Trying to understand ARB calcs.

[Mazur]

I have recently began researching on how to calculate ARB stiffness required and found Optimum G's formulas for doing so.

I have plugged everything into Excel to make it user friendly, but I am getting conflicting results to what my brain thinks should be happening.

The required roll rates are increasing when I increase the following: desired roll gradient, track width, CG to RC distance, tire rate, and suspension frequency.

All of those variables I would assume would lower the roll rate required since the car will tend to roll less (or in the case of desired roll gradient, less rate to reach my figure). My calculated roll rate/gradient from the ride springs reflect my thinking correctly, but not for the ARB's.

Is there something I am not getting?

[Mazur]

I have recently began researching on how to calculate ARB stiffness required and found Optimum G's formulas for doing so.

I have plugged everything into Excel to make it user friendly, but I am getting conflicting results to what my brain thinks should be happening.

The required roll rates are increasing when I increase the following: desired roll gradient, track width, CG to RC distance, tire rate, and suspension frequency.

All of those variables I would assume would lower the roll rate required since the car will tend to roll less (or in the case of desired roll gradient, less rate to reach my figure). My calculated roll rate/gradient from the ride springs reflect my thinking correctly, but not for the ARB's.

Is there something I am not getting?

[Bobby Doyle]

I would recheck your calcs. Increasing the values of everything you listed, except the CG to RC distance, would require lower-rate ARBs.

[R. Alexander]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Bobby Doyle:
I would recheck your calcs. Increasing the values of everything you listed, except the CG to RC distance, would require lower-rate ARBs. </div></BLOCKQUOTE>+1

[mtg]

One point that people have confused/missed before: the "-H" term, that is height from roll center to CoG. It's most likely a "negative" distance, thus the numerator becomes positive when you multiply the two negatives together.

[Pennyman]

Page 599-600 in RCVD also has an equation for calculating required ARB stiffness.

[Mazur]

I can't seem to figure it out. I'm going to try to calculate out by hand and see if it still comes out wrong.


I also don't have that book...yet. If someone could scan it and send it to my e-mail, that'd be awesome.

E30S50@gmail.com

[DougMilliken]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Mazur:
I also don't have that book...yet. If someone could scan it and send it to my e-mail, that'd be awesome.
E30S50@gmail.com </div></BLOCKQUOTE>

Hey!! Scanning a work covered by copyright is illegal. Scanning a book that is published by SAE (who sanction the FSAE and the related competitions worldwide) is just plain stupid. SAE actively polices their copyrights.

My father and I worked for eight years to write RCVD. If you can't afford a copy, please borrow from a library or a teammate.

-- Doug Milliken
http://www.millikenresearch.com/rcvd.html
http://www.millikenresearch.com/fsaettc.html

[BenB]

If you are designing your team's ARBs then you should definitely get a copy and read of RCVD. RCVD and the Tune to Win should be read by anybody working on the suspension for their school's FSAE team.

quote:
"Scanning a work covered by copyright is illegal"

And on top of that asking for this on a website monitored by the book's author is definitely not a good idea!

[Mazur]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DougMilliken:
Hey!! Scanning a work covered by copyright is illegal. Scanning a book that is published by SAE (who sanction the FSAE and the related competitions worldwide) is just plain stupid. SAE actively polices their copyrights.

My father and I worked for eight years to write RCVD. If you can't afford a copy, please borrow from a library or a teammate.
</div></BLOCKQUOTE>

Sorry if I affended you. I actually did end up picking up a copy http://fsae.com/groupee_common/emoticons/icon_smile.gif

[exFSAE]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Mazur:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DougMilliken:
Hey!! Scanning a work covered by copyright is illegal. Scanning a book that is published by SAE (who sanction the FSAE and the related competitions worldwide) is just plain stupid. SAE actively polices their copyrights.

My father and I worked for eight years to write RCVD. If you can't afford a copy, please borrow from a library or a teammate.
</div></BLOCKQUOTE>

Sorry if I affended you. I actually did end up picking up a copy http://fsae.com/groupee_common/emoticons/icon_smile.gif </div></BLOCKQUOTE>

Crack a Red Bull, open to page 1, and begin.

I kid. Great publication, but no way to take it in all at once when you're starting out. Picked my copy up in... 2006? I am just now starting to feel really comfortable with the majority of it.

[Mazur]

I know what you mean. As school progresses over the years a lot of things begin to make sense to you. http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Adambomb]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by exFSAE:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Mazur:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DougMilliken:
Hey!! Scanning a work covered by copyright is illegal. Scanning a book that is published by SAE (who sanction the FSAE and the related competitions worldwide) is just plain stupid. SAE actively polices their copyrights.

My father and I worked for eight years to write RCVD. If you can't afford a copy, please borrow from a library or a teammate.
</div></BLOCKQUOTE>

Sorry if I affended you. I actually did end up picking up a copy http://fsae.com/groupee_common/emoticons/icon_smile.gif </div></BLOCKQUOTE>

Crack a Red Bull, open to page 1, and begin.

I kid. Great publication, but no way to take it in all at once when you're starting out. Picked my copy up in... 2006? I am just now starting to feel really comfortable with the majority of it. </div></BLOCKQUOTE>

No kidding. I didn't get mine until '07, and still have a ways to go with it. My current recommendation is that whoever wants to do vehicle dynamics work gets it in their freshman or sophomore year, that way by the time they're a senior they'll be comfortable with it!