Total gear ratio on 4WD limitless! Abstract dilemma

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Total gear ratio on 4WD limitless! Abstract dilemma

Horhe

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Hi all,

First post here besides the introductory one :).

Second of all, I have a bit of a struggle understanding some things related to the calculation of the RPM @ wheels.

Here's the data:
I am looking to calculate [email protected], for an Arrma Limitless. The configuration is the following:
- Pinion 16T / Spur 34T - resulting in a gear ratio of 1.26
- Front Diff Pinion 13T / Crown 43T - resulting in a diff gear ratio of 3.31
- Rear Diff Pinion 13T / Crown 43T - resulting in a diff gear ratio of 3.31 (obiviously)

Now, my dilemma is, in the case of the 4WD Arrma Limitless:
Do I determine the "total" gear ratio by MULTIPLYING ALL THREE RATIOS? (1.26 x 3.31 x 3.31)
or
Do I just multiply the center and one of the diffs ratios (1.26 x 3.31)
?

In theory it makes sense that in order to calculate the RPM at the wheels, say...front wheels, I'd just have to multiply the center pinion/spur ration with one of the diffs ratios! And thus I'd get the total gear ratio to help me calculate the RPM @ the say...front wheels as per my initial example. Since the Limitless has the same front and back gear ratio, that's a bit easier than for instance in the case of the Felony where the front diff and back diff ratios are different.

Is this correct? I am struggling a bit with the abstract ideea of total gear ratio.

Thank you!
 

ABabyEater

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Multiply by only 1 diff ratio. Think of it as turns needed to rotate a wheel.

The motor has to turn more than once to turn the center driveshaft one time, since it has a smaller pinion than spur, right? So, it take 1.26 turns of the motor to make 1 revolution of the center driveshaft. It takes 3.31 revolutions of the center driveshaft to rotate the wheels once, right? So, since 1.26 motor rpm = 1 center driveshaft rpm, and 3.31 center driveshaft rpm = 1 wheel rpm, it makes sense that 3.31 x 1.26 gets you the amount of motor revolutions to find the wheel revolutions, right?
 

Horhe

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Multiply by only 1 diff ratio. Think of it as turns needed to rotate a wheel.

The motor has to turn more than once to turn the center driveshaft one time, since it has a smaller pinion than spur, right? So, it take 1.26 turns of the motor to make 1 revolution of the center driveshaft. It takes 3.31 revolutions of the center driveshaft to rotate the wheels once, right? So, since 1.26 motor rpm = 1 center driveshaft rpm, and 3.31 center driveshaft rpm = 1 wheel rpm, it makes sense that 3.31 x 1.26 gets you the amount of motor revolutions to find the wheel revolutions, right?
Thank you! That was my reasoning as well, but a few thigs confused me! One would be that I’ve seen so many stated diff ratios for the limitless and felony that were wrong, numbers that do not make much sense, and the other aspect was the felony!
How would you calculate the rpm @wheel for the felony?
I guess you can only calculate RPM at the front wheels and then the obviously different rpm at the back wheels and then perhaps average them!
Thanks for the input! Much appreciated! 😃
 
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