Shrinking Brass tube

Is it possible to shrink brass tube slightly?

I was at the hobby store, and bought some #2 pushrods to make rudder shafts, but the closest brass tube ( or any kind of metal tube) was 1/8 inch, which is close, but not correct. It’s important to keep the gaps small on the rudder log to keep water out.


Put it in the freezer!:devil3: :devil3:

And that will permanently shrink the tube to the size I want it to be? :confused: :confused:

The trick is to keep the tube high enough so the top will be above the waterline. Then leakage becomes impossible even with a loose fit.

Is this for your Footy?


That’s how I build them, but there’s some merit to having the good fit to eliminate slop. A sloppy rudder makes the boat hard to steer straight, IMO.

I was thinking of heating the tube with the steel rod inside, and rolling them between some boards or metal plates. I’ve seen people shrink sheet brass by hammering it together, so my method is a little like that.


I use to put teflon tape (what plumbers us on threads) on my pintals for my full size boat. Just wrap it around untill you get the fit you want.

I was considering using some gold foil, but I think that would be difficult to get it into the shaft log without nicking or cutting it. I think Teflon tape would be about he same, and only 1 layer would be needed.


Oh, ok…I thought the question was about leakage…
I doubt that a little bit of looseness will make any difference.

Well, all I can say is give it a try & let us know if it works. If you’re really all that worried about it, perhaps you could wax the rod & fill up the void with epoxy. Or you could wrap the rod with aluminum foil & insert it in the tube. How about some thick grease? Maybe that would help with the leakage “problem” at the same time. Let’s see a picture of the boat.

I know what to do…

Using either hard or paste solder, I will coat the shaft with solder and then sand it to fit in the shaft. That will be both hard and permanent.

you could try roller peening the tube.
put the smaller shaft inside, then with something solid, like metal pipe.
put the assembly on a hard surface, and mush down while rolling.
just a thought.
i’m going to try it now with some alu tube.
tell ya if it works in about 10 minutes.

ya, it worked. i just did it with aluminum, and it’s way softer than the brass.
i guess ya just gotta mush harder.

Thanks for Tryin,Nigel.

Maybe you can squeeze down the brass tube locally to prevent play between oversized tube and a rudder shaft.

Take a tube cutter and set it so it just squeezes a little way into the tube. You will be trying to just squeeze a ring in the tube at each end of the rudder shaft, not actually cut the tube. If you go a little at a time you should be able to squeeze a ring just a bit then check for slop, then squeeze some more, check, etc.

When you are happy with the fit you can put some waterproof grease inside the tube on assembly to cut down on friction at the squeezed rings.

This was written up in either the “EC12 manual” or “Optimizing the EC12” as a method of making a “below waterline height” rudder tube be waterproof. And it does work for that as well.

Some electric or scale guys use that method to make prop shafts.


The solder idea sounds like it would work.

I always buy the two sizes of brass tubes that fit one inside the other. Then I don’t have the dis-similar metal corrosion problems, AND they are made to fit inside one another.