TromboneChat

Here is a video of a piece of cross brace tube mounted in my lathe, with a dial indicator on the other end.

The tube is heated, and quickly expands by more than .015".

It takes several minutes to get back to room temp/original length.

The solder hardens well before the tube has cooled back down to its original length. This is why jigs can only get you so far in assembly.

Very interesting.

So, the challenge (and the magic) is to account for the expansion and to know at what point in the contraction that cooling will cause the solder to harden. Correct?

--Andy

Andy,
Yes. This is where heat control comes into play. Understanding where to heat, how much, and how long all influences how the assembly ends up.

That’s awesome Matthew. Thanks for sharing that!

To be honest with you. I would have never had the guts to do that experiment. My fear would be that the heat could mess up the caliper. I guess that is not a concern.

Makes sense. I would think that thermal expansion should be a big deal.

I have worked as a controls engineer in the past and dealt with industrial welding robots and never understood how often people seemed to just not care about how hot a part is during a welding operation - i.e., the difference between a weld being made after a part sat on a tool for hours vs. a weld being made in direct sequence from a bunch of previous welds. Or any semblance of climate control.

Yes. Every casting manufacturer has proprietary algorithms for shrinkage.

Good argument for JBWeld instead of solder. (PS that's intended as humor, don't actually try it.)

How does soldered on oversleeves not distort the slide tube?

Elow wrote: ↑Mon Sep 18, 2023 8:04 am How does soldered on oversleeves not distort the slide tube?

It does. Heat can also cause bent crooks to open up slightly when soldering ferrules, etc.

Heat also has an impact on your jigs and fixtures. If you're soldering up a bunch of the same assembly over a short time, the tooling can get quite hot and its dimension can change significantly.

My soldering experience has mostly been plumbing and electrical connection related. As far as welding, I have a welder which comes in handy down on the farm. Rule #1, when welding thin (sheet metal/auto body) material, low heat, and don’t weld too much at a time. Very easy to warp metal if you make too long of a weld.

An on a related topic, I have noticed when arriving to play in the winter, my horns are a bit sharp when I start playing, back in tune in about 5 minutes of playing.

BrassSection wrote: ↑Mon Sep 18, 2023 2:41 pm ...

An on a related topic, I have noticed when arriving to play in the winter, my horns are a bit sharp when I start playing, back in tune in about 5 minutes of playing.

This is related to the speed of sound. The speed of sound is related to temperature: the lower the temperature the slower sound travels. The pitch of the horn is the speed of sound divided by the length of tube (wavelength). While a cold horn is somewhat shorter than a warm one, the difference in length is much less than the effect of the speed of sound. So as you warm up the instrument, the speed of sound increases and the [fixed] tube length allows the pitch to increase.

BGuttman wrote: ↑Mon Sep 18, 2023 3:45 pm This is related to the speed of sound. The speed of sound is related to temperature: the lower the temperature the slower sound travels. The pitch of the horn is the speed of sound divided by the length of tube (wavelength). While a cold horn is somewhat shorter than a warm one, the difference in length is much less than the effect of the speed of sound. So as you warm up the instrument, the speed of sound increases and the [fixed] tube length allows the pitch to increase.

I'm pretty sure that the dominant factor affecting the pitch in this sense is not the length of the trombone, but the temperature of the wiggly air in it.

BrassSection wrote: ↑Mon Sep 18, 2023 2:41 pm

An on a related topic, I have noticed when arriving to play in the winter, my horns are a bit sharp when I start playing, back in tune in about 5 minutes of playing.

My horns are flat when cold and go sharp in the heat.

BGuttman wrote: ↑Mon Sep 18, 2023 5:45 pm
This is related to the speed of sound. The speed of sound is related to temperature: the lower the temperature the slower sound travels. The pitch of the horn is the speed of sound divided by the length of tube (wavelength). While a cold horn is somewhat shorter than a warm one, the difference in length is much less than the effect of the speed of sound. So as you warm up the instrument, the speed of sound increases and the [fixed] tube length allows the pitch to increase.

This reminds me of my former life as a Production Engineer at a pulp and paper mill. Huge lime kiln operating at 2300 F at the firing zone. Hard to keep ID fan running when kiln was cold on start-up, 300 HP 2300V motor would easily overload moving cold air, would run at about 40% load when kiln was hot. Never thought that kiln would be an object lesson in brass instruments!

I notice the change more drastically on my trumpet than any other horn.