I have made 3 tiny engines and working on the 4th.
I've almost finished a tiny Jenny Wren boiler. Steam line out is only approx 2mm diameter.
In Tubal Cain's plans (Building Simple Model Steam Engines Vol. 1) the boiler is committed to serving steam to the one engine.
Could I make a little manifold to run 3 or 4 engines at once off the same tiny boiler or is this simply impossible and silly for reasons that a Newb like myself may not yet comprehend ?
I wouldn't expect all 4 engines to run for very long at the same time, I'd be happy with 20 seconds, would be fun to see them all running at the same time.
If a manifold is impractical how do people avoid committing one boiler to one engine I was thinking that the boiler line could terminate in a small brass block and I could somehow plug and unplug the engines one at a time into that block.
My boilder below and some pictures of finished Jenny Wrens made by other people can be seen here
The one in the palm of the hand gives a good idea of scale.

Bill