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The Champion numbers don't work, because he was using different spindles, much narrower chassis and smaller wheels.
My tire/wheel setup is:
- front 215/50/R17 wheels ET 40 and 8" wide, ext. diameter is 25.46"
- rear 245/45/R17 wheels ET 40 and 8" wide, ext. diameter is 24.97"
Tried it many many times, and at the moment, this is where I'm at:
7 Duratec-w/10mm wheel spacer
Question, when I add an 1" lean(roll angle) to the left, camber is OK to go into + territory? No matter what I do, I get around 0.68-0.7 left camber. If I set -0.5 degree camber, when I add 1 degree, goes to around 0.276. That is normal?
Also everybody says that a 0.25 scrub radius is OK. I have read somewhere that Miata has a 0 scrub radius. Should i use the Miata's 0, or go with what everybody says? Right now my vsusp is done with a 0.25 scrub.

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Tibor


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

You do not want a "0" scrub radius. That gives you dead input type of steering feel. A .5" to .75" scrub radius typically give the best steering input. To get more camber gain in roll, increase the angle on the upper control arm. Shoot for camber gain around .8 degrees per degree of roll.

It makes sense, but I'm wondering why Mazda designed it with 0 scrub radius?
If I add 1" bump, I get 0.442 camber angle.
If I add 1 degree roll angle, I get 0.796 degree.
I calculate it correctly? How these numbers look to you?
Thanks for trying to help.

Tibor

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Tibor


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

It's somewhat irrelevant. The 7 is so much lighter that 'normal' numbers don't always work out the same. With 5.5 degrees of caster and roughly one inch of scrub my steering was numb, wouldn't self-center and tended to wander instead of wanting to go straight. At 10 degrees of caster it self-centers, tracks a straight line nicely, communication is much improved and steering effort is still reasonable. You couldn't get away with that much combined caster and scrub in a manual steering car if it weighed 3000lbs, the steering would be too heavy.

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Peace, Ron

OK, I went back to an early one and worked it a bit as per Miatav8 suggestion to have the yellow and blue lines in the graph to run parallel.
I had to extend the LCA mounting points, and reduce a bit the UCA mounting points to get to this point.
I will have to add some extra tubes, to be able to attach the brackets.
What do you guys think about it, to me(who doesn't know almost nothing about this things) it looks very good.


7 Duratec-Looks good?-w/3mm wheel spacer

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Tibor


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

The zero scrub is for FWD systems, to reduce kick-back [torque steer] when applying power.

I have added a 3mm spacer to have 0.25" scrub.
I have added 10 more millimeters, now the scrub is 0.377".
Should I add even more?
In the beginning I had something just over 1" and I was told to reduce it much lower.

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Tibor


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

The .37" scrub should be good. The car should have a lighter steering feel. I'm sure some drivers would prefer that, Vs a heavier feel.

That amount of scrub is fine. As Dave said, you'll have lighter steering. My opinion is 1" or less with typical sized street tires and you'll be fine.

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Peace, Ron

So, here it is the .377 scrub radius vsusp, what do you guys think about it? Can I build it with these numbers?

7 Duratec-Looks good?-w/3mm wheel spacer

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Tibor


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

Your looking for .100 or less per inch of travel. An try to get it toeout in bump.

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American 7 5.0 T5
Lotus 15 ish?
914/H6

I work on this for hours every day, and I can't get it under .500. I have no idea on what I'm doing, that is the problem. I'm just changing numbers and hope that it gets better.
But I don't know how it should look a good one.
Some people are saying that the default vsusp is very good. If I gave it 3" bump, it goes over -5 degree camber. To me that does not look good at all.
Scrub is 3", that seems to big as well.
FSVA is 49, which to me it seems very short, no?
Sorry, but I don't understand what do you mean about toe out bump. Can you see that in vsusp?
Could you please look at the attached picture?
That is what you are saying?
Also what should I see at the roll center if I add 1 degree, how the camber should look like?
I'm using 0.5 camber.

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Tibor


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

Tibor,

I'm looking at this Vsup model ==> 7 Duratec-Looks good?-w/3mm wheel spacer in the posting Wednesday, September 13th above. I'm not seeing what you describe. It has FVSA on both sides as 129.383 inches.

Also, what chassis front end are you modeling? Is it McSorely or the Vodou chassis front end? You are using the base 442E chassis as your starting point, right?

I see you steering tie rods now (maroon). Have you found out how to determine changes in toe-in/toe-out now?

Cheers,

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

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

I'm using the 442E chassis.
I'm planning to use the Vodou(modified Haynes modified for Miata NA spindles) control arms.
I don't think that is possible to see toe. There is a tab "Steering" where is shows the length of the rack height/length and where the outer tie rod should be located.
At least I'm not aware how to see toe.

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Tibor


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

We're really mixing apples and oranges here, Tibor. You're using the 442E chassis with the Champion (Book) layout for the front suspension arms, but the control arms are coming from the VoDou version of the Haynes Roadster design. You could use the VoDou arm design, but I'm pretty sure the arm lengths would need to be different for your specific (hybrid) component mixture.

I downloaded a PDF copy of the VoDou design and looked at the front bracket locations it provides and took them from the drawing there which is just below.


Taking your Vsup model, and assuming your placement and figures for the front track, upright ball joint locations, steering tie rod ball joint, etc, etc., are per VoDou design as well, I wanted to see what one would get from the original VouDou design. I converted the VoDou metric measurements to inches, which is the green text in the graphic below. I don't know if Vsup can use millimeters or not.


You may want to fiddle around with the above numbers and see if the original design was any good in the first place. I have no reason to suspect it's not good, but it would pay to verify it.

I don't know why Vsup cares about the distance between the mounts and the inclination angle. It may just be for verification purposes for the builder? I don't know, but I've never had to use those figures for anything. I think those numbers may have confused you.

If I may make a suggestion here, I'd verify that the standard Champion bracket locations can be fitted to the 442E chassis. You actually have the 442E built, right? See if the 442E front frame will actually support their original locations, and do the same for the front rear brackets. If so, enter those in Vsup. If not, you'll have to figure out a new, practical location using the original locations as a guide, but placing them out further from the centerline, up from the bottom, etc., etc.

Then verify that you have the track and upper/lower balljoint centers, steering tie rod balljoint centers numbers entered correctly for the Miata NA versions. What was your source for those numbers? You can make the track whatever you want in theory, but I'm assuming the VoDou numbers are based on being compatible with the rear Miata IRS layout.

Just remember, there is a solution available. Figuring is out is our job as constructors of one-off versions of the Locost, which yours will be.

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

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