Hi PD's....& welcome Peter.......... you mention [
steamers] & also [
gearbox's] ....so I assume you intend an electric drive.....

a simple answer to your question for a 1:24 Chieftain class paddler would be a paddle shaft rotation to approx. 180 RPM max
Having said that.......with a low current consumption 12 volt electric geared motor + a good quality electronic speed controller will provide you with realistic start off speed [10 RPM] & take you to say 150 RPM for top speed
The 180 RPM is only a get out of trouble scenario, however the accurate scaling of the paddle wheel components will also have a dramatic effect of the paddling force provided
Now if my assumption of electric is incorrect

....and real steam is intended, then essentially the speed requirements remain the same ....however steam

is a far bigger gambit & ball park
Take the time to read our archives.......any questions....don't hesitate to ask....Derek
