Ecentric variable gear train allows constant input speed and variable output speeds

Ecentric variable gear train allows constant input speed and variable output speeds

Not many in this day and age of automation; you could easily do this with a variable frequency drive. Back in the day before electronics, perhaps you would use this to speed up or slow down an assembly line, so assembly persons could do their task at a slow speed in front of them, and then the product would move at a faster speed between stations.

What are possible applications?

Thanks for the good content.

This is the type of stuff I like to see on this sub.

It's more variable in the sense that the output speed is sinusoidal.

Or maybe real high torque environments where you want to keep momentum in the motor driving this assembly but have a variable speed on the output.

I love gear and shit gifs.

I'm not so sure how the output would be variable.. that looks hard geared to me.

If you feel the gears might need someone to talk I urge them to call the Suicide Hotline at 800-273-8255 or visit

and if you give me a big enough lever and a place to stand, i can move the world

anything is possible with the right material properties, torque input, and overall scale

Serious question.

Would this gear assembly be capable of withstanding high torque though?

But not both at the same time.

Nah they'll be fine, they may be a little depressed for a period but they always come back around.

Don’t put words and shit in my mouth.

Just watching this gives me anxiety that the two outer gears will collide and strip.

"Remove "

With steel just to create a space elevator you would need a cylinder starting at 1 inch and at the other end having would be roughly 2x the size of the observable universe. So you would need an extremely good material to even try moving any amount of large planetary mass

I think this should be changed to "if you give me enough Russian and US nukes and a big enough button, I can move the world"

producing a sinusoidally varying output speed, I mean, idk - I like arrangements like this for visually appealing do-nothing machines

How did you come to the conclusion of nothing when he just said an interesting (admittedly outdated) use for it? I get that your comment was probably a joke but still

Oh well that's fucking cool as shit.

More details here.

If you mean this, that's more of an optical illusion from the perspective.

What would be a practical use for this type of gear?

I saw a similar mechanism on a packaging machine. Basically pulled the film forward quickly then slowed down to seal. The eccentricity was adjustable so it wasn't exactly like the one in th gif. This was on a new machine about 5 years ago so fairly modern application.

If you want something to go 50% speed half the time

Variable output speed is misleading. The output of this is a repeating sinusoidal speed output.

Unless it's at the same time

I had sweaty palms until I saw it was impossible

Would you be able to modulate the speed though, beyond modulating the input speed I mean? It looks like it's just a fixed cycle of high to low speed output.

I'm not sure what you're talking about. While it looks like they're speeding up and slowing down, the rotors are spinning at a constant rate.


Edit: don't listen to me, brain took a shit.

More so time varying rather than any arbitrary output

Hopefully they die or its not a very good cannon

Those rotors are spinning at a constant speed. Look only at one of the hubs and you'll see it never actually slows down.

The gold gear is actually the input so if you stop that gear the whole thing would stop.

I can move someone with a cannon, that is technically correct. Whether they die in the process... is another story

How is it useful? For impressing myself after I manage to make it out of Lego

mp4 link

This mp4 version is 96.51% smaller than the gif (218.84 KB vs 6.12 MB).  

Beep, I'm a bot. FAQ | author | source | v1.1.2

This mp4 version is 96.51% smaller than the gif (218.84 KB vs 6.12 MB).

Beep, I'm a bot. FAQ | author | source | v1.1.2

A cylinder that starts at one inch and gets wider? isn't that a truncated cone rather than a cylinder? Cylinder sides are supposed to stay parallel. That being said steel isn't a great material for most things. It's relatively cheap and suffices for most applications, that's all.

You should check out this guy’s YouTube channel if you haven’t already. Not only does he do gear-like videos, he does pretty much everything.

A mechanical representation of an elliptical orbit? Like an orrery sort of.


Edit: don't listen to me, brain took a shit.

How is it useful?

I'm pretty sure that's an optical illusion. If the blades really did speed up and slow down like that, the vibration from the varying torque be insane.

That seems... Uncalled for?

What? Constant outside speed and slower inside speed? Lifting torque? Not sure what you're trying to say, those rotors have a constant speed and are just geared together to prevent contact. Thee slow-down-speed-up effect is just an optical illusion.

In theory yes, but in practice you have to consider material properties.

Of course it could if it was overbuilt enough.

The real question is, would it be more cost effective to do it another way. There's a reason that belts and gearsets are much more common.

The one pictured isn’t adjustable either. It’s a fixed speed input with a variable speed output. If you plotted the output speed it would be sinusoidal.

it would be a fixed speed. no way to modulate unless you change the ratio between gears. older technologies that were used to modulate speed included belts/chains on variable diameter sheeves/sprokets.

edit: and by fixed speed I mean, it wouldn't change from it's current sinusoidal pattern.

collide and strip

( ͡° ͜ʖ ͡°)

Thing that keeps speeding up and slowing down