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WW1 Thornycroft restoration


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It is the last day of Steve's holiday today so he and Dad were keen to finish the engine strip-down. The last remaining job was to extract the pistons from the cylinders and this has been causing us all some trepidation. However, there is only one way to get it done and that is to go and do it! Here is the jig that they made yesterday.

 

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It is a simple 1 1/2" diameter bar tapped through at 3/4" Whitworth for two set screws. The centre collar is the same size as the journals and sits inside the big end to prevent it from going oval when the jacking force is applied. The bar was fitted into the big end of the first rod and then blocked up with timber underneath to jack the screws against.

 

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The pressure was applied by slowly winding the bolts until there was a bang and the piston let go.

 

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Progressive jacking and packing saw it slowly extracted.

 

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The piston doesn't look too bad and a good clean will help. Even the scraper ring came loose so we were very pleased. The bore could do wth a bit of a polish, however.

 

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The second one was approached in the same manner but after tightening the bolts as far as he dared, Steve resorted to a bit of heat to encourage the piston to let go.

 

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This was applied very gingerly as the risk of cracking the casting is very high and would be catastrophic. He raised the temperature to a point where it was too hot to keep your hand on it and then gave the bolts another half a turn. Fortunately, the piston let go at this point and he was away.

 

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On removal, the piston looked fine but the bore could do with some attention. A good crust of rust had formed over the crown it looks pretty poorly beyond that point. Something to consider another day.

 

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Number three had been on top dead centre when the engine stopped so it had to be dragged the whole length of the bore. Dad polished the area below the piston with emery and Steve tried jacking again. Much to his surprise, it let go very easily although it had still be be jacked the whole way. Number four was just the same so success has been achieved and we are very pleased.

 

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The day was rounded off by an inspection of the valve guides. The inlet side are all fine but theexhaust side are well worn. Steve therefore knocked them out with a drift and Dad will turn up some replacements in due course.

 

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Steve returns to Leicester tomorrow but all objectives for the week have been achieved and we are very pleased. Now all we have to do is clean the bits, make replacements and put it all back together!

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With both the whole engine and the "half" engine now mainly dismantled, the next job was to get the old studs out of the crank case that we intend to use. The old studs are either very rotted away or the threads are quite worn so they must be replaced with new ones.

 

We expected this job to be quite difficult and that the old studs would probably break off. However, they had been heavily dosed with "Plus Gas" and all of them just unscrewed with the use of a Stilson. A pleasant surprise!

 

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The four long studs go down inside the crank case to hold the splash guards.

 

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And now the really unwelcomed and odious job - cleaning the crank case! It is too precious and delicate to have it sand blasted so it is back to rotary wire brushes in the hand drill - with paraffin and a soft brush to get the grease and oil off. This one is more difficult than the Dennis - that one is made of aluminium so that one man could heave it around but the Thorny one is of cast iron and is really a two man job to get it off its stand to turn it up side down.

 

A start has been made on one end but there is a long way to go!

 

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Thanks for that Robert. We are always worried about boring everyone to death with mindless detail! Sometimes a photo does help you get your thoughts together with a problem though. This was our first experience of extracting pistons and we were not looking foward to it at all. Fortunately they were not too painful in the end. One of my friends filled his pistons with diesel and then set fire to it with the acetylene torch! It worked for him but he is braver than I am!

 

Good luck with the Leyland. We shall look forward to hearing of the outcome!

 

Steve :)

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Thanks for that Robert. We are always worried aboutblem though. This was our first experience of extracting pistons and we were not looking foward to it at all. Fortunately they were not too painful in the end. One of my friends filled his pistons with diesel and then set fire to it with the acetylene torch! It worked for him but he is braver than I am!

 

Good luck with the Leyland. We shall look forward to hearing of the outcome!

 

Steve :)

 

Steve,

 

please don't stop "boring everyone to death with mindless detail!" it's what makes this thread so interesting! I have quite a lot of experience with "modern" engines and mechanics in general. I really enjoy seeing it all coming appart and going back together again!

 

Keep up the good work!

 

Regards, Matthew

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I think there's a lot of value in the "mindless detail" particularly when accompanied by such excellent photographs.

 

I've seen a few useful hints on these threads - not sure I'm going to buy a lathe or a milling machine yet, though.

 

Gordon

Edited by Gordon_M
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In some respects there can never be enough information, it is the small things that would be left out of a 'resume' that are often the gems, like the piston removal. Walking past a restored vehicle at a show is one thing, seeing what went into the retoration is quite another. I will always pay a lot more attention to WW1 vehicles at shows from now on, I expect most people don't realise the amount of work that goes into the rebuilds.

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The water connection consists of two castings and a rubber seal between (according to the manual). We have yet to part them but I anticipate complete destruction of the rubber when we do!

 

Steve

 

Let me know when you get to this stage, I should be able to help with the rubber element; we often get called on to recreate obsolete parts. http://www.martins-rubber.co.uk

 

Lovely to see another major project coming back to life, well done, Adam

Edited by Thumpercross85
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In some respects there can never be enough information, it is the small things that would be left out of a 'resume' that are often the gems, like the piston removal. Walking past a restored vehicle at a show is one thing, seeing what went into the retoration is quite another. I will always pay a lot more attention to WW1 vehicles at shows from now on, I expect most people don't realise the amount of work that goes into the rebuilds.

 

yes, detail in depth is always good and you should have this to show off your hard work

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Let me know when you get to this stage, I should be able to help with the rubber element; we often get called on to recreate obsolete parts.

 

 

Thanks Adam. You are very kind. I can make quite a few things but rubber items are a bit out of my league! Will be in touch!

 

Steve

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Progress just a little slow at the moment because of other diversions! Cleaning of the Crank Case has started, using just rotary wire brushes in a electric hand drill and also paraffin brushed on to get rid of grease and oil. These two pictures are "before and after". Still a long way to go as we have not started on the inside yet.

Some of the residual rust on the case is just dust from the wire brushing and it is our usual practice to "wash" items with cellulose thinners before painting to get rid of this and to leave a oil-free surface. Bondaprime - the primer we use is thinned with cellulose thinners.

 

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This is the inside of the Timing Case - "before and after" the first clean !

 

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I "discovered" another useful way of getting rid of rust, plain white vinegar, either submerged in a "tank" or with a rag soaked in it placed in such a way as to have full contact with the metal to clean. wash with water and protect immediately. Easier than electrolysis, it dose smell, so I put the whole thing in a plastic bag, bin liners are good for big parts!

 

I like you swage block in the back-ground, I hope nobody else dose!

 

Regards, Matthew

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With the "Dogs" for the Inlet Valve Caps virtually finished last month but put to one side as the top flange on each of these has to be partially cut back to leave the "Locking Tabs". There are similar "Tabs" on the "Dogs" for the Exhaust Valve Caps and it was our thinking that these could all be machined at the same time.

So it was time to turn to making the Exhaust Valve Caps. Like the Inlet ones, they are machined from solid drawn cast iron bar. We decided to machine one right through first of all with the exception of machining the "Tabs" on the top flange - just to prove the machining process - and if that proved to be successful, the other three could then be machined in a batch.

The iron was turned down first of all to the overall diameter plus a few "thous" to be finished off later in the process. The flange was then roughly cut in - again leaving a few "thous" to be finished off later.

 

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The inside was then machined to the final shape and dimensions, drilled and tapped 5/8" Whit for the locking bolt and nut. There is a drawing of the part following, should the photographs not be clear enough to see the finished shape.

The part was then reversed in the lathe so that first of all, it could be machined down to the final depth - in other words, the chucking piece can be machined off at this stage.

Final machining to the required shape follows.

 

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All done - apart from cutting back the flange to leave the "Tabs". In the final picture, locking bolt and nut are screwed in.

Just another three to do - and hopefully will be done quicker as a batch!

 

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  • 3 weeks later...

With the engines stripped down, we are starting to think about the re-assembly of it but I guess little will actually be done to putting it together until the whole team re-assembles in Devon later on. A whole new set of studs will be required and manufacture of these has started.

 

You will recall that this is a four cylinder engine with the cylinders cast in pairs - i.e. two cylinders in one casting so that there are two fixed head cylinder blocks to attach to the crank case. Each block is held down on six 5/8" studs - the studs are threaded 5/8" Whitworth. We have chosen to make the new studs out of EN24 which is a bit tougher than ordinary mild steel - we are thinking of the forces to which they will be subjected to in use.

 

Of the six studs, four are plain studs - one at each corner - but the two centre studs are extended down into the Crank Case, but reduced to a 3/8" diameter on the extended portion - to hold splash guards which are designed to prevent the oil from going up into the bores.

 

We started by making the centre studs. The 5/8" EN24 was held in a collet chuck and was threaded in the lathe to about 4/5 of the full depth of the thread - and then finished off with a Die. The embryo stud was then reversed in the chuck - the required thinner length was first of all reduced to 3/8" and then threaded 3/8" Whitworth - to hold the nut retaining the splash guard. Later on, this will require a cross hole in the 3/8" threaded section to make sure that the retaining nut cannot fall off in to the crank case. The second section of 5/8" thread was then cut - using the same method as the first one.

 

So that's those four out of the way and we can turn to the eight shorter ones next.

 

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The West Yorkshire Steel site has a nice table of mechanical properties for different grades of steel if anyone is interested. I dare say I will be going down the EN24 track too some time in the near future on a similar motor. Did you use 'T' type steel?

Regards Robert

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It is really amazing the variety of things that crop up and which we discuss on HMVF! Yes - this was EN24T - and anybody who really wants to look at the specification of this material in depth should "google" it! In a nut-shell, it will tell you that this is "through-hardening alloy steel which can be used in components such as gears, shafts, STUDS, and bolts. It can be further surface hardened."

 

For our purpose, it is suitable as it is and will not be hardened further. We have used it before in bigger lumps on the Dennis and then I was concerned about machining it - thinking that really it would be just too much for the modest home workshop. This time, I bit the bullet and found that it machined very easily with a nice finish.

 

Tony

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Where-else on the net will you find a discussion about materials suitable to replace those from a motor designed 100 years ago and built soon after. The discussion on 'head-tightening sequence' for these old motors was another classic. By following these threads there is much is to be learnt; be it technique or technical detail. However the 'gem-discussions' are soon lost in a sea of thousands of messages. Is there a way of collecting said 'nuggets' in some sort of compendium? At the moment I tend to write them down in a notebook!! Very low tech...

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Long Bank Holiday weekends are usually the time when the whole team gets together in Devon to press on again with restoration work. This Easter, Steve could not come down but I joined Tony so that we were still able to press on with some work that requires more than one pair of hands.

 

 

Tony cleaned the Crank Case a week or two ago – and also underneath as best that he could without turning it over – he thought it too heavy and difficult to risk doing that on his own – but the two of us did that easily and I was able to get in underneath to do the greasy parts that Tony could not deal with working from the top. A further clean with cellulose thinners – and then another coat of primer.

 

 

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Whilst I was pressing on with that, Tony completed the cylinder studs and when painting was completed, he tried a trial fitting of them in the Crank Case.

 

 

 

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Just to finish off the day, I started cleaning some of the smaller bits – to get them ready for reassembly.

 

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Tim

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