### understanding screw torque

Posted:

**February 22nd, 2018, 12:03 am**Looking at different worm gearheads, I notice that "full load" spinning torque does not double when the gear ratio doubles. I assume this is because when the screw turns twice as far to spin the gear the same distance, it generates twice as much friction and heat. I have two questions:

1) Assuming the motor is stalled, does the torque ratio begin to match the gear ratio? Meaning one doubles when the other doubles? Because the instantaneous force on the gear has to overcome the same amount of static friction.

2) In general, I think the torque and the power consumption is highest when a permanent magnet DC motor is stalled. Is this true, and does the exact level of torque when stalled depend on the position in rotation of the inner magnets relative to the outer ones?

3) What is a typical stall torque compared to spinning torque in a 60:1 worm gearhead? Steel worm, bronze gear 1-inch radius immersed in gear oil.

Here are some references:

torque calculator: https://www.engineersedge.com/gears/scr ... lation.htm

torque examples: http://www.rushgears.com/tech-tools/wor ... and-torque

stall torque: https://evmc2.wordpress.com/2014/07/07/ ... tor-types/

1) Assuming the motor is stalled, does the torque ratio begin to match the gear ratio? Meaning one doubles when the other doubles? Because the instantaneous force on the gear has to overcome the same amount of static friction.

2) In general, I think the torque and the power consumption is highest when a permanent magnet DC motor is stalled. Is this true, and does the exact level of torque when stalled depend on the position in rotation of the inner magnets relative to the outer ones?

3) What is a typical stall torque compared to spinning torque in a 60:1 worm gearhead? Steel worm, bronze gear 1-inch radius immersed in gear oil.

Here are some references:

torque calculator: https://www.engineersedge.com/gears/scr ... lation.htm

torque examples: http://www.rushgears.com/tech-tools/wor ... and-torque

stall torque: https://evmc2.wordpress.com/2014/07/07/ ... tor-types/