LocostUSA.com

I found my notes, Tibor. I've cherry picked out some of the values most relevant to your front suspension situation. They are all target values, not absolute requirements.

1. Static camber -0.5 to 0 degrees desirable, -1 degree acceptable for hard cornering situations.

2) Camber gain - 0 to -0.5 degrees per inch of suspension travel (not given in roll degrees).

3) Toe-in static, max 1/16" inward at each wheel.

4) Toe-in gain, maximum of 3/4" inward, i.e., 3/8" inward maximum for each wheel on 3" dive. Less is better. Slight toe-out on dive OK.

5) Castor angle, 5 degrees desirable. 1/2 SAI (Steering Axis Inclination) angle max.

6) Scrub radius, -0.5" to -1.5" most desirable range.

7) Roll center front 1"-3". 1" to 1-1/2" seems to work well on Locosts, builders report.

Roll center rear 4"-6"

By the way, my virtual swing arm length is ~154". It worked well for my design, but I'm using '94 Mustang front spindles, not Miata stuff.

I hope this is helpful.

Cheers,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

Thank you Lonnie for trying to help, it is greatly appreciated.

_________________
Tibor


'20 Alfa Romeo Stelvio daily
Locost/442E in progress

With that virtual swing arm length of 154, the roll center moves horizontally? I don't know, if that is OK to move or not.
If it is OK to move, then I could move the RC much lower.
Found these videos about suspension, they seem very good, but it still don't understand everything:
https://www.youtube.com/watch?v=gwtJNS5NlTw
https://www.youtube.com/watch?v=RY7GLr49rc0

MiataV8, I hope you are not upset on me.
I'm just having a hard time believing, that I have nailed my vsusp in one try, without understanding a thing about suspension design.

Thank you all for trying to help.
It is much appreciated.

Tibor

_________________
Tibor


'20 Alfa Romeo Stelvio daily
Locost/442E in progress

A 154" swing arm length may not be right for your components, Tibor. The front roll center is going to move around some with suspension movement in any real world design - side to side and up and down. It's about keeping it from moving too much. You have to experiment with things to find the right combination for your Miata (I'm assuming) front suspension parts.

For example, my upper and lower ball joint centers are likely at different heights off the ground and distances from the vehicle centerline than your Miata parts. I elected to use essentially my 1994 Mustang donor vehicle's front and rear track. It's a tiny bit different, but not much. The live rear axle is also from the same donor Mustang. So, some things were essentially "fixed" for me at the start.

I assume you know the rolling radius of your wheels and tires at front and back. That's the distance from the center of the mounted tire on a suitable width wheel (both rolling radius and suitable wheel widths come from the tire manufacturer). It is possible to alter the track front and rear to some extent by getting wheels of different offsets, and of course by setting the track itself if you don't use the donor track as a starting point. If you don't know what wheel offset is, just Google it and you'll get some nice, illustrated diagrams. You just have to be reasonable about it how much you change offset, however.

So, if you know what the rolling radius of your tires are (the manufacturer will publish the width too if you haven't bought them yet), the offset of the wheels you're using, and consequently the track it all establishes, you have a number of variables essentially fixed. I believe you've set the ride height already at 6.5". On a Locost that tells you where the bottom of the chassis is located.

What I did at first was set the centers of the front suspension brackets from the book: Haynes Roadster in my case; the Champion book for you. It won't be the ideal choice, but it gives a starting point. Your chassis is 4" wider (I think) than the Book, so the geometry will end up slightly different anyway, but it's a start.

You have the dimensions of your front spindles, right? So, that tells you a lot. Set up the locations for your upper and lower ball joint centers relative to your rolling radius (that's where the center of your hub spindle will be) and the chassis centerline and then connect them to the centers of your chassis brackets. See what you get when you fill in the program and run it.

You have to determine which suspension characteristics are within a desirable range and which aren't. Then you start looking for ways to improve the deficient ones while trying to keep the best attributes as stable as you can, improving them if possible. It's a lot of experimentation.

I don't know if Vsup has you enter the centers of your tie rod ball joints on the spindle, but that's important later for determining steering rack location.

It's all a lot of trial and error, Tibor. It's complicated, so expect to do a number of interations. Do try to get the stock Miata layouts for the rear. Do you have any information from the plans you're following as to their locations?

Regards,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

Thanks for all that Lonnie, but I already have every info in vsusp filled in.
Yes I'm using a Miata NA front and NC rear, from which I don't have any info. It is a multi link suspension(5 control arms at one wheel).
Previous Mitas had a 3" RC, so I'm asuming that NC can't be to far off from that number.
I have messed a bit more and I have come up with two variants, what do you think which one would be better for street use?
I understand that all is a compromise, but I'm not sure which compromise should I go with for street use. Less camber gain, or more lean in a curve.
The two version have one difference, 1" shorter LCA.
The first one has very little RC side movement.
The second one has a bit more.
Here are the two variants:
7 Duratec-Final Version/low rc-w/3mm wheel spacer
7 Duratec-Final Version/low rc-w/3mm wheel spacer
If you forgot how to use the roll angle and bump, you just add numbers in the boxes where shows "0".
Thank you in advance.

_________________
Tibor


'20 Alfa Romeo Stelvio daily
Locost/442E in progress

I'm not familiar with Vsup, so I'm feeling my way through it. I may be missing some features it has.

The first one is better than the second. However, I think you have too much camber change on roll even with the first one.

I'm surprised you can't set the static camber yourself. It seems to be totally dependent on the control arm lengths. That is, it calculates the camber as if the upper control arms are fixed, not adjustable.

I changed the ride height to 6" and reduced the tire size somewhat. That had some positive effects, but not enough. Are you able to fiddle with those two variables, or have you bought the tires/wheels already?

I don't see any way to track toe-in/toe-out as a variable you can chart. Besides camber change, you want to make sure the toe-in and/or toe-out are reasonable on dive and bump. You can simulate a 3" dive by putting in 3" bump at both wheels in Vsup. It's the same geometry as when the suspension is in a straight-ahead dive of 3". I'd want to know the toe values then and when you enter -3" bump on each wheel. That gives you behavior when you're chassis is going up in the air, like a jump over a hill.

I think you're going to have to experiment with your chassis-side height locations for the control arms. They are very sensitive to change I found out, so you'll need to go slow and document all the changes you make, so you know what yields an improvement and what doesn't. I think a longer virtual swing arm length would help with the camber changes. Maybe shoot for 120"-130" and see what happens?

Ideally, you'd like the wheels/tires to be as close to vertical as possible at all times. That's impossible to realize in the real world, so you try to minimize changes to camber. Excessive toe-in or toe-out can produce some very negative effects too.

I don't think you're there yet.

Cheers,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

Wheels and tires are already purchased.
With a longer FVSA the camber change should be less, since the radius increases, but what that means for other things?
It will lean much more easily?
Yes, I can't see the toe numbers. I'm wondering how others have dealt with that, who used vsusp.
I'm looking through many build logs, and people are just showing the brackets installed, but they don't talk about how they managed to get to that stage.
Everybody is a suspension engineer?
I know that you have purchased some software, and you are using that.
I should be doing that as well?
I'm starting to think, that I may have to use the McSorley adjustable "box" for the upper control arms.
https://www.youtube.com/watch?v=UsZan0SoSu4
I don't understand why he is saying that the upper control arm should have 10-15 degrees downward, toward the chassis.
That is impossible to achieve.
So, to recap, longer FVSA to achieve less camber change with a 3" bump. What would be an acceptable number?
How about the lean angle at 3 degree?
RC should stay as close as possible to the CL of the car, or if is sliding a bit, it should stay in the same plane.
Vodou drawings show a 9.92" for the upper control arm. That would make the UCA and LCA almost parallel.
Also I'm looking at Youtube videos of Caterham, MK Motorsposrt, GBS cars and they all seem like the upper control arm is almost parallel.

_________________
Tibor


'20 Alfa Romeo Stelvio daily
Locost/442E in progress

Here it is what I have ended up with:
https://tinyurl.com/49nv8fxr
Replaced the 3mm wheel spacer with a 10mm one, now I have .250 scrub radius.
Spindles, wheels and tires has to stay, I already have them.

_________________
Tibor


'20 Alfa Romeo Stelvio daily
Locost/442E in progress

By the time our cars are done, we are - to some degree - suspension engineers. To build a suspension that works well, builders must understand it, otherwise it's blind chance what turns out.


The above in bold is concerning - what is the basis for this statement? I'm bringing this up because if the overall design is basically correct, the upper A-arm does indeed slop downward. We need to get this ironed out so that a safe design comes out the other end.

_________________
Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

I understand that has to slope down, but that much seems impossible. The best that I have got, it was a bit over 6 degrees.
My problem is, that I'm far from being a suspension engineer. I barely understand what is going on.
The issue that I'm having, that no matter what I adjust, not much is changing.
I have even used the Vodou numbers, and it's still not good imho. My wheel/tire combination is causing this issue? Others have used 17" sets.
You guys could give me please some acceptable numbers(maximums), for camber and lean angles?

_________________
Tibor


'20 Alfa Romeo Stelvio daily
Locost/442E in progress

Do you have a serious deadline for completing the front suspension? Meaning, is there a genuine reason way you have to have a solution today, or this week, or in a week? If not, I'd say just take deep breath and realize you have to put some more time into learning about this aspect of the project before arriving at a good solution.

I can answer some of your questions, but I don't have time today. I'll do my best to answer at least some of them tonight.

Cheers,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

It is all good Lonnie, I have time, there is no deadline. I thought that I'm not to far off, and I had a few days off, so I tried to tackle the front suspension. But I have realized, that is not a simple and fast project.
I'll keep messing with the numbers, this way I'll learn something myself as well.
I have what else to do on the car

_________________
Tibor


'20 Alfa Romeo Stelvio daily
Locost/442E in progress

Yes, I bought a 3D suspension design program. It's not cheap, but I've always had a keen interest in suspension design and it gave me a chance to explore there. It does involve a learning curve and establishing (or estimating) many more characteristics of your vehicle, ones Vsup does not ask you for.

Toe-in/Toe-out is primarily a function of your steering rack location and how its tie rods relate geometrically to the control arm(s) inner joints and the location on the uprights on the outer end. Toe-in/Toe-out can be affected by roll and steer too, and the two of those in combination, and anti-dive, but you need a 3D program to figure out the aggregate effects. So, lacking that, you do need to see what Toe-in/Toe-out is for dive and bump with the wheels straight ahead.

The McSorley approach in the video has some good aspects in that it's no-math, flexible and adjustable for camber and castor, but the 2" slider box is excessive and not necessary, in my view. You'll arrive at a better solution using Vsup and experimenting with the inner locations of your control arms. Your outer locations are now essentially fixed by your choice of wheels/tires and the specifics of the Miata uprights you're using. You can still alter the ride height, however, so keep that in mind. That's a "biggie."

Also, the base of the upper arms in McSorely's setup is relatively narrow, so make sure your coilovers can be mounted so that the coilover springs and upper control arm links don't collide.

I've seen mention of the Vodou design, but know nothing about it. Isn't it for a variant of the Haynes Roadster, not the Champion/McSorely variants? Those are different designs at front and back and especially where the lower chassis rails run at front as you can see from this 3D model joining of the two of them (McSorely in red, Haynes in gray). I did it years ago when I was trying to decide which to use.

So, using the control arm brackets locations from one type on the other could lead to real issues.

Increasing the FVSA length may cause the roll center to move more laterally, but not too much. Otherwise, it should only create minor changes in other variables, particularly on a street car where you're not doing extreme maneuvers, assuming you keep it's length within reason like 120-150 inches.

A good target for camber is keeping camber change < 0.5 degrees change per inch of vertical travel. Less is better, of course.

The roll center is going to move around some with any design. In my opinion, if you can keep it withing a circle of 0.5" radius around it's static design location viewed from the front (X & Y movements under typical street suspension changes) then you're doing well. That's just my opinion.

Cheers,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

By the way, I did find my notes from McSorely's documentation regarding the location of the front suspension brackets on the chassis. They were for the 442 and 442E. Here they are:

442:
"The increased width exists through the rear and the cockpit, while the front end is based on the book chassis and it uses a standard nosecone. The suspension brackets can be mounted according to the layout provided by the book, but the length of the front wishbones should be customized to be sure the track width agrees with the donor axle following assembly."

442E
"An increased width/length/height of 4/4/2 inches (respectively) over the original book design throughout the entire chassis, requiring a wider nosecone. . . . the suspension brackets can be mounted according to the layout provided by the book, but the length of the front wishbones should be customized to be sure the track width agrees with the donor axle following assembly."

Do you have access to the original Champion book for those locations? You might want to give them a try using the Miata setup and see what you get.

Cheers,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

Weird, I did not get a notification.
Thank you Lonnie for all that.
Yes, I have both books, original and Gibbs.
I will try with the original books mounting points, and I will let you know.
I have noticed that if I go very wide with the FVSA, I get better results, but that is not good to have that long FVSA, right?
Tried the Voudou(modified Haynes) numbers, just to see how those look. But I haven't looked into the chassis angled tubes angles to compare them with the 442E. Most likely they are different and they wouldn't work correctly.
Some time in frustration, I'm thinking about cutting off the 442E front end, and add the Vodou front end.
When I have started(it's been a year already), I wasn't aware of the alignment issues that I will have with the LCA. The Vodou looks so much easier. Or even going straight/parallel with the tubes of the chassis.
Vsusp has a steering tab, and that can be turned on. It will give the length of the rack, and the mounting height of the rack. But I agree, that it would be much better to view the car from the front.

_________________
Tibor


'20 Alfa Romeo Stelvio daily
Locost/442E in progress