How to Quantify Energy on a Planet Gear?

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Discussion Overview

The discussion revolves around quantifying energy on the planet gear of a planetary gear set, focusing on the relationship between power, torque, and rotational speed (rpm). Participants explore theoretical and practical aspects of energy transfer within the gear system.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • John D suggests that all energy passing through a planetary gear set goes through the planet gear and can be quantified as power using torque and rpm.
  • Some participants question whether the focus should be on energy, torque, or loads, and seek clarification on the configuration of the gears (e.g., stationary ring or sun).
  • John D expresses a desire to quantify energy in terms of power, using the formula for horsepower based on torque and rpm.
  • Another participant asks for clarification on which components are the input and output to understand power flux.
  • Felmon38 proposes that energy should be calculated similarly to how it has been used in traditional gear systems, noting applications in power split situations like CVTs and hybrids.
  • There is a discussion about the relationships between power on different components of the gear set, with equations presented to illustrate these relationships.
  • John D raises a question about calculating torque based on power and rpm, seeking confirmation on his approach.
  • Participants discuss the need for known variables to solve for unknowns in the equations presented.
  • John D questions whether the power on the planet is equal to the power on the input, while also inquiring about the consistency of the ratio between different outputs.
  • Some participants express disagreement regarding the assumption that forces on the sun and ring are equal, indicating a need for further discussion.

Areas of Agreement / Disagreement

Participants express differing views on the relationships between power, torque, and the forces exerted on the components of the planetary gear set. There is no consensus on whether the forces on the sun and ring are equal, and the discussion remains unresolved regarding the implications of these relationships.

Contextual Notes

Limitations include assumptions about efficiency being ignored, and the dependency on specific configurations of the gear system that may not be universally applicable.

John D
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How can I quantify the energy on the planet gear of a planetary gear set?

My thoughts are:

All the energy that goes through a planetary gear set goes through the planet gear.

This energy can be quantified as power with torque and rpm relative to the axis of the planet gear. Thanks

John D
 
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John D said:
quantify the energy on the planet gear
"Gear(s)? Energy? Or torques/loads? Ring or sun stationary?
 
I was hoping for energy as in power. rpm x torque / 5252 = horse power.
As if it was a gear in a sequential gear train with torque rpm and horsepower. We all chase torque through a gear set using our rules but all the parts have power, energy. I thought.
thanks Bystander,
John D
 
Please John, can you tell me which are the input (power) and the output (load) wheel in order to know the power flux?
 

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flemon38
Because all the energy that goes through the planet set goes through the planet gear I would think the energy should be calculated the same. For many years we have been using this gear system with one member fixed. Lately we have been using it in power split situations as in CVTs and hybrid systems. You could use the example of power in on the planet carrier (arm) and out on the sun and ring. Even with the sun or ring stopped all power is always going through the planet gear.
Pc = Pp = Pr + Ps Power on the carrier equals the power on the planet equals power on the ring plus the sun.
Thanks for any help,
John D
 
felmon38 said:
Please John, can you tell me which are the input (power) and the output (load) wheel in order to know the power flux?
 
John D said:
Pc = Pp = Pr + Ps
I'm more inclined to write this as Pcarrier = nPplanet, where "n" is the number of planetaries.
 
Then John, if N is the torque:

Np.wp=Ns.ws+Nr.wr

and then:

Np/zp=Ns/zs+Nr./zr

Well, I don't know if this was what you were looking for.
 
Yes
I can calculate the rpm but how do I calculate the torque? Can I just use the power on the carrier and the rpm of the planet gear?
Bystander is right. For purposes of understanding I was using just one planet. The point is the total power is on the planet(s). Power*5252/rpm on the planet?
Thanks guys,
John D
 
  • #10
If we have these six variables: N's and w's, and the followings three independent equations:
Np.wp=Ns.ws+Nr.wr
ws=wp.zp/zs
wr=wp.zp/zr

then we need three knows variables in order to get the other three unknows
 
  • #11
The unknown appears to be the torque ( Np)
on the planet.
 
  • #12
A more realistic example could be, for instance the following: the two outputs could be two brakes so we will know their torques, Ns and Nr, the other date could be the characteristcs curve of the input motor: f(Np,wp)=0. So, from the first equation we could know the power of the motor and, from the characteristics curve Np and wp. From the other two equations, ws and wr
 
  • #13
Felmon38,
This is my question? Can I make the statements: The power on the planet is equal to the power on the input. The power on the planet can be expressed in torque and rpm. Ignoring efficiency. A side question would be; is the ratio between Ns and Nr always the same?
Thanks
 
  • #14
According with the equations I don't think so.
 
  • #15
I agree with you 100%.

If any of the advisors are watching I would expect we will get a disagreement.
There is an equal force on the ring and sun rule that gets in the way.
That is really what I would like to get a conversation started about.
Thanks felmon38,
John D
 
  • #16
Sorry John, I've spent this long time to understand your question (this is my fault not yours) well: there is not a rule at all telling that the force on the sun and on the ring are the same (I suppose we are talking about the forces the planet exerts on the ring and on the sun)
Bye
 

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