Copper or Steel for Displacer Cylinder?

[portlandron]

I am building the 1/4 inch scale Rider-Ericsson Hot Air Pump Engine from Myers Model Engine Works.

Myers supplied a piece of 2" steel tube for the displacer Cylinder however in the book STEAM & STIRLING by Fitt they talk about using a piece of 2" copper tube for making the displacer cylinder, which I have a piece of.

For those of you with more experience with this type of engine then I have would using copper for this item make it run better?

 

[Blogwitch]

I made a brass one after a friend tried to straighten his one up in the lathe and the whole lot collapsed inwards.

http://madmodder.net/index.php?topic=4831.0

It might give you a few pointers on how to go about things

BTW, the engine ran perfectly with the brass one installed.


John

 

[Orrin]

I've built one of these engines using the Myers casting set. For the hot cap--I assume that's what your question is about--I used steel and closed the end of it with a copper disk. The copper provides good heat transfer.

You don't want to use copper for the sidewalls of the hot cap, however. It conducts too much heat upward toward the cold end.

Likewise, the displacer piston should be made of a poor conductor of heat and made as thin as possible to minimize heat from the hot to the cold end.

My R-E turned out very well. It will run off the heat from a birthday candle. I had to build a second burner for mine that was much smaller than the one in the plans; it has half as many gas jets. I'm going to have to build a third one because my half-size burner still puts out too much heat. I've decided to try a Jerry Howell burner.

Here's a hint about burners: Don't build it as tall as called for in the plans. It will protrude too far out the bottom of the furnace and the legs under the engine won't be tall enough. Take a look at most folks' R-E engines and you'll see they've put wooden sticks under the legs to raise them up. There's no reason for this if you make the burner shorter. Doing so will allow you to enclose the bottom of the furnace.

You can see how I did mine, here:
http://users.moscow.com/oiseming/lc_ant_p/pic_Pr10.htm

Good luck.

Orrin