4 ms·

I don't understand why this is called an "amplifier" rather than simply "a clutch". The torque input is always the same; there is no "amplification" of the torq

by fernly 7y ago

I don't understand why this is called an "amplifier" rather than simply "a clutch". The torque input is always the same; there is no "amplification" of the torque. The tensioned rope or spring simply applies more or less of the torque to the output, by varying the friction on the drum.

detaro 7y ago
That's true of pretty much any amplifier: a small signal controls how much of a large "source" is available at the output. If I had to guess, it's a) to emphasize the "signal" part and b) to make a distinction for it being used for the proportional control?
bacon_waffle 7y ago
The output gets more torque, just like a capstan allows a person to amplify tension on a rope. Maybe this will explain better than the wikipedia page: https://www.youtube.com/watch?v=ailf7bz9H0o https://www.youtube.com/watch?v=ailf7bz9H0o edit: spelling, grammar...
- fernly 7y ago
  The reason I wondered, is that in years past I had serviced machines that used a "wrap spring clutch"[1] which I knew used the same principle. These are mentioned in passing in the Wpedia article on clutches[2] where it says they obey the "Capstan equation". That article[3] opens, > The capstan equation or belt friction equation, also known as Eytelwein's formula, relates the hold-force to the load-force if a flexible line is wound around a cylinder (a bollard, a winch or a capstan) So there's the generic idea, which can be viewed as a clutch or a bollard. The bollard is an "amplifier" in the same sense that a transistor is, where a small controlling voltage regulates a larger current flow. However the wrap spring clutch is on/off, not proportional, so is effectively a torque SWITCH. [1] https://www.warnerelectric.com/products/clutch-products/wrap-spring-clutches https://www.warnerelectric.com/products/clutch-products/wrap... [2] https://en.wikipedia.org/wiki/Clutch https://en.wikipedia.org/wiki/Clutch [3] https://en.wikipedia.org/wiki/Capstan_equation https://en.wikipedia.org/wiki/Capstan_equation
  - bacon_waffle 7y ago
    I think a better transistor analogy than a FET is a BJT, where both the amplified quantity and control signal are electrical current. The key difference between a clutch and torque amplifier is that, with a clutch, the output shaft power all comes from the input shaft. The torque amplifier's output shaft power mostly comes from the output drum, not the input shaft. The drums are constantly spinning, powered by some external source. https://www.youtube.com/watch?v=oNNkNc7mFJ4 https://www.youtube.com/watch?v=oNNkNc7mFJ4

by fernly 7y ago

detaro 7y ago

That's true of pretty much any amplifier: a small signal controls how much of a large "source" is available at the output. If I had to guess, it's a) to emphasize the "signal" part and b) to make a distinction for it being used for the proportional control?

bacon_waffle 7y ago

The output gets more torque, just like a capstan allows a person to amplify tension on a rope. Maybe this will explain better than the wikipedia page: https://www.youtube.com/watch?v=ailf7bz9H0o https://www.youtube.com/watch?v=ailf7bz9H0o edit: spelling, grammar...

fernly 7y ago
The reason I wondered, is that in years past I had serviced machines that used a "wrap spring clutch"[1] which I knew used the same principle. These are mentioned in passing in the Wpedia article on clutches[2] where it says they obey the "Capstan equation". That article[3] opens, > The capstan equation or belt friction equation, also known as Eytelwein's formula, relates the hold-force to the load-force if a flexible line is wound around a cylinder (a bollard, a winch or a capstan) So there's the generic idea, which can be viewed as a clutch or a bollard. The bollard is an "amplifier" in the same sense that a transistor is, where a small controlling voltage regulates a larger current flow. However the wrap spring clutch is on/off, not proportional, so is effectively a torque SWITCH. [1] https://www.warnerelectric.com/products/clutch-products/wrap-spring-clutches https://www.warnerelectric.com/products/clutch-products/wrap... [2] https://en.wikipedia.org/wiki/Clutch https://en.wikipedia.org/wiki/Clutch [3] https://en.wikipedia.org/wiki/Capstan_equation https://en.wikipedia.org/wiki/Capstan_equation
- bacon_waffle 7y ago
  I think a better transistor analogy than a FET is a BJT, where both the amplified quantity and control signal are electrical current. The key difference between a clutch and torque amplifier is that, with a clutch, the output shaft power all comes from the input shaft. The torque amplifier's output shaft power mostly comes from the output drum, not the input shaft. The drums are constantly spinning, powered by some external source. https://www.youtube.com/watch?v=oNNkNc7mFJ4 https://www.youtube.com/watch?v=oNNkNc7mFJ4