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Hunslet 5" Loco

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Brian Brown 128/07/2009 18:22:55
1 forum posts
Hi all,
I'm currently approaching completion of my 1st locomotive, a 5" Hunslet to the Don Young design, but try as I may, I have not been able to form the brass cowling that wraps around the rear of the firebox backplate / outer wrapper joint. The cowl is a 2" wide brass strip in half round section and is curved through a 17 1/2 " diameter for 180 degrees, with the remaining legs on either side continuing half round but straight in order to cover the vertical joint.
I hope that makesense!
I've tried clamping sheet brass between 2 formers and heating/beating, but I still end up with creases. I've also tried forming a half round srtaight section and coaxing it around the radius, again to no avail. Pressing seems to be the answer, but I don't have the means or wherewithall to machine a set of dies.
I realise that the cowl is purely cosmetic, but as it adds immeasurably to the appearance, I would really appreciate some advice as to how approach this task before I ruin any more sheets of brass!
Many thanks,
Brian Brown
 
David Clark 128/07/2009 19:18:52
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3357 forum posts
112 photos
10 articles
Hi There
Could you turn the top bit, cut it in half, make the two uprights and
silver solder together?
regards david
 
Ian Abbott29/07/2009 11:50:25
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279 forum posts
21 photos
Is this a solid half round, or a shaped piece of metal like half a tube?
 
If it's the latter, how about starting with a 2" tube and having it bent at an auto exhaust  shop, then splitting it along the centre line.
 
A casting would work, but rather expensive.
 
Regards
Ian 
Speedy Builder526/02/2010 16:50:19
2878 forum posts
248 photos
Could you use copper instead - its a bit more malleable.
mgj26/02/2010 18:49:08
1017 forum posts
14 photos
Ian I suspect that may be a very good answer . Sounds like 1/2 a tube over some kind of flange or joint..
 
Otherwise its a former, a set of proper tin bashers hammers, and start shrinking and expanding. And keep annealing! Unless you have access to a proper (English) forming wheel. 
 
To do it round a former is quite simple (in concept!!!!) You need a contracting hammer. You anneal and start deforming the metal (with a soft face mallet is best). It will start to wrinkle - of course. Out comes the contracting hammer. Shrink the wrinkle, and take it out. And so you go on, annealing frequently as you go. You may find as the metal thickens in places you need to file some off.  Finally draw file and polish up.
 
Simples - until you try it. But that's how to panel beat it.
 
(A blunt file makes a reasonable contracting hammer, if you want to experiment on some scrap. Not as good as the real thing, but adequate. Bit slow, but it will take the wrinkles out.
 
 

Edited By meyrick griffith-jones on 26/02/2010 18:49:33

calder percival 104/03/2010 19:48:56
19 forum posts
1 photos
the secret is to take it all together steady  and re heat don't go bashing in one area. heat, beat ,trim, heat it will work just do it slowly
calder percival 104/03/2010 19:49:01
19 forum posts
1 photos
the secret is to take it all together steady  and re heat don't go bashing in one area. heat, beat ,trim, heat it will work just do it slowly

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