Spetz

Hey guys,
New member here and just got a few questions


I have a Tamiya TGX nitro car and thinking about putting front and rear "LSD's"

Can someone explain me the difference between ball and one way diffs?

Am I correct in that ball diffs are adjustable?

And that one way diffs, just allow via a one way bearing for a wheel to spin faster than the other, however not taking away power from the slower turning wheel?
If so, does this mean that brakes do not work on the axle with a one way diff?


So in the end of the day, which one is better?
I plan to put diffs both front and rear as the motor/exhaust/gearbox have all been upgraded and it does spin the inside wheels constantly

GYNAIKAS

Ball differentials work exactly the same as gear differentials but instead of gears they use 3 discs. The middle one is usally plastic hith holes where the balls are installed and the balls are a bit wider than the dics so that a small part of them exceeds the disc. The other two discs are aluminum or steel and they touch the balls one frm the left and one from the right. You "pack" the whole thing together and there's your ball differential. And yes one way diffs mean that brakes do not work on the axle with a one way diff. but while accelerating they work exactly like any other diff.

Spetz

Are the ball diffs adjustable? (tightness wise)
What are the advantages of each of these and disadvantages?

On a AWD car, is it necessary to do front and rear? Or is it a good idea to do rear only, so the rear slides out but the front catches and controls it?

GYNAIKAS

They are adjustable if you tighten the ball diffs setup screws the metal discs have more pressure against the balls so it gets stiffer. You use one way diff. ONLY to the front axle so that the front rolls gently. It needs caution cause the brake acts like handbrake (only to the rear). One way diffs help while you reduce throtle before and durng a corner and prevent oversteer when that happens cause the rear holds while engne rpm fall and the front rolls free.

Foxy

You'll never see any pro racer using a ball diff in a nitro car. Use a one-way front if you have a lot of sweepers. If your track is all hairpins, you're better off with a gear diff in the front. Always use a gear diff on the back, and use silicone oil to restrict it's movement, try 10-20 thousand to start with. I run a solid front axle in my car (no diff at all) because my track is very large and wide with a lot of fast corners. Ball diffs will also undo themselves in the course of a long nitro race.

Spetz

To be honest losing the front brakes is sort of out of the question

How long to ball diffs last for? Keeping in mind I don't want to be rebuilding the car each time I use it. And, I'll be racing it on the track by myself too.

Gear diff/ball diff is the same thing?

Now, can someone explain the advantage of using a front diff which isn't open? Wouldn't this cause understeer?

Ideally I think I would want a fairly tight rear diff so I can get the tail out but then I want the front wheels to guide the rear (ie, like when a FWD car spins, and you press throttle to straighten it)
How would I achieve something like that? And how does my theory work in practice?

Foxy

No, ball and gear diffs are not the same thing. One has balls, the other has gears.

In order to help you with what diff 'you' should use, tell us more about the track you run on. As for trying to do anything except drive as fast as you can between the white lines without crashing, I'd leave that experimentation for a while.

You can make a geared front diff very solid by packing it with a diff lock oil like 100,000, that may have a good effect for you. Certainly forget about ball diffs.

GYNAIKAS

Yeap it's a very old technology and its purpose of existance was to reduce spinning mass for better acceleration and lower weight. But the disadvantages were significantly more than the advantages.

Spetz

Foxy, why forget about ball diffs?

Gynaikas, are you refering to ball diffs?


As far as the track goes, I kind of want the car to be all round, rather than set up for a certain track... that and I couldn't really tell you anything abou the local track [&:]

GYNAIKAS

Yeap I refer to ball diffs...

Spetz

So what are the distinct disadvantages?

And when you refer to gear diff, is there a limited slip geared diff available or you guys mean by putting heaps of heavy grease into the diffs?


So, in my case what do I do? The car spins the inside wheels through corners and I can put very little power down. I don't want to lose braking power, nor constant servicing of diffs

IARacer

With gear diffs you can put silicone oil in them of different viscocities (thickness) which can make the diff move more freely or more tightened, so to compare to real cars, it would be like an adjustable limited slip diff.
I am a huge fan of gear diffs, and not a huge fan of ball diffs just from the maintenance associated with them.

Spetz

How high of maintenance are we talking about?

And how effective will the gear diff be with thick grease?

Isn't there anything like car diffs? My car has a helical diff which tightens when more torque is put through it. Anything like that for RC Cars?

Foxy

Just put a solid spool front axle or fill the front diffs with 100,000wt oil. And put 30,000 in the rear. Don't use ball diffs for a nitro car.

Spetz

What's a solid spool?
Is that like a locker diff?

And, with oil viscosity, is the higher number thicker or thinner?

GYNAIKAS

Yeap. In fact it's the lack of differential at the front. Blocked differentials work better while exiting corners at throtle.

IARacer

As for the Silicone oil, the higher the number the thicker the oil. I have seen from 5 all the way up to 200,000.

Spetz

So there is no other type of diff then?
And the most reasonable choice is to just add really thick oil?
That's pretty dissapointing


Thanks for all the help guys, I appreciate it

Foxy

What other type of diff do you want?

Ball diffs - not adjustable enough, not suitable for nitro.
Gear diffs - fine, just add oil, can be used front or rear.
One way diffs - give you corner exit speed without sacrificing turn in. No front braking. Only be used on the front
Solid spool - gives you good corner exit, sacrifices turn in, but allows you to keep front braking. Can be used front or rear.

Spetz

How come ball diff isn't suited to nitro? Don't electric cars create more power/torque?
Tamiya has a ball diff as a hop up option for my car which is nitro

GYNAIKAS

Electric cars weigh 1/2 of a nitro car. So differential's action is more important for nitro cars cause forces applied to the wheels/transmission are 2-3 times stronger than to an electric car's. In that case ball diffs are unable to transmit 100% of the power to the wheels cause the metal discs slip from the balls. This can be prevented by tightening the diffs, something that reduces their right/left power transfer wich is also wrong.

Spetz

ahhh I see
That's an interesting fact
I was wondering myself when looking at the pics/imagining how it'd work and thought it would slip but then thought I must be wrong

IARacer

I would call that a good thing rather than disappointing. Being able to change the silicone in the diff gives you the ability to adjust the diff to be loose or tight depending on your track conditions and personal preference.