Shrink fit Aluminium tubing

Hello All!

I am making an exhuast muffler from aluminium. It will comprise of 3 parts; two 'end caps'and an aluminium body.

The body is from 18mm OD tube, the end caps from aluminium stock.

My question is... fitting the end caps, which I intend to press in.... I'll explain.

The ID of the tube is 15.00mm. When I heat the tube (well over 120 degrees) the ID is now 15.10mm. What I intend to do is turn up the end caps ona a lathe, with a shoulder of (say) 15.15mm, heat the tube and then press them in and finish machining the muffler when cool. The tube now grips the end caps.

When the muffler gets hot (attached to a model four stroke engine) then all the aluminium parts should expand at the same rate, keeping the caps in place.

I've looked at commercial mufflers (particularly OS and SC) and they are made with end caps, with no 'weld' being evident.

Should I also reinforce with JB weld or whatever?

Thoughts anyone?

Steve

Hi Steve,

I made some silencers for an OS 300 flat twin four stroke many years ago using a similar method and it worked fine. Trouble was they were so effective, once the model flew a short distance from you you couldn't hear the engine at all. Dead stick landings are always a little exciting when you don't hear that the engine has died on you.

Bob.

Great Bob, I feel as though I'm on the right track. Seems like there are no baffles in a FS system,so fairly straightforward!

Oddly enough, I NEVER thought to go out and buy one...

Edited By Stevo on 11/05/2015 17:47:31

Another option is to bore out the end of your tube to say 17mm for a depth just greater than the thickness of the endcaps.

Make the endcap 17mm dia with a slight taper to its thicknes

Pop the cap into the recess and then spin the edge of the tube to close it up around the endcap which then becomes captive. You can just use a bit of round bar in teh toolpost or if you have a bearing on a bar nudger you can use that.

Or bore out the tube and screwcut for some end caps, same as making fueltanks

Never thought of the spinning option, Jason, thanks...

I got some aluminium welding wire from Alutight at Harrogate. What can I say? - it works a treat and might be worth trying.

Neil

Plus 1 for the aluminium weld/braze wire. I got mine from here.

When making my Dyno I got a bit enthusiastic when milling:

Lump of ally brazed on:

Finished crankcase with patch:

The join line is rather more visible in the photo than in real life but no gaps. It seems to be good stuff.

But I like Jason's swaging method, probably what I'd use.

Rod

If you can bore a little step in the end of the bore,push in the end plug, then pien the end of the tube over, and you should be ok. Thats a suggested method used for making hot caps for Stirling Engines by James G. Rizzo.

Ian S C