WW1 Thornycroft restoration

[Great War truck]

When we first obtained the chassis from under the Shepherd’s Hut, the front springs were “finished” and on the near side, the fittings holding the spring to the front axle on that side had disappeared entirely. To enable us to move the chassis, a very temporary fitting was made up, just to hold everything together.

 

The one top keeper plate remaining – or properly named in the Parts Book as a “Strong Back” was in very poor condition – but fortunately there was enough information available from it to enable us to make two replacements. Presumably, the originals were either castings or forgings, but we thought that steel fabrications would do the trick.

 

Laser cutting seemed to be the easiest way to make these parts but the total overall thickness was too much for our local man to deal with – to cut in one piece, and then it would have been necessary to mill a slot down the middle to accommodate the rectangular plate on top of the spring being part of the assembly holding the leaves together.

 

So instead, we opted to have three pieces cut for each so that the two smaller edge pieces could be welded to the main plate, but leaving the required slot. The three bits were held in their correct positions for welding with temporary nuts and bolts.

 

[Great War truck]

The finished “Strong Backs” –the three bits of each welded together with the weld tidied up and then primed.

[andypugh]

"Strongback" is a phrase that my granddad used to describe some of his tools. (I am the first non-engineer in my family for 3 generations). One of them was a thing for straightening things, with screws and V-blocks.

I think it is a generic term for something that bolts pass through to deform something weaker. Like pulling a leaf-spring together.

[paul_bish]

nice solution to the problem

[Asciidv]

What a lovely job! A very nice square in the centre, those special square drills you bought have have certainly come in handy! I am however puzzled as to why you didn't start off with a bit thicker plate and then just milled the channel in? Best wishes, Barry.

[Asciidv]

......and now when I look a little closer did you cheat and have them laser profiled!?

[Minesweeper]

That reminds me of school when our Teachers used to say - "Make sure you read the question before you answer!"

 

Tony

[Asciidv]

Yes, I own up! I only looked at the pictures! Somehow I missed the words that explain all...:nut:

Edited March 30, 2014 by Asciidv

[andypugh]

What a lovely job! A very nice square in the centre, those special square drills you bought have have certainly come in handy!

 

I can bore square or hexagonal (or pentagonal, for fun) holes on my lathe.

[rewdco]

I can bore square or hexagonal (or pentagonal, for fun) holes on my lathe.

 

You're making me very curious Andy! I have seen these Chinese tools for drilling square holes on YouTube (

), but I guess this is not what you mean?

 

Jan

[andypugh]

You're making me very curious Andy

[rewdco]

Very nice Andy! Never seen anything like that before!

 

Jan

[Asciidv]

Here is a U.K. supplier of those special drills for drilling square holes. They are not particularly cheap!

 

Barry

[rewdco]

Only available today I guess...? )

 

Cheers,

Jan

[Caddy]

Along with the tartan paint

[mattinker]

It is perfectly feasible to drill square holes using a rotary broach. The attached video is for drilling hex holes, but a square, hole is done using a square tool!

 

 

 

 

Regards Matthew

[flandersflyer]

When we first obtained the chassis from under the Shepherd’s Hut, the front springs were “finished” and on the near side, the fittings holding the spring to the front axle on that side had disappeared entirely. To enable us to move the chassis, a very temporary fitting was made up, just to hold everything together.

 

The one top keeper plate remaining – or properly named in the Parts Book as a “Strong Back” was in very poor condition – but fortunately there was enough information available from it to enable us to make two replacements. Presumably, the originals were either castings or forgings, but we thought that steel fabrications would do the trick.

 

Laser cutting seemed to be the easiest way to make these parts but the total overall thickness was too much for our local man to deal with – to cut in one piece, and then it would have been necessary to mill a slot down the middle to accommodate the rectangular plate on top of the spring being part of the assembly holding the leaves together.

 

So instead, we opted to have three pieces cut for each so that the two smaller edge pieces could be welded to the main plate, but leaving the required slot. The three bits were held in their correct positions for welding with temporary nuts and bolts.

 

invest in some bottles and cutting gear, bagging etc...

 

you could have got the torch out to make these....burn `em out of a bit of plate....

[Great War truck]

We took the opportunity of looking together at the “new” front wheels for the “Thorny” where you may recall that the hubs are badly worn and will need some work before they can be used. We have decided to use those wheels but get the hubs “skimmed” out – we reckon by about 5/32” – where there is enough “meat” to allow for that so that the bores are true again. New Bronze bearings will have to be made with an appropriate larger outside diameter to fill the larger bore.

 

We had to have the front wheels of the Dennis similarly bored out as they were heavily rusted. Before that was done, we removed the old tyres from those wheels and had the wheels sand blasted without the tyres. That was the mistake as when we refitted the wheels with new tyres, the new tyres dropped loosely on to the wheels – and we had to pack them out with a steel shim and canvas. All of the rust on the wheels helped to keep the tyres firmly in place and the sand blasting had effectively reduced the size of the wheels.

 

So with the “Thorny” wheels, we shall get them sand blasted now with the old tyres left on to protect the rims – prime the wheels to protect them from rusting and arrange for the hubs to be bored out– and then get the old tyres pressed off and the new ones pressed on.

 

With sufficient man power available, we lifted the front axle out of the shed so that could also be prepared for sand blasting. The King Pins needed to be taken out and the stub axles removed – we knew from previous experience that King Pin locking bolts can be a devil to remove but were agreeably surprised when the nut on the first one easily unscrewed and the bolt just knocked out.

 

The retaining bolt on the other side was a completely different matter. Whilst the nut came undone, there was no way that the bolt could be knocked out – heat did not do the trick and we eventually screwed the head right off the bolt – so drilling it out was the only answer. We went in half way from each side, gradually opening up the drilled holes so that there was only tiny bit of the walls of the bolt remaining in the hole. These were knocked off with hammer and chisel and the remains of the bolt eventually came out.

On the side where the retaining bolt came out easily, we found that the bolt was 3/8” in diameter where it should have be 7/16” – the bolt on the other “tight” side was in fact the correct 7/16” diameter – and that is why it was so much tighter and had to be drilled out. We guess that some time during its working life, the mechanic working on it at the time had the stub axle off and possibly did not have a correct 7/16” bolt to go back in the hole and he used a 3/8”one instead – or he found it too tight to get a 7/16” one back in again and used a smaller size for his own convenience. As the bolt was undersize, the King Pin had revolved where it should not have done during its working life and that would explain the wear on the bolt which is clearly visible in the photograph.

 

The “working party” has dispersed again – but there should be two of us here next weekend and for a few days afterwards when we plan to take the axle to a local garage where there is a big Press so that we can use that to get the King Pins out – and also move the Wheels over to the Sand Blaster to get them cleaned.

 

[Gordon_M]

Good stuff. I take it you will save that King Pin by welding it up and machining back down? I know you could make one but repairing the original would seem to be the thing to do?

[Minesweeper]

Good stuff. I take it you will save that King Pin by welding it up and machining back down? I know you could make one but repairing the original would seem to be the thing to do?

 

We need to have a look at it - so will make the decision when we have taken it out!

 

Tony

[Redherring]

Tony, I was interested to read about sandblasting and loss of the interference fit between rim and tyre. We were talking about this very thing last weekend. Is there a way of measuring outer rim -v- inside tyre to ensure the "perfect interference fit"? How was this done in days gone by? Robert

[andypugh]

Is there a way of measuring outer rim -v- inside tyre to ensure the "perfect interference fit"? How was this done in days gone by? Robert

 

The wheel OD can be very easily and accurately measured with a tape measure. Preferably a Pi-tape with a vernier section.

http://www.ebay.co.uk/itm/NOS-USA-PI-600-900mm-Outside-Dia-Tape-4-Lathe-/390313145714?pt=LH_DefaultDomain_2&hash=item5ae079f572

 

The tyre bore is more difficult. It probably isn't circular, for a start. Readings at several positions with an internal micrometer is probably the best way to get an idea.

 

While I am spending your money: http://www.machine-dro.co.uk/digital-dial-vernier-calipers/1000mm-40-digital-caliper.html

[Redherring]

Ahhh. I understand the Pi tape. We use the same tape - though plastic; so nowhere hear the same accuracy - to measure tree diameter on the way to determining tree volume!

[Redherring]

Ok. So what is the perfect interference fit?

[fesm_ndt]

With all the fancy adhesives around now would they have solved the Dennis loose tyre issue and prevent any further water ingress?

 

As i guess the Dennis and Thornycraft are not very fast.

 

Ps looked up king pin today as always amused at where some English words come from but didn't so far find any origins, but was a term used for the central pivot on wagons.