Badger5

The vented shock caps make it very easy to bleed the shock when building them, don't think there is a performance advantage.

motorcitymatt

iTrader: (3)

So I finally managed to cobble together a ball diff for my KF2 to compare it to the gear diff on our local medium bite clay track. It seems the current trend in thought is: lower grip surfaces = ball diff

While I have quite a bit to say on this topic I thought you all might be interested to know that there is a substantial weight difference between the two assemblies. Most people assume that gear diffs weigh more and that may be true for some kits/manufacturers. Here are my findings for the Schumacher diffs:

• Ball diff assembled w/ Carbide Balls (U2459) - 40.5g
• Gear diff assembled w/ 3000 cSt CoreRC fluid - 30.5g

While difficult to measure I wonder if having an extra 10g of weight right over the rear axle noticeably changes the handling characteristics of the car? Could this be part of the reason why many people "prefer ball diffs" on lower traction surfaces?

And for guys looking to shave 10g of overall rotating mass from the drivetrain for stock class racing, maybe a gear diff should be on the list of things to try?

joeymdz

iTrader: (13)

Other than the weight comparison did you run the BALL DIFF vs the gear diff at your track?

Because a ball diff is 100 times better in a lose grip track scenario. even if you put 50wt in a gear diff it is not the same as a ball diff.

There are tons of write ups on the subject but if you have both try them and see which one best suits you and your style of driving. Im a huge fan boy of gear diffs... but you cant beat the feel and performance of a ball diff on a lose track

cokemaster

iTrader: (18)

Has anyone used the new Diff O-Rings, U4712? There is an extra set of O-rings that I do not know where to use?

motorcitymatt

iTrader: (3)

I actually did for the first time with this car a couple of days ago. Unfortunately I didn't have much time with it and I have been experimenting with other aspects of the setup that made the car pretty bad during this session so it was hard to see the differences through the "mud". I originally had gone out to try a lower roll center in search of a little more grip in the corners but I think I overdid it. I changed to a 1-dink plate and 1mm above the ball stud (stock is 2-dink with 3mm). This made the car roll so much (in combination with 300 cst and white 1.8 springs) that it was just too sloppy in the infield. I had to wait so long for the car to square up before I got on the throttle (to keep it from spinning out) it just wasn't worth it.

I had time to either try putting the roll center back to where it was or try the ball diff. I put the ball diff in (took out a gear diff with 1k) and it seemed to help a little but it was not a night and day difference. I think I preferred the car with the ball diff because I could get on the throttle a little more out of the turn. However, the car was so bad in this regard because of the roll center adjustment I think I am going to have to wait and see how it goes after I get the rest of setup straightened out.

Like you pointed out, much has been said about the pros and cons of ball/gear diffs in other threads. My intent is not to spark another debate like the ones that typically unfold in those threads. They usually devolve into flame wars because at the end of the day it really is subjective unless you do some serious and time consuming testing to show the benefits of either on a particular track/car/combined setup.

Like you I prefer gear diffs primarily because they are legitimately tunable. And in the case of the Schumacher diffs they are substantially lighter. I really want to make it work with the gear diff but am more than willing to use the ball diff if it helps me get around the track faster of course.

Anyway, I'm going to have a lot more time this coming week to experiment with it some more and I'll share what I find here.

motorcitymatt

iTrader: (3)

I bought a U4712 set and was wondering the same thing. I have not looked into it but I suspect the larger o-rings fit the outdrive holes of a different housing and they just put the o-rings in for both and share the part number.

The guys at DiscountRCStore would probably know for sure.

hacker

iTrader: (141)

There was quite a lot of drag on my KF with the shorty setup even with the belts setup as loose as possible!

I would imagine this KF2 to be no different and not the best car to use for stock class.

NWracer77

iTrader: (1)

no drag at all in either of my KF2's

Tony Newland

iTrader: (53)

There's quite a few guys running them in stock and doing quite well.... well enough they run mod also and place well. Something is wrong with your car

motorcitymatt

iTrader: (3)

Tony do you know if the guys you know who are running the KF2 in stock and doing well are running the carbon fiber chassis or not?

I am running the stock aluminum chassis with a 203g shorty pack and my car weighs in at a pretty chunky 1635g.

Tony Newland

iTrader: (53)

They run both chassis'

The carbon is about a 60g weight savings... but either way theyre not running the front stiffeners, side dams of battery holdowns... servo tape the battery in and I think theyre weighing in around 1510-1550g

motorcitymatt

iTrader: (3)

Interesting. I never thought of eliminating the stiffeners along the side. Now that Schumacher just released a carbon fiber upper brace for the KF2 (similar to what was on the KF) it might be an alternative if you didn't want to give up the stiffness.

Getting rid of all those chassis parts, swapping in the carbon fiber chassis plus some titanium turnbuckles should probably get me where I need to be.

Thanks for the tips.

Tony Newland

iTrader: (53)

np

motorcitymatt

iTrader: (3)

So I just removed those parts and weighed them all together. 59g

The big surprise to me were the side dams. 13g a piece! The aluminum stiffeners were another 7g, so 20g a side.

So just between this and the CF chassis I should be able to get to around 1520.

Anyone have a rough idea of what going to titanium turnbuckles is worth on this car? (Or any of the other recent Cougars)

Tony Newland

iTrader: (53)

Not sure... probably 10g or less I would guess.... Going light on paint is also a big gain... paint adds up surprisingly

Subtract the battery holdowns and your right at the weight limit