Category Archives: Vehicles

Lever-pull Wind-up LEGO Car

Lever-pull Wind-up LEGO Car - right side view

Inspired by Isogawa Yoshihito, I decided to try to make a rubber-band powered LEGO car that could be wound up using a lever. His method of creating a wind-up LEGO machine is quite ingenious. I’m not sure if ISOGAWAY came up with it, but I assume he did.

I will try to describe how this LEGO machine works, but the video below might be more helpful. The car has a lever which is attached to a large gear. This gear is part of a set of gears are placed so that turning the large gear turns other gears several times (using the gear ratios). One axle on the car turns freely, but another is attached to a set of three gears (this could be as few as two or as many as several). One of the gears in the set that connects to the axle rests freely on one of the gears in the set that connects to the lever. You can see this in the image below. The gear in between the two yellow pieces is resting on the gear to its right.

Lever-pull Wind-up LEGO Car - gear close up

When you pull back the lever the gear on the axle set is forced upward and nothing happens (it just bounces on the gear that spins as you pull the lever back). However, when the lever is released, the rubber band pulls it back the opposite direction. This forces the gear in the axle set downward. It basically gets “stuck” and it’s forced to spin rather than bouncing up and down like it did when you pull the lever back. It’s quite clever (I didn’t come up with it, unfortunately.)

Here are a few more pictures so you can see how the gears are connected.

Lever-pull Wind-up LEGO Car - gear angle viewLever-pull Wind-up LEGO Car - gear angle view 2

Lever-pull Wind-up LEGO Car - gear close up 2

Lever-pull Wind-up LEGO Car - side view lever pulled Lever-pull Wind-up LEGO Car - front view

The main downside to this LEGO car is that it’s distance is somewhat limited. Obviously it can be geared up to go fairly far, but it’s limited by only half a turn or so of the gear connected to the lever. With this design, at least, you can’t just wind up the car so that it will go a very long distance. In the video below, you can see that it can at least go ~8-10 feet, maybe more depending on how well it’s coasting.


Simple Power Trailer Modification for LEGO Technic Tracked Crane 9391

lego-technic-tracked-crane-9391-built lego-technic-tracked-crane-9391-box

The Technic Tracked Crane (9391) is a great, inexpensive Technic set, but it doesn’t have any power. I wanted to do a simple mod to make the tracks spin.

Getting power to it is fairly easy if you’re willing to include the trailer. This method replaces the axle that rotates the upper portion with an axle that drives the tracks.

The first step is modifying the Tracked Crane so that the tracks can be driven and a trailer can attach to it.


First just replace the axle on the very bottom that runs parallel to the tracks with a longer one. You’ll probably also want to get rid of the black gear that spins the top portion of the crane (since this gear will constantly turn).

9391 Tracked Crane Trailer Modification - Bottom

Next attach a worm screw to the axle.


9391 Tracked Crane Trailer Modification - Worm Screw

Now take another axle and place it across the tracks to connect the back gear on each track to each other. On this axle, attach an 8 tooth gear which will be driven by the worm screw. You may need to firm up the axles with some other pieces.

9391 Tracked Crane Trailer Modification - Bottom

Finally, make a little trailer with a motor on it that can connect to the first axle. The only important thing here is that you make the connection the same height as the axle you’re connecting to on the crane. You may use a different motor than the one I used.

9391 Tracked Crane Trailer Modification - Trailer

Connect the trailer to the crane and you’re ready to roll (literally)!

9391 Tracked Crane Trailer Modification - Connecting 9391 Tracked Crane Trailer Modification - Connection