WW1 Thornycroft restoration

[Old Bill]

Now that the Dennis has a new home, I can get back to Thornycroft! Some projects just take far too long....

 

 

We are at a position where we want to get the back axle and wheels fitted. Then the engine and gearbox can go in and we will be lloking like a lorry at last. This is to be the Christmas project but before we can do that, we need to fit the brake drum dust covers as they cannot be installed once the axle is attached to the springs. The dust covers we had are very poorly so we have to make up some new ones.

 

 

A close inspection and reference to the photos taken of the Carlton Colville lorry showed them to be 20swg steel discs with a 3/4" flange around the outside and the centre dished inwards with a bead around it. The first task then was to make up a flanging block. This was simply a laser-cut piece of 3mm plate screwed to some 3/4" plywood. Whilst getting this cut, we also had two blanks done at the same time.

 

 

The blanks were sandwiched between the steel-faced piece of ply and a second piece to back it up. Then the edges were laboriously tapped over a bit at a time until they sat more-or-less flat around the block.

 

 

 

As the block was only steel faced I could not get the ripples out as the rather soft timber just deformed inwards.

 

 

Whilst wondering what to do about this, I remembered that Father had bought me a set of panel beating tools. I have never worked out how to use them but found that one of the dollies had a radius about the same as the flange. I held it up behind the flange by hand and tapped against it with the planishing hammer. This improved things quite a bit but the flanges are still obviously hand beaten by unskilled labour!

 

 

 

 

Two flanged plates resulted.

 

 

The next part of the job was to work out how to emboss the centre. I have recently acquired a 30tonne hydraulic press and thought that might be the answer so I turned up another steel faced tool, this time in mahogany.

 

 

 

 

The flanged plates are slightly bigger in diameter than the distance between the press legs. However, by tilting them, they would just fit in the middle. As usual, I am using all of my equipment to its capacity!

 

 

 

[Old Bill]

The ply started to bend so I needed to support it all round. In rummaging in the workshop, I found this ring which is the piece parted off from the brake drum. Perfect!

 

 

Off we went again but I was amazed when I reached 25 tonne without quite reaching the full depth.

 

 

To get the last bit of movement, I inched around the edge with the ram pushing locally. This achieved 9/16" when I was aiming at 5/8". I deemed this acceptable and proceeded to push the second one.

 

 

 

The result is quite pleasing but it was at this point that I realised I had reached the end of the stroke, 1/16" short of where I wanted to be! Very embarrassing and a lot of effort for the result. Oh well. At least I know how far the ram goes now!

 

 

Next task was to open out the bore as I had left it undersize to allow it to stretch. I marked it out with odd-leg calipers and then cut it with a nibbler before cleaning up with a file.

 

 

 

The beading around the edge of the hole had originally been formed by folding the steel over. However, I just could not see how to do this so we decided that a brass bead of similar section but riveted on would be acceptable.

 

 

The challenge then became how to bend it. This was done by drilling a hole through a block of wood and simply leaning on it. It was a bit painstaking but worked well..

 

 

It was at this point that my estimate of a 24" length of bead became noticeably too short so I riveted in an extra piece of flat and dressed it to match.

 

 

 

 

 

After dressing back, the bead was quite presentable.

 

 

 

The original remains seem to match anyway.

 

 

Two covers ready for the Christmas project.

 

 

Back to painting the Dennis' new home.....

 

Steve

Edited November 8, 2015 by Old Bill

[TrevWringe]

Great to see that you’re able to work on the Thorneycroft again. I’m still constantly staggered by your levels of skill and ingenuity! It’s wonderful to be able to watch your work as it progresses. Thanks very much for the effort that you put into this thread. It’s very much appreciated.

[andypugh]

This was simply a laser-cut piece of 3mm plate screwed to some 3/4" plywood. Whilst getting this cut, we also had two blanks done at the same time.

 

Possibly outside the capacity of your laser-cutterist, but if you had done the whole form in steel plate then that opens up the option of heating the flange with a blow-torch to make it easier to shrink the ripples out.

 

It isn't like some mild steel discs are going to sit around for long without finding other uses, is it :-)

[Old Bill]

I did think about it, Andy but it would have been a massive piece of steel and I would have struggled to handle it. The fuel tank ends are only flanged by 1/2" so I shall get steel flanging blocks made for them. The corner radii are only 4" for them so they will be harder still to flange.. No doubt we will get there.

 

Steve

[Asciidv]

Excuse me, but what happened to Steve Metal-Spinner Gosling?!!

[Chris Suslowicz]

Excuse me, but what happened to Steve Metal-Spinner Gosling?!!

 

I suspect the metal was too thick and too hard to spin. The originals were most likely pressings and beyond the scope of even the Gosling's facilities. (Which is a pity.)

[David Herbert]

Those back plates look great ! I wonder if it would be worth running some soft solder between the brass beading and the plate, partly to reinforce the joint and partly to prevent water getting in and rusting the steel in a place that will be almost impossible to seal completely.

 

David

[dgrev]

I suspect the metal was too thick and too hard to spin. The originals were most likely pressings and beyond the scope of even the Gosling's facilities. (Which is a pity.)

 

Well, not quite "unGoslingable", just requiring a different (and very impressive -as usual) approach to obtain

an equivalent result.

 

Reproduction pressings really are a challenge, no matter how well equipped and talented the restorer(s).

 

Lacking a 25 ton stamping press, doesn't seem to have scared them off.

 

Regards

Doug

[andypugh]

Reproduction pressings really are a challenge, no matter how well equipped

 

I used similar "hybrid techniques" to make some Ner-a-Car parts. The material was rather thinner, I suspect.

http://bodgesoc.blogspot.co.uk/2014/07/neracar6.html

[Old Bill]

Excuse me, but what happened to Steve Metal-Spinner Gosling?!!

 

That would have been a better way to do it but they are just too big for my facilities. I spun the fuel tank ends for the Dennis which are 16" diameter and 18swg and that was quite successful although I had to make up a bronze tool to do it. They were at the limit of diameter for our Colchester Student lathe though and these covers are 22" diameter so although only 20swg, I couldn't do them that way. I could have imposed on my friends again for use of a larger lathe but am keen not to become a perishing nuisance!

 

I originally planned to solder the brass to the steel but felt that with dissimilar metals their relative expansions would distort the covers. I cleaned them before riveting so I could still do it. Will give it some more thought.

 

Steve

[andypugh]

I originally planned to solder the brass to the steel but felt that with dissimilar metals their relative expansions would distort the covers.

 

You quite often see brass fitting soldered to steel tanks, so I don't think this is a huge concern, especially in a part that probably doesn't see such a huge temperature swing.

[andypugh]

I could have imposed on my friends again for use of a larger lathe but am keen not to become a perishing nuisance!

 

Now, if only you had just built a nice big shed at the side of your house, then you could put a decent-sized lathe in the end of it.

 

http://www.ebay.co.uk/itm/181925330600 looks to be shorter than a Dennis is wide (though he does say that the photo is not necessarily of the lathe he is selling)

[flandersflyer]

That would have been a better way to do it but they are just too big for my facilities. I spun the fuel tank ends for the Dennis which are 16" diameter and 18swg and that was quite successful although I had to make up a bronze tool to do it. They were at the limit of diameter for our Colchester Student lathe though and these covers are 22" diameter so although only 20swg, I couldn't do them that way. I could have imposed on my friends again for use of a larger lathe but am keen not to become a perishing nuisance!

 

I originally planned to solder the brass to the steel but felt that with dissimilar metals their relative expansions would distort the covers. I cleaned them before riveting so I could still do it. Will give it some more thought.

 

Steve

this wont be the problem

 

 

Electrolytic corrosion may well be though...in time...

[Great War truck]

These are two pictures of the Brake Linings that have been supplied and are to be fitted to the Brake Shoes. They measure 8” x 4” and are 3/8” thick.

 

They are totally rigid and have to be bent around to a much tighter radius to match the Brake Drum and Shoes. We do not think that they can be bent around cold as we think that they might break or crack. We understand that to re-form them, they should be heated and bent around whilst they are still hot – is this correct?.

 

Does anyone have any information or advice on how to do this please? 180 degrees oven heat has been suggested – and if that is correct, how long should they be left in the Oven? The Domestic Authority might not be over-keen on this operation.

[andypugh]

I bent mine in the oven, as suggested.

I put them in the oven on top of a former, then took them out and pushed them onto the former with a tea-towel.

 

However, if I was doing it again I would not heat the former, as it took a long and uncomfortable time for things to cool enough to take the set. I think hot material onto a cold shoe would be better.

 

You can always have a second attempt.

[Minesweeper]

I bent mine in the oven, as suggested.

I put them in the oven on top of a former, then took them out and pushed them onto the former with a tea-towel.

 

However, if I was doing it again I would not heat the former, as it took a long and uncomfortable time for things to cool enough to take the set. I think hot material onto a cold shoe would be better.

 

You can always have a second attempt.

 

Thanks Andy - what temperature and for how long?

 

Tony

[andypugh]

what temperature and for how long?

 

I don't remember, but it would have been whatever Saftek suggested. Probably on the phone, I can't find an email.

[andypugh]

I don't remember, but it would have been whatever Saftek suggested. Probably on the phone, I can't find an email.

 

Aha! I found that I mentioned it in the blog post that describes making the brake.

http://bodgesoc.blogspot.co.uk/search/label/Neracar9

 

This is a transmission brake just like the Thornycroft one, but just a little bit less hefty :-)

 

(And the answer is 200C)

[flandersflyer]

I bent mine in the oven, as suggested.

I put them in the oven on top of a former, then took them out and pushed them onto the former with a tea-towel.

 

However, if I was doing it again I would not heat the former, as it took a long and uncomfortable time for things to cool enough to take the set. I think hot material onto a cold shoe would be better.

 

You can always have a second attempt.

 

 

i suppose steaming them into the correct radius..(a bit like they used to do to get Lincrusta round corners) would do it..

[BenHawkins]

and if that is correct, how long should they be left in the Oven? The Domestic Authority might not be over-keen on this operation.

 

 

My Domestic Authority generally approves things going in the oven if they are wrapped in aluminium foil and don't smell.

[Great War truck]

Steve was in Axminster today and brought with him the newly made Dust Shields, just described. He wanted to trial fit them before passing them on to the “Axminster Paint Shop Sub-division” for completion. Very pleasingly, they fitted “like gloves” and they can now be painted ready for final assembly over the Christmas break.

[Great War truck]

Whilst Steve was in Axminster, it was a good opportunity to have that second pair of hands available to help shape the Transmission Brake Pads.

 

In accordance with advice, the Domestic Authority vacated the kitchen and the Top Oven was heated to 190 degrees. A piece of plywood was placed on the kitchen floor to protect it – one of the Brake Shoes was held in a large vice and placed on the Plywood as the curvature of that was to be used as the former for the Lining. The pads were placed in an old baking tray which was also protected with silver foil – “just in case” and all tools and clamps were placed to be readily available for the forming of the hot linings. A “lump” hammer was available to be used to press the hot lining into the shoe.

[Great War truck]

The linings were left in the oven for about 10 minutes and then hastily transferred onto the shoe whilst they were still hot – and pressed down at the centre of the shoe with the lump hammer, which was just being used as a pressing tool – not as a hammer! They pressed down fairly easily into position with that pressure on them and were then were quickly clamped down before they cooled off.

 

Now both the shoes and linings have to be drilled for final fitting. Not rivets in this case but four 3/8” Bronze bolts in each one, nutted on the outside – as per the originals.

[Great War truck]

These Brakes Shoes then had to be drilled 3/8” in four places to take bolts for attaching the linings to them. The linings on the rear wheel brakes were attached to their shoes with orthodox brake lining rivets but 3/8” bolts were originally used on the transmission brake shoes – and we have followed that same practice. After the holes were drilled in the shoes, the linings were clamped up to the shoes and drilled through and then held in position with steel bolts, pending further work on them.