Leading arm attachment

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Re: Leading arm attachment

Postby hardingfv32 » October 16th, 2015, 12:34 pm

You are correct. My statement about the vertical force is incorrect.

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Re: Leading arm attachment

Postby Rickydel » October 20th, 2015, 12:09 pm

The Ringwraith did and does have ZRR rear suspension.
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Re: Leading arm attachment

Postby DFC17 » October 29th, 2015, 11:05 am

Just a little note on rear Motion Ratios.

Over the last 30+ years I have tried high and low motion ratios with the zero roll rear suspension. My conclusion is it doesn't matter. In fact my current rear suspension system (Modified BRD) has the lowest motion ratio of any system that I have ever made, or used, and it performs the best.

The fastest FV in the nation has the worst rear motion ratio of any Vee, or frankly any race car, I have ever seen.

The zero roll design is very unique and can not be engineered like a conventional suspension system.
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Re: Leading arm attachment

Postby FV80 » October 29th, 2015, 11:35 am

I agree with you Scott. Although I haven't actually TRIED nearly as many setups as you, my car has bascially ZERO motion "ratio" and it seems to work pretty well. I've seen quite a number of cars with widely varying ratios.. some push, some pull, but basically they ALL *CAN* handle pretty well. It seems to just come down to proper shock valving and that adjustable NUT behind the steering wheel.
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Re: Leading arm attachment

Postby hardingfv32 » October 29th, 2015, 1:57 pm

DFC17 wrote:The fastest FV in the nation has the worst rear motion ratio of any Vee, or frankly any race car, I have ever seen.

The zero roll design is very unique and can not be engineered like a conventional suspension system.


The same engineering that is used for a 'conventional suspension system' is used for a zero roll... or mono shock system.

Are you certain Varicins' mono shock system has a bad motion ratio? You have accurate knowledge of his shuttles dimensions?

Motion ratios are just one part of the suspension design puzzle. Not holding any more significance than any other part. Motion ratio is not an end target goal. Any valid research regarding changes in motion ratios would require appropriate spring and shock modifications made during a same day back to back test. Is that the type of testing you did?

Changing motion ratio without spring and shock mods is just basically a gross setup change. It could be better or worse than what you had before.

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Re: Leading arm attachment

Postby hardingfv32 » October 29th, 2015, 1:59 pm

FV80 wrote: It seems to just come down to proper shock valving and that adjustable NUT behind the steering wheel.


Spring/wheel rate.... and shock valving.

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Re: Leading arm attachment

Postby FV80 » October 29th, 2015, 4:24 pm

hardingfv32 wrote:
FV80 wrote: It seems to just come down to proper shock valving and that adjustable NUT behind the steering wheel.


Spring/wheel rate.... and shock valving.

Brian

Yep ... I MEANT to say that - spring/shock valving. The wheel rate is FIXED (pretty much). Can't change the wheel rate itself - just it's relationship to the spring.
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Re: Leading arm attachment

Postby DFC17 » October 29th, 2015, 4:52 pm

hardingfv32 wrote:
The same engineering that is used for a 'conventional suspension system' is used for a zero roll... or mono shock system.


I don't necessarily consider mono shock and zero roll to be the same. Even though they both use one shock they are different.

hardingfv32 wrote:Are you certain Varicins' mono shock system has a bad motion ratio? You have accurate knowledge of his shuttles dimensions?


I should have used the term "low" not "worst" my mistake. Yes, I would say that it is a low ratio. I might be wrong because I have never measured it, its just an educated guess based on my observations of the angles and the spring size.

hardingfv32 wrote:Motion ratios are just one part of the suspension design puzzle. Not holding any more significance than any other part. Motion ratio is not an end target goal.


Completely agree, especially when it comes to zero roll, that was the point of my original post.
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Re: Leading arm attachment

Postby DFC17 » October 29th, 2015, 5:01 pm

FV80 wrote:Yep ... I MEANT to say that - spring/shock valving. The wheel rate is FIXED (pretty much). Can't change the wheel rate itself - just it's relationship to the spring.


Actually the wheel rate is not fixed. it is a calculation of the spring rate and the motion ratio and will change depending on both factors.
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Re: Leading arm attachment

Postby hardingfv32 » October 30th, 2015, 2:02 pm

FV80 wrote:... my car has bascially ZERO motion "ratio" and it seems to work pretty well.


I have thought on this and I am interested in how you physically accomplish your motion ratio... if it is not a big secret.

I assume ZERO means 1:1 ratio. I have found that getting to 1:1 is a very challenging packaging problem. About the only way I can think of is either a very high shock location or rockers that hang downward and have a pivot point in a very high location above the transmission on a special sub-frame. Either would make for a interesting exhaust system layout.

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Re: Leading arm attachment

Postby FV80 » October 30th, 2015, 6:56 pm

It depends on how you define "motion ratio"..
In my car, there is a single rod connecting the ends of the shock to the ends of the axles (actually, a triangular structure that attaches to the axle near the trans and another point at the end of the casting closest to the wheel). There are no other rocker arms and there are no bell cranks. So.. as the wheels move up, the shock moves IN and UP. Yes... it has been quite a challenge to get a decent exhaust system on it, but we have managed to do pretty well with this setup for .. oh... 30 years or so.
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Re: Leading arm attachment

Postby hardingfv32 » October 30th, 2015, 11:01 pm

Your system would be similar to the Agitator? If so then you have a motion ratio on the order of 2:1... 2" travel at the wheel equals 1" at the coil over shock.

Motion ratio being the wheel travel movement vs the coil over shock travel.

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Re: Leading arm attachment

Postby jpetillo » October 30th, 2015, 11:40 pm

I like this discussion. Much of the reason to find the right motion ratio dependents on what your shock tolerates. You want the shock to move enough that its function is not dominated by stiction for small wheel movements where you want the shock to work for you, but on the other extreme not so much movement that you run out of travel. Then the valving needs to work for the piston speeds expected from that motion ratio. You can change motion rations, but where your shock transitions between low speed and high speed damping changes. I think that matters, and we should be concerned with that.

There's nothing magical about very large motion ratio suspensions (much lower shock movement - using Brian's definition of motion ratio) - it may just require a better engineered shock that will not have a stiction problem for small movements.

Although there is a big difference to me of how a single shock system compares in action to a double shock system, there is no reason I see where the motion ratio is any less important in a single shock design. Does anyone feel otherwise? John
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Re: Leading arm attachment

Postby jphoenix » November 1st, 2015, 12:19 am

Why is zero roll only found on an FV? Is it not a suitable design for other class open wheel cars?
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Re: Leading arm attachment

Postby jpetillo » November 1st, 2015, 12:39 am

Zero roll resistance in the rear puts the anti-roll duties to the front tires, which helps balance the front to rear grip. But, with the swing axle rear end and the standard single shock design, it helps control the rear tire camber better during cornering.
Last edited by jpetillo on November 1st, 2015, 3:38 pm, edited 1 time in total.
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