

that's an easier way :-D:-D:-D

Edited March 10, 2013 by fesm_ndt
pp spelling

[Old Bill]

Thank you, Gentlemen, for all of your kind thoughts and suggestions.

 

Dad found the crack after we went our separate ways last weekend so I have only seen the same photographs that you have! I am sure there is a fix in there but I feel inclined to have a closer look at the second clutch before deciding on which one to use. I did start pulling the second one to bits but broke the spring clip off in the hole and so decided to continue with the first instead. As a result of the clip still being in the hole, I think we will have to cut the nut off which is a great pity as it is better than the first. Oh well. At least we can make a new one if necessary. The other plus side of using the second clutch is that we might be able to get away with the original lining again.

 

Cheers!

 

Steve

[Great War truck]

One thing that we do not have but will need sooner or later is a Starting Handle! Fortunately, this picture of the original handle on the Carlton Colville “Thorny” and an “exploded” picture in the Parts Book really provides all the information that we need to make one.

 

 

We started with a suitable length of black mild steel for the main body of the handle with two small 3/16” thick steel discs which will be silver soldered to each side of the bottom of the handle with a larger round part to be welded to the top of the handle to give the correct profile and ultimate strength. After these parts were joined, the body was set up in the milling machine so that it could be machined to the correct profile.

Across the top of the handle is a tightening adjustment – a 5/8” slot was machined across the top to take a 5/8” steel tube through which goes a 5/16” bolt. This ultimately will need to be slit across its circumference and into the hole in the top of the handle so that when the nut is tightened on the bolt, it will draw the two sides together. This slit to be cut later after the the hole in the top of the handle is enlarged to 1” square to accommodate the shaft with the dog which engages with the engine.

 

 

 

 

[Great War truck]

After the 5/8” steel tube was brazed in, the handle was set up in the milling machine again so that round hole in the top could be opened up to 1” square to take the shaft with the dog.

 

 

 

Some final adjustment with a file ensured that the square was a good snug fit. This section just needs the slit cut in it now, through the 5/8” tube to the top point of the square hole to finish that job. Steve has a good slitting saw so that will be finished off in Leicester.

 

 

 

 

The actual part of the handle which is grasped is a brass tube with a steel core – the brass tube revolves on the steel core. The steel core is a good push fit into the vertical part of the handle, with its end then riveted over. Similarly, the outer end of the brass tube is supported by a 1” long steel disc through which the end of the steel core protrudes by just an 1/8” which is also then riveted over to ensure that it remains tight.

In these pictures, the whole assembly has not yet been pushed hard home as it really needs the press to do this smoothly and comfortably and that, too is in Leicester!

 

 

 

[Gordon_M]

That's nice work, but you are at it again with that silver solder. All that lot could have been welded together quite easily and I'm sure the assembly would have been stronger, though admittedly not as neat.

 

Never had a silver soldered stressed joint come apart?

 

Gordon