# Is it "Peak" or "Constant" Torque

Hi everyone, is the “motor guide” torque rating on XL sheet given as

Constant or Peak ?

I need to calculate N-m of thrust for the actuators in operation.

I’m using ODrive 6374 150Kv.

Regards Jerry.

Hey Jerry

Its the peak torque. You can run your motor at peak torque for about 30 seconds before you have to start worrying about overheating. Obviously a shorter time than that if its already hot. Your constant torque value is going to depend on how your motors cooled. Without any active cooling like a fan your looking at about 1/3 of peak torque for your constant torque. With good fan on the motor you could could probably get closer to 50% of peak torque.

I would be happy with 33%, as I think it will work well with those figures.

Here is my reasoning behind the question:

And here is the output using this above motor and a 1605 ball screw

Kudos to Dirty @ Xsim

Thank you again regards Jerry.

What is that tool? I want that!

Cheers Stijn

Looks like this tool is ignoring motor and ballscrew inertia. The acceleration is way off.

Hi Crinq, This stuff is way above my intellectual pay grade!! The info is from an XL spreadsheet (Dirty XSim) using Clear Path Servo info (Image 1).

So how do I adjust the info adding motor and ballscrew inertia?

Maybe if it not toooooooo brain taxing we could all learn something from your educated input

Kind regards Jerry.

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Hey Jerry

In addition to what Crinq said, it also looks like your are assuming the ball screws are 100% efficient. While they can be >95%, they are never 100%. To estimate the ball screw and motor inertia you would need to know their moment of inertia. You could get pretty close with the ball screw by just taking its mean diameter and modeling it as a cylinder while assuming the density of steel. The motor will be a little more tricky, but you can also make a rough estimation based on the mass of the shaft and rotor.

With that information you will have a better description of the total inertia in your system and likely much lower acceleration estimations.

Hi Richard, thanks for the info; I have to say this stuff is way over my head, so I can’t afford to assume anything, this is why I ask questions!

And the question came from the usage of a ClearPath Server and the calculation from Dirty whom builds simulators, which it what I will attempt, “with the aid of ODrive”

And I may have bitten off more than I can chew; however with some help from all you bright people, it just may happen.

Many tanks again
Jerry.

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