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Can anyone explain movement 38? [1] Two identical gears start moving at the same speed. Suddenly, one gear slows down, then lurches forward at a much faster sp

Can anyone explain movement 38? [1] Two identical gears start moving at the same speed. Suddenly, one gear slows down, then lurches forward at a much faster speed, and then returns to its starting speed. While the other, identically shaped gear, spins at a constant speed the whole time. [1] http://507movements.com/mm_038.html http://507movements.com/mm_038.html

balfirevic 7y ago
Only relative speed will be determined by the geometry (these gears, in effect, change the gear ratio throughout one revolution). In this animation, the author decided that the left gear is driving the right one (while itself, presumably, being driven by a motor at constant speed or something similar).
nachexnachex 7y ago
The left wheel rotates at fixed speed, it's the source of the movement (connected to the source of power). The right wheel rotates according to the relative radii between them, the constant speed of the left wheel dictating its speed.
lowboy 7y ago
Red is being driven by the axle at a constant rate, blue is being driven by the teeth of red
Nition 7y ago
They are indeed identical but they're spinning in opposite directions, which in effect means one is flipped (going small->big instead of big->small). I believe that's how they can behave differently.
Zenst 7y ago
Gear ratios. Think bicycle. By adjusting the distance from the center the ratio can be changed. Closer to the center on the driving cog (the left red one) will reduce rotation ratio and further away, will increase the rotation.
Parcle 7y ago
I imagine the red gear is the one backed with a motor rotating at a constant speed. Which would explain why it never slows down or speeds up. The blue one is being entirely driven by the red. It slows down because moving 2 notches at a greater diameter requires less rotation than moving 2 notches at a lesser diameter. It then speeds up because moving 3 notches at a lesser diameter requires more rotation than moving 3 at a greater diameter.
dsheth 7y ago
the gear on the left is the driving gear, moving at a constant rate. When the gear on the left allows the gear on the right to fit closer to the center of that left gear, the gear on the right moves more slowly. Similarly, when the gear on the right fits farther from the center of the left gear, the gear on the right moves more quickly
scoyle 7y ago
It appears that the left gear is the driving gear and the right is the driven. This means that the angular speed of the right gear is the ratio of the left radius to the right radius (speed_right = speed_left*radius_left/radius_right). Because the angular speed of the left gear is constant the only change to the angular speed of the right will come from the changing radius ratio of the two gears. This behavior can be seen a bit more clearly with nautilus gears that have constantly changing radii.
Rapzid 7y ago
Others have talked to the changing ratio, however I think the possible implications(use cases) of this are also interesting. I'm imagining making room for something, also rotating at a the same speed, to slip into place by arresting the second gears speed before catching it up. I'd love to get into watch building which likely utilizes a lot of these tricky movements.
- pawelk 7y ago
  I have recently became interested with the inner workings of watches and found this 1949 video to be a perfect explanation of the underlying concept of a watch movement mechanism: https://www.youtube.com/watch?v=WYBvt9kA3bE https://www.youtube.com/watch?v=WYBvt9kA3bE
  - Rapzid 7y ago
    That was a great video. Tourbillon from scratch; one day.
lqet 7y ago
As others have mentioned, the movements make perfect sense intuitively as soon as you realize that the red gear is rotating constantly (driven by a motor), and the blue gear is spinning freely.
- duiker101 7y ago
  It does indeed thinking about it like that. But since the gears would be bumping into each other rather than just pushing each other would that cause them to deteriorate faster?
  - soulofmischief 7y ago
    Sloped / beveled edges, a strong material, and a ratcheting mechanism should keep gear lifetime about the same if I had to guess.
    - mdesq 7y ago
      Also lubricated with grease or even bathed in oil which serves as a cushion.
  - skykooler 7y ago
    Gears are always bumping into each other, one tooth at a time. In practice, the friction of the teeth sliding on each other causes much more wear than the impacts.
    - taejo 7y ago
      In a properly constructed (shaped) gear, the teeth should roll against each other rather than sliding (i.e. the velocities of the contact points are the same).

balfirevic 7y ago

Only relative speed will be determined by the geometry (these gears, in effect, change the gear ratio throughout one revolution). In this animation, the author decided that the left gear is driving the right one (while itself, presumably, being driven by a motor at constant speed or something similar).

nachexnachex 7y ago

The left wheel rotates at fixed speed, it's the source of the movement (connected to the source of power). The right wheel rotates according to the relative radii between them, the constant speed of the left wheel dictating its speed.

lowboy 7y ago

Red is being driven by the axle at a constant rate, blue is being driven by the teeth of red

Nition 7y ago

They are indeed identical but they're spinning in opposite directions, which in effect means one is flipped (going small->big instead of big->small). I believe that's how they can behave differently.

Zenst 7y ago

Gear ratios. Think bicycle. By adjusting the distance from the center the ratio can be changed. Closer to the center on the driving cog (the left red one) will reduce rotation ratio and further away, will increase the rotation.

Parcle 7y ago

I imagine the red gear is the one backed with a motor rotating at a constant speed. Which would explain why it never slows down or speeds up. The blue one is being entirely driven by the red. It slows down because moving 2 notches at a greater diameter requires less rotation than moving 2 notches at a lesser diameter. It then speeds up because moving 3 notches at a lesser diameter requires more rotation than moving 3 at a greater diameter.

dsheth 7y ago

the gear on the left is the driving gear, moving at a constant rate. When the gear on the left allows the gear on the right to fit closer to the center of that left gear, the gear on the right moves more slowly. Similarly, when the gear on the right fits farther from the center of the left gear, the gear on the right moves more quickly

scoyle 7y ago

It appears that the left gear is the driving gear and the right is the driven. This means that the angular speed of the right gear is the ratio of the left radius to the right radius (speed_right = speed_left*radius_left/radius_right). Because the angular speed of the left gear is constant the only change to the angular speed of the right will come from the changing radius ratio of the two gears. This behavior can be seen a bit more clearly with nautilus gears that have constantly changing radii.

Rapzid 7y ago

Others have talked to the changing ratio, however I think the possible implications(use cases) of this are also interesting. I'm imagining making room for something, also rotating at a the same speed, to slip into place by arresting the second gears speed before catching it up. I'd love to get into watch building which likely utilizes a lot of these tricky movements.

pawelk 7y ago
I have recently became interested with the inner workings of watches and found this 1949 video to be a perfect explanation of the underlying concept of a watch movement mechanism: https://www.youtube.com/watch?v=WYBvt9kA3bE https://www.youtube.com/watch?v=WYBvt9kA3bE
- Rapzid 7y ago
  That was a great video. Tourbillon from scratch; one day.

lqet 7y ago

As others have mentioned, the movements make perfect sense intuitively as soon as you realize that the red gear is rotating constantly (driven by a motor), and the blue gear is spinning freely.

duiker101 7y ago
It does indeed thinking about it like that. But since the gears would be bumping into each other rather than just pushing each other would that cause them to deteriorate faster?
- soulofmischief 7y ago
  Sloped / beveled edges, a strong material, and a ratcheting mechanism should keep gear lifetime about the same if I had to guess.
  - mdesq 7y ago
    Also lubricated with grease or even bathed in oil which serves as a cushion.
- skykooler 7y ago
  Gears are always bumping into each other, one tooth at a time. In practice, the friction of the teeth sliding on each other causes much more wear than the impacts.
  - taejo 7y ago
    In a properly constructed (shaped) gear, the teeth should roll against each other rather than sliding (i.e. the velocities of the contact points are the same).