Suspension design for Locost with Vsusp

[Brust]

Except that all those factors are accounted for in the program. It's six one half dozen the other.

[Posthumane]

Oh, no disagreement there Brust, for the program it doesn't really matter since, as you say, it takes it all into account. I was just musing in a more general sense that track is defined that way to remove the effect of wheel width. Carry on.

[Brust]

Roger that- I hope that didn't come across too snotty. I was panicking at around 1030 last night so had to go back out and measure to confirm the correct width. Luckily, my first measurement was good, and I'm all set to go!

[phongshader]

Hopefully some one can tell me why there is a difference of opinion of what the measurements and angles between vsusp and Solidworks. Such as the linear distance between the ball joints, angle of the arms in relation to the chassis, and so on. Probably user error...
Thanks

susp.jpg

miata/LS1/442E

[phongshader]

yes it's user error, got it working now
miata/LS1/442E

[horizenjob]

That's nice to have a check though... Thanks!

[phongshader]

I've been playing around with VSUSP trying to figure out what I want...what do I want? From what I can gather keeping the RC stationary as possible and somewhere between 0 and 3" above ground is fairly important then keeping the tires perpendicular to the road surface, camber curves. Does that sound right? With that in mind would some one with more experience take a look and possibly throw some pearls of wisdom my way?
http://tinyurl.com/miata-LS-442E
Thanks

[autoxinvr6]

http://tinyurl.com/nd24s37

My VSUSP plan

The rear upper and lower from pivots should be adjustable vertically 1.25 inches in either direction . Working on a plan for the fronts to be adjustable in the same way...

The rear upright is a MacPherson and the rear upper pivot is using the top hole of where the strut would mount so that pivot can really be placed anywhere provided it is at least an inch further inboard if you keep it the same vertical height....

Thoughts?

[Yohan]

Hi Guys,

could you please comment my suspension design:

default values

[horizenjob]

I took a quick look at the Vsusp results pointed to in the last three posts. Sorry we don't get much discussion in this thread. I should have taken notes, so I will try to get back to it this weekend.

Yohan, looks good to me. It's interesting that if I remember right you used to tilt the rear lower arms down towards chassis, but now you have settled on doing this with the front. You are towards having a lot of static camber but of coarse you can change that once you drive the car or wear out some tires or just land up being happy with it. Let us know!

Yohan has more tilt of the roll axis from front to back, about 2". This will help the car turn in and reduce understeer.

Autoxinvr6 and Phongshader also have reasonable setups with reasonable camber correction, guidelines I have seen recommended no more then 1/2 degree per degree of roll. I have to check again but one of those setups at one end of the car seemed above that. Both of these setups have less tilt on the roll axis and if the car pushes too much that will be something to look at. That's all I had time for to check so far. I didn't get to look at swing arm lengths or other issues yet.

Thanks for putting up some numbers. It will be great to be able to look at these things when you have these cars running. It's a good contribution to the site.

[Lotus19]

Hey guys, is there a way to set a track width on the Vsusp, and "lock" it in place? I've ben playing around with the simulator, but anytime I increase tire size, offset, etc., the track width changes. Since I am using the Lotus 19 body, my track width is pretty much set. I'm using Miata uprights and my front hub face-to-hub face distance is 49". My wheels have a 30mm offset, so 49"-(1.181x2)=a track width of 46.638". How can I save this number in the simulator?

BTW, How are all you builders, using Miata uprights, getting such low R/C's? I built a Staniforth string computer, but I am getting crazy numbers. I'm pretty sure I built it correctly.

For example, with 205/60 15 tires, 30mm offset wheels, Miata hubs and a LCA pretty much parallel to the ground, I'm getting a R/C of about 4.75" off the ground! In order to get a more reasonable R/C of 2.5", I have to angle the LCA down towards the frame at around 6*, which is not good. I know my tires are a bit taller than stock, but my track width is almost 9" narrower than a stock Miata (which should make my R/C lower than the factory 2.4" measurement).

I wanted to use old-school technology and figure out my pick up points with the string computer, but it looks like I'm going to have to rely on one of these newfangled computers!

Any help would be appreciated!

Joe

[Rob7]

Hi Joe -
In vsusp, the track width is currently output-only. So if you change the wheel offset, the track width must change unless you also change something like control arm length. If vsusp did have a feature to lock the track width, which part of the suspension would you prefer change when you adjust wheel offset?

-Rob

[Lotus19]

Hey Rob, I was hoping that the a-arm lengths would automatically change with manipulation of the inner pick-up points. In my case, track width, offset, tire size, and upright settings are all fixed. If these values remained constant, along with a way to keep the tire "locked" vertically during initial set-up, then all one would need to do is play around with the inner pick-ups (as the control arm length would automatically change). Then, once pick-ups were chosen, the tire could be "unlocked" and the user could drag the icon around to see the effects of bump/roll with the chosen settings. Kinda confusing, but hopefully this makes sense. Thanks

Joe

[KB58]

I haven't used Vsusp but have seen an issue which affects other sw packages:

If you adjust caster, the sw doesn't rotate the virtual upright as expected; all it does it move the upper pickup point alone. What "should" happen is that the entire upright (and its pivot points) is rotated as an assembly, raising the steering pivot (assuming front-steer.) If the software isn't rotating the entire upright, it results in a physical implementation that differs from the sw and results in unexpected bump-steer.

[Rob7]

Lotus19: I can see how that would be useful, I thought about that feature a while back but never got around to it because it would likely take a while to implement. No one had asked for it, so I thought it might be too much trouble for a 2D tool. Curious how many other builders would find it helpful to be able to 'lock' the wheels in place and adjust other parts of the suspension?

KB58: Makes sense, vsusp doesn't even bother with caster. A proper 3D tool would solve this and a lot of other problems. I had started converting the Wishbone code to javascript a while back but then got sidetracked. I'll take another look at it today, hmmm