Author Topic: Sprocket size  (Read 5592 times)

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Offline Smokingunz351

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Sprocket size
« on: January 03, 2006, 04:46:00 pm »
guys i need your help. im switching from a #35 chain and sprocket to a 40/41 size chain and sprocket setup. my problem is i dont know how much bigger a #41 sprocket is going to be in diameter then a 35. for example im runnin a 72 tooth #35 sprocket on the rear, what size 41 sprocket would i need to have the same gearing? is there some kinda math formula or something to help me out here? thanx for yalls help


Bill
Custom doesn't come in a box! It comes one saw blade at a time"

Offline Squidd

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« Reply #1 on: January 03, 2006, 06:08:59 pm »
Gear "ratios" are determined by "both" the drive and driven gear...

So in your example if you were running a 72 tooth #35 and lets say a 24 tooth drive (for ease of math)...

72/24=3:1 ratio

So to get the same from the #40/41 size with a 45 tooth rear you would need a 15 tooth drive to get same gearing...

45/15= 3:1 ratio

The 45 tooth rear is going to be "about" 7" in diameter...

You could get the same "ratio" in #40/41 chain with a 48 tooth rear and 16 tooth driver...

48/16= 3:1 ratio... at 8" diameter..

Then if you want to change "ratios" and pulling and to speed characteristics, you start interchanging drive and driven gears...

48 tooth rear with 15 drive or 45 tooth rear with 16 drive..

48/16= 3.2:1 ratio and 45/16=2.8:1 ratio....

Then depending on engine torque, chassis traction and track length...you can adjust from there....

The 3.2:1 will "pull hard" and wind out quick than either of the 3:1s will...and the 2.8:1 will have higher top speed at loss of pull from corner...

Got it..? 8)
Randy Stys
"Pull My Finger"
 63 Cub Cadet S/A

Offline Squidd

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Sprocket size
« Reply #2 on: January 03, 2006, 06:19:21 pm »
Now, your #35 72 tooth gear is about 8 and 3/4" in diameter...

The corresponding #40/41 at 8 3/4' is a 54 tooth gear...

So using the "ratio calcs" you would need a 18 tooth drive gear to get the "SAME" 3:1 ratio as the example above...

54/18= 3:1 ratio...

ALL THREE gear sets will pull exactly the same with a 3:1 ratio...

45/15, 48/16, 54/18..etc...

Now does that make sence...? :wink:
Randy Stys
"Pull My Finger"
 63 Cub Cadet S/A

Offline Smokingunz351

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« Reply #3 on: January 03, 2006, 09:22:29 pm »
clears it up a lil bit. i suck at math lol. i dont have the mower here at the house and im not going to be able to get to it at school for a few days so could you tell me what a #35 15 tooth sprocket is in a 40/41 size. this is for the sprocket mounted on the tranny. thanx for the info though and im glad theres people out there to help with this kinda thing.

later
Bill
Custom doesn't come in a box! It comes one saw blade at a time"

Offline Squidd

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« Reply #4 on: January 03, 2006, 09:50:34 pm »
A #35 15 tooth is right at 2" diameter...

A #40/41 11 tooth is right at 2" diameter...

I'm going to asume you have a 72 rear and 15 drive #35..or a 4.8:1 ratio...

If we go with "diameters" in #40/41 we get...54 rear (8 3/4") and 11 drive (2")...

54/11= 4.9:1 ratio...pretty close to the same...
Randy Stys
"Pull My Finger"
 63 Cub Cadet S/A

Offline Smokingunz351

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« Reply #5 on: January 04, 2006, 03:47:03 pm »
hey thanx for the help. i was kinda overwhelmed with all the math and stuff. but like i said before im glad theres people out there who know this stuff.
Custom doesn't come in a box! It comes one saw blade at a time"

Offline Squidd

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« Reply #6 on: January 04, 2006, 05:46:53 pm »
Well if think this part was hard.... :wink:

Now you still have to factor in your trans gear ratio and your pully ratio, and whether you straight drive or overdrive...
Randy Stys
"Pull My Finger"
 63 Cub Cadet S/A