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Hi There,

I developed a motorized gearbox that does not need a dedicated motor for shifting gears. Instead it uses the speed difference of two driving motors to shift gears. This way I benefit from the combined power of two motors for propulsion and an autmoated gearbox. I then still have the third motor for other purposes, like steering.

Anyway, here are two video's, the first showing the gearbox in action, the second explains how it works.





More details on my blog.

Hey, that's pretty cool!

BTW, embedded YT videos don't work right now, so I've posted the links below:

Video 1
Video 2

Very cool. Thank you for showing some of the details in the video. The design is very slick, i.e., well done. I also like that it is modular. The modularity makes it a good teaching tool. And makes it easier to see the effects of the transmission and study gear efficiency.

I am subscribed to your blog and see the first 5 paragraphs of your article in my RSS reader, but when i go to your blog, the last post is "The ultrasonic sensor" from September 12, 2012.

The YouTube vidoes embed fine for me. FireFox 16.0.1 with flashblock on Ubuntu 12.04.

Very nice idea, as it prevents the other motor to be dead weight most of the time.
How well does it perform in practice? Since there are two motors, quite a bit of force will go through it, can the Lego transmission parts keep that in check? How fast can you switch gearing?
I would like to try it out, but I guess I have to finish my 6x4 first...

(The YouTube videos didn't work for me, it embedded the flash version and I don't have flash installed.)

I fixed the problem with my blog. The article is now available under this link.

I haven't tested the gearbox under load. It is build to demonstrate the concept, hence its modularity and ability to take apart and reassemble in a few seconds. It was not build for strength, so I think it will fail under load.

Gear shifting is quite fast. It is merely a matter of choice how fast you want it to be. This can be adjusted in hardware, by changing the gear train to the differentail, or in software, by increasing the speed difference between the motors. The downside with fast gear change is less accuracy and more sensitivity to unintended speed differences. But even with the current setup it can be made faster than you see in the video.

Hi Aswin,
That is pretty cool. I love the way you can split it apart so you can show how it works, very nice.

So do you have any plans for how you are going to use it?

Andy
PS oh and the embedded videos (on this site) don't work for me with Chrome.

gloomyandy wrote: So do you have any plans for how you are going to use it?

Andy

No I don't. Usually I make free wondering robots. They use at least two motors for propulsion to give them extra speed. But I don't think a gearbox is a good idea with electric motors. Better to invest in a sturdy gear train with some acceleration (1-2).
I was tempted to use it for steering though, that would free up the third motor in some models. But there is too much slack in the system to allow for accurate steering.

I hope someone else sees some use in it.

I haven't had much success with gearboxes to speed up my models, the only thing I have succeeded in is smashing gears ; )

But I do think they could have an use when gearing down. For example if your normal gear is good enough to drive on a flat floor, but too high for driving up at slopes, you could switch to an lower gearing to get that extra power needed. Could be useful if you need good performance both indoor and outdoor.

Hello Aswin,
absolutely amazing mechanical engineering!
Great that you also made the educational video.

charis