Welcome to Paddleducks......
With the range of steam powered models, both paddlewheel and prop driven, there is bound to be something that will allow you to continue your passion for steam, but without the weight of a loco. Many paddlers were fitted with beam engines, though how well they would work in model sizes may be an issue - A lot of weight relatively high up doesn't help with stability!
Once you posted a few messages, you will have access to our Downloads section, which has drawings and articles for all sorts of stuff in it. Hopefully we can give any advice and help you may need whilst making a choice or during the build.
Regards
Eddy