Servo controlled Silly-String Trigger

by sliptonic, published

Servo controlled Silly-String Trigger by sliptonic Oct 6, 2011

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10510Views 2775Downloads Found in Robotics


This started out as a project to learn modeling in FreeCAD. I've attached the FreeCAD project file as well as the .stl models.

I'm not sure what I'll do with it, but it seems like it would work nicely in some kind of Halloween costume.

The main bracket works like a clip-on spray-paint trigger -- In fact, the bracket should fit other kinds of rattle cans as well.

The servo bracket was modeled to fit a hobby servo I had lying around. I've found that servos have a variety of different mounting screw patterns so you might have to modify this for whatever servo you're using.

A bent bit of paperclip works to connect the servo horn to the end of the trigger.

Here's a short clip of it firing: http://www.youtube.com/watch?v=fPpnoXX5sNc

I just learned that this design is used in the Icarus One spray paint drone by the artist/vandal KATSU.


Print out all three parts.

Snap the bracket into the collar on a can of silly-string.

Attach the trigger to the bracket with a 3mm screw. The bulge in the middle of the trigger should be pointed down and rest right on top of the spray can nozzle.

Tap the two holes in the trigger to 4mm.

Mount the servo to the bracket with the servoplate in between with two 4mm screws.

For additional rigidity, screw the other end of the servo to the plate with two more screws and nuts.

Control your servo with an arduino or other proto board.

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Awsome work!

Soon the cats will live in fear of the couch!

I am attaching a airpressure can to it and a pir.

But I am having some issues with my arduino sketch and before I get more gray hairs do you have a sketch for this?

Hello, I love this design, I printed in PLA, although it seemed like it would snap as PLA is brittle, it didn't, and it works GREAT!!! Thank you, I'm going to incorporate this into a jack-o-lantern with a ping (sonar) sensor for Halloween! Thanks again!! I will post a video once it is done :)

I thought I'd share a few thoughts on this after printing and assembling it:

  1. First Thanks! this is great!
  2. The bracket printed in PLA was too stiff for me to put on a can. I reprinted it in PETT (Actually Colorfabb XT, Eastman Amphora) and it was flexible enough to mount. It swivels a bit on the top, so I would recommend taping it to the can to keep from accidentally spraying yourself backwards!
  3. You mentioned 3mm screw sizes, I didn't have any long enough, and metric screws are hard to find here. I ended up using 6/32 x 3/4 for the servo mount. They bite into the bracket well enough to be retained. The "axel" is 6/32 x1 inch and it self threads into the bracket. I drilled through the trigger to slightly enlarge it so it can move freely on the screw-axel.

Next I want to try to design a servo bracket for those 9G micro servos that can be had for under $2.

Tried to print, the bracket won't skeinforge,

I can't duplicate your problem. I'm skeining it with SFACT and pronterface and it goes fine. The STL also imports into blender without errors and I don't see and holes in the mesh. Any more clues?

Great work , this would be great for Halloween

Needs mounting hardware to attach to a face tracking rig..

Interesting. The US military has been using silly string to find tripwires in buildings that they are clearing. Could we combine this with a turtle shell racer and have a remotely controlled vehicle for tactical use?

Someone needs to put a bunch of spray cans on their mower bot and paint a portrait of themselves on their lawn.

Very nicely made, and clever design! :)

This is really cool! Great work!