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  1. #1
    Member super66's Avatar
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    Default zero roll explained please

    Hi guys contacting you here from Ireland and I am wondering can someone explain how this works and what are the benefits or does anyone know of any videos (utube,etc) that show how it works I am interested in trying to fit this on to my own Formula vee if there are benefits I know the guys in GAC in the uk have a very nice set up with three dampers being used and having read up a article about theres they say they are using this to acheive zero roll.

    I am asking this to you as you all have been leading the way when it comes to zero roll for many years.

    thanks all

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    The basic benefit of a FV rear zero roll system is to relieve the rear suspension from any roll resistant duties and thus, any additional wheel loads. This would be helpful if you required more rear grip. Our systems are usually one coil-over assembly, push rods, and rocker/bell cranks. It could be called a mono shock setup.

    After reading some of your rules, at a minimum you would be required to develop a system that uses two coil over assemblies. Other rules that I found say the shocks must be mounted directly to fixed brackets on the chassis. You need to review your rear suspension rules.

    Brian

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    Member super66's Avatar
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    Brian
    You are correct when you say that we have to use two dampers a crazy rule if you ask me, what i am trying to do is understand the idea and then if the benefits are worth it I would like to "try" and get a zero roll sysytem in place,that is one of the reasons why I asked if anyone could put up some pics/videos of their system and I can try and understand it,as they say a picture is worth a thousand words.
    Are you aware of the j damper used in formula 1 is this sonething the same as zero roll.

    thanks for your reply

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    Member Rob E's Avatar
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    Earliest versions of zero roll in SCCA had two shocks and two springs. The rules required it or someone thought that they did at that time. Ended up with a shock and spring mounted each way and mounted to one upright in the center to the aforementioned pushrods, etc.

    I may have some pictures of an adaptation that a friend of mine did to his Zink close to 30 years ago.

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    Member super66's Avatar
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    Rob e

    If you have those pics it would be great if you could post them up or send me a pm with them so I could have a look.

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    Default

    1) A j damper is not relevant to this discussion.

    2) Do the coil over assemblies have to be mounted directly to fixed chassis locations?

    3) In general, when the car is in perfect working order, what is the balance of your car, understeer or oversteer?

    Brian

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    Default

    Basically you would replace the push rods on each side with coil over assemblies and the coil over assembly in this photo (center location) with a push rod.

    Brian

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    Member super66's Avatar
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    Brian

    I will be picking up my car at the weekend and I will send you some pics of what I have but basically what we have is the same as the old formula fords in that we have a leading arm coming from the chassis to the rear axle and the damper comes from that axle up to the chassis.
    Your question about balance it would be oversteer,initial turn in is fine but on acceleration coming out of the corner I am getting the understeer.

    Thanks

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    Default A few Pics

    This is not a U.S. vee, but might work for your rules.














  10. #10
    Contributing Member lawyerbob's Avatar
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    Having just become the owner of a D-13 with the two rear shock zero-roll set-up, I'd be interested in understanding the differences, pros and cons of the two vrs one shock set-up.

    Thanks
    Bob Stack, Hartland, WI
    CenDiv - Milwaukee region

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    Short answer: Weight reduction and less aero drag. If you are running high dollar shocks there is a cost savings as well.

    The only con I'm aware of is a tiny increase in the center of gravity height, but no way is it enough to offset any of the advantages.

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    Contributing Member lawyerbob's Avatar
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    Quote Originally Posted by Daryl DeArman View Post
    Short answer: Weight reduction and less aero drag. If you are running high dollar shocks there is a cost savings as well.

    The only con I'm aware of is a tiny increase in the center of gravity height, but no way is it enough to offset any of the advantages.

    thanks
    Bob Stack, Hartland, WI
    CenDiv - Milwaukee region

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    I would find it odd that there are no zero roll setups in Ireland... IF... the rules actually allowed such a setup. Zero roll would be helpful with the over-steer issue. Of coarse we race on slicks with the rear thread being wider than the front. Are you not on one size of street radial tires? I am not sure how the use of radials effects the discussion. Being equal size would not seem a plus.

    Is your setup described as a Z bar rear suspension by the participants? Are there restrictions on what happens to ground clearance when the Z bar is disconnected? How are your rules enforced in this regard? Ideally you would want the Z bar to be responsible for all the rear spring requirements... IF... your goal is zero rear roll resistance.

    Brian

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    The last picture is of the Citation zero roll suspension system I produced for several years. It was designed by Ed Zink in late '78-'79. The original version had a shock/spring looking device that passed for the second spring/shock unit. The rules only required 2 coil spring/shock units, not identical or even functional. Some years later SCCA dropped the 2 shock rule.

    If you notice all the setups have a droop limiting device. The damper and droop limiting setups are critical. On some of the Citations I have added a very light rear anti-roll bar. The D13's used a VW steering damper to slow the roll rate. I have never worked out a roll damper for the bell crank setups but it is worth thinking about.

    Because of the VW geometry, in particular the roll center and front view swing arm setup of the VW suspension, a FV produces a very strong jacking effect in the corner. The rear wants to rise to the limit of the suspension. When a FV corners it jacks against the droop limiter and the suspension movement is a combination of bump and roll against the limiter.

    Get everything right and this system works well.

    I shipped several cars to the UK years ago. One of those cars won several championships. The cars were re-badged.

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    Steve

    1) Do you perceive any negative consequences from limiting rebound with the drop limiter? Is there an assumption that by definition when a FV hits a track irregularity it will come off it's fully jacked setting, thus providing a range of rebound motion?

    2) Why did you add a very light rear ARB? If to correct a balance issue, could this not be accomplished by increasing the grip at the front?

    Brian

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    Quote Originally Posted by Hardingfv32 View Post
    Steve

    1) Do you perceive any negative consequences from limiting rebound with the drop limiter? Is there an assumption that by definition when a FV hits a track irregularity it will come off it's fully jacked setting, thus providing a range of rebound motion?

    2) Why did you add a very light rear ARB? If to correct a balance issue, could this not be accomplished by increasing the grip at the front?

    Brian
    Rebound damping in the shock is also bump damping into the rebound limiter.

    You have no choice. The geometry is the controlling fact of FV suspension. It is what it is. You are doing several things. The rear spring has a lot of preload as it is installed. The droop limiter is part of the preload package. Preloading suspension is very common, probably more than it should be. In the case of an FV you are stuck with things that don't want to work in your favor.

    If you put a spring on the rear that would hold the car up with no preload, you would not be able to drive the car, too loose. To get some grip, you soften the spring. Then you don't have enough spring force to hold the car up. So you preload the spring.

    We added the rear ARB to help make the car react a little quicker on corner entry. It is not enough to affect the car after that.

    You can model the FV suspension in Mitchell software.

    People think of balance issues as increasing grip at one end or the other. How do you increase grip on a corner? Especially at the front of a FV. A better way to think about it is in how you load the tires one end to the other.

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    Quote Originally Posted by S Lathrop View Post

    People think of balance issues as increasing grip at one end or the other. How do you increase grip on a corner? Especially at the front of a FV. A better way to think about it is in how you load the tires one end to the other.
    While I would agree with this statement for most race cars, don't we have something to work with on the FV front end by moving to a more favorable location on the camber curve. I believe the the FV front suspension goes to positive camber under high G load cornering because of roll and component flexing. Could we not use more static negative camber to end up with less positive camber when under cornering load? Could this not improve front grip?

    Brian

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    Quote Originally Posted by Hardingfv32 View Post
    While I would agree with this statement for most race cars, don't we have something to work with on the FV front end by moving to a more favorable location on the camber curve. I believe the the FV front suspension goes to positive camber under high G load cornering because of roll and component flexing. Could we not use more static negative camber to end up with less positive camber when under cornering load? Could this not improve front grip?

    Brian
    The Lilly FV had the solution to that problem. I have built a copy and it does work. The Lilly setup solved the flex problem.

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    Senior Member Diamond Level Motorsports's Avatar
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    Default Lilly System

    Steve,

    Do you have a picture or sketch of the Lilly system? I have a basic understanding of how it works but cant remember all of the details.

    Thanks,
    Last edited by Diamond Level Motorsports; 11.12.11 at 12:11 PM. Reason: spelling
    Scott

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    Lilly FV? Alright, you gotta tell us now

    There should be a book on all this stuff.. How am I supposed to know what's been done 20 years before I was even alive? :P

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    The Lilly was from Detroit, I believe. About 1968-69 vintage.

    The front sway bar attached to an a-arm that inturn attached to the top and bottom of the link pin carrier. The force from the sway bar would apply a torque to the link pin carrier. This would counter act the torque from cornering on the link pin carrier.

    No, I don't have any pictures and I have not made a drawing. I used this setup on a car for Chuck Brewer 15 or more years ago. It showed promise but he damaged the car and he did not use the bar when he rebuilt the car. We tested that and a number of other ideas that we had seen over the years as we prepared to do his new FV that is yet to make the track. But we have the homologation papers for it.

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    Why not just add more negative static camber? Most FV's are currently no more than 1.5 negative static.

    Would a negative 2 degree front camber setting have any unusual negatives? Say under braking...

    Brian

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    Quote Originally Posted by Hardingfv32 View Post
    Why not just add more negative static camber? Most FV's are currently no more than 1.5 negative static.

    Would a negative 2 degree front camber setting have any unusual negatives? Say under braking...

    Brian

    There is a limit to how much negative you can get. And the negative does nothing good for braking.

    Finally look at pictures of FVs cornering. Have you ever seen a FV with anything less than maybe 2 degrees positive?

    The harder you corner a FV the more you bend the lower training arm.

  24. #24
    Member super66's Avatar
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    Guys

    This makes very interesting reading,lawyer bob any chance you could put up some pics of your D 13s double rear zero roll as this may be of use to me as I alked to some of the guys at the weekend and they say that we must two dampers and two springs and not a single unit as for the pics put here the car with the threee dampers in board is actually the GAC car a very good car in the uk but the guys told me that some one enquired about bringing one of these cars in ans was told that type of set up is noy allowed.
    Steve I think the cars you talk about were rebadged the" Predator" but I could be corrected and was driven by andreas serrano to take a champonship.

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    Do you have a link to your local rule set that we could look at? Lots of folks here with a ton of practice in reading between the lines might be able to see if a zero roll would make it or not.

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    Quote Originally Posted by super66 View Post
    Guys

    This makes very interesting reading,lawyer bob any chance you could put up some pics of your D 13s double rear zero roll as this may be of use to me as I alked to some of the guys at the weekend and they say that we must two dampers and two springs and not a single unit as for the pics put here the car with the threee dampers in board is actually the GAC car a very good car in the uk but the guys told me that some one enquired about bringing one of these cars in ans was told that type of set up is noy allowed.
    Steve I think the cars you talk about were rebadged the" Predator" but I could be corrected and was driven by andreas serrano to take a champonship.
    I knew Andre when he raced in the US. The cars he used in the UK were not mine.

    The setup I built could accomodate 2 shocks. Put a spacer between the bell crannks and mount a shock on either side. You would have to valve the shocks with 1/2 the damping force and use springs 1/2 the rate I used. Fox used to make small diameter shocks. You might find some cycle shocks that in pairs would work. It does not take a high dollar shock to work on the rear of a FV.


    I used such low spring rates that I had to go to 2.5 diameter springs. The US rules did not require 2 identical shocks, just 2 shocks and springs.

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    Andres Serrano won the 1995 UK F/Vee championship in a Predator.

    The Citations were rebadged as Spyders in UK, with rack and pinion steering and different noses. Jez Clark won several championships in an orange Spyder.

    Guy

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    Global Moderator Bill Bonow's Avatar
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    Default UK Spyder

    Here is Jez in the UK Spyder. I wouldn't really call them rebadged. Steve sold one into the UK and after heavy mods, they produced the Spyder
    Last edited by Bill Bonow; 05.18.14 at 6:39 PM.
    Bill Bonow
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  29. #29
    Global Moderator Bill Bonow's Avatar
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    Default Formula Vee Ireland

    FWIW, FV in Ireland is the closest relative FST has on the globe. Their rules are extremely close to the US Formula First rules.

    Check these guys out: www.formulavee.ie

    Cool cars, great racing
    Bill Bonow
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    Bill,

    I wasn't sure about the word 'rebadged' when I typed it, but I couldn't think of anything better. at the time.

    Now I see the picture, I remember they had to add a rear facing brace to the roll hoop and obviouly it has a ball-joint beam. There were probably about 5 or 6 Spyders produced, but this car was by far the most successful.

    Ironically, the car in the background is a UK-spec Irish Vee, a Leastone with a Z-bar rear suspension. This car too was a Multi-Championship winner in Britain, in the hands of Ray Moore.

    Guy.

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    Steve

    IF you have used the Mitchell software to model a FV zero roll rear suspension, how did you treat the single rear spring with it's floating ends?

    A) Is there a difference in wheel rate in a one wheel bump vs a two wheel bump?

    B) Is there a difference in shock rate in a one wheel bump vs two wheel bump?

    Brian

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    Quote Originally Posted by Hardingfv32 View Post
    Steve

    IF you have used the Mitchell software to model a FV zero roll rear suspension, how did you treat the single rear spring with it's floating ends?

    A) Is there a difference in wheel rate in a one wheel bump vs a two wheel bump?

    B) Is there a difference in shock rate in a one wheel bump vs two wheel bump?

    Brian
    1. I assumed the spring was fixed at the center of the chassis.

    2. In bump, the spring rate does not change but the displacement of the spring is double. In roll the spring rate is not an issue because the spring does not compress in roll. I have not put sensors on a FV but my guess is that in pure roll, the spring does not compress. In fact in pure roll, the spring unloads to the limit imposed by the droop limiter. Given that most setups use a lot of rebound damping, and the car might see some spring compression in a corner because of bump action on the track. Any difference in the load between the rear wheels when one tire encounters a bump will simply cause the rear suspension to roll vs. bump one wheel.

    3. When we get our new car to the track, I hope to explore the effects of different motion ratios. This has been a major area of development in other formula cars in recent years.

    I find it amazing that FV handle as well as they do.

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    Quote Originally Posted by S Lathrop View Post
    I find it amazing that FV handle as well as they do.
    They don't, we're just incredible drivers!

  34. #34
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    Guys

    The reason I asked the question about your zero roll was because we do indeed use a z bar on the rear of our cars here in Ireland and I am persuming that the z bar and the zero roll set up try to do the same job in other words to stop the rear wheels tucking in while corning,I noticed this year while travelling behind another car how much the z bar flexs (that is the length of bar from one side of the rear to the other) under load and thought to myself that each time you corner you are not going to get the same results due to this flexing that is why I thought of your type of seup but with two dampers instead of one as it would give repeatable results (that is it looks to be more solid) please correct me if I am wrong.
    A .few of the guys have mentioned on here that there has been zero roll set ups with two dampers but no one seems to have any pics to show this as if I could see these set ups I may be able to try this set up myself.

    Steve please except my apology I thought andres was running one of your cars.

    Bill I checked out some of the videos you have put and I really like the hard but fair racing that takes place in the USA what are you guys revving to.

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    Ed Zink did his first zero roll system with 2 shocks. He mounted a bell crank in the normal shock mount on the chassis and attached the shock to one leg on the bell crank. The other leg of the bell crank was connected to the same leg of the bell crank on the other side of the car. The link between the 2 bell cranks was adjustable. Each shock was preloaded sufficiently so that the car was supported at ride height. This is called zero droop and is common at the front of a lot of formula cars.

    The adjuster between the bell cranks was used to set rear camber.

    The down side of this setup is that the springs were 100 #/in and coil bind and collapsing was an issue. You will need to use 2.5 ID springs.

    This design should satisfy the Irish rules. I do not have a picture of Zink's design. I never saw it run, either.

    I think that some type of zero roll system would be a big improvement.

  36. #36
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    Steve
    your description paints a good mental picture, I may try a mock of this,i have just got of the phone to one of my friends and he remembered in a US VW mag he has somewhere pictures of a older type vee and he thinks it could be the zink machine,heres hoping.

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    Quote Originally Posted by super66 View Post
    Steve
    your description paints a good mental picture, I may try a mock of this,i have just got of the phone to one of my friends and he remembered in a US VW mag he has somewhere pictures of a older type vee and he thinks it could be the zink machine,heres hoping.
    Glad that I could help. Good Luck.

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    Quote Originally Posted by super66 View Post
    I checked out some of the videos you have put and I really like the hard but fair racing that takes place in the USA what are you guys revving to.
    Thanks much for the compliment. We're running a single 34 mm carby with a 32 mm balance plate underneath, so we don't see much beyond 6200 rpm on a good day.

    Steve,

    I was told the story that Ed Zink and Harvey Tempelton were at a race (in '67?) and in conversation, Ed told Harvey his idea for zero roll. Harvey built it on the Shadowfax. Can you confirm or add anything to this lore.
    Bill Bonow
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    Relevant to the previous question?

    http://www.conceptcarz.com/vehicle/z...Shadowfax.aspx

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