Suspension design for Locost with Vsusp

[carguy123]

I'd love to be able to work backwards. Tell it what wheels, diameter tires, offset, upright, track and then give it some parameters that I want in RC, camber gain, etc. and have it tell me what it would take to get there.

[horizenjob]

Lotus19

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.

There might be a couple of things going on here. Pretty sure I may land up using the word tradeoffs...

If your links are parallel or nearly so that gives you a roll center close to ground.

The Miata has uprights with a high lower wishbone. It's very similar to a Pinto upright when I superimpose them in my model. I considered building a spacer to fit under the upright and move the wishbone down, but that's hard because the boss that mounts the lower ball joint is at a considerable angle so the geometry changes a lot.

So having to mount the upright a couple of inches higher then needed also moves your roll center up a couple of inches for a lot of the geometries you are probably trying. That's a reason I spent more time looking at the Pinto parts because they come in drop versions, which don't drop the car if you're building from scratch - but they do drop the lower control arm. If you are using modern size wheels you can use normal Pinto uprights and add spacers below for wishbones with spherical bearings. You can do the same thing with the traditional Triumph style uprights which may be what was on the original Lotus 19, they are very nice units.

Don't be afraid to angle your lower arm some and perhaps settle for a little less camber correction in bump.

The nice thing about Rob's program is that you can share your setup with us more easily then a string computer and you can have different windows open so you can keep track of your changes and go back easily and review what you are doing. That can be a big help, with the string computer you need to write everything down and draw your own graphs...

This is in fact a good amount of work to do, no matter how you do it. Keep at it!

[Lotus19]

Thanks for the encouragement/info Rob and Horizen. I thought about using Triumph uprights, as that's what originally came on the car, but figured Miata parts were abundant, cheap and a lot of other builders have used them with great success. I already have the Miata stuff, plus all of the Kinetic stuff, so I'll make it work...

As anyone plugged in all of the dimensions of a stock, 1st gen Miata into Vsusp? Would be interesting to see it in the simulator...

[Mhm]

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.

I also think that it would be a very usefull feature to lock the wheels in position.
I've been playing around with vsup and myself constantly adjusting arm lengths on keep the track constant inner pivot points are being moved around.

[Lotus19]

So I've been playing around with the simulator:

http://vsusp.com/?tool=2d#0.7%26project ... enter.y%7D

What are the target parameters to shoot for when using the simulator and am I even close?

[horizenjob]

Lotus19, should I just look at the front or are you asking about both ends? The front looks fine. You have reasonable camber correction, sometimes people try to get too much. The rear looks like you're still working on it? You probably want the rear roll center higher then the front, pr the car will not be happy to turn in...

[Lotus19]

Oops, I should have made that clear: front only. (Haven't even touched the rear yet).

I only ask, because it seemed almost too painless! Wheels seem to stay upright in bump, but I just wanted to make sure I wasn't missing something. Thanks!

[Rob7]

Ack, late reply, sorry about that -- OK, it sounds like a 'lock wheels' feature would be good to work on next. I'll work on that after I fix a couple small bugs. At this point it does seem that it will take a little while to implement that feature, but I'll see how it goes. Thanks for the feedback, guys --

[Rob7]

As anyone plugged in all of the dimensions of a stock, 1st gen Miata into Vsusp? Would be interesting to see it in the simulator...

Hi Lotus19 - I wanted to reply sooner, but I'm curious if you've seen this thread from http://www.miataturbo.net. Looks like someone put in both the front and rear susp measurements. Tire size is not the stock, but the tire diameter only increased 1/4" with the lower profile tires.

Project link is:
Miata geometry - 185/55r15

Here's a link with the oem-size tires in case it's helpful:
Miata - 185/60r14

[Lotus19]

Hey Rob! Thanks for the stock Miata simulator info--I'm sure it will be helpful for all of us using Miata uprights, trying to come close to the factory geometry. It's nice to be able to compare my numbers with those of the engineers at Mazda! Also a big thanks on working on the "wheel lock" feature. I think it will really make Vsusp that much more easier to use. Good luck!

Joe

[Rob7]

No probs, Lotus19

I just added a VSusp update to get some older issues out of the way. Next I'm going to look at doing the 'lock wheels' feature. I'm hoping it won't take too too long to implement

[Lotus19]

Okay, so I've got two designs that seem to look pretty good to me. The first has longer a-arms, which everyone says is a good thing. Of the two designs, is one clearly "better" than the other (i.e. more predictable handling), or are they so similar that an average Joe like myself wouldn't really notice?

Any tips/advice/comments appreciated. Thanks!

http://vsusp.com/?tool=2d#0.7%26project ... enter.y%7D

http://vsusp.com/?tool=2d#0.7%26project ... enter.y%7D