Rotary engine
The rotary engine, was one of those things that just worked! Once I knew the systematics I pulled out my bits and built it! Perhaps I was feeling inspired, but everything just fitted together as it should! The instructions for the engine don't use any piece that is currently unavailable, but if you want it to run smoothly you will need to use the old piston head pieces that were available in sets such as the original super car. Sure the new pistons are nice and compact, but they don't have the versatility of thee old chunky type. Have a look at ebay.co.uk if you're desperate for some. I got mine that way as part of a misc. bits auction when I was looking for some replacement parts.
The instructions for the rotary engine come in two parts. The shaft of the engine - which has the pistons etc attached, and the housing or cowling of the engine. It's a multi-part model so both files will need to be in the same directory for it to work in MLCAD.