Roll Centres
#1
Roll Centres
low or high settings? Thanks
#2
Tech Fanatic
iTrader: (10)
Join Date: Apr 2006
Location: Sydney, Australia. St Ives RC Club.
Posts: 961
Trader Rating: 10 (100%+)
#3
whats the difference between high and low in asphalt indoor? right now i dont have the time to do runs cause im busy.
#4
Have you tried asking in the forum for your particular car.
Skiddins
#5
Tech Fanatic
iTrader: (10)
Join Date: Apr 2006
Location: Sydney, Australia. St Ives RC Club.
Posts: 961
Trader Rating: 10 (100%+)
Check out this website:
http://users.pandora.be/elvo/
and look under "Suspension". Roll center is in chapter 2.3
#6
Super Moderator
iTrader: (239)
a high roll center will keep the car rolling(leaning)making the car react faster and have more traction, a low roll center allows the car to roll more and react slower reducing responsiveness in and out of the turns. On low bite asphalt tracks with rubber tires run a high roll center
#7
@B4bandit
thanks for the link.
@MarcosJ
theoretically the smoother/high bite the track is i can go low on roll center? okay i guess its about time to hit the tracks.
Thanks everyone.
add more tips if you like.
thanks for the link.
@MarcosJ
theoretically the smoother/high bite the track is i can go low on roll center? okay i guess its about time to hit the tracks.
Thanks everyone.
add more tips if you like.
#8
Smoother, high bite tracks (eg. carpet) allow for a higher roll center. The more traction the higher the roll center you can get away with. The less traction the more you need the chassis to roll to achieve the grip you're looking for.
Testing it is the best way to see the effects of roll center settings. I was surprised at the difference a tiny roll center adjustment can make.
#9
I think he meant to say "a high roll center will keep the car from rolling"
Smoother, high bite tracks (eg. carpet) allow for a higher roll center. The more traction the higher the roll center you can get away with. The less traction the more you need the chassis to roll to achieve the grip you're looking for.
Testing it is the best way to see the effects of roll center settings. I was surprised at the difference a tiny roll center adjustment can make.
Smoother, high bite tracks (eg. carpet) allow for a higher roll center. The more traction the higher the roll center you can get away with. The less traction the more you need the chassis to roll to achieve the grip you're looking for.
Testing it is the best way to see the effects of roll center settings. I was surprised at the difference a tiny roll center adjustment can make.
Just think about it this way, when the camber link is less parallel relative to the arm, you have a higher roll center.
When the camber link is more parallel relative to the arm, you have a lower roll center.
#11
Tech Master
iTrader: (1)
Tek, since when does more roll --> less traction? Forget for a second that the commonly toted words 'more roll --> more traction' doesn't have a solid base in vehicle dynamics study. It's just accepted to be so. You are the first person I have ever seen claim more roll --> less traction.
Guys run high roll centers in foam/carpet because there is already a ton of grip, and having a very responsive and accurate car is more important than generating a little extra grip. My 007 is much easier to drive around a fast carpet/foam sweeper with high roll centers. Also, without high roll centers, you have to run extremely stiff springs to avoid catching the outer edge of the chassis. That isn't ideal for maximizing traction, either.
Low roll centers are used on asphalt because guys want a suspension that is soft and relies on chassis roll to sustain weight transfer rather than using suspension geometry to sustain weight transfer. Using suspension geometry to do that results in high instantaneous loads on the tires and will quickly and easily put the tires beyond ideal slip angle. Frequenting the beyond-ideal slip angle leads to traction loss (understeer, oversteer, or a drift) and heavy tire wear.
I dare guess that pushing foams on carpet over their ideal slip angle isn't as bad as rubbers on asphalt, because the foam/carpet traction coefficient doesn't drop as sharply beyond ideal slip angle. Rubber/asphalt relies heavily on a static grip interaction not present in foam/carpet.
And if you don't feel like reading my vehicle dynamics and tire dynamics mumbo jumbo, just check the 007 setup sheets on teamxray.com. You'll find that carpet/foam roll centers are consistently higher than rubber/asphalt roll centers.
-Adam
Guys run high roll centers in foam/carpet because there is already a ton of grip, and having a very responsive and accurate car is more important than generating a little extra grip. My 007 is much easier to drive around a fast carpet/foam sweeper with high roll centers. Also, without high roll centers, you have to run extremely stiff springs to avoid catching the outer edge of the chassis. That isn't ideal for maximizing traction, either.
Low roll centers are used on asphalt because guys want a suspension that is soft and relies on chassis roll to sustain weight transfer rather than using suspension geometry to sustain weight transfer. Using suspension geometry to do that results in high instantaneous loads on the tires and will quickly and easily put the tires beyond ideal slip angle. Frequenting the beyond-ideal slip angle leads to traction loss (understeer, oversteer, or a drift) and heavy tire wear.
I dare guess that pushing foams on carpet over their ideal slip angle isn't as bad as rubbers on asphalt, because the foam/carpet traction coefficient doesn't drop as sharply beyond ideal slip angle. Rubber/asphalt relies heavily on a static grip interaction not present in foam/carpet.
And if you don't feel like reading my vehicle dynamics and tire dynamics mumbo jumbo, just check the 007 setup sheets on teamxray.com. You'll find that carpet/foam roll centers are consistently higher than rubber/asphalt roll centers.
-Adam
#12
I believe you meant to say that on a high bite track, it allows for a lower roll center, because you can allow the car to roll more to achieve less traction.
Just think about it this way, when the camber link is less parallel relative to the arm, you have a higher roll center.
When the camber link is more parallel relative to the arm, you have a lower roll center.
Just think about it this way, when the camber link is less parallel relative to the arm, you have a higher roll center.
When the camber link is more parallel relative to the arm, you have a lower roll center.
If you watch a well set up rubber tire car with low roll centers go around the track you can see how much more the chassis will roll back and fourth over a well set up foam tire car with higher roll centers.
I know. Sorry.
#13
Okay well then I have myself confused then. Now its all clear, somewhat.
#14
Tech Master
You can always learn the old-fashioned way,read as much as you can.Once you learn what a roll center is and how it relates to your car's center of gravity it's much easier to figure out what your car needs to handle well.Google these authors if you want to learn more, Don Alexander,Fred Puhn,Herb Adams and Martin Crisp.
#15
What would you guys recommend when it comes to running Foams on Asphalt? High or low? Front or rear?