Race It Back: How a Pull Back Engine Works

This is a cool LEGO project that also shows how pull back engines work. It uses a rubber band which attaches to a gear that is in turn connected to the rear axle. This lets it wind up, and then you let go and watch it zoom!

Fun toy for kids with various Lego pieces to build.

Downloads

Race it back_ How it works.mp4

Supplies

Some Lego pieces may be discontinued, so don't bother with them unless they are necessary or you have them. The pieces may be any color you desire. If there are any repeats of pieces in the list, only use the first one you saw.

-1x Rubber band (preferably long and stretchy, but not too long and stretchy)

Lego pieces:

-4x 24-tooth gear

-1x 20-tooth gear

-1x 12-tooth gear

-2x 2-long Smooth Technic connector

-1x 12-long Plus-Connector axle

-2x Technic Plus-Connector racing wheels

-2x Technic Round-Connector racing wheels

-4x Racing tires

-1x 1 by 8 by 1 Technic brick

-2x 8 by 6 by 1 hollow Technic brick

-1x 7 by 5 by 1 hollow Technic piece

-1x 3-long Plus-Connector axle

-1x 4-long capped Plus-Connector axle

-2x 8 by 6 by 1 ramp*

-1x (8 by 6 to 8 by 4) by 2 curved Technic brick

-2x curved 1 by 1 by 1 brick with 1 by 1 by 1/3 extension

-4x 2 by 4 by 1 brick

-1x 3 by 6 by 1 ramp*

-1x (2 by 10 to 2 by 6) by 2 arch*

-3x 4 by 8 by 1/3 plate

-7x 2-long Technic connectors

-5x 1 by 4 by 1 Technic brick

-2x 1 by 6 by 1/3 smooth plate

-7x 1 by 6 by 1 brick

-1x 1 by 12 by 1 Technic brick

-1x 1-tall round Technic piece, kind of looks like a steering wheel*

-1x 2 by 6 by 1/3 plate

-2x 2 by 2 by 1/3 plate

-2x 2 by 3 by 1/3 plate

-2x 1 by 2 by 1 brick

-1x 1 by 2 by 1 brick with Technic connector

-1x 1 by 12 by 1/3 plate

-2x curved 2 by 4 by 2/3 wedge

-4x 1 by 8 by 1 brick

-3x 1 by 8 by 1/3 plate

-1x 1 by 10 by 1/3 plate

-1x 1 by 4 by 1/3 plate

-1x 2 by 2 by 1 brick with Technic connectors on one pair of opposite sides

-1x 6 by 6 by 1/3 plate

-1x 1 by 6 by 1/3 plate

-1x flat 1 by 8 by 1/3 plate

-2x 1 by 4 by 1 brick

-1x 1/2 bushing

*optional

Building the Car

Connect the two dark grey rectangles to the light grey rectangle in the order shown in the picture.

Pieces used in this step:

-2x 8 by 6 by 1 hollow Technic brick

-4x regular Technic connectors

-1x 5 by 7 by 1 Technic piece

Building the Car

Put the pieces together as shown.

Pieces used in this step:

-1x 4 by 6 by 1/3 plate

-1x regular Technic connector

-1x 1 by 4 by 1 Technic brick

Building the Car

Take the two builds from the previous two steps and connect them as shown. The exposed Technic connector from step 2 goes into one of the middle holes in the 5 by 7 by 1 Technic piece.

No extra pieces used in this step.

Building the Car

This is not a good camera angle, but put the (6 by 8 to 4 by 8) by 2 Technic brick and put it on the side where some light grey is showing on the top, which now becomes the front of the car.

Pieces used in this step:

-1x (6 by 8 to 4 by 8) by 2 Technic brick

Building the Car (optional)

Only do this step if you have the ramp used in the next step. Connect the 1 by 8 by 1 Technic brick to the 6 by 8 by 1 hollow Technic brick as shown.

Pieces used in this step:

-1x 1 by 8 by 1 Technic brick

-2x regular Technic connectors

Building the Car (optional)

Place the 3 by 6 by 1 ramp on the two pieces on the front, then place a 1 by 6 by 1 brick underneath the ramp.

Pieces used in this step:

-1x 3 by 6 by 1 ramp

-1x 1 by 6 by 1 brick

Building the Car

Put the two connectors on as shown. Note that you have to put the other connector in the same spot on the other side. Then place the 4 by 8 by 1/3 plate on top of the arch.

Pieces used in this step:

-2x smooth Technic connector

-1x 4 by 8 by 1/3 plate

Building the Car

Place the 3 plates on as shown. Note that the 1st plate goes right behind the 4 by 8 by 1/3 plate.

Pieces used in this step:

-3x 1 by 8 by 1/3 plate

Building the Car

First place the 1 by 12 by 1/3 plate on the 1 by 12 by 1 Technic brick, then place the two 1 by 1 by 1 with 1 by 1 by 1/3 extension curved bricks on the ends.

Pieces used in this step:

-1x 1 by 12 by 1/3 plate

-1x 1 by 12 by 1 Technic brick

-2x 1 by 1 by 1 with 1 by 1 by 1/3 extension curved bricks

Building the Car

Put the build made in the previous step on the end of the bottom of the two 1 by 8 by 1/3 plates that are over the edge of the piece.

No extra pieces used in this step.

Building the Car

Add the 1 by 8 by 1 brick on the right first, then the 1 by 4 by 1 brick on the left, then the 1 by 8 by 1 brick on the left last.

Pieces used in this step:

-1x 1 by 4 by 1 brick

-2x 1 by 8 by 1 brick

Building the Car

Put the two 1 by 2 by 1 bricks on the edges, and the 1 by 2 by 1 bricks with Technic connector in the middle.

Pieces used in this step:

-2x 1 by 2 by 1 brick

-1x 1 by 2 by 1 brick with Technic connector

Building the Car

Connect the pieces together as shown.

Pieces used in this step:

-1x 1 by 4 by 1 Technic brick

-1x 2 by 2 by 1 bricks with dual Technic connectors

Building the Car

Put the build from the last step where shown.

No extra pieces used in this step.

Building the Car

Put the 1 by 6 by 1/3 plate on the either pieces as shown.

Pieces used in this step:

-1x 1 by 6 by 1/3 plate

Building the Car

This step uses many pieces. I suggest zooming in on the picture to see where they go. Make sure to put the rubber band around the Technic connector before you put on any other Lego pieces.

Pieces used in this step:

-1x Rubber band

-1x 1 by 6 by 1 brick

-1x 2 by 4 by 1 brick

-4x 1 by 3 by 1 brick

Building the Car

This step uses many pieces. I suggest zooming in on the picture to see where they go.

Pieces used in this step:

-2x 1 by 4 by 1 brick

-3x 2 by 4 by 1 brick

-2x 1 by 8 by 1 brick

Building the Car

Follow the order of the pictures. Place the pieces as shown.

Pieces used in this step:

-1x 6 by 6 by 1/3 plate

-1x 1 by 6 by 1 brick

Building the Car

Put the 12 tooth gear on the 3 long axle.

Pieces used in this step:

-1x 3 long axle

-1x 12 tooth gear

Building the Car

Put the build made in the last step on the car as shown.

No extra pieces used in this step.

Building the Car

Put the 24 tooth gear on the other end of the axle from the last two steps.

Pieces used in this step:

-1x 24 tooth gear

Building the Car

Put the pieces together as shown.

Pieces used in this step:

-1x 1 by 4 by 1/3 plate

-2x 1 by 4 by 1 Technic brick

Building the Car

Put the axle through the other end of the 1 by 4 by 1 Technic brick, then put on the 24 tooth gear and the (optional) kind-of-steering-wheel piece.

Pieces used in this step:

-1x 1-tall round Technic piece, kind of looks like a steering wheel

-1x 4 long capped Technic axle

-1x 24 tooth gear

Building the Car

On the build from last step, put a 1 by 4 by 1 Technic brick on the end of the axle, then place the build where shown. The two 24 tooth gears should mesh together.

Pieces used in this step:

-1x 1 by 4 by 1 Technic brick

Building the Car

Follow the order of the pictures. First, slide the 12 long axle in a bit. Then, slide the first two gears onto it. Next, slide the axle in a bit farther, and add the 20 tooth gear. Make sure that the 20 tooth gear meshes with the twelve tooth one. Finally, slide the 1/2 bushing onto the end, and move the axle all the way in.

Pieces used in this step:

-1x 12 long axle

-2x 24 tooth gear

-1x 20 tooth gear

-1x 1/2 bushing

Building the Car

Place the pieces as shown.

Pieces used in this step:

-1x 4 by 8 by 1/3 plate

-3x 1 by 6 by 1 brick

Building the Car

Place the build from the last step with the three 1 by 6 by 1 bricks facing the front of the car.

No extra pieces used in this step.

Building the Car

It may be hard to see, but place the 2 by 6 by 1/3 plate so that it flattens the roof out.

Pieces used in this step:

-1x 2 by 6 by 1/3 plate

Building the Car

Place the pieces as shown.

Pieces used in this step:

-1x 1 by 10 by 1 plate

-2x 2 by 2 by 1/3 plate

Building the Car

It may be hard to see, but put the two 2 by 3 by 1/3 plates on the end, then place the 1 by 6 by 1/3 flat plate in the middle.

Pieces used in this step:

-1x 1 by 6 by 1/3 flat plate

-2x 2 by 3 by 1/3 plate

Building the Car (optional)

Put the (2 by 10 to 2 by 6) by 2 arch on the back of the car as shown.

Pieces used in this step:

-1x (2 by 10 to 2 by 6) by 2 arch

Building the Car (optional)

Place the ramp as shown. Make sure the front of the ramp is at the front of the plate that was placed in step 7, and the back of the ramp rests on the large 6 by 6 by 1/3 plate and the 2 by 6 by 1/3 plate that were placed in steps 27/28.

Pieces used in this step:

-1x 6 by 8 by 1 ramp