3d Printed Dual Band Pull String Car

I've created a 3d printable toy car that's powered through two rubber bands and primed by pulling a sting.

I'll explain how to assemble each printed piece and include each of the necessary files. 

You'll need to have, or have access to, a 3d printer, 2 rubber bands, a bit of string, possibly some modeling glue and some modeling paint if you desire to add some flair to your freshly printed toy car.

If you have any questions, or if there is anything that isn't quite clear, let me know and I'll do my best to explain. 

The wheels consist of two parts, the hub and the treads.

You will need to print the tire treads for the corresponding side of the car so that the treads are facing the right direction.

So that's four wheel hubs and two of each of the left, right tire tread files.

The frame is simple enough.

It consists of holes for the axels to go through for the tires, structure guides, holes and grooves for the rubber band axels and a hole for the pull string to travel through.

There are ten internal components for the toy car, not counting the rubber bands and wheels.

I will discuss how to connect them in an upcoming step, for now just get them printed.

This is the top shell of the toy car.

I may make improvements to it, or design other shells for the chassis if the request to do so is strong enough.

If you are following along at home, make sure that every thing has been printed out so far.

   You should have the following items if everything has been printed out.
       > 4 Wheel Hubs
       > 2 Right Facing Tire Treads
       > 2 Left Facing Tire Treads
       > 1 Car Frame
       > 2 Wheel Axels
       > 6 Gears, 2 of each type
       > 2 Gear Caps
       > 1 String holder
       > 1 Pull tab

The wheel hub and treads assemble as shown. 

A slight amount of glue should be added around the rim to keep the hub and treads secured.

The front axel is the easiest part.
   It requires putting the 3d printed axel through the front frames holes, adding a slight amount of glue then adding the tires to that.

The back axel requires you to insert the axel through one of the holes in the frame then through one of the gears that fit it, then through the string holder, then through the other gear and then out the other side.

This part is fairly easy.

Attach the two printed gears that fit on the two axels that the rubber band will attach to.

Next you will need two rubber bands.
  Place them in the corresponding grooves.
   Hook them over two extrusions coming from the frame near the front axel, one on each side.
   Next attach them to the hook on the axel themselves.
 The order that you do this in is arbitrary.



Then insert the axels into the hole that's located near the front of the rear axel then snap them into the grooves near the front.

[Hopefully everything should line up and fit correctly, if it doesn't let me know.]

You should have two gears, and two caps left, from the internal components.

The gears will fit on the two little protrusions and the caps will fit on what's sticking out of it from there.

You should all a very little drop of glue to the very inner portion of the cap in order to keep it in place.

It's important not to glue the cap to the gear itself, only to the shaft that it spins upon, you want the gear to be able to turn freely.

You should disengage the rubber bands before you do this step so they don't get charged as you spool the thread.


Feed the thread you have through the hole in the back of the chassis and tie it to the string holder.

Wind the thread so it goes underneath then over the casing. Essentially you want the wheels to travel in reverse once you pull the string in order to prime the vehicle for launch.

Attach the rubber bands back to the axels then pull the thread to charge the vehicle, you may have to do this a few times in order to find the right length for the thread and the amount that it has to be wound around the axel to charge the rubber band completely.

Once this has been found out attach the thread to the pull tab.

The last part of your new toy car requires attaching the upper car printout.

There's a little tab in the front so that's the part that will have to connect first than press it together and it should hold together.

If not add a little glue.

That completes this instructable.

I really hope I've designed everything right, I'm pretty sure I have, but you never know.

If anyone does print this out I'd love to know the results and if there's any problems with it let me know and I'll fix it so it becomes a working toy. If you have any suggestions as to make it better I'd also like to know those as well.