# Weak and Cheap Linear Actuator? [closed]

I have a tiny tube that sprays lubricant but I need it to move between some holes in a line. The total distance is only 10 inches.

So imagine the holes like this:

[ o o o o o o o o o o ]


And I need to move the lubricant tube between them.

I think I need a linear actuator to move the tube, but it doesn't need to be strong at all (less than 1 lb of force) or very accurate. If it lubricates a little bit off center it doesn't matter.

My issue is that linear actuators are so expensive! I'm currently leaning towards building one with Knex or Lego Technic and a servo. But does anyone know of a cheap/weak/inaccurate hobby option for less than \$30?

• Shopping is off-topic. May 1 '17 at 1:35
• This is off-topic. But consider a belt-sled system to translate rotation motion into linear motion. Ya know, like a 3D printer. But instead, it's a 1D printer. 1/3 the price... May 1 '17 at 1:55
• @uint128_t That is a great idea and I actually already have the parts for that. Thanks! If you post this as an answer I'll mark it. I'm laughing at myself for not thinking of this. :) May 1 '17 at 2:34
• I'm voting to close this question as off-topic because it is a mechanical design problem rather than an electrical design problem. May 1 '17 at 4:42
• Arrange 10 holes in a circular arc and connect circular arc to the linear arrangement via 10 flexible tubes.
– Chu
May 1 '17 at 9:03

## 2 Answers

A hobby micro servo and a fabricated rack and pinion with a worm gear.

Or rip it out of a dead cdrom. Dime a dozen.

• A hobby servo won't begin to have enough travel, unless you remove the endstop and modify it into a DC gear motor with goofy drive electronics. May 1 '17 at 4:42

worm gear is good but long, and you still need a datum optical sensor.

Also a cog belt drive from a stepper motor is very accurate with one optical end-stop for calibration by design. these are all used in any cheap printer or scanner. Controller is simple if you can program a uC card with motor driver. Otherwise, beyond scope of this questioner.

Stepper drive cards are usually direction and step# or step in/out from "home" sensor. Pulley size & steps per rev determine resolution.