gear ratio

[Sam2197]

thanks for the help. im sure this is an easy thing to get confused

[JM987]

which would give you a looow speed, but high torque

[NickE]

Originally Posted by JM987

which would give you a looow speed, but high torque

This depends on what motor is used, and what the application is. For example, a 12:1 reduction used with CIM motors would be fast if used for an arm rotation, but slow for a drivetrain.

[JesseK]

As an addition to the original post:

If you ever see a reduction given in decimal format (e.g. the 2008 KOP's were 0.0784), THAT is where the output shaft rotates 0.0784 times per 1 revolution of the input (output:input). Car transmissions usually show reductions in this manner. This particular number (0.0784) was calculated by (14/50)*(14/50), where each 14-tooth gear is the input and each 50-tooth gear is the output in their respective stages. Also note what the reciprocal of this number is ( 1 / 0.0784 = 12.75), but to flip the decimal like that you also 'flip' the which side is the output and which side is the input, hence (12.75 : 1) is (input : output).

Whoever lost that argument was probably headed in the right direction but confused about the nomeclature, hence the argument kept going. Durn those kinds of arguments...

[MrForbes]

Originally Posted by JesseK

If you ever see a reduction given in decimal format (e.g. the 2008 KOP's were 0.0784), THAT is where the output shaft rotates 0.0784 times per 1 revolution of the input (output:input). Car transmissions usually show reductions in this manner.

When did this start? I must have missed it.

All the car transmission gear ratios I've seen are expressed as the number of turns of the input shaft : one turn of the output shaft. For an overdrive transmission, the overdrive ratio is expressed as a decimal because the output shaft turns faster than the input shaft.

(I read Hot Rod, not Motor Trend, maybe they do things differently?)

[JesseK]

Originally Posted by squirrel

When did this start? I must have missed it.

All the car transmission gear ratios I've seen are expressed as the number of turns of the input shaft : one turn of the output shaft. For an overdrive transmission, the overdrive ratio is expressed as a decimal because the output shaft turns faster than the input shaft.

(I read Hot Rod, not Motor Trend, maybe they do things differently?)

The decimal format is just the number itself, e.g. 0.0784 and not 0.0784:1.

I'll try to explain the reasoning so the OP doesn't get further confused... This stems from my street racing days back in college. Some of the guys were gearbox junkies and tuned their transmissions for lower top speed with ridiculous acceleration through a set RPM range known as a 'power band'. When they would talk about shortening a gear, this was the number they were messing with. It was always less than one, and it represented the reduction from the engine output to the shift stage rather than from one shift stage to the next (which is also sometimes seen). This allowed them to figure out if their cars were still in an 'optimal' power band for each gear after they made a modification to an engine component (which may have shifted the power band to a higher or lower RPM range). This tweaking is similar to the FRC electric motor curves vs the loads we put on the motors. It makes sense to me because the higher the number, the faster the output shaft spins.

I guess I just assumed this verbage can be used for all transmissions since you see that same decimal format used in almost every available FRC calculator. Maybe I was wrong.