Finding Pitch Circle & Teeth for Amplitude Movement

In summary, the conversation discusses determining the pitch circle and number of teeth required for a mechanism to achieve a certain amplitude. The animation shows that the pinion originally had 12 teeth but 7 have been removed, and it may only work with an even number of teeth. The rack shifts a total distance of (pitch diameter x pi/2) or (rack tooth pitch x number of original pinion teeth/2) before returning. The mechanism's motion is described as violent and the rack has no mass. The conversation also includes a calculation for determining the travel distance, but there is confusion about the units.
  • #1
Jones1987
77
0
How would I work out the pitch circle and number of teeth required to move the mechanism a certain amplitude? Looked over 4-5 sources for pitch circle, but cannot make sense of it..
 
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  • #2
In the animation, if the pinion had all its teeth, there would be 12. 7 of those teeth have been removed (5 remaining). Not absolutely sure, but based on the model, it may only work with an even number of pinion teeth (prior to removal). 1 more than half of the original number of teeth likely have to be removed.
The rack shifts a total (from left to right say, before returning) of:
(pitch diameter) x (pi) / 2
or
(rack tooth pitch) x (number of original pinion teeth) / 2

This mechanism is really not very nice. Although it appears to be simple, its motion is quite violent. At the end of each stroke there is infinite acceleration. In the animation, it looks smooth, but that's only because the rack has no mass.
 
  • #3
tvavanasd said:
In the animation, if the pinion had all its teeth, there would be 12. 7 of those teeth have been removed (5 remaining). Not absolutely sure, but based on the model, it may only work with an even number of pinion teeth (prior to removal). 1 more than half of the original number of teeth likely have to be removed.
The rack shifts a total (from left to right say, before returning) of:
(pitch diameter) x (pi) / 2
or
(rack tooth pitch) x (number of original pinion teeth) / 2

This mechanism is really not very nice. Although it appears to be simple, its motion is quite violent. At the end of each stroke there is infinite acceleration. In the animation, it looks smooth, but that's only because the rack has no mass.

So if I had a pitch diameter of (0.1m) x (pi) / 2 = 0.1571 m/s? Is this correct?
 
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  • #4
Jones1987 said:
So if I had a pitch diameter of (0.1m) x (pi) / 2 = 0.1571 m/s? Is this correct?

I expect that travel should be 0.157 m.
Why are you suggesting the answer is in m/s?
 
  • #5
So does it mean the pitch circle is 0.157m or the distance the rack moves is 0.157m per revolution?
 

What is pitch circle and how is it related to amplitude movement?

The pitch circle is the theoretical circle that passes through the center of the gear and is used to calculate the gear ratio. In amplitude movement, the pitch circle is used to determine the distance traveled by the gear in one revolution.

How do you find the pitch circle for amplitude movement?

To find the pitch circle, you first need to measure the gear's diameter and divide it by the number of teeth. This will give you the pitch diameter. Then, using the formula Pitch Diameter = Number of Teeth/ Diametral Pitch, you can calculate the pitch circle.

What is the diametral pitch and why is it important in finding the pitch circle?

The diametral pitch is the number of teeth per inch of the gear's pitch diameter. It is important in finding the pitch circle because it is used in the formula to calculate the pitch circle. Different gears have different diametral pitches, so it is crucial to know the correct value for accurate calculations.

Can the pitch circle change during amplitude movement?

No, the pitch circle remains constant during amplitude movement. It is a theoretical concept and does not change as the gear rotates. However, the distance traveled by the gear in one revolution may change depending on the gear's position in the rotation.

How do you determine the number of teeth for amplitude movement?

The number of teeth for amplitude movement is determined by the gear's pitch diameter and the diametral pitch. By rearranging the formula for pitch diameter, you can calculate the number of teeth using the equation Number of Teeth = Pitch Diameter x Diametral Pitch.

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