Repair toy with 3D printed parts


A month or so ago my son received a very basic remote controlled car. Being 18 months old, he unsurprisingly managed to more or less break it in a couple of weeks…

CarAndRemote

The car and its remote

This is one of those really cheap toys that makes more noise that it actually does things.

It has only 1 motor at the back, the front wheels don’t even touch the ground and to turn it actually goes backwards which blocks one wheel and allows only the other one to move, hence always turning in the same direction (this is sooooo annoying ! :) ).

Anyhow, as any father that has nothing else to do and was looking for an excuse to do something with my underused 3D printer, I set up on fixing it…

I started by removing the old motor and gears and fitting new 3D printed small gears on the rear axle (which is actually split in 2, so the 2 wheels are already independent):

Small gears that go on the axle

Small gears that go on the axle

Then it was time for the bigger gears that go on the new motors (for which I used a couple of Solarbotics GM9 that I had lying around):

Big gear

Big gear

The most “challenging” part was to create mounts for the motors, as I didn’t want to simply glue them in place (mainly so that I can re-use them, but also so that I can replace the gears if needed):

Motor mounts

Motor mounts

Motor mount and gear test

Motor mount and gear test

Hot glue is always my friend :

Motor mounts close up

Motor mounts close up

Right motor and mount, nothing on the left yet

Right motor and mount, nothing on the left yet

And here is the final result, which works surprisingly well. I’m really curious to see how long the PLA gears last before they wear out or break:

Final version

Final version

It might be worth mentioning that I used:

  • Inkscape to draw the gears (really great tool) and the complex shapes of the motor mounts
  • OpenSCAD to extrude the drawings from Inkscape into shapes and export to STL
  • Cura to generate the GCODE from STL and do the printing

Here’s the OpenSCAD code for reference (it’s really simple, the little complexity there was, was in generating the initial drawing with Inkscape)


// GEARS
//linear_extrude(file = "BigGear.dxf", height = 5, center = true);
linear_extrude(file = "SmallGears.dxf", height = 3, center = true);

// MOTOR MOUNT 1
union(){
	translate([0, 27, -15.5]){
		difference(){
			cube(size=[33, 18, 5]);
			translate([7.5, 9.5, 0]){
				cylinder(h=100, r=1.5, center=true, $fs=0.5);
				translate([18, 0, 0]){
					cylinder(h=100, r=1.5, center=true, $fs=0.5);
				}
			}
		}
	}

	difference(){
		linear_extrude(file = "SolarboticsGM9_Fixation_Path.dxf",
				height = 21, center = true);

		translate([16.5, 0, -2]){
			cube(size=[6.5, 100, 3.5], center=true);
		}
	}
}

// MOTOR MOUNT 2
union(){
	translate([0, 10, -15.5]){
		difference(){
			cube(size=[33, 35, 5]);
			translate([7.5, 26.5, 0]){
				cylinder(h=100, r=1.5, center=true, $fs=0.5);
				translate([18, 0, 0]){
					cylinder(h=100, r=1.5, center=true, $fs=0.5);
				}
			}
		}
	}

	difference(){
		linear_extrude(file = "SolarboticsGM9_Fixation_Path.dxf",
				height = 21, center = true);

		translate([16.5, 0, -2]){
			cube(size=[6.5, 100, 3.5], center=true);
		}

		cube(size=[20, 54, 60], center=true);
	}
}

Yes I know, I ended up spending far more time and used parts that cost more than the whole car, but it was nevertheless fun!

Now my design is undergoing the most demanding of tests, as I’ve given it back to my son. If it’s still working in a few weeks, I might consider improving it even further. There are several things I’d like to add:

  1. be able to go backwards and turn in both directions
  2. have proportional control
  3. control direction and acceleration with an accelerometer by tilting the remote control wheel

But again, I’m not sure that it’s worth investing any more time in this platform…

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2 Responses to Repair toy with 3D printed parts

  1. Pingback: Community Corner: Projects Shared By A 3 Year Old Engineer and Dozens More « adafruit industries blog

  2. Pingback: Maker Dad Repairs Broken Toy with 3D Printed Parts #3dthursday « adafruit industries blog

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