WW1 Thornycroft restoration

[David Herbert]

From your photos it looks like the drum on the NZ starter shaft is considerably eccentric to the shaft. How would that work? Presumably it is not some sort of harmonic ballancer?

 

David

[Minesweeper]

From your photos it looks like the drum on the NZ starter shaft is considerably eccentric to the shaft. How would that work? Presumably it is not some sort of harmonic ballancer?

 

David

 

Yes, it is eccentric - I cannot explain it - but better brains than mine will!

 

Tony

[Gordon_M]

Tch, think about turning a starting handle by hand ... It turns easily till it is on compression and then you need maximum leverage, so there will have been some sort of rolling starter bearing on the outside of that rubber.

 

When it is at the 'close to the crankshaft' part of the orbit you will have maximum turning speed, when it is at the 'furthest from the crankshaft' part of the orbit you will have maximum leverage for the compression part of the cycle.

 

..... and before you ask " why didn't they just make it one big diameter then, to get the same leverage / applied power all round" that would reduce the overall RPM considerably and reduce the chances of a start.

 

Very sneaky - not stupid, our ancestors.

[Asciidv]

Gordon,

 

May we have a sketch please? I think what you are proposing all sounds a bit too fanciful!

 

Barry.

[Barney]

Re; Starting Handle Shaft.

 

It looks to me as though the shaft turns inside the eccentric component and as there also appears to be a greaser to lubricate the shaft my thoughts are that the eccentric is an outrigger bearing for the longer shaft and the rubber gives a resilient mounting into a circular bracket that bolts onto the front chassis cross member.

 

Best regards. John

 

Edit;

 

The mounting bracket suggested is more likely to have been a pot shape rather than just a circle, the studs coming through rubber grommets in the front of the pot and nutted up to hold it all in place.

If the engine is not resilient mounted then perhaps, as Tim says, the unit is from a later lorry or another application, a resilient mounted generator perhaps.

 

Edited February 8, 2013 by Barney

[Gordon_M]

Gordon,

 

May we have a sketch please? I think what you are proposing all sounds a bit too fanciful!

 

Barry.

 

Cor, if only we had an on-screen sketch tool Barry ...

 

I'm just suggesting that's how it works - if I'm looking at the image right that very much suggests itself, can't really state it in much more detail.

 

Think about turning an engine over by hand to start - you want it to turn quickly, but when it is on compression you slow down as the load rises - I just see this eccentric as a way round that.

 

Gordon

[Old Bill]

I have just been digging through the early pictures for this project, from before the digital age, and have found this one taken whilst we were opening the crate. As you can see, it appears simply to be a resiliant mount for the handle. I find this a bit odd as it is massive overkill for the purpose. However, I am wondering whether it was originally intended as the front mount for the engine itself? The M4 engine doesn't show any signs of mounting holes in the front to accept it but we have always been a bit puzzled by the sub frame as it looks nothing like anything else we have ever seen. I am questioning whether the engine was a replacement mounted on the frame at a later date and therefore inherited the starting arrangement. We shall probably never know but I am now intrigued!

 

Steve

[Gordon_M]

Hmm, jury still out then It would certainly act as a resilient mounting point .... Here was me thinking it was cleverer than that. Looking at the way it is bolted to that workmanlike steel frame I cant see it needing a mount, unless something else drove through it / round it / in line with it.

[Barney]

Steve,

 

If you look carefully at an enlargement of this photo you can see that the front cross member is curved downwards and where the starting handle passes through the member you can see two bolts/nuts to the right hand side the shaft, presumably there are two others on the side that is hidden by the shaft. It looks very much like this lorry has a similar starting handle arrangement to the resiliant mounting unit you have; the shaft and bolt/nut orientation look to be the same.

 

Best regards. John

Edited February 8, 2013 by Barney

[Great War truck]

Something else we tried to do last weekend was to fit the inlet camshaft. Firstly, Steve's new governor bits were installed.

 

 

 

. Unfortunately, it rapidly became apparent that the camshaft was not going to go so it was pulled out and the governor bits were inspected. Steve had forgotten that the pivot points on the yoke were below centreline so he had made the actuating arms too long.

 

 

He was not happy! He has spent today cutting them back and then silver soldering on some new ends. In order to keep them in line, he machined the ends on a piece of bar but did not cut it through until after it had been soldered. This worked well and the shaft is ready for the next try.

 

 

 

[nz2]

The photograph of the heavy subframe is certainly different in size and form. I would suspect it it from an industrial application as the subframe used on the Thornycroft J trucks is considerably lighter. The front cross member as shown is not like that on the J series. The very late J's and KB series using the AB4 engine had a 3 point engine mount system the front mount was in a rubber bush but again considerably smaller that that shown in the photo. The curvature of this mount ( upwards) is the opposite to that of the trucks with the mount being flat on the top.

The photo from the Flika account is from the Brunt Collection in Victoria Australia. The crank start mount is attach to the front cross member underside. The alloy seen in the photo is the front of the sump.

That truck has a radiator mounting which appears to have a non original top tank and different side mounting points. Unfortunately my photos of that truck show detail about the engine but not the radiator. They do show a series of radiator hoses traversing across the front of the engine to the lower tank on the right hand side. It would appear this radiator is from another vehicle may be a Leyland.Note there is no name on the top tank. It also had no radiator fan nor mount for it.

Doug

[Redherring]

Colac is local to me and I have been looking for an excuse to go visit Merv.

[Old Bill]

Colac is local to me and I have been looking for an excuse to go visit Merv.

 

If you get the opportunity to take a few more detailed pictures we should love to see them please!

 

Steve

[lynx42 Rick Cove]

Colac is local to me and I have been looking for an excuse to go visit Merv.

 

I see why you call yourself Redherring.

 

Local? 152km and about 2hours travel is not too local. Still say G'day to Merv. He has one of my Albions on show. It came from Orbost/Marlo area many years ago.

 

Regards Rick

[Redherring]

That's the thing about reherrings... we can be misleading... Robert :angel:

[Great War truck]

When we took the engine apart, it was evident that a water inlet to the pump had been broken off.

 

 

 

The first task sorting this problem was to identify what it should look like. A complete original can be seen in this photo of the Sandy Bay charabanc engine and the Carleton Colville lorry. Steve also had the great good fortune to be able to visit the owner of an Alldays and Onions tractor into which had been installed a Thornycroft engine and take a couple of close-ups.

 

 

 

[Great War truck]

After the usual fight, the water pump was dismantled and the inlet casting revealed.

 

 

As you can see, it proved to be quite a complex shape so Steve sought advice about how to put the pattern together. One of his pals, Adrian, suggested that rather than replace the whole casting, he simply make up the spigot and he (Adrian) would weld it on for him. Well that made the job a lot easier so Steve set about making up the pattern.

 

 

After making up the plug, he put it through the bandsaw to split it. The material lost due to the cut was replaced by sticking on layers of 1/32” plywood and then dressing to shape.

 

 

 

 

[Caddy]

I love all the work that has been done, and I find myself becoming addicted to this thread.

 

Can't stop my jaw from dropping open either

[Asciidv]

Steve, why has the top core print an inverse taper rather than being just parallel like the bottom print? Does this part really need a core at all as you could mill out the water passage?

 

Barry.

[Great War truck]

Next came the core box. This was made by laminating MDF and once again cutting in half, making up the lost material with plywood.

 

 

 

To aid the removal of the core and give strength to the final casting, fillets were added to the inside of the core box using ‘fillet leathers’ simply glued in. Steve was extremely fortunate in that whilst wandering a disused part of the factory where he worked, he found abandoned in a cupboard, a box of fillet leathers. The works foundry and pattern shop were long gone and it seemed such a shame to waste them!

 

 

The pattern and core box were then painted using Bondaprime and rubbed back to give a smooth surface. This is really a zinc anti-rust primer but it soaks into the MDF very well, hardening the surface and allowing the second coat to be rubbed back to a very smooth, matt finish.

 

 

[Great War truck]

Father then took them to the local foundry where the spigot was cast in grey iron. The mould boxes unfortunately, misaligned but it was not serious and there was plenty of metal to cut the casting back.

 

 

 

 

 

Then came the task of fitting the spigot to the main casting. Firstly, the casting was dressed back to give some reasonable edges with which to mate.

 

[Great War truck]

 

 

 

Then Steve cut a plate to hold the two bits together.

 

 

[Old Bill]

Steve, why has the top core print an inverse taper rather than being just parallel like the bottom print? Does this part really need a core at all as you could mill out the water passage?

 

Barry.

 

Hi Barry.

 

Initially, I was concerned about the core floating off or simply moving. In hindsight, I think I would have got away without the dovetail but I am still not very confident about pattern making and make it up as I go along. Fortunately I have had some guidance from chaps on the Dennis thread and with my background reading have had some reasonable success. As you can see, though, my castings tend to be a bit thicker than the originals which is probably why the Dennis water pump weighs 31lbs!

 

Milling out the passage would have been possible but a lot of work. My mill is only a glorified drilling machine and doesn't have enough stroke on the quill to reach the end. Also, my lathe isn't big enough to have bored out the circular hole. Cutting the MDF proved a lot easier! Of course there was quite a lot of work in the pattern and I can't see it ever being used again unless we have a disaster. Still, it has served its purpose.

 

Steve

[Great War truck]

The whole lot was passed to Adrian who very kindly welded them together.

 

 

Whilst discussing the job, Steve commented that hadn’t worked out how to get the old white metal from the bearing and out of the stuffing box. ‘Leave it to me!’ says Adrian and proceeds to melt it out using oxy-acetylene. Steve was very concerned about cracking the iron but it became no more than hand hot due to Adrian’s care in only warming the white metal. You certainly find out who your friends are in this hobby!

 

 

 

 

 

 

[Great War truck]

Then it was home for a clean-up. The welds were machined off flush and the radii dressed with files and a flap wheel.

 

 

 

 

Next step was to give the assembly a pressure test so the holes were sealed with steel plates and a bit of rubber and 10psi air was applied. Unfortunately, the joint proved a lot more porous than had been hoped with various pin-holes. This was not completely unexpected as the casting is very thin, old iron and does not weld well, even with the pure nickle rods Adrian had selected. Steve plans to machine the weld out in the worst position so Adrian can have another go and then try to suck Loctite into the remaining pin holes. We will let you know how we get on!