As mentioned in Project Alpha, I wanted to create a linear gearbox for comparison. Since my only Power Function motor is used in Project Alpha, I had to use my NXT set for this one.
A linear gearbox is different from the usual one in the way it functions. Instead of having multiple movable "clutches" to engage/disengage gears, in the linear gearbox, the shaft that the gears are mounted on moves such that different sets of gears engage/disengage. "Clutches" are absent, so there is no need to hunt for such exotic Lego parts. A linear gearbox relies on the fact that different gears, when mounted in certain sets, have equal distances between their mounting axles. When constructing such a gearbox, it is important to keep in mind the spacings between each gear on each axle.
Mine have four forward gears, achieved by pairing four sets of gears:
- 24-tooth spur with 8-tooth spur
- 20-tooth dual-bevel with 12-tooth dual-bevel
- 16-tooth spur with 16-tooth spur
- 12-tooth dual-bevel with 20-tooth dual-bevel
Input is by a NXT Motor, output is made more visible using a Lego piece. I programmed my NXT such that the motor would turn five rotations then stop and wait for a bump on the touch sensor, after which the loop repeats and the motor turns. After each set of rotations I would switch gear, then press the touch sensor, because if the input is continuous I am afraid that my gears would grind too much and get damaged. Although, the gear grinding is not an actual issue, as shown at the end of the video when I switched through all four gears while the motor is still running.
Oh, and, for decoration, I added a useless NXT motor beside the NXT. It's absolutely extra and I don't know why I put it there (probably because I'm more used to a NXT running with two motors, like in a robot).
In the pictures, wires have been mostly removed for clarity.
Please pardon the color randomness, I don't have much bricks to spare.
The results are good; this gearbox is much better than the first one. It can handle stresses very well and the gears hardly crack or grind. Friction is not a problem in this one. The only disadvantage is it's size, despite having fewer gears, it is larger than the first gearbox.
Here's the video:
The results are good; this gearbox is much better than the first one. It can handle stresses very well and the gears hardly crack or grind. Friction is not a problem in this one. The only disadvantage is it's size, despite having fewer gears, it is larger than the first gearbox.
Here's the video:
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