Largest amount of weight on a high torque movement?

Posted: Fri Oct 29, 2010 2:49 pm     Post subject: Largest amount of weight on a high torque movement?

I have designed and laser cut custom gears for a clock. The main drive gear would run off of the hour hand on a clock movement. The design requires a ball to rotate to show the time. This ball's weight is supported by a brass shaft and however the final gear rotates this ball about the support. The ball that I am looking at using is roughly three pounds.

This brings up my two questions. First, are there any clock movements that have only the hour hand? Second, will a high torque movement have enough power to rotate this ball?

Thank you in advance for your help.

Posted: Fri Oct 29, 2010 9:14 pm     Post subject:

I doubt the high torque movement would have enough power to drive a 3lb ball. The high torque movement requires specially counter-balanced, lightweight, aluminum hands. Although the motor has a bit more torque than a standard movement, the movement design is more so orientated to drive length (longer hands) rather than weight (heavier hands). If you could lighten the weight of the ball considerablly, the high torque could be an option. Testing would need to be done to ensure the movement could run the hand properly without loss of time-keeping.

Movements should be able to drive only the hour hand. Simply omit the minute hand (which would mount on the hand shaft after the hour hand). The hour hands of quartz movements are typically designed to be a friction fit on the center hand shaft (so there are no additional fasteners required to secure the hour hand).

Posted: Sat Oct 30, 2010 3:14 am     Post subject:

You are really going to need an electric motor to drive that weighted ball (rotesserie motor 1 rpm). You really need a hollow sphere, then you could get a plain electric clock motor. In my experience the high torque movements have just enough power to drive a very light set of hands.

Here is a link for the hollow sphere's.

http://www.wagnercompanies.com/spheres_and_hemispheres.aspx

For motors I would check ebay, robotics, or surplus dealers. 1rpm motors that come to mind are the electric rotesserie, and disco ball motors.

http://www.sciplus.com/category.cfm/subsection/18
http://www.surplussales.com/motors/Motors-1.html
http://www.blowerwheel.com/gearmotor.htm

Posted: Sun Oct 31, 2010 5:16 am     Post subject:

Thanks for the answers, I had a feeling the the clock movements wouldn't be strong enough but I figured it was worth a try. Unfortunately I will not be able to use a ball that is hollow or less weight as this part has already been completed. I appreciate the ideas for the motors, however they would take a lot of additional gearing to work. My initial drive gear has to rotate twice in a 24 hour period, a 1 RPM motor rotates too fast.

Has anyone ever worked with a Synchron motor? I have found some that have rotations of 1 RPH and one that rotates once per day. The slower motor is advertised for use with telescopes, however I haven't seen any documentation on the amount of torque they put out.

Posted: Mon Nov 01, 2010 10:26 pm     Post subject:

You are going to have to talk to the mfg of the motor, as that is a huge amount of mass you are trying to turn.