how to calculate torque/power/speed needed
how to calculate torque/power/speed needed
(OP)
Hi All.
I am looking to determine the torque/power/rpm. needed to lift a 4 kg. load
150 mm vertically in 10 seconds.
I need to use a 6 volt dc. gear motor mounted vertically and connected to a 12 mm
dia. acme lead screw ( steel ) with a 3 mm pitch and 48 % efficiency.
The lead screw nut witch the load is connected to is also steel.
The load guide is a steel tube with a brass bearing.
Please see attached drawing.
Best regards and thanks in advance.
I am looking to determine the torque/power/rpm. needed to lift a 4 kg. load
150 mm vertically in 10 seconds.
I need to use a 6 volt dc. gear motor mounted vertically and connected to a 12 mm
dia. acme lead screw ( steel ) with a 3 mm pitch and 48 % efficiency.
The lead screw nut witch the load is connected to is also steel.
The load guide is a steel tube with a brass bearing.
Please see attached drawing.
Best regards and thanks in advance.





RE: how to calculate torque/power/speed needed
This is fairly simple stuff to calculate I used the formula on this site:-
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Just considering the Acme screw in order to achieve your requirements it would need to rotate at 300rpm and the power required is approximately 0.5W with a torque of about 0.072Nm.
Bear in mind this is without the 48% efficiency included.
I can see from the drawing that it is to lift a 4kg load but whats the actual application of the screw device.
desertfox
RE: how to calculate torque/power/speed needed
I also recommend against designing around components and following up with the calculations. How do you know that the lead screw is adequate without determining the forces, torque, HP, etc.?
I have had bad experiences with using a bronze bushing as a linear bearing when there is a moment involved. The pressure is applied unevenly and these bushings tend to not allow smooth movement of the carriage. Plus lubrication is difficult and cleanliness becomes an issue.
I recommend that you start with some analysis and then select components. Decide on a velocity profile. Determine the forces and size the screw and bearings. Look at the instantaneous power requirements and size your motor to that requirement.
RE: how to calculate torque/power/speed needed
To the OP, is energy efficiency or size critical? Can you leave room to retrofit a larger/smaller one once the assembly is prototyped?
David