Understanding of a simple 4 gear box and gear ratio

[Kaydash]

Hi all :)

I've been building a good number of best supercar mocs lately, and i decided to step up my game a bit, and build a supercar (1:10) of my own. If the paneling, steering, making a chassis is Something i can do without too much trouble, it's not the same when it comes to gearbox. As i Don't want to rehash somebody else's job, or at least not completely (lol) i've been busy these past few days trying to learn how gearing works. And thx to sariel and his work, (e.g gear calculator / tutorial) i've learnt a lot already. But obviously, i'm just beginner and there is a lot i have to figure out before i can do a gearbox of my own.

 

So i've build this one, found on internet and try to study it:

I was trying to calculate gear ratio of each gear but i'm already stuck :(

So question, since i can't even figure out which one of the entry is the input, hence the other being the output. 

Isn't a gearbox supposed to gear up whatever the gear engaged? so we'd have at the end Something like this, say:  1st: 1:6   2nd 1.4  3rd: 1.2,1  and 4rth: 1:1 (not related to the picture below)

When i look at that exemple and the placement of the 1st gear, hence orange entry being the input, it appears to gear down, and hence, i've considered the red entry being the input.

I'm already lost.

And worse: i can clearly  count that i have a 1:6 gear ratio, but when i try to calculate, the result won't match (4th gear on the picture):

24 teeth into 8 teeth: 1:3

8teeth into 16 teeth 2:1

Following grey 16teeth on a different axle is idle

16teeth into 8teeth 1:2

 

final ratio with math: 1:3 (calculator)  but when i count 6 révolutions for the last gear, so i'should have a 1:6 ratio

 

What am i missing here?

thx for helping me guys!

Sorry for the noob questions, but everything's gotta be a lot easier once i figure this out :)

 

Edited March 29, 2020 by Kaydash

[mortenm]

Red is input. 

1st: 1:1

2nd: 1:2

3rd: 1:3

4th: 1:3 x 1:2 = 1:6

[Kaydash]

thx mortenm. How do you visually define that red is input?

[mortenm]

Because of the ratio. If it's the other way around, the car would go faster in 1st gear compared to 2nd.

Maybe someone else have a better way to explain it ?

[Kaydash]

When i look at every single supercar, the 1st gear ratio is always higher than the second gear etc... if that's what you mean by "faster". Or am i wrong? :)

[Gray Gear]

I assume we are talking about non-RC cars?

Some cars (like the Defender) have a fcked up gearbox that will make the fake engine turn faster when you shift up while maintaining the same wheel speed, while it should be the exact opposite. The engine should do less revolutions per wheel revolution when you shift up.

[Kaydash]

thx grey gear. Non-RC cars, absolutely

On 3/30/2020 at 5:45 PM, Gray Gear said:

 The engine should do less revolutions per wheel revolution when you shift up. 

That's what i figured. so it's maybe the obvious way to identify an input entry from an output one?