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I am very new to Lego, and I want to create a simple horizontal sliding door. I'm using a medium linear motor to drive a linear actuator which is attached to the door. The problem is the motor does not line up with the linear actuator.

How can I fix this?

Lego linear actuator

4 Answers 4

31

The axle is misaligned by half a stud, so an obvious approach to this problem is offset your motor by half a stud.

The technique of offsetting bricks by half a stud is known as AZMEP (from the german "aus zwei mach eins Plättchen", meaning offset of half a stud), which is a specific case of the SNIR (Studs Not In a Row) technique.

As it has been already pointed out, one way of doing AZMEP is using part 3794, Plate, Modified 1 x 2 with 1 Stud, Jumper AKA "jumper plate". You can just pop a few of these underneath your motor:

jumper plate

The Unnoficial LEGO Advanced Building Techniques Guide (oldie but goodie, available in gratis PDF) lists a number of other bricks that can be used for the AZMEP technique, e.g.:

AZMEP tube-to-hollow-stud AZMEP technic bricks

I'd suggest trying out a liberal application of 1x1 round plates on the underside of the motor, clip each round plate to the space between 4 studs on the baseplate:

1x1 round plates under motor 1x1 round plates on baseplate assembly with 1x1 plates, oblique assembly with 1x1 plates, top view


As Sander has pointed out, you can also use technic bushes to offset things alongside axles by half a stud. In your particular assembly, this can be useful to effectively widen the linear actuator from 3 studs to 4 studs.

I suggest the usage of 2L axle + pin plus technic bushes:

Assembly with 2L axle+pin

If you're short on parts, you can also consider using 2L technic pins under tension:

Assembly with 2L pins, top view Assembly with 2L pins, oblique

...but be aware that this assembly is way flimsier, and the pins will wobble around. You'll need to provide extra support to the technic 1x4 bricks (blue 1x8 in my diagram). In other words: add 6-stud wide bricks or plates to both the top and the bottom of those.

Another option is to use thin liftarms to fill that half-a-stud gap:

Assembly with liftarm


Finally, another solution is to forego the baseplate entirely and use an assembly attached to the motor's pin holes. Note how the motor pinholes are 3-stud wide, which are offset half a stud relative to the motor's 4-stud wide body.

There are multiple ways of achieving this, but I'll illustrate using 39793 Technic, Pin Connector Block, Liftarm 1 x 3 x 3 and 2905 Technic Liftarm Triangle:

Assembly with liftarms Assembly with liftarms, exploded

I think the most compact solution possible needs a 92907 Technic, Axle and Pin Connector Perpendicular Split:

Compact assembly

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  • 1
    It may be worth pointing out that there is now a modified 1×3 with 2 studs (double jumper), which is ideal for the footprint of that linear motor.
    – KRyan
    Jan 6 at 16:01
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    Isn't your example with 3L-axles with stop physically impossible to assemble? Jan 6 at 16:15
  • 1
    Oh wait, the 3L axles with stop would need to slide through the interior of the linear actuator piece. You're right. Working in CAD sometimes does this to me. Jan 6 at 16:55
  • Last solution would benefit from using half pins with linear actuator rather than full sized 2L Black pins. And, to be precise, you'd want to switch 2L round connector with something like 6538b or 6538c to transfer power.
    – Alex
    Jan 6 at 18:51
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    "Half pin" is community name for Technic, Pin 1/2, similarly to "Apollo" and "Erling" bricks. [Technic, Pin 3/4 ](bricklink.com/v2/catalog/catalogitem.page?P=32002#T=C) could also be used here, but I think this wouldn't be as rigid assembly as I wish it would be.
    – Alex
    Jan 7 at 6:29
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An alternative is to shift the linear actuator by half a stud using eg. a Technic Bush 1/2 Smooth or Technic, Liftarm Thin 1 x 2 - Axle Holes (or any other thin liftarm) as spacer on both sides to control the horizontal alignment, and use plates to control the vertical alignment.

enter image description here

enter image description here

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  • This is non-trivial, since the linear actuator is connected by pin holes, not axle holes. Jan 6 at 9:09
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    @IvanSanchez If a more secure connection is desired, the longer thin liftarms have pin holes Jan 6 at 9:51
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You can do this by utilising some Technic pieces - CV or U joints. Each solution requires two of each element.

Solution 1

Technic, Universal Joint 3L

enter image description here

Solution 2

Technic, Steering CV Joint Axle

enter image description here

Technic, Steering CV Joint

enter image description here

Solution 3

Technic, Steering CV Joint Axle, Wide

enter image description here

Technic, Steering CV Joint, Large Ball

enter image description here

4

To solve this, you need jumper plates to line up

jumper plate - from BrickLink jumper plate - from BrickLink

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  • 1
    It may be worth pointing out that there is now a modified 1×3 with 2 studs (double jumper), which is ideal for the footprint of that linear motor.
    – KRyan
    Jan 6 at 16:01
  • I didn't, but only because I didn't know it would work better; I've added it now
    – RSchulz
    Jan 6 at 19:30
  • I don't have any variation
    – Eric
    Jan 7 at 14:27

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