Introduction: Merry : the Chimney Sweep Robot

About: I'm a maker.

This is the second functional prototype of my project Merry which was first presented in Instructables in the Design for Robotics Contest. From then, it was just just an idea, a 3D render and a robot who works supposedly. Today, many things happened and I'm now really excited to show you a real robot with which you can clean your chimney without effort or climbing on the roof.

I worked a lot to make this robot cheap and feasible by everybody. It will cost you less than 40 euros and you will be prevent from chimney's fire by sweeping more regularly.

This project is part of the Spotless Challenge so, if you love it, don't forget to let it know by your vote !

Step 1: Getting the Parts

I tried to make this robot cheaper as possible. I bought a 11 euros cordless drill in my favorite DIY store and found in it every component needing for my robot. Try to find a similar one, your no name drill should have quite the same components but if some are different, you can adapt the body part using my Solidworks files. You will also need :

  • 4 ball bearings 22*8*7
  • 100mm long 8mm brass rod
  • 30mm long 14mm diameter steel tube
  • 1 switch
  • 100mm long 12mm diameter threated shaft
  • 5mm thick aluminum plate

You also need some PLA to 3D print all the parts, some electrics tools, a 3d printer and it will be better with a CNC machine.

Step 2: 3D Print

The robot's main body and the two gears are 3d printed. You can use PLA or ABS according to your preference.

The biggest part fit in a 125x113.5x36.2mm cube

The main body

This part is quite difficult to print. You might use a brim to get better surface and 0.2mm layers thickness. For the support, I guess you to use ones only behind the 2 motor fix holes. You will have a better result with all support recommanded by your slicer but you will waste a lot of filament for nothing. You just need to be precisely enough for the ball bearings place.

For a good looking, you can sand down the exterior of the body with successively 80, 250 and 800 sand papers for a perfect result.

The gears

The gears are more simple to print. You might use 0.2mm layers and no support. Sanding is more important to get a good contact between the 2 gears.


You can find all the files in this link. I also give you access to all my Solidworks files. If you want to use an other drill or other composent, you will be able to modify more easily the model. If you don't have access to a CNC machine or can't made aluminium parts by someone, you can also print the part "Vilebrequin.STL" 2 times.

→ Google Drive

Step 3: CNC Machining

You need to CNC machine two parts in aluminum to prevent break. You need a 3mm drill a 6 mm thick aluminium plate. You can download my gcode on the following link. I use 200mm/s speed. I also give you DXF and solidworks files in such a way that you can redo the program as usual. You don't need a heavy precision on this part.

Step 4: Eletronics Wiring

Change the led

You can change the original LED for 3.5mm ones. You can have to desoldering the first ones, take over the black fastener and soldering the new ones. You can use a red, orange/yellow and green ones.

Replace the wires

The original wire are quite short. Take new ones, big enough and replace it.

Change the switch and cut the card

The card is too long. All the top of the card is only used to change the direction of the motor with the drill trigger so you don't need it. Cut it with a metal saw and keep only the + et - terminals as in the picture.

Step 5: Crank Shaft Assembling

Cut the brass rod

Cut 3 brass rods at :

  • 27 mm
  • 15 mm
  • 53 mm
Paper sand the rods

Use paper sand to correct the rods diameter and make them fit perfectly in the ball bearings

Make flat contact

Make flat contact as in the blueprint. The goal is to reach a new 7mm diameter and 4mm long (20 for the one in the gear)


Slide in the rods the ball bearings and don't forget the "Came" part. You can down glue all the parts of the crank shaft. Make sure that both axes are co-linear.

Step 6: Final Assembly

After building the crank shaft and finishing the electronics. You can final assemble all the part. You must glue the treated shaft in the bottom of the robot and screw the motor with the ones from the drill. Electronics part must fit in the body and you must be careful with the wire. In the body, tap the four holes with a 4mm diameter tool. You can close the two parts of the body and use 4 M4 20 mm long screws. I personally have some problems with the led, it must be difficult to perfectly fit them in the body.

Step 7: Conclusion

Latest finishes

Your robot is now finish and ready to use. You now just have to screw two sweep's brushes quite bigger than your chimney diameter. Indeed, the robot use the self-blocking effect of the brushes to move.

My concept idea video showing how the robot move :

How to use Merry

Start to fix a rope or a string on the ring of the bottom brush. According to your chimney, you must insert the robot in the tube using in the trapdoor or by dismantling the bottom tube part. Switch on the robot before engage it of course. Now, just wait. Once the rope does not move anymore, pull on the rope. It will inverse the brushes's hair and the robot will go down by itself. You also can help it by keeping pull one the rope.

Spotless Contest

Participated in the
Spotless Contest