I'm not a traction engine guy, but speaking generally, I'd be more worried about rapid wear of the sliding surfaces of aluminium than the differential expansion. Plenty of motorbike and car engines run cast iron cylinder lines in aluminium blocks and operate at far higher temps than a wet steam engine. It all comes down to making the liner a tight enough interference fit then heating the aluminium and dropping in the frozen liner

But rubbing aluminium with a slide valve might cause wear. Steel can run in aluminium, eg Honda camshafts etc, but its usually with darn good lubrication by oil, not steam and condensate!

Post some more details and pics of your cylinder and its problems. Plenty of knowledgeable steam model guys on here can probably tell you how to fix it. I'm sure you are not the first to make whatever missteps have been taken.

I think Hopper and Clive missed the fact the cylinder liner would still be phosphor bronze but the cylinder block would be aluminium as opposed to brass.

Emgee

This is referring to wear of aluminium which is not applicable in this instance.

Emgee

Sam – If you are going to change materials for your block I suggest a chunk of Meehanite cast iron.

1. lower cost than aluminum or brass/bronze, widely available

2. machines beautifully

3. ph bronze valve will run perfectly on a well finished / lapped cast iron surface with little or no wear for years

4. well proven for use with steam – no expansion worries

5. stronger more durable than aluminum and threads will be much less prone to stripping than aluminum

Years ago I bought a stick of 2" Meehanite 2 feet long for about $10 as I recall and have carved out MANY small steam cylinders and parts from it with every success.

The only drawback with it is that it covers everything in a black dust while machining, but this is very minor thing in my opinion.

Don't confuse Meehanite with the continuously cast iron bar that one seller purveys. If it hasn't got 'Meehanite' moulded into it or got a certificate available, it won't be Meehanite. No problem with con-cast bar, but there is a bit of false trades description amongst one or two suppliers.

Granted, Ian, I'm sure that's true. My bar was marked down in price as it was ordered in error by another customer and the metal vendor did not want to ship it back 500 miles to one of the "rust belt" states. He preferred to get some cash on the spot from me instead. I was lucky to find it there that day. I'm pretty sure though that to buy Meehanite today would still be much cheaper than brass or bronze and possibly aluminum in a given size.

I have also used other no-name brand continuously cast bar from my metal suppliers as well, and it was not bad at all, but not as nice to work with as Meehanite.