Solo vee rear suspension.

[killerken53]

So I keep getting the idea in my head to abandon my current late 60s vintage solo vee chassis and build a new chassis from scratch. Currently the car runs 2 rear shocks and a z bar. I know this is ancient technology in the racing vee world, with current cars utilizing zero roll resistance designs. The question is, does zero roll style suspension help with the low speed cornering we experience in autocross, or am I better off with a z bar and stiff springs.

My initial thought is to utilize stiff enough springs the car essentially becomes a large go cart or 500 style with minimal suspension travel. Maybe I am completely off base. As always the goal is to eliminate as much understeer as possible.

[Drake]

Couldn't tell you about the Vee, but with my Spitfire (and I assume any swing arm rear suspension), roll resistance must be minimized. Tried coil-overs once and the handling was terrible. Have you thought about making a push rod - mono shock mod.?

[S Lathrop]

Your push problem is not at the rear of the car.

The rear roll resistance is dominated by the very high roll center that is a function of the swing arm rear suspension. Among other features is the tendency of the rear end to jack up in a corner. The zero roll setups allow you to control the jacking tendency. All the zero roll systems have a droop limiting system. As the car corners, the rear rises and corners against the droop limiter. The wheel movement is a combination of some bump and a lot of small rolling movements. The advantage of the Zero roll setups is the much lower resistance to wheel movement and consequently better rear grip. I have found that adding a very small rear anti roll bar does add a nice tool to help balance the car.

I would suggest that you could make a major break through in performance with an external front anti roll bar that operates on the link pin carrier and not the trailing arms. I found that the car could use a stiffer front ARB than could be fitted inside the beam. The stiffer ARB would make the car more reactive to steering inputs and the external ARB would help reduce the positive camber gained by the flexing of the trailing links.

At a minimum you could try adding the external ARB that VW used on later model cars. This might do a lot to improve the US issue.

[HayesCages]

Go with the zero roll set-up, you'll love it.
Steve:
As far as using an external front anti-roll bar; since one of the spring packs is removed from the beam and a bar of some kind put in it's place, what would you use to hold the trailing arms in place if you used only an external bar? Or are you saying that you need an additional bar to the internal one?
We used a piece of 3/4" square the full length of the beam and had no issues with handling. (after boring the center hole...)

[killerken53]

Thank you all for the clear and detailed answers.

I did forget to mention I am running FF size tires, including wide rears in R25(B?) compound.

I am presently running an internal ARB of unknown stiffness that came with the car, and 1 spring pack. I will scrounge around and see if I can come up with a complete external ARB to add as an experiment.

The way the car is presently configured, a zero roll type suspension would be challenging. If I choose to go that way I plan to build a new chassis from scratch to address that and several other issues that I don't like about the present design. That may be a little while down the road.

I have never weighed the car, corner or otherwise. I will really try to get that information. I have always felt that the front end was "light", but that is only from seat of my pants feelings. Is there any benefit to playing with rear ride height or adding weight to the front end to improve mechanical grip?

[S Lathrop]

Go with the zero roll set-up, you'll love it.
Steve:
As far as using an external front anti-roll bar; since one of the spring packs is removed from the beam and a bar of some kind put in it's place, what would you use to hold the trailing arms in place if you used only an external bar? Or are you saying that you need an additional bar to the internal one?
We used a piece of 3/4" square the full length of the beam and had no issues with handling. (after boring the center hole...)

I just had a rod between the 2 trailing arms and nuts to set the clearance between the trailing arms and the same thrust bearings used for the sway bar. I had pieces of square stock with holes to center the rod in each trailing arm.

[S Lathrop]

Decades ago, I built zero roll conversion kits to change from a spring/Z-bar setup.. I had one customer say that it took him less than an hour to change his Lynx over to zero roll. I produced close to a hundred of those kits

The original design was something Ed Zink drew up and sent to me just before the run offs in 1970's something. We installed the setup on the Z12 for the first practice and finished second that year. We followed that up with 4 wins over the next 5 or 6 years.

[HayesCages]

I just had a rod between the 2 trailing arms and nuts to set the clearance between the trailing arms and the same thrust bearings used for the sway bar. I had pieces of square stock with holes to center the rod in each trailing arm.

So you had no front anti-roll bar of any kind? Or just the stock VW one?

[BLS]

The way the car is presently configured, a zero roll type suspension would be challenging.

FST cars use the swing axle with FF tires (R60 compound I think) with Zero Roll rear suspension, and do not have issues.

[HayesCages]

[QUOTE=killerken53;468019 ......eliminate as much understeer as possible.[/QUOTE]

We used to run 1/8" toe out for A/X, makes low turn-in much better.

Have you looked at your Akerman angle? We ran zero* (none) for road racing but suppose something close to stock would work better for low speed courses.

[S Lathrop]

So you had no front anti-roll bar of any kind? Or just the stock VW one?

No. I built an external ARB that operated on the link pin carrier and not the trailing arms. The bar was much stiffer than I could have made and mounted inside the beam.

I copied the ARB setup from a FV I saw in the late 1960's.

The ARB forces counter act the bending tendencies on the trailing arms.

The steering setup on my cars allows me to increase akerman to a bit more than 100%.

[HayesCages]

Gees, how big was it?

[S Lathrop]

Gees, how big was it?

7/8 x .080

[killerken53]

Again, the information is invaluable. I will give all of it a shot.

In the meanwhile, here is a picture of what I am working with.

[S Lathrop]

30 minutes with a hack saw and you would be ready to install zero roll setup. The biggest issue will be relocating that battery.

I mounted the zero roll system on the Zink Z12 with a bracket that used the hole in central rib of the transmission and the 2 bolts that mount the engine and the transmission. You cut the Z bar mounts off and move the battery and you have the same space I used for the Z12.

[BLS]

Here is a picture of Steve's Citation design:

[killerken53]

A picture is worth a thousand words. Thank you both.

Looks like I have a project to figure out how to build Mr. Lathrop's assembly.

[S Lathrop]

Here is an other picture of the same idea.

The droop limiter spring is missing.

[BLS]

Steve, first pic of the new car?

[S Lathrop]

Steve, first pic of the new car?

It has been on the track for testing. This has been a very slow project. The homologation papers were issued from Denver.

Some of the body work was hammered aluminum. The hammer that did the work also built an Indy car that my father was part owner.

[provamo]

Steve, first pic of the new car?

chassis looks stout....is there room for an engine?

[S Lathrop]

chassis looks stout....is there room for an engine?

Ithink I can put a type 4 in there if I had to. A FV engine has plenty room. A six cylinder won't fit though.

[provamo]

Ithink I can put a type 4 in there if I had to. A FV engine has plenty room. A six cylinder won't fit though.

can not wait to see your latest creation

btw thanks for all the technical advice you have posted here!

[Purple Frog]

The car in post #23 of this thread:
http://www.apexspeed.com/forums/showthread.php?t=68087

Had a Z bar like the one in the first post... but was also droop limited with a cable/pulley system. Crude, but effective.

At first glance I actually thought I might be looking at the old car, but looking closer the one that is the subject of this thread is much nicer than my old crate.

[BLS]

Some of the body work was hammered aluminum. The hammer that did the work also built an Indy car that my father was part owner.

Thanks, hope to see it soon...