WW1 Thornycroft restoration

Thats what these forums are for, to help each other out.

John G

The first brake drum is off:

The engine needs very little done to it now before it can be dropped into the chassis – but there are a whole number of jobs that need to be done first of all before we can “plonk” it in!

Essentially , we need to get the chassis underneath the Block and Tackle – but before we can do that, we need to get it on its wheels. The front springs are now hanging in position and the front axle – minus the swivelling ends is also hung temporarily in position. The front wheels are now in Bedfordshire where the old tyres will be pressed off this weekend. We have “new” good second-hand tyres to go on to the wheels – but the hubs need skimming on a big lathe before the sound replacement tyres are pressed on. This will now follow as and when those tasks can be fitted in. With the larger diameter hubs after the skimming, we shall have to get larger diameter bronze bearings.

We have been tackling the rear wheels – after sand blasting, it became very apparent that the Brake Drums – or Rings will need to be skimmed but we are not sure if there is enough metal there to allow for that. We have already mentioned the choices that we have – cast new “drums” in line with the later pattern, fabricate new steel ones – or the latest suggestion is that we go for metal spraying to build up where the old metal has gone – and this latter option is now being explored. So no final decision made on that one yet.

In the meantime, we need new back tyres – we do not have any. Last year, we obtained a quotation to have four new back rubber tyres made – they are “twins” on the back – and the quotation for that came out at £3,600 – more than a little frightening. On the Dennis, we opted to go for polyurethane and they came out at just £170 each – so £680 for the lot. We have always been concerned that perhaps with the Dennis, we could have made the wrong decision – but they have been fine. The initial shininess has worn off and they can be easily mistaken for rubber tyres.

The quotation for the Thorny – nearly 10 years after the Dennis ones were made came out at £200 each – so really, the choice again is made for us.

The polyurethane tyres are made on the steel bands of the old tyres – so those tyres must be pressed off as soon as possible and taken to the Polyurethane Tyre manufacturer who has the facility to remove the remains of the old rubber – and the new tyres will be bonded to those steel bands.

One of the steel Brake Drums has already been taken off the first rear wheel with the second one still to be done. The first one proved to be very difficult to move – it rather looks as if they were attached to the wheels with fitted bolts – and after this great passage of time, they did not give in easily!

We need new Shackle Pins for the Back Springs – new pins for the Front Springs were made some time ago and are fitted. The back Shackle Pins are very similar but bigger. They are in two patterns – a rather heavier one for the fixed link at the front of the rear spring and slightly smaller ones for the rear of the rear spring. Just one pin required for each of the fronts of the rear springs, but the rear of the rear spring is on a swinging link so that there are two of these pins to be made for each spring – so a total of six altogether for the rear springs in two different sizes.

The new rear springs were made some time ago – they need cleaning and painting and bronze bushes pressed in one end of each.

Making the Shackle Pins is really just a repetition of the process that we followed in making the front ones some time ago. The steel used was EN8 and the pins are made from a length long enough for two so that they are machined back to back with always enough of the length available to hold it during the machining process.

We already had some 1 1/4” EN8 in stock – it had to be turned down to 1 1/8” with a 7/8” Whit thread screw cut on the end for the securing nut.

The machined length is then cut into two at this stage, ready for machining the other end.

Each length then goes back into the lathe to be machined to correct length – drilled 3/16” through to about 2 7/8” inches length for lubrication purposes. The end is then opened up with a 29/32” drill to be tapped 1/4” BSP for a Greaser.

The remaining jobs to be done on these are a “through hole” in each about half way down to join up with the long 3/16” hole to allow the passage of grease through to the bearing surfaces. Holes have to be drilled for the 3/16” “feathers” and spanner flats have to be machined on the ends. And then finally, a through cross hole in the 7/8” Whit thread to allow for a retaining split pin for the slot nut.

These two shackle pins will now be put to one side at this stage to await the other four slightly smaller pins to reach the same stage and those final holes in all of them can be drilled at the same time in the same set-up required for that. Similarly, with the Spanner Flats – all can be machined at the same time.

Tim, I was contemplating tyre profiles. Do you have a cross-section you can show us for such profiles - both for and aft if they are different? Robert

Including measurements...!

The tyres on the Thorny were identical in size to the ones on the Dennis and these are the two sketches that were prepared for the Dennis Tyres when we had them made. We shall use the same ones again.

Brilliant. That all important 10 degree slope. And I see you used the same profile for both for and aft.

I shall compere this against tyres I have come across. Thank you. Robert

We have had a family get-together in Devon to take the lorries to Honiton Hill Rally and also visit the Great Dorset. In between times, we have found some time to put some more of the engine together. The first block was fitted in January but the other one has been sitting on the floor ever since! Steve had scraped in the big ends a while back so we were ready to fit it.

Step one was to dust it all off and then oil the pistons and bores.

Then, using the trusty chain block hung from the door frame, we lifted the block and gave the water connection a liberal coating of Red Hermetite which is, sadly, no longer available.

Then it was simply a case of lowering it onto the pistons whilst Steve compressed the rings into the bores.

A wangle to get the gasket into the water connection and it was down.

When we did the first block, we were asked why we drop the block onto the pistons rather than fit the pistons into the bores and drop the lot onto the crank. Our reasoning is that with a fixed-head engine, there is the possibility of pushing the piston too far up the cylinder and allowing the top ring to pop out locking the piston into the bore. Having done this before (and got away with it!) we didn’t want to take the risk again.

We then dropped in all of the lovely new valves, made for us by G & S in Godalming. These are a beautiful job exactly as per the originals. Unfortunately , we hadn’t quite thought out that when the valve seats were re-cut, they would be lowered so that when the valves were installed, all of the tappet clearance would be lost!

Our solution to this was to remove 1/16” from the end of each valve using the Dremel and face the ends of the tappets which were showing signs of wear anyway. A quick search for the giant valve spring compressor, previously made up for the Dennis and they were soon installed all round.

The next task was to install the plugs over the top of the valves. On all of our previous vehicles, these have simply screwed in with a copper washer. However, Thornycrofts, in their wisdom, made them simple plugs, ground into a seat and secured with a bolt on the top. Step one was to grind these in and the next photos show the plug covered with grinding paste, Steve grinding one in using a socket on the plug and then the finished surface.

Once this had been completed, the joint surface was coated with Red Hermetite and the new bayonet cap, made by Father a long time ago and kept in stock, was fitted and screwed down.

This was repeated for all of the exhaust valves leaving the engine a few steps further forward.

The next time we get together we will do the inlet valves and sump. Still plenty to do!

We have had a family get-together in Devon to take the lorries to Honiton Hill Rally and also visit the Great Dorset. In between times, we have found some time to put some more of the engine together. The first block was fitted in January but the other one has been sitting on the floor ever since! Steve had scraped in the big ends a while back so we were ready to fit it.

Step one was to dust it all off and then oil the pistons and bores.

Then, using the trusty chain block hung from the door frame, we lifted the block and gave the water connection a liberal coating of Red Hermetite which is, sadly, no longer available.

Then it was simply a case of lowering it onto the pistons whilst Steve compressed the rings into the bores.

i still have a pot of stag..someware....

anyway....what i like about this thread is the way progress is in trunches...like installments....

it allows us all to scroll through....then await the next episode..

riveting stuff boys...crack on...

Like the to do list on the door.

Especially agree with the last item.

Magnificent!

More progress and less bits on the floor:

More progress and less bits on the floor:

[/quote

that gasket material you have used on the crankcase inspection covers....is that stuff made by flexitallic?....as they are fairly local to me (cleckheaton)...

that gasket material you have used on the crankcase inspection covers....is that stuff made by flexitallic?....as they are fairly local to me (cleckheaton)...

I don't know who makes it. It came in a roll from Beaulieu Autojumble years ago!

Steve

It is a shame you don't see those pistons any time soon,

they are just lovely

it is a nice sight to see bolting parts together,

on a different note, were you on the war and peace this year and got a issue with sunk wheels on the last day?

i made some film of a old lorry being stuck in the grass, i just loved the sounds it made.

When we did the first block, we were asked why we drop the block onto the pistons rather than fit the pistons into the bores and drop the lot onto the crank.

You are correct - However, many times you will find these old T-heads with bent rods. As you have probably discovered its very easy to have things jamb-up and the rods take the weight of the block if the pistons get a bit off kilter.

A while back I was helping my brother pick-up his airplane after its annual - while chatting with his mechanic he mentioned how with the old engine when valves would stick he would take-out a spark plug, insert a length of nylon rope into the bore. When he cranked the engine over by hand the piston compressed the rope and pushed the offending valve closed. The rope could be easily removed since one end was left hanging out the spark plug hole.

Needless to say... one could use a length of rope coiled-up in the combustion chamber to keep the pistons from sliding too far up and popping a ring over the top of the bore. Once the block is suspended upright over the crankcase with straps holding the piston in you could pull the rope out and lower the whole assembly in place.

Just a thought....

On another note... its great to see the engine going together - I cannot wait to here it run. You mentioned scrapping in the bearings - are they cast-in-place Babbitt or are the bronze backed Babbitt shells?

Best regards,

Terry

On another note... its great to see the engine going together - I cannot wait to here it run. You mentioned scrapping in the bearings - are they cast-in-place Babbitt or are the bronze backed Babbitt shells?

 

Best regards,

 

Terry

The shells are solid white metal castings with no backing. They are about 1/4" thick and simply dropped into the crank case and onto the ends of the rods. I have not seen them like that before!

Steve

I ran into a similar type in a 1909 Jackson. The mains were simply machined Babbitt inserts with no backer. They were indexed in the crankcase and caps with steel dowels.

Here you can see the aluminum caps and the two Babbitt "inserts". I am assuming they did it this way because of the difficulty of bonding poured Babbitt to aluminum.

Yes, just like that!

Steve

I have the great good fortune to have a few days off this week. Mostly, they are dedicated to chores but I did find a couple hours to go in the shed yesterday and have a look at the engine breather. This is a simple bronze elbow, bolted to the top of the crank case and directed into a thin steel tube which brings the hot air from the exhaust manifold to the inlet to the carburettor. There is no seal. The casting just pokes into the side of the tube. Over the years, vibration of the tube has eaten into the side of the elbow.

Step one was to cut the end off and trim it back with a file.

Then I turned up a new end in gunmetal.

Silver soldered it on. (My favourite process!)

Dressed it off with a file so it is all ready to fit. Unusually, the joint is showing but I don't think anyone will notice.

Back to the chores!

Steve