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Black RX
2013.08.20, 05:53 AM
hi,

sorry for the noob question :D

i made similar thread int he part in hop up section but nobody answer T.T. probably i posted it in the wrong section.

so can anyone explain what is the purpose of using ball diff on the rear ? i see almost everyone use them but i dont know the purpose of using it.

i do know the purpose of using LSD ( limited slip differenttial ) which is to limit the difference of rotational speed between left and right rear tires.

so does the ball diff have the same purpose with LSD ? can anyone also explain how ball diff work ?

or in what situation i need LSD and in what situation i need a ball diff on the rear ? :D

thank you in advance

color01
2013.08.21, 12:42 AM
The LSD that most people sell is a modified gear diff, which limits one wheel from spinning (good) but can also cause both wheels to spin (bad).

If you're a good enough driver you can pull off absolute faster lap times with a gear diff, but because a (properly tuned) ball diff will slip the balls instead of the tires, for 99% of drivers a ball diff will provide more consistent acceleration, and therefore faster laps overall.

Do you drive RWD or AWD? AWD can use gear diff/LSD all around similar to 1/10 touring cars, you mash the throttle and the car fires out of a corner. For RWD, for anything more than "Stock"-class power (50t motor probably being the upper limit on power) I would strongly suggest a ball diff to make the car easier to drive. I tried to develop a gear diff setup for RWD Modified but I always had trouble consistently putting down power on corner exit. I did, however, occasionally match Mr. World Champion's lap records at RC Kenon. ;)

Black RX
2013.08.21, 06:28 AM
i use RWD Mni-Z MR-02 with X-Speed motor :)

i dont have AWD at the moment, but im planning to get ma-010 or ma-015 int he future.

so, you said that a properly tuned ball diff will slip the balls instead of the tires, does that mean ball diff works like traction control on real cars ? it limits the amount of torque delivered to the tire by transferring the excess torque to the balls instead to the tires ?

this also mean that ball diff reduce the braking force when you use the brake right ?

this means its not really equivalent to LSD right ?
since as far as i know LSD only limit the torque difference between left and right, but the total torque still the same.

does ball diff also limit the difference between left and right tires ?
for example in case of body roll and only left or right tire lost contact with the surface with stock diff, all the torque from the motor will only be delivered to the wheel that lost contact with the surface. Do ball diff also give solution to this problem ?


sorry for the lot of question :)

color01
2013.08.23, 10:53 PM
Theoretically yes it's still an LSD; in practice a ball diff tends to slip without differentiating, and when it does slip the balls, the torque transferred is whatever the frictional force value is between the particular disk and balls that are in the diff. That's part of why building a good ball diff is such a time-consuming task, you need to prep the balls and rings very consistently to ensure that you're getting equal slip left and right.

When the tire slips before the ball diff, it behaves like an open diff as it is built like one. Not too much you can do about that, though PN does make a clever spur gear (my personal favorite to use) that catches the balls when you hit the throttle, keeping them from turning = making it harder to diff out on-throttle, while preserving the slip and free-spinning action of a normal, well-built ball diff.

Black RX
2013.08.24, 09:25 AM
i see, thank you for the explanation :)

have you tried both ball diff and LSD ?

can you tell me the difference between them in case of handling feels ? :D



and also, right now i still use stock gear diff for my MR-02, i sometimes got over steer on corner entry after a long straight, and while throttle near the corner exit at small radius 90-180 degree turn.

i am thinking to change my stock gear diff with a ball diff or the new atomic LSD.

any recommendation ? :)

color01
2013.08.27, 10:41 PM
I actually haven't had a chance to use a purpose-build LSD, only a converted gear diff with grease. The difference is exactly as I described, the ball diff allows for better turn in and slips upon applying power, whereas the LSD turns in less well, and applies more power on exit. Works OK for Stock class but it's way too much power transfer for Mod. :)

I would learn to tune the ball diff first, it's the easiest one to live with.

Black RX
2013.09.02, 11:42 AM
i see

thank you, i think im gonna try with a ball diff :D

scoobyrs25
2014.07.12, 11:13 AM
Theoretically yes it's still an LSD; in practice a ball diff tends to slip without differentiating, and when it does slip the balls, the torque transferred is whatever the frictional force value is between the particular disk and balls that are in the diff. That's part of why building a good ball diff is such a time-consuming task, you need to prep the balls and rings very consistently to ensure that you're getting equal slip left and right.

When the tire slips before the ball diff, it behaves like an open diff as it is built like one. Not too much you can do about that, though PN does make a clever spur gear (my personal favorite to use) that catches the balls when you hit the throttle, keeping them from turning = making it harder to diff out on-throttle, while preserving the slip and free-spinning action of a normal, well-built ball diff.

Any idea what this gear is called? Searching the Kenon site can be a pain.

cowboysir
2014.07.12, 09:25 PM
PN racing 2wd delrinmachine cut limited slip diff spur gear. As far as I recall they only make it in 64 pitch. You'll find it in the mr03 drivetrain parts section