This is a printed pullback toy car that is printed ready
Step 1: Gear One
First off we have to make the gears that are gonna make are car move. We need a gear with 10 teeth, one with 12 and one with 18. This last one is also gonna wind up our spring so on that one we are gonna make a few adjustments. You can easily get gears like this on the internet, sites like crabcad are great for it.
Step 2: Wind Up Gear
This gear is gonna wind up our spring. So we have to make an adjustment. By using the extrude feature we can easily put a ring on the gear that will protect our spring and a holder for the end of the spring.
Step 3: The Spring
The spring is easily made with the tangent arc feature while sketching you just have to switch between 2 centerpoints. With this methode you become to spiral form we want for the spring. After this leave a little edge on the end so the spring can lock into the holder.
Step 4: The Holder
As you can see I left some space in the cabinet for the spring so the spring can lock into place. With this methode the spring won't break when you wind it up to much. After you draw the cabinet for the spring. Draw the to plains that will hold the gears. Don't forget that the second gear needs to be able to move, otherwise the spring will wind up when the car moves forward. To avoid this we have to make sure the second gear (the one that transfers it's motion to the last gear the one that winds up the spring) can move out of the teeth of the last gear.
The holes that will hold the gears have to be bigger then the cilinders holding the gear so the gears can turn.
At last make 2 holes that will hold the wheels.
Step 5: The Wheels
Finnaly draw the wheels.
The gear on the axis of rear wheel will put everything in motion. This will be the second 10 teeth gear.
This gear has to be attached to the wheel.