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WW1 Thornycroft restoration

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Taking a compression test wouldn't have told them much with the stuck rings I think.

David

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Posted (edited)

I was more intrested in a before and after number after expanding the ring gaps and opening up the bore. It would have read low on the two holes with the stuck rings and let them know before disassembly how many cylinders had problems. Compression tests and leak down tests can be helpful in understanding ring seal. Also it could identify unknown valve sealing issues. It’s an easy test that’s done in a few minutes. On the Rolls I can shut down the car with a charge in the cylinder and come back an hour later, swing the distributor and get it to fire thus giving what we call a “free start” without touching the starter. Fun to do at shows and a great indication of a good engine. All just for fun. 

That one hole without soot on top of the piston should be investigated, it may mean a manifold vacuum leak or a poorly sealing exhaust valve, or ignition problem on that one. A cylinder balance power Check while running would help identify any loss of power if there was any. It may also be no problem.........worth checking out.

Steve asked how I found this thread and I didn’t answer. Back in the early seventies a family member had a WW I Renault tank that I use to play on. They had it out in the front yard as a lawn ornament. As I’m sure they are quite rare, I was attempting to locate it for possible purchase. Ended up chasing down a Stewart and a Sherman. I built my garage attached to my house to handle the Sherman, but never managed to land one that was in my condition and price range. Still want to add a WW II tracked toy to the collection. Most likely something lighter as I dont want to own a tractor trailer to go to the shows.

Edited by edinmass

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4 hours ago, edinmass said:

 A cylinder balance power Check while running would help identify any loss of power if there was any.

Ed, I would just pull off each plug cap in turn and listen for a change in engine note to see if I was missing on a cylinder. Is a 'Cylinder balance Power Check' anything more sophisticated?

On my early Dennis's charging a cylinder beforehand and then returning up to a couple of hours later is like you say a real 'party piece'. The Dennis's have trembler coils so we have plenty of sparks to set alight the remaining mixture.

Barry.

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Starting when shut down with a charge: my son loved to do this when he was a little boy (he is now 13). It also shows the advantage of an impulse magneto.

Regards, Marcel

 

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22 hours ago, edinmass said:

That one hole without soot on top of the piston should be investigated, it may mean a manifold vacuum leak or a poorly sealing exhaust valve, or ignition problem on that one. 

Agreed; although in my experience a clean piston amongst sooty ones suggests a water leak into the cylinder.

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On 5/29/2018 at 9:20 AM, Tomo.T said:

 

Hi Steve,

Looking at your pics above, your front mudguards appear to follow the radius of the wheels. From the original pictures this was not the case and there should be a straighter section at the rear. This only applies to the fronts, and the rears are as shown. I am unable to illustrate this atm. but you might want to have another look before finishing the brackets ?

Tomo

Hi Tomo.

You are right in that nearly all Thornys have a straighter portion at the rear of the wing. However, if you look , you will find that there are quite a few different patterns in use with some domed and some flat on the top and other subtleties. As ours are domed, I think that straightening out the rear edge is not to be attempted.

I haven't been able to search through the pictures as my new computer won't talk to my back-up drive which is irksome in the extreme!

Steve   :) 

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On 5/28/2018 at 10:15 PM, Richard Farrant said:

Hi Steve,

A thought has just come to me regarding your pistons. I am not sure how long it was between them being cast and when you machined them, but it was well known years ago that iron castings had to lay for a period before machining. I recollect this with motorcycle cylinder barrels. Also cylinder blocks for engines, I have had experience of several types where they were machined pretty soon after casting and then the blocks became out of line when the casting 'relaxed' (probably a technical term for this which I cannot remember).

regards, Richard

I had heard of the weathering of castings by leaving them out in the foundry yard for six months to settle down ('That's not weathering, that's rusting!') I must admit that I hadn't thought of doing so on ours as I thought the effect would be negligible. Apparently not! Our pistons are about a thou elliptical with them being narrower across the gudgeon pin holes. At least I don't have to machine them that way. I just need more clearance in the bores!

Many thanks for the reminder. I shall know for next time now.

Steve   :)  

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On 5/31/2018 at 8:55 AM, edinmass said:

Steve asked how I found this thread and I didn’t answer. Back in the early seventies a family member had a WW I Renault tank that I use to play on. They had it out in the front yard as a lawn ornament.

Thanks for that Ed. Most interesting! Some lawn ornament! I think we shall have to count that one as one that got away. At least you have a garage big enough for a Sherman tank. You can never have too much space!

Steve  :) 

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2 minutes ago, Old Bill said:

I had heard of the weathering of castings by leaving them out in the foundry yard for six months to settle down ('That's not weathering, that's rusting!') I must admit that I hadn't thought of doing so on ours as I thought the effect would be negligible. Apparently not! Our pistons are about a thou elliptical with them being narrower across the gudgeon pin holes. At least I don't have to machine them that way. I just need more clearance in the bores!

Many thanks for the reminder. I shall know for next time now.

Steve   :)  

No problem Steve. It was just that I remembered coming across problems with cylinder blocks that had not been allowed the time to settle and thought the same could occur to a piston and it would not need to alter only a few thou to cause a problem.

Hope you can resolve the problem.

regards, Richard

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In the steam railway world we leave new cylinder castings out to weather for as long as possible before machining.  At least two of our out-of-ticket locomotives (which won't be in the overhaul queue for a while) already have new blocks sitting outside. These should be well seasoned by the time they are required for machining. Lack of cylinder block seasoning was a problem in some locomotive classes when constructed from new, and they required much remedial work and ultimately new (seasoned) cylinder castings .

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I found the whole weathering thing very interesting, didn't know that. Although I had heard of BMW's pee-blocks for racing...

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Yes, there was an article in one of the BMW mags about 15 years ago about the blocks used in the 2002 bat mobile and later M3. They were left outside for months and staff were incouaged to pee on them to accelerate the stress relieving qualities of time and rust lol.

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14 hours ago, Chris Hall said:

Yes, there was an article in one of the BMW mags about 15 years ago about the blocks used in the 2002 bat mobile and later M3. They were left outside for months and staff were incouaged to pee on them to accelerate the stress relieving qualities of time and rust lol.

It seems to be widely reported, so may be true, but I very much doubt if it had any effect. 

 

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I think any effect would be that the pee encouraged rusting which will have had a small effect on reducing residual tensions in the very surface of the castings. Grit blasting the rust off afterwards will have had a much bigger effect. I think it makes a nice colourful story but they might as well have danced round it for the same effect.

David

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I think its a Cast Iron thing to be honest.  All steel casting have to be heat treated to prevent them being brittle (Widmanstatten alpha).  The great thing about CI is once its out of the sand its ready to be machined and away you go, however because there are no heat treatments required any residual stress (locked up dislocations in the lattice) caused during solidification in the sand mould can cause it to move a little over time as it stress relieves at room temperature.  If you gave it a stress relieving heat treatment then all the dislocations would move that much more quickly and there would be no need to weather anything.

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Hi Chaps.

I have been sorting out all the things I put on hold whilst working on the lorry! However, I am getting back to it now. I am not good at instant decisions as I like to weigh the facts and listen to all of the advice I am offered. Even if I don't take your advice, I always appreciate it very much so many thanks to everyone for their suggestions.

In the mean time I have been pushoing on with wing brackets. They are a horrible job and I shall be pleased to see the back of them. I have spent a lot of time filing a bit of shape into them.DSCN7613.JPG.ab9bdb2a217a190e9669730c8a1f754d.JPG

Then it was a case of drilling the bolt holes.

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Followed by a bit of filler to tidy them up.

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They are now in primer awaiting attention from the paint shop.

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Something else which didn't quite get finished off was the throttle pedal. Dad had cut it to my sketch but never quite got around to filing the section. In the end, this proved a blessing as I got it a bit too long and had to drill a second pivot hole futher up.

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Once trimmed back, the pedal was filed to an elliptical shape to represent a forging.

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Another tedious job!

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It does make a worthwhile improvement in its appearance, however.

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I have finally decided what to do with the pistons and cylinders. The cylinders are to be honed out by a further 0.002-0.003" to clean them up and increase the clearance and this should happen next week. I have been turning the pistons in the Myford to increase the clearance around the top land to 0.017" and that between the rings to 0.012" with the bottom section remaining with a 0.005" clearance. This will increase when the bores are honed.

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I have also taken the opportunity to increase the depth of the ring grooves by 0.020" and have opened them out by a whisper to make sure that the rings move freely.

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Following advice from here, I shall replace the compression rings on the two pistons which picked up as the originals were scored when this happened. I shan't trouble with the oil control ring. The pistons are all complete now and only await delivery of the new rings.

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Now I must return to filing wing brackets, the front ones this time. They don't get any more fun to do!

Steve   :)

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Steve, I think you are on the right track. I would replace ALL the rings. I would change the oil before start up. I would also change the oil again after an hours running in. I would use a straight ten weight for the first two changes, and then go to a straight thirty after that. Once the lorry has a few hundred miles on it I would switch over to a 100 percent synthetic. If you choose not to run anti freeze,  use distilled water with cutting oil in it. Prevents rust, lubricates the water pump, and if it leaks or overheats it cleans up with a garden hose. I take it there is no chance for a freeze where you live........if there is a chance then obviously anti freeze is required. Looking forward to seeing her back on the road........and looking forward to the next updat! Ed

 

PS- a magnetic drain plug would also be a good idea.......I would devise a way to install a few magnets in the oil pan as well, even if you can’t get to them often, they can be a big help. 

Edited by edinmass

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Steve - I think in time you will agree that to have persevered with the Brighton run would have been a bad decision.

The 3 of you were under the pump in order to make that event and pure and simple, the truck wasn't going to make it.

Driving these old things on modern roads is stressful and having an untested vehicle with as it turned out a major issue would have just ruined the whole experience, probably with it marooned by the side of the road with a seized engine.

In my opinion all 3 of you man'ed up and made the no-go decision which was a much harder thing to do than heading off down the road. In aviation it goes by a number of names, but is a well know trap for those who fixate on the goal to the exclusion of perspective. It is a difficult thing to resist.

See graphic.

Now you have no schedule, can get that engine running sweetly and can enjoy the rest of the restoration, other than the wings (mudguards) installation that is.

Regards

Doug

(Aussie one)

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Edited by dgrev
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Edinmass,

There is virtually nowhere in the UK where it is guaranteed to never freeze so unless your vehicle lives in a heated museum building and only comes out in the summer anti-freeze is required. The corrosion inhibitor aspect is good too.

I have just done some work on a modern GM auto box and was surprised to find that there were several ceramic magnets in the oil pan just stuck on by their own magnetism. They had collected a huge amount of swarf from when the converter died.  If I ever work on an old engine with a tin sump but no magnetic drain plug I will definitely put a magnet in there as it is such a simple mod with huge benifits.

David

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They are on scedule for London to Brighton 2019. A magnet machined in the drain plug might be a good idea, i use two hard drive magnets on the 2.25 petrol / diesel oil filter housings.  

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Thanks Chaps. Lots of food for thought there. We store them dry, generally, as we do very few miles and it reduces the amount of drips on the floor! The Dennis has been roadworthy for seven years now and still hasn't done 500 miles and the poor old FWD hasn't run at all for nearly three. All a bit sad really!

I have spent the day working on the front wing irons. Grinding, filing and filling the same as before although the welding was very kindly done for us by Adrian. A very tedious job which I can now hand over to the paint shop.

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Steve   :)

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Steve, spoke to an old time engine shop and Babbitt guy today, we spoke of your problem, and he commented your ring gap should be .020 , I think he is about right. I too have finished vehicles that don’t get driven much. A made a new rule, If I don’t drive it twice a year, I sell it. More than 75 percent of my stuff went down the road......which was fine. Currently I have 17 regularly exercised pre war exotic cars kept in top running condition. It’s just about a full time job. After two years, today  I managed to clean and wash my every day Ford Focus. It looks much better! Ed

Edited by edinmass

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Just think what can happen to a vehicle not used! I got given a picture of my dad's 109 and he claimed €60 damages for a mirror and mirror arm... it needs new foor wells and all repair sections of the bulkhead. Yes, it is a steel scaffold and not as i was told a aluminium one. Drive them old ones, enjoy them static... just insure them properly! 

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