The secret of the Dreadco perpetual motion machine

Back in 1981 I was an A Level science student. Suggested reading was the New Scientist magazine, which at the time was a serious academic publication. (It seems to be more general interest science now.) Being a fairly lazy A Level science student, I would read the first third of a few articles before getting lost in the detail, skip the middle of the magazine, which was just job adverts, and read the page inside the back cover, a humorous page written by Dr David Jones under the pseudonym Daedalus. 

I don't remember much of what I read, to be honest, but I do remember that in one issue David Jones issued a challenge to readers to work out how a "perpetual motion" machine he had built worked, with the answer and the names of those to guess correctly to be published in the magazine in the next issue. Of course, this being a serious scientific magazine, there was no suggestion that it was a real perpetual motion machine.

I thought about it for a while, and had an idea as to how the wheel was supplied with energy to keep turning. I wrote to David Jones and he wrote back to say my suggestion was correct. Unfortunately my letter just missed the deadline. The names of two other people who had guessed correctly were published in the magazine. I seem to remember that he wrote that he had decided not to reveal how the machine worked for a while longer, to keep people guessing...

I didn't think about it again until a few days ago when a YouTube suggestion for a video about the very machine appeared while I was watching something else. I never thought that over 40 years later it would still be a source of mystery and debate.

I wish I had kept my letter from David Jones, but as far as I knew he was going to reveal how the machine worked in a week or so, so I chucked it in the bin. Apparently all David Jones' letters about the machine are archived, so my letter could be in there!

So what is the secret? Well, I would hate to spoil a 40 year old mystery. It's not really that difficult to guess. A number of people in the YouTube comments have suggested the answer I came up with. As Virginia Mills intimates in the video, look for a mundane explanation, rather than an exotic one. She also gives a huge clue in talking about Orffyreus' weighted wheel perpetual motion machine. The idea of falling weights adding impetus to a wheel is initially attractive until you remember that there is actually no net input of energy because the momentum of the wheel has to drag the weight upwards from a lower level on the way up. Without a source of energy it won't work.

But with a source of energy?