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WW1 Thornycroft restoration

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Ouch, sort of mixed news then ? :cool2:


I was looking forward to about twenty pages of threads where you saved up, bought a gear-cutting company, a CAD machine, and various other trinkets then just made the thing - alas it will now be clean up and fit - doubtless it is as good inside as the outside looks.


Ah well, sometimes Santa comes through, and I'll join in the thanks to the NZ contingent.



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It has been quite an exciting day really.. Tim and I pulled the camshaft out and rotated it through 180° yesterday. Unfortunately, he then had to go home but this morning, we were able to put the engi

We haven't balanced the shaft. The rotation depends on how well I drilled the leather so there will be some variability in it. Hopefully, there won't be a problem but if there is, then I will have to

Thanks Tomo. I'll remember that! We have had a nice day., all bright and still and not cold. I have been pressing on with the hand controls and linkage. First part was to cut the throttle shaft a

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Wonderful Tim, no stopping you now. I marvel at how we are able to solve problems and source parts so quickly via the internet. In the past we would have given up after months of fruitless letter writing and false trails.


Quite right. Mind you, it has still taken us 22 years!



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Gordon_M said:
Ouch, sort of mixed news then ? :cool2:


I was looking forward to about twenty pages of threads where you saved up, bought a gear-cutting company, a CAD machine, and various other trinkets then just made the thing - alas it will now be clean up and fit - doubtless it is as good inside as the outside looks.


Ah well, sometimes Santa comes through, and I'll join in the thanks to the NZ contingent.




Yes, that would have made a good read indeed and we could have done it if we had to (much like Ben is doing with his Dennis). It is however much nicer and easier to have the original parts. Thanks again Mike.


Before it was packed up Mike took some photos of the diff, so you can see what remarkable condition it is in.






Look at all that lovely black stuff.

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That's lovely, a real clean and fit job. Did I see a full set of internal expanding brakes in those rear hubs too?


There must be all sorts of odds and ends like that axle, dotted about the world, belonging to people who know how rare they are and determined to prevent them for being torched for no reason, so everyone happy at this sort of result I'm sure.

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  • 3 weeks later...

Boxing Day - and time to open the Box! Inside was the complete Thorny Back Axle with the diff in it. We then had to take the wheels off so that the axle and the two wheels could be stored safely and separately. First job was to get the two half shafts out - straight forward and both half shafts are in excellent condition.








These three pictures reveal the excellent condition of the half shafts









Then to get the wheels off. A series of jacking bolts and a specially home made spanner to remover the big retaining nut did the trick. This primitive spanner was just an old bit of steel bar with two prongs bolted to it, to fit across two opposite flats of the big nut. Everything was nice and oily and really none of the fastenings gave us any great deal of trouble to undo.










More to come in a moment

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It would have been nice if the first wheel would then just slide off the axle but it was quite tight and slightly fouling the brake linings. A crow-bar and small hydraulic jack eventually got them moving and we were able to slide them off. These wheels are extremely heavy and we used the Engine Hoist to take the weight of them.











Unfortunately, a Brake drum on one of the wheels cracked during the dismantling process. We really hate breaking original parts - but we have a couple of spares in stock so can replace that one.











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Brake drum casting looks like a decent quality cast iron ( rather than steel or malleable iron ) I'd suggest a thorough crack check of any replacement before you spend a pile of time and energy fitting it, and the one on the other wheel as well. MPI check for preference. You might find some cracking on something that looks other wise fine visually.


On the other hand it does look relatively simple form, and would turn up nicely from a ring forging in carbon steel, which would probably be preferable mechanically since cast iron is great in compression and a bit iffy under tension and shear stress.


Positive note - you have a back axle, diff, wheels, so what's one cracked casting? :cool2:


I'm guessing that the rubber could be cut down a little to give a surface, then built back up and autoclaved to vulcanise it to the rims.

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Yes, breaking that brake ring is very annoying but can't be helped. Nothing we can't fix! The other ring has a very old crack in it as well. Fortunately, our chassis still has two wheels on it so we will have to play mix-and-match when the time comes. My immediate thought to replace it, if we have to, would be to have one cast in malleable iron but we will cross that bridge when we get there. My immediate concern is to get the axle locked away under cover in case our anvil thieves return.


Tyres will be interesting. The army had twin 880-120 tyres fitted but these have a single wide tyre. On the Dennis, we used the original 880-120 rims but had polyurethane tyres moulded on. We will do the same here unless a set of original Dunlops surfaces. One never knows!



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Interesting as to your comment regards the tyre sizes. A great number of the solid rubber tyres seen in N.Z. are wide singles for the rear. Some show the signs of Goodyear branding, I assume placed on the vehicle as new tyres were required during its working life.


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Our prime objective today was to get the Thorny Axle, complete with "diff" still in it safely stowed away until we are ready to deal with it. It is a fair old lump and with really only our Engine Hoist to move it, it was a case of proceeding with caution!

We are always short of space and it meant moving things around to find a safe home for it - but we took the opportunity then of bringing some other Thorny bits to the fore as they had been well tucked away whilst we were dealing with the Dennis.

Firstly, we wanted to turn the axle over on the pallet so that it was the right way up - it had travelled on its side from NZ.







The "right way up" axle was then lifted and dropped down onto the legs of the Hoist, and like that, was wheeled to the back of the Lorry Shed where a space had been cleared for it in front of two Peerless wheels. Here it does not interfere with any other activities in the Shed and it is safe and out of harms way until we are ready for it.






The Thorny project started some 22 years ago - we had no engine, no complete chassis and no "diff". In the early days of the project, we always thought that it would be a "piece of cake" to find all the bits that we wanted but it did not work like that! Following a "Wanted" advert for an engine - it must be about 20 years ago, we were offered a half of an engine - a Thornycroft M4, which was the correct engine. Sometime in its past, the two cylinder blocks had been removed and lost so there was the crank case, crank and pistons and some other attached bits and pieces. We jumped at that offer and thought that another engine would follow shortly after so that we were ready to go. It must have been perhaps another 10 years before the complete engine turned up and that acquisition is described in an earlier thread.

With everything being moved around today to accommodate the new axle, we dug out the old "half engine" as there are several bits still on that which are missing on the complete engine. That will be required shortly to work on so it was the appropriate time to bring it out.

Interestingly, one of the feet on the complete engine through which it is bolted to the chassis is broken off so we had thoughts of doing another "mix and match", using the crank case from the "half engine" as a replacement. That will be fine, but it is interesting to see that the matching foot on the "half engine" is also damaged - but not terminally so we wonder if there is a problem there with the engine fouling something as it is lowered in or taken out. We shall find out in due course!

Other things brought forward include the Gearbox and the part of the Gear Change quadrant.









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As part of our re-shuffle, we moved other engines around. We have a Dorman engine which is ear-marked for our second Peerless when we get around to it and an old FWD Wisconsin engine which is really past its sell-by date but good for spares. We wanted to move the Thorny bits to the front so that we could get at them and these two other engines have taken a step backwards until they are wanted!


We would be very happy to swap the Dorman Engine for a suitable Peerless engine if anybody has one!









All done! The Thorny engines in the front with the Dorman behind. Now just to get the grey civilian Autocar back in the Shed and then it will be job done. Hopefully tomorrow, we can get back to stripping the engine down!






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With the new back axle safely tucked away yesterday, Steve turned his attention to the engine today and to getting it stripped down. The next job on it was to remove the Valve Caps - but that was easier said than done as they were corroded to the extreme. They consist of what was once a hex headed threaded section which screwed into a mounting with a bayonet cap type fixing. The Hex head in all four cases had completely corroded away with nothing left and the bayonet fittings on the other parts were either corroded or broken.


Our usual procedure of heat and Plus Gas failed to work and the only alternative now was to cut them out. This was achieved with some difficulty on the first two with the use of a drill, a grinder on the Dremel and the good old hammer and chisel which broke them up


The photographs tell the story but you will see the extreme amount of rust on these fittings - especially around the threaded sections which made them impossible to unscrew.






















If things go well and with some perseverance, the last two will be out tomorrow!

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The pictures here have become a little jumbled and includes the photos from the previous posts as well. 


A fresh day - and Steve returned to digging out the last of the two valve caps. Again, just a case of persistence in cutting, grinding and drilling until the bits became free. They are now all out with no damage to the actual cylinder blocks. Not a very nice job and Steve is just relieved that we are not dealing with an engine with more than four cylinders!


We mentioned in an earlier post that one of the old spark plugs in the engine was a Mica one and it proved totally different to deal with from the other three. The last photograph in this sequence of three shows that plug after it was taken out, still screwed into its cap!

With the Plug Caps out, we turned our attention to getting the cover of the Timing Case. The Pulley Wheel for the Fan Belt had to be removed first of all - there were two jacking points in it and after the threads in those was cleared, it was just a case of making up a simple Jack (30 minutes work) to easily remove the Pulley (30 seconds work!)

At this stage, the Oil Seal had also to be taken off the Starting Handle Shaft so that the cover could be clear of any obstruction.

With some gentle pulling, pushing, levering and tapping, the cover came off to reveal a sight that we hoped that we would not see!


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Just before we called it a day, today, a file was scraped across the edge of one gear wheel, just to see how deep the rust was - and initially it does not look too bad............ But we shall see when it has had a proper clean.


The last photo shows the Governor - the lead weights have decayed somewhat!


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The first thing we did Saturday morning was to drop the sump from the engine. Fortunately, there was very little oil left in it and we guess that it must have been drained before we ever had the engine.

We believe that the last regular use that this engine had was to drive a stone crusher and there is certainly a lot of stone dust stuck to the outside of the case. Mixed with oil, the dust had turned into a hard scale. The inside was wiped dry and then most of the hard scale on the outside was scraped off - the next job will be to get it in a paraffin bath to clean it completely.

We are itching to get at the timing gears to clean them properly but it really is not possible to get at them in their present location. They have had a further slight scrape but they will have to wait as they are for the moment until the cam shafts come out.

The Fan Belt and Magneto Drive shaft was attached to the front cover and it has been possible to remove that one. An initial wire brushing on the gear wheel there has removed most of the rust and although the teeth are not perfect, we are optimistic that if the other wheels prove to be in the same condition, then they will be quite useable.

We do not think that water has actually got into the Timing Case and that most of the problem has been caused by condensation as the rust is quite light and almost superficial.


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The next big job is to remove the two cylinder blocks - this is not likely to happen quickly as the "team" is dispersing again now at the end of the Christmas Break and that will have to wait for the moment. However, we have started to remove the big ends as the objective is to lift the Blocks right off with the pistons still in them. We will take the pistons out when we can turn the blocks upside down so that we can see which ones are stuck and then re-act accordingly to deal with them.

With the bottom of the engine now opened up, it is possible to see the cams and the cam-followers. We must wait to see them properly after they have been cleaned up but they do not look over-impressive at this stage!

None of our old lorries have a dip-stick to measure the oil level in the engine - when was the dip stick invented, I wonder, as that does seem to be the easiest way of measuring the oil level.

In this Thorny, there is a float in the engine oil which is connected to an aluminum tube running vertically from the top of the float into a brass indicator fixed to the top of the crank case. This was totally corroded up and the brass indicator had been crushed so that the tube was stuck in it. There is no glass "window" in the brass indicator to protect the tube and the level is checked by seeing whereabouts the top of the aluminum tube is in the slot in the brass indicator window. We had to cut the tube to get it out but we saw after it was out that it was holed and damaged in any case so it would have had to be replaced..

This will be straight forward to repair and replace but the thing is very vulnerable. Hence my question - "When was the Dip-stick invented" - a much better and more practical gauge!


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Well done chaps, I was shocked when I saw inside the timing case but it's amazing what a little time-consuming wire brushing can do. Some time ago I started with a rough axle and after a good pressure wash, degrease, layer upon layer of paint stripper and endless wire brushing, I got the finish looking like glass. I'm sure you people will go way beyond that :-D

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Whilst putting the axle away over Christmas, we were reminded that both it and the gearbox require a mushroom type breather. Steve went to see a chassis at Great Missenden many years ago and although the chassis had been well stripped, it still had the breather which he was allowed to remove. This was safely put away at the time and forgotten. Steve knew we had it and, quite remarkably, managed to find it again! He cleaned it up and then proceeded to make another which was a nice exercise in turning and filing. They are now to be put away once again ready for when they are needed.


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