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Old 05-13-2012, 10:45 AM   #3586
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Hey guys,
I have an LE and I'm looking for parts, but I would like to stay with the orange anodizing. I can't seem to find anyone that stocks them. Can someone point me in right direction please??
I just built my LE, but I did not use the orange turnbuckles.....they are avail for sale if anyone is interested....PM me.
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Old 05-13-2012, 01:37 PM   #3587
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thinking about it:

Higher RC nearest CG so the transfer weight is more "static" = less steering
Lower RC further CG so the transfer weight has more "play" = more steering
Are u talking about the rear RC ?
I was also thinkin some time ago i get the working of a RC.
But this is totaly different , i thought it was like , higher RC in the rear makes the rear more sweepy.
Lower RC more grip , and that this was the reason why drivers are lowering the RC for outdoor tracks with less grip.
And higher RC for carpet tracks with good grip.
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Old 05-13-2012, 02:20 PM   #3588
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Haha Roll center seems very confusing. Some say Lower RC gives more traction, and others says the opposite.
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Old 05-13-2012, 04:48 PM   #3589
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I think the Roll Center confusion begins because high or low is not the actual reference to the location of the hinge pin holder or the upper link.
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Old 05-13-2012, 07:06 PM   #3590
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Originally Posted by Kevin E. View Post
Are u talking about the rear RC ?
I was also thinkin some time ago i get the working of a RC.
But this is totaly different , i thought it was like , higher RC in the rear makes the rear more sweepy.
Lower RC more grip , and that this was the reason why drivers are lowering the RC for outdoor tracks with less grip.
And higher RC for carpet tracks with good grip.

yes im talking about rear rc!

lower RC and Higher RC you are "playing" with weight transfer..

on tracks that have less grip you need less support on tires, sometimes happens when you run some laps on track fine after that starts the loose rear, you are supporting to much o rear tires... on tracks that you have good grip you need to do the opposite may you need support more on tires to prevent the "overgrip".


of course this my opinion! like everyone says has many of theories about it

Ps.: Sorry my english
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Old 05-13-2012, 07:10 PM   #3591
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I think the Roll Center confusion begins because high or low is not the actual reference to the location of the hinge pin holder or the upper link.
truth!
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Old 05-14-2012, 12:00 AM   #3592
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I think the Roll Center confusion begins because high or low is not the actual reference to the location of the hinge pin holder or the upper link.

I'll take this a little further to say that its more about the amount of mass above the hinge pin. A high hinge pin has less mass (low rc) above it and a low hinge pin has more mass (high rc) above it.
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Old 05-14-2012, 03:28 AM   #3593
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Originally Posted by instigator View Post
Hey guys,
I have an LE and I'm looking for parts, but I would like to stay with the orange anodizing. I can't seem to find anyone that stocks them. Can someone point me in right direction please??
RC MARKET have some Orange parts listed,not sure if they have stock

Last edited by mcb-jet; 05-14-2012 at 03:29 AM. Reason: typo
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Old 05-14-2012, 06:43 AM   #3594
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Default Roll Center

Let me see if I can hopefully clarify the concepts behind roll center, since there seems to be some confusion and a lot of interest.

HOW TO MAKE THE RC HIGHER OR LOWER

I think the first thing to clarify here is that when you "reduce" the amount of spacers on the inboard upper links you are "raising" the roll center. This may seem backwards, but it is not. Often there is confusion around this, because for the lower A arm the opposite is true. ie. when you reduce the height of the lower A arm (inboard) you are lowering the roll center. This is a very important thing to understand. Not understanding this is most often what causes confusion in understanding roll center.

WHY DOES A LOWER RC CAUSE MORE ROLL

When you raise the roll center (RC) it is closer to the center of gravity (CG) of the car, so the side force on the center of gravity of the car has less leverage to make the car roll. i.e. the larger the distance between the CG and RC the more leverage the side force has to cause the car to roll.

To illustrate this point let's use the physical characteristics of a laptop lid. when you go to close your laptop lid, if you grab the lid near the top of the screen you have a lot of leverage to close the lid. If you grab the lid near where it connects via hinges to the keyboard you it requires more force to close the lid because you have less leverage. So the greater the distance between where you grab the lid to close it and the hinge point the more leverage you have to close the lid. It is same principles at work when comparing roll center and cg. The further apart the CG and RC is the more leverage the side force has to make the car roll.

WHY DOES MORE ROLL REDUCE THE LATERAL GRIP AT THAT END OF THE CAR

More roll cause more weight transfer to the outside tire (i.e lateral weight transfer), which reduces the overall grip at that end of the car. The reason for this is that as we increase the load on the tire by X amount we don't get the same X amount of increase in lateral grip.

There is something called the tire performance curve that says that if you were to add a 100g of vertical load you will increase the lateral grip that tire has by X. However if you were to add an additional 100g of vertical load on top of the original increase of 100g, you will increase the lateral grip by something less than X. In other words, you as the amount of vertical load increases you do get more lateral grip, but each additional 100g of vertical load increases the lateral grip by a smaller amount each time.

So for example lets assume the inside and outside tire that both at rest of 500g of vertical load and each tire is producing lets say X amount of lateral grip which when added together is (X + X) lateral grip. When the car rolls the outside tire vertical load increases and the inside tire vertical load decreases given the outside tire more lateral grip and the inside tire less lateral grip. Because of the tire performance curve the amount of lateral grip the inside tire looses (lets call this a) is greater than the lateral grip the outside tire gains (lets call this b). So a > b. and the total lateral grip generated by that inside and outside tire is (X+b) + (X-a) which is less than (X + X).

This is why as the car rolls due to a lower roll center it will produce less lateral grip.

Now as I said in a previous post a higher roll center does have a higher resistance to roll, and this higher resistance to roll does also add vertical load to the outside tire. However with our RC cars rolling so much, the increased body roll due to lower RC transfers more vertical load to the outside tire than the higher RC roll resistance does.


SO WHEN CAN THINGS APPEAR TO WORK DIFFERENTLY THAN EXPLAINED ABOVE

In a scenario where you run a higher rear roll center than the front roll center this can give the car a nose down attitude in corner entry and mid corner. This nose down attitude is transferring weight forward (i.e. longitudinal weight transfer). When you transfer weight from the rear of the car to the front of the car this gives the front tires more vertical load and lateral grip compared to the rear tires, which depending on the mix of things can give the care more steering, often on initial turn in and sometimes mid corner.

It happens more so on initial turn in because at this point the weight transfer forward is at it's greatest...however at mid corner the weight has started to transfer back towards the rear causing the car to gain more rear lateral grip and less front lateral grip.

So in other words a high rear rc and a low front rc can often produce what appears to be more steering on corner entry, but a push in mid corner, because at mid corner the weight has started to transfer back to the rear which produces a more even weight distribution between the front and the rear of the car. In this situation when the front and rear weight is more or less equal, then because the front has a lower RC than the rear, the front tires will have less lateral grip than the rear causing the car to push in the middle of the corner.

whew...that was a lot of typing.
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Old 05-14-2012, 08:16 AM   #3595
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Very well said.
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Old 05-14-2012, 09:53 AM   #3596
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Great Job Martin!
Is it advantageous to keep your front and rear roll center even or within 1-2mm of each other? I am sure that there is a point where the front and rear RC discrepancy is no longer an asset.

P.S
I hope you are getting us tons of asphalt info.
Although my car is really good outdoors right now.
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Old 05-14-2012, 04:20 PM   #3597
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Originally Posted by jag88 View Post
Very well said.
Thanks

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Originally Posted by rdlkgliders View Post
Great Job Martin!
Is it advantageous to keep your front and rear roll center even or within 1-2mm of each other? I am sure that there is a point where the front and rear RC discrepancy is no longer an asset.

P.S
I hope you are getting us tons of asphalt info.
Although my car is really good outdoors right now.
Everyone likes a different feel in their car, and high rear RC with a low front RC has a very different feel than the opposite or when the RC are fairly close. Having said that I personally do prefer the feel of the car when the roll centers are closer than further apart. I have found that when the RC get too far apart when running on high grip carpet, cars has a much higher tendency to traction roll as well. Typically once I find a balance of Roll centers I like, I don't vary the inboard upper link spacers by more than 1mm, and most often only a 0.5mm. As I shared in an earlier post for asphalt I do run a significantly higher RC both front and rear to generate more lateral grip, but if I ran that setup on carpet the car would traction roll.

I can't wait to get to the reedy race to dial in a setup for that awesome norcal track. I will be there this weekend doing some testing.

cheers.
M
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Old 05-14-2012, 04:26 PM   #3598
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Isn't it possible that your lower roll centers are generating less grip because the increased roll causes more chassis rub?
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Old 05-14-2012, 04:43 PM   #3599
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Thankx alot Martin, really appriciate this.
This is the same way i learned it and it is perfectly explaned.
Now i am getting it 100% , this is for me the most important thing of the car.
Thankx again.
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Old 05-14-2012, 06:45 PM   #3600
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Quote:
Originally Posted by Martin Crisp View Post
Thanks



Everyone likes a different feel in their car, and high rear RC with a low front RC has a very different feel than the opposite or when the RC are fairly close. Having said that I personally do prefer the feel of the car when the roll centers are closer than further apart. I have found that when the RC get too far apart when running on high grip carpet, cars has a much higher tendency to traction roll as well. Typically once I find a balance of Roll centers I like, I don't vary the inboard upper link spacers by more than 1mm, and most often only a 0.5mm. As I shared in an earlier post for asphalt I do run a significantly higher RC both front and rear to generate more lateral grip, but if I ran that setup on carpet the car would traction roll.

I can't wait to get to the reedy race to dial in a setup for that awesome norcal track. I will be there this weekend doing some testing.

cheers.
M
I liked 15.2/15.0 springs for carpet, and I tried the same setup on a barely medium bite parking lot last weekend. I wound up taking 1mm from each inner camber link, but the car was a bit pushy entry and exit, and a touch loose mid-corner. I think going to a 16/16.5 spring up front would help immensely. I can't believe that the car reacts so great to 1 or 2 setup changes going from high grip carpet to a parking lot, and still being hooked up.
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