Z bar?

[sign.designer1]

Anyone have an old Z bar sway bar for sale? I need one for a vintage Vee restoration.
Thanks
David

[provamo]

was the Z-bar a droop limiter?

[pacratt]

was the Z-bar a droop limiter?

A z-bar acts as both a torsion/sway bar and a droop limiter.

David, what make/model vee are you working on ?

Glenn

[provamo]

what is the difference between a say bar and an anti-roll bar?

[sign.designer1]

The Z-bar is the sway bar that was used to manage rear chassis roll on earlier formula Vee's. I am working on what's supposed to be an Autodynamics MKIII, but I think it may be something else. An Autodynamics yes, but MKIII, probably not. I got a logbook with the car, but the chassis looks different than what's shown in the logbook. There was a one-off chassis built by AD in 1971, and I'm wondering if this is it. All my research has turned up nothing so far. I'll add some pics as soon as I get them sent to my computer. Thanks,
David

[S Lathrop]

The Zink FV's made their Z bars out of 5/8 diameter 304 stainless. You can bent that material cold with some very simple pressing tools.

I had a Mk3 AD but I don't remember what size the Z bar was or any details of how it was built. I do know that the Zink worked a lot better so I would use that car as my guide.

[BLS]

The later Zink's had a Z bar in a tube with bushings at each end and arms welded to the bar.

Would be pretty simple to fab something similar.

[BLS]

"was the Z-bar a droop limiter? "

Not really a droop limiter in the normal sense. It worked in the opposite direction of the normal sway bar/anti roll bar. When one side lifted, the opposite side would go down with a Z bar. This would tend to keep the relationship of the two tires the same, but allowed for some bump/droop at each side independently, acting as another spring in that sense. It acted as a type of "camber compensator" in that sense. When the car was lifted at the rear, the Z bar, when properly set, did not allow positive camber to develop, so in that sense it was droop limited.

From my memory, it was very difficult to get a Zink to oversteer when the Z bar was set properly, unless it was a real bad oversteer. It was a job to get the understeer to a minimum...

[S Lathrop]

A Z-bar is a spring that increased the spring rate in bump and rebound but had no effect in roll. It was setup to preload the road springs in bump so it had the effect of reducing the effective spring rate in bump until the preload was overcome when the spring rate in bump became the sum of the road springs and the z-bar.

The zero roll setups that followed were simply an extension of the z-bar principal but over a wider range of movement.

The big problem we had with the Zink setup was getting soft enough springs that could be preloaded to the degree they had to be so they could support the rear of the car.

[S Lathrop]

The later Zink's had a Z bar in a tube with bushings at each end and arms welded to the bar.

Would be pretty simple to fab something similar.

This Z-bar design was done to get a stiffer Z-bar.

[killerken53]

This was the z bar on the homebuilt car I had. Just a different view of a similar idea.

[socaljeff3798]

I have a brand new Lynx Z bar that I never used it has all the mounts and links.

These Z bars are heat treated. And designed for FV's

I am asking $300.00

Jeff
PM me

[BLS]

"This Z-bar design was done to get a stiffer Z-bar. "

It was an improvement over the old one, IMO. My first car had the older design and required much more "preload" to keep full droop from going to positive camber. This one did not require as much. At least that is how I remember it. As I recall it, I was able to get the inherent understeer almost eliminated, but not quite

[Ray Dona]

I have one in SS that will sell for $ 75. It is used - looks perfect... If you have some dimensional requirements, let me know.. email raydona@rexxonengineering.US or 978 838 2240

[Ed Womer]

Like Steve mentioned Z bars are pretty simple to make and can be bent even with simple tools if a bender is not available. I have made them for guys with older cars that they basically started to sag and I prefer to use cold rolled steel and bend the ends with the pipe dies on my Hossfield bender. The hardest part is getting them bent so when you lay it on a flat surface it is in the same plane along its length. Of course you have to then pre load the bar by pushing down on the chassis before you attach the links to the axles and how much depends on what result you want. This is also how you get the bar to keep the axles from going positive which is not good.

I just finished making some 11/16" sway bars for the front end since a friend ask me for some and I have a few left over for sale at $100 each. I can make them in pretty much any size from 3/4" down and I turn down the end of the bar to insert it into the square end so I can weld it with a Rosetta weld as well as the end where it butts up against the square. I also include the square ends tapped for 5/16" 24 threads with a short piece of threaded rod and washer and nylon lock nut for adjusting the play.

Ed

[Mark_Silverberg]

The Z bar has two intended purposes and one unintentional consequence.

The two intended purposes are
1) Reduce / eliminate rear roll stiffness - which it does for at least a good portion of the roll angle the vehicle experiences
2) Greatly reduce the spring rate in rebound to avoid the rear camber from becoming positive. This could be viewed as a droop limiter - but it is not a hard stop like many droop limited suspension.

The unintentional consequence is that the rear spring rates become very high when the both rear wheels are in compression. as the spring rate of the coil overs and the z bar add together. To counter act this the z bar is put in preload so that is actually is releasing before it starts to add resistance force in compression.


Interestingly the McLaren MP4-12C also had a Z bar - but for reasons opposite of a FV. It this case a very non - linear rear compression rate was desired because of the aerodynamic impact of the diffuser and wing.

[sign.designer1]

Thanks for the input, gentlemen. I appreciate the feedback and info. Also, Ray. I just sent you an email.
Thanks again

[problemchild]

The Z bar has two intended purposes and one unintentional consequence.

The two intended purposes are
1) Reduce / eliminate rear roll stiffness - which it does for at least a good portion of the roll angle the vehicle experiences
2) Greatly reduce the spring rate in rebound to avoid the rear camber from becoming positive. This could be viewed as a droop limiter - but it is not a hard stop like many droop limited suspension.

The unintentional consequence is that the rear spring rates become very high when the both rear wheels are in compression. as the spring rate of the coil overs and the z bar add together. To counter act this the z bar is put in preload so that is actually is releasing before it starts to add resistance force in compression.

Interesting overview, which would conflict with the overview I would provide.
If nothing else, I see your unintentional consequence as an additional benefit.

The negative, as I see it, is you need twice as many shocks and springs ..... increasing the weight and cost. Both weight and cost are increased again, if you go inboard, due to structure and linkage. If you leave them outboard, you have aero considerations, and increased risk to expensive shocks during misadventure.

The indirect negative, is that because a 4 shock car can be so sensitive, more setup tuning (and testing) is required. I ran 4-shock cars with inboard or outboard Z-bars for several years at the National/Runoff level. With droop limiters, you could generate a very stable platform, and be spectacularly fast in some corners. I abandoned the program because I was so underfunded that I could not develop it properly and, most significantly, the extra weight.

[Mark_Silverberg]

Interesting overview, which would conflict with the overview I would provide.
If nothing else, I see your unintentional consequence as an additional benefit.

The negative, as I see it, is you need twice as many shocks and springs ..... increasing the weight and cost. Both weight and cost are increased again, if you go inboard, due to structure and linkage. If you leave them outboard, you have aero considerations, and increased risk to expensive shocks during misadventure.

The indirect negative, is that because a 4 shock car can be so sensitive, more setup tuning (and testing) is required. I ran 4-shock cars with inboard or outboard Z-bars for several years at the National/Runoff level. With droop limiters, you could generate a very stable platform, and be spectacularly fast in some corners. I abandoned the program because I was so underfunded that I could not develop it properly and, most significantly, the extra weight.

Agree - I was just trying to speak to what the Z-bar did - obviously when the whole system is taken into consideration then there are other disadvantages to a dual shock / z bar setup from a weight, cost, and complexity standpoint.

It could be argued that the additional spring rate provided by the Z bar when both rear wheels are in compression would allow the spring rates on each of the shocks to be less and some may see that as an advantage - I just never found it to be