Speed of shaft connected to gear

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    Gear Shaft Speed
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Discussion Overview

The discussion revolves around the relationship between the rotational speeds of shafts and gears, particularly focusing on how gear ratios affect these speeds. Participants explore concepts related to gear mechanics, including tangential velocity, gear ratios, and the implications of different gear sizes on rotational speed. The conversation includes both theoretical and practical aspects of gear operation.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant inquires whether shafts S1 and S2 rotate at the same rpm given a gear ratio of 1:2 and a motor speed of 1000rpm.
  • Another participant explains that tangential velocity is constant for both gears and that the gear ratio is proportional to the number of teeth and diameters, suggesting that for a gear ratio of 2:1, the rpm ratio would also be 2:1.
  • A different participant cautions about the correct interpretation of gear ratios, indicating that the stated ratio may not match the visual representation, which could lead to confusion regarding the relationship between input and output speeds.
  • Some participants express uncertainty about the relationship between gear ratios and rpm, with one suggesting that if the gear ratio is 2:1, then the rpm should be 1:2, indicating a potential misunderstanding of the concepts.
  • Another participant asserts that the shafts rotate at the same speed as their respective gears, which raises questions about the accuracy of previous claims regarding speed differences.
  • A participant presents a scenario involving specific shaft and gear diameters and asks for clarification on the resulting rpm of shaft S2, indicating a desire for practical application of the discussed concepts.
  • Several participants question the validity of the formula used by one member to relate rpm to speed, suggesting a need for clarity on the source and application of such formulas.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between gear ratios and rotational speeds, with some asserting that the shafts and gears rotate at the same speed while others question this assertion. The discussion remains unresolved regarding the correct interpretation of gear ratios and their implications for shaft speeds.

Contextual Notes

There are unresolved assumptions regarding the definitions of gear ratios and their application to the problem at hand. Participants also reference specific formulas and visual representations that may not be universally understood or agreed upon.

vidhyarthi
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Hi all,
I'm an EE student and i have least knowledge about working of gears.
I just want to know that if there are two shafts S1 and S2 of same diameter having two gears G1 and G2 mounted on them respectively. The gear ratio is 1:2. And the shaft S1 is connected to a motor which rotates at 1000rpm. Then
Will the shafts S1 and S2 rotate at same rpm. If yes then why people say that gears are used to increase or decrease speeds. If no how their speeds are differed?
 

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Keep these two things in mind about gears:

a) The tangential velocity is the same for both gears.
b) The number of teeth is proportional to the diameter of the gear.

As a consequence of a)

v = contant = R1 X angular speed 1 = R2 X angular speed 2

As a consequence of b)

gear ratio = ratio of teeth = ratio of diameters

So for a gear ratio of 2:1, the rpm ratio is also 2:1.
 
You need to be really careful how you write the gear ratios down, as what you've put doesn't match the drawing.

It's:
Input teeth:Output teeth

Gears can be visualised as two circles touching at a single point. With the respective diamaters being the ratio of the gears.

So you say the ratio is 2:1, but the picture shows a 1:2 ratio as the output gear is larger.
 
edgepflow said:
Keep these two things in mind about gears:

a) The tangential velocity is the same for both gears.
b) The number of teeth is proportional to the diameter of the gear.

As a consequence of a)

v = contant = R1 X angular speed 1 = R2 X angular speed 2

As a consequence of b)

gear ratio = ratio of teeth = ratio of diameters

So for a gear ratio of 2:1, the rpm ratio is also 2:1.
But actually rpm is inversely proportional to diameter of the rotating object then if gear ratio i.e. the ratio of diameters is 2:1 then i think the rpm is 1:2. Is it true?

xxChrisxx said:
You need to be really careful how you write the gear ratios down, as what you've put doesn't match the drawing.

It's:
Input teeth:Output teeth

Gears can be visualised as two circles touching at a single point. With the respective diamaters being the ratio of the gears.

So you say the ratio is 2:1, but the picture shows a 1:2 ratio as the output gear is larger.
Sorry i thought that gear ratio as the ratio of their speeds.

And what happens to the shaft rotation will they rotate at equal rpm?
 
vidhyarthi said:
But actually rpm is inversely proportional to diameter of the rotating object then if gear ratio i.e. the ratio of diameters is 2:1 then i think the rpm is 1:2. Is it true?

And what happens to the shaft rotation will they rotate at equal rpm?

That's true and you've just answered your next question.

The shafts rotate at the same speed as their respective gears.
 
Final question(i think i can understand fully with this)
Let the diameter of shaft S1=S2=19mm and S1 is a motor shaft rotating at 3000rpm.
from rpm=(kmphx1000)/(60xA) the speed of shaft is 10.744kmph
The gear G1 with diameter 150mm rotates at 380rpm and the gear G2 rotates at 190rpm(got from above formula)
then at what rpm the shaft S2 rotates 3000 or 190??
 
Why are you saying the gears are rotating at different speeds to the shafts? Also where on Earth did you find that formula?
 
xxChrisxx said:
Why are you saying the gears are rotating at different speeds to the shafts? Also where on Earth did you find that formula?
I'm saying that because gear has more diameter than shaft and from your question can i understand that shaft just deliver power to any thing connected to it i.e same torque and same speed.
And coming to the formula i got it here http://wiki.answers.com/Q/What_is_the_formula_for_converting_rpm_to_kph
 

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