Zero Roll damping theory??

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77fmod
Posts: 324
Joined: July 27th, 2006, 10:20 am

Zero Roll damping theory??

Post by 77fmod »

Okay here's one to get some discussion going.. :lol:
Once again, I am confused about the zero-roll dynamics. In SOLO and with a conventionally suspended car everyone runs very little rebound in their shocks in order to attain the maximum weight transfer during extended maneuvers, i.e., 6-7 cone slaloms and quick switchbacks. I and everyone else in Vee's with Z-bars found this to be the optimum setup, also.
Now, I transfered the same setup to my Zero-roll when I built it up and it seems to work well. So, can you true chassis guru's help me understand what would happen if I increased the rebound in my shocks? Nothing? Or would it be similiar to the z-bar effects?
I am having a hard time getting my head around this and I have not found any literature to help with the understanding.

All info is appreciated..

Johnny B.
hardingfv32-1
Posts: 1014
Joined: December 1st, 2006, 8:01 pm

Re: Zero Roll damping theory??

Post by hardingfv32-1 »

The characteristics of the shock setup are the same for Z-bar and Zero-roll. If you agree that the rear jacks up in the turns, starts out with too much camber and jacks to correct camber.....Then less rebound at the rear will allow the rear suspension to reach optimum camber faster. What is the car doing in the turns? Break it down into entry, middle, and exit. The shocks can only work during entry and exit.

What type of weight transfer do you think you are trying to control: fore-aft or lateral? Rebound of the front or rear shocks?

Brian
77fmod
Posts: 324
Joined: July 27th, 2006, 10:20 am

Re: Zero Roll damping theory??

Post by 77fmod »

Thanks Brian. I should have been more clear. I am concerned with the cornering weight transfer that would occur in a slolom. In particuar, the cross corner weight transfer. Is there any? And secondarily, what happens in a steady state condition with the weights at the front... I know this is a lot to consider and I am sure that most of you guys have taken at least some of this into consideration.
Robert, I know you probably have all the graphs and vector diagrams to explain all of this.. :lol: But if you could just try to put it into terms that an old country boy might understand... :lol:

Thanks,

Johnny
jpetillo
Posts: 759
Joined: August 26th, 2006, 2:54 pm

Re: Zero Roll damping theory??

Post by jpetillo »

This is definitely a controversial subject. You may want to check out some previous threads. The bottom line is that there is lateral weight transfer at both the front and rear even with the zero roll resistance rear end. However, because of the zero roll resistance rear suspension, the anti-roll portion of the weight transfer is slaved 100% to the front tires. Regarding the dynamics of how to dial it in, Brian can answer that better. John
77fmod
Posts: 324
Joined: July 27th, 2006, 10:20 am

Re: Zero Roll damping theory??

Post by 77fmod »

Thanks guys,
That is kinda what I was imagining.. All roll resistance being at the front and very little if any cross-corner transfer..

Johnny B.
hardingfv32-1
Posts: 1014
Joined: December 1st, 2006, 8:01 pm

Re: Zero Roll damping theory??

Post by hardingfv32-1 »

I would consider a FV to be the worst possible car to autocross.

Z-bar setup provides some degree of lateral weight transfer. This setup would be the easiest to put into an oversteer condition.

A somewhat over simplified statement:

Zero-roll - In steady state, the shocks and front sway bar have nothing to do with weight transfer. They perform timing functions for the camber and toe changes that take place as the car rolls. If you can't break down what is happening, entry, middle, and exit, then don't worry about the shocks. Something like camber or toe that effects all three phases is a better adjustment option.

I think this is right
Brian
DanRemmers
Posts: 293
Joined: June 24th, 2006, 7:21 pm

Re: Zero Roll damping theory??

Post by DanRemmers »

hardingfv32-1 wrote:Zero-roll - In steady state, the shocks and front sway bar have nothing to do with weight transfer. They perform timing functions for the camber and toe changes that take place as the car rolls. If you can't break down what is happening, entry, middle, and exit, then don't worry about the shocks. Something like camber or toe that effects all three phases is a better adjustment option.
Brian
I have to admit that adjusting the front shocks on my solo vee didn't seem to make a darn bit of difference. A slight change in rear toe made a BIG difference.
robert
Posts: 177
Joined: June 28th, 2006, 7:17 am

Re: Zero Roll damping theory??

Post by robert »

Johnny,

Your wider tires (I assume), greater power, and I guess use of lower gears than just 3rd and 4th, suggests to me that your car may want a set up a bit different than a Vee, or FST.

Rather than ask what might happen with your car's shock adjustments, why not simply test them for yourself?

My guess is that you should limit suspension travel to keep camber under control, and the contact patches maxed. A side affect to that would be a car that could be run, or modified to run lower. Lower or wider translate to less lateral load transfer, and better lateral grip . . . all else equal.

Do you guys have to run a dif? Can you spin the wheels?
hardingfv32-1
Posts: 1014
Joined: December 1st, 2006, 8:01 pm

Re: Zero Roll damping theory??

Post by hardingfv32-1 »

The importance of shocks in amateur race is completely overblown. VERY few racers can break down a car's performance in turns by entry, middle, and exit. Without this info it is just endless experimenting. Is the driver, car and the track going to stay consistent for all this experimenting? At the amateur level, it is highly unlikely. After spending a lot of money, most shock improvements are usually only found in the drivers head.

With the rapid transitions of solo, shock eval is going to be close to impossible.

Brian
DanRemmers
Posts: 293
Joined: June 24th, 2006, 7:21 pm

Re: Zero Roll damping theory??

Post by DanRemmers »

robert wrote:Do you guys have to run a dif? Can you spin the wheels?
My solo vee has 85 hp and 95 lbft of torque, with zero roll, open diff, and 10" wide rear tires. It's difficult to break the rear tires loose unless they're cold or wet. When they do, it's both tires and sudden. The rules now allow a limited slip, but I'm not sure that's necessary, especially with the zero roll.

A year or so ago, I finally got my car handling fairly neutral, so I'm not changing it. It's a lot easier to drive fast when you aren't fighting the car all the time.
Lynn
Posts: 592
Joined: June 24th, 2006, 11:15 pm

Re: Zero Roll damping theory??

Post by Lynn »

robert wrote:
Do you guys have to run a dif?
We are allowed an LSD, but so far no one has tried one.

robert wrote:Can you spin the wheels?
Oh, yeah. How much depends on which gear.
69 Beach Solo Vee, #65 FM

85 Lynx B Solo Vee

71 Zink C4 Solo Vee
77fmod
Posts: 324
Joined: July 27th, 2006, 10:20 am

Re: Zero Roll damping theory??

Post by 77fmod »

Brian,
My car has had many changes incorporated into the front end since I last drove it so I really don't know what it is doing at this point. With my old Z-bar car, I could definately tell the difference in slaloms with front shock changes. However, with the zero-roll car I had not experimented with it and was just wondering whether one could expect any differences.
You may consider a vee to be the worst possible car to autocross but we continually run times that are very close to the Formula Fords and that was before they gave us 315cc more displacement and the front end changes. My shocks are rebuildable and not adjustable so I will have to wait for a test and tune weekend to really make the changes that would affect my head.. :lol:
Dan,
I don't believe that adding a LSD to a zero-roll car will give you much bang for the buck. However, I can see how it would help a Z-bar car.
Thanks to everyone who contributed.. I will keep you informed once I have some time with the new changes..

Best of luck to all..
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