Sorry to rain on Bohm but those engines give Stirling engines a bad name. They are rather poorly designed. (I sold my Bohm.)
My good hot air engines will run and run and not over heat. Also they easily run accessories (Wilesco or Mamod ones.)
The glass cylinder alpha engines being sold from China are generally very good but my best ones still being produced are my PM Research engines.
Check out this one, it is only supposed to be a fan, but it has enough torque to run a Mamod workshop and then some!