Is This a Power Sharing Mechanism?

If I understand correctly the image below averages the total power output of the 2 sides? Ex one side has more load so the motors then share the total load. But each side can go different directions?
I would be using this on my rollers since one is under considerably less stress than the other and I’d like to relieve some of the stress off the motor but they also need to go different directions independently from each other. I assume the 84 tooth gear is the output?

I don’t think the friction losses are worth making a differential for your rollers. but out of curiosity, which 2 rollers are you planning on linking that you want to be able to independently control? the launcher and indexer?


I have 2 sets of rollers one in the back and one if the front. One is going at 1000 rpm and then a 1777 flywheel. The problem is that this set of rollers accelerates quite slow. The other set is just running on 600 rpm so it’s under little load. Also has an ejector if your wondering.

do the 2 sets ever need to spin independently? because if not, you can just link it directly.

another problem with the differential is that if you try to move both at the same time, each will be running with half the speed that they would be if you were only powering one.

The 2 sets need to spin independently so I can’t directly link.
Also what do you mean by each will be running at half speed when they are both moving?

The way a diffy works is this:

if both motors spin clockwise at 100% speed, output 1 will spin clockwise at 100% speed. if both motors spin counterclockwise at 100% speed, output 1 will spin counterclockwise at 100% speed.

if one motor spins clockwise at 100% speed and the other spins counterclockwise at 100% speed, then output 2 will spin clockwise at 100% speed. if one motors spins counterclockwise at 100% speed and the other spins clockwise at 100% speed, then output 2 will spin counterclockwise at 100% speed.

now this is all great if you never want to spin both output 1 and 2 at the same time, but I’m guessing you do.

in order to do that, you need to do stuff like this:

if motor 1 spins at 100% speed clockwise and motor 2 spins at 50% speed clockwise then output 1 will spin clockwise at 50% speed and output 2 will spin clockwise at 50% speed.

so you see, there is no way to have both outputs spin at 100% speed when using a differential (I think, if anyone smarter knows a way feel free to say it)


I would recommend using some sort of ratchet device instead of a differential. Something like this allows for independent control and also shared power with significantly less friction.


The ratchet idea seems plausible since I really only roll the flywheel set one direction which is up but the other set needs to spin multiple directions. But a ratchet there wouldn’t help since I have to spin it the same direction anyways and I also couldn’t slow it down.
Then the differential idea is fundamentally flawed but if I use both ideas it could work.

Motor 1 will be the front set and Motor 2 will be for the back set and same for outputs.

For spinning the back set, directly attach to the motor 2.

Then use the power sharing mechanism and connect both motors to it.

Then ratchet both outputs together so either can power the front set.

This would allow for you to control the back while giving some of the power to the front and then the motor 1 can then control the direction the front goes while motor 2 control which output it uses but this doesn’t matter since you ratchet the 2 outputs together. This should allow for you to give extra power to the front while still controlling the 2 directions independently.

This is very achievable with a ratchet. On our bot the ejector roller (the top back roller) is directly powered by a motor2, motor 1 powers the remainder of the rollers. The ratchet is connecting the two systems. When the ejector motor spins counterclockwise the ratchet slips and motor 2 no longer powers the front rollers. When motor 2 spins clockwise the ratchet engages and motor 1 and 2 power the front rollers, however only motor 2 is powering the back roller. If you wanted to spin the front rollers backward it would also power the back roller backwards as well.
I’m not sure that you will need to give that extra power to the front roller. Keep in mind that when you are ejecting the system switches to one motor power for a fraction of a second. This is not long enough to negatively impact the speed of the front rollers and if you do not have enough torque you may need to adjust the friction, tensions on your rollers. The amount of friction that your proposed system would add would negate any benefits that the motor sharing would provide.


you are correct. you’d be violating some pretty fundamental laws of physics of you had more output power than input


I mean it might be possible to run both outputs of a diffy at 100% speed but 50% torque. that doesn’t create power out of thin air, but I’m not sure I know of any differential that does this.

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yeah i was gonna mention that but i can’t think of anything that does it with the same input/output schemes. i’m sure there’s some fancy mechanism used industrially that can do that sort of thing but it’s probably way out of the scope of vex

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That just means connecting both outputs to the same motor(s) in parallel, lol.

But if you want variable speeds with max power, then each output needs to have one of these:


well, no, not if you want the directions of each output to be independent.


Anyone know what the outputs are when you spin the motors certain in each combination? Ie Both motors spin clockwise which outputs spins and what direction? I know Xenon27 said something about this but I think this is just him explaining the basic idea.

i believe it does not matter