I understand that the M motor has an adequate amount of speed, and the XL motor is best known for its torque. But is the XL motor really faster than the M motor? Or is it the other way around? I am asking this question because I recently saw the L motor, and one reviewer said "It has the speed of the M motor but the torque of an XL motor." I am assuming this means that the M motor is faster...?
asked Nov 14, 2014 at 19:04
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4 Answers
It delivers a maximum torque of 90,4 mNm (600 mA). Without load its rotation speed is around 220 rotations per minute.
It delivers a maximum torque of 45,4 mNm (450 mA). Without load its rotation speed is around 380 rotations per minute.
It delivers a maximum torque of 40 mNm (300 mA). Without load its rotation speed is around 380 rotations per minute.
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Well, I take it you are telling me that the M motor is faster. Now that I think about it, the M motor isn't the fastest motor that LEGO has made. The 9v 2838 motor is by far, much, much faster. philohome.com/motors/motorcomp.htm Nov 15, 2014 at 2:22
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1@TaylorGarrett L and M motors have the same unloaded rotation speed (380rpm) which is faster than the XL (220rpm), however they both have lower torque, which means that they will stall under lower loads than the XL. Nov 15, 2014 at 23:10
Theoretically, in terms of power (speed • torque), the XL Motor is faster than the L Motor and M Motor. The reason being, you can gear up the XL Motor 2:1 and have the following output: running torque of ~7 N.cm & rotational speed of ~290 RPM. However, a small amount of these measures will be lost due to friction and decreased efficiency (by transferring drive through gears). Regardless, comparing these measures to the normal output of the M Motor — running torque of ~3.63 N.cm & rotational speed of ~275 RPM; and the L Motor: running torque of ~6.4 N.cm & rotational speed of ~272 RPM — and we have a clear winner, as far as running torque performance goes. Also, it is worth mentioning that the XL Motor has significantly higher efficiency than both the L Motor or the M Motor.
RPM measurements listed here are the loaded characteristics, not no-load. This is why the RPM numbers listed here are lower than what others have said.
Torque and speed measurements are according to http://www.philohome.com/motors/motorcomp.htm
It really depends on what you're going to be using it for. I'm in the middle of motorizing the fancy branded Lego Porsche and I was gonna use a couple of L Motors to drive the wheels and a servo to handle the steering, but after some research I found that because of all the gears going through the gear selection and drive-train, a powerful amount of torque is required and as Damon very correctly stated, the XL Motors are much more efficient in terms of performance. You might not be getting the same speed but you'll end up regretting buying the L motors due to their lack in torque. To solve this issue with my Porsche I just used a BuWizz controller instead of the old IR setup for more speed, flexibility and less weight as I don't need a receiver.
I bought an XL-Motor a couple of weeks ago, but when I saw a video of the M-Motor I knew it was faster. It seems to be that the XL-Motor can pull so much more due to the increase in the size of the whole motor but takes a lot more time to do a full 360-degree spin, and for the M-Motor it takes about less than a second to do a whole spin. If you want to buy a motor due to its speed but lack in torque, buy an M-Motor. If you want to have a stronger motor that won't get jammed easily, buy an XL-Motor.
If you already have an XL-Motor (or L-Motor) and you don't want to buy another (M or L) motor just increase the gear ratio. Take a huge gear wheel and get a small gear wheel and connect them to your build. Basically what is happening here is the big gear wheel is taking longer to make a whole 360 degrees spin and while it's trying to do that the small gear is going twice as fast as the big gear and therefore makes it go fast.
Here is an image of the motor: 
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1To be honest, both small and big gears will take same amount of time to make 360 degree turn on the same motor. The difference in changing speed/torque these make make is due to diameter (and subsequently number of teeth) each gear has.– AlexJun 12, 2020 at 18:41
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Then how come the gear goes faster then the motor even though it has less teeth and how can the radius of the whole 360 degree spin go the same speed as the smaller gear? I mean the gear is big so it takes longer but if the gear is decreased to the size of the other gear they go the same speed and theres no diffrence in speed.– NerdJun 12, 2020 at 21:12
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I think you are confusing "gear" with "combination of gears". One single gear attached to the motor axis will turn independently of its size. Usually, adding an image to the answer will be very useful for illustrating what you try to explain. Welcome to Bricks.SE. Jun 12, 2020 at 21:36
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As I mentioned, both small and big gear turn with the same angular speed or revolutions per minute as the motor does. Angular speed isn't a parameter of the gear, but rather of the motor itself. You can test this by placing both sized gears on the same axle attached to a motor - they will spin with same speed. Placing each gear independently will result in same angular speed. What you are referring to here is related to gear diameter/radius/circumference or number of teeth of the gear. The bigger the driver gear the quicker driven gear will spin and vise versa.– AlexJun 12, 2020 at 21:36
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Let me clear this up, seems like you're confused about how gears mysteriously move faster/slower when connected together. if you put one single small gear on some random motor, it will rotate. A bigger gear on the same motor will seemingly move slower. Why, you ask? Because the size of the gear is bigger, therefore making the rotation longer, as @Alex said. (same goes for wheels or any other round object) You can also connect gears together so that their teeth touch in order to customize speed, too. Jun 14, 2020 at 18:14