Scorpio

Using a Differential to Power Two Independent Sections

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I rarely post but I check this site and other Lego Technic sites like Sariel's and GBC websites and I am stumped on a way to mechanically make this work. 

I am trying to use the Lego differential in a way that I have not seen others use it, at least in the searches I have performed. 

Limitations:

  • Input motor needs to constantly run
  • I would like to do this purely mechanically. Cannot use Mindstorms. Would prefer to not use switches unless necessary. 

Problem:

I am trying to use a Lego differential to power two separate sections of my build. I don't have access to easy pictures so please see the simple diagram below. I have power on one axle and the two other axles will drive separate sections. I would like Section A to run constantly (or could potentially stop when Section B is running). Section B is currently being held up by a ratchet that completely stops the gear from turning until it is released, When released, Section B will run one full revolution then stop again until the ratchet is released again. The ratchet release is not on a pattern. It can be released 20 times in a minute then not released again for an hour.

The issue that I am running into is that Section B currently has a higher load than Section A; therefore, when Section B's ratchet is released for the gear to run one full revolution, the load is heavier than Section A and Section B does not move.

Solutions I can think of:

  • Make the load on Section A larger than that on Section B so that when the ratchet releases, Section B will be easier to move than Section A and the differential will transfer power to Section B and it will work. I would rather not arbitrarily add to Section A's load unless that is the only way.
  • Otherwise, maybe engage a ratchet on Section A to stop that section completely but then disengage exactly after Section B has completed one revolution and at the same time, stop Section B from running. I would think this is more difficult since at least one Section will need to run at a time so the motor and differential don't break but I could be wrong. 

I'm currently using the 28-tooth differential with 3 - 12-tooth bevel gears (BL: 62821b) inside a 5x7 technic frame 

Simple diagram:

                                Section B

                         ----------|----------

Section A    -----|    Differential   |-----  Input Motor

Any help is appreciated. Thanks. 

Edited by Scorpio

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You should watch Technic Brick Power from YouTube. He has a few videos on using the differential for different tasks.. here is a link to his YouTube site. Check out his other experiments. This guy is good!! 

 

Edited by sirslayer

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It sounds like you actually want a clutch mechanism controlling section B, and not a differential. This is a system used in GBC modules fairly often.

In this video, you can see what I'm talking about. I think having a clutch over a differential would work a lot better for your purposes. If you're wondering what's the clutch, watch the little wheel that is used to grab the axles, and how it moves.

This video shows an even better clutch.

Edited by Saberwing40k

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6 hours ago, Saberwing40k said:

In this video, you can see what I'm talking about. I think having a clutch over a differential would work a lot better for your purposes. If you're wondering what's the clutch, watch the little wheel that is used to grab the axles, and how it moves.

This video shows an even better clutch.

This is exactly what I’m looking for. Thank you! 

I am trying to figure out how to switch sections on and off using only a GBC ball and this video makes it look like it should be possible. 

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