There are number of people who make dumbbells for installation in the home, roof, garage or mobile belfry and who provide design details for DIY construction.   These can be connected to a PC running Beltower.

Typical designs can be found at:

• John Norris's Mini-Dumbbell

  DIY or ready made, small ones (2 ft dia. wheel) for the home and increasingly for use on portable towers for demonstrations.
  
  

  Saxilby Ringing Simulators

  Top quality, ready made, portable dummy bells in wooden frames, either one bell (Wombel) or grouped to form a campanile.