im very confused

civic freak · #1 07-10-2003, 07:17 PM

can somebody please explaine a very simple way to figure out gear ratios and if u can can u tell me how to tell if its fast or slow and what tha numbers mean ive used search tool no luck at all can someone please explain very simply simply enough that tha average joe knows how or just tha simplest way u no

faulkbeets · #2 07-10-2003, 07:18 PM

i cant help you all the way but just a little , the lower the number it means that it is faster but usually takes more time to build it up to that speed

civic freak · #3 07-10-2003, 07:20 PM

which number all of em or just one????????

faulkbeets · #4 07-10-2003, 07:22 PM

cant remember exactly but the numbers have something to do with the number of pinions on something ummm i think all of em not sure correct me if im wrong

frizzen · #5 07-11-2003, 03:05 AM

Ok, gear ratios are REALLY simple, once you understand the basics. We'll worry about: Gear ratio numbers, Torque, and Speed.

A gear ratio is the number of times the drive source (engine) has to rotate for each time the output (axle) rotates.

Let's start off with something for a real car. (Differential gear ratio, for RWD vehicles) Economy gearing is usually 2.73:1 or numerically lower, while accelleration gearing normally uses up to 4.11:1, but occasionally even in the 5:1 ratios. Hey, car-guys like small numbers to one.

Confused yet? I'll make it easier. Something like a 1:1 ratio will give you top speed but little/no mechanical advantage (extra torque) so whatever the motor or engine can produce is all you get. So, you've got a motor producing 1 ft/lb of torque, and the output from the gears is 1 ft/lb torque, and is at the same speed.

But let's have a 100:1 gear ratio now, you have more torque than you know what do to with, but your top-speed sucks!! You have a ton of mechanical advantage here, but because of it, you can't spin the output with much speed at all. The same motor producing 1 ft/lb of torque is attached to this ratio, and produces 100 ft/lbs of torque. BUT it spins 100 times slower than imput.

So, just to confuse you more, let's stick an Over-drive gear ratio in there and see what happens!
- For this demonstration we'll use 0.50:1 So, the imput side gets 1/2 a rotation for every rotation of the output. (This is also written as a 1:2 ratio, but we're talking about use in cars, so it's all referenced to 1 revolution of the output.) Anyway, the same motor is attached to this ratio, and it still produces 1 ft/lb torque, but the output only has 1/2 (0.5) a ft/lb of torque, but spins 2 times faster than the imput.

IF any of this makes sence yet, I can move on to how to actually calculate the ratio.

charliebrown · #6 07-11-2003, 09:13 AM

A way to figure out your gear ratio is this:

Take the number of teeth on the border of the idler gear and divide the number by 6 for the pinion gear's teeth. you get 3, so the pinion gear has to turn 3 times to make the idler gear turn once.

Now, take the number of teeth of the axle gear and divide that number by the idler gear's CENTER GEAR's number of teeth. The answer is number A.

Now take number A and multiply it by 3 to get your gear ratio.

EX: There are 6 teeth on the pinion gear, 18 teeth on the border of the idler gear, 6 teeth on the center of the idler gear, and 24 teeth on the rear axle gear. Divide 18 by 6, and 24 by 6. The answers are 3 and 4. Multiply 3 and 4 together and put the answer over /1, so you get a 12/1 or 12:1 gearing ratio.

MadScott · #7 07-11-2003, 11:38 AM

The easiest way to figure it out is to go by color, red is the fastest top end speed with poor torque and blue has the best acceleration but lacks top end speed.

civic freak · #8 07-11-2003, 02:04 PM

i thank you all so much, i understand u frizzen till' your 3rd paragraph then i sooooooo comfuzd i dolmast 4get how 2 spel. i understand charlie brown until tha 4th paragraph then im totally lost but once again thank u all maybe ill understand when im in 11th grade.

, silla dont no what it means but it sure sounds cool