NS F355 Project (Page 66/73)
Yarmouth Fiero JAN 26, 03:11 PM
You got me thinking this morning wftb with your statement regarding the mounting location of the inboard end of the tie rod. I was sure I had it settled in my mind that my current arrangement for the tie rod and control arm would generate zero toe change so I went looking for my old drawing. As you can see, with the tie rod and control arm sharing a common point on the ball joint axis and the two pieces fixed together at the inboard end, the assembly is free to rotate together with no net effect on the ball joint / spindle, ie: no toe change. So the fixed end of the tie rod can mount anywhere on the control arm. Thanks for getting my brain in gear.

Bloozberry JAN 26, 04:06 PM
You are correct Yarmouth Fiero... your design does not require the toe link to be mounted to the chassis. If it were mounted to the chassis though, then it would have to be located where wtfb suggested to avoid introducing toe in bump.
Yarmouth Fiero JAN 27, 09:04 AM
Well today is a snow day so perfect for concentrating on capturing the mind numbing yet important data of Body Roll vs Roll Center.

Here are the results of my suspension and stock data supplied by Blooz. Again, I am comparing my '85 style suspension against '88 style so take it with a grain of salt. It does show though my my suspension seems to have a much more stable Roll Center which should be a good thing.

This data is based on a CG of 18" but I think my final CG will be slighlty lower. This should further improve the stability of the car in hard cornering.
Bloozberry JAN 27, 09:40 AM
That's an amazing improvement over the '88! Nice work!
85-308 JAN 27, 09:46 AM
I tried to find a source for the Lotus Suspension Analysis software; a Brit source showed it on sale but (maybe my order was too small?) I couldn't get to the check out page; it just refused. Another that (yeah, yeah, I know...) had it for free - and there are lots of sites showing it for free.. ended up with the inevitable. Spent well over an hour cleaning up my computer from all the trash it installed and even before that, it 'looked like' I had to use the software on a shared server, ... somewhere... no thanks!

So.....
does anyone know where it can be obtained safely? I've sent a note to Lotus but no answer at least yet.
thx
GP
85-308 JAN 27, 10:19 AM
Not trying to sideswipe your thread, Yarmouth; just an update on the Lotus Suspension Software issue. I hope this might help others who get all excited about getting suspension design software like I was.... Maybe it will help someone avoid what I found out.
I DID get a reply from Lotus and they are the ONLY ones who sell it, and yes, as you would suspect from its capabilities and graphics, it is EXPensive... at least for a casual non-commercial user such as most of us would be..
So the seemingly innocuous Brit site I mentioned turned out thusly:
I went thru the process of ordering (this was pre-Lotus reply, mind you) and then on to the payment page.. again, not having ANY idea of what it was really worth.. so suspecting nothing at this time. The software site offered hundreds of various titles and 'looked' ok - yeah, whatever that means!?
Then I checked the payment page web address and while it did have the 's' for secure, it also had switched from 'softwareonlinechoice-dot-something' to 'WINEITUP' dot something.
"Wine it up"? A payment page? So the flags went up and I closed it and started checking it out and yes, it seems it might be a scam site thought to be based in Latvia or somewhere. NOT in Great Britain as I thought...
So, the old story: If it seems to be too good to be true, it probably is. The going rate for the real thing, by the way, is about $3150 per year for Shark alone. So that won't be happening anytime soon...
Back you you, Chet! /End Musical Interlude/ Again, apologies for this sidetrack. LMK if you want it edited or deleted... NP!!
GP

Edit to update actual location..

[This message has been edited by 85-308 (edited 01-27-2015).]

Bloozberry JAN 27, 10:20 AM
And from the previous page:

quote
Originally posted by Yarmouth Fiero:
Well I managed to capture the results of Body Roll vs Camber. The results seem to indicate that while there is camber change during body roll, it seems to be significantly less than the stock suspension. Am I interpreting this data correctly?





You have misinterpreted the data. Your camber gain is much better than the stock '88 Fiero. Take for example the extreme end at 6 degrees body roll where your plot says you have +2 degrees camber on the outside tire. That 2 degrees is measured from the angle of the tire patch to the ground. That means it's much closer to being flat than the '88's tire patch which is 3.75 degrees away from being flat on the ground. Of course the flatter the tire patch, the more traction you have, but there's more that comes into play than that because the tire also flexes.

As I mentioned the other day when we were talking, some of the modern mid engine cars like the Ford GT have an average 0.7:1 camber to roll ratio to account for these other factors. You can sample your data at various points and see where your ratio lands (it varies... and don't forget to take into account your -1 degree static camber!) So for example at 3.5 degrees body roll, your camber gain ratio is [3.5 degrees - (0.58 deg + 1.0 deg static)] / 3.5 deg = 0.55. At 6 degrees body roll it's 0.50:1. That decreasing trend is a characteristic of the Chapman strut design... as the lower control arm approaches perpendicularity with the strut, the camber gain will decrease to zero.
85-308 JAN 27, 10:30 AM
Just to show I CAN stay on topic:

what is the best way now to predict, and control, body roll? Shocks, springs and sway/roll bars? Basically I am wondering IF and WHEN you would get to (ie) 6 degrees of roll; if it might be less or it might be even more? Do you have a goal in mind for maximum roll amount?

What software are you using; is it any kind of suspension design software or are you cranking all this thru Autocad in 3D (wow you are quick if so).
Do you have plans on how the rear setup will affect (the design of) your front end setup; ie assuming it will be a narrower track and somewhat lower due to tire/wheel size, how will you thereby 'link' the two together? Just curious as to what's in the back of your mind on this.

GP
Bloozberry JAN 27, 11:17 AM

quote
Originally posted by 85-308:
The going rate for the real thing, by the way, is about $3150 per year for Shark alone.



The best way is to find a friend who already has access to it and buy him a beer.


quote
Originally posted by 85-308:
what is the best way now to predict, and control, body roll? Shocks, springs and sway/roll bars?



I can try to answer this one. There are several spring rate calculators out there that suggest an appropriate spring rate after having entered a bunch of measurements and going through the interim step of calculating your wheel rate. They usually give end up suggesting a much softer riding car than an enthusiast would like, so take it with a grain of salt. Luckily coil springs can be had in any rate you want in 50 lb/in increments.

Controlling body roll then becomes choosing the correct sway bar (since they only stiffen the chassis in roll) usually through trial and error. It would be nice if there were suppliers who could make any physical configuration and torsional stiffness you'd like, but for the most part we have to settle for what we can make fit, or design the suspension in such a way as to minimize the need for sway bars altogether. Not great choices no matter which way you look at it.
Yarmouth Fiero JAN 27, 11:23 AM
Thanks for all the comments guys. I just got back in from a couple hours of snow blowing so I need to let the feeling come back in my fingers. I have a lot of widows on my street needing to be dug out.

Back with more shortly.