PDA

View Full Version : Ball Differential


JDV28
2010.07.05, 11:57 AM
Im looking for a ball differential for my 03, but I dont know what companies make good differentials. At ReflexRacing they have Atomic, 3Racing, and Kyosho.
Thanks in advance.

Half
2010.07.05, 12:11 PM
I don't know but I guess that ReflexRacing has its own differential too.
you should look to a very light shaft plus robust and durable rings.
I can't advice you on how to buy cuz I've only ran with one since I bought and never tried any other. The advice I can give is to do a search here on the forum cuz I'm pretty sure someone did a comparison between some ball differentials some months ago, of course it should be out of date now with a couple new ones that came out, but some are still top notch products.

JDV28
2010.07.05, 12:17 PM
I did see a few of the extra light differentials, but I dont think there were any made by reflex, I will look again though. Also, I couldnt find any comparisons of diffs here.

cowboysir
2010.07.05, 12:48 PM
ReflexRacing has some really nice parts from themselves and Qteq in combination of some lightweight parts from PN that'll make a really nice lightweight diff that has smooth action. It'll be spendy but worth it....

Otherwise, read up on some interesting diff comparisons from pinoyboy or christian tabush.

JDV28
2010.07.05, 12:58 PM
I dont want to assemble it myself. I want it completely ready to use.
and I still cant find any of these comparisons.

SAGISI
2010.07.05, 01:05 PM
Best assembled ball diff is pn lightweight v3! Little heavier then a qteq/pn diff setup but for the price it's awesome! When you take it apart for a rebuild replace the spur with a reflex racing v2 spur and your set.

JDV28
2010.07.05, 01:09 PM
Thats the kind of answer I am looking for! Could you link me to somewhere that has it? I cant seem to find anywhere
edit: is this it http://www.rckenon.com/public_html/shop2/catalog/product_info.php?products_id=4924

SAGISI
2010.07.05, 01:35 PM
The link you provided is not the 64pitch version. Here's the one you should get:

http://www.rckenon.com/public_html/shop2/catalog/product_info.php?products_id=4858

-Comes with 9 tooth to 14 tooth pinions.

And heres the link for reflexracing v2 spur:

http://www.reflexracing.net/proddetail.asp?prod=RX1154

JDV28
2010.07.05, 03:11 PM
Thanks! I will be ordering them within the next week. I dont fully understand how the teeth work, like the different numbers of them and how the different teeth affects the car. If its not too much trouble would you explain it to me?

Half
2010.07.05, 03:41 PM
the number of teeths on the pinion will differ the gear ratio.
Low number of teeth the higher the acceleration is (and of course, speed is reduced compared to higher number of teeth) and vice-versa.

It depends on track layout and your own preference on what to use at a given stage. I would recommend to start with a pinion like 12 if you're using a stock motor, then progress through experimentation.

JDV28
2010.07.05, 04:12 PM
Thank you for explaining that. So is 12 like the middle/stock?

Half
2010.07.05, 04:25 PM
So is 12 like the middle/stock?

Nop not exactly. Just an indicator I think that it will perform better that way, and it's better to start from there.

Be advice, as any ball differential you'll use to be more stick or less stick on your likes on how in acts when rotation (I mean the friction it generates), they usually come very loosen so if you install it and the power ain't going to the wheels (instead the differential will mainly "slip") you need to tighten it.

if you go to the pn one, watch the black delrin piece thats on the side of one ring. that has a small hole, which you use (like a clip or so) to rotate it clockwise (like closing).

JDV28
2010.07.05, 04:54 PM
What does rotating that disk do? Tighten it so it doesnt slip?

EMU
2010.07.05, 04:55 PM
I try to look at the RPM that the motor puts out, and try to gear according to that. A high RPM motor I will gear much lower than a low RPM motor.

The size of the track is a big factor in gear choice as well as motor choice. When I choose my gearing, I want to top out in the middle of the longest straight. This gives me the best balance of acceleration to speed.

Lower gearing (more acceleration), gives more drag brake as well. So when you come off the throttle, the car will slow down faster. With high gearing, the motor doesnt slow down the car as much. If the car gets a little loose when you come off the throttle, but feels good everywhere else, you may want to try a pinion with one more tooth to see if it will help balance the car, so long as it still feels good throughout the track, and still tops out on the longest straight.

Lower gears use less batteries, since you arent accelerating as much. You get up to speed faster, and there is less strain on the motor. So if you dont make runtime, you can gear down a little and it will help.

When I adjust my differential, I do so on the track that I am racing. I push the car backwards, let go, then stab the throttle. If the motor spins up, and doesnt move forward right away, the diff is slipping. If the car moves forward as soon as I hit the throttle, it is too tight. I want the diff to slip just a little bit before it catches. When the car is moving, it wont slip, but will when I push it in reverse then hit the throttle. This makes the differential set to the grip that the tires have on the track that is being raced. Every track and set of tires are slightly different, so I adjust the differential each track I go to. Occasionally the track conditions change during the race day, so I test every practice to make sure that the diff tension is appropriate for the current conditions. Remember, the diff tightens a tiny bit as it warms up, so diff tension will change ever so slightly from the start of the run to the middle of the run, and try to setup for that. Another reason why I like a tiny bit of slip at the start of the run...

JDV28
2010.07.05, 05:25 PM
So on a track with alot of long straights, a higher ratio would be better, and on a track with more turns and short straights I would want a lower ratio?
Also, is it true that have a 9T pinion creates a larger ratio than a 10T?
I have been reading through this http://home.scarlet.be/~be067749/58/c5/index.htm

also, the motor i will be using is a PN 70t spec motor.

Half
2010.07.05, 06:10 PM
So on a track with alot of long straights, a higher ratio would be better, and on a track with more turns and short straights I would want a lower ratio?
Also, is it true that have a 9T pinion creates a larger ratio than a 10T?
I have been reading through this http://home.scarlet.be/~be067749/58/c5/index.htm

also, the motor i will be using is a PN 70t spec motor.

yes you get that right.
also 9T will give you larger ration indeed.
I use a pn70t and with a fast layout I usually use 13T. It depends alot on driving style, if you're able to keep the speed in corners or if you prefer a fast in fast rotation and banged out style put one or two tooths down.

JDV28
2010.07.05, 06:27 PM
Thank you very much for clearing all of that up!

EMU
2010.07.05, 08:41 PM
The smaller the ratio number, the higher the speed/less acceleration.

The following image is a compilation of a few different gear charts. I use it as my desktop, so I can easily figure things gear ratios. One thing to take into consideration, is rollout of the wheel. Basically, the larger the driving wheel, the faster the car will go, and you may want to try a slightly higher ratio/lower gearing. I tend to use the term gearing rather than ratio, higher/lower (tall/short) gearing. Ratio is a little backwards, where a higher ratio is more accel/less top speed...

The upper left is for 2wd, right and bottom left is AWD.
http://mini-zracer.com/forums/attachment.php?attachmentid=30162&stc=1&d=1278380428

JDV28
2010.07.05, 11:41 PM
That diagram is a bit to detailed for me. I now have enough knowledge to adjust the ratio on my car to fit different situations and my driving styles, and for that, I thank each of you that helped.

JeremyC
2010.07.06, 01:29 PM
Ball differentials are tricky to get working properly. If setup correctly your car is much easier to drive, but if done wrong the car is erratic.

This advice goes for anything really, but until you are experienced yourself you should always have someone else check over your car to make sure it is operating correctly.

For the ball diff specifically you should check a few things:

If you hold one wheel still and spin the other; everything should be smooth
Hold the other wheel and spin; should still be smooth
Spin both wheels in the same direction, and there should be no binding(other than the motor magnets holding it back)
When you wiggle the axle there should be a small amount of slop, but only enough slop to allow the axle to spin freely.


The next issue is adjusting your ball diff. In general you want it on the lose side. In my experience a slightly lose diff is better than slightly tight. That means you should notice a slight slip when accelerating hard from a standing stop, but only slight slip, and only with aggressive acceleration.

Good luck.

ChiMiniRc
2010.07.06, 04:21 PM
Would this diff be useful for his MR-03? mR2045 Ceramic diff.

http://i280.photobucket.com/albums/kk193/Greg_Zielinski/sell1.jpg
I happen to have a new one I'm not using.

JDV28
2010.07.06, 04:40 PM
Thank you Greg, however there is one online that I specifically like because it comes with pinions 9-14t

ChiMiniRc
2010.07.06, 08:15 PM
No Problem.