I spend a lot of time with band instruments. I need to measure the inside
taper of a curved pipe without (BIG WITHOUT) destroying it. Measuring on
the outside and then subtracting wall thickness really doesn't work because
the pipes are drawn and the wall thickness varies.

I was thinking that there should be some plastic like what fishing bait is
made from or the material that is used to make flexible molds that I should
be able to pour in there and then pull out after it gets floppy.

Any ideas what plastics to look at?

Any ideas how to measure the ID of curved tapered pipes?

Regards,
LB

Sounds like you need one of those ultasonic units to test wall thickness.

Leonard & Peggy Brown wrote:

I spend a lot of time with band instruments. I need to measure the inside
taper of a curved pipe without (BIG WITHOUT) destroying it. Measuring on
the outside and then subtracting wall thickness really doesn't work because
the pipes are drawn and the wall thickness varies.

I was thinking that there should be some plastic like what fishing bait is
made from or the material that is used to make flexible molds that I should
be able to pour in there and then pull out after it gets floppy.

Any ideas what plastics to look at?

Any ideas how to measure the ID of curved tapered pipes?

Regards,
LB

On Thu, 17 Feb 2005 00:42:23 GMT, "Leonard & Peggy Brown"
wrote:

I was thinking that there should be some plastic like what fishing bait is
made from or the material that is used to make flexible molds that I should
be able to pour in there and then pull out after it gets floppy.

Any ideas what plastics to look at?

Any ideas how to measure the ID of curved tapered pipes?

Regards,
LB

Maybe you could ask a dentist about the stuff they use to create
moulds for crowns/dentures.

Hi, not knowing how much of a curve you are talking about this may not
work, but if not too sharp, simple gelatine can be cast and literally blown
out of the tube. We use agar in the lab and fairly high % stuff can be
pretty stiff but still flexible. Gelatine is likely about the same. With
some care, even if it breaks a little, you might be able to get some
measurement.
Again, not knowing how sharp a turn and how precise you need to be, this may
not work.

"Leonard & Peggy Brown" wrote in message
...
| I spend a lot of time with band instruments. I need to measure the inside
| taper of a curved pipe without (BIG WITHOUT) destroying it. Measuring on
| the outside and then subtracting wall thickness really doesn't work
because
| the pipes are drawn and the wall thickness varies.
|
| I was thinking that there should be some plastic like what fishing bait is
| made from or the material that is used to make flexible molds that I
should
| be able to pour in there and then pull out after it gets floppy.
|
| Any ideas what plastics to look at?
|
| Any ideas how to measure the ID of curved tapered pipes?
|
| Regards,
| LB

Reprorubber. The first hit on the web is this:
http://www.newmantools.com/flexbar/repl.htm We use the blue stuff a lot at
work. We usually make a bit extra and if you keep rolling it between your
hands while it cures you get a perfect ball that bounces like a superball.

"Leonard & Peggy Brown" wrote in message
...
I spend a lot of time with band instruments. I need to measure the inside
taper of a curved pipe without (BIG WITHOUT) destroying it. Measuring on
the outside and then subtracting wall thickness really doesn't work
because
the pipes are drawn and the wall thickness varies.


This is interesting. What for?

On Thu, 17 Feb 2005 00:42:23 GMT, "Leonard & Peggy Brown"
wrote:

I spend a lot of time with band instruments. I need to measure the inside
taper of a curved pipe without (BIG WITHOUT) destroying it. Measuring on
the outside and then subtracting wall thickness really doesn't work because
the pipes are drawn and the wall thickness varies.

I was thinking that there should be some plastic like what fishing bait is
made from or the material that is used to make flexible molds that I should
be able to pour in there and then pull out after it gets floppy.

Any ideas what plastics to look at?

Any ideas how to measure the ID of curved tapered pipes?

Regards,
LB

I've used this stuff called "Alumalite". It's a silicone rubber that's
made for making molds. It's available at hobby stores. Also, here's a
url for someone selling molding supplies who will give you a free
sample. http://www.jgreer.com/silicone%20page.htm . Alumilite is
expensive. I don't have any experience with the fellow at the above
url or with his prices. Silicone rubber is nice because it doesn't
stick to the item being copied. There is also a metrology rubber
called "Repro Rubber". It's good stuff but really expensive.
ERS

"jtaylor" wrote in message
...

"Leonard & Peggy Brown" wrote in message
...
I spend a lot of time with band instruments. I need to measure the
inside
taper of a curved pipe without (BIG WITHOUT) destroying it. Measuring
on
the outside and then subtracting wall thickness really doesn't work
because
the pipes are drawn and the wall thickness varies.


This is interesting. What for?


I need to measure some of the tapers on an old french horn so that it can be
reproduced.
LB

LB

If that horn is old enough, you may be talking hand hammered, rolled,
and soldered tubes, so wall thickness is variable depending on which way
you measure. You should post to the Musical Instrument Makers Forum,
www.mimf.com . There are a bunch of clever people there, some of whom
make brass winds.

You might also look at Robert Barclay's book, "The Art of the
Trumpet-Maker" which is about making replica 17th and 18th century
Nuremberg style trumpets, but covers a lot of the same processes as were
used making horns.

My guess is once you get out of the bell region down into the tubing
part, the wall thickness will be pretty uniform. I'd do a bunch of
measurements with a long arm caliper at every point you can reach, at
several points around the circumference of each tube you can reach into,
and see if there is a statistically significant variation. You may not
need to make a cast replica (which is always dicey because minor
registration errors will cause huge wall thickness errors).

In point of fact, wall thickness, except in the bell, is insignificant
to the sound of the horn. Even the shape of the air column is
immaterial, which is why you can fold them up and have elliptical
sections near the valves and at the sharp curves. Only the volume counts.

Interesting problem.

Good luck

Jim

I would try silicone rubber potting from your local building supply
with some hollow glass microspheres added for filler. How much
microspheres to add would take a little experimentation. Too much and
the result is not flexable enough to get it out in one piece. Too
little and it would be too flexable to get good measurements.


Dan