Handeling Thread

[JohnK]

John, after reading that post, I'm damn glad I bought a Caterham and don't have to play around like that. :rofl:

 

Tom

 

Yup. That's exactly why I'm going to the trouble of explaining what I've had to work with (and I guarantee that the particular version of my car is different in lots of different respects than the majority of this make) and how I've approached dealing with it. But, for those who have Caterhams I'm letting them know I think, from what I've learned about what it takes to make a car "handle", that I feel they've made a very good choice. And maybe, if they don't want to bother working on their car but are just curious in what such work can be all about, I'm doing my bit sharing experiences and what I THINK I've learned.

 

And it should be added, there're a lot of different things people are interested in in a Se7en. Some people are really pleased if it just goes like a scalded cat, others like the way it turns, or LOOKS - I think all of us, regardless of the make, are pretty flattered by the attention we get whenever we stop for gas or at, say, a Hooters restaurant .

Edited January 22, 2014 by JohnK

[JohnK]

John are you running a watts Linkage? I witnessed a Storker at the Track I work at, the thing was all over the place, yes it was quick in a straight line. You are quite correct Tom about the Caterham compared with some of the other kits.

 

No. It's a 5-link IRS, Subaru sourced from the uprights, axles and LSD. Stay tuned, there'll be pictures, once I figure out how to decribe what I did without writing more of a book than I already am

[JohnK]

John

 

Have you had your car corner weighed?

 

Yes. After I aligned the car myself I took it to a local shop that has the most current Hunter alighment setup and a set of Longacre scales and the experience to measure everything correctly. If you're interested, I'll post the figures, but the real purpose of getting it done at a competent shop was to see how I had done on my own. The alighment came out really accurate - I was enormously pleased that it was possible to achieve that accuracy in one's own garage. In my experience to this point, unless something's really awfult, I look at corner-weighting as fine tuning and I'm not any where near that point yet.

Edited January 22, 2014 by JohnK

[JohnK]

Considering the theoretical and the practical sides of such work . . .

-

The theoretical part involves alternately reading what different people have to say about how suspensions work and then sitting in front of your computer's monitor editing different values in a program that creates computer-generated suspensions out of collections of data that you feel your reading has enlightened you enough about to make a good guess at improving – and then calling up graphical representations (plots and figures and diagrams showing who knows what kind of relationships) that you THINK will reveal a picture of the car's behavior happening the way you want, or think you want, or might be really better than they are currently from the data that created a model of your car the way you measured it . . .

-

Think about this a little. You're doing all of this with the expectation that you will be able to find a solution in your head and with the help of some software and your understanding of what some experienced people have written that you think you understand, that when you go out to your garage and actually BUILD it (the practical side of the work), it will actually be really greatly improved and great fun to drive. Back in the '60, having to face the “smoking remains” that resulted from my doing this kind of thing and not achieving what I'd hoped for, I could always say, “Yeah man, but I was really stoned at the time.”

-

But Boeing made the 787 this way and, forgetting about the batteries, it's an amazing piece of work!

 

With the above in mind, consider the results of my analysis, the theoretical picture it resulted in and, next time, the actual construction work that it produced.

 

https://www.dropbox.com/s/adwrmmq6bw63s9a/RollOtbd-5.5inY%2B2.973Z.jpg?dl=0

 

 

(I have a stack of such graphs for different lengths and heights and different parameters that I generated as I was exploring different combinations and learning how to best plot what I thought (at any one point in time) was the best means of revealing what was going on.)

 

Making sense of the plots: What's hard about this, at least for me, is that suspension programs necessarily rely on memorizing conventions that are not in any way intuitive. You just have to remember that turning the car to the RIGHT causes the program to calculate the ROLL as being NEGATIVE. And because this is just a convention and I've confused myself a whole lot when I fumbled the relationships, I printed that relationship conspicuously in the center of this plot.

 

Chassis Roll is shown in degrees on the x-axis. The Middle and Top panels show Right and Left camber values over the range of +/- 2.5° of longitudinal chassis roll. The Bottom panel shows the movement of the roll center with Roll in inches from longitudinal centerline.

 

I'll step through this two different ways.

 

Step by step:

-Locate the value of -1.0° of Roll on the x-axis. A negative Roll value means you're turning to the Right, and therefore the y-axis value that's relevant is that of the Left camber shown on the Top panel, because that value (+0.35°) is what angle the Left/outside/laden wheel is at. Of less importance is the value of the opposite Right/inside wheel which is shown on the Middle panel as -0.40°.

And on the other side...

-Locate the value of +1.0° of Roll on the x-axis. A positive Roll value means you're turning to the Left, and therefore the y-axis value that's relevant is that of the Right camber shown on the Middle panel, because that value (in this case +0.37°) is angle what the Right/outside/laden wheel is at. Of less importance is the value of the opposite Left/inside wheel which is shown on the Top panel as -0.38°.

 

More generally:

-Of the upper two panels only half of each panel is of interest (those values that are positive) and that half of each panel applies to either a Right or Left turn when calculating camber in roll because the value that's important is the one that's for the outside wheel. E. g., for Right turn/negative Roll values Left camber is relevant, and these values are shown in the left half of the top panel; for positive Roll values Right camber is relevant, and these values are shown in thr right half of the middle panel.

Reading the degrees of Roll from the X axis at the very bottom of the plots, turning Right will cause the chassis to roll to the car's Left, loading the Left suspension – and if the turn is sharp enough to generate -1.0 degrees of roll, the left suspension will increase its Camber (the top of the left wheel will lean out) +0.35° (measured from the bottom of the wheel). As a result, this isn't bad at all bad for a setup starting from 0° static camber, and even at 2.5 degrees of roll the camber gain is +0.83°. Flip things to the other side and it's about the same for turns to the left.

-

Comparison with the original configuration where +2.0° of Roll was yielding +1.82° camber change on the outside wheel, and achieving +0.72° camber change instead with the the modified configuration at the same amount of Roll pleases me. Had the car's cornering not shown as much oversteer, I certainly would not have gone through all this trouble, and the original data certainly jibs with the reason for the car's behavior in this respect.

 

 

It is especially heartening that these values are based on the numbers I got from measuring the locations of the original upper A-arms and associated bits on the car when I first acquired it and had taken it down to the bare chassis. And with the prototypes I cobbled together built from my modified dimensions, I was able to verify that the camber values that came from the program and the values I measured with the car when aligned with the modified parts were satisfyingly close, and certainly part of the same sheet-music.

 

The inside wheels start out in negative camber and get to -1.1°. While it is certainly better to have both right and left wheels perpendicular to the road surface, the inside wheel does less work and its camber is correspondingly less critical. Weight transfer across the chassis is least when the roll center is on the ground, but still the outside wheel winds up carrying more of the cornering force and, as such, plays the most critical role.

 

I ran across a section in Smith's Tune... (pg. 18) on the behavior of a racing tire which showed the coefficient of friction (CF) plotted against camber indicated that the greatest CF occurred between -1° and -2° due to something called 'camber thrust', and that the CF was generally lower during positive camber than negative camber due to the way the contact patch distorted. Nett, while it's not too bad to run into a bit of negative camber, even a bit of positive camber decreases friction relatively quickly.

 

 

Given this behavior in Roll, the setup I'll might start with will be to have static camber start at -1.5° to -2.0° which would allow the tires to take taking advantage of the tire's camber thrust over much of the chassis' roll range.

 

However, remember that this was a “compromise”?. . .

 

And the less-than-desirable camber behavior in Bump that this configuration results in is shown on

 

https://www.dropbox.com/s/mil8y9nkd3g7c5z/Ride-OutBd%20-5.5Y%2B2.973Z.jpg?dl=0

 

On a track, where the road is likely to be smooth, this probably isn't too bad. (When I look at this plot I have to keep reminding myself that spring/shock compression in Roll does not do the same thing to the suspension geometry as compression in Ride.) Even if static camber is set at -1.5° on both sides this hopefully won't be as gastly as it might appear given

a) that you can go (as per Smith's graph, above) pretty negative in camber without losing it all (-3° is what is shown before the coefficient of friction really starts to fall off), and

b)that there's a difference in road quality between the typical twisties out in the country and Baja. (at least where I live). Still, I'll make it a point to be realcareful until I see how this setup behaves when I'm on corners that are rough. One of the recommendations you'll read is that, when you align your car, keep a notebook with records of not only what dimension all the links have, but also the number of threads showing, and especially, how many turns it takes to get from one camber setting to another. This is where such advice comes home – 'specially if you didn't take it at the time, like me.

 

 

When I bought WinGeo3, and then spent what I considered an inordinate amount of time being able to get comfortable with it, I thought I had not made a wise choice. It was a lot of work, not to mention measuring the car and obtaining and wading through the resource materials necessary to understand the engineering concepts. But looking back, the choice justified itself in two areas. First of all, the work required to learn to use it increased my understanding of nearly anything I did, or felt I had to do to the car (recall I'm a Biologist by training). Secondly, when considering the behavior of the car's handling, the up-front work with the program allowed me to understand and diagnose the problem, and then gave me a huge assist by providing a technology that I could apply to developing, testing and then implementing a solution.

 

Next, the hardware, but doing that post may take a while.

Edited December 28, 2016 by JohnK
changes madated by DropBox, fixing links

[Mondo]

I think WCM has a pretty good record in autocross and at the track. With less than 80 cars out there, it obviously doesn't have the $$$/hours of engineering/stress testing that Caterham has (and you pay for). But there are some very competent S2Ks out there that I would have no problem putting up against others (especially considering the money invested). And their suspension isn't completely different from what's delivered; mainly beefed up in areas that have been found weak).

I like JohnK and think he'll be the first to admit he takes things to the max (just read all the research he does). And given a 2005 Caterham, I'm sure he'd find ways to improve it (probably more in the reliability department ).

With all the main brands, I'm confident someone knowledgeable can set them up (without major engineering changes) close enough that driver's skill will be the deciding factor.

Edited January 22, 2014 by Mondo

[JohnK]

I think WCM has a pretty good record

 

Mondo,

I think I was editing my post #63 while you were responding. My car is very different than most WCMs out there and I think most people with their heads on reasonably straight wouldn't think of going through all the nonsense I have experimenting and all with the goal of learning (but, still, it is such a gas to drive . I'm going through this series of posts as payback to the Se7ens community at large - I spent years and years lurking on Se7ens.net learning about "the car" (i.e. a Se7en-type car) and what I might expect and what facets of such a car I might find most interesting and what people loved and what people hated. If the next generation of Se7ens owners wind up being better informed about the different things they can find in the car by reading what I post, then I'll feel I've done some good.

[MightyMike]

John are you running a watts Linkage? I witnessed a Storker at the Track I work at, the thing was all over the place, yes it was quick in a straight line. You are quite correct Tom about the Caterham compared with some of the other kits.

 

"Storker"? Your snide and conceited remark was out of line and certainly what I would consider a brand comparison. I suggest that you re-read Rule #1 in the guidelines and rules section.

[lancylad]

I have a very good friend who resides in France and has a bda powered caterham, lovely fella and a mine of info which he extends to any one who has a seven type car, no one upmanship in him. He was an active contributing member of two UK based sites.

He left both those forums for exactly what is taking place here. This is a great site, forum, lets keep it that way. We all have the same interests at heart, that is to drive, tinker and drive some more...a certain sensitivity is some times needed when discussing the various makes of sevens. The info on handling has been beneficial to all so far, keep it coming. Blat on people..

[xcarguy]

STORKER!!!!!!!!!! LOL!!!!!!!! So that's what he was talking about. And all this time, I thought there was a new brand out there that I didn't know about.

 

Okay, just kidding. But seriously, guys, there's nothing to prove here. Every Storker . . . ah . . . sorry . . . Stalker owner on this forum (including me) is going to wake up in the morning and still be a Stalker owner. We Stalker owners enjoy our cars for our own reasons. Personally, my Stalker is the most rewarding car I've ever owned, and I owned a Birkin beforehand. My comment is no slam against Birkins; they are fantastic cars. As for my Stalker, I built the car, sold it, bought it back, made it mine again and have had an absolute blast with my second-time-around ownership. I’ve enjoyed tinkering with steering, suspension, aero, playing with tire compounds, corner weighting, etc, etc; the list goes on and on, and that’s what I mean by 'most rewarding car'. And I've certainly enjoyed sharing my experiences with the guys (and gals) on this forum.

 

In saying what I’m about to say, I am in no way defending Terry, but in all fairness to him, he did also mention a certain Birkin that was handling poorly. We all know that there are lots of reasons for a car (ANY CAR) to handle poorly; inadequate tires, improper suspension setup, improper tire inflation, substandard driver (such as me), etc. Throw a ton of power into the equation, and a car that has an improper suspension setup is going to be a monster. Combine that with something like a throttle linkage that acts more like an ON/OFF switch and you further compound the problem. And then add in that driver like me . . . well, we don’t have to actually go there. I once built a Cobra replica that, when finished, over-steered like crazy, had said throttle that was an ON/OFF switch and was scary at best in a corner, but it did run like stink in a straight line. With hindsight being what it is, I wish that I had had the foresight to of gone to someone more knowledgeable than myself and had solicited their help with getting the car setup properly. But I didn’t, and in my ignorance, I sold that car TWO YEARS LATER!!!! thinking it was one of the worst handling cars I ever owned. And it was, not because it was a bad car, but because of me and my lack of understanding about what was going on with the suspension, tires, steering, etc.

 

I know this is a handling thread (and I want it to get back to that and stay just that, a handling thread), but just wanted to put my two cents on the table. Personally, I didn't take any issue with Terry’s statement. I didn't take it as ‘brand bashing’, but more a comment by way of observation. JohnK has gone to great lengths to share his experience in suspension setup in this thread; let’s not take away from that.

 

Gentlemen, we are all on this forum together because we all share a common interest with these cars. Let’s all (this includes ME) be courteous and respectful of each other and appreciative of what each other drives, regardless of brand.

 

And Terry, please, it’s Stalker, dang it, not Storker . . . But that was funny. BTW, happy birthday.

 

Okay, back to the thread.

 

:lurk::lurk::lurk:

Edited January 31, 2014 by xcarguy

[Guest Terry]

Several months ago I was in a bar with several friends of mine enjoying a few cold ones, the conversation got round to talking about bikes; 2 of my friends own Suzuki GSXR 1000’s Sport Bikes and the other owns a Harley. Like some of our members on this forum the guy with the Harley got mega defensive and accusing because the GSX 1000’s guys thought his bike was a Dinosaur. The guy got totally bent out of shape, offended and left. (how sad).

In the end whether or not you own a Birkin, Stalker or Caterham someone’s going to think it’s a piece of garbage, who gives a shit what people think. The moral of the story is don’t get offended about your ride, because when you do you reveal how insecure you are about what you own and how your life is affected by the opinions of others.

My final thoughts on this matter for those who are insecure and defensive about their Lotus 7 /Caterham derivative, is sell it and spend the money on counseling.

 

The End.

Edited January 22, 2014 by Terry

[MightyMike]

Not insecure, not defensive, but do believe your comments are extraordinarily snobbish.

[Guest Terry]

Z3. The bottom line pal is you de railed this post because you reacted to a general statement and took it personally.

[Davemk1]

I'm not a very active member here but I think this place has a lot of value......and I was excited to see a thread with the focus on handling. I have a lot to learn, and some to share and I was looking forward to it.

 

But this thread has been for the most part a waste of bandwidth and if I were a mod I'd close it, delete it and start another handling thread in its place. I would then delete every post that didn't focus on the subject. I fully realize how difficult the job of a mod is and I appreciate the time and effort you put into the forum for all out good.........i would just say that being heavy handed at times can be a good thing.

 

Just my 2 cents.........you can now go back to trying to prove who has the bigger wang.

 

dave

[xcarguy]

. . . . I've spent YEARS trying different combinations in suspension software, fabrication of front and rear anti-roll bars, large amounts of time and money spent on shocks and springs, and hours spent trying to understand what Carroll Smith and Millikin & Millikin were teaching about sports car suspension.

 

My experience is that most folk (including myself, at times) are looking for a 'magic bullet'. A single fix that going to make their car handle wonderfully in one fell swoop. There just ain't no such animal. Enlightenment isn't that easy to achieve, if it actually is ever achieved. The pursuit is not for the timid.

 

Can we get back to meat n' tatters, please? :toetap05:

[slngsht]

I'm not a very active member here but I think this place has a lot of value......and I was excited to see a thread with the focus on handling. I have a lot to learn, and some to share and I was looking forward to it.

 

But this thread has been for the most part a waste of bandwidth and if I were a mod I'd close it, delete it and start another handling thread in its place. I would then delete every post that didn't focus on the subject. I fully realize how difficult the job of a mod is and I appreciate the time and effort you put into the forum for all out good.........i would just say that being heavy handed at times can be a good thing.

 

Just my 2 cents.........you can now go back to trying to prove who has the bigger wang.

 

dave

 

Just checking in... starting at page one to see what it's all about.

[Guest Terry]

I'm pleased to hear that you are excited about this thread.

[slngsht]

guys, I'm inclined to leave the posts as they are. If you've made a post that's not contributing to the thread and want to delete it yourself, do so. As long as it doesn't escalate, I'll let it be. I'm certainly open to a discussion on this, but not here. If you'd like, PM me, or start a thread in the members only section on the topic.

 

calling a stalker a "storker" isn't particularly helpful. at least some of the folks here who don't have a caterham certainly could've chosen to buy one, or even get it built by experienced hands. if there is one thing true about a seven is that it is more tunable than anything else on the road, and it can really be an expression of whatever the owner's desire is. some people just want to drive what they got to the best of their ability - others want to mod and experiment - others want to take a saw to it and try out their fabrication skills. Is it more likely that a showroom stock caterham is better behaved than the car I built and aligned in my garage? probably. Is it impossible that a home built seven can outperform a caterham? No, it's not impossible.

 

This is a great topic with a lot of good posts... keep building on that

[yellowss7]

Hey Mazda, quit posting and get building. You have a few more months to get your car ready. And based on John K's advice in this thread, don't spend time on your suspension set up, Just get that drivetrain done!!!!:smash::smash::smash::seeya:

 

Tom

[Z3 Stalker]

I have deleted my posts for the benefit of this thread

Stewart

[slngsht]

Hey Mazda, quit posting and get building. You have a few more months to get your car ready. And based on John K's advice in this thread, don't spend time on your suspension set up, Just get that drivetrain done!!!!:smash::smash::seeya:

 

Tom

based on my driving skills, I have decided preparing my suspension for high speed offroad excursions is the way to go