Published April 2023
Planetary gearsets are efficient arrangements of gears that achieve a high gear ratio in a small space. Planet gears are held between a sun gear and a ring gear. A carrier (not shown) helps keep the planet gears in place, and provides a convenient attachment point for an output.The relative difference in speeds between the sun and the ring determine how quickly the planets rotate about the sun.
Try changing the speed of the sun gear to see how the planets react, and scroll down when you're ready to see more. On small screens, scroll up to see the controls, and down to hide them.
The number of teeth on each gear determine the relative sizes of the gears, and therefore the ratio.
Try changing the number of teeth on the sun and planet to see how the gears react.
Every time the sun gear rotates 3.66 times relative to the ring gear, the carrier rotates once.
Note that the number of teeth on the ring depends on the number of teeth on the sun and planet - it has to be big enough to fit the other gears!
You can also change the number of planets. Evenly spaced gears will only mesh (fit together) if the total number of teeth in the ring and the sun is divisible by the number of planets. A number that would mesh is shown below.
If gears that touch each other are coprime (not divisible by the same number), the gears will wear less, because every tooth will contact every tooth on the other gear, instead of contacting the same teeth over and over. If the number of teeth are not coprime, the tooth numbers are highlighted in blue.
Try changing the number of teeth on the sun and planet to see how the gears react.
Every time the sun gear rotates 3.66 times relative to the ring gear, the carrier rotates once.
Note that the number of teeth on the ring depends on the number of teeth on the sun and planet - it has to be big enough to fit the other gears!
You can also change the number of planets. Evenly spaced gears will only mesh (fit together) if the total number of teeth in the ring and the sun is divisible by the number of planets. A number that would mesh is shown below.
If gears that touch each other are coprime (not divisible by the same number), the gears will wear less, because every tooth will contact every tooth on the other gear, instead of contacting the same teeth over and over. If the number of teeth are not coprime, the tooth numbers are highlighted in blue.
Attaching a second planetary gearset to the first allows for very high gear ratios.
Here, the first carrier is attached to the second sun, so the reduction happens twice.
Now, for every 10 rotations of the first sun gear, the second stage's carrier rotates once.
Try changing the number of teeth and see what kind of ratios you can acheive. You can also click and drag on the gears to rotate the view to get a better look.
Here, the first carrier is attached to the second sun, so the reduction happens twice.
Now, for every 10 rotations of the first sun gear, the second stage's carrier rotates once.
Try changing the number of teeth and see what kind of ratios you can acheive. You can also click and drag on the gears to rotate the view to get a better look.
Instead of connecting to just one gear in the second set, what if you connect to two?
If the first and second sun, and the first and second carrier were connected, they'd have the same speed.
If the first and second ring had the same number of teeth, they'd have the same speed too.
If the first and second sun, and the first and second carrier were connected, they'd have the same speed.
If the first and second ring had the same number of teeth, they'd have the same speed too.
But if they have a similar number of teeth, they'd move at similar speeds.
If the first ring is still, the second ring will be almost still, aka moving very slow.
If you use the first sun as an input, and the second ring as an ouput, you'd have to turn the first sun 100 times for the ring to turn once.
Play with the sliders and see if you can achieve a ratio of over 1:10,000.
Hint: try to maximize number of teeth while making sun₁*planet₂ and sun₂*planet₁ close, but not equal.
If the first ring is still, the second ring will be almost still, aka moving very slow.
If you use the first sun as an input, and the second ring as an ouput, you'd have to turn the first sun 100 times for the ring to turn once.
Play with the sliders and see if you can achieve a ratio of over 1:10,000.
Hint: try to maximize number of teeth while making sun₁*planet₂ and sun₂*planet₁ close, but not equal.
In some configurations, the output gear rotates in the opposite direction of the input gear.
This can be used to your advantage if your power source is spinning in the opposite direction of what you want your final output to be.
This can be used to your advantage if your power source is spinning in the opposite direction of what you want your final output to be.
One-way bearings are bearings that freely rotate in one direction, and lock in the other direction. Placing one-way bearings between different components in the gearbox allows the inputs and outputs to be changed dynamically depending on which way they are spinning.
This can be used to get two different output gear ratios with an electric motor that can reverse direction, without any need for an external transmission.
For example, we can switch between a singly-connected configuration with a 3:1 ratio, and a doubly connected configuration with a -300:1 ratio, achieving an output that's always spinning in the same direction with either high speed or high torque.
This is the main concept behind this patent.
This can be used to get two different output gear ratios with an electric motor that can reverse direction, without any need for an external transmission.
For example, we can switch between a singly-connected configuration with a 3:1 ratio, and a doubly connected configuration with a -300:1 ratio, achieving an output that's always spinning in the same direction with either high speed or high torque.
This is the main concept behind this patent.
Special thanks to the co-inventors on the above patent, Max Wood-Lee, Chuck Brunner, and Steven Toddes.
Major thanks to Bartosz Ciechanowski for the inspiration.
Thanks to TutorialsPoint, as this all started with this rotating cube.
Major thanks to Bartosz Ciechanowski for the inspiration.
Thanks to TutorialsPoint, as this all started with this rotating cube.