The Todeschini/Di Bella Device Part II

Professor Laithwaite's article

My original introduction to the Di Bella device was Prof. Eric Laithwaite's article "1975—A space odyssey" in Electrical Review magazine, 28 March/4 April 1975. In this article he quotes an eyewitness, Christopher Hook, who attended the 7th Symposium of Naval Hydrodynamics, Rome, in August 1968. There he was given a hands-on demonstration of a Di Bella device. He says:—

"...When he [Di Bella] arrived with this model without props, paddles or jets I rather naturally showed scepticism, whereupon the Professor thrust his model into my arms. On being switched on the model frog marched me, in a mild manner, towards the door by the action of rotating masses inside..."

I thought this was interesting enough to investigate further.

Background

Prof. Laithwaite mentioned in his article that Di Bella was granted a patent, but he didn't identify it further. In those pre-internet days patent searches were more difficult (and expensive) than they are now, so I didn't try to find that patent. Also, my first attempt to obtain Di Bella's paper On Propulsive Effects of a Rotating Mass was unsuccessful. I did manage to obtain a poor-quality photocopy in 1999. If I had seen it earlier, I would have noticed the second, even more interesting device shown as Figure 4 in the patent (US Patent 3,404,854) and discussed in detail in the paper, which I'll deal with in my next blog post. I now think that this is probably the device referred to by Christopher Hook.

I did see that while in operation, it would be possible to have the out-of-balance mass (of the first Di Bella device) move sinusoidally across its axle, with amplitude that could be varied externally, if desired, in real time. Stripped to its basics, my device was schematically as shown:—

Schematic drawing of my modified Di Bella device

And here it is, as a real physical device:—

My modified version of a Di Bella device. It is similar to the original except
that the out-of-balance mass can, if desired, be made to move across its axle,
at the rate of one oscillation per revolution. Its locus is drawn below.

The moving components, apart from the frame. The out-of-balance mass has an internal
ball-spline bearing, so it can translate but not rotate with respect to its splined axle.
Its position is controlled by a cam follower in its central recess. The user sets the cam
follower's position. And, yes, the hardened splined axle has not just been ground down,
but also threaded at both ends. More "hard-core" work — literally!

Locus for my modified Di Bella device at maximum oscillation amplitude

Tests

When spun up to speed using an electric drill driving via the flexible cable shown, this device would vibrate and move fairly slowly across a surface such as an old wood-topped table. But with only a moderate amount of testing, it was obvious that, like Di Bella's original device, mine also had to rely on interaction with its surroundings, by friction, in order to move. This was always so, whether the out-of-balance mass was moving across its axle or not. So it could not be a true inertial propulsion.