Trying to Learn squat....

[Fabman]

No, that's not what would happen. The frame would rest on the axle, and there would be traction.

Exactly.

That’s what happens when bad geometry tries to pull the wheel off the track. Look at that graphic again. Regardless whether or not there is a spring in the picture, that’s irrelevant. That bad geometry compresses the spring and therefor lifts the tire off the tarmac. Bingo-no traction.


Sent from my iPad using Tapatalk

 

[Fabman]

Wait what? There would be traction by lifting the tire off the track? How in Sam Hill do you figure that?


Sent from my iPad using Tapatalk

 

[Fabman]

Are you familiar how wedge works in a chassis?
What you are doing by lifting that tire is adding wedge to the chassis. Taking weight off one pair of tires and transferring it to the opposite pair, diagonally.

Sent from my iPad using Tapatalk

 

[Fabman]

Ok I think I know what they are doing.....and it’s not quite what we are talking about. My points regarding action of the geometry and anti squat are correct. Think about it for a while.

This is a different deal.
Now, a tire will only support so much load, once you go beyond that load you over work the tire and it breaks away. In that case, taking load off the tire enhances grip. But only if you are overloading it. What they are doing by letting the car shift like that is wedging the chassis dynamically, it’s like taking out a few turns of the coil over but only in the corners. Brilliant. But this only works when the pressure on that tire exceeds the available grip and over works it.

So we have two strategies depending on the definition of the problem. If the tire needs more downforce or weight, anti squat resisting that weight transfer is the way to go. BUT if you have too much weight on that tire and you are over working it, then you need to reduce the load on that tire. That’s how wedge in stock cars works. If it’s loose you put a round in the LR weight jacker. If it’s tight you put a round in the RR.

So the real question is:
Are we over loading or under loading the tire? The fixes are very different depending on how you answer that question.

Sent from my iPad using Tapatalk

 

[Grant 302]

Are you familiar how wedge works in a chassis?
What you are doing by lifting that tire is adding wedge to the chassis. Taking weight off one pair of tires and transferring it to the opposite pair, diagonally.

I understand what a wedge is and how it works. But no, it's not that. Somewhat like it, but created only by the dynamics, etc. Nothing is overloaded. It uses the weight transfer from the roll from the turn. That changes the geometry toward more squat and more weight transfer. The roll understeer 'aims' the outside tire toward CG. All of that allows you put more power down through the outside rear tire while still in a turn.

 

[Mad Hatter]

Good day too all!! The idea was not to squat for the sake of squatting!! just to remind you guys were the car was.....



The Instant center was too far back I think.... What I was looking for is a little less anti-squat (easier if to say "squat" and I like the word better). Oddly enough I first noticed the traction problem when I was invited to a 1/4 race at the track for a publc event... I took off quickly against another Mustang fully confident that I had the faster car.....but I totally lost traction in third and let him get away. Thats when I started to think about the Instant center and saw the problems that Fabman was having..

So with all your suggestions.... (Heated, but enjoyable)..... This is how I have the car now and I think I can fine tune the line a little more. (the Green Line is the current set up). I will try to corner balance the car this week as well. Raising the rear might improve things.... The idea was not to recreate a Buick El Dorado!!

 

[Mad Hatter]

Just to get my dates right...

 

[Fabman]

I understand what a wedge is and how it works. But no, it's not that. Somewhat like it, but created only by the dynamics, etc. Nothing is overloaded. It uses the weight transfer from the roll from the turn. That changes the geometry toward more squat and more weight transfer. The roll understeer 'aims' the outside tire toward CG. All of that allows you put more power down through the outside rear tire while still in a turn.

So we’re back to roll steer, you think that’s what this is about?


Sent from my iPad using Tapatalk

 

[Grant 302]

So we’re back to roll steer, you think that’s what this is about?

No. I like roll oversteer. Even if just a little. I prefer a car that turns better or at least that's my goal for my car hardware wise right now.

I just see a way that some understeer could or would work to help make a car handle more like what Mad Hatter is looking for. I've spent a lot of time over the years thinking about how this was achieved by other cars, including the Phoenix car(s). Just reverse engineering what I think was being done. There were some posts maybe in '12 or '13 that were posted here showing some of the GS cars with the FRPP brackets on....but the LCAs clearly mounted in the OEM mount location above. I think it was one of the Roush cars and with the 'spaghetti' bar. Certainly confused me at the time.

 

[Fabman]

No. I like roll oversteer. Even if just a little. I prefer a car that turns better or at least that's my goal for my car hardware wise right now.

I just see a way that some understeer could or would work to help make a car handle more like what Mad Hatter is looking for. I've spent a lot of time over the years thinking about how this was achieved by other cars, including the Phoenix car(s). Just reverse engineering what I think was being done. There were some posts maybe in '12 or '13 that were posted here showing some of the GS cars with the FRPP brackets on....but the LCAs clearly mounted in the OEM mount location above. I think it was one of the Roush cars and with the 'spaghetti' bar. Certainly confused me at the time.

A lot of stock cars ran a shorter wheelbase on the right to do this very thing. (Leading with the RR) Problem is you have to drag it around the whole track.
I ran a spring rod on the RR trailing arm of a tour car I built for a guy, it would allow the wheelbase on the right to shorten on acceleration but snap back to square as the load decreased. That was a way of combatting power oversteer with a very powerful car.
The concept works in that situation but doesn’t sacrifice anti squat to do it.


Sent from my iPad using Tapatalk

 

[Fabman]

What’s this spaghetti bar about? That’s a new one for me...


Sent from my iPad using Tapatalk

 

[Grant 302]

What’s this spaghetti bar about? That’s a new one for me...

It was a rear sway bar that was maybe ~10mm or so. I don't think it was the Ford 13mm. At the time it was hard to understand running a bar that soft. Most of us hadn't seen anything like that on a Mustang before.

 

[Mad Hatter]

I do remember it being called a Piano wire...... the difference of "No Bar" vs a 18mm bar are very evident but then again its not a 1cm bar...

 

[Grant 302]

Yeah, I'm not sure on it's diameter either way. 10mm was just a guess based on the way it looked in the aluminum mount (looked like for the 22mm bar) and how big the nylon spacer/adapter was that wrapped it.

 

[Mad Hatter]

Twas the sage @blacksheep-1 who said "use the 13mm bar"

 

[Grant 302]

I'm sure that's a good idea. The roll and squat are 'slow' transfer events and a stiff bar would be counterproductive, IMO.

 

[Grant 302]

This is the simplest diagram I could find that depicts what I'm talking about:


from here: http://www.thecartech.com/subjects/auto_eng2/Auto_Eng_1.htm

"Transferred weight (wt)

A vehicle under acceleration due to driving has the tractive force (Fw) introduced between tires and road surface of the driving axle, and at the same time an equal but opposite inertia force (ma) acts at the point of centre of gravity crating a moment (ma h) which transfers weight (wt) or vertical loading from front to rear axle (wheels)."

The above example should apply to *any* rear suspension when under 100% anti-squat.

---------

This one a little more boiled-down to body and wheel/axle/arm assembly:



But more importantly, this diagram shows that anything UNDER 100% Anti-squat will transfer weight to the rear and create MORE traction for the rear axle. This is a slow transition and only increases as weight begins to transfer. This is what I think is needed to lift front wheels.

Over 100% Anti-squat, and the rear trailing arms 'borrow' spring rate to provide a transitional 'hit' or shock. This effect goes away as torque drops off and the spring returns toward its static height.

Both of the above will move the rear spring and need to have some control via rear dampers. Squat needs enough compression to slow the transition and then enough rebound to hold/set or slow the transition off squat. Conversely, over 100% anti-squat needs to react with high speed rebound followed by compression to slow the transition off-lift. The further away from 100% AS, the more damping either setup will need.

 

[Fabman]

This is the simplest diagram I could find that depicts what I'm talking about:


from here: http://www.thecartech.com/subjects/auto_eng2/Auto_Eng_1.htm



The above example should apply to *any* rear suspension when under 100% anti-squat.

---------

This one a little more boiled-down to body and wheel/axle/arm assembly:



But more importantly, this diagram shows that anything UNDER 100% Anti-squat will transfer weight to the rear and create MORE traction for the rear axle. This is a slow transition and only increases as weight begins to transfer. This is what I think is needed to lift front wheels.

Over 100% Anti-squat, and the rear trailing arms 'borrow' spring rate to provide a transitional 'hit' or shock. This effect goes away as torque drops off and the spring returns toward its static height.

Both of the above will move the rear spring and need to have some control via rear dampers. Squat needs enough compression to slow the transition and then enough rebound to hold/set or slow the transition off squat. Conversely, over 100% anti-squat needs to react with high speed rebound followed by compression to slow the transition off-lift. The further away from 100% AS, the more damping either setup will need.

This is what I've been trying to say...

 

[Grant 302]

This is what I've been trying to say...

Do, or do not. There is no try.

 

[Fabman]

Do, or do not. There is no try.

I do, we just speak different languages....