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iTrader: (2)

If geared diffs are automatically faster on carpet, why are all 12th scale cars running ball diffs?

symmetricon

iTrader: (27)

never said that, I preferred ball diff on lower traction hillbilly dirt tracks (trolling). I always found it cornered better, but on high bite, I like gear diff's since it doesn't unload as easily.....

symmetricon

iTrader: (27)

I was speaking in context to 2wd buggies. I won't pretend to know anything about 1/12 scale but I would imaging it has to do with rotating mass and weight....

symmetricon

iTrader: (27)

Some of you guys make sound like ball diff's are always better, if that's that case, why don't we see them in 1/8 offroad buggies???

Davidka

iTrader: (86)

Because the mass of the vehicle would require a very strong diff. That would require a large ball circle (large diameter diff rings) and there is not enough space to do that in the car without making for impossibly high outdrive placement. It would also be very difficult to know if your diffs were too loose over the noise of the nitro engine.

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iTrader: (2)

Not heavy at all. The answer is handling characteristics. Geared diffs push more. There's more detail out there, I won't try and remember it off the top of my head.

People haven't been able to make one that is strong enough for the application. Ball diffs don't exist in full scale racing, they're an invention for small scale RC. 10th scale is the tipping point at the moment.

symmetricon

iTrader: (27)

that's exactly my point. 1/10 wheelers are quickly reaching then point where they are not gonna be strong enough to handle the abuse. we now have mod motor putting out over 700watts peak....the power to weight ratio is getting closer and closer to an e buggy, and given the grip levels of some tracks I think it is reasonable to think a gear diff will have exclusive advantages over ball diff's ...

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iTrader: (2)

I agree with your point, but offer this counter point that new materials make ball differentials stronger than when they first came on the scene. Tungsten carbide and ceramics take more abuse than steel balls. It's all a matter of whether the abuse increases faster than the materials improve.

In Touring cars the ability to fill the diffs with different weight oils can also make them more consistently tunable. The old gear diffs that the ball diffs replaced didn't do that as well.

I think for some time yet it's going to be a combination of the track conditions and the class (chassis and motor) you are running that decides whether ball diffs or geared diffs are the go.

symmetricon

iTrader: (27)

I agree completely. I am interested with the direction Serpent is going with their ball diff, 4 x 1/8" balls instead of tiny 3/32 balls.

Davidka

iTrader: (86)

This is what the original RC-10 had (though I believe the Serpent car has more than 4x diff balls, I think that's a typo they addressed in their thread) when the diff was on a lay-shaft in the spur gear. My old Schumacher Cat (w/Trinity diff) also had larger diff balls but they were 3mm I believe, was a very long time ago.

3/32 cam about when Losi and AE (and MIP before them) shrunk their diffs to put them inside the gearbox.

1967Typhoon

iTrader: (35)

I have been using 30K for a while now on my 2wd SCT. In some parts of the track, I still get a bit of "one wheel peel" if I turn in too fast. I am going to change up to 50K next time I need a rebuild in my diff. Some of this could be fixed by suspension setup, but that will affect how my truck handles in the rest of the track. I have an insane amount of steering, so I am upping the diff weight.

My track is ultra high bite, we run clay slicks. 30K is often a starting off point for tracks like this. They make diff oil up and past 300K. 50K is thick, but not OMFG thick.

People get hung up too much on setup. Instead of experimenting with what is out there, they replicate what they see/read/hear. Make your car fast by adjusting to what it it doing. Don't try to adjust by what the fast guy is running. Because if you do, you might not ever be the fast guy. The best example I have ever seen of this is Tebo with the ribbed fronts in his 2wd buggy. NOBODY but him were using them initially. He recognized that traction was TOO high and took it on head first, whereas other drivers seemed to set up the car to try to handle all of that grip.