WW1 Thornycroft restoration

[Minesweeper]

Looks like a bigger workshop might be useful? Here's the engine repair shop at 3rd Heavy Repair Shop (358 Coy ASC) at St Omer

 

If only!

 

Tony

[edinmass]

Gentlemen, I have thoroughly enjoyed you restoration saga of both the Dennis and Thornycroft. Very impressive work and I can't say enough to thank you for your wonderful generosity for sharing it with all of us. Any new information on the pistons? Are you planning to make them yourself? They are very easy to order here in the US to any specification you may want. When we order new pistons, we order them with a slightly oversize small end pin, then ream the small end to a perfect fit. Saves time and money by not installing new bushings in the rods. Ed M. Boston, Massachusetts

[Old Bill]

Hi Ed.

 

You are one step ahead of us! Yes, we will need new pistons because we have lost 3/16" on the bore diameter due to the liners and the original pistons do not have enough meat on them to skim them down. My intention is to make up a pattern and have them cast in grey iron at our local foundry. Then I can machine them to suit the rings that we have bought. The biggest challenge will be the gudgeon pin hole as it is 2 1/2" below the crown but the clearance over the saddle on the lathe is only 2 1/16" so between centres boring is out. My mill does not have enough vertical stroke to go right through either so we may well be knocking on doors. Come to think of it, one of our friends has just retired and as a retirement present, has bought himself a large vertical mill. Time to invest in a few beers!

 

Do you know of a company that makes iron pistons as specials? It would be most interesting to find out what they could do for us.

 

Thanks for the tip-off!

 

Steve

[Barney]

Steve says; The float appears to be about 0.030" which feels OK but I don't know how much it should be. How much would you expect?

 

Normally crankshaft end float is 2 to 3 thou., although I have an old book that shows a couple of 1930’s engines had as much as 6 thou. clearance.

 

Sorry I can’t offer any scenario for 30 thou clearance, although I have seen, in engines where the thrust washers were badly worn, the crankshaft moving back and forth and creating a knocking noise. Also on engines where oil flingers and helical cut groves were used on the crankshaft, in place of oil seals or felts, the movement of the crank would sometimes cause an oil leak due to damage caused to the flinger when came into contact with its mating surface.

The biggest load taken by the crankshaft thrust washers are from depressing the clutch. Unfair wear and tear is caused by ‘riding the clutch’ whilst driving or holding the clutch out for long periods whilst the vehicle is in gear and stationary; having to double declutch on vehicles with crash gearboxes doesn’t help either.

On this engine a small amount of wear is also caused by the tooth angle of the helical cut timing gears trying to slide themselves out of mesh when under load.

 

Best regards. John

[Asciidv]

John,

 

I would love to talk to you in detail about the noise from crankshaft end float.

If you go to this You Tube link, you will see (hear!) why.

 

 

 

This link tells the full story

 

http://www.dennisfire.co.uk/p50.htm

 

I wonder if you would contact me off the HMVF forum at;

 

DrBAH999@aol.com

 

Thanks,

 

Barry.

[k2lofty]

At the point of timing all the cam sprockets to crank sprocket might be worth checking for TDC, on the crank. Although the taper pin hole lined up on the crank sprocket, could it not be half a tooth out, or even a tooth or 180 ? or did grandad drill them identically,and relative to the timing mark, or infact dot them last from TDC (OH I AM SUCH A WORRIER)

Fantastic thread, I keep up to date, and absolutly love it.

 

KEEP UP THE GREAT WORK---- LOFTY

Edited January 3, 2013 by k2lofty

[Asciidv]

Returning to the question of acceptable crankshaft end float and the observations that John raised, I have included the section on endfloat from a 1930's Leyland engine manual. The size of this engine is simiilar to the Thorny. The suspicion might therefore be that 30 thou float is a little on the large side.

 

Barry.

 

[Old Bill]

Hi John and Barry.

 

RE: End Float

 

Many thanks for your comments regarding the end float. 0.030" does seem a bit much. Unfortunately, there is no way of adjusting it except by replacing all of the white metal shells and line boring again. I really don't want to do that and feel inclined to leave it alone. I don't think that float was what stopped them using the engine although, I guess that it might make setting up the clutch brake a bit tricky. The timing gear end load will tend to bias the crank in the same direction as the clutch so there will be little end movement when I hit the pedal. I think we will leave it alone and see what happens.

 

Cheers!

 

Steve

[Old Bill]

At the point of timing all the cam sprockets to crank sprocket might be worth checking for TDC, on the crank. LOFTY

 

Thanks Lofty. You are absolutely right. Please may I have some guidance as to how to do it? There are no marks on the flywheel at all and the manual offers no comment. As the gears are a matched set, the two camshafts will be correct to each other but may, as you point out, be wrong to the crank. At the moment, we can set the crank to TDC using a square against the top of the case and I can put a follower and push rod in place so that we can see when that begins to lift an exhaust valve. The question really is when should it lift? One old motor vehicle manual we have suggests 49° before BDC. Does that sound about right to you? The Thorny manual really is no use at all for setting up the engine but the Dennis one gives a timing chart. This suggests 45° before BDC.

 

I think that I might put a datum on the crank case, then line the flywheel up to TDC and mark it with a felt pen. If I measure the diameter of the flywheel, I can work out the circumference and divide it into 45° positions using a tape measure. Then, if I put a DTI on the top of the push rod and slowly turn the flywheel, I will be able to see where it begins to open. A nice interesting challenge although I am not quite sure what I will do if it proves to be half a tooth out!

 

Incidentally, another question arises. Why are the timing marks on the gears marked '3' and '4' rather than 'I' and 'E' or '1' and '2'? Might the factory have been assembling matched sets?

 

Cheers!

 

Steve :-)

[mattinker]

The get you out of trouble method that I was taught was to set the N°1 piston to TDC using a dial gauge, measuring from say 10 thou below, going past TDC (top dead centre) to 10 thou below and dividing the distance between the two on the fly wheel. Working without the pistons, with the engine up side down, (bearing in mind that it's a fixed head!)N°2 journal at BDC (Bottom dead centre) might be easier. Find a convenient place to mark the flywheel for future reference. When N°1 is at TDC, the valves on N°4 cylinder should be "on the rock", the point where the inlet valve is opening and the exhaust valve is closing. With the valves in place, with the correct tappet clearances at the point where the cams just start to touch or come of the followers should be right! It's easier with a single cam shaft engine! My method should be sufficiently close to get the teeth into mesh. If the cams have no adjustment on the cam shaft, this method should be spot on. The Cams being marked in degrees could have been that when the engine was first set up, they had a selection of pinions to fine set the timing.

 

 

Regards, Matthew

[k2lofty]

Sorry I did not want to alarm you, but I would simply check that when all timing gears are fitted and marks aligned, and the crank put on TDC. (easily checked with a piston in and I know you have non at the moment) it would be a good idea to check the cam followers on the firing cylinder are both at their otimum lowest point IE both valves on that cylinder absolutely shut, and the opposite two followers on the rock, as for valve openings BTDC, providing the cams are timed correctly can do nothing but come out right as that is built into the cams, I am quietly confident all is well but this is the time to check just to be sure, as regards TDC mark its well worth marking the flywheel and the block, thus making life easier when attending to the basic IGN timing and even to allowing you the opportunity to see how near you are with a strobe, I except they are modern but it great to see you got it spot on, by ear. :blush:

 

Never meant to worry you but now is the time to check just to be sure

 

 

best regards to you and your crew lofty

Edited January 5, 2013 by k2lofty

[TOM MODEL T]

Hi Steve

 

I had excessive end float on the 1923 Ford Model T engine. The white metal was in excellent condition and I did not want to re-metal. I had 2 new thrust washers machined from a good quality brass. The original white metal thrust surface was machined down, the crankshaft surfaces trued up. The new thrust washers were pinned to the block and cap and the end play re-set to .002". Have completed 5000 km since and all is fine.

 

Have you tried the following link for pistons?

www.egge.com

 

Regards

Tom

Edited January 5, 2013 by TOM MODEL T

[Great War truck]

We are just returning our attention to the Water Pump so that we can get that finished – the attached photos of an “onion” is in fact a shroud designed to cover the drive pulley and drive belt for the pump – and it also contains a bearing to support the end of the water pump drive shaft. It was cast in aluminium and is very much showing signs of wear and age with a great deal of its flange broken or rotted away.

 

We had hoped that it might be possible to remove the remainder of the broken flange – make a new flange and weld that to the main part of the “onion” – but a test weld on a part of the flange that would be removed in any case reveals that the original aluminium is very contaminated – and probably was not very pure when the item was made some 95 years ago - so it will not weld.

 

A disappointment as it now means more pattern making so that a completely new “onion” can be cast.

 

 

 

 

[Barney]

Just to give a possible reason for the markings on the gears I give an instruction for replacing timing gears on the Morris VS15M engine that was fitted to Morris Oxford cars in the series MO, II, III and V and other derivatives.

 

The VS15M engine is gear-driven. These gears are paired and if replaced the new gear must bear the same markings as the original. The gears are marked with the letter “T” and in addition are marked with a minus figure from 1 to 6. The sum of the markings on both gears must equal minus 6, e.g. a crankshaft gear marked -2 must be mated with a camshaft gear marked -4. Either gear can be renewed individually provided that these tolerances are observed.

 

Presumably this arrangement is to give some tolerance during manufacture as was done with piston and bore markings.

 

Is it not possible to clean up one set of original gears and shafts then using a motorcycle crankshaft protractor and dial gauge check the point at which the inlet and exhaust valves lift on the best part of the gear and cams. Then swap the gears/shafts around to what you require and recheck. Make sure that the tappet clearances (say 10 thou) are readjusted to the same reading if you change camshafts.

 

If only I lived closer, Tony???

 

Best regards. John

[Barney]

After receiving some feedback I feel I should clarify my post (No 579) on the knocking noises caused by worn crankshaft thrust washers.

I believe this scenario to be very rare and I only encountered two engines that exhibited this problem. Both were four cylinder engines built in the 1930/40’s with chain driven camshafts; both were well worn but were running quite nicely without too much other noise.

Unlike the rhythmic vertical forces exerted on the crankshaft during the firing stroke there are no similar forces applied to the crankshaft in the horizontal plane. Any horizontal movement of the crankshaft is totally random*, other than when the clutch is depressed, so the knocking noises, in the two engines I encountered, were also random in that a few knocks were heard then silence, then a few more knocks and silence again, etc, etc. The number and intensity of knocks and the time length between them was totally random and there was no pattern that could be discerned.

The easy way to check for this problem is to depress the clutch slightly but not so far as to reduce the engine speed. This will force the crankshaft fully forward (or backwards in modern engines) and stop any horizontal oscillation whereupon any knocking from this source should cease.

Please accept my apologies if I have misled anybody.

* This may not be true in engines like the Thornycroft where helical cut timing gears are fitted.

 

Best regards. John

[Asciidv]

Were those bird droppings on the water pump housing from a MIG pigeon or a TIG pigeon?

 

Barry.

[Old Bill]

Thanks Matt and Lofty.

 

An instant explanation of how to do it! I shall check the timing the next time I go down to Devon and see what we have.

 

I think you are right, the numbers must refer to matching sets of gears. The gears are keyed to the camshafts so there is no adjustment. I guess they just selected sets in the factory. This might explain why the big ends are numbered 17, 18, 21 and 22.

 

Cheers!

 

Steve

[Old Bill]

Crank End Float

 

Thanks for that Tom. I will eye up the job the next time I go down and see how easy it might be to do.

 

Thanks also for the supplier suggestion. I had not seen their name before but they look like just the right sort of people to help us out.

 

This forum is wonderful for all the help so freely given!

 

Cheers!

 

Steve :-D

[philb]

I wouldn't give up on that pump casting without trying Alutight/Technoweld. Many of us have successfully repaired parts that would otherwise have been scrap.

[Minesweeper]

Were those bird droppings on the water pump housing from a MIG pigeon or a TIG pigeon?

 

Barry.

 

Sorry Barry - I didn't answer this one earlier - it was TIG Pigeon!

 

Tony

[fesm_ndt]

Sorry Barry - I didn't answer this one earlier - it was TIG Pigeon!

 

Tony

 

If you guys want I can ask around at my company TWI as some of the PHD's might have some ideas on what causes it or maybe how to reverse it? We get involved in a lot of welding research

[Minesweeper]

If you guys want I can ask around at my company TWI as some of the PHD's might have some ideas on what causes it or maybe how to reverse it? We get involved in a lot of welding research

 

Thanks, Mike - it would be quite interesting to hear what experts have to say about it - but we are quite resolved now to making a pattern and casting a new one. We understand that old aluminium castings - this one is about 95 years old - were generally made in a poor quality aluminium which does not weld well, even when it is clean and this one being porous has soaked up a lot of "muck" over the years which makes it even more difficult. On top of that, there is sign of wear through "belt rub" so it really has seen better days.

 

Nevertheless, we always want to learn and will be most interested in having an opinion from the professionals!

 

Tony

[fesm_ndt]

Thanks, Mike - it would be quite interesting to hear what experts have to say about it - but we are quite resolved now to making a pattern and casting a new one. We understand that old aluminium castings - this one is about 95 years old - were generally made in a poor quality aluminium which does not weld well, even when it is clean and this one being porous has soaked up a lot of "muck" over the years which makes it even more difficult. On top of that, there is sign of wear through "belt rub" so it really has seen better days.

 

Nevertheless, we always want to learn and will be most interested in having an opinion from the professionals!

 

Tony

 

you know, your one line explanation most likely sums it up really well, as aluminium is a curse to weld really well if got contaminants on it. Being porous like you say the contaminates are inside. I asked one of the top guys in our office as I know we were involved in some Hurricane repairs a few years back, so I am really curious also as we have some really advance stuff in the labs in Granta Park.

[fesm_ndt]

I got this response from the head office.

 

Couple of things to consider:

 

1. Is it a casting? By age it could be a very poor quality casting with extremely poor weld ability.

2. Is it a engine block / cylinder head etc, if yes could be impregnated with oil which will have a profound effect on weld ability.

3. If possible clean the casting (insignificant bit) back to bright metal and see if an arc (TIG) can be initiated / develop a weld pool, try adding filler wire, possibly AlSi 4043 type.

4. Alternatively, have the casting analysed to establish composition.

 

They could go into it deeper, way deeper as it's a fascinating place.

[Stormin]

A technique I've read about with regard to welding poor quality ally castings is to turn up the AC balance (most modern ac tig have this feature) and pass oer the area with the torch a few times to clean up the metal, after mechanical cleaning first of course.

This melting of the surface helps to remove hidden impurities. After several passes of just the torch then you can think about adding filler wire to actually fuse the pieces together.

 

Lots more good advice can be found on the Mig welding forum which also covers Tig and other workshop practices.

 

http://www.mig-welding.co.uk/forum/forumdisplay.php?f=22

 

Im sure some of the members on there would be keen to hear about your project.

 

I know your pattern making skills are considerable but it would seem a shame to lose an original item that can be restored despite the wear and tear.