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WW1 Thornycroft restoration

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Steve

 

What sort of diameter is it?

 

The boiler on a Bowman Jenkins E101 or M101 is supposedley 'drawn'

 

269_1.jpg

 

its the workhardening though that takes place whilst spinning/coldforming...

 

often copious amounts of annealing are required to achieve the form without introducing hard spots, spelching or stress cracks....

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Rollforming sounds interesting. How would that work? I think of it as a progressive folding process for producing long, two dimensional sections such as gutters and haven't seen it produce cylindrical items. I'll try anything which gives me the results I want!

 

Yes, annealing is essential and if anything, I do it too much. In the clip above (Thanks Chopa!) the spinner carries out a tremendous amount of forming in one hit whereas I tend to remove the part, re-anneal it and then put it back for another go. My concern about getting the piece off the mandrel is that I want to remove it, anneal it and put it back a number of times. The difficulty is that it is parallel and has to slide the whole way along the mandrel. The split mandrel in the clip above is tapered two ways so once loosened, the part comes off. I could make the mandrel out of aluminium which would prevent the brass from getting a grip but I don't want to go to that much trouble. A nice piece of oak or mahogany will do the job well, as long as I can get the thing off! Waxing the block and then gently warming the brass sounds like quite a nice approach.

 

Incidentally, what is 'Spelching'. I've not heard that one before and my dictionary isn't being very helpful either!

 

Cheers!

 

Steve

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Steve

 

What sort of diameter is it?

 

The boiler on a Bowman Jenkins E101 or M101 is supposedley 'drawn'

 

Hi Hedd.

 

It is 3 3/16" dia by 3 3/16" long and 16swg. It is going to take some pushing around which is very unkind to lathes!

 

Steve

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probably pie in the sky but how about a couple of formers and your mates press as per this clip

though I would think in 1/16th brass I would think the home press you have would do it Edited by cosrec

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It appears to be a deep drawing like a cartridge case. I will have to spin it, however. It is about 4" tall and parallel so getting it off the hardwood chuck will be tricky. Any suggestions would be welcome!

 

Steve

 

Steve, I make patterns about that size for both brass and steel sheet out of aluminum. The way to keep it from bell mouthing at the end is to drill a 1/4" hole front to back to allow the air to escape while spinning the part. Then it will be parallel and you can get it of the tool. Hope it helps you out as it works for us. Great job on your restorations as I am always learning something from these threads.

 

Steve K.

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probably pie in the sky but how about a couple of formers and your mates press as per this clip
though I would think in 1/16th brass I would think the home press you have would do it

 

Deep drawing would work. The challenge for me is to make the part with a minimum of tooling as I only want one! Worth keeping up my sleeve. Thanks for the fascinating clip!

 

Steve

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Steve, I make patterns about that size for both brass and steel sheet out of aluminum. The way to keep it from bell mouthing at the end is to drill a 1/4" hole front to back to allow the air to escape while spinning the part. Then it will be parallel and you can get it of the tool. Hope it helps you out as it works for us. Great job on your restorations as I am always learning something from these threads.

 

Steve K.

 

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

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probably pie in the sky but how about a couple of formers and your mates press as per this clip
though I would think in 1/16th brass I would think the home press you have would do it

 

Watching this video it is interesting to see how much the finished cylinder wall thickness is reduced from the original plate thickness in the drawing process. Compare the plate at 0.32 and the cylinder, after cutting, at 2.11. I estimate nearly half the thickness has gone.

 

The Stanley Brothers in America built their steam car boilers by drawing. The boiler was 18" in diameter by 13" high and the plate started at 1/2" thick. After drawing the wall thickness was about 3/16" and the brothers thought this too thin a safely margin to use with the 600psi that these cars worked at. In order to satisfy their concern they wound three wraps of carbon steel wire around the boiler and welded the ends to the shell. In a test the unwound boiler exploded at 1,200psi but the wire wound boiler withstood 1,800psi at which point the expanded and ferruled copper tube ends started to leak.

 

John

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That is still only a factor of three! Full size locomotive boilers are designed with a factor of five and our models run at eight!

 

Fascinating clip though.

 

Steve

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Rollforming sounds interesting. How would that work? I think of it as a progressive folding process for producing long, two dimensional sections such as gutters and haven't seen it produce cylindrical items. I'll try anything which gives me the results I want!

 

Yes, annealing is essential and if anything, I do it too much. In the clip above (Thanks Chopa!) the spinner carries out a tremendous amount of forming in one hit whereas I tend to remove the part, re-anneal it and then put it back for another go. My concern about getting the piece off the mandrel is that I want to remove it, anneal it and put it back a number of times. The difficulty is that it is parallel and has to slide the whole way along the mandrel. The split mandrel in the clip above is tapered two ways so once loosened, the part comes off. I could make the mandrel out of aluminium which would prevent the brass from getting a grip but I don't want to go to that much trouble. A nice piece of oak or mahogany will do the job well, as long as I can get the thing off! Waxing the block and then gently warming the brass sounds like quite a nice approach.

 

Incidentally, what is 'Spelching'. I've not heard that one before and my dictionary isn't being very helpful either!

 

Cheers!

 

Steve

 

where it breaks out & splits/frets...

 

its a common term used in joinery ...as in:

 

"spelch block"....used to support the back edge of anything put through..lets say a spindle moulder...

 

you would clamp the piece/s and use a spelch block on the back edge when moulding/scribing/relishing....prevents breakout when machining against the grain

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Steve, I make patterns about that size for both brass and steel sheet out of aluminum. The way to keep it from bell mouthing at the end is to drill a 1/4" hole front to back to allow the air to escape while spinning the part. Then it will be parallel and you can get it of the tool. Hope it helps you out as it works for us. Great job on your restorations as I am always learning something from these threads.

 

Steve K.

 

 

just out of interest here as well....

 

when turning/backing off large, thin O/D discs on a lathe....start from the centre out....otherwise it wont face up flat...

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Hi Hedd.

 

It is 3 3/16" dia by 3 3/16" long and 16swg. It is going to take some pushing around which is very unkind to lathes!

 

Steve

 

 

Why?

 

you have bearings to take both radial & axial/linear thrust on a lathe dont you....

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Rollforming sounds interesting. How would that work? I think of it as a progressive folding process for producing long, two dimensional sections such as gutters and haven't seen it produce cylindrical items. I'll try anything which gives me the results I want!

 

Yes, annealing is essential and if anything, I do it too much. In the clip above (Thanks Chopa!) the spinner carries out a tremendous amount of forming in one hit whereas I tend to remove the part, re-anneal it and then put it back for another go. My concern about getting the piece off the mandrel is that I want to remove it, anneal it and put it back a number of times. The difficulty is that it is parallel and has to slide the whole way along the mandrel. The split mandrel in the clip above is tapered two ways so once loosened, the part comes off. I could make the mandrel out of aluminium which would prevent the brass from getting a grip but I don't want to go to that much trouble. A nice piece of oak or mahogany will do the job well, as long as I can get the thing off! Waxing the block and then gently warming the brass sounds like quite a nice approach.

 

Incidentally, what is 'Spelching'. I've not heard that one before and my dictionary isn't being very helpful either!

 

Cheers!

 

Steve

get yourself some of that oak Steve and make up 2 blocks....tapered....

 

find a way of fixing the 2 blocks together with the tapers facing each other....then swing them and get an O/D for size...

 

should make extracting the spun form easier....if you use a bit of allthread epoxied into one of the oak blocks....you can then use a nut to hold the other one to it....get the nut chuckside....then you just back the nut off....and the form should release...thus allowing extraction of the spun part....:)

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You might be overthinking this one. I believe you will be able to extract the mandrel with a few taps, especially if you beeswax it up first.

If it proves impossible even after a little gentle heating for expansion, you can always drill the crown, it needs a hole to bolt onto the kingpin top anyway, tap it for air or grease fitting, epoxy up the air hole in your mandrel, then blow it out with a grease gun or airline.

Edited by Chopa

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You might be overthinking this one. I believe you will be able to extract the mandrel with a few taps, especially if you beeswax it up first.

If it proves impossible even after a little gentle heating for expansion, you can always drill the crown, it needs a hole to bolt onto the kingpin top anyway, tap it for air or grease fitting, epoxy up the air hole in your mandrel, then blow it out with a grease gun or airline.

 

For just one-off, I will start with this approach. It is nice to know, however, that there are a few more strings to my bow if need be!

 

Many thanks!

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We did do a little more over the weekend. First thing was to fit the governor casting (without butterfly!).

 

DSCN1533.JPG

 

Of course, it needs some linkage. I had a rummage around and found some ball joints that we had bought years ago. They were just right!

 

DSCN1535.JPG

 

A quick clean up and a rod and the effect is complete.

 

DSCN1536.JPG

 

Finally, we made up the starting dog and fitted it to the end of the crank.

 

DSCN1541.JPG

 

A couple more bits done. Must press on with the front axle now as we really want to get it on its wheels.

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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

 

Hi Steve, We put a pin on the center unless we need you have a cup without a hole. Then we drill a hole midway between the pin and edge to bleed the air from the part while spinning it. The part comes out nice and parallel with no bell mouth opening. We have made hundreds of spin tools that way in both aluminum and steel depending on how many pieces we run. So far the aluminum tool have produced hundreds of parts but the get soft eventually due to the heat created by spinning. Hope I helped out on this as you and your crew have given me idea also.

 

Steve K.

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Thanks Steve. You certainly have helped me out. My spinning has come about by buying a book, making some tools and having a go. I have never been able to speak with anyone who actually knows what they are talking about on the subject!

 

I always put a hole in the centre if I can so that I can have a locating pin as I am concerned about the disc flying out at the start of the job. Incidentally, please may I have some guidance on speeds? This one will be brass, 16swg and the initial diameter of the disc will be 8". My book says 'fast' but I don't know what that really means. I feel inclined to try about 400rpm but I would value some guidance please.

 

Cheers!

 

Steve

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We did do a little more over the weekend. First thing was to fit the governor casting (without butterfly!).

 

[ATTACH=CONFIG]101030[/ATTACH]

 

Of course, it needs some linkage. I had a rummage around and found some ball joints that we had bought years ago. They were just right!

 

[ATTACH=CONFIG]101031[/ATTACH]

 

A quick clean up and a rod and the effect is complete.

 

[ATTACH=CONFIG]101032[/ATTACH]

 

Finally, we made up the starting dog and fitted it to the end of the crank.

 

[ATTACH=CONFIG]101033[/ATTACH]

 

A couple more bits done. Must press on with the front axle now as we really want to get it on its wheels.

 

Yep, got the message Steve. ;)

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If it proves impossible even after a little gentle heating for expansion, you can always drill the crown, it needs a hole to bolt onto the kingpin top anyway, tap it for air or grease fitting, epoxy up the air hole in your mandrel, then blow it out with a grease gun or airline.

 

I am glad I read this far before replying, I was about to suggest the same thing.

 

Air will slightly expand the part and provide a nice air-bearing effect. But grease might be less exciting.

 

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

https://picasaweb.google.com/lh/photo/LBoi5b4CsBt_EFhiK0EPftMTjNZETYmyPJy0liipFm0?feat=directlink

 

But also some usable parts:

https://picasaweb.google.com/lh/photo/JqMiezKZO-Cwmt1JMMShgdMTjNZETYmyPJy0liipFm0?feat=directlink

 

(The Ner-a-Car has one acetylene light and one new-fangled electric one)

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