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Old 11-19-2009, 12:15 AM   #16
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Did any one stop to think about rotational mass, on road cars wheather they be 1/8 or 1/10 have tires and wheels that are no were near the wieght of a buggy wheel and tire comb and if you add into the eqausion truggy wheel and tire combo's there is no way a ball diff that could handle the power that we apply to the wheels of our off road cars would be feisable for our cars.

1. The size and wieght of the tungsten or steel balls that would need too be used make these diffs would make the cars much heavier then our current kits and add a ton of drag on our drive lines increasing center drive shaft wear and decreasing fuel mileage

2. Center of gravity, this part would have to be large and bulky, so along with adding wieght to our cars we are moving the wieght higher up on the chassis and on top of this think about the increase in size of our gear boxes your going to add a ton of weight.

3. The mear size of the part wouldnt allow for correct gear ratios you wouldnt be able to design a pinion that small to allow for correct gear ratio's and still have a reliable drive line.
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Old 11-19-2009, 04:43 AM   #17
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The fact that someone in this thread is suggesting using ball diffs over gear diffs is an insult to everyone that enjoys wrenching on there cars, from racing 1/10 for many years i absolutely hate ( and im not alone ) rebuilding ball diffs, gear diffs are still messy but at lease they can hold out for a few race meetings before requiring a rebuild, and a rebuild only consists of o-rings, a gasket and fluid 99.9% of the time, cheaper, less hassle.

Ball diffs might be inside sealed Gboxes but that doesnt stop the thrust bearing from getting full of crap whether they are sealed up or not, to keep a ball diff smooth it needs to be cleaned and greased a lot more frequently than a gear diff. And on 1/8 nitro off road, the amount of maintenance thats already required means i would never option for a ball diff, if it aint broke dont fix it.

I really cant see a ball diff lasting an hour main, electrics race for 5-6 minutes and i used to refresh my diffs every 2 race meetings ( about 40 minutes of running ) and even then they werent real flash most of the time if the track was blown out. Try running qualifiers, semi`s and a main without needing to tear the car down and rebuild ball diffs... no thanks.
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Old 11-19-2009, 02:52 PM   #18
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I could definitely see ball diffs working. It's something I've thought about for years. The big question is whether or not you could get enough friction with a ball diff to create the same kind of lock up 7k oil creates. A 1/8th ball diff would certainly use ceramic balls, which are very light. The diff would also need probably 16-32 balls running on two or three different tracks. The thrust bearing would have to be a beast too. External adjustment is what would really make me interested in them though. Just imagine not having to rip your whole buggy apart and make a huge mess with oil to tighten or loosen up your diff action a bit. All you'd have to do is a remove a plug from your front or rear gear box.
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Old 11-19-2009, 04:05 PM   #19
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you would still have to pull the center diff out of the car to adjust it.
i would LOVE to see a ring a pinnion set up on a ball diff while still keeping it strong and compact enough to work in a standard bulkhead.
I think a thing woriking against a ball diff is the fact that with a gear diff if you lock up the one side the other spins twice as fast, I beilve this is why most 1/8ths are so stable.One tire grips hard and wants to send the car one way, while the lack of force on the otherside increases the wheelspeed sort of pulling the car back on a straight direction.

myself i dont adjust my diffs unless my car is doing something I really dont like on-power
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Old 11-20-2009, 02:29 AM   #20
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Default No way....

I do not miss ball diffs from the rc 10 days. great for those cars, but I work on my car enough, the parts on a ball diff are more expensive too, and in reality, the nova engine would fry a ball diff. Give it up.....
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Old 11-20-2009, 11:42 AM   #21
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Ball diffs rock!!! why the abusive posts, the dude is just posing a question, brand pimps and search nazies are one thing but getting angry at posing a question, RCtech really is full of morons.
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Old 11-20-2009, 02:34 PM   #22
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Ball diffs rock!!! why the abusive posts, the dude is just posing a question, brand pimps and search nazies are one thing but getting angry at posing a question, RCtech really is full of morons.
...because if you are abusive.....it makes you look smarter.........
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Old 11-20-2009, 05:28 PM   #23
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Old 11-20-2009, 05:48 PM   #24
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you would still have to pull the center diff out of the car to adjust it.
i would LOVE to see a ring a pinnion set up on a ball diff while still keeping it strong and compact enough to work in a standard bulkhead.
I think a thing woriking against a ball diff is the fact that with a gear diff if you lock up the one side the other spins twice as fast, I beilve this is why most 1/8ths are so stable.One tire grips hard and wants to send the car one way, while the lack of force on the otherside increases the wheelspeed sort of pulling the car back on a straight direction.

myself i dont adjust my diffs unless my car is doing something I really dont like on-power
It could work. I have been running a rekluse clutch in my crf450 for years. Its a ball bearing against pressure plates set up. It is smooth and takes a beating. I know you geniuses are going to say its not the same- but it is the same concept. The difference is centrifugal effects increase the pressure on the ball bearings for grab. I wish someone would re-engineer that- no more burned up clutches and center diffs.
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Old 11-20-2009, 08:35 PM   #25
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Im not against the ball diff idea just giving an idea why it might not be ideal, Im all for new innovative ideas and like to see something diffrent.
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Old 11-20-2009, 11:33 PM   #26
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the gear diff will always be better because the resistance to diferentiation is proportional to speed. the ball dif has a constant resistance, given by the amount of presure you apply with the cross bolt. oil has zero resistance at zero speed differentiation and it progressively goes to max with the change of velocity of each side - theoretically to infinite resistance. that gives you smoothnes, traction at low speed, high speed, etc. also it is cheaper and easier to make strong, light and reliable.

also, the amount of power put on the floor from a 1/8 scale off road is big, real big, a ball diff will be made crap in a 60 min race. brushless may have torque and power but you cannot really compare a 1/12 or 1/10 scale on road, it's a different ball game, those things weight what? 2 pounds? 2-1/2? the amount of momentum and force that a big block 21 -28 crankshaft/flywheel/clutch assembly has when a buggy lands from a big tripple will never be understood by any 1/10 brushless motor, ball diffs will simply fail. in fact off road 1/8 cars had ball diffs in the 80's and they had to change them to gear when engines started building some decent power - about half of todays? kyosho's first 1/8 scale buggies all had ball diffs, mint baja, roudy baja etc.

X
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Old 11-21-2009, 08:53 AM   #27
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^ Good points but like so many others they assume that one would simply drop a 1/10th ball diff in a 1/8th car. Remember too that the accepted standard for lubing diff balls is silicone grease, which has similar resistance properties to silicone gels as used in gear diffs, with some sort of solution to keep silicone fluids in place at the diff balls/rings the same tuning opportunities would exist.

Give tharris1959's post another read. We're talking about a 230lb/60hp motorcycle with a 150-200lb man on it and that clutch is proportionately FAR smaller relative to the size/mass/power of the bike than anything we're using in R/C.
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Old 11-21-2009, 09:06 AM   #28
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I will just say.... Because... That's all that needs to be said
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Old 11-21-2009, 02:24 PM   #29
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Old 11-21-2009, 04:14 PM   #30
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Remember too that the accepted standard for lubing diff balls is silicone grease, which has similar resistance properties to silicone gels as used in gear diffs, with some sort of solution to keep silicone fluids in place at the diff balls/rings the same tuning opportunities would exist.
That wouldn't work very well. The only good way I have seen to give a ball diff a truly adjustable, limited slip action is to use clutch like friction pads like the old Serpent pro-diff. Something like that would work, but I don't see it being better. Why use something that has at best the same performance and requires more work?
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Last edited by wingracer; 11-21-2009 at 11:36 PM.
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