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Making several subtle bends on brass tubing


joelwideqvist
12-29-2014, 07:06 AM
Hi guys,
I'm in the process of making two exhaust pipes for a 1/12 chopper build. I want to make them out of brass tubing but I'm having a hard time getting it right. I have some tube bending tools but my primary issue is that I need to do some subtle bends right next to eachother and the bends has to be exactly at the right spot to route around the engine. The final pipe is just like 30 mm "wide" and moves in all dimensions.

We are talking about something like this;

http://www.furyforums.com/forum/attachments/honda-fury-general-discussion/448d1249015364-raw-design-new-exhaust-pict0006.jpg

or this;

http://i1013.photobucket.com/albums/af254/paulhart1970/928d99dc.jpg

How would you go about the task? Do you find it possible to achieve in brass tubing or is it just too fiddly? Pliers, some sort of jig or just skip the brass and go for styrene rod or sprue?? (The brass material would suit the build best but will be left out if to hard to work with)

/Joel

mike@af
12-29-2014, 10:12 AM
I'd build it the way it would be built in 1:1, make a the various bends out of separate pieces, cut, and solder together.

CrateCruncher
12-29-2014, 11:54 AM
High Joel,
I've had best success using solid aluminum rod from K&S kiosk in many hobby stores in the States. Because it's solid it doesn't collapse or flatten when bending around a mandrel. Since it's aluminum it doesn't have to be plated. Just polish it and shoot a bit of clear to protect the finish.

The hard part is getting the tips correct. I drill out the end of the rod before bending. Start with a small bit and work your way up. Don't go too big or too large a step or the aluminum will stretch and start to bulge. To simulate an extremely thin wall thickness I "scrape" the inside of the soft aluminum wall with a sharp hobby knife until it looks right.

Order of operations is important. I wouldn't bend anything until after the tip is drilled. After the bends are made I then use a flat file to taper the tip to the correct angle. Go back and use the scraping technique to even out the wall thickness. Again, go slow and use a SHARP blade! The aluminum cuts like butter.

The demarcations shown in your photo can easily be made by rolling the soft aluminum rod under a hobby blade at the appropriate intervals prior to bending.

Good luck!
http://i419.photobucket.com/albums/pp280/cratecruncher/Custom%20Katana/swbfrt004.jpg

360spider
12-29-2014, 12:46 PM
I would also suggest putting a wire of the same diameter inside the tubing to prevent it from kinking in the spots where bends need to be. Make it shorter than the pipe so it doesn't stick out when you done.

stevenoble
12-29-2014, 05:50 PM
I've had success by filling the rods with sand whilst you bend it to shape to stop it collapsing..

joelwideqvist
12-30-2014, 12:54 AM
Thanks for your input guys, very valuable, but it's not really stopping the tube from collapsing that is my problem. Mor like I dont have the power to bend the tube when it has to be done with bends that are so tight together. Is it a question of the hardness of the material that can be easily solved by using pliers or is it hard to come by with brass?

CrateCruncher
12-30-2014, 01:24 AM
I'm curious. Why do you want brass? It's much harder to work than aluminum and has to be polished and plated. The annealed aluminum rod from K&S is soft enough to pull around a drill bit with your thumb.

RC airplane guys use brass tube in their fuel plumbing. Dubro makes a small inexpensive bender for 1/8 and 5/32" diameters I believe. Here is a video review: https://www.youtube.com/watch?v=e-H1DUh1xPc

joelwideqvist
12-30-2014, 04:07 AM
I'm curious. Why do you want brass? It's much harder to work than aluminum and has to be polished and plated. The annealed aluminum rod from K&S is soft enough to pull around a drill bit with your thumb.

RC airplane guys use brass tube in their fuel plumbing. Dubro makes a small inexpensive bender for 1/8 and 5/32" diameters I believe. Here is a video review: https://www.youtube.com/watch?v=e-H1DUh1xPc

Mostly cause it is what I have at hand and cause it makes me irritated that I can't fix it :-) I'll try to get hold of some other tubes and rods and see where that leads.

MPWR
12-30-2014, 08:59 PM
A technique that I've heard works (but I've not yet used is):

First, anneal the tubing by hearing it with fire until glowing, then let cool. It dramaticly softens the brass, and makes it more flexible/bendable. (Ok, this I have done, and do often when working with brass.)

Once annealed, seal one end with modeling clay, fill with water, and seal the other end with clay. Stick it in a freezer until the water is frozen solid. Then bend as you like.

From what I've heard, this is how brass musical instruments are bent into ellaborate shapes, and it works with small tubing as well.

sjelic
12-31-2014, 02:29 AM
or cut the tube where inner bent will be (not only cut but triangle kind of cut depending on the size of a bent), then solder the cut, I was doing that on 90 degrees bents and it went fine, when you cut it to the half of a pipe it will easily bent. Water freezing tehnique will also remove smaller damage on the bent.

joelwideqvist
12-31-2014, 02:38 AM
I don't have soldering skills so, although interesting, I think I'll skip that one.

Perhaps just of academic interest, but what has to be used to make brass glow and anneal? I guess a candle will not be enough, a small burner perhaps?

joelwideqvist
12-31-2014, 02:39 AM
But all in all I think I'll just go for another material.

CFarias
12-31-2014, 09:50 PM
Perhaps just of academic interest, but what has to be used to make brass glow and anneal? I guess a candle will not be enough, a small burner perhaps? Use a butane torch. I would recommend the kind use for cooking, but a plumber's torch will work as well. Be sure you have a surface to let it cool on, such as a large piece of tile. You don't want to burn your fingers holding on to the piece while it cools. Have you considered using large diameter solder for the pipes? It bends easily and can be plated. Finally, using solid rod instead of tubing will give you more surface for soldering and will hold its shape better during bending. For open ended pipe finish off that length with a proper tube. Large diameter stainless steel hypodermic tubing can be found on-line (Component Supply Co.) and can give you a better scale wall thickness and appearance than brass or aluminum tubing. It's more difficult to work with but can be bent and soldered as suggested by other forum members and can be polished to a beautiful shine. Hope this helps.

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