Whats everyones thoughts on an 8 ball or a 12 ball spur gear.

You have to put alot more pressure on the 12 ball to keep it

from slipping,,, maybe slightly smoother ?

Whats everyones thoughts on an 8 ball or a 12 ball spur gear.
You have to put alot more pressure on the 12 ball to keep it
from slipping,,, maybe slightly smoother ?

I think just the opposite.
There is actually less pressure with more balls.
Per ball.. and that is really what it is all about.

I think of situations like that as men doing work.
The idea of those balls is to drive the car forward.
It's the only means of transmitting the power from the spur,
to the axle.
The 12 guys can do the job easier than 8.
They will wear out slower, because they are doing less work... each.
What if there were only 3-4 balls?
They would have to work MUCH harder than 12... to get the same
amount of 'work' from them..
And because you had to 'load' them more, they would 'wear out'
a lot more quickly..

When you build a racing transmission for a car, you ADD plates...
For the same reason.. more friction, better lockup with the same
amount of pressure.. Same with dragster clutches.. they use a lot of plates.
More friction.

I could also be wrong... :drunk:
But you asked for thoughts..

I would have to agree with Dan. 12 balls will decrease the slip depending on what kind of Diff balls you use and what kind of diff lube you use. I use Muddslide diff balls and diff lube. If you have slip your car will not run right less slip on the spur more power to your axle. I run stock class so I need as much power as possible so I usally run 12 balls. I think if you dont have a smooth and locked axle and spur you have nothing!!

I would have to agree with Dan. 12 balls will decrease the slip depending on what kind of Diff balls you use and what kind of diff lube you use. I use Muddslide diff balls and diff lube. If you have slip your car will not run right less slip on the spur more power to your axle. I run stock class so I need as much power as possible so I usally run 12 balls. I think if you dont have a smooth and locked axle and spur you have nothing!!

Yes what Dan said.

More balls less heat!!!

I do understand what your saying.

The pressure comment from my end is that with the associated style diff cone and spring washers , you have to give it an extra turn with 12 balls.

But thats working just the opposite ? the more pressure is divided by 12
instead of 8 to get the same grip per ball.

Not that it matters , but these are ceramic balls.

NCFRC, Think more in terms of the diff need 10 lbs of pressure applied to the balls (no matter how many there are) to keep the diff from slipping when power is applied from the motor. If you have 8 diff balls you dispersing those 10 lbs across 8 points, when you have 12 balls the same pressure is being dispersed across 12 points. You don't need to develope the same grip per ball, just the same grip from the diff. I have never payed any atention to how many turns it takes to have a tight diff, not even sure how to measure that.

Well guys I had been running 8 ball gears then i read about touring car racers drilling 8 ball gears for a 16 BALL DIFF! So i had the same thinking.. the more the better but i found it wore quickly and while smooth it wasnt terribly free either. Now im using the black kimbourgh gears and find them very free. Any way heres the link if anyone is interested. http://racingfactory.wordpress.com/2007/08/13/building-the-16-ball-trf415-diff/

Edited for wasting bandwidth...sorry all!

Here's my thought...

Given the varying structure of diff balls and diff rings AND diff lube, it's impossible to say that one is better than the other, without defining what diff setup someone has; and also the condition of the diff to begin with. First off, let me state this:

"Coefficients of friction are extremely sensitive to atmospheric dust and humidity, oxide films, surface finish, velocity of sliding, temperature, vibration, and extent of contamination. In many cases the degree of contamination is perhaps the most important single variable."

If you have 8 diff balls and apply 10lbs. of force through the use of the differential tightening nut/screw, then you are, for all practical purposes, applying 10/8lb, or 1.25lbs, of force per ball. If you had 12 diff balls, then you are applying 0.8333!lbs of force per ball. However, remember that the ball is an intermediary device that simply (at this stage) transmits the force to the opposite diff ring. The ball doesn't do a thing until rotated, which leads to the next observation...

The force required to rotate the spur gear while holding the wheels still (diff slipping) can be considered a tangential force. In other words, someone holds the wheels stable and another person places their finger on the spur and pushes in a linear motion; a tangent line to the axle. We don't know what amount of force it takes, so let's just go on!

The Coefficient of Friction is what I think you are after comparing 8 to 12. However, there is no simple calculation for this, as you are not dealing with horizontal surface to surface friction (gravity) nor are you dealing with surface to surface using strictly tangential forces. But, for arguments sake, let's just plug the numbers into a formula, FrictionCoefficient = F/N, where F is the Tangential Force required to produce sliding (diff slippage) and N is the Normal Force between the surfaces (pressure per ball). With 8 balls, this is 1.25. For fun, let's say the tangential force is 3lbs.

Fc = 3/1.25, which equals 2.4. There isn't a weight attached to this number, it's simply 2.4 as the Coefficient of Friction given the other data, F and N. If we had 12 diff balls, the formula would be:

Fc = 3/0.8333!, which equals ~3.600. There's a big difference, but most likely this isn't going to be true because I've never done the experiment and want to have some theory to throw out there! :) I'm going to say that both setups have the same or comparable Fc, which would equate to this:

2.4 = F/0.8333!, which makes F, our tangential force, 1.99992lbs. My theory, simply using no real-world numbers, is that the more diff balls used will actually make the diff slip easier. However, a side affect is that the diff will be smoother due to the Angle of Repose (in relation to the diff rings/balls).

The last item to take into account is that if you are going to test this, you need calculate the correct F. Since the diff balls are not on the outside of the gear, you are not applying force directly to the balls when rotating the spur gear. If you applied the force directly to the balls themselves, then it would be much higher, as you are not multiplying the force via a fulcrum system. Without pictures, this whole concept is difficult to visualize. Anyways, you would have to test the diffs with:

A. The same type and amount of lube, or none at all, and in a very well controlled environment.

B. The same type of diff balls and rings.

If anyone has the equipment to test this accurately, I'd like to see the results. I may setup a crude mechanical method, but it certainly won't be accurate enough to make mathematical conclusions. The most difficult part is the ability to disassemble and reassemble the diff to the same normal force, 10lbs, or whatever is used in the experiment. You simply can't do this by 'feel'. The nut either applies 10lbs of force or it doesn't!

Yeah.... that.... or...
you can tighten the nut until the diff doesn't slip..

NCFRC, Think more in terms of the diff need 10 lbs of pressure applied to the balls (no matter how many there are) to keep the diff from slipping when power is applied from the motor. If you have 8 diff balls you dispersing those 10 lbs across 8 points, when you have 12 balls the same pressure is being dispersed across 12 points. You don't need to develope the same grip per ball, just the same grip from the diff. I have never payed any atention to how many turns it takes to have a tight diff, not even sure how to measure that.

Mike's post is right.

The amount of pressure it takes to lock up the differential has nothing to do with the number of balls the diff has.

Force to overcome friction = Coefficient of friction X Normal force

Simple equation. Surface area and consequently pressure have nothing to do with it. Where Super X-ray is going wrong with his thinking is that he is varying the coefficient of friction based on pressure. The coefficient is defined only by the properties of the two things in contact with each other, nothing else.

So why would more balls be better? Because although the number of balls doesn't effect normal force you need to lock the diff it does effect the pressure on each ball. Although the forces involved here are pretty small the pressure on the balls and rings is huge since they have a very very tiny surface area in contact with each other. The more pressure there is the more they will deform, the more they deform the less the balls will want to roll when your wheels are spinning at different speeds and the more they will want to slide. The more the balls slide the worse your diff functions. Also, the balls and rings wear out sooner.

So why not run more balls? There would be a point of diminishing returns where the diff is really not going to function much better, so now you've added more weight and more cost for no return. To be honest I have no idea how many balls we really need. I have never botherred to try and find out. For all I know you may only need 4 balls in your diff if you're running stock. I know back in the day I used to run a ball in every other hole and the diff felt fine.

The only reason it might initially seem like it requires more force to lock up a diff with more balls is that when you first tighten down the diff it would deform the ring so the balls would be sitting in little divots. Fewer balls would mean more pressure and deeper divots. Once you spun the diff a few times and wore in a channel all the way around for the balls the difference would go away. This also why we run harder diff balls then diff rings, so that the ring does the majority of the deforing and wears a channel while the ball stays more round.

Here's my thought...

Given the varying structure of diff balls and diff rings AND diff lube, it's impossible to say that one is better than the other, without defining what diff setup someone has; and also the condition of the diff to begin with. First off, let me state this:

"Coefficients of friction are extremely sensitive to atmospheric dust and humidity, oxide films, surface finish, velocity of sliding, temperature, vibration, and extent of contamination. In many cases the degree of contamination is perhaps the most important single variable."

If you have 8 diff balls and apply 10lbs. of force through the use of the differential tightening nut/screw, then you are, for all practical purposes, applying 10/8lb, or 1.25lbs, of force per ball. If you had 12 diff balls, then you are applying 0.8333!lbs of force per ball. However, remember that the ball is an intermediary device that simply (at this stage) transmits the force to the opposite diff ring. The ball doesn't do a thing until rotated, which leads to the next observation...

The force required to rotate the spur gear while holding the wheels still (diff slipping) can be considered a tangential force. In other words, someone holds the wheels stable and another person places their finger on the spur and pushes in a linear motion; a tangent line to the axle. We don't know what amount of force it takes, so let's just go on!

The Coefficient of Friction is what I think you are after comparing 8 to 12. However, there is no simple calculation for this, as you are not dealing with horizontal surface to surface friction (gravity) nor are you dealing with surface to surface using strictly tangential forces. But, for arguments sake, let's just plug the numbers into a formula, FrictionCoefficient = F/N, where F is the Tangential Force required to produce sliding (diff slippage) and N is the Normal Force between the surfaces (pressure per ball). With 8 balls, this is 1.25. For fun, let's say the tangential force is 3lbs.

Fc = 3/1.25, which equals 2.4. There isn't a weight attached to this number, it's simply 2.4 as the Coefficient of Friction given the other data, F and N. If we had 12 diff balls, the formula would be:

Fc = 3/0.8333!, which equals ~3.600. There's a big difference, but most likely this isn't going to be true because I've never done the experiment and want to have some theory to throw out there! :) I'm going to say that both setups have the same or comparable Fc, which would equate to this:

2.4 = F/0.8333!, which makes F, our tangential force, 1.99992lbs. My theory, simply using no real-world numbers, is that the more diff balls used will actually make the diff slip easier. However, a side affect is that the diff will be smoother due to the Angle of Repose (in relation to the diff rings/balls).

The last item to take into account is that if you are going to test this, you need calculate the correct F. Since the diff balls are not on the outside of the gear, you are not applying force directly to the balls when rotating the spur gear. If you applied the force directly to the balls themselves, then it would be much higher, as you are not multiplying the force via a fulcrum system. Without pictures, this whole concept is difficult to visualize. Anyways, you would have to test the diffs with:

A. The same type and amount of lube, or none at all, and in a very well controlled environment.

B. The same type of diff balls and rings.

If anyone has the equipment to test this accurately, I'd like to see the results. I may setup a crude mechanical method, but it certainly won't be accurate enough to make mathematical conclusions. The most difficult part is the ability to disassemble and reassemble the diff to the same normal force, 10lbs, or whatever is used in the experiment. You simply can't do this by 'feel'. The nut either applies 10lbs of force or it doesn't!



UHHHHHHHH WHAT??? LOL

good post

Yall think about balls alot more than I do

UHHHHHHHH WHAT??? LOL

good post

It was actually 100% incorrect, but that's ok :)

It was actually 100% correct, but that's ok :)



?????

What was the point of doing that?

That was the biggest waste of BANDWIDTH ever used on this forum.....

Does any body have any calculations on how tight I should tighten my wheel nuts?

You guys are totally right what we need on Hobbytalk are fewer discussions on how our cars work and more sponsor plugs and arguments about class rules.

:rolleyes:

:lol: :lol: :lol: :lol: :lol: I'm with you.
Richard T

You guys are totally right what we need on Hobbytalk are fewer discussions on how our cars work and more sponsor plugs and arguments about class rules.

:rolleyes:

You guys are totally right what we need on Hobbytalk
are fewer discussions on how our cars work and more sponsor plugs
and arguments about class rules.

:rolleyes:

Amen.
Never mind about the "how things work" BS...
We all know it's "chassis... chassis.... chassis...." :drunk:

Amen.
Never mind about the "how things work" BS...
We all know it's "chassis... chassis.... chassis...." :drunk:


No, it is all BATTERIES -POP- BATTERIES -HISS- BATTERIES -BANG!!-

I love this sport!

AWWWW come on, we all know it about who can wheel it the best.......

I'd convert this to a poll, since the lack of information is overwhelming!

I believe eight (8) differential balls is best.

I'd convert this to a poll, since the lack of information is overwhelming!

I believe eight (8) differential balls is best.

I think the real answer is, do what you want.
3 will work, 6 will work, or 12.

It is going to require the same amount of total pressure to
move the wheels, regardless of the number of balls,
like Mike said.

The number of balls, is going to dictate how long they last,
and how long the diff ring lasts. And also, I believe,
how smooth the diff works.

If you run 3 or 4 balls, as Pat pointed out, you can certainly
get the same lockup.
However... it is, and always will be a friction thingie.
To get 4 balls to give you the same lock up,
the groove in the diff rings will have to be deeper, to get the
same amount of total surface area ratio between balls and rings
(the friction part)..

But keep in mind.. if you use 3, for example, the balls are now
doing two jobs.
Making the diff work, AND trying to make a groove in the hard steel rings.
(the smoothness part)

So as mentioned earlier...
Two men can carry a safe up a hill.
Four men can do it easier.
8 men can not only do it easier,
but more times in a day...

For now.. I'm sticking with 12.

At least 6 balls to finish a race.
2 balls to win.

At least 6 balls to finish a race.
2 balls to win.


My favorite sticker

"RACING ... All other Sports take just ONE BALL"