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Old 10-27-2022, 03:39 PM
DrTrombone DrTrombone is offline
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Default Forming concave cones from sheet brass

Hi,

I'm a brass instrument hobbyist, and I do some fabrication. One style of horn I've been working on is the sackbut--a Renaissance trombone. These have a "kranz" or "garland" around the bell to add support. They look like this:



I've formed them by silver-brazing lamp banding into a circular shape, annealing, and then forming on a mandrel with a big rawhide mallet, but the result is always uneven and not very pretty.

I have one of those cheap "english-wheel-shaped objects."



Is there a technique I can use--either before or after silver-brazing the ends together--which will result in a prettier kranz?
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Old 10-27-2022, 04:16 PM
Jaroslav Jaroslav is offline
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I have seen several videos on YouTube of musical instrument repair. One video showed a special EW with many attachments for narrow openings. Everything is easy to make. I don't remember the address of the video anymore. I have similar extensions for different situations. My EWs are very variable. In some cases I use very small bearings and polyurethane and plastic wheels. They don't leave a mark.


Edit your EW a bit. Add some profile to make them less flexible. With flexible wheels, you don't have good control when shaping. Before welding the reinforcement, pre-tension the frame with a strap. The wheels become very strong. Your shaping result will be greatly improved.
https://www.allmetalshaping.com/showthread.php?t=20883
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Old 10-27-2022, 05:58 PM
hot rivet hot rivet is offline
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The best way i have seen them made is from flat sheet folded in half then raised over a mandrel. I have made similar shapes the same way, spinning would be another good option. There used to be a good video on youtube but i cannot find it.
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Old 10-28-2022, 11:41 AM
DavidB DavidB is offline
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While I've hand raised such forms from flat sheet rolled into a cone with the seam soldered I found spinning a better process. I've attached a couple of items I've spun in the past with the first being similar to the end bell which I think is what you're trying to improve.


spin1.jpg

spin2.jpg
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