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Old 06-08-2004, 05:42 PM   #12766
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Nice Article on Roll centers

http://www.mytsn.com/publ/publ.asp?pid=9986

cheers...
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Old 06-08-2004, 06:01 PM   #12767
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Default MTX-3 Roll Center

Quote:
Originally posted by Unregistered
Not exactly. I'll try to explain how the rollcenters and CG all work together.

We know what the CG is and that it controls how much weight is transferred to the outside tires during cornering.

We know what the rollcenters are (front and rear), and the roll axis is an emaginary line connecting the front and rear rollcenters.

On our cars (all RC cars that I've seen) both rollcenters are below the car's CG.

Here's how they work together. The roll axis changes how the CG weight is transferred to the outside wheels. If the roll axis is level (front and rear rollcenters are the same) then the CG weight will transfer straight out (the percentage is about the same as the front to rear weight distribution). If the roll axis is more inclined (always higher at the rear) it tweaks how the CG transfers weight moving it foreward on the car giving more steering and the feel that you lose rear traction (you lose rear and you gain front).

I guess a more simple way to put it is that with the rear rollcenter raised it wants to force the front to roll more in the corner planting the RF tire more.
The following images show the position of the front and rear roll centers(A,B,C) so you can get an idea of how the position of the roll axis will change when the rear roll center blocks are changed. Obvoiusly everything like hub spacers, ride height and tire size will change the roll center, but you can see the trend when everything is kept constant and only the blocks are changed.
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File Type: jpg mtx3-front.jpg (106.0 KB, 198 views)

Last edited by Mike D; 06-08-2004 at 06:14 PM.
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Old 06-08-2004, 06:02 PM   #12768
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Default Re: MTX-3 Roll Center

Quote:
Originally posted by Mike D
The following images show the position of the front and rear roll centers(A,B,C) so you can get an idea of how the position of the roll axis will change when the rear roll center blocks are changed. Obvoiusly everything like hub spacers, ride height and tire size will change the roll center, but you can see the trend when everything is kept constant and only the blocks are changed.
Attached Images
File Type: jpg mtx3-rear-b_block.jpg (106.2 KB, 154 views)

Last edited by Mike D; 06-08-2004 at 06:14 PM.
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Old 06-08-2004, 06:03 PM   #12769
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Default Re: Re: MTX-3 Roll Center

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Originally posted by Mike D
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Old 06-08-2004, 06:04 PM   #12770
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Default Re: Re: Re: MTX-3 Roll Center

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Originally posted by Mike D
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Old 06-08-2004, 10:00 PM   #12771
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Quote:
Here's how they work together. The roll axis changes how the CG weight is transferred to the outside wheels. If the roll axis is level (front and rear rollcenters are the same) then the CG weight will transfer straight out (the percentage is about the same as the front to rear weight distribution). If the roll axis is more inclined (always higher at the rear) it tweaks how the CG transfers weight moving it foreward on the car giving more steering and the feel that you lose rear traction (you lose rear and you gain front).
Great stuff....

AND...Mike D....the figures showing graphically where the roll-centers are look almost like an excel worksheet or similar software.....WHERE CAN I GET THE SOFTWARE.....that's the coolest thing yet to this thread......HOW CAN I GET A COPY OF THOSE.....please help....

Quote:
also with the 16/19 conversion i have just been told by my mugen supplier that this conversion only works with a mtx-3 that is equipped with a front one-way diff. or can this still be used effectively on a mtx-3 with front and rear open diff?
That mugen supplier obviously does not understand the concept of the conversion.....It works GREAT with locked-diffs or regular diffs in the front....and one-ways......Has NOTHING to do with the style of front diff......give it a shot....(The cost is less than $10 and it takes about 2min or less to install......just pull-out some worn-down front tires to put about a 3.5mm split on the car.....)


Last edited by Bivens; 06-08-2004 at 10:07 PM.
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Old 06-08-2004, 10:19 PM   #12772
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Default Re: MTX-3 Roll Center

Quote:
Originally posted by Mike D
The following images show the position of the front and rear roll centers(A,B,C) so you can get an idea of how the position of the roll axis will change when the rear roll center blocks are changed. Obvoiusly everything like hub spacers, ride height and tire size will change the roll center, but you can see the trend when everything is kept constant and only the blocks are changed.
This is great info, and it completely agrees with my understanding. However I just cannot get it through my thick skull why having a lower roll centre, with more rear chassis roll, is a superior thing on a high grip circuit. My thinking is more grip, less required roll = better.....................

Mugens recommendation of the A block on fast tracks has me stumped.
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Old 06-08-2004, 10:36 PM   #12773
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Quote:
Originally posted by rjl
I'm entered for the World Championships I hope, does anyone know if I could rent a house close to the track 2/10/04-25/10/04. Also need to ship goods to someone reliable, the stuff I won't be taking with me. This will be my first WC if all goes well, wish me luck guys I will need it.
How are you....i live inBrazil near the WC track..... and yes , there are some hotels near the track 5 startars U$$35 day....if you want more information ask me on [email protected]
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Old 06-08-2004, 10:37 PM   #12774
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Quote:
Mugens recommendation of the A block on fast tracks has me stumped
I agree...I use the A-A blocks when I'm on a low-traction track that needs more rear grip mid to off-corner.....
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Old 06-08-2004, 10:40 PM   #12775
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Quote:
Originally posted by Bivens
I agree...I use the A-A blocks when I'm on a low-traction track that needs more rear grip mid to off-corner.....
Does the manual or supplementary sheets make a recommendation as to which blocks to use when?
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Old 06-08-2004, 11:37 PM   #12776
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how do you guys set the track with on your cars so that is it accurate?

when i build my 710 , serpent gave us some dimensions from the a-arm to the outside of the steering blocks..

I am having a hard time getting both sides of the car to add up tp 200 and have the same dimension on both sides.

thanks !
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Old 06-09-2004, 12:55 AM   #12777
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Default roll centre

AMGRacer the manual doesn't give any explaination on what blocks to use when. But for Brendale we use nothing but A A. The car feels no where as good with B B in the rear. And as you know at my home track there is plenty of grip even after the rain in the morning. I can't explain why we use these blocks, but the car rolling more in the corners definately feel good to me. That's just my 2 cents worth.
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Old 06-09-2004, 02:53 AM   #12778
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i dont get it.
Can someone tell me what each block dose. I now that it makes the rear arms sit up higher but what diffrentce dose this make to the car.

What dose A-A do to the car.
what dose B-B " " " "
What dose C-C " " " "

what is if for like A-A high traction tracks? Or Lower Traction tracks?


Also what steering Block gives you more or less streering A,B or C?

Thanks Guys
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Old 06-09-2004, 04:07 AM   #12779
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thanks taylor-racing and biven. Yea i will be doing this conversion ASAP! hardest thing i reakon is to get the right belt! do you guys know how many teeth this belt has? or a link to a shop online that has this belt has i cant find it anywhere in the hop-up section in those online shops.

rjl. Is the world championships held in just one track? if so where? and GOOD LUCK! that would be very exciting to attend!
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Old 06-09-2004, 05:20 AM   #12780
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ok roll centres as it really is! :

A blocks lower the roll centre. this is best suited to high bit surfaces. WHY!? Because the car centre is lowered. this means the weight transfer WILL be less onto the arms and subsequently through the shocks, and more through the chassis. ie the car will slide before it bites. (bites means the shocks reacting to the weight transfer and soaking up the weight)

B blocks is somewere inbetween

C blocks will lift the cg and roll centre at the rear. this equals to a car that shifts weight more to the arms and subsequently to the shocks. SO!? Well this means there will be less rear end sliding because the shocks are soaking up the force earlier. therefore the car grips ealier.

WHY DO THE SHOCKS REACT EARLIER WITH "C" BLOCKS AS COMPARED TO "A" BLOCKS? place your finger on the top of your shocks. push down. notice the reaction of the compression is alot earlier. this is a rough example of high cg and a C block type effect.

now place your finger near the actual block. it will take a greater force for you to compress the shocks. compression occurs later. THIS IS A "A" BLOCK type effect. the cars back end will naturally slide as it requires greater inertia for shock compression. (shock compression = grip)

DOES THIS SOLVE THE ROLL CENTRE ISSUE?
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