[modeleng] Brass dome cover for Tinkerbell
- From: Harry Wade <hww@xxxxxxxx>
- To: modeleng@xxxxxxxxxxxxx
- Date: Tue, 08 Nov 2005 10:04:40 -0600
At 07:52 AM 11/8/05 +0000, you wrote:
> I am seriously considering making a brass dome cover for a 7.25" gauge
>tinkerbell that I help maintain. The cover is 10" diameter, 12" high, boiler
>is 14" diameter, and it has a 4" hole in the top for the safety valves to
>exit through.
Peter,
If I had this job to do I would look first to Option #2, spinning the
hemisphere and beat out the base flare and I would start with a drawn tube
if possible. But then I suppose 10"OD drawn brass tube would be no easier
to find in the UK than it is in the US, although we can occasionally find
it at better metal merchants by asking for Unobtainium.
Joking aside I think it would be beneficial to use solid material,
either sheet or tube, because the difference in ductility and behavior
between brass parent metal and silver solder may very well cause problems
when you begin stretching the metal at the flange. I don't know this for a
fact but my sense of the behaviors of both metals tells me this is a
possibility.
I have done a couple of base flares such as this dome will have (in
copper, for boiler steam domes) and it's not all that difficult although
the more care given to the formers the better the results. I began with a
piece of drawn tube and (as you can envision) a female form which tightly
fits the tube OD. The required flange radius is cut perpindiculary across
one face of the form on the tube centerline. A tightly fitting bung needs
to be made and inserted into the tube ID to prevent the walls rolling
inward as the flange is laid over. As Barry says, anneal regularly.
Regards,
Harry Wade
Nashville Tennessee
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