Okay. Why are my front left and right weights not equal since the zero roll can be thought of as a three-legged stool? And the rear weights are not equal right to left either.
There is actually a distance between the rear uprights so I figured that adjusting the bars from the bell cranks to the axles should make some difference and initially it appears to but once you settle the chassis it goes right back to the original weights.
Can someone help me understand what is actually going on here?
Does everyone with a zero roll have this issue or am I missing something?
Thanks,
JGB
77 F/mod
Zero Roll corner weights
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Martinracing98
- Posts: 170
- Joined: June 24th, 2006, 7:27 pm
Re: Zero Roll corner weights
How much different is different? Most rear suspension is truly zero roll. I think mine as the rear suspension rolls the side going up moves in the sprind slightly more than the side going down. This is do to geometry. If the geometry is progressive as the car squats this would be true. With that case a slight twist in the front torsion bar or sway bar would tilt car slightly one direction resulting in slight increase in weight of one side over the other. It should not be much though.
Re: Zero Roll corner weights
For the front weights, if you have something that is off center in the car (ballast?) then it would be difficult, if not impossible, to balance. The front is also supported by the spring pack inside the front tube. It wouldn't take much 'tweak' of that spring pack to put more load on one side than the other. Before the advent of ride height adjusters, the generally accepted way of changing the ride height was to chain the chassis to a tree or something, then put a long (strong) tube over the end of the turkey leg and "PULL" past the spring point. It was VERY difficult to perfectly balance left/right with this method.
If you have a sway bar, it too, could be twisted and cause imbalance.
As for the rear - if it's zero roll, they should balance pretty well except for friction. If you have a bell too tight on the side of the trannie (creates a LOT of friction), you can get some pretty weird looking numbers.
No self respecting 'vee guy' should even OWN a set of corner scales ... what are you trying to do - make the rest of us look bad?
Steve
If you have a sway bar, it too, could be twisted and cause imbalance.
As for the rear - if it's zero roll, they should balance pretty well except for friction. If you have a bell too tight on the side of the trannie (creates a LOT of friction), you can get some pretty weird looking numbers.
No self respecting 'vee guy' should even OWN a set of corner scales ... what are you trying to do - make the rest of us look bad?
Steve
The Racer's Wedge and now a Vortech, FV80
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DanRemmers
- Posts: 293
- Joined: June 24th, 2006, 7:21 pm
Re: Zero Roll corner weights
Yeah, how much difference are we talking? If the two rear uprights are not even, then the motor may not be level and thus tipping to one side. The frame could be warped slightly so that the motor is not parallel with the front beam. You could have a hub or axle that weighs more than the other side.
Or if the floor the scales are sitting on was not level (and the scales didn't self level) then that could cause a problem. (But things like that never happen.
)
Or if the floor the scales are sitting on was not level (and the scales didn't self level) then that could cause a problem. (But things like that never happen.
)Re: Zero Roll corner weights
If one side of a front spring sags, it basically puts a tilt in the frame, but corner weights should not change.
With zero roll, unless something in the rear spring system binds, static corner weights won't change due to anything except weight distribution.
JGB, The spring and rockers are free to flop from side to side as push rod length is altered. In other words, an adjustment of the length of a push rod will alter ride height, but the load is still equalized between both push rods. Any momentary increase in load at one push rod is quickly, and evenly distributed between both. With true zero roll design, only friction, "stiction" or a bind will allow corner loads to not equalize after changing a push rod's length. As you noted, corner weights returned once you settled the chassis.
If the three legged stool you mentioned was more like three legged table, you can easily see that moving a stack of books around on the table would affect the load distribution on the legs. All three legs remain on the floor, but loading varies with where the books are placed.
You could put a plank across two scales, with one table leg centered on the plank, and put scales under the other two legs. The weight carried by the scales under the plank should be split 50/50, even as you move the books. The weight on the other two legs will change as the books are moved.
With zero roll, unless something in the rear spring system binds, static corner weights won't change due to anything except weight distribution.
JGB, The spring and rockers are free to flop from side to side as push rod length is altered. In other words, an adjustment of the length of a push rod will alter ride height, but the load is still equalized between both push rods. Any momentary increase in load at one push rod is quickly, and evenly distributed between both. With true zero roll design, only friction, "stiction" or a bind will allow corner loads to not equalize after changing a push rod's length. As you noted, corner weights returned once you settled the chassis.
If the three legged stool you mentioned was more like three legged table, you can easily see that moving a stack of books around on the table would affect the load distribution on the legs. All three legs remain on the floor, but loading varies with where the books are placed.
You could put a plank across two scales, with one table leg centered on the plank, and put scales under the other two legs. The weight carried by the scales under the plank should be split 50/50, even as you move the books. The weight on the other two legs will change as the books are moved.
Re: Zero Roll corner weights
Guys,
Thanks for the input.
First of all, a friend loaned me the scales...
Secondly, after wrenching on everthing for hours today, I realized that stiction has a lot to do with it but still could not get the balance I thought I would see.
Finally, I checked the wheelbase, since I had bolted on a new ball joint beam and installed new motor mounts. Well, I found a significant difference which was embarrasing as you might imagine.
So now the chassis is going on a flat table and everthing is going to be reset from scratch..
Whew! What a day.. LOL
JGB,
Thanks for the input.
First of all, a friend loaned me the scales...
Secondly, after wrenching on everthing for hours today, I realized that stiction has a lot to do with it but still could not get the balance I thought I would see.
Finally, I checked the wheelbase, since I had bolted on a new ball joint beam and installed new motor mounts. Well, I found a significant difference which was embarrasing as you might imagine.
So now the chassis is going on a flat table and everthing is going to be reset from scratch..
Whew! What a day.. LOL
JGB,
Re: Zero Roll corner weights
Robert is right, aside from stiction and a tilted floor, only an uncentered weight will cause a difference in weight from side to side in a zero roll resistance Vee. This is true in the front or the rear. The starter can cause this, for example. You might want to swap the scales from side to side to see if they are different when they're measuring in the 200 pound range. John
Re: Zero Roll corner weights
I like to do all my alignment work with the shocks on full soft and no rebound. It will reduce some of the "stiction". With our rear swing axle, there is so much side loading the car won't always return to the same point. Either you have to roll the car back and forth, which is hard to do on scales, or have shuffle plates under the rear wheels. I like to set a point on the floor, make a change, then roll and bounce the car as close as the same way each time and return the car to the same point. It's a challenge but you can avoid big mistakes. You won't have to do all that when you're setting toe, just make sure the car is at race weight including driver.
The above post is for reference only and your results may vary. This post is not intended to reflect the views or opinions of SCCA and should not be considered an analysis or opinion of the rules written in the GCR.
Re: Zero Roll corner weights
what I know about corner weights on a Formula Vee goes like this,....If Steven Davis is sitting on my right front tire. and Brad Stout is sitting on the left, The right side is lighter!....The same rule applies to the rear! Now if you want to go fast ! just get one of those "Fat" Intakes!
eugene
eugene
eugene Team2Stool deviant
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billinstuart
- Posts: 201
- Joined: July 17th, 2006, 8:53 pm
Re: Zero Roll corner weights
Don't be real concerned about wheelbase variations. Be more concerned about alignment based on the centerline of the car. When you look down the inside of the rear tires you want to see the same part of the front beam on both sides. I've seen 1/2" wheelbase difference on cars that handled superbly.
There is no better way to align your car than building "a box" with strings. Forget alignment machines..they are for selling "alignments" to the public.
There is no better way to align your car than building "a box" with strings. Forget alignment machines..they are for selling "alignments" to the public.
Re: Zero Roll corner weights
Okay.. Just an update.
After bolting on the new ball joint front, and scaling the car it was 10 lbs. heavy in the right front and left rear. It was determined that it had a 1" difference in wheelbase side-to-side.. Yikes.
Put it on a flat table. Chalked the centerlines and discovered that the rear was square and the toe was correct. Squared the beam horizontally and put a spacer in the short side between the beam and the chassis. Set the toe and the camber at the front and am now happy to say that it scales even in the front and only 2 lbs out in the rear and I will write that off to stiction or some other obscure phenomena..
I hope that this exercise might possibly help others identify a problem with their chassis..
As an added note, even though my toe had been checked on the front and the rear independently, now the chassis definately seems to roll much easier indicating less scrubb..
All the best,
Johnny B.
After bolting on the new ball joint front, and scaling the car it was 10 lbs. heavy in the right front and left rear. It was determined that it had a 1" difference in wheelbase side-to-side.. Yikes.
Put it on a flat table. Chalked the centerlines and discovered that the rear was square and the toe was correct. Squared the beam horizontally and put a spacer in the short side between the beam and the chassis. Set the toe and the camber at the front and am now happy to say that it scales even in the front and only 2 lbs out in the rear and I will write that off to stiction or some other obscure phenomena..
I hope that this exercise might possibly help others identify a problem with their chassis..
As an added note, even though my toe had been checked on the front and the rear independently, now the chassis definately seems to roll much easier indicating less scrubb..
All the best,
Johnny B.
Re: Zero Roll corner weights
Johnny,
Something sounds weird here. Next time you are motivated to scale your car you might try the following. If corner weights change, there is roll resistance at the rear, rather than zero roll resistance.
With your car on the scales, what effect has steering the wheels either direction on corner weights? That would be something like creating unequal wheelbases.
If you place a shim (2 X 4) under one front wheel, what effect does it have on corner weights?
I can see a beam "steered" a bit one direction resulting in dissimilar wheelbases. I can also imagine a very slight affect on front wheel weights due to wheelbase differences. But with zero roll, rear weights should remain unchanged (percentage wise) no matter what you do at the front.
Have you checked the gravitational field in the area where you scale the car
Something sounds weird here. Next time you are motivated to scale your car you might try the following. If corner weights change, there is roll resistance at the rear, rather than zero roll resistance.
With your car on the scales, what effect has steering the wheels either direction on corner weights? That would be something like creating unequal wheelbases.
If you place a shim (2 X 4) under one front wheel, what effect does it have on corner weights?
I can see a beam "steered" a bit one direction resulting in dissimilar wheelbases. I can also imagine a very slight affect on front wheel weights due to wheelbase differences. But with zero roll, rear weights should remain unchanged (percentage wise) no matter what you do at the front.
Have you checked the gravitational field in the area where you scale the car
Re: Zero Roll corner weights
Robert,
I have returned the scales but I may look into it again once it gets warm and I feel more like being out in the garage.
Maybe it was the UFO that hovers above the house from time-to-time that affected the gravitational fields...
But, I swear the right front and left rear were 10lbs heavy before the adjustments. We found that the beam was about a degree out being low on the left side.
JGB
I have returned the scales but I may look into it again once it gets warm and I feel more like being out in the garage.
Maybe it was the UFO that hovers above the house from time-to-time that affected the gravitational fields...
But, I swear the right front and left rear were 10lbs heavy before the adjustments. We found that the beam was about a degree out being low on the left side.
JGB