I made it. And it works perfectly
The secret is in the rotating device you use and the kind of spanking/whipping instrument.
First - the rotating device should have adjustable speed and be powerful enough to handle with sometimes heavy object.
I used the amateur hand drilling machine with the potentiometer and fastened it horizontally to the edge of the table.
Second - the coupling between the machine and the whip. This is the round rubber plate with the bolt in the middle(you can buy it with the machine). I made two holes in it and used some threaded bolts to fasten the whipping instrument.
Three - the whip iteself. Because I prefer the strong impresions, the whip I made looks really severe, although when used with the machine its rather harmless. It leaves nice marks anyway.
The whip is made from three pieces of rubber hose. First, the thickest, about 40 cm long, serves as a handle and is pinned to the whipping machine. Second piece of rubber, about 16 mm wide and 100 cm long is partly inserted and glued into the "handle". The 20 cm piece of flexible plastic is insterted and glued where the hoses overlap.
The third hose, 10 mm thick and 30 cm long is inserted and glued into the middle hose.
Alltogether it gives you 1,50m long, pretty heavy whip.
When its fastened to the slowly rotating drilling machine it hits with the reasonable power, getting the velocity at the end of the downwards move.
You can adjust the speed and the power simply by potentiometer on the drilling machine.
I sometimes use some some special resistor device which enables you to adjust the velocity even if you are immobilized on the bed or bench.
Perhaps I make some photo and send it here.