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.
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.
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.
With LEGO power functions and a few gears, it’s fairly easy to make a four-leg walker.
For this walker, I used the battery box as the body, and made a head out of a medium motor. I connected a worm screw to the motor pointing towards the ground.
I built a basic frame going down kind of parallel to the motor, and then going at a right angle parallel to the battery box. Next to the worm screw, I placed a 24-tooth gear. This could be swapped out for a different gear if you want to experiment with power and speed.
The gear that is adjacent to the worm screw is on an axel that has two other gears on it. These gears are on the outside of the frame. These have pins in one of the off-center holes, that also connect to the “legs” of the walker. The legs of the walker are further connected to a small piece (a black three-length piece in the pictures) that can swivel as the legs move up and down. The interaction between this swivel and the rotating gear is what causes the legs to move up and down. Changing the distance between these pieces and/or the length of each or size of the gear will change how the legs move.
I made all four legs similar, so that they all rotated the same distance.
Another important thing to remember with the legs, is that the timing needs to be calibrated so that the legs move correctly in relation to each other. You can look at the video for a better picture of this — it will likely take some experimentation.
In order to drive the rear legs, I placed gears all the way along the length of the frame.
I used an odd number of gears (five) so that the front gears and the back gears rotate the same direction.
Finally, note the “feet” at the bottom. The walker should be able to balance on two feet at a time. That way two feet can hold it steady while the other two fit lift up and advance forward. The feet on this walker are wide so that the center of gravity falls somewhere between the two feet that are on the ground (front right and rear left, or front left and rear right).
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).
Next attach a worm screw to the axle.
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.
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.
Connect the trailer to the crane and you’re ready to roll (literally)!