Spec Miata Community   
search | help | calendar | games | forum home

  next oldest topic   next newest topic
» Hello Spec Miata Community » SpecMiata.com » Spec Miata Setup Guide » FAQ Week #1 - Rear Swaybar (Page 1)

 - Email this page to someone! | Subscribe To Topic
Page 1 of 2 1  2  next » 
 
Author Topic: FAQ Week #1 - Rear Swaybar
Todd Lamb Verified Driver Made Donation to Website Series Champ
Playboy Mazda MX-5 Cup Champion 2009

Region: SE Div, Atlanta
Car #: EddieFur
Year : Party like it's ____
Posts: 952
Status: Offline
Icon 1 posted  Profile for Todd Lamb   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

In an effort to start some handling discussions on the various adjustments available on a SM, the topic of this week's FAQ is the Rear Swaybar.

The obvious part is that a softer rear swaybar setting (holes closest to the ends for the best leverage) will increase rear grip, i.e. tighten up the car.

A stiffer rear swaybar setting (holes farthest from the ends for less leverage) will decrease rear grip, i.e. loosen up the car.

End link adjustments are important for no pre-load, and swaybars should be disconnected for scaling.

Further questions, comments, suggestions, tricks, tips? e.g. is there enough adjustment? too much? Bind in the mounts? Preload possibilities?

--------------------
Mazdaspeed // SafeRacer // Traqmate // OPM Autosports // East Street Auto // Cobalt Friction
Racers Edge Motorsports Rolex GT RX-8 // i-MOTO Racing Conti Challenge MAZDASPEED3
Twitter: http://www.twitter.com/toddspeed

Mike Tesch Made Donation to Website
Member

Posts: 65
Status: Offline
Icon 1 posted  Profile for Mike Tesch   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

deleted

mullet


Region: SW
Car #:
Year : 93
Posts: 121
Status: Offline
Icon 1 posted  Profile for mullet     Edit/Delete Post  Report this post to a Moderator

don't forget, new rule for this year regarding bars, you can disconnect one link on the swaybar .

Z-MAN Verified Driver
Member

Region: Mid-South
Car #: 54
Year : 1990
Posts: 711
Status: Offline
Icon 1 posted  Profile for Z-MAN     Edit/Delete Post  Report this post to a Moderator

quote:
Originally posted by mullet:
don't forget, new rule for this year regarding bars, you can disconnect one link on the swaybar .

This does seam to make the car more friendly in the wet...

Z-Man

Todd Lamb Verified Driver Made Donation to Website Series Champ
Playboy Mazda MX-5 Cup Champion 2009

Region: SE Div, Atlanta
Car #: EddieFur
Year : Party like it's ____
Posts: 952
Status: Offline
Icon 1 posted  Profile for Todd Lamb   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

True dat!

What about one side being in a different hole than the other?

--------------------
Mazdaspeed // SafeRacer // Traqmate // OPM Autosports // East Street Auto // Cobalt Friction
Racers Edge Motorsports Rolex GT RX-8 // i-MOTO Racing Conti Challenge MAZDASPEED3
Twitter: http://www.twitter.com/toddspeed

Jim Daniels
Guest


Status: Offline
Icon 1 posted    Edit/Delete Post  Report this post to a Moderator

Text book thinking hard to apply when we cannot change the bar size.

Rye
Member

Region: CACC British Columbia
Car #: 34
Year : 1991
Posts: 115
Status: Offline
Icon 1 posted  Profile for Rye     Edit/Delete Post  Report this post to a Moderator

Because the swaybar ends are essentially working against each other, setting the links in different holes gives you the average leverage of each side. This allows you to make "half" adjustments of stiffness.

Rye
Member

Region: CACC British Columbia
Car #: 34
Year : 1991
Posts: 115
Status: Offline
Icon 1 posted  Profile for Rye     Edit/Delete Post  Report this post to a Moderator

It shouldn't make any difference which side is set to stiff or soft.

John Mueller Verified Driver Made Donation to Website
Okay, not the slowest anymore...

Region: SoCal
Car #: 13
Year : 1992
Posts: 847
Status: Offline
Icon 1 posted  Profile for John Mueller   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

NEWBIE ALERT [Confused]

So, am I to assume that adjustable ends will give you degrees of your desired outcome regardless of which hole you mount to?
  • Shorter the link = more grip (understeer)
  • Longer the link = less grip (oversteer)

Then, if I my above hunch is correct:
  • Is there a rule for setting the bar and the linls for a baseline?
  • What would be a recommended at track adjustment increments be (in numb of turns or distance)?


Ohhh, this is good stuff [thumbsup]

--------------------
Thanks,
John Mueller
NASA SM National Director
http://www.Weekend-Racer.com
#13 "Tiger Miata" - 2009 SoCal SSM Champion

Todd Lamb Verified Driver Made Donation to Website Series Champ
Playboy Mazda MX-5 Cup Champion 2009

Region: SE Div, Atlanta
Car #: EddieFur
Year : Party like it's ____
Posts: 952
Status: Offline
Icon 1 posted  Profile for Todd Lamb   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

The handling is affected by the hole the end link bolt goes through on the swaybar itself, not the length of the links. Shortening or lengthening the links is done to eliminate any pre-load on the bar.

If the bar has pre-load you'll get more roll resistance one direction than the other. Not exactly the preferred method of tuning, but I bet somebody out there is tuning that way.

In addition, I've heard the argument that it DOES matter which side is set to stiffer or softer if using unlike holes.

--------------------
Mazdaspeed // SafeRacer // Traqmate // OPM Autosports // East Street Auto // Cobalt Friction
Racers Edge Motorsports Rolex GT RX-8 // i-MOTO Racing Conti Challenge MAZDASPEED3
Twitter: http://www.twitter.com/toddspeed

Rye
Member

Region: CACC British Columbia
Car #: 34
Year : 1991
Posts: 115
Status: Offline
Icon 1 posted  Profile for Rye     Edit/Delete Post  Report this post to a Moderator

After making my post about the different holes on each end of the sway bar, I thought about it and I have to agree with Todd that it does make a difference.

You would have more leverage (softer) on the side with the hole furthest out, and less leverage (firmer) on the side with the hole closer in.

I'm not sure how you could benifit from this sort of "tuning", but I'm sure someone else has found a way!

Richard

Jim Boemler Verified Driver
Veteran Member

Region: NWR, OR
Car #: 30
Year : 1992
Posts: 8523
Status: Offline
Icon 1 posted  Profile for Jim Boemler     Edit/Delete Post  Report this post to a Moderator

quote:
Originally posted by Todd Lamb:

In addition, I've heard the argument that it DOES matter which side is set to stiffer or softer if using unlike holes.

Can you quote the argument for us? I think it's gonna be BS, but I'd like to hear the reasoning.

jim

--------------------
Just a clown

Todd Lamb Verified Driver Made Donation to Website Series Champ
Playboy Mazda MX-5 Cup Champion 2009

Region: SE Div, Atlanta
Car #: EddieFur
Year : Party like it's ____
Posts: 952
Status: Offline
Icon 1 posted  Profile for Todd Lamb   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

The moment down the center of the bar is the same, but it equates to different forces on each wheel due to the effective length of the arm being different on each side.

--------------------
Mazdaspeed // SafeRacer // Traqmate // OPM Autosports // East Street Auto // Cobalt Friction
Racers Edge Motorsports Rolex GT RX-8 // i-MOTO Racing Conti Challenge MAZDASPEED3
Twitter: http://www.twitter.com/toddspeed

Jim Boemler Verified Driver
Veteran Member

Region: NWR, OR
Car #: 30
Year : 1992
Posts: 8523
Status: Offline
Icon 1 posted  Profile for Jim Boemler     Edit/Delete Post  Report this post to a Moderator

I think you'll find the reverse is true. That is, the moment is different (as seen by the arm at it's attachment point), but the force at each attachment point is the same (precisely because the effective lengths are different).

jim

--------------------
Just a clown

Casey Z Verified Driver Made Donation to Website
MegaModerator

Region: MidDiv
Car #: 13
Year : 92
Posts: 2873
Status: Offline
Icon 1 posted  Profile for Casey Z     Edit/Delete Post  Report this post to a Moderator

quote:
Originally posted by Jim Boemler:
I think you'll find the reverse is true. That is, the moment is different (as seen by the arm at it's attachment point), but the force at each attachment point is the same (precisely because the effective lengths are different).

jim

I have been stewing over this all evening and tend to agree with you Jim. However, seeing as the moment has to be transfered from one arm to the other and that transfer is both dynamic and not immediate there would seem to be some change in handling. It would be dynamic, but it would be there. What are your thoughts on this one? Still thinking this through.

Your buttometer would have to be pretty good to sense this, but I do think it could be measured with the proper gear.

I think the main issues are time, force and moment arms. That and the recognitio n that it isn't a static measurement.

--------------------
----------------
Z Brothers Racing / East Street Auto

Casey Z - 1.6 Kettle
MidDiv National #13

Todd Lamb Verified Driver Made Donation to Website Series Champ
Playboy Mazda MX-5 Cup Champion 2009

Region: SE Div, Atlanta
Car #: EddieFur
Year : Party like it's ____
Posts: 952
Status: Offline
Icon 1 posted  Profile for Todd Lamb   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

You're talking about a different scenario Jim, and while your assumptions are correct, you've just made my point in a different way.

Take any one given turn, and what I'm saying applies - the moment in must equal the moment out. The only difference is the force applied due to the length difference.

In your scenario - yes with a turn to the left and a turn to the right, different holes on each side will produce, say a 1# force, multiplied by a different length, will give you a different moment. But then again, that different moment is applied through the bar to the other end, which also equates to a different force.

For simplicity, let's say one hole is at 1' from the bar centerline, and another hole is at 2'. You turn one direction, and 1# is applied at the 1' hole, resulting in a 1 ft-lb moment through the bar. Apply that to the 2' hole, and you get a 1/2# force.

Now you turn the other way. 1# of force is applied at the 2' hole, resulting in a 2 ft-lb moment. Transfer that through to the 1' hole on the other end, and you get a 2# force.

Thus, roll stiffness is not equal left to right if the holes are not equal distance from the bar mount centerline.

--------------------
Mazdaspeed // SafeRacer // Traqmate // OPM Autosports // East Street Auto // Cobalt Friction
Racers Edge Motorsports Rolex GT RX-8 // i-MOTO Racing Conti Challenge MAZDASPEED3
Twitter: http://www.twitter.com/toddspeed

Jim Boemler Verified Driver
Veteran Member

Region: NWR, OR
Car #: 30
Year : 1992
Posts: 8523
Status: Offline
Icon 1 posted  Profile for Jim Boemler     Edit/Delete Post  Report this post to a Moderator

While nothing in the car is truly static, I don't see any "dynamics" playing a role here. At any point in time the forces on the arm have to be in balance. I also see the "moment transfer" as a false analysis. During the time the bar is in play (meaning when the wheels are not moving in sync), there isn't so much a transfer of force as a resistance to force. That is, the bar isn't rigid, with movement transferred from one end to the other -- it's a spring, which dissipates the force by NOT moving at the other end.

jim

--------------------
Just a clown

Jim Boemler Verified Driver
Veteran Member

Region: NWR, OR
Car #: 30
Year : 1992
Posts: 8523
Status: Offline
Icon 1 posted  Profile for Jim Boemler     Edit/Delete Post  Report this post to a Moderator

I think you're missing the same point, Todd. That is, putting a one ft-lb moment at one end produces a one ft-lb moment at the other end only if the bar doesn't bend. But it DOES bend -- it's a torsion bar.

jim

--------------------
Just a clown

Casey Z Verified Driver Made Donation to Website
MegaModerator

Region: MidDiv
Car #: 13
Year : 92
Posts: 2873
Status: Offline
Icon 1 posted  Profile for Casey Z     Edit/Delete Post  Report this post to a Moderator

quote:
Originally posted by Jim Boemler:
While nothing in the car is truly static, I don't see any "dynamics" playing a role here. At any point in time the forces on the arm have to be in balance. I also see the "moment transfer" as a false analysis. During the time the bar is in play (meaning when the wheels are not moving in sync), there isn't so much a transfer of force as a resistance to force. That is, the bar isn't rigid, with movement transferred from one end to the other -- it's a spring, which dissipates the force by NOT moving at the other end.

jim

Jim,

Not arguing, trying to understand. The spring theory works as long as the spring is symetrical. In this case it is not and it is being acted on by the other connecter in this case the connection to the other lower control arm. That is where I am getting to the dynamic portion of the equation. I may wimp out and start working out the math tomorrow. I am pretty sure it is there. But probably minute...

--------------------
----------------
Z Brothers Racing / East Street Auto

Casey Z - 1.6 Kettle
MidDiv National #13

Jim Boemler Verified Driver
Veteran Member

Region: NWR, OR
Car #: 30
Year : 1992
Posts: 8523
Status: Offline
Icon 1 posted  Profile for Jim Boemler     Edit/Delete Post  Report this post to a Moderator

Hmmmmmmmm. Well, you should be able to prove that a progressive-wound spring puts more force at one end than the other, too!

jim

--------------------
Just a clown

Todd Lamb Verified Driver Made Donation to Website Series Champ
Playboy Mazda MX-5 Cup Champion 2009

Region: SE Div, Atlanta
Car #: EddieFur
Year : Party like it's ____
Posts: 952
Status: Offline
Icon 1 posted  Profile for Todd Lamb   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

Of course it twists once the moment exceeds the torsional rigidity - where do you think it gets the forces that twist it? Moment = Force x Distance. The simple example above applies to any given point in time during cornering.

For any given corner, in order to twist, it has to get equal and opposite moments from each end of the bar. If it doesn't, it will rotate instead of twist. Try unbolting one end of your swaybar and see if you can get any force out of it in torsion.

--------------------
Mazdaspeed // SafeRacer // Traqmate // OPM Autosports // East Street Auto // Cobalt Friction
Racers Edge Motorsports Rolex GT RX-8 // i-MOTO Racing Conti Challenge MAZDASPEED3
Twitter: http://www.twitter.com/toddspeed

Casey Z Verified Driver Made Donation to Website
MegaModerator

Region: MidDiv
Car #: 13
Year : 92
Posts: 2873
Status: Offline
Icon 1 posted  Profile for Casey Z     Edit/Delete Post  Report this post to a Moderator

quote:
Originally posted by Jim Boemler:
Hmmmmmmmm. Well, you should be able to prove that a progressive-wound spring puts more force at one end than the other, too!

jim

When and in what proportion? Once again, not a static measure. Please don't make me get out my books. Give me the answer! [thumbsup]

Just kidding.

--------------------
----------------
Z Brothers Racing / East Street Auto

Casey Z - 1.6 Kettle
MidDiv National #13

Todd Lamb Verified Driver Made Donation to Website Series Champ
Playboy Mazda MX-5 Cup Champion 2009

Region: SE Div, Atlanta
Car #: EddieFur
Year : Party like it's ____
Posts: 952
Status: Offline
Icon 1 posted  Profile for Todd Lamb   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

If you took that progressive-wound spring and put one end on a lever arm, you'd have a comparable scenario where force in is not equal to force out. AKA pushrod suspension.

--------------------
Mazdaspeed // SafeRacer // Traqmate // OPM Autosports // East Street Auto // Cobalt Friction
Racers Edge Motorsports Rolex GT RX-8 // i-MOTO Racing Conti Challenge MAZDASPEED3
Twitter: http://www.twitter.com/toddspeed

Rye
Member

Region: CACC British Columbia
Car #: 34
Year : 1991
Posts: 115
Status: Offline
Icon 1 posted  Profile for Rye     Edit/Delete Post  Report this post to a Moderator

Picture one end of your bar having a ten foot long arm, and the other with a two inch arm. I think you will agree that the long arm is very easy to move up and down relative to the short arm, regardless of whether the shaft has some give (torsional spring) in it or not.

The comparison to the linear spring is not valid, because both end forces are acting DIRECTLY against each other, and not through different arms.

I think this is really a simple lever and fulcrum situation, regardless of whether it is static or dynamic. It could be compared to a see-saw with a rigid board, or a springy one.

Jim Boemler Verified Driver
Veteran Member

Region: NWR, OR
Car #: 30
Year : 1992
Posts: 8523
Status: Offline
Icon 1 posted  Profile for Jim Boemler     Edit/Delete Post  Report this post to a Moderator

I did give you the answer, Casey! Get out your books if you need to. [Wink]

Todd, are you saying that reversing the ends of a progressive spring makes it behave differently? Or that if you apply X pounds of force at one end, some other number of pounds will be felt at the other end?

jim

--------------------
Just a clown

Casey Z Verified Driver Made Donation to Website
MegaModerator

Region: MidDiv
Car #: 13
Year : 92
Posts: 2873
Status: Offline
Icon 1 posted  Profile for Casey Z     Edit/Delete Post  Report this post to a Moderator

Jim you are killing me.

The question is still when and in what proportion?

You really believe or better yet can show math that proves it is not dynaminc in some way? Sorry I don't think so. Think milliseconds, not static measurements.

--------------------
----------------
Z Brothers Racing / East Street Auto

Casey Z - 1.6 Kettle
MidDiv National #13

Jim Boemler Verified Driver
Veteran Member

Region: NWR, OR
Car #: 30
Year : 1992
Posts: 8523
Status: Offline
Icon 1 posted  Profile for Jim Boemler     Edit/Delete Post  Report this post to a Moderator

If you want to deal in milliseconds, I agree there can be differences, but they're due to things you haven't even considered yet. Friction in the bushings. Hysteresis in the elasticity of the bushing lube. Coriolis forces. Maybe asymmetric charging of the flux capacitor.

Hope you got a Big Book. [Wink]

jim

PS: just so I'm not accused of evading your two key questions: When? Always -- if the theory breaks any time, then it's at least incomplete, and probably false. Proportion? Bullshit is proportional to the square of the number of people flinging it.

--------------------
Just a clown

Rye
Member

Region: CACC British Columbia
Car #: 34
Year : 1991
Posts: 115
Status: Offline
Icon 1 posted  Profile for Rye     Edit/Delete Post  Report this post to a Moderator

I really don't agree that explaining a simple mechanical process is flinging BS, but I guess you are entitled to your opinion.

The "spring" part of the swaybar is essentially the shaft between the arms on the ends. The torque at each end of that straight shaft is of course equal at each end. The difference in the effect on the suspension is proportional to the length of the lever at each end. If this were not true, then moving the links on both sides by the same amount would not have any effect on the overall stiffness. The "springiness" of the bar hasn't changed, just the mechanical advantage that is utilizing the spring / torque shaft.

Rye
Member

Region: CACC British Columbia
Car #: 34
Year : 1991
Posts: 115
Status: Offline
Icon 1 posted  Profile for Rye     Edit/Delete Post  Report this post to a Moderator

By the way, thank you Mr Drago, for explaining how you can use this assymetrical swaybar setting to fine tune your suspension.

Richard

Dusty Bottoms Verified Driver Made Donation to Website
99 all the way!

Region: Lone Star
Year : 1990
Posts: 4253
Status: Offline
Icon 1 posted  Profile for Dusty Bottoms     Edit/Delete Post  Report this post to a Moderator

For simplicity's sake assume the bar is not flexing, has frictionless bushings, and is not moving right now.

The side with the shorter moment arm will apply half the force...but remember at the other side you have a longer moment arm...so nobody really cares about how much force is applied to the bar...the important part is how much force is applied to the inside wheel. Assuming frictionless bushings I say it doesn't matter whether you have asymmetric settings or not.

Homework for you guys...the bar moves sideways in the bushings under load with the heim joint links, how does that affect the forces in an asymmetric vs. symmetric setting? [Smile]

Edit: disclaimer: I haven't had my coffee yet. [Smile]

--------------------
"Your victory is tainted! Asterisk! Asterisk!!!"--Lisa Simpson

Jim Boemler Verified Driver
Veteran Member

Region: NWR, OR
Car #: 30
Year : 1992
Posts: 8523
Status: Offline
Icon 1 posted  Profile for Jim Boemler     Edit/Delete Post  Report this post to a Moderator

Rye, before you get all riled up, you might consider that I include myself among the flingers. [Wink]

jim

PS: if it matters which end has more leverage on the bar, then it should really matter which end you disconnect in the rain. For a clockwise track, which one should I disconnect?

--------------------
Just a clown

Todd Lamb Verified Driver Made Donation to Website Series Champ
Playboy Mazda MX-5 Cup Champion 2009

Region: SE Div, Atlanta
Car #: EddieFur
Year : Party like it's ____
Posts: 952
Status: Offline
Icon 1 posted  Profile for Todd Lamb   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

quote:
Originally posted by Antonio Garza:
The side with the shorter moment arm will apply half the force...but remember at the other side you have a longer moment arm...so nobody really cares about how much force is applied to the bar...the important part is how much force is applied to the inside wheel.

You lost me at the first sentence - the shorter arm transfers more force. Everybody should care how much force (torsion) is applied through the bar by the outside suspension, because that force, divided by the distance, IS the force applied by the bar to the inside suspension. I did the math in the example above to show the difference - the length of the arms does not cancel out this difference, it creates the difference. If you re-read my post and still feel this way please explain when the laws of physics were changed.

[Divide by zero error]
Jim, there are so many holes in your logic and examples I don't even know where to begin. If you're so confident you're right why don't you give us an example with calculations (see my example above) to prove your point?

Myth Busted: When one end is disconnected (rain setup) there is no moment in the bar because there are no opposing forces from that end. So of course it doesn't matter which end you disconnect, or even if you cut the bar in half - it's no longer acting as roll resistance. If the rules allowed it, you could bolt one end to the roof in the rain and leave it dangling...and guess what? It still wouldn't matter which end was flapping in the breeze!
[/Divide by zero error]

--------------------
Mazdaspeed // SafeRacer // Traqmate // OPM Autosports // East Street Auto // Cobalt Friction
Racers Edge Motorsports Rolex GT RX-8 // i-MOTO Racing Conti Challenge MAZDASPEED3
Twitter: http://www.twitter.com/toddspeed

Casey Z Verified Driver Made Donation to Website
MegaModerator

Region: MidDiv
Car #: 13
Year : 92
Posts: 2873
Status: Offline
Icon 1 posted  Profile for Casey Z     Edit/Delete Post  Report this post to a Moderator

quote:
Originally posted by Jim Boemler:
[QBCoriolis forces. Maybe asymmetric charging of the flux capacitor.
[/QB]

[rolling on floor laughin]

And now we know why you get the clown role. That is good!

--------------------
----------------
Z Brothers Racing / East Street Auto

Casey Z - 1.6 Kettle
MidDiv National #13

Dusty Bottoms Verified Driver Made Donation to Website
99 all the way!

Region: Lone Star
Year : 1990
Posts: 4253
Status: Offline
Icon 1 posted  Profile for Dusty Bottoms     Edit/Delete Post  Report this post to a Moderator

OK all caffeinated now.

I meant to say that with the bigger moment arm, the bar sees more torque applied to it given the same force. This is where I was mistaken before...I failed to complete my own math.

Assume equal forces on both sides due to the chassis roll (on equal corners, etc.). One side you have 3cm moment arm, on the other you have 6cm. Assume the force to be 20kg. T=rXF

T=3cm*20kg=60cm-kg
60cm-kg=6cm*x
x=10kg

Apologies to Todd et. al. for wrongly contradicting you guys.

That wasn't enough for me...I built a little rig with piano wire, some nylon tubing, etc. I used some scrap brass, and a gram scale. The brass piece I used weighs 107-108g

Placing the scale load point 5cm from the center of the bar (90į bend on the bar), and placing the weight 5cm from the center of the bar...the scale reads 107g.

Placing the scale load point 7cm away, and the weight 5cm away, yields 85g.

Placing the scale load point 5cm away, and the weight 7cm away yielded 147g

Deflections...I would say the bar/wire had probably a little more flex in scale than our bars do...but not enough to throw results too far off.

The thing I'm not accounting for is all the movement. My jig and my math assumes the bushings are static...when in reality the car is moving around, or resisting movement as a result of the bar. The distances traveled by the endlinks are different based on the position...and I think that's where most of us struggle with as far as accounting for all the variables. I'd love to have Mark Bennett...a real expert on all this stuff weigh in.

Thanks guys for forcing me to sit down and do the math.

--------------------
"Your victory is tainted! Asterisk! Asterisk!!!"--Lisa Simpson

Dusty Bottoms Verified Driver Made Donation to Website
99 all the way!

Region: Lone Star
Year : 1990
Posts: 4253
Status: Offline
Icon 1 posted  Profile for Dusty Bottoms     Edit/Delete Post  Report this post to a Moderator

OK I thought a little more about what I said about letting the mounting points roll and I went back to my jig. I took the weight off the jig to let it "roll" and the weight was reduced significantly. Here's a picture of the setup:

 -

I'll let others do the more complicated math...I was just in a break between honey-do's [Big Grin]

--------------------
"Your victory is tainted! Asterisk! Asterisk!!!"--Lisa Simpson

Rye
Member

Region: CACC British Columbia
Car #: 34
Year : 1991
Posts: 115
Status: Offline
Icon 1 posted  Profile for Rye     Edit/Delete Post  Report this post to a Moderator

[QUOTE]Originally posted by Jim Boemler:
[QB] Rye, before you get all riled up, you might consider that I include myself among the flingers. [Wink]

It's good to see that we can agree on something! [Smile]

Todd Lamb Verified Driver Made Donation to Website Series Champ
Playboy Mazda MX-5 Cup Champion 2009

Region: SE Div, Atlanta
Car #: EddieFur
Year : Party like it's ____
Posts: 952
Status: Offline
Icon 1 posted  Profile for Todd Lamb   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

Wow Antonio - pretty cool setup!

I do however, think that as you've shown this is a static "story problem". Yes it's all moving but if you take a snapshot in time (just one of numerous data points, i.e. mm of suspension travel) you get the basic idea of the forces relative to the asymmetrical setup. Friction, inertia, and all the other factors, while not insignificant, are inconsequential to the discussion at hand.

If you wanted to factor all that in - I'll be on the deck drinking a beer and waiting for the results [Big Grin] I never really cared for differential equations.

--------------------
Mazdaspeed // SafeRacer // Traqmate // OPM Autosports // East Street Auto // Cobalt Friction
Racers Edge Motorsports Rolex GT RX-8 // i-MOTO Racing Conti Challenge MAZDASPEED3
Twitter: http://www.twitter.com/toddspeed

Casey Z Verified Driver Made Donation to Website
MegaModerator

Region: MidDiv
Car #: 13
Year : 92
Posts: 2873
Status: Offline
Icon 1 posted  Profile for Casey Z     Edit/Delete Post  Report this post to a Moderator

AG, you have GOT TO GET A LIFE MAN!!! [Eek!]

Just kidding, that is a pretty neat little experiment and illustrates what we are all BS'ing about pretty well. Now get back to work before I tattle on you to your wife... [Wink]

--------------------
----------------
Z Brothers Racing / East Street Auto

Casey Z - 1.6 Kettle
MidDiv National #13

Dusty Bottoms Verified Driver Made Donation to Website
99 all the way!

Region: Lone Star
Year : 1990
Posts: 4253
Status: Offline
Icon 1 posted  Profile for Dusty Bottoms     Edit/Delete Post  Report this post to a Moderator

Honestly, it took me 5 min. to look for the parts, 5 min. to put it together...I played with it 10min. maybe. I thought of whipping out my RC car tweak board or scales and one of the cars to illustrate it...I may get to it just for fun..and I've been meaning to get one running and take it to a race anyway.

--------------------
"Your victory is tainted! Asterisk! Asterisk!!!"--Lisa Simpson

Steve Scheifler Verified Driver Made Donation to Website
Veteran Member

Region: STL
Car #: 82
Year : 1991
Posts: 2136
Status: Offline
Icon 1 posted  Profile for Steve Scheifler     Edit/Delete Post  Report this post to a Moderator

Iíve seen this exact topic debated a number of times on different sites and always zoned out before any of the engineers managed a clear checkmate, but Iíve never seen anyone create a model to test it. Way to go Antonio! But, Iím not yet convinced that the difference is real because the center of the bar does seem like a simple torsional spring connecting two loaded arms, one applying force and one resisting it. But since both are seen as applying equal but opposite forces, the amount of twist in the bar (and therefore roll resistance) should be the same no mater which side is ďloadedĒ. But then I remember that Iím no engineer so Iím inclined to believe those of you who use the most complex logic. [Wink] Or models, I really like the model.

Question: If rather than an arm, one end was a splined shaft into a block mounted on a control arm, what happens to your math? If Iím not mistaken, some race car suspensions have been designed with mono-arm anti-sway bars. What did they know, or not know?

Todd Lamb Verified Driver Made Donation to Website Series Champ
Playboy Mazda MX-5 Cup Champion 2009

Region: SE Div, Atlanta
Car #: EddieFur
Year : Party like it's ____
Posts: 952
Status: Offline
Icon 1 posted  Profile for Todd Lamb   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

Assuming the amount of twist is the same, the forces on each side of the bar (transferred to the suspension) are different because the length of the arms are different.

Got any pics/diagrams of the mono-arm swaybar? Sounds interesting....

--------------------
Mazdaspeed // SafeRacer // Traqmate // OPM Autosports // East Street Auto // Cobalt Friction
Racers Edge Motorsports Rolex GT RX-8 // i-MOTO Racing Conti Challenge MAZDASPEED3
Twitter: http://www.twitter.com/toddspeed

Steve Scheifler Verified Driver Made Donation to Website
Veteran Member

Region: STL
Car #: 82
Year : 1991
Posts: 2136
Status: Offline
Icon 1 posted  Profile for Steve Scheifler     Edit/Delete Post  Report this post to a Moderator

Something about the wording of your answer makes me pause and wonder if the dynamics involved are being factored in correctly. Are you positive that in a real-world situation the forces on each end are the same if the lever arms are the same, or are they inherently different during cornering loads due to the suspension design? It just seems like something is being left out (other than my education that is).

Sorry, no pics or diagrams, but Iíll see what I can find.

Dwayne Hoover Verified Driver Made Donation to Website
Veteran Member

Posts: 3138
Status: Offline
Icon 1 posted  Profile for Dwayne Hoover     Edit/Delete Post  Report this post to a Moderator

"Everything is a spring".

http://www.whiteline.com.au/articles/NASIOC_post_assymetric_adj.pdf

Juan Pineda Verified Driver Made Donation to Website
Veteran Member

Region: San Francisco
Car #: 34
Year : 1992
Posts: 2279
Status: Offline
Icon 1 posted  Profile for Juan Pineda   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

I'm going to agree with Antonio (and others) here -- using different length arms on the sway bars arms will produce asymmetrical handling results. It's simple leverage:

F_right * L_right = F_left * L_left
where F is force, L is length of arm

So:

F_right = F_left * L_left / L_right
F_left = F_right * L_right / L_left

i.e. If the arms are different lengths, then forces transferred from right to left are different than from left to right.

The fact that the torsion bar twists does not affect the leverage, and the equations above are unchanged regardless of the stiffness of the torsion bar. This is similar to a simple spring, where the force that you apply to the spring is the same as the force the spring applies to it's stop, regardless of how stiff the spring is, or how much it is compressed.

Steve, I don't quite understand your question.

-Juan

--------------------
www.ArtOfRoadRacing.com Race Craft Clinic - Thunderhill - 30 Jan 2011

Steve Scheifler Verified Driver Made Donation to Website
Veteran Member

Region: STL
Car #: 82
Year : 1991
Posts: 2136
Status: Offline
Icon 1 posted  Profile for Steve Scheifler     Edit/Delete Post  Report this post to a Moderator

quote:
Originally posted by Juan Pineda:
... This is similar to a simple spring, where the force that you apply to the spring is the same as the force the spring applies to it's stop, regardless of how stiff the spring is, or how much it is compressed.

Steve, I don't quite understand your question.

-Juan

But to some of us without advanced degrees, that sounds like an argument against there being a difference. [Confused]

Sorry, I can't do a better job of asking a question that I don't' understand! I'm seeing things in the peripheral vision of my understanding. I sense something is there but I can't make it out.

Steve Scheifler Verified Driver Made Donation to Website
Veteran Member

Region: STL
Car #: 82
Year : 1991
Posts: 2136
Status: Offline
Icon 1 posted  Profile for Steve Scheifler     Edit/Delete Post  Report this post to a Moderator

quote:
Originally posted by MBennett:
"Everything is a spring."

http://www.whiteline.com.au/articles/NASIOC_post_assymetric_adj.pdf

Interesting, though I'm still trying to figure out what some of the values are. What are the large ones above the units of force, that are averages of the three values above that? Does the math people have been quoting predict the essentially fixed difference in those between, for example, Med/Hard and Hard/Med, regardless of the pump deflection? What about the consistent lack of change in force for the middle tow deflection values? Very odd at a glance.

Back to my non-question as I think it may relate to the above linked document. Is it valid to treat one end as "fixed" and the other as "pumped" when both are attached to the suspension of a cornering automobile?

Dwayne Hoover Verified Driver Made Donation to Website
Veteran Member

Posts: 3138
Status: Offline
Icon 1 posted  Profile for Dwayne Hoover     Edit/Delete Post  Report this post to a Moderator

quote:
Originally posted by Steve Scheifler:
Back to my non-question as I think it may relate to the above linked document. Is it valid to treat one end as "fixed" and the other as "pumped" when both are attached to the suspension of a cornering automobile?

What end would you wind a rubber-band airplane from?

The model is the same (mathematically) ... the rubber band airplane is a very soft torsional spring constrained at one end by a very small lever, being wound by the action of a much bigger lever. Make the rubber band a lot stiffer, make the levers at each end a lot closer in length, and then put bumpstops in the way after a few degrees of rotation and PRESTO... Miata swaybar.

The asymmetry is there, with mathematical certainty ... I'll let you guys argue whether it has an effect or not. [Wink]

But ... I'll bet you a Jim Daniels Signature Series fish scale that 95%+ of SMs have asymmetrical wheel rates due to to spring tolerance, bushing preload variance, camber difference (the tire has it's own camber too, eh?).

--------------------
Visit the Midland City Arts Festival!

Dusty Bottoms Verified Driver Made Donation to Website
99 all the way!

Region: Lone Star
Year : 1990
Posts: 4253
Status: Offline
Icon 1 posted  Profile for Dusty Bottoms     Edit/Delete Post  Report this post to a Moderator

Well my 1/8th car has the rear blade bars (the fronts are a PITA to adjust), so this is interesting and I think is different from the result posted by Mark above for blade bars.

Hopefully this comes across OK.

w=weight on that side
n=no weight on that side
-=blade flat on that side (softest)
|=blade vertical on that side (hardest)

LR on the left side, RR on the right side.
numbers are weights in oz.

n-23.1, 21.7-n
n-19.4, 49.9-w
w-50.0, 19.0-n
w-53.0, 16.1|n
n-20.5, 49.0|w
n|21.3, 48.6-w
w|52.8, 16.0-n

Unfortunately the scales are not the same..but I leveled them and zeroed them often. I bounced the car once before putting on the weights.

I started with stiff springs but couldn't see a big enough difference so I switched to the softest springs so I could see the movement. I put a big moment arm attached to the horizontal CG of the car (handle is balanced for carrying)...but way above the vertical CG to accentuate movement.

I do have the original wire type rear bar which allows adjustment of the moment arm which I'll try tomorrow.

--------------------
"Your victory is tainted! Asterisk! Asterisk!!!"--Lisa Simpson

Dusty Bottoms Verified Driver Made Donation to Website
99 all the way!

Region: Lone Star
Year : 1990
Posts: 4253
Status: Offline
Icon 1 posted  Profile for Dusty Bottoms     Edit/Delete Post  Report this post to a Moderator

I looked closer at Mark's link...they have blade bars but have 3 hole positions. The ones in my RC car are adjusted by rotating of the blades themselves.

--------------------
"Your victory is tainted! Asterisk! Asterisk!!!"--Lisa Simpson

Juan Pineda Verified Driver Made Donation to Website
Veteran Member

Region: San Francisco
Car #: 34
Year : 1992
Posts: 2279
Status: Offline
Icon 1 posted  Profile for Juan Pineda   Author's Homepage     Edit/Delete Post  Report this post to a Moderator

quote:
Originally posted by Steve Scheifler:
quote:
Originally posted by Juan Pineda:
... This is similar to a simple spring, where the force that you apply to the spring is the same as the force the spring applies to it's stop, regardless of how stiff the spring is, or how much it is compressed.

But to some of us without advanced degrees, that sounds like an argument against there being a difference. [Confused]
Steve,

Not really. Here's how it works. The torque applied by the lever on the right side of the torsion bar is the same as the torque that the torsion bar applies to the lever on the other side. This is independent of the springiness of the torsion bar, or how far it's twisted. That's the analogy with the spring.

But that's talking about torque on the torsion bar, not force on the suspension. The force that the levers apply to the suspension is affected by the lengths of the levers due to leverage. The shorter the lever, the greater the force that it will apply to the suspension, given the same amount of torque. So the side of the torsion bar with the shorter lever will apply a greater force to the suspension than the side with the longer lever. Hence the asymmetry.

-Juan

--------------------
www.ArtOfRoadRacing.com Race Craft Clinic - Thunderhill - 30 Jan 2011

 
Page 1 of 2 1  2  next » 
 

   Close Topic   Feature Topic   Move Topic   Delete Topic next oldest topic   next newest topic
 - Printer-friendly view of this topic | Subscribe To Topic
Hop To: