Gear vs Ball Diff, a discussion
01-23-2008, 09:52 AM
#1
Gear vs Ball Diff, a discussion
Currently I am looking at a variety of 2wd stadium trucks, and since I have been acustomed to ball diffs for 1/10 scale, I wanted to get some opinions on how using a Gear diff that can be filled differs performance wise from a ball diffs. Advantages to each, etc.
this discussion doesn't concern gear diffs that cannot be filled.
this discussion doesn't concern gear diffs that cannot be filled.
01-23-2008, 10:33 AM
#2
Unfortunately I have not had the opportunity to test a sealed gear diff in an electric car, they just aren't available!
The only modern example I can think of is the Serpent S400 tourer which has a gear diff as an option and from reading the comments on the web it seems to work really well.
With the power available in modern electric cars I do think the ball diff is starting to struggle to cope. Some are better than others, the new 12 ball Tamiya diffs run better than the 8 and 10 ball diffs from before.
The advantage of the gear diff is zero slip, almost no wear and consistency of setting.
The advantage of the ball diff is lower weight, not really an issue in mod in my opinion though.
I'd like to see more sealed gear diffs available for electric cars!
The only modern example I can think of is the Serpent S400 tourer which has a gear diff as an option and from reading the comments on the web it seems to work really well.
With the power available in modern electric cars I do think the ball diff is starting to struggle to cope. Some are better than others, the new 12 ball Tamiya diffs run better than the 8 and 10 ball diffs from before.
The advantage of the gear diff is zero slip, almost no wear and consistency of setting.
The advantage of the ball diff is lower weight, not really an issue in mod in my opinion though.
I'd like to see more sealed gear diffs available for electric cars!
01-23-2008, 10:34 AM
#3
In my opinion ball diffs are the way to go. I have had gear (planetary) and in my cases the ball diff has better action, truer braking and takeoff and I think a quality one like in a T4 will hold up better. Just my opinion. 
01-23-2008, 10:34 AM
#4
In my opinion ball diffs are the way to go. I have had gear (planetary) and in my cases the ball diff has better action, truer braking and takeoff and I think a quality one like in a T4 will hold up better. Just my opinion.
01-23-2008, 01:20 PM
#5
The main reason i think ball diffs are used in electric and 1/10 scale in general is for precision, you cant beat the no backlash instant response of a belt drive/ball diff drive train. Compare that to a 1/8 nitro buggy driveline and see what i mean.... because in nitro you run a centrifugal clutch it doesnt show the backlash and the car is still as precise as it is ever going to be running a clutch, in electric because the power is instant and very hard hitting from so low in the rev range the less backlash helps protect the driveline ( its like preloading the driveline in a car before doing a launch at the drags, it will take up the backlash and protect the driveline from the SHOCK of the launch, ball diff/belt drive is constantly preloaded IMO ) and make the car a lot more precise.
Only downfall to ball diffs, rebuilding, wear fast and pain in the arse in general.
Only downfall to ball diffs, rebuilding, wear fast and pain in the arse in general.
01-23-2008, 01:26 PM
#6
Just to add to that as SOSIDGE mentioned, i would also like to see more gear diffs in electric, there is no reason a company cant make a graphite composite internally geared diff, this would be still light, very smooth and have not much backlash, would be virtually maintanance free and quiet. There is no need for metal gears in electric 1/10 scale as the weight isnt there and the use of slipper clutches prevents breakage. This would allow a lot more tunability with diff fluids etc. Over the very narrow range we have with ball diffs.
01-23-2008, 02:20 PM
#7
There is one very important difference between gear and ball diffs that continue to give ball diffs viability. A gear diff under load is "trying to come apart". The internal gears are pushing away from each other and binding. With a ball diff all of those forces are non existent. So while a gear diff seems like it would be stronger (it can be) it takes haevy metal parts and strong housings to counter the opposing forces of the gears against each other. They are also more bulky which would be a challenge with current 1/10th designs. A ball diff by comparison can be extremely lightweight because aside from the main diff gear and outdrives, all of the working parts are under relatively low mechanical load.
Planetary grear diffs are another option but I think they have to have bigger housings.
It would be very interesting if someone could compare how effeciently they both operate under load.
Planetary grear diffs are another option but I think they have to have bigger housings.
It would be very interesting if someone could compare how effeciently they both operate under load.
01-23-2008, 02:31 PM
#8
Ball diffs are lighter & better suited for stock aplications where drivetrain weight is a big issue. Gear diffs are better suited for high power aplications where drivetrain weight isn't as big a concern. In classes like li//bl mod you can get gobs of power & run time that will actually take advantage of these.
01-24-2008, 09:36 AM
#9
Tech Adept
Am I understanding this right? Are you talking about a trans that is pretty much locked up 1 to 1? Not having any type of slip other than your outside slipper?
01-24-2008, 10:22 AM
#10
Yes, I am talking about being able to lock down the slipper. In 2wd this isn't something you want, but in the 4wd classes you are able to acelerate harder out of the corners. It really makes a huge performance difference in classes like mod tc. In off road it will simply help to make the drivetrain more durable.
01-25-2008, 08:54 AM
#11
Tech Adept
I was thinking for 2wd there would be no advantage of it. Actually it would hurt you coming out of the corner's. Being that the trans works like a real cars limited slip. In 4wd you could always take a use a drill press and drill through the outdrives and center gear and put a small pin through it. But really I dont see how it would help having your trans lock up 1 to 1 even with a 4wd. I still think you need some slip from side to side with how uneven the tracks are. The slip that the ball diff has helps you with traction. Doing away with it would just have you spinning out every corner.
01-25-2008, 01:13 PM
#12
When you run 2wd properly you will learn throtle control. The ball diffs do not always hold up to the rigors of a high power bl motor or nitro engine if you run them in a long main. The gear diffs are simply more durable & better suited for mod li//bl trucks that can run for 30 minutes w/ high power possibilities.
01-26-2008, 01:16 AM
#13
i like my e-firestorm's sealed gear diff. i cleaned out the grease and put oil in it. it's been great so far.
01-26-2008, 09:02 AM
#14
01-26-2008, 04:36 PM
#15
Ball Diff vs Gear
Here is a different point of view. I run on a high banked carpet oval and we only run 1/18th scale. I bought my new Vendetta Stadium Truck and everyone said I would have to have to pull the gear diffs and switch to ball diffs to be competitive. I never made the change. Currently I hold the track record for this class and was the points champ of the last series. Of 18 races, I won 16. The two I didn't were the result of battery charge error (my mistake) and a snapped front axle. I also run the plastic when everyone said I had to have steel CVDs.
Normally on the start whether I am in the front or back by the time we come out of turn 2, I am in first. Gear diff is immediately pulling. This is just another type of racing and another way to use the diff.
Normally on the start whether I am in the front or back by the time we come out of turn 2, I am in first. Gear diff is immediately pulling. This is just another type of racing and another way to use the diff.