Jump to content

WW1 Thornycroft restoration


Great War truck

Recommended Posts

Hi Steve,

 

is this youtube clip any use ?

 

 

 

 

Andy

 

Thanks Andy. Yes, that's a good one. There are several on Youtube and I have bought a DVD from this bloke as well. Sometimes, though, you just want to talk to someone! The trouble with these old lorries is that you need so many skills and it is very hard to obtain them all. Never mind. One at a time!

Link to comment
Share on other sites

 

My recent attempts at metal spinning have produced a lot of scrap:

 

But also some usable parts:

 

 

 

They look fine, Andy. What speed did you use and what sort of tool? I have used a bronze tool on steel in the past because my lovely hardened steel tools were ruined in no short order! Did you do them in one go or did you heat them part way through to reduce the cracking?

Link to comment
Share on other sites

They look fine, Andy. What speed did you use and what sort of tool?

 

A hardened steel tool, but also a roller and a beader. Actually the roller and the beader are the same home-made tool but with the roller swapped.

 

The lamps with a spigot were done in two stages. I found a bit of inexplicable plastic in the box (the patterns have been used a few times before, generally by pros) and it turned out to be a collar that spaced out the spigot to the main shape so that it was possible to get a "touch" on the main body before the tool torque ripped the spigot-end out. Then the spacer was removed and the spigot rolled to final shape.

Link to comment
Share on other sites

Steve

 

This spinning is a bit big for your lathe but I found this video very interesting for the number of different tools used, the two man operation and how they form up, roll and flatten the rim, shown near the end.

A long video I admit but if you get bored you can study the pictures on the wall ;)

 

 

 

John

Edited by Barney
Link to comment
Share on other sites

All done in one go? What sort of speed?

 

All in one go, though I did experiment with an extra annealing for the super-difficult lip. This is a picture of an original one:

http://www.geutskens.eu/neracar/images/PPL/8-Accessories/804-Headlamp%20Electric/09-Headlamp%20Electric,%20bv-gec.jpg

 

I think I pressed the "speed up" button 3 times, so that would be 300 rpm. I know things went better when I slowed down a bit, so it isn't wood-turning speed.

Link to comment
Share on other sites

Andy's lamp parts look fantastic! Although I am surprised that he hasn't progreammed up his little CNC lathe to spin them automatically?

 

I think the shape of the lamp parts have an advantage over Steve's task as they are are an expanding bell shape whithout any large change of contour. Steve has to spin his material through 90 degrees with quite a small radius and then spin a long parallel tube. This has always defeated me with my spinning attempts.

 

spin1.JPG

 

The brass part in the picture has a parallel section of only an inch and when I have tried for more the brass has torn or wrinkled up. As Andy said, this is a great sport for producing scrap.

 

I also have a feeling although I cannot be sure that the disk which you start with should be perfectly round. I have been cutting my disks just with a treadle guillotine so that they look like octagons (maybe 16 'o' gons ) rather than perfect circles. Can anyone confirm that this is important?

 

 

Barry.

Link to comment
Share on other sites

I shall do some spinning preparation tomorrow. In the mean time, I have been making track rod ball ends. Initially, I was hopeful that we could salvage the original ball ends but closer inspection revealed them to be pretty sick.

 

DSCN4788.JPG

 

The only solution was to make up some more. Fortunately, the originals were not hardened at all so it started off as a simple turning job in medium carbon steel. Dad did the donkey work, turning the shanks and screw cutting the 3/4" BSW threads.

 

DSCN1410.JPG

 

I then put them in the Myford and turned them roughly ball shaped.

 

DSCN4866.JPG

 

DSCN4867.JPG

 

DSCN4870.JPG

 

I now had the puzzle of generating a ball shape reasonably accurately. I did consider my spherical milling approach, previously seen in these pages but felt that a better approach might be to use a ball-turning attachment. I therefore acquired one from Arrand Engineering. It requires a boring head to be mounted on the end to carry the tool but I found that mine doesn't fit! Fortunately, I was able to borrow Father's, also made by Arrand.

 

DSCN4871.JPG

 

The boring head simply unscrews from the taper shank and then onto the turning attachment which is mounted in the toolpost.

 

DSCN4872.JPG

 

DSCN4873.JPG

 

DSCN4875.JPG

 

The tool is controlled by moving the lever in the foreground, gently and smoothly. I did have some trouble though as I had ground the tool with a standard knife edge. The turning attachment is meant for model engineers and balls of about 1/2" diameter so my 1 5/8" ones were stretching it to the limit. As a result, it was all flexing a little bit and the knife edge on the tool tended to drag it in to a deeper cut before springing out leaving a series of steps. I was at a loss to know what to do about this until I ran the tool backward with the knife edge trailing. It then gave a nice consistent smooth cut at a depth of 0.005". This was slow but quite satisfactory considering what I was expecting it to do.

 

DSCN4876.JPG

 

DSCN4877.JPG

 

I left 0.002" on for a final polish with emery and they came out well.

 

DSCN4878.JPG

 

DSCN4879.JPG

 

DSCN4882.JPG

 

Now I must ovehaul the female sections to match!

Link to comment
Share on other sites

The brass part in the picture has a parallel section of only an inch and when I have tried for more the brass has torn or wrinkled up.

 

I _think_ that there are two processes at work and you need to balance them.

 

You can lay the disc down on to the former. This keeps the material thickness the same, but creates wrinkles as the overall diameter reduces. This is what happens when the tool is relatively far from the former.

 

Alternatively, you can stretch the material along the former. This is what happens when the tool is hard against the former and you push towards the chuck. This is (I think) the process of shear-forming which looks a bit like spinning, but isn't.

 

You need to play these effects off against each other. It is interesting to note that the open ends of my headlights are rather thinner than the starting material, but the lampholder bosses have come out rather _thicker_ than the starting material.

Link to comment
Share on other sites

I also have a feeling although I cannot be sure that the disk which you start with should be perfectly round.

 

I guess it keeps the edge more homogenous, and so cracks and wrinkles are less sure where to start.

 

The spinning videos all seem to do a lot of edge trimming with a tool for the job, so it shouldn't be too hard to trim to perfect circles when mounted and "set on" the former.

Link to comment
Share on other sites

All in one go, though I did experiment with an extra annealing for the super-difficult lip.

 

Having said that, I would rather expect to have to anneal a brass part a few times if making your bearing cover.

 

At least Brass is fairly easy to judge the temperature of, it gets red before it melts.

 

I found that with aluminium a green marker pen worked well as a temperature gauge. Scribble all over it, then heat from the other side until the colour disappears.

Link to comment
Share on other sites

I know that this might sound like (and be) a completely dumb question, but is there any chance of spinning a curved end onto a tube instead of spinning a flat disc into a deep cup shape?

 

Yes, that could certainly be done although I have never tried it. It does depend on getting the right size tube to start with, though. I would have to have a few goes to judge the tube length as well. Another possibility.

 

Thanks!

Link to comment
Share on other sites

I have been preparing for the spinning exercise today. I had a rummage under the bench and came up with a splendid piece of oak which has been there for twenty years. It is hard as hell! This is good as when I have spun onto softer material, it has come out with a wood grain finish.

 

DSCN4883.JPG

 

This was faced off, drilled and then tapped 3/4" BSW to suit my back plate which I hold in the chuck.

 

DSCN4884.JPG

 

The next pice was the follower. This is a plate the diameter of the flat part of the cover with a central spigot to locate the disc. It is clamped up by using the revolving centre in the tailstock pushed into the centre on the reverse side.

 

DSCN4886.JPG

 

DSCN4885.JPG

 

Then it was time to cut out the blank. Our local second hand tool shop had a piece of brass in stock, big enough to make two, just in case I make a mess of the first one. It was roughed out with the nibbler and then filed all round to make a smooth edge. I think that this makes the edge a lot easier to finish and removes any stress concentrators reducing the chances of cracking starting around the edge.

 

DSCN4887.JPG

 

DSCN4889.JPG

 

That finished the spinning preparations. Further progress will have to wait until I can use Father's Colchester again. Finally today, I turned up the mounting adaptors to attach the cover to the top of the king pin and give a tapped hole for the stauffer.

 

DSCN4890.JPG

 

We are getting close to being able to hang the front wheels now, the next big milestone!

Link to comment
Share on other sites

I know that this might sound like (and be) a completely dumb question, but is there any chance of spinning a curved end onto a tube instead of spinning a flat disc into a deep cup shape?

 

They make gas cylinders that way. But I can see it being tricky to do it as a spinning operation as you are trying to compress the metal into a smaller volume.

 

 

Link to comment
Share on other sites

I found that with aluminium a green marker pen worked well as a temperature gauge. Scribble all over it, then heat from the other side until the colour disappears.

 

When I was at school I'm sure we were taught that you rubbed aluminium all over with soap then heat it up until the soap goes black, see here

http://steamshed.com/annealing%20process.html

Link to comment
Share on other sites

Thanks John. That one is excellent. It seems that the secret of getting the job off is to have a highly polished, metal mandrel, I am amazed at how far he spins it without annealing in between. I would have treated it at least half a dozen times. Not brave enough I guess!

 

The job will have to wait now until I am in Devon again to use the Colchester. It is a bit big and brutal for the poor old Myford!

 

Steve

Link to comment
Share on other sites

Thanks Steve. It sounds like I should be making a metal chuck/mandrel so that it doesn't get a grip. I hadn't thought of drilling the middle though. I will put a hole in the centre of my blank so that I can have a locating peg to prevent the unformed disc from flying out at speed. That might prove more excitement than I want!

 

Steve

was working once at this place.....all it were was O/D`ing and facing off some stainless blanks....

 

they`d come in straight off being parted off on a big oil country stanley...

 

then we`d swing em in a ward 7...

 

 

 

the razor sharp edges like sawblades at 1500 or so RPM...

 

 

 

they cut yer gloves to ribbons just mountin em.....lol...

Edited by flandersflyer
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...