Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Hi,

I my experience with compound pendulums they are not as isochronous as simple pendulums the longer arcs do take relatively longer than the shorter ones.  This means that it is more important that the escapement gets a constant force to keep better time not just being the right length also I found that the amount of movement required to adjust it is a lot smaller.  Usually there is a third form of regulation either above or  below the fulcrum or point of balance of the pendulum. The pendulum is regulated to say five minutes a day using the the larger weights and then the smaller intermediate weight is used to improve on this.

Many years ago I rescued a old turret clock movement from a cellar in a property we were vacating. As the movement had a pendulum that was around ten feet long whose frequency was about 1.5 second but it would be called 3 seconds in America as both movements (back and fore) are counted, in the UK we are mean and count only one swing. This was so long it wasn't practical to run the clock, as the well as the problem with length the pendulum weighed about 100 lb!

So I made and fitted a compound pendulum with the same frequency with was only 1 metre long say 39 and a bit inches. We are not at home at the moment but I think I took some photographs of the pendulum made and if you are interested I could try and find them and post.

Take care Tony.