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drelectron

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I'm not sure if this would be more a geometry or algebra problem. I'm trying to figure out the process to find the answer to this problem.
I have a wheel that is 40 inches in diameter. On that wheel is a gear with 20 teeth. Each tooth actuates a magnetic sensor which in turn sends pulses to a controller. I'm trying to figure out how many pulses per second if the wheel is traveling 5, and 6, and 7 miles per hour and so on.
I'm sure there is an equation or string of equations that will give me the answer just not sure how to get there.
Please let me know if this needs to be in a different thread.
Thanks
 
I need to add that the teeth are on a gear mounted on the end of the axle. The gear is about 4 inches in diameter. The known value would be 20 pulses per revolution.
 
I'm not sure if this would be more a geometry or algebra problem. I'm trying to figure out the process to find the answer to this problem.
I have a wheel that is 40 inches in diameter. On that wheel is a gear with 20 teeth. Each tooth actuates a magnetic sensor which in turn sends pulses to a controller. I'm trying to figure out how many pulses per second if the wheel is traveling 5, and 6, and 7 miles per hour and so on.
I'm sure there is an equation or string of equations that will give me the answer just not sure how to get there.
Please let me know if this needs to be in a different thread.

The teeth are on a gear mounted on the end of the axle. The gear is about 4 inches in diameter.

At 5 mph the wheel will traverse 5(5280)/3600 = 7.333 feet/sec.

The wheel will rotate [7.333/3.333(3.14)]360 = 252º/sec.

With 20 teeth on the gear, 20(252)/360 = 14 pulses/sec. will be actuated.

My apologies for the misdirection.
 
At 5 mph the wheel will traverse 5(5280)/3600 = 7.333 feet/sec.

The wheel will rotate 7.333(360)/40 = 66º/sec.

With 20 teeth on the gear, 20(66)/360 = 3.666 pulses/sec. will be actuated.
Click to expand...

Thanks tchrwill. I Understand the first and third equation but could you please explain the second.
 
Yes Denis that's me as well. How about this.
A wheel with a circumference of 126" moving at 88" per second will make 1.43 revolutions per second (126/88= 1.43). The smaller gear will make the same number of revolutions which would mean there would be 28.6 pulses per second (20*1.43= 28.6).
What am I missing???
This is why I posted here I seem to get different answers depending on who I ask.
 
drelectron said:
Yes Denis that's me as well. How about this.
A wheel with a circumference of 126" moving at 88" per second will make 1.43 revolutions per second

It is moving less than "1 circumference" per second - thus it will make "less than 1" revolution per second.

(126/88= 1.43). The smaller gear will make the same number of revolutions which would mean there would be 28.6 pulses per second (20*1.43= 28.6).
What am I missing???
This is why I posted here I seem to get different answers depending on who I ask.
Click to expand...
 
Subhotosh Khan said:
It is moving less than "1 circumference" per second - thus it will make "less than 1" revolution per second.
Click to expand...

My mistake. So the formula would be 88/126= 0.698 revolutions per second?
Which would mean 0.698*20= 13.96 pulses per second.
 
Thanks for the help everyone. The trick was figuring out how many revs per second at any given MPH which gave me the pulse per second at that MPH.
The formulas you gave were exactly what I needed. Thanks again.
 
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