Bending tubes

A forum to discuss the arcane art of making uilleann pipes, reeds, and set maintenance.

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dirk the piper
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Bending tubes

Post by dirk the piper » Tue Feb 28, 2006 12:45 pm

In the "Books" topic we got on a pretty interesting tangent about tube bending... Let's give it its own topic. Also, be sure to check out page 2 of "Good Books."

It seems a lot of pipe-makers have a lot of trouble with bending tubes well. Also, has anyone on this list ever seen a tube bend on uilleann pipes that is as smooth and even as say, the crook on a nicely-made trumpet? If you have seen one specimen that good, I bet you also have seen ten that are nowhere near that quality. Anyway, let's see if we can uncover some good methods here.

My tube bender is a home-made bender. I got the basic design by looking at Tim Britton's bender at his shop, and then I built my own, using scrap metal and blackwood. When I get home, I'll post some pictures. I intend to keep focussing on improving my tube bends.

So far, I only have some experience bending brass, using a woods metal filler. I have made dies for bending the bass-drone end-return on a D-set, and the loop bends for the same drone. It also works fine for bending the air tube on a chanter cap. When I was shopping for bismuth-alloy filler, some supplier sent me a nice pamphlet on how to get the best results with the alloy. There's more to it than meets the eye.

Regarding leverage, I use a four-foot long piece of steel as the lever on my home-made bender. The advantage of this is that the big, fairly smooth motion by my hand on the outside of the lever translates into a very smooth, easy bending motion at the tube. As you mention, Billh, the bend is usually at an instantaneous point, all done at once. It's pretty easy to make a very even bend, and there's no elbow-grease needed. Sometimes, the bend isn't perfectly symmetric, but sometimes it is. I think, maybe the brass tube slips in the jig when I don't get a symmetric bend. I also think a two-lever bender design might give more consistent results. I also think it would be fun to build a hydraulic bender, or experiment with even longer lever-arms.

Dirk
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John Mulhern
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Post by John Mulhern » Wed Mar 01, 2006 8:55 am

I posted this topic over on the Practical Machinist forum.
http://www.practicalmachinist.com/ubb/u ... 4;t=000831

(interesting technical .pdf suggested by contributor...flexing ball mandrel p. 11. Probably prohibitively expensive, impossible to find & a PITA to make...but hmmmmmm? ) :mrgreen:
http://www.hinesbending.com/BASICTUBEBENDINGGUIDE.pdf

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dirk the piper
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Post by dirk the piper » Wed Mar 01, 2006 12:27 pm

The Ferree's intrument catalog sells strings of steel balls, but they are inteneded for removing dents from the bent tubes of various wind instruments.

-Dirk
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PJ
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Post by PJ » Wed Mar 01, 2006 1:25 pm

Don't know if anyone's already posted this but here's a link to Mike Dow's website. Scroll down to the end of the page and he give some information on bending brass tubing:

http://www.archcarving.com/Bagpipes%20& ... m#Projects
PJ

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Post by billh » Thu Mar 02, 2006 9:00 am

John Mulhern wrote:...
(interesting technical .pdf suggested by contributor...flexing ball mandrel p. 11. Probably prohibitively expensive, impossible to find & a PITA to make...but hmmmmmm? ) :mrgreen:
http://www.hinesbending.com/BASICTUBEBENDINGGUIDE.pdf
ZOWIE, that's great!

I also suspect that the jig in figure 17 could be used without the mandrel (using a metal filler instead, like lead or Woods' metal) to good effect for our purposes. I think one often wants a radius somewhat less than twice the tube diameter, but never below 1.5D, and our tubing needs to have reasonably thick walls to survive dents and bumps. Just making a nice jig with pressure die, bending die, and wiper die, ought to do the trick. My current setup has most of the component parts, but the tolerances are not really as high as one would like.

Bill

Kevin Popejoy
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Post by Kevin Popejoy » Mon Mar 06, 2006 11:31 am

I fabricated my tube bending jig using readily available materials. Mr. Quinn was kind enough to give me some guidance. The design is relatively simple using a central wooden capstan and two bending arms. The capstan and blocks are easily changed out for different sized tubing. I use lead as a filler and anneal the tube prior to bending. I also polish the tube on the lathe before I bend it to cut down on finishing time. Just click on the thumbnail for a larger pic.

Component parts:

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Jig set up with tube in place:

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Partial bend:

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Full bend:

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You may not see in the photos that the bearing blocks have a brass back. The threaded bolt through the arm bears against the back of the block and allows for adjustment. As you can see from the component pic, I have a couple sets of capstans and blocks for different tube sizes and bending radius'. Hope this helps.

Kevin

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dirk the piper
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Post by dirk the piper » Mon Mar 06, 2006 12:49 pm

Those pictures are really great, Kevin! Do you have some shots of the tube by itself after the bending is done? I'm also glad to hear from people using the two-lever approach.
When you bend, is it hard to keep the two levers steady and even with each other, or is it a fairly simple thing?

-Dirk
Last edited by dirk the piper on Mon Mar 06, 2006 3:02 pm, edited 1 time in total.
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billh
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Post by billh » Mon Mar 06, 2006 1:38 pm

Thanks Kevin; nice setup and great pics.

It's very similar in concept and design to what I use, except mine has much shorter lever arms and isn't as neat, generally. I think yours'll inspire me to do a re-make. :-)

Bill

Kevin Popejoy
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Post by Kevin Popejoy » Mon Mar 06, 2006 2:15 pm

Sorry Dirk, I didn't think to take a shot of a completed tube...although I have a couple pics of a finished set. Again, just click on the thumbnail for a bigger pic:

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Bending is pretty simple...just load the tube, adjust the blocks down onto the tubing using the threaded bolts and go for it. With the broad bearing surfaces everything stays aligned. The only real tricks are annealing the tube and filling it with lead. Skip either step and you'll get wrinkles.

And Bill, thanks I'm glad you like it. It's really more robust than it needs to be but the design was somewhat guided by the materials I had on hand. Have fun with it. k

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dirk the piper
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Post by dirk the piper » Tue Mar 07, 2006 10:20 am

Nice pics Kevin! I'm really looking forward to building a two-arm bender now.
As far as I'm concerned, a more robust tube bender makes it easier to make a better tube bend. :-)

-Dirk
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DMQuinn
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Post by DMQuinn » Wed Mar 08, 2006 9:03 am

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dirk the piper
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Post by dirk the piper » Wed Mar 08, 2006 11:49 am

Now that's beauty! Thank you for posting those, David. Are you using a two-arm bender design?

Also, I like how your bass-drone bends end in a cup that covers the ouside of the wood, which would prevent the problem of wood cracks from metal tubes inserted into wood.

-Dirk
I'm a piper, you're a piper, he's a piper, she's a piper - wouldn't you like to be a piper too?

Jonathan_P
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Post by Jonathan_P » Wed Mar 08, 2006 12:28 pm

Lovely photos, David.

I'm curious about the removable clamps you use to stabilize your bass drone loop. I have asked a couple of folks who own your pipes, and they didn't know why you build them this way.

Do you do this so that the loop can be reversed if desired? Or is there some other reason?
Jonathan

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DMQuinn
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Post by DMQuinn » Wed Mar 08, 2006 7:39 pm

dirk the piper wrote:Now that's beauty! Thank you for posting those, David. Are you using a two-arm bender design?

Also, I like how your bass-drone bends end in a cup that covers the ouside of the wood, which would prevent the problem of wood cracks from metal tubes inserted into wood.

-Dirk
The bending device is very much like the one Kevin showed us pictures of. Two arms rotate around an axle post (a 1/2" bolt) held in a vise, and capstans of various size and radius can be put onto the axle. Bolts through the arms allow for positioning the wooden cauls which distribute the bending forces. I always bend from the center, i.e. both arms at once, all in one go to the target radius.

The cups, which I call "thimbles," fit over tenons lapped with thread, and I do it that way for exactly the reason you mention, to avoid putting metal inside wood. The drawback of the old method of sticking the ends of the bends into sockets in the wood is of course that it often splits the walls of the sockets. Not always, but once is too often if it's your drone. The thimble approach is safer, but it also requires maintenance, like any other lapped joint.

Jonathan_P wrote:Lovely photos, David.

I'm curious about the removable clamps you use to stabilize your bass drone loop. I have asked a couple of folks who own your pipes, and they didn't know why you build them this way.

Do you do this so that the loop can be reversed if desired? Or is there some other reason?
The traditional approach is to make the first and third legs of the bass drone taper somewhat, so a simple non-adjusting band will hold them together by wedging. There is only a very small degree of compensation possible with that arrangement, and each time you take the drone apart, more marring is possible. The clamps only make it possible to take the drone apart and put it back together without marring the wooden pieces all that much, but as with so many "innovations," it's probably not worth it. The old way works just fine, and the adjustable clamps are a whole lot more work.

The loop can be reversed, but that hardly ever comes up. I should think that if you used the old method of cementing the ends of the U-bends into sockets, that would pretty much commit you to a right-handed or left-handed setup. Using the thimbles commits you to seasonal maintenance, so ease of field stripping becomes an issue.

Kevin Popejoy
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Post by Kevin Popejoy » Thu Mar 09, 2006 12:05 pm

DMQuinn wrote:I should think that if you used the old method of cementing the ends of the U-bends into sockets, that would pretty much commit you to a right-handed or left-handed setup. Using the thimbles commits you to seasonal maintenance, so ease of field stripping becomes an issue.
Or you could epoxy the thimbles in place giving you the benefits of the thimble without the seasonal maintainence. You wouldn't be able to switch the set-up... but how often does that come up? k

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