What Is It? – the Answer

You got pretty close to guessing the function of our mystery machine but you didn’t quite get it.

Gilles Berthoud needed to test the strength of his new saddle design so he invented this machine to give it a workout. He was pleased to report that his new saddle lasted far longer than comparable saddles. The saddle went 84 hours without breaking. The nose, rails, and crescent all survived intact. Another popular brand of saddle broke after 17 hours.

Here is a very brief video of the machine in action.