K'nex Forward/Reverse Transmission




About: Hello there! Welcome to our instructables page, where you will find k'nex stuff, more k'nex stuff, and maybe some computer stuff here and there. In case you're wondering why this is 'our' instructables p...

Hello there! Say you are in the middle of making an awesome new k'nex project, and you need a motor. You run to your junk drawer full of k'nex motors, and the only one left is your 12v motor. "Drat" you think, as you slump back to your building area, "I needed a newer style motor because I need to change the direction of the motor!" You pause, thinking of the predicament you are in. You think in horror of what would happen if you take apart one of your current builds, just so you can make this new one that you're not sure will even work, let alone be worth taking apart your precious build. You draw yourself up, and you say, "I will not let this happen!! I will search on... INSTRUCTABLES!!! Duh! Why didn't I think of it before!" You get out your phone and search on the instructables app. Lucky you, there's a search result that looks like what you want. You think again... is this build really worth building this contraption? You think again... Yes. It totally is! Thanks for coming along for the ride!

Now I know you might be thinking, "Hey, this isn't a new idea!" but I never saw instructions for one, so I decided to fill the void. Of course, this version is not the same as the others out there. It is meant to be small and easy to build, but it doesn't have the torque that a more complex one would have, so plan on modifying it to have it handle more difficult tasks.

Feel free to watch the video so you can see it in action, and then, if you want to build it, skip on to the step after that!

BirdCrazy made an instructable for his, more complex but probably better working, automatic transmission! Feel free to check that out. :)

If you want to know more, click here.

For an explanation of how it works (if the above link wasn't good enough), click here.

Questions? Feel free to send a comment or PM and I will get back to you ASAP!

Have fun!

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Step 1: The Video

Here's the video of the transmission! Feel free to watch it and then go on to the next step to build it!

Step 2: The Motor Section

Whoa, the first thing is the motor! We're off to a good start, I'd say. Okay, now let's build it! I'll catch up with you in the next step.

Step 3: The Gears Pt. 1

This is the first part of the mechanism that does the reversing! Hey, ya know, if the power pack on the motor had a switch there'd be no need to build this! That's not too encouraging...sorry

Step 4: The Gears Pt. 2

The second set of gears! And, yeah, despite what it looks like, this is necessary.

Step 5: Putting It All Together!

You know, it doesn't do you too much good to have something that's not put together, so that's what we'll do in this step! After you put it together, you only have one more really long step till you're done!

Step 6: The Switch

The part that changes the direction of the gears! I bet this is what you came here for!

Step 7: Done!

Great job! You finished your transmission! Just plug the motor in, flip the switch and watch the fan at the end spin in different directions! If it doesn't work all the time, just add more tires on the switch. It'll make it work better.

Oh, and if you want to, you can add a picture of your transmission in a comment and it'll be added to this step!

Thanks for building!

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    45 Discussions


    1 year ago

    Hey, I made this transmission and it works really well. I wanted to use this for my next ball machine in a lift. I have now come to a problem: I want the lift to switch it on it's own, but I can't seem to get it to work. Do you have any tips?

    1 reply

    Reply 1 year ago

    If your problem is that the gears aren't sliding easily enough, you can look at shadowman's flickr album for citadel which includes several pics of the transmission he used on his elevator lift.

    It might be easier for me to help you if you could tell me what type of lift you're working with, and what exactly is happening with what you have right now.

    I'll try to help you as much as I can! :-)


    2 years ago

    This is the same type of transmission that Shadowman uses for his twin elevator lift in his citadel machine? If so your a life saver! trying to make my own twin elevator lift like Shadowman's so hopefully this will help :)

    1 reply

    Reply 2 years ago

    Not the same, but similar. Glad it'll help! :)


    Reply 2 years ago

    No, sorry. I don't know if there is a simpler way to do it. Are you having trouble with anything in particular?