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Old 02-23-2005, 04:03 PM   #14686
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Default Re: Re: Re: Re: steering ackerman & rear block

Quote:
Originally posted by afm
You are forgetting that RC is also affected by setting of the position of camber links...read my post a couple of pages back.

AFM
Ok, I read that in the past.
Now
How is possible that "c" is better for low traction conditions?

For me:
With "A" we are lowering the rear roll center = More roll and more traction

With "C" we are raising the rear roll center = less roll and less traction
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Old 02-23-2005, 04:05 PM   #14687
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[QUOTE]Originally posted by cdelong
You guys all need to buy the XXX Main setup book. Next to a temp gun, it's the best R/C investment you will make- probably better!

It goes like this- normally the RC (roll center) is below the CG (center of gravity). How much roll (traction) you get depends on the distance between the two. The farther away the RC is from the CG the more roll and more traction you will get. If the RC is very close to the CG- your car will roll very little- just as you would expect to need on high traction set-ups with the A- blocks.

Now having said all this, I'm wondering what the 4mm, 5mm and 6mm numbers means next to the A, B and C block's on the setup sheet.

Could someone measure the distance between the centerline of the holes in the A block and the top of the chassis? I'm curious. I would measure, but I'm waiting for my stuff to be shipped back from FL. If the A block holes are 4mm above the chassis I'm really going to be confused, because that means the others are 5mm and 6mm above the chassis and "should" have less roll cause the RC would be lower in relation to the CG.
.
Now
How is possible that "c" is better for low traction conditions?

For me:
With "A" we are lowering the rear roll center = More roll and more traction

With "C" we are raising the rear roll center = less roll and less traction
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Old 02-23-2005, 04:28 PM   #14688
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Quote:
Originally posted by cdelong
You guys all need to buy the XXX Main setup book. Next to a temp gun, it's the best R/C investment you will make- probably better!

It goes like this- normally the RC (roll center) is below the CG (center of gravity). How much roll (traction) you get depends on the distance between the two. The farther away the RC is from the CG the more roll and more traction you will get. If the RC is very close to the CG- your car will roll very little- just as you would expect to need on high traction set-ups with the A- blocks.

Now having said all this, I'm wondering what the 4mm, 5mm and 6mm numbers means next to the A, B and C block's on the setup sheet.

Could someone measure the distance between the centerline of the holes in the A block and the top of the chassis? I'm curious. I would measure, but I'm waiting for my stuff to be shipped back from FL. If the A block holes are 4mm above the chassis I'm really going to be confused, because that means the others are 5mm and 6mm above the chassis and "should" have less roll cause the RC would be lower in relation to the CG.
I havent looked yet but is it possible the 4, 5 and 6mm are the distance between the CG and RC with the different blocks with the default camber link set up. That would make sense for sure. Like you say, the further below the CG the RC is the more roll you will get. Going to be looking at the car more tomorrow so will check up on this.
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Old 02-23-2005, 04:56 PM   #14689
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Quote:
Originally posted by cdelong
You guys all need to buy the XXX Main setup book. Next to a temp gun, it's the best R/C investment you will make- probably better!

It goes like this- normally the RC (roll center) is below the CG (center of gravity). How much roll (traction) you get depends on the distance between the two. The farther away the RC is from the CG the more roll and more traction you will get. If the RC is very close to the CG- your car will roll very little- just as you would expect to need on high traction set-ups with the A- blocks.

Now having said all this, I'm wondering what the 4mm, 5mm and 6mm numbers means next to the A, B and C block's on the setup sheet.

Could someone measure the distance between the centerline of the holes in the A block and the top of the chassis? I'm curious. I would measure, but I'm waiting for my stuff to be shipped back from FL. If the A block holes are 4mm above the chassis I'm really going to be confused, because that means the others are 5mm and 6mm above the chassis and "should" have less roll cause the RC would be lower in relation to the CG.
Or if you don't have access to the xxx Main Setup Book, you can go here: http://home.tiscali.be/be067749/58/ and under suspension there is a complete explanation off RC, CG, etc. etc.

With Regards to measuring distance, I did and the C blocks, which I have installed in my car, have centerlines 6mm above chassis.

Now on a direct consult with official Mugen driver in Japan, he commented that for tracks with good grip they use A blocks, and B and C blocks as traction decreases He also commented that they sometimes combine these blocks to modify anti-squat.

Also that these blocks modify dynamic roll center and camber variation in combination with upper link position as suspension works along turns, so roll center varies, it is not static.

AFM
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Old 02-23-2005, 05:32 PM   #14690
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As soon as anyone starts talking roll centre I pretty much stop listening, this theoretical point in space constantly varies it's position and can at times be located an infinite distance from the car. Now, the Universe is actually spacially finite and I fail to see the relevence of a point outside of the observable Universe.
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Old 02-23-2005, 05:43 PM   #14691
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Like I said- if the C block measured 6mm I would be totally confused.

I am.....

The lower the lower arms are in the chassis, the more roll you "should" have. I will ahve to take this to the Mugen forum and ask Robbie Collins for more insight.
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Old 02-23-2005, 05:56 PM   #14692
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this is gonna be hard to explain but every body knows when the bite comes up most of the traction roll issues come from the front. if you stay with the rear higher roll center it will let the rear stay flat but coming in to the corners if the rear is too stiff it will actually dump or over power the front and cause traction roll. you should be able to just read what your car is doing. if you look at what they are doing on electric carpet racing you'lle see that they actually lower the roll center and adjust spring rates.
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Old 02-23-2005, 07:45 PM   #14693
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[QUOTE]Originally posted by cdelong
[B]Like I said- if the C block measured 6mm I would be totally confused.

I am.....

The lower the lower arms are in the chassis, the more roll you "should" have.

Like Josh told us at the Nats. 2004, make the car a little bit lazy in the corners and it wont roll over. Soften the car up, Lowering the rear pins will let the car roll more, but it will make the car a little bit lazier to react.
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Old 02-23-2005, 09:01 PM   #14694
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Guys, I believe this was already debated sometime back... It's true that the Mugen factory drivers run "differently" from what should be run on high and low traction tracks with regards to the rear blocks...

As to which block gives higher and lower RC, hope these diagrams posted by Mike D previously on this thread will put all doubts to rest...





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Old 02-23-2005, 10:09 PM   #14695
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Okay, so which rear block gives me the highest grip ? A, B, or C ?
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Old 02-23-2005, 10:26 PM   #14696
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I read Hudy Set Up book :

A block : more roll , more grip
B block : neutral
C block : less roll , less grip

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Old 02-24-2005, 04:54 AM   #14697
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Quote:
Originally posted by cdelong

Now having said all this, I'm wondering what the 4mm, 5mm and 6mm numbers means next to the A, B and C block's on the setup sheet.

Could someone measure the distance between the centerline of the holes in the A block and the top of the chassis? I'm curious. I would measure, but I'm waiting for my stuff to be shipped back from FL. If the A block holes are 4mm above the chassis I'm really going to be confused, because that means the others are 5mm and 6mm above the chassis and "should" have less roll cause the RC would be lower in relation to the CG.
For the rear blocks, the distance between the centre of the hinge pin and the top surface of the chassis goes like this:

A block = 4mm
B block = 5mm
C block = 6mm
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Old 02-24-2005, 05:10 AM   #14698
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Part of the reason that a softer setup will help to stop traction rolling is that the more the car rolls on a car will little droop, the more the chassis is pulled down to the ground effectively lowering the CG. A really stiff car does not roll enuff to pull the chassis far enough down. This of course is only part of the story.
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Old 02-24-2005, 05:52 AM   #14699
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Too much emphasis on this roll centre thing and not enough thought about Archamedes ( my Greek sucks) theory of levers.
The rear blocks all work and the difference in practice is slight. I think differences in the arc scribed by the arm with the different blocks and the relationship to the arc scribed by the camber link are what matters. When we describe a change made to a settup can we start refering to the actual part that was changed, I'm getting sick of hearing guys avise others with terms like "Just lower the roll centre man." It makes more sense to say things like "shorten the camber link" or "raise the A arm pivot" I don't take a computer to the track and I don't have a program for determining roll centre.
Where is the roll centre when 1G is applied the the side of the centre of gravity?
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Old 02-24-2005, 06:03 AM   #14700
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Quote:
Originally posted by jwf_frani
this is gonna be hard to explain but every body knows when the bite comes up most of the traction roll issues come from the front. if you stay with the rear higher roll center it will let the rear stay flat but coming in to the corners if the rear is too stiff it will actually dump or over power the front and cause traction roll. you should be able to just read what your car is doing. if you look at what they are doing on electric carpet racing you'lle see that they actually lower the roll center and adjust spring rates.
Hmmm, yes . . . and since the front and rear roll centres are "connected", presumably the carpet guys lower the rear roll centre in order to limit the weight transfer to the front, yeah?
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