motorised hoops

the only things that are guaranteed to phase lock, drive wise are gears, toothed pulleys and timing belts or chains and sprockets.

Only gears do the right angled bit... although a flexi drive or a set of UJ's will also do that.

Hmm, those would work - it's the staying in sync part which rules out belts, I would have thought.

Where does the vertical wheel sit relative to the horizontal one? That may or may not rule out the possibility of a 45 degree shaft (and home- made UJs or pegged gears) or even a flexible drive shaft made from some suitable tubing (all depending on how heavy-duty and long-lived this needs to be)

cheers

Jules

Hmm, those would work - it's the staying in sync part which rules out belts, I would have thought.

Where does the vertical wheel sit relative to the horizontal one? That may or may not rule out the possibility of a 45 degree shaft (and home- made UJs or pegged gears) or even a flexible drive shaft made from some suitable tubing (all depending on how heavy-duty and long-lived this needs to be)

the hoops are on the 45 degree angle ">"

whats a UJ ?

Thanks

hang on, lets clear this up a bit

imagine a vertical pole, then the hoops top of one and bottom of the other touch the pole, then as they rotate along each others path they travel around the pole.

so effectively you get this pattern path

does that make sense?

? hang on, lets clear this up a bit

imagine a vertical pole, then the hoops top of one and bottom of the other touch the pole, then as they rotate along each others path they travel around the pole.

so effectively you get this pattern path

Diagram here

direction, or opposite directions?

How fast do they need to turn? Will people be trying to grab the wheels, or are they free to rotate? How long does this need to last before it falls apart? ;-) All of those could easily make a difference to the choice of drive.

Oh, UJ = universal joint. Something from the power transmission for a vehicle would be overkill, but maybe you'll find something smaller (say

Of course going with UJs might be overkill if just rustling up some pegged gears out of wood is good enough...

cheers

Jules

I think if they ran in different directions, the whole return to the same position may be more difficult?

free rotation but only once, then the whole assembly will be move to a new location and spun again (it needs to be portable)

Do you remember the optical illusion of two hoops apparently spinning on each other in Superman, Blakes 7 and other Sci-Fi films? this was achieved with the hoops fixed and the whole thing spinning. I don't want that, the wheels will be turning, the fixed point will only be the central axis.

I thought maby having a disc in the middle to run the two wheels on

Imagine a spinnng top, as it falls over its base stays in once place, the top is 45 degree leant over and its circumfrence is spinning just as I'd like my wheels to move.

speed is another point, the rotation can be as slow as 1 revolution in 3 seconds, but I'm happy to move it manually

Ta follks... I'm sure we will get there

Shafts and a gearbox in the middle. Easy, if you can live with shafts. A drill right-angle gearbox is probably the easiest linkage, if your scrapbin is empty.

Another idea is stepper motors. You might want an opto sensor (the bike tyre valve hole is convenient) and an Arduino or PIC to control them. The advantage of this is flexible positioning of the wheels, as you don't need a mechanical shaft linkage.

I've made peg and lantern gears out of wood before. One way takes a laser cutter, the other takes a _lot_ of time.

We're lacking a lot of relevant data.

- free running decoration, or a tougher load handling mechanism needed?

- occasional use or daily use?

- are tooth edged wheels acceptable?

- 3rpm or 3000?

One simple option if you're using bicycle wheels would be to attach a sprocket onto the end of a shaft on each wheel, and let the 2 sprockets mesh. Good for low power work only though, the contact surfaces will be all wrong for power transmission.

NT

I like the right-angle gearbox idea, otherwise a couple of UJs top and bottom. Vass - I'm not quite clear if this is also supposed to rotate around the vertical pole under power, or if that aspect is done manually?

That thought had crossed my mind, too - but the mention of bike wheels implies something perhaps too heavy for readily-found steppers to turn (not particularly fast either, which may or may not be a problem)

I suspect that a bit of TTL would do for control, so wouldn't necessarily need a micro and programming ability.

cheers

Jules