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myxpykalix
11-18-2012, 07:14 AM
I'm making a jewelry box for that same little girl who i made the castle bed for. She had her brain surgery and has expressed a desire for something like a jewelry box.
What i'm trying to figure out is a fancy lid with a special way to open it. What i was thinking about was taking this (see pic) design, enlarging it to the size of about an ipad. Then i wanted to inset it into the lid of the jewelry box with some plexiglass over the top so she could see the gears turn from the top

What i want to then do is have a shaft come up thru the center somewhere that would have some type of carving attached that would act as the "doorknob" which when turned, say a half turn would turn the gears and move a pinion that would retract to be able to open the lid.

Here is where i'm lost. I want the "doorknob" to only have to turn a half turn to disengage the pinion but i would like for the gears to spin at least 1 or 2 revolutions. That says to me i have to figure out the gearing correctly.

Seems like what i would need to do is have a small gear on the shaft connected to the doorknob that inturn turns the larger gears.
Then below that a larger gear that acts like a rack and pinion to open this lid.

i have seen small a metal geared combination (like a reducer?) that might do what i'm wanting, if anyone knows about something like that, even if it is for some other purpose i'd like to check it out if you have a link. I'd buy something premade to use it if i could.

I have the stl's of the gears in this pic but I could start with all new gears if necessary. If someone can advise me on how to make this happen i'd appreciate it.
Brian, Andrew this is your chance to show us how smart you really are!:Dlol
Any and all suggestions, even a whole different design idea would be appreciated...:)

myxpykalix
11-18-2012, 10:14 PM
anyone?? i'm stumped..:confused:

Bob Eustace
11-18-2012, 10:39 PM
Jack what about pinching a few ideas from the steam punk light switches?

beacon14
11-18-2012, 10:51 PM
Without getting too much into the details, I think you have it backwards. You would need a large gear attached to the knob, and a small gear to transfer that rotation to the mechanism. That way, a half turn of the knob moves more teeth, making the small gear rotate more than once.

If you have a small gear on the knob, turning it half a rotation would only make a larger gear turn a few degrees.

Sounds like a neat project. Good luck!

myxpykalix
11-18-2012, 11:31 PM
Bob....DUH! I already have:D That was where i fashioned my rack and pinion latch from because it only has to travel between .5 and 1 inch in distance but i wanted the gears to spin way more...

David....thats why I ask you experts!:D Because I would have gotten it
Bass-Ackwards without your advice:eek: thanks

In researching i have found some small plastic gears that were "compound gears" where a small gear was ontop of a larger gear. I couldn't cut these gears that small,i might need to buy them:mad: