Garden Railway Forum

I have purchased a kit containing a small quantity of 3mm copper pipe.
I understand how to bend larger plumbing pipe by filling with sand etc, but how do I prevent kinking with the smaller diameter.
^Thanks for any words of help.

hoppy504 wrote: ↑Wed Aug 31, 2022 12:39 pm I understand how to bend larger plumbing pipe by filling with sand etc, but how do I prevent kinking with the smaller diameter.

What radius do you want the bend in the tube to be?

For 1/8" copper tube, say for steam piping on a live steam loco, I normally just make sure the tube is fully annealed and bend it by hand. I can successfully bend a radius around 1/2" that way, by taking it slow and using multiple anneals.

For smaller radii, if you have a lathe there are model engineering designs around for tubing benders. I built a simple bending mandrel for 1/8" tube, but can't find it to take a photo., which shows how often I use it.

Don't know how easy it would be pouring sand into 3mm tubing, but it may be possible to use the bending technique that makers of brass musical instruments use. Fill the tube with water, plug the ends and freeze the water. Bend it, let it thaw and pour out the water.

Regards,
Graeme

Thanks for your reply.
The piping is for a Regner Tram kit, from what I have seen in photos the bends are around 3/8 radius.

Fine sand didnt work for me, the sand prohibits bending.

Try bending around a tube or round stock material, 20mm round bar will give a radius about 10mm

If you have a lathe - or access to someone who can spend a few minutes turning something up for you - then it is easy to make a bending tool. Just a length of brass with a slot 3mm wide in it. The bottom of the slot doesn't need to be rounded or even flat. The diameter of the bottom should be roughly the diameter you want to bend too.

Place the tool in a vice and hand bend the annealed pipe in the slot. That should minimise the distortion. Repeated annealing would be a good idea - bending a bit more each time.

Don't be afraid of trying - if you kink it then 3mm pipe is readily available.

Trevor