Provided you have the tools and the servo you can built this for under a couple of bucks. The actuator extends with a rate of about 50mm/min. It is rather slow but very powerful. Watch my video at the end of the post where the small actuator lifts 10kg vertically.
- hobby servo
- standard hobby brass tubing
-OD: 4.0mm, ID: 3.4mm
-OD: 5.8mm, ID: 4.5mm
- standard hobby styrene tubing
-OD: 4.8mm, ID: 3.5mm
- M4 studding
- 2 x M5 washers
- 2 x M4 nuts
- 5 minute epoxy
- multi-strand cables
- heat-shrink tubing
- standard tools – screwdrivers, scalpel, files etc.
- dremmel multi-tool with ceramic abrasive disk, or similar
- hand-drill + 4.9mm + 2.5mm drill-bits
- M3 tap
- M4 tap
- soldering iron
- glue gun
- small vice
- small saw
- sanding paper (relatively fine)
- small flame torch
Step 1: Remove mechanical stop - drill bottom case cover
- I will be giving instructions based on the dimensional parameters of the Hitec HS-300. The procedure remains the same for any type servo. I strongly recommend you read the whole post before you start. So lets make a start, shall we?
- Open your hobby servo, remove control electronics, feedback potentiometer and mechanical stop on the servo’s output gear.
- Solder new cables on the servo motor’s leads.
- Drill two 4.9mm holes on the servo case bottom cover. These should be located longitudinally along the centre line and 9.5 mm from each end (this applies on the Hitec HS-300 and is also true for many standard servos but depending on your servo type there might be differences). The M4 thread will come out from the servo body using one of these two so this hole must be located directly below the centre of rotation of the servo’s output gear. Be very careful since this alignment is very important! If you don’t get it right you might have to use a new servo! The more accurate you are, the longer your servo will endure.
- Measure the dimensions of the rotating shaft of the potentiometer on the servo’s original electronics – note the geometry in general. The shaft should be flattened right at the tip in order to prevent it from freely-rotating once inserted into the servo’s output gear.