Maximum Speed of Lego Smart Motors?

[onthuhlist]

Newbie question. Searched the forums for "maximum speed" but found no answers.

Pybricks gives us control of Lego Smart Motors by specifying degrees per second of rotation. But what is the maximum physical speed limitation for the various motors? I assume it is different for Technic XL motor 88014 and Technic L motor 88013 and Spike Essential small motor 45607. Is there an easy way to reference each motor's max speed within PyBricks, or a simple way to set the speed to a percentage of each motor's capability? It will waste a lot of time for me to trial and error working down from 5000 deg/S or up from 1000 deg/S to figure out the max RPM.

Also, what happens if you exceed the motor's deg/S capability in Pybricks? Does the operating program detect that the motor is not keeping up, and give you a notification? Thanks for your help.

[dlech]

The actual max speed depends on factors like the battery voltage and the load on the motor.

The link below lists the "rated" max speed of each motor type.

https://github.com/pybricks/pybricks-micropython/blob/master/lib/pbio/src/motor/servo_settings.c

I think you can get this value programatically from motor.control.settings().

[dlech]

Does the operating program detect that the motor is not keeping up, and give you a notification?

No it doesn't notify you, the motor will just run as fast as it can.

But you can check motor.stall() to see if it isn't keeping up.

[onthuhlist]

Thanks for the info. Can you help me interpret the page you linked since the listed values are unitless? Should I be looking at angle_d_speed, torque_d_speed, or speed_d_speed, and what are their units? Thanks again, as I was just doing trial and error trying to get it to go as fast as I could. I understand that if a motor stalls, it will go slower. But a smart motor should not slow down due to loads within its capacity, correct? Doesn't the motor use its position sensors to make the speed accurate, assuming the battery can supply the necessary power? Or am I just imagining that things are more sophisticated than they are?

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On Tue, Mar 24, 2026, 4:24 PM David Lechner ***@***.***> wrote: The actual max speed depends on factors like the battery voltage and the load on the motor. The link below lists the "rated" max speed of each motor type. https://github.com/pybricks/pybricks-micropython/blob/master/lib/pbio/src/motor/servo_settings.c I think you can get this value programatically from motor.control.settings() <https://docs.pybricks.com/en/stable/pupdevices/motor.html?highlight=settings#pybricks.pupdevices.Motor.Motor.control.limits> . — Reply to this email directly, view it on GitHub <#2642?email_source=notifications&email_token=AWL53SRAJPAQT6IBOH25OO34SMKJXA5CNFSNUABIM5UWIORPF5TWS5BNNB2WEL2ENFZWG5LTONUW63SDN5WW2ZLOOQXTCNRTGAYTMMZSUZZGKYLTN5XKMYLVORUG64VFMV3GK3TUVRTG633UMVZF6Y3MNFRWW#discussioncomment-16301632>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AWL53SUSYN4VIUKDO2FDTU34SMKJXAVCNFSM6AAAAACW6DFLOGVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTMMZQGE3DGMQ> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[dlech]

Just look for the lines like .rated_max_speed = 1200,. This is the max rated speed in degrees per second.

It sounds like you have a generally correct understanding. Just keep in mind that speed and torque are inversely proportional. So at any given battery power, the max speed is still affected by the load on the motor. The heavier the load, the lower your effective max speed will be.