Steve Lathrop wrote....
The front sway bar attached to an a-arm that inturn attached to the top and bottom of the link pin carrier.
Steve
I have thought on this for a few days and can not figure out how to attach a arm to link pin carrier. How can you attach anything without modifying the stock parts?
Brian
Super66
1) A two shock zero roll setup would be over 30 years old. Not that many photos that old in the digital realm.
2) You need to ask yourself why the zero roll setup is not common where you race.
3) The flexing Z bar would not be a consistency issue. It is acting like a spring should. It could also be supported in the center.
4) "I am presuming 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 am not sure that statement is correct. The primary focus is to reduce roll resistance.
Do you appreciate that Z bar is the only spring you need in the rear. The coil over spring could be removed if the Z bar is made stiff enough.
You would then have a zero roll setup.
Here in the US, the rules specify that the car cannot touch the ground with the Z bar detached, thus preventing a zero roll Z bar setup.
All of this is before my FV time, so it could be subject to error.
Brian
I can not confirm that. I did see the parts on the bench in Charlotte. Zink stayed with the Z-bar setup through the first year of the Z12 FV in 1976-77. He sent me a drawing for the bell crank system after we had qualified for the run offs with a D13 rear grafted to the Z12. We built the new design and went to the run offs with any testing. Hogdal finished second. Over the years I produced well over a 100 zero roll kits based on that design.Originally Posted by Bill Bonow
You press a boss into the top and bottom of the link pin carrier. The boss is threaded and you bolt a rod end to the boss.
Steve,
Any photos available of the external sway bar?
Thanks!
Mark
Sorry, but no.
The bar did go around the front of the beam. The a-arms from the link pin holders attach to the ARB. I used a rod end mounted vertical to adjust the preload out of the ARB. The ARB was below the steering links. In the end there is a lot of stuff inside the wheels.
Back in the 80's I ran a stock VW external roll bar mounted with the factory rubber mounts and brackets. It was on a converted Lynx B with a factory 0 roll subframe. Worked really well and carried the car to a 3rd place at the Runoffs.
The above post is for reference only and your results may vary. This post is not intended to reflect the views and opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR. thanks, Brian McCarthy, BOD area 9.
Steve
Very sharp idea!
With a mounting system to the center vertical plane of carrier, could I now use a control arm from the carrier mounting system to a location in between the two beams? Would this control arm/suspension leg not then move with the carrier without binding. Not sure how to state it, but move in the same arc?
It is a special day when I learn something new. Thanks
Brian
You need separate links for each of the arms, with their pivot points at the centerline of the beam tube - eg - you want the lower link (for the lower trailing arm) pivoting at the centerline of the lower tube, and if using a link for the upper arm (off of the top of the upright) it has to pivot at the centerline of the upper tube. Any other arrangement will cause binding since they won't be traveling on complementary arcs.
I worked all this out a few years back, but never produced it - too much work for the potential monetary payback.
What you say is true if you locate on the control arms, but that is beauty of Steve's method of attaching to the carrier. It provides an operating plane that is between the tubes so you can reach the correct mounting position parallel/in line with the axis of the beam tubes.
Is this not correct?
Brian
No.
The Lilly link a-arm sticks out perpendicular to the car centerline, with the inboard end following the same arc as the upright. It is allowed to "float" so to speak at its inboard end via the drop link to the swaybar. In the case of a link forming the second leg of an a-arm bracing an individual trailing link, the inboard pivot has to be on the same line that the trailing link pivots on.
With an a-arm attached to the top and bottom of the upright at the outboard end and between the beam tubes at the inboard end, you have to remember that it is prevented from swinging in an arc about the inner pivot point because its mountings points at the upright do not move in the same type of arc as the individual trailing arms - each outer pickup swings up and forward the same amount, forcing the inboard pickup of the a-arm to swing up and forward the exact same amount.
The construction complexity for bracing the individual links comes from having to construct a pivot around the beam tube - it can be done, naturally, but it isn't cheap and simple.
I think I see the miscommunication.
I am proposing a triangle shaped subassembly: two ends of a triangle structure mounting to the two ends of the carrier/upright and the third corner of the triangle is the mounting point for the control arm. This sub assembly has no freedom of motion. So now I have a central location for the control arm.
Does this sound better?
Brian
I think some sketches would clear things up a bit
(and not just so I understand what's going on here, either..!)
I could build an example faster than drawing it on computer. Is not nor will it ever be in my skill set.
If you want to try I will comment on your effort.
Brian
OK, I think I get what you are describing now - an arm (or link) attached to a bracket that is in turn attached to the 2 ends of the upright.
In this case, the arm (link) will have to be exactly the same length as the trailing arms (as measured parallel to the car centerline), and mounted parallel (looking from the side) to the trailing links. Only then will it travel on the same arc and not cause binding.
However, to get any decent benefit from it (bracing the lower trailing link from flexing inward), its mounting point at the upright would have to be close to the lower arm pivot, which then puts its forward pivot somewhere inside the lower tube.
Raise the arm up at the upright (closer to the half-way point between the trailing links), and the effectiveness decreases dramatically.
The next problem is that by using this secondary bracket, your pickup for the link is now alongside the upright, causing a torque moment at the bracket's attachment to the upright. If you expect a pressed-in plug to handle that load without eventually loosening, think again.
If what you are describing is an a-arm pointing inwards (lateral), with a link from there going forward to a pivot point between the tubes, to get any benefit, the link going forward will have to be an integral part of the lateral arm to impart any resistance to the bending forces at the trailing arms ( and it would have to be pretty stout since you are relying on its bending strength instead of feeding the loads directly along its length)- if it is attached via a rod end, it will do nothing for you at all in that regard.
You are correct about the actual fab issues, but at least I understand what is possible. I do not feel the system is require, so I can live with our current understanding. I think there are more components involved with this overall flex issue than just the control arms.
I do not believe much extra camber is required to solve most balance issues. So, solving the flex issue is not really required to get a improvement in front end performance.
It was a good learning experience.
Brian
Arm flex is only one of the issues in front end grip - the biggest is the friction that it induces in the bearings inside the tubes, and no matter what sort of "tricks' are employed there in modifying the bearings, the lateral loading of the trailing links makes them bend in between the bearings (as well as load the bejezuz out of them), causing misalignment and extra friction. Bracing the trailing arms (or, in the case of the Lilly Link, applying a counter-torque at their outer ends) is the best way of addressing both issues.
Very good point. I learned two things today. Thanks for hanging in with the conversation.
Brian
If I'm bored with nothing to do at some point in the future, I'll draw something up (highly simplified) so that those who are still confused can see what we are talking about.
Unfortunately, with my current work load, that may be a while!
Vee's are a cool problem, engineering-wise. Everything about them is totally wrong for good performance, so it is amazing that they corner as well as they do. If a couple of remaining issues are resolved, even the old masters of the class might be surprised at the jump in performance.
You mean me? Yup, that would be great
Thanks for the discussion everyone, I love these threads, especially when I struggle to understand them. Makes for better learning!
Fascinating topic .... but before doing a drawing to explain the Lily front end, please write a rule to prevent people from doing it. The very last thing that FV needs right now is a technical revolution.
Greg Rice, RICERACEPREP.com
F1600 Arrive-N-Drive for FRP and SCCA, FC SCCA also. Including Runoffs
2020 & 2022 F1600 Champion, 2020 SCCA FF Champion, 2021 SCCA FC Champion,
2016 F2000 Champion, Follow RiceRacePrep on Instagram.
Why bother, name one person on the East Coast that would go to the trouble to make such a device? Can't be but a handful that even have the skill set to accomplish it. And of that group how many are competitive enough to prove its value?
Brian
One could argue that Zero-Roll rear ends were a technical revolution.
Hell, anything compared to the stock components could be considered a technical revolution!
Greg, Anyone can write a rule. Feel free to submit whatever you feel is needed. We as members make the rules, not SCCA.
Guys
There has been a great response to this post and a lot of techanical know how displayed but I am still no wiser as to what Zero Roll is actually. What is zero roll what does it do to your car going into a corner, in a corner or what does it actually prevent and what is happening to your car when using zero roll.
I have tried reading up on this but what I am actually looking for is a simple explanation of it (laymans terms) as I have started to look into the chassis set up and performance and asking a lot of the guys here they either dont know or are not willing to tell you.
Well, as the least experienced guy on this thread, I can tell you what my understanding of it is, how it works and what it's supposed to do. It might not be entirely correct, but it will be as layman as it gets!
Basically, there are two bell cranks.. Or uprights or whatever people wanna call it. In the simplest examples, they are two vertical parts that attach to the frame on either side of the gearbox. They can freely rotate parallel to the axle.. Between these two uprights, we have a shock/spring combo. If you think of just these 3 parts, you can move the whole thing side to side, the uprights will hinge on the frame and the shock will remain parallel to the ground, moving side to side. Right?
Then you connect these uprights to the axle tubes (or trailing arms, usually.. same effect in our simplified version of things..). What happens now is, if both wheels move up or down, the shock/spring gets compressed or extended. This is what happens when you go over a bump, or under braking/acceleration. In roll, when you're cornering, one wheel will be going down and one wheel will be going up - so the whole assembly rotates freely, there is no spring or shock stopping or controlling the movement. So the zero roll really means zero roll resistance. The rear suspension does not control roll in any way! So all of the roll resistance is coming from the front suspension. Remember, this is a simplified version, there might be more to this, but.. That's the idea! If the rear suspension doesn't have to deal with roll resistance, it has more grip to deal with cornering. Also, the rear inside wheel is supposedly always loaded with at least the unsprung weight of that corner, which means you're not likely to get wheel spin out of corners.
Does that help?
EDIT: One other thing.. With a zero roll car, two funny things can happen - if you were strong enough to pick up the front end with your arms, you could rotate (roll) the whole car side to side and both rear wheels would stay on the ground, unaffected. It would feel like a wheelbarrow! On the other hand, if you jack up the rear of the car (lift it up by the frame..) You can move one wheel all the way up and down (and the other will move down and up) with one finger
Zero Roll is the term that describes various systems that support the rear end of a FV and have as their main characteristic no resistance to roll. If you jack a zero roll car up at the rear, you can roll the rear suspension in either direction and it will not return to a square or the same position as it was when it is on the ground. Yet the system will support the car. Also part of the system is a limit on the total travel of the rear suspension in bump and rebound.EDIT: One other thing.. With a zero roll car, two funny things can happen - if you were strong enough to pick up the front end with your arms, you could rotate (roll) the whole car side to side and both rear wheels would stay on the ground, unaffected. It would feel like a wheelbarrow! On the other hand, if you jack up the rear of the car (lift it up by the frame..) You can move one wheel all the way up and down (and the other will move down and up) with one finger
The goal of the system is to reduce the loading of the rear tire during cornering and limit the tire travel in order to achieve maximum grip for the rear tires. One unique characteristic of the FV rear suspension is that wheel travel and camber are related exactly. The zero roll system controls the rear camber and results in the softest vertical wheel rate possible. Zee Bar systems have much higher friction and single wheel spring rates than the zero roll system. Bottom line is a car has more potential grip with zero roll.
As you put larger tires on the rear of a FV, you possibly get less of a grip return than one gets with the relative small tires used in US FV racing. This is my speculation only.
Greg: FV has always been a development class. Years ago I came to believe that no matter how trick you made a car, for any one lap it is the guy who has the best engine, best tires, the best balanced setup will be the fastest when well driven. The most one can hope to achieve is a car that gives your driver an advantage that plays out over the distance of the race. It may be nothing more than your guy gets more passing opportunities than the opposition. The trick cars take time to make them work and you can always copy what he has done if he makes the tricks work.
super66
We digressed while waiting for photos or more questions from you.
The most simple explanation: There is no functional difference between the two types of rear FV suspensions, EXCEPT roll resistance. A Z bar system has some minimum level of rear roll resistance, says no lower than 20%. A zero roll system can have go as low as 0%. Less roll resistance at the rear means more grip, all other things being equal.
Questions?
Brian
Guys
Thanks for the responses I now understand what you mean by zero roll I should have maybe asked for the easy way first but thanks for sticking with me on this and I think it is worth looking at for our vees whether it will be allowed or not is something else.
Brian sorry I did not get to collect my car at the weekend as it was not ready and it was not worth a 200 mile round trip but when I do get the car I will post some pics, just one other thing Brian on your car I noticed a set of very neat air ducts directing down on to the top of your heads are they homemade or can they be purchased from someone ?
Steve the pics of the US vee the my friend has in the VW Mag. are actually of a 1972 Caldwell D-13 and was owned by a guy by the name of Rex Linde I dont know whether it has zero roll on the rear or not but if it was I think that it would work with in our rules do you know the car and its rear set up ?
Yes, that was my old car. Very familiar with the article/pics. That set up is the common to-the-D13's-of-the-era twin shock zero roll set up.
I purchased Rex Linde's D13 back around 2004. I've since sold it but know its new owner well. If you want any additional photos or measurements from that set up let me know.
If you want pictures of any other similar setups post a question on the VARA website in the FV section. Every VARA FV1 class car runs a dual shock zero roll set up. FV2 allows zero roll with single shock. FV does not allow zero roll unless on the shadowfax (period correct).
Here's a vid.
http://www.youtube.com/user/fezzic18.../1/F7XgjneAo8Y
Thanks Fezzic
That explains it very well.
Hey Anyone,
I've attached a drawing for a front suspension I was thinking of building. It will be for a trike with a single rear wheel. I was researching zero roll and found this thread. The bottom photograph in post nine seems a lot like what I was planning. I am curious what anyone might think of the idea?
Kevin
What would stop you from falling over? A zero roll provides no roll resistance. Seems like on a trike that would lead to the bike just falling over???
Stephen Saslow
That's what I thought. So it's not actually zero roll it's zero anti-roll? In that case I'll need an anti roll bar. But at least it separates the anti-roll from the suspension and puts it all on the bar. And it's a three wheel car so it can't fall over.
You should just do what the other trikes are doing. This whole trike subject is outside yours and almost everyone else's design skill set on this forum.
Zero roll on a FV is designed to deal with a set of chassis dynamic/handling requirements unique to the FV. A trike has a completely different set of requirements.
Brian
Last edited by Hardingfv32; 10.26.17 at 3:38 PM.
Well yes, its soooo complicated. Morgan has only been doing it for more than a hundred years. To be honest if I was happy doing what everyone else was doing it wouldn't be worth doing. I'd just ride my Ducati. If the nomenclature for the suspension were correct I wouldn't have bothered you in the first place.
Please excuse the FV/FST community for using the incorrect nomenclature to reference their "zero roll resistance" rear suspensions. Most of us would probably consider a trike with single rear wheel to all ready have "zero roll resistance" rear suspension and thinking that putting a "zero roll" configuration on the front suspension would be unmanageable and fall over. Clearly I will show my ignorance with my suggestion that you could then install some training wheels and call it a Quinticycle, which would fit in with your criteria of being different than what other people are doing. Or you should ride your Ducati.
Greg Rice, RICERACEPREP.com
F1600 Arrive-N-Drive for FRP and SCCA, FC SCCA also. Including Runoffs
2020 & 2022 F1600 Champion, 2020 SCCA FF Champion, 2021 SCCA FC Champion,
2016 F2000 Champion, Follow RiceRacePrep on Instagram.
Just thinking about cornering, my guess is that the rear tire needs to be cambered into the corner to develop good cornering power.
As you corner, the car will roll to the outside of the corner and the rear wheel will camber outward. This may result in the rear wheel actually steering to the out side of the corner. It will also reduce the cornering potential of the tire. Seems to me that you need to design a suspension system that causes the rear tire to camber into a corner as you turn the trike.
I have actually seen a sway bar setup on a FV that used the force of the sway bar to camber the out side wheel into a corner. Maybe you can figure out how to do that at the rear. And I can see a zero roll resistance front end that would make that system work. But the geometry of the front suspension won't be any thing even close to what you have drawn.
Yes Morgan has build trikes a very long time ago. But I don't remember that they used a zero roll resistance front suspension system.
Thanks, your comments are helpful. When I asked about zero roll I was thinking of anti squat which if I understand it correctly keeps the tail from drooping under acceleration. And it is done with the suspension geometry I believe.
As for cambering the rear wheel I agree it would help in cornering. I think trying to cause camber change on the swing arm/drive wheel would be impractical. One possibility is to lean the whole monocoque from the front. A passive system would be to use Ackerman and a lot of caster to cause the inside wheel to drop the inside of the trike. An active system might work by giving the lower control arms a single center pivot. The steering arms would then be fixed to the chassis. And the steering rack would be connected to the upper joint of the spindle. It might be necessary to use power steering I don't know. It might be possible that the centrifugal force would right the chassis as you exit a corner. It needs to be drawn and modeled.
I was also planning to use those huge rear tires they put on Harley's. The tire has a round profile so it would not provide roll resistance. I would use the biggest one I could find for the rear. Mount it on a 'wide five' race wheel which could be bolted to a Honda Comstar hub pretty easily using a flat aluminum adapter plate. You can use some smaller rear tires on the front you just flip them around so the tread pattern works for braking rather than acceleration. They come in 15's so car wheels would work on the front.
There are currently 3 users browsing this thread. (0 members and 3 guests)
Posting Permissions
Reply With Quote
