Gear Ratio Equation and Chart I Made for us Crawlers...

[thegodofclod]

ok well i was bored and i wanted to know the ratio of my projects. so i built this little chart using gathered information from the board. it should explain everything you need to know to calculate your own crawl ratio. it also has all the ratios for a maxx set up so you can see what you can get in first and second. ok well here it is.....its just copied and pasted. hope this thing helps you guys figure your crap out.


Gear Ratio Equation

**done using juggy tranny**

First take the # of teeth on the spur gear which in this case is 40.

Divide by # of teeth on pinion which in this case is 9.

40/9 = 4.44

Next take the stock transmission ratio which in this case is 6.37 and multiply it by 4.44.

4.44 x 6.37 = 28.3

That would be the ratio of your transmission.....now for all together crawl ratio with axles.

Then take the ratio of your axles which for a jugg/txt would be 2.0:1 and muliply to 28.3 or what ever your
trans ratio came out to be.

28.3 x 2.0 = 56.6 crawl ratio

If you are running a gear reduction take that ratio which i will say is a gd-600 using a 2.5:1 ratio and multiply
that to your entire crawl ratio.

56.6 x 2.5 = 141.5 final ratio.

Thats all there is too it.


Ratios on common trucks....

E-maxx,

1st gear = 2.76 (with 72t spur 3.1 G.R and 9t pinion = 194.4)

2nd gear = 1.72 (with 72t spur 3.1 G.R and 9t pinion = 121.14)

diff = 2.84

teeth on spur = 72 or 64*


Juggy / TXT,

tranny = 6.37 ( final ratios on above chart)

axle = 2.0

teeth on spur = 40



(* = interchangeable)

GD-600 Ratios,

18t pinion = 2.5

15t pinion = 3.1

13t pinion = 3.5

12t pinion = 3.8

im going to use the ratios i have posted next to the maxx ratios. i will see how they work.

 

[NeoSlayer888]

Nicley done. I vote to have this be a sticky.

 

[RCHunter]

How did you get to the 6.3 juggy tranny ratio? There is the 40t spur then 2, 27t gears then a 30t gear. Am I missing a gear somewhere?

Here are some Maxx Ratios I had

Gear Reduction
36t / 18t = 2:1
36t / 22t = 1.63:1

Stock Maxx Diffs
Ring 37t / Pinion 13t = 2.85:1

Stock Maxx Tranny
1st Gear = 2.77:1
2nd Gear = 1.72:1

Spur Ratio
Spur 66t / Pinion 18t = 3.67:1
Spur 66t / Pinion 14t = 4.71:1

FINAL RATIO
1st Gear: 3.67 X 2.85 = 10.46
10.46 X 2.77 = 28.97
Reduction = 28.97 X 1.63 = 47.22:1

2nd Gear: 3.67 X 2.85 = 10.46
10.46 X 1.72 = 17.99
Reduction = 17.99 X 1.63 = 29.32:1

 

[JohnRobHolmes]

this needs a big bump, and I am asking myself this for when I get home (but if you know feel free to post it)

What is the diff ratio for the mad/ twin force
What is the diff ratio for a tlt 2.66:1
What is the ratio for a pede tranny (internals only)

edited in answers

 

[JasonInAugusta]

JRH,

The E-Pede tranny has a 2.72:1 internal ratio (Hence the 272 Magnum name)

The 272 Magnum is actually shared among the E-Rustler, E-Stampede, and Bandit.

The N-Pede has a 372 Magnum...guess what the internal ratio is. :lol:

The Mad/Twin force have standard 1/8 scale diffs.

43 tooth ring gears with I think 13 tooth pinions.

 

[JohnRobHolmes]

thanks, JIA. I know searching would have produced that, but I didnt have time.

Now they are in this thread. I think it's a good candidate to pile all "gear ratio", "final drive", and general gearing discussion into. It has equations, and a good list of ratios and math in it.

 

[JohnRobHolmes]

yep, mad force has a 43:13 reduction. i finally got the chance to count it.

so here is what I am figuring out.

What is my final drive ratio if I want to go 4mph with a 15" rollout and a motor spinning 40K rpm

4mph= 253440 inches/hour
= 4224 inches/ minute

4224"/ 15" = 281.6 rpm at wheel to hit 4mph

40,000 rpm motor / 281.6 rpm at wheel = 142:1 final ratio



spur/ pinion ratio is 66/13 or 5.077
diff ratio is 43/13 or 3.3

so 16.7541 is my reduction without tranny. This leaves my tranny with a reduction of 8.4755

Now I need to build the tranny.

 

[MSH]

http://www.scriptasylum.com/rc_speed/

this is a brushless based calculator, you enter trans ratio's, tire size, Kv and battery voltage and get to see the speed you will have."thumbsup"

 

[kerrywittig]

Does anyone know what the ratios are for the RC4WD RI & R2?

Got some of it..............

R1-50:1 to 120:1 Gear Ratio

R2-10:1 to 30:1 Gear Ratio

But....what are the actual "internal" ratios of the assemblies themselves?

Thanks, Kerry

 

[grapegoat]

this is fricken sweet god of clod! never have i seen gear ratio stuff posted so black and white. its like gear ratio for dummies, which is right up my alley :lol:. question how did you get the tranny ratio. i got an e-maxx tranny and i see on here that it is 2.77:1 but i want to know how you got that.

 

[hairba11]

I have a gearing spreadsheet hosted on another site.
The link is in my sig.
It was originally designed with mini's in mind, but gears are gears.
now that I am getting into crawlers, I wil probably release a V4 to add extra GRU's
I don't know if there is a host for zip files or not, so for now its just linked to one18th

:edit:
OK, VERSION 4 AVAILABLE

I added a handfull of other reductions:

transmission
GRU 1
Portal axles
GRU 2

I updated the instructions also.

If it seems like it would be worth the effort, I could add a page 3 with reference gear ratios.
It seems like that is where this thread is headed.

:edit:
OK, who am I kidding, I'm working on a page 3 which wil have stock gear ratio's broken up by mfg., model, and component. If people want to drop off gear ratio's in this thread, I can add them to the spreadsheet for additional reference.

p.s. I went through a spare gearset for my TXT trans, from bottom to top,
30/16=1.87, 27/15=1.8, 27/15=1.8, so 1.87x1.8x1.8= 6.05 for a gear ratio before the spur.

 

[hairba11]

OK, here is a link to what I have so far, I found the tranny list, and added that. I don't have all the axles
I also don't have much for orginization yet, but right now I'm just collecting data.

http://i137.photobucket.com/albums/q217/hairba11/mlst/gearing.jpg

 

[JohnRobHolmes]

Nice work!

 

[hairba11]

Thanks, its slow going, I cruised rc4wd's site and added some of their stuff to it.
I'm still missing:
TLT info
Maxx axle info
madforce tranny info
Highlift info
bruiser info
anything else...
I only have so much free time for reading and searching.

I am hot linking the file now
Gearing spreadsheet V4

Incomplete reference section, but there it is.

 

[slobin3d]

bringing this back up again...

I want to match my tlt/pede final ratio setup to my WK/xxx setup so I will have similar wheel speed. I've done the math to find the final on my pede which is 52.45-1 standard setup, and the WK/xxx without spur and pinion is 12.0-1 I do the division to find that I need a S/P ratio that is 4.37-1 I want to use an 11t pinion to get the smallest possible spur. what math do I use to figure what spur I need?