A simple question (but I don't knwo the answer)

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Discussion Overview

The discussion revolves around calculating the circumference of a second wheel (B) that is intended to spin five times for each revolution of a first wheel (A) with a known circumference. Participants explore the implications of using different circumferences and gear sizes in their calculations.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant asks for the circumference of wheel B based on the requirement that it spins five times for each revolution of wheel A, which has a circumference of 78 inches.
  • Another participant suggests a calculation involving division and later corrects it to multiplication, indicating uncertainty about the correct approach.
  • A participant introduces a complication regarding the use of a gear with a different circumference (75 inches) and questions which circumference should be used for the calculation.
  • Some participants assert that the circumference of the gear is the relevant measurement for the calculation, while others emphasize the importance of gear tooth counts over circumference in gear systems.
  • There is a discussion about whether to divide the sizes of the gears or use another method, with some suggesting that the approach depends on the desired outcome.

Areas of Agreement / Disagreement

Participants express differing views on which circumference to use in calculations and whether to focus on gear tooth counts or circumferences. The discussion remains unresolved regarding the best approach to calculate the required size of wheel B.

Contextual Notes

Participants mention the importance of understanding gear mechanics and the distinction between tire and gear calculations, but there are no settled definitions or assumptions about the relationships between the different measurements.

NYC2LA
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I have a bicycle wheel (A) with a circumference of 78 inches.

I want to attach a wheel (B) to it that will spin FIVE times (for each of the ONE revolutions of A).

What is the circumference of wheel B?

(I honestly do not know how to calculate wheel/circle rotation)

thank you.
 
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I would guess at 78 / .20

Is this correct?
 
Ooops...I meant 78 x .20

And to further my problem:

the circumference of the wheel (with tire on it) is 78" but I have a gear that is 75" in circumference which is attached at the hub. If I need a wheel to spin five times more for every revolution of the tire do I use the 78" or the 75" in the calculation to find the right size gear?

TIA
 
78 x .20 will do it unless you are connecting the second wheel to the gear and not the wheel.
 
okay...so my assumption...

was correct, in that it's the circumference of the circle (gear) is the source for the calculation.
A gear half the size of another gear would spin twice the rotations, on fifth the size, five time, etc.
 
NYC2LA said:
was correct, in that it's the circumference of the circle (gear) is the source for the calculation.
A gear half the size of another gear would spin twice the rotations, on fifth the size, five time, etc.
With gears it is better to use gear tooth counts rather than diameter (or circumference).
Gears mesh so the effective circumference is not on the surface unlike a bicycle tire.
 
excellent!

yes...i am using the count of teeth...(chain driven) is there a formula? or just divide the smaller into the bigger?
 
Which way depends on the answer you want.
But, divide one by the other is pretty much it.
 
ok

cool beans...
thanx

eom
 

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