Traction Rolling - how to solve it
01-26-2014, 06:47 PM
#46
Dynamic weight transfer also includes the effect of roll centers.
The larger the distance between roll center and CG the greater the amount of roll.
The larger the distance between roll center and CG the greater the amount of roll.
01-26-2014, 07:07 PM
#47
If anyone is interested there is a fairly extensive thread on traction rolling with some very good tips.
http://www.rctech.net/forum/electric...n-rolling.html
http://www.rctech.net/forum/electric...n-rolling.html
01-27-2014, 11:29 AM
#49
Tech Fanatic
Thread Starter
Um my arms are as low as the can go to the chassis I am running no spacers under my camber links im trying to reduce traction because I lost .2 off a lap and other guys could make changes to take more traction out of their car I cannot as of yet this was for the 3rd and main event its just slow and has too much tracrion in general no traction rolling
I am having a hard time understanding your posts to be honest
sorry.But I will do my best....
You can have too much traction in the corner in the sense of having too much rear or too much front traction, which affects the balance. However you can't really have too much overall traction in the corners unless of course you are traction rolling.
From your setup info you provided, try adding some spacers to the inboard upper links. This will further lower you roll center, causing the car to roll more and thus loosing lateral grip.
Cheers.
01-27-2014, 11:43 AM
#50
Tech Fanatic
Thread Starter
I've been battling this for some time now and could not wrap my head around why so many folks say you must soften the car up. In my head I had always looked at traction rolling as a direct result of too much roll.. limit the roll, limit the tip. Well, it's not that simple I don't think. The physics in carpet racing is very different due to what I might call traction/weight ratio. In the 1:1 world you could stiffen the car up to the point where you limit mechanical grip enough that the outer tires slide because they don't receive enough load. We have so much grip indoors that just doesn't happen, plus the speeds we race at aren't high enough to slide the car (albeit arguably) even if it is set up stiff. I believe there is a correlation between lateral load, vertical load and traction. When grip gets really high we essentially need less mechanical grip to get the car to turn at speed. The problem I think is that in doing so (stiffening the car), we are increasing lateral load and decreasing vertical load on the tire. This is a recipe for even snappier t-rolls. Theoretically, one may be able to stiffen it to the point it is able to break traction, but now you may have a setup that is quite skatey at the limit and just difficult to drive. If you go the other direction and soften the car I think what is happening is that you are effectively decreasing lateral load and increasing vertical loading of the tire (even more mechanical grip). I think it's the balance of this loading that is important here. However, because the car is sprung softly and the roll centers are very low, the chassis has a lot of leverage and less resistance to roll so you still need to limit it otherwise it'll still tip. Now one may be looking at a bit more ARB and things of that nature. Basically, instead of looking for ways to utilize the available traction in an energy efficient manner, we may need to look for way to waste it. By keeping the car softly sprung we are creating more mechanical grip that we actually need, but the direction of the loading may be what we need to keep the car from flipping over.
a) If you can lower the CG you will reduce traction rolling
- by going softer and limiting the droop of the car, the car will roll into the carpet more which lowers the CG.
- by reducing droop on the car, the inside will tend not to lift off the ground keeping the CG lower
b) Reducing lateral grip will reduce traction folling
- you can do this in many ways....
-- lowering the roll center will allow the car to roll more, increasing the difference in vertical load between the outside tires and inside tires. My app explains this in more detail but there are formulas that explain that the greater the difference in vertical load between the outside tires and inside tires the less lateral grip you will have.
-- you can reduce the static camber on the tires
-- you can reduce the dynamic camber gain on the tires, by making the upper link as long as possible.
-- you can stiffen the swaybars, which can but not always increase the difference in vertical load on the inside versus outside tires....again leading to less lateral grip. note: I have found in practice however that overly stiff sway bars can make traction rolling worse.
-- glue sidewall...but I don't recommend this unless you have tried everything else
-- etc etc...less gippy tires...etc.
01-27-2014, 11:48 AM
#51
Tech Fanatic
Thread Starter
If anyone is interested there is a fairly extensive thread on traction rolling with some very good tips.
http://www.rctech.net/forum/electric...n-rolling.html
http://www.rctech.net/forum/electric...n-rolling.html
To help me respond,...when you say stiffening or softening the car...are you referring to the chassis stiffness? the springs? the shock oils? the roll centers?
01-27-2014, 12:48 PM
#52
Tech Fanatic
Thread Starter
Hi,
Zac sent me an email, but I thought I would post my response here just in case others get value out of it.
1) Roll Center
When you add spacers to the inboard position of the upper links you are lowering the roll centre.
When you raise the inboard position of the lower arms, this raises the roll center.
Another way to remember this is that the less vertical distance there is between the upper link and lower arm’s inboard pivot points the higher the roll center will be.
lowering the roll centre means the car rolls more and raising the roll centre will decrease roll.
Lower roll centres will cause the car to have less lateral grip.
Higher roll centers will cause the car to have more lateral grip.
2) Droop
Increasing droop will increase the chances of traction roll because the inside portion of the chassis can raise up higher, causing the CG to be higher, than with less droop.
Zac sent me an email, but I thought I would post my response here just in case others get value out of it.
1) Roll Center
When you add spacers to the inboard position of the upper links you are lowering the roll centre.
When you raise the inboard position of the lower arms, this raises the roll center.
Another way to remember this is that the less vertical distance there is between the upper link and lower arm’s inboard pivot points the higher the roll center will be.
lowering the roll centre means the car rolls more and raising the roll centre will decrease roll.
Lower roll centres will cause the car to have less lateral grip.
Higher roll centers will cause the car to have more lateral grip.
2) Droop
Increasing droop will increase the chances of traction roll because the inside portion of the chassis can raise up higher, causing the CG to be higher, than with less droop.
01-27-2014, 01:08 PM
#53
01-27-2014, 03:30 PM
#54
Two things I've been hearing lately that I haven't seen mentioned here are:
1. use of a front gear diff
2. more drag brake
I haven't tried a front gear diff specifically to reduce traction roll, so I can't comment on its effectiveness, but I can say that more drag brake has been helpful in the past. Obviously both are compromises that may or may not be worth it.
1. use of a front gear diff
2. more drag brake
I haven't tried a front gear diff specifically to reduce traction roll, so I can't comment on its effectiveness, but I can say that more drag brake has been helpful in the past. Obviously both are compromises that may or may not be worth it.
01-27-2014, 03:40 PM
#55
Two things I've been hearing lately that I haven't seen mentioned here are:
1. use of a front gear diff
2. more drag brake
I haven't tried a front gear diff specifically to reduce traction roll, so I can't comment on its effectiveness, but I can say that more drag brake has been helpful in the past. Obviously both are compromises that may or may not be worth it.
1. use of a front gear diff
2. more drag brake
I haven't tried a front gear diff specifically to reduce traction roll, so I can't comment on its effectiveness, but I can say that more drag brake has been helpful in the past. Obviously both are compromises that may or may not be worth it.
my favorite is a lighter front bar...
01-27-2014, 07:25 PM
#58
But weight transfer and chassis roll are two different things. A stiff suspension will not allow chassis roll, which leads to traction roll. A softer suspension will allow more chassis roll, and therefore reduce the chances of traction roll
Better?
01-27-2014, 08:35 PM
#59
Tech Fanatic
Thread Starter
Two things I've been hearing lately that I haven't seen mentioned here are:
1. use of a front gear diff
2. more drag brake
I haven't tried a front gear diff specifically to reduce traction roll, so I can't comment on its effectiveness, but I can say that more drag brake has been helpful in the past. Obviously both are compromises that may or may not be worth it.
1. use of a front gear diff
2. more drag brake
I haven't tried a front gear diff specifically to reduce traction roll, so I can't comment on its effectiveness, but I can say that more drag brake has been helpful in the past. Obviously both are compromises that may or may not be worth it.
The front gear diff is an interesting thing. I never really experimented with it to reduce traction rolling. Every time I tried a front gear diff the car felt smoother and easier to drive, but ultimately slower existing a corner because the front wheels are not driving the car forward as much.
I had a windows phone for a while too. But I was tired of not being able to get the apps I wanted. So back to iPhone again. Hope you are well...Cheers.
01-27-2014, 10:01 PM
#60