Zero roll "bump" limit?

[tiagosantos]

Where are you seeing the graph for front ride height?

According to Scott, black is chassis roll in degrees (measured at the front beam), red is rear ride height. Since the scale is centered around zero, I'm going on a limb and saying that 0 is normal ride height (whatever that his for his car), above zero means the car is jacking, below zero means it's compressing the shock (lowering ride height..).

As far as #2 there, seeing the two scales for on and off the limiter, I see your point. But depending on how much static camber Scott was running and what he had his droop limiter set to, there might not be much of a ride height change between them.. I dunno. The graph does seem to move up very slightly when the roll is at max, but I agree that I was expecting it to move a bit more on a "normal" FV setup. You know, the typical 6 degs of negative camber, 1 or 2 of droop. I know I run my numbers a bit closer, but still..

[tiagosantos]

darn it, I said I wouldn't look at the graph more than 10 seconds, but I had to go and look at it again. Anyway, I think if Scott added some filtering to the curve, we'd see that his static ride height with the driver sitting in the car would probably be right around -0.15.. Look at the big flat area on the roll graph about 3/4 of the way into the lap. Looks like a nice long straight. The rear ride height graph starts (with a lot of noise, but imagine the average of that section) right around -0.17 and slowly goes up to -0.05 or so until it flattens up completely. I'd guess that Mr. Scott was braking hard into T14 and the car went right up against the limiter, stayed there for the first part of the corner.. Then there's a nice downward spike, most likely the usual trip into the rumble strip between 14 and 15.

[Mystique Racing]

I run -2 deg. total Droop and -4 Deg. total camber, so zero on the potentiometer would be -2 deg. total droop. I use my shock as the droop limiter.

There is no noise on my trace. What you see is what you get.

[hardingfv32-1]

Normal convention is for compression to be positive on the chart.

That said if, you reverse the signs and make -.10 your static ride height, then it could make sense. .10 of travel might be 2 deg of camber and gets you to zero which could be the droop limit. Those are some healthy compression spikes, maybe curb riding. The one at the hill must be the car landing after the crest and bottoming. That is a lot of compression for a car that is supposed to have a low ride height. Maybe that is by FV standards.

A lot of time spent a 6 deg rear camber if these are the correct interpretations.

Brian

[smsazzy]

When a vee turns in, it is generally on the rear droop limiter by mid corner. This is due to the natural jacking forces of the swing axle.

Whether your car has a droop rod, or just the shock length is limited, that is ultimately where it ends up.

1) So this is an exception to your statement? So you think you are compressing going into the turn (uphill and light braking entrance)? Why does the front shock not show any unusual compression?

2) "You are reading the graph backwards." View the scale, I do not think so. Regardless, we really should see two clear range limits for the red trace in you are spending anytime on the limiter. One range limit is when the car is on straights and the other is when it is turns. There only seems to be one in this graph.

Brian

1- The compression is at the apex of the turn. Where the road abruptly goes up. The same spot i normally see 2.4 lateragl G. That is not possible without some serious compression into the road. (after turn in, just about at my apex before you crest the hill)

2- As stated by others, you are indeed seeing it backwards.

The small oscillations while on the bump stop is normal road irregularities. You will always see this. Even if you set static camber to -3 and droop to -3, you would still see the slight up and down due to bumps and pavement changes. This is due to the fact that bump stops are not typically made of cement, but rather a compressible material. It gives a little to absorb these irregularities.

3- You know better than this, you're just messing with people. Every year we replay this conversation. We're still not on a billiard table smooth surface. And just to clarify, you do indeed run a droop limiter, it is just built into the valving of your shock. Now that we have covered that, we should be good.

[problemchild]

3- You know better than this, you're just messing with people. Every year we replay this conversation. We're still not on a billiard table smooth surface. And just to clarify, you do indeed run a droop limiter, it is just built into the valving of your shock. Now that we have covered that, we should be good.

For the purposes of this discussion ...... Atleast we got this out of the way early this year.

[jpetillo]

I believe that Brian had stated this pretty clearly in the past - that he runs stiff suspension and uses the limit of his shock at full extension as an ultimate droop limiter, but does not use an external droop limiter. It sounds like Scott does something similar. I didn't see that Brian was even bringing up this subject in this thread. John

[smsazzy]

It was simply a matter of time.

[hardingfv32-1]

1) The compression is at the apex of the turn. Where the road abruptly goes up. The same spot i normally see 2.4 lateragl G. That is not possible without some serious compression into the road. (after turn in, just about at my apex before you crest the hill)

So, you are tell me the car goes to about -8 degrees camber at this point and is happy? Where are what should be record amounts of roll at this point on the black graph?

2) I honestly did not realize the graph was not to normal convention.

3) We clearly outlined how my suspension functions without HITTING any form of limiter in past threads. You clearly don't have the skill set to appreciate what was discussed. As a Vortech owner why would you care? You wouldn't dare change anything.

Brian

[Mystique Racing]

So, you are tell me the car goes to about -8 degrees camber at this point and is happy? Where are what should be record amounts of roll at this point on the black graph

Not sure if .600 of shock travel is equal to -8 deg. of camber, I meant to create a math channel to calculate that but never got to it. I do know that .600 of shock travel is equal to one inch of chassis vertical movement.

The compression in the track that smsazzy refers to effects all four corners of the car so there will not be any additional roll shown on the graph.

BTW Brian, you should know that I never do anything to "normal Convention"

[Rolling Stone]

Yawn!!!!!!ZZZZZZZzzzzzzzzzzzzz

[smsazzy]

3) We clearly outlined how my suspension functions without HITTING any form of limiter in past threads. You clearly don't have the skill set to appreciate what was discussed. As a Vortech owner why would you care? You wouldn't dare change anything.

Brian

Here is your statement from the other thread:

I do not have a droop limiter. The shock is used to keep the camber from going to positive camber as a safety precaution. If you want, you can say the droop is set at 0 deg.

Seems pretty clear to me that you are indeed running a droop limiter.

[BLS]

I read through that thread when I first started reading here.

"The shock is used to keep the camber from going to positive camber as a safety precaution."

That statement only says the shock is an ultimate safety limit. As I recall, Brian has a very high spring rate, and his car runs out of spring before it gets to positive camber.

I think it is fascinating to see some variation, and discussion, over a suspension design 40+ years old.

[smsazzy]

"Runs out of spring" is irrelevant. It is not the spring (alone) forcing the car into jacking. It is also the leverage of the wheel on the swing axle. If the spring has such short travel that it cannot push the car up an inch, then I concede that it is a unique setup. Based on results, I can only assume it is not a good idea.

[jpetillo]

Yes, the spring and jacking forces together support the sprung weight at the rear of the car. I took BLS's comment of "running out of spring" to mean that the spring reduced vertical force by the amount of the jacking force before it hit any limit, at which point it will stop raising up. Since the jacking force is not enough to hold the car up on it's own, the spring should still have plenty to go. If the spring used reduces vertical force quickly enough that it doesn't allow it to jack past, say, 2 degrees negative total camber as another car would by using a droop limiter, can you explain why you think this is a bad idea? I hope I didn't change the scenario too much.

Perhaps we're straying from the original intent of this thread - it was not about our perceptions of Brian's suspension. Apparently I'm not helping matters with this post. I'm more interested in seeing where Scott's post is going to go - it's a good subject. John

[BLS]

"Runs out of spring" is irrelevant.

Well I admit to being being on the unknowlegable end but I don't think it is irrelevant. If there is no more "push" from the spring I don't believe the side force at the contact patch is enough to support the weight of the car which is required to go further into positive camber territory.

I am not passing judgement on the soundness of it. I'm not even positive it is what Brian said, just what I remember getting out of that thread. It does however seem to go along with the statement you cited regarding the "safety precaution".

[smsazzy]

can you explain why you think this is a bad idea?

Results. In order to have the spring that stiff, the back end is so hard that the car is undriveable. One lucky lap without a spin may be fast, but in 4 races, I have seen that car finish only once on the lead lap and that was in 6th place. All three other races it was lapped at least once by at least one Vee.

I hear all this talk about how brilliant this set up is, but it is yet to finish well in a race.

You can't expect to have that stiff of a setup and have a car handle the conditions of a 35-40 minute race. Unless maybe you put Raikonen in the car.

Think about it, in order to not have at least 2 inches of compression on the spring, you have to be running 400 pounds or so of spring. (depending on the motion ratio of the rockers of course, but bottom line is, it has to hold up about 550 pounds of car) that gives the rear almost no ability to absorb road irregularities and makes the tire essentially the only absorbing agent. I'm just not seeing that work.

[Mystique Racing]

I'm more interested in seeing where Scott's post is going to go - it's a good subject. John

My post was simply to try to give a real world example to help answer the question originally asked regarding the amount of rear suspension travel and the amount of rear suspension roll.

Nothing more, nothing less.

[tiagosantos]

You can't expect to have that stiff of a setup and have a car handle the conditions of a 35-40 minute race.

Yes, at your level, you don't need a setup like this yet.

[hardingfv32-1]

[quote="smsazzy"]
In order to have the spring that stiff, the back end is so hard that the car is undriveable. One lucky lap without a spin may be fast, but in 4 races, I have seen that car finish only once on the lead lap and that was in 6th place. All three other races it was lapped at least once by at least one Vee.

1) You are talking about a new car using the same stiff rear suspension design as the previous model. The new car has had its share of teething problems NOT associated with the rear suspension. I don't think we had any trouble with the competition in the period 3-5 years ago using the stiff rear suspension on the previous model car.

2) "Think about it, in order to not have at least 2 inches of compression on the spring, you have to be running 400 pounds or so of spring. (depending on the motion ratio of the rockers of course, but bottom line is, it has to hold up about 550 pounds of car) that gives the rear and makes the tire essentially the only absorbing agent. I'm just not seeing that work."

This statement if not clear to me. If you find it necessary to keep this as simple as saying a stiff suspension has 'almost no ability to absorb road irregularities', then I will counter with how do FF or even F500 get away with such stiff suspensions? You have no scientific bases for saying my rear FV suspension is too stiff. Your are only restating a FV myth.

Do you even understand how my stiff suspension works?

Brian

[smsazzy]

Do you even understand how my stiff suspension works?

Brian

It doesn't.

[hardingfv32-1]

It doesn't.

I interpret that answer as you tapping out. That you can not add anything intelligent to the discussion.

Brian

[Rolling Stone]

I don't know how my stiff suspension works...but my old Lady does,and it's nothing to do with 2" either Give it a rest boys call it a draw.

[jpetillo]

I'm more interested in seeing where Scott's post is going to go - it's a good subject. John

My post was simply to try to give a real world example to help answer the question originally asked regarding the amount of rear suspension travel and the amount of rear suspension roll.

Nothing more, nothing less.

I know, it's an excellent piece of data. I was interested in seeing the discussion that followed.

[smsazzy]

Don't worry, Brian and I aren't going to have a fist fight otr anything. We're friends. We just both enjoy a spirited debate, and I like pulling his chain. Heck, I'm even a customer of his.

However, Brian, with all due respect, you have no idea what my rear shock setup is. How could you? I can tell you this, there is not a vee in the country using what I'm using.

I do understand how your rear suspension works, I think.

Basically, the rear spring is so stiff, (or preloaded perhaps) that there is virtually no compression of the spring due to chassis weight. So when the jacking forces start to lift the rear of the car, once the spring has travelled to its "maximum unwinding" (can't think of the term, fully extended - it's been a long day) the spring no longer contributes to lifting the car.

If you assume the distance (for easy math) from the tire patch to the axle is 1 foot, and the side load on the tire is about 750 pounds (assuming the tire is gripping about 1.5G and the back of the car weighs 500 pounds - again - for easy math) the lift on the car should be about 750 pounds. Divide that by the length of the axle (reverse of leverage- call it 3 feet for easy math) and you have 250 pounds of lifting force. Since the back of the car in this example weighs 500 pounds, you stop lifting when the spring stops helping.

Does that summarize it?

I am not disputing that you know how it works, or how it works, just whether it does indeed work.

If I am misunderstanding how it works, I'm all ears.