warren (12/28/82)
I received a puzzle as a christmas gift that I though would be of interest to net.physics readers. It is an apparent perpetual motion machine, consisting of a small lightweight top that spins "forever" on a black plastic base. I have seen these other places, and their owners assure me that if the motion isn't perpetual, it at least lasts virtually forever in spite of heavy use. Here are a few facts about the puzzle determined from personal observation: The top is about 1 inch in diameter, made of plastic with an embedded powerful magnet, oriented so that the north and south poles spin with as the top spins. The base is a sealed cylinder of black plastic, about 3 inches in diameter and 1 1/2 inches high. It has a slightly raised rim around the edge to retain the top, and slopes somewhat towards the center. It also has a raised pattern in the form of an '!' mark with the dot in the center of the base. Within the sensitivity afforded by a pocket compass, the base has no permanently magnetic components. The base is relatively light in mass, and the mass appears to be concentrated in the center. When the top is spun on the base, it will drift towards the center. Every time the top comes near the center of the base, it appears to accelerate its spinning, and as a result of contact with the '!' marking be flung towards the edges of the base. The top frequently passes between the two segments of the marking, though this is not critical to the perpetual motion phenomenon. (The top continues to spin if prevented from passing through the gap, and will also continue to spin on a sheet of paper held very close to the top surface of the base.) The top spins equally well in either direction. While I have not tested this in any quantitative way, the top appears to have a maximum and minimum speed. When spun too slowly, it is knocked over by the raised pattern on the base before it can be accellerated. It does not appear to continue to accellerate indefinitely if allowed to remain at the center of the base, though frictional losses would undoubtly impose a limit even if the internal mechanism doesn't The question is, of course, how does it work? It is fairly obvious that something in the base is coupling energy into the top through the magnet in the top. To really understand this thing, you have to explain: 1) How is the top driven, and how is the drive synchronized to the motion of the top (in both directions!). (Remember that the base doesn't seem to contain any permanent magnets. 2) What is the power source that allows prolonged operation with no replaceable parts? Since it was a gift, I have no idea what it cost, but the general construction and packaging suggest to me that it couldn't have been more than about $10. This rules out anything really exotic, like mini nuclear reactors and the like! Have fun with this one, I certainly am! Warren Montgomery (ihnss!warren) PS: If you want one of these things, send me mail and I will return the name and address of the company that makes them or post it to the net if there is an overwhelming response. PPS: I don't own any stock in the company that makes them!
henry (12/30/82)
I've never seen one of the beasts, so I can't say for sure, but I do know one way of building "perpetual motion" machines. It is possible to get *small* amounts of energy literally "out of the air" by picking up and rectifying the 60-Hz signal from nearby power wiring. This signal is omnipresent in industrial civilization (well, it's 50 Hz some places...). You can't get much power, but it can be enough to keep a low-friction device going. What bothers me is that the description of the "perpetual top" implies a fairly small base, and it's hard to get practical amounts of power from the power-wiring radiation without a sizeable antenna. Henry Spencer U of Toronto
rb (01/04/83)
Maybe it has something to do with the earth's magnetic field? Seems unlikely but you never know. -Ronen
kiessig (01/15/83)
Has anyone out there seen some clocks on which the hands are attached to some CLEAR plastic, and there are no visible parts behind them? All you see is the clock hands and a piece of transparent plastic. They are very expensive. Anyone know how they might work? Rick
thomas (01/17/83)
Yeah, it's easy - the pieces of plastic have gear teeth around the edge, and are rotated at the correct rates. (I.e., there is one piece of plastic for each hand.) =Spencer
gh (01/17/83)
I saw one of these clocks with no apparent mechanism some years ago. If I
remember correctly, the minute hand was fixed to the clear disk behind the
hands. This disk was turned at the rate of one revolution an hour by a small
motor in the base that drove the rim of the dial. The really clever part was
the hour hand, which was quite loose, and you could push it about with your
finger, and it would always return to the correct position for the current
time of day. This was done by a counterbalance and a complex little system
of gears in the hub where the hands met; as the minute hand / dial went round,
this drove the gears in the hub and changed the angle of the hour hand relative
to the counterweight (which of course always hung down).
Graeme Hirst, Brown University Computer Science
...!{decvax, vax135}!brunix!ghrandals (01/17/83)
~~~~~~~ original question ~~~~~~~
Has anyone out there seen some clocks on which the hands
are attached to some CLEAR plastic, and there are no visible parts
behind them? All you see is the clock hands and a piece of transparent
plastic. They are very expensive. Anyone know how they might work?
Rick
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The mechanism is rather simple, once you figure it out (and it took me
a LONG time!)
The hands are printed on clear round disks that are the size of the entire clock
face. Each disk sits on a couple of small rollers in the base of the clock,
and is supported so that the disk can turn. The small rollers in the
base are simply turning at the proper rate to make disks (and hence the hands)
appear to "move" at the right speed. Clever.
Not afraid to have a good time with my name,
Randal L. Schwartz
Tektronix Microcomputer Development Products
Beaverton, Oregon, USA
UUCP: ...!{ucbvax or decvax}!teklabs!tekmdp!randals (ignore return address)
CSNET: tekmdp!randals @ tektronix
ARPA: tekmdp!randals.tektronix @ rand-relayjwb (01/17/83)
I have one of the clocks with the clear (glass in my case) which supports the hands. I found it in my parents' attic. I have had to fix it several times so I know how it works. A regular clock motor is in the base. It has a conventional gear. Glued to the glass is a large gear hidden in the outer shell of the clock It's sort of like a rack and pinion made into a circle. Thus the entire glass rotates. The minute hand travels through friction with the glass. It's not rigid so you can set the clock. The hour hand is connected through a series of gears with a weight so it achieves a virtual movement which corresponds to 1/60 the speed of the minute hand. This may be more than anyone wanted to know, but it is how it works. Jack Buchanan
leichter (01/17/83)
The clocks I've seen with hands attached to pieces of clear plastic - actually, glass in all the one's I've seen - are actually very simple: There are two pieces of glass, and the glass itself rotates! Each hand is attached to the appropriate piece of glass. One can also be clever and hang a low-friction bearing on the glass & drive a couple of gears - so one piece of glass can drive several hands. -- Jerry decvax!yale-comix!leichter
berry (01/17/83)
#R:ihuxs:-25400:zinfandel:9600001:000:282 zinfandel!berry Jan 17 11:15:00 1983 The clocks with "no works" have the hands attached to clear plastic disks which are driven from the edge. The works are concealed in the (opaque) case that frames the whole. A clever effect. Berry Kercheval Zehntel Inc. (decvax!sytek!zehntel!zinfandel!berry) (415)932-6900
kiessig (01/17/83)
I guess they could rotate the whole plastic box. The clocks
I saw were square, though. Perhaps rotating a round piece of plastic
inside the square? There certainly weren't any gear teeth visible.
Rick Kiessig
{harpo,megatest}!fortune!kiessig