You’ve probably noticed by now that the new EV3 medium motor rotates around it’s long axis, as opposed to rotating on a cross axis like the EV3 and NXT large motors.

The cool thing about the EV3 medium motor is that it’s compact and elongated, which would be useful in making robot arms with powered joints.  But, we want it to rotate the same way the large motors do.

In the first image below, you can see a partial construction for making this work.  We combine four of the flat triangles (99773 or the older 2905), four of the flat 5-beams with axle ends (11478), and two 3-hole axle/pin connectors (32184) to hold a 24-tooth gear (3648) and a worm gear (4716) together.  Note the use of two yellow flat bushings (32123) to keep the worm gear centered on the 6-axle (3706).

What you get out of this is a gear reduction 1:24 (the round gear turns 1 complete revolution for each 24 revolutions of the worm gear).  This gives you a lot of torque for lifting.

The other useful feature of this combination is that anything attached to the axle through the round gear can’t make the worm gear rotate.  So when the worm gear stops turning the assembly stays locked in that position.

The second image shows the how the gear assembly attaches to the EV3 medium motor with four 5-beams (32316) and six 2-pins (2780).  You can use much longer beams which extend to the data cable end of the motor so you can form an attachment there.

The second image also shows one way to attach something to the working end of the gear assembly – two double-bent 3×7 beams (32009).  There are plenty of ways to connect things, as long as they have an axle hole at the end to go on the axle through the round 24-T gear.

And now you can see a significant advantage to this construction:  because the working axle is held one beam-height above the motor, whatever you attach to it can lay flat along the length of the motor.