Converting 48P to 32P

[joe.bielski]

Hey guys,
anyone know what the equivalent of 87T Spur 17T Pinion in 48P gears be in 32P gears? I'm tired of stripping gears

 

[Jeff@TireBalls]

56/11

 

[HANgOVER Airbrush RC]

divide the two numbers...
One you find the ratio, it's easy.

check it out....

87\17=5.12
so that's your ratio. If you have a spur in mind (I'll use the above example) then we can figure out the pinion.

so, 56/x=87/17 (x = the pinion we want to find)
in order to isolate "x" we will cross multiply.
that leaves us with...
56*17 = 87x with me so far?
all we need to do now is arithmetic...
952 = 87x divide by 87
10.94 = x
That gives you a 11 tooth pinion. (good job Jeff)

or we could shoot for a 90 tooth spur.

90/x=87/17
90*17=87x
1530=87x
17.58=x

lets check our work...

56/10.94=5.12 and
90/17.58=5.12

I realize it's impossible to have a half toothed gear....so let's round.

56/11=5.09 and
90/18=5.00
So, Jeff was closer with his math @ 56/11, but a good second choice (if the parts are available) is the 90/18.


See, algebra DOES come in handy...

Hope this helps.

 

[fr8cture]

Haha wow I havent done that since middle school. throwback. lol

 

[Olle P]

I would use easier, more generic, maths:
The 48P to 32P ratio for same diameter gears is 32/48 = 2/3 = 0.667.
For a given 48P gear the equivalent 32P gear thus have 2/3 as many teeth.

You'll likely end up with fractions. To keep a spur/pinion ratio as close as possible round both numbers up or down, depending on what gives the closest end ratio and what adjustments can be made to the motor position.

 

[onebullet]

awesome info, thanks for sharing fellas!

 

[Col_Sanders]

divide the two numbers...
One you find the ratio, it's easy.

check it out....

87\17=5.12
so that's your ratio. If you have a spur in mind (I'll use the above example) then we can figure out the pinion.

so, 56/x=87/17 (x = the pinion we want to find)
in order to isolate "x" we will cross multiply.
that leaves us with...
56*17 = 87x with me so far?
all we need to do now is arithmetic...
952 = 87x divide by 87
10.94 = x
That gives you a 11 tooth pinion. (good job Jeff)

or we could shoot for a 90 tooth spur.

90/x=87/17
90*17=87x
1530=87x
17.58=x

lets check our work...

56/10.94=5.12 and
90/17.58=5.12

I realize it's impossible to have a half toothed gear....so let's round.

56/11=5.09 and
90/18=5.00
So, Jeff was closer with his math @ 56/11, but a good second choice (if the parts are available) is the 90/18.


See, algebra DOES come in handy...

Hope this helps.

I would have just done 87/17=5.12. 5.12 is your final ratio. Then if you want to keep that ratio and wanted to use a 56t spur, 56/5.12=10.9 (11t pinion).

 

[Jeff@TireBalls]

I would have just done 87/17=5.12. 5.12 is your final ratio. Then if you want to keep that ratio and wanted to use a 56t spur, 56/5.12=10.9 (11t pinion).

That's the way I do it, I started with 56 spur as that is a very common size to find.

 

[Eric0424]

I would have just done 87/17=5.12. 5.12 is your final ratio. Then if you want to keep that ratio and wanted to use a 56t spur, 56/5.12=10.9 (11t pinion).

It's not your final ratio, it just the spur/pinion ratio. It's actually just the first calculation in the Final Drive Ratio equation.

 

[Col_Sanders]

I know. You still have the trans gearing and diffs, but that is irrelevant to this topic.

5.12 is the ratio at the input of the transmission.

 

[rustneversleeps]

54/14."thumbsup"

 

[oldbugs]

OMG. my head just exploded. Lol

 

[rustneversleeps]

OMG. my head just exploded. Lol

OK Should have known better how about 54/13. lol

 

[Eric0424]

I know. You still have the trans gearing and diffs, but that is irrelevant to this topic.

Then there was even less of a reason to use the word "final". It has a specific meaning in this context and it's not the spur/pinion ratio, or the transmission ratio or the axle ring/pinion ratio. You may not care about the terminology, but others do. That's why I'll correct these minor flubs or "slips of the tongue" when I see them. Like correcting and error in a part number or web address, it's nothing personal as we all make mistakes.

 

[HANgOVER Airbrush RC]

While the answer to many of us was obvious, I was trying to explain how to get the right answer, rather than just giving the answer.
That way, any others that may visit this thread might not have to ask, but would have the needed info to figure it out.

Hence,

IF we want the ratios to be equal, THEN

gear set 1 = gear set 2, where Gear set 1 is known, and Pinion2 is unknown

Spur1 Spur2
------ = --------
Pinion1 Pinion2

Cross multiply and we get

Spur1 x Pinion2 = Pinion1 x Spur2

So to solve for Pinion2, we divide BOTH sides of the equation by Spur1.
The two Spur1's on the left cancel each other out, and we are left with

Pinion1 x Spur2
-------------------- = Pinion2
Spur1

let's not forget, that we can swap Pinion2 and Spur1, if instead we knew the pinion and wanted to solve for the spur gear.



If we set up our "formula" this way, anyone can plug in their numbers and have a go, without having to remember, "Do I multiply or divide the gear ratio by the new number?"

There are many ways to get out of the woods if you know where you want to go, The formula (and the super long explanation earlier) are meant to be a map for those who are not as "mathematically inclined" as others.

you know, "give a man a fish, vs. teach a man to fish," That old nugget.

Maybe I am making it too hard?

Olle P,
That is an interesting concept. I had to look in my Machinist's Handbook.
But you are right. A 48P gear would have 48 teeth on a 1" gear, so your method works too.
Useful info.
Thanks.

 

[Col_Sanders]

:roll: I didn't say final drive ratio there Mr Technical. It was the final ratio in the answer to his question.

 

[Eric0424]

I didn't say final drive ratio there Mr Technical. It was the final ratio in the answer to his question.

No point in getting offend or rolling your eyes and your attempt at an insult is weak to say the least. You misspoke, time to move on.