GearHeads Corner

Hi,
I'm working on a wooden clock design. The design requires a large planetary gear that will be suspended from a pinion i.e. the planetary gear does not have a shaft. Standard tooth profiles are designed to work when the gears are constrained to be a particular distance apart by their shafts.  They will jam when one gear is unconstrained, right?
Is there a tooth profile I can use so that one gear supports the other without jamming?  Or is this a case of experimenting with the shift, stub and width parameters until I end up with something that works?
Thanks!
Nathan.

Involute toothed gears can run tightly together, especially with greater pressure angles. But the gear will need some constraint other than just the one pinion, or it will swing like a pendulum. What does the gear do, with only one connection? Show us more please ...

If your moving slow youd be fine, otherwise as Justin points out youll end up swinging..

Involute teeth would would fine with that though... and you coudl always add round idlers on the outside rim
at 4 and 7 oclock...

Art

Thanks for the replies.  It's good to know that binding won't be an issue.

I am using two large wheels for the minute "indicator" and the hour "indicator" on my clock.  The wheels will have the hours / minutes engraved around the edge.  There will be a viewing "window" or loupe or some such at the 12 o'clock position on each wheel, indicating the current time.
Since the period of rotation is at most 24/day, I'm pretty confident swinging won't be a problem.

I promise to post some pictures when I get this clock running.  Simulating the mechanism was my first project in Gearotic.  What a fabulous bit of software!

Thanks again!
Nathan.

Good luck Nathan:

  My plexiglass clock uses a similar scheme.. ( in the video on the main web page).
Just make sure it isnt too tight. :)

Art

Hi Nathan,
I've done a number of "hanging" ring gears and they work fine - I'm sure the purists will point out the the friction will be increased slightly but for an hour ring you won't likely notice it.
  In my builds I had to have something to keep the hanging ring from "walking" off the pinion - something like two rings on the pinion to act as a guide.  Even then it still worked.

John

PS check out my avatar

njkotzur;

Could you use 2 friction idler wheels above the pinion on the backside of your planetary? Might work to eliminate swing and hold everything together.

Cheers
Bob