1st grade math question

blueboy · Sep 6, 2019

What is the gear ratio?
Driver gear is 34 teeth the driven gear is 32 teeth. So is it 1.0625:1 or .941:1

Gordon Heaton · Sep 6, 2019

I learned it as the revolutions of the driving gear / driven gear. So to me it is .941:1

The example that comes to mind is the rear-end ratio on a motor vehicle, 4.11:1 etc.

TGTool · Sep 6, 2019

I have trouble remembering which way things go too, so usually resort to some sort of logical cross check to clarify. In this case, I see that a larger gear is driving a smaller on, meaning that it will be speeding up the output. So having two possible numbers to choose from, I'd take the larger one, 1.0625.

BoxcarPete · Sep 6, 2019

I'm going to side with Gordon on this one. Don't forget that the colon in any ratio represents the word "to" so we can correlate an input to an output.

So, .941 rotations in to 1 rotation out makes the most sense to me.

johnoder · Sep 6, 2019

Or "over drive "

Ever notice the vehicle transmissions with "over drive" express that ratio as always being less than one

jz79 · Sep 6, 2019

the work that needs to be done is usually represented by the "1", from there you calculate how much work you need to do at the input side to get the result of "1" at the output, in this case - 16/17 of the 1, or 0.941:1

michiganbuck · Sep 6, 2019

How To Calculate Gear Ratio - HBReducer

Re: Divide the driven gear teeth by the drive gear teeth.

blueboy · Sep 6, 2019

Divided by, goes into, always gets twisted around in my dyslexic mind.

johnoder said:
Or "over drive " Ever notice the vehicle transmissions with "over drive" express that ratio as always being less than one

That’s what I was thinking.
Thanks guys!

boslab · Sep 6, 2019

michiganbuck said:
How To Calculate Gear Ratio - HBReducer

As correctly pointed out driven / driver (DRIVEN MAD BY THE DRIVER)I did a lot of that in college, make up little rhymes as we weren’t allowed to look up formulas in exams so you got good at remembering them, on the down side I remember just about every formula and can’t remember what day it is
Mark

bloomautomatic · Sep 6, 2019

Is the tooth count metric or imperial?

blueboy · Sep 6, 2019

bloomautomatic said:
Is the tooth count metric or imperial?

It's Romulan!

mhajicek · Sep 6, 2019

It's Canadian.

gbent · Sep 6, 2019

Gordon Heaton said:
I learned it as the revolutions of the driving gear / driven gear. So to me it is .941:1

The example that comes to mind is the rear-end ratio on a motor vehicle, 4.11:1 etc.

I disagree, it is driven over driver. In your example, a rear end has a large ring gear (driven), and a small pinion (driver). So say you have 4.11's, 37 teeth on the ring divided by 9 teeth on the pinion.

I'd call the OP's a .941:1, or for clarification, call it a .941:1 overdrive gear set.

Joe Gwinn · Sep 6, 2019

English isn't quite precise enough to depend on people all getting the same answer. I would always say which gear turns faster.

Likewise with ratios in general. I always say something like ""the xx, computed as aa divided by bb".

Gordon Heaton · Sep 6, 2019

gbent said:
I disagree, it is driven over driver. In your example, a rear end has a large ring gear (driven), and a small pinion (driver). So say you have 4.11's, 37 teeth on the ring divided by 9 teeth on the pinion.

I'd call the OP's a .941:1, or for clarification, call it a .941:1 overdrive gear set.

Aren't we saying the same thing? Like I said (post #2) in the OP's case, .941 revolutions for 1 rev in the driven gear. In my example, 4.11 revolutions for 1 in the driven gear. The only difference between what you said and what I said is that you referenced an overdrive set while I did not. The results are the same.

EPAIII · Sep 6, 2019

The only proper way to do it is with Roman Numerals. So it's

XXXII to XXXIV.

bloomautomatic said:
Is the tooth count metric or imperial?

bridgedog · Sep 6, 2019

Just glanced at this and said to myself "well that's simple".
After reading all the following posts now I am not so sure.

gbent · Sep 6, 2019

Gordon Heaton said:
Aren't we saying the same thing? Like I said (post #2) in the OP's case, .941 revolutions for 1 rev in the driven gear. In my example, 4.11 revolutions for 1 in the driven gear. The only difference between what you said and what I said is that you referenced an overdrive set while I did not. The results are the same.

In your original post you have driving/driven. I said its driven/driving, and used a ring and pinion to illustrate your rear axle ratio example.

In any case, its easy to get words so similar confused.

Gordon Heaton · Sep 6, 2019

You are quite correct. I meant to infer that the driving number was listed first, not infer a mathematical operation. I should have written it so: driving:driven.

EmGo · Sep 6, 2019

gbent said:
I disagree, it is driven over driver.

No, it's driver over driven. Rear end ratios are one of those cases where people have been doing it wrong so long that wrong becomes normal, but in general use it's always driver/driven.

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