Gear Ratio chart help
 

Guys,

I am in need of some help. :blush:

I have the below gear ratio chart that is in need of expanding from a 90 to 85 spur gears and 15 to 26 pinions.

But I am after a full chart with all pinions and spurs, but maths is not one of my strong points so hence why the help. I have no internal ratio at all so kindof stuck with the below. Anyone out there capable of working this out or figuring out the internal ratio. Thanks.

15 16 17 18 19 20 21 22 23 24
90 13.29 12.46 11.72 11.07 10.49 9.96
89
88
87 12.04 11.33 10.70 10.14 9.63 9.17
86 11.20 10.58 10.02 9.52 9.07
85

The formula you need is

Overall Ratio = Spur Gear / (Pinion * Internal Ratio)

So (and my math is rusty), transposing that, I think you get

Internal Ratio = (Spur Gear / Overall Ratio) / Pinion

Failing that, I have an excel file that you can play with to your heart's content.
If you pm me your email, I'll send it to you.

Is it not

(spur/pinion) * Internal Ratio = Over all ratio

Any how i think your internal ratio is 2.215
I have email you a chart, so see if it make sense.

Matty - you might be right - I may have the brackets in the wrong place:blush:

Excel seems to work it out without needing any brackets using the formula OR=Spur/Pinion*IR

So my bad - sorry

Matty,

Thanks, I will have a go with it this evening. The car I have doesnt have a ratio in the instructions, as they are kindof vague due to it being a prototype so doesnt make life too easy when you upgrade to brushless.:cry:

Just go to:-

www.gearchart.com

type in the car you have, and it will print out a coloured gear chart for you.

Greyfox - Mmm dont think they have proto type buggies on their lists. Thanks anyway

here's one using gearchart starting with your smallest pinion & spur based on B4 internal ratio of 2.6

you can do the same if you try, just fill in the bits circled

I found a rough and very close ratio.

2.214 is almost on the button

Matty almost had it, I think it actually may be 2.2145 but it wont make that much of a difference. Now I can base my ratios from what I use on my B4 to my 4wd.

Thanks for all your help guys, much appreciated.