Suspension Spreadsheet - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


Race Prep Miata race-only chat.
Sponsored by:
Sponsored by:

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 04-05-2013, 10:53 AM   #1
Elite Member
Thread Starter
iTrader: (5)
 
Join Date: Dec 2010
Location: Raleigh, NC
Posts: 1,970
Total Cats: 49
Default Suspension Spreadsheet

Hi Everyone,

I have been working on a suspension spreadsheet over the last few weeks. I am mostly doing it as an exercise to help me understand the complex beast that is car suspension. I have got it a point where I think I sharing it to get suggestions is a good idea. Its similar to FCM's sheet, but my intention is go a bit further with the calculations:

-include helper springs
-adjustable sways
-maybe tires
-roll couple as a calculation of CoG, roll axis/center height, and wieght.

Just to iterate, I am trying to learn more, so any suggestions related to suspension are greatly appreciated too. If you guys find any math errors, please let me know and I will fix them.

You can play with it online (Google Docs).

You can download a .ods copy here.

I have included links in the bottom left corner. Most of the links are related to formulas or general suspension discussions. Have a look!
Name:  Screenshotfrom2013-04-05095338_zps8bcacd22.png
Views: 58
Size:  525.6 KB
Seefo is offline   Reply With Quote
Old 04-05-2013, 11:09 AM   #2
I'm Miserable!
iTrader: (1)
 
Join Date: Jan 2008
Posts: 203
Total Cats: 8
Default

Nice! I support this venture.
GAMO is offline   Reply With Quote
Old 04-05-2013, 06:27 PM   #3
Elite Member
Thread Starter
iTrader: (5)
 
Join Date: Dec 2010
Location: Raleigh, NC
Posts: 1,970
Total Cats: 49
Default

I have included my measurements for motion ratios. I came out with:

Front Spring MR: ~.67
Rear Spring MR: ~.75

Front ARB MR: ~.50
Rear ARB MR: ~.56

I measured it a couple of times, trying different locations. I think the most accurate is measuring at rotor face where the studs are (that's what I am going with).

I was thinking about figuring out the coilover angle, but ours seems so insignificant, I am not sure its worth it. The big thing seems to be a difference of angle between the front and rear coilovers (as it creates a bigger gap between the two sets of springs).

Has anyone tried/calculated our roll center or CoG? I imagine its not easy with all the **** in the way.
Seefo is offline   Reply With Quote
Old 04-06-2013, 04:39 AM   #4
Senior Member
iTrader: (1)
 
Join Date: Dec 2010
Location: Farmington Hills, MI
Posts: 878
Total Cats: 93
Default

NA Rear Suspension Geometry in WinGeo - MX-5 Miata Forum

That link has some pictures of a WinGeo file that someone made. It shows that the rear has a roll center of just over 3". I've heard that Miatas have a roll center of 3" in the rear and 2" in the front, and a CoG of around 17". That's just from what I remember reading on forums from a while ago.

Sometime when I have some extra time, I'm going to try to measure all the suspension pick-up points and make a WinGeo model of the front and rear suspensions. I'm really curious to see how it looks.

Spreadsheets are awesome. Mine is about 8 tabs large so far. But, it's for design of a Formula SAE suspension, so it incorporates tire data. I can take my WinGeo model, export data to the spreadsheet, and it will do iterations based on the progressive motion ratios I have designed (all calculations assume fixed motion ratio, which is somewhat worthless with a changing ratio).
acedeuce802 is offline   Reply With Quote
Old 04-06-2013, 03:06 PM   #5
Elite Member
Thread Starter
iTrader: (5)
 
Join Date: Dec 2010
Location: Raleigh, NC
Posts: 1,970
Total Cats: 49
Default

Quote:
Originally Posted by acedeuce802 View Post
NA Rear Suspension Geometry in WinGeo - MX-5 Miata Forum

That link has some pictures of a WinGeo file that someone made. It shows that the rear has a roll center of just over 3". I've heard that Miatas have a roll center of 3" in the rear and 2" in the front, and a CoG of around 17". That's just from what I remember reading on forums from a while ago.

Sometime when I have some extra time, I'm going to try to measure all the suspension pick-up points and make a WinGeo model of the front and rear suspensions. I'm really curious to see how it looks.

Spreadsheets are awesome. Mine is about 8 tabs large so far. But, it's for design of a Formula SAE suspension, so it incorporates tire data. I can take my WinGeo model, export data to the spreadsheet, and it will do iterations based on the progressive motion ratios I have designed (all calculations assume fixed motion ratio, which is somewhat worthless with a changing ratio).
Very nice, I figured the locost forums would have some good info on this. Mind sharing your suspension spreadsheet?

What has me really baffled so far is that balance seems "irrelevant" of weight distribution up to this point. I am really wondering when that starts to affect things and the calculations done at that point. I was thinking it would show up with weight transfer, but from my reading it seems weight transfer is almost always calculated at the CoG using total weight and distributing it based on roll stiffness.
Seefo is offline   Reply With Quote
Old 04-14-2013, 09:58 AM   #6
Elite Member
Thread Starter
iTrader: (5)
 
Join Date: Dec 2010
Location: Raleigh, NC
Posts: 1,970
Total Cats: 49
Default

I plugged the miata suspension geometry in this nifty little webapp.

The rear suspension is pretty close I think. I have scoured the internet for data on the suspension mount points and subframe. Majority of data came from the locost forums and a post on enderw88. I grabbed the roll center from a government safety test.

Stock Roll Centers:
Front: 2.17in
Rear: 3.5in
CoG: 17.7 in

VSusp is 2d only, so there is definitely a limitation on accuracy here. Plus the front UCA is really hard to figure out since its angled and not parallel. I am not sure how accurate the front is over all, but I think its pretty close.

You can adjust the ride height for your car (measured at the subframe, its .25" lower than the pinch weld).
Seefo is offline   Reply With Quote
Old 04-19-2013, 02:14 PM   #7
Senior Member
iTrader: (1)
 
Join Date: Dec 2010
Location: Farmington Hills, MI
Posts: 878
Total Cats: 93
Default

Quote:
Originally Posted by Track View Post
Very nice, I figured the locost forums would have some good info on this. Mind sharing your suspension spreadsheet?

What has me really baffled so far is that balance seems "irrelevant" of weight distribution up to this point. I am really wondering when that starts to affect things and the calculations done at that point. I was thinking it would show up with weight transfer, but from my reading it seems weight transfer is almost always calculated at the CoG using total weight and distributing it based on roll stiffness.
I will add my spreadsheet later, it's super messy right now (I make VERY messy spreadsheets at first), and in the next few days I'm reorganizing it so someone other than myself may have a clue of what's going on.

Weight distribution becomes very important when you start talking about yaw moments. The vehicle rotates about it's center of gravity. Think about how the Deltawing corners. It's front tires are only 4 inches wide, and yet it doesn't understeer at all. The CG is very rearward, making the distance from the front tires to the CG much longer than the rear. The lateral force generated at the tires is putting a moment about the CG, and since the front wheels are so much farther away from the CG than the rear, they affect the yaw more.
acedeuce802 is offline   Reply With Quote
Old 09-05-2013, 07:57 PM   #8
Newb
 
Join Date: Sep 2013
Posts: 2
Total Cats: 0
Default

Quote:
Originally Posted by Track View Post
I plugged the miata suspension geometry in this nifty little webapp.
Neato! That's what I want to do too! Unfortunately that link just took me to vsusp.com's default suspension settings. Where can I find data on Miata front and rear suspension chassis bracket positions, ball joint locations (front) and bushing locations (rear) on the spindles (relative to wheel location), and control arm lengths? I'm newer than new here and I don't even have a turbo on my Miata yet (though I have one on my Locost) but this info will be much appreciated.
JackMcCornack is offline   Reply With Quote
Old 09-05-2013, 08:14 PM   #9
Elite Member
Thread Starter
iTrader: (5)
 
Join Date: Dec 2010
Location: Raleigh, NC
Posts: 1,970
Total Cats: 49
Default

Quote:
Originally Posted by JackMcCornack View Post
Neato! That's what I want to do too! Unfortunately that link just took me to vsusp.com's default suspension settings. Where can I find data on Miata front and rear suspension chassis bracket positions, ball joint locations (front) and bushing locations (rear) on the spindles (relative to wheel location), and control arm lengths? I'm newer than new here and I don't even have a turbo on my Miata yet (though I have one on my Locost) but this info will be much appreciated.
I suspect your browser is acting up in that case...

I would use firefox or chrome to do it. If all else fails, copy the link address and paste it directly into your link bar.

You can find most of my sources in the spreadsheet on my google drive. (first post).

I found all the data on the internet and verified some of it on my car. I didn't try too much, nor did I change it if my measurement deviated, so you can probably retrace my steps.

If I found multiple values of the same measurement, I tried both and used what seemed reasonable (based one expected RC).

I have the rest of the site saved, but I am not near my laptop at this time.
Seefo is offline   Reply With Quote
Old 09-07-2013, 01:34 AM   #10
Newb
 
Join Date: Sep 2013
Posts: 2
Total Cats: 0
Default

Track, I want to thank you for your remarkably prompt response. Man, I'm such a luddite, but I'll work with the info you linked before I bother you again for more details.

You'd think that accurate measurements of Miata suspension geometry would be easy to come by...maybe if I was a spec racer or sumpin' I'd know just who to ask. Sigh.
JackMcCornack is offline   Reply With Quote
Old 09-11-2013, 11:05 AM   #11
Elite Member
Thread Starter
iTrader: (5)
 
Join Date: Dec 2010
Location: Raleigh, NC
Posts: 1,970
Total Cats: 49
Default

Seefo is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Project Gemini - Turbo Civic on the Cheap Full_Tilt_Boogie Build Threads 59 12-15-2017 09:00 PM
1994 Spec Miata Race Car SM/SM2/SSM For Sale Quinn Cars for sale/trade 6 10-23-2016 08:58 AM
Hey everyone another n00b here Big_gumby Meet and Greet 80 10-05-2015 05:06 PM
3rd Time's a Charm...hopefully. zephyrusaurai Meet and Greet 2 09-28-2015 11:59 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 07:20 AM.