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I suppose this is not strictly Data Acquisition, but it is Analysis of Suspension and I can not see a better forum to put this question in. Scott Fairchild has put up a few videos on measuring and analyzing suspensions to determine roll centers. The software that he uses appears to be very good, but I don't know what it is, what it costs, or what alternatives there might be. Any suggestions, comments or user experience would be greatly appreciated. Thanks
Do yourself a favour, just get a big piece of paper. I've downloaded the software package that Scott used, but I'm not sure I'm prepared to spend some time in learning how to use it.
This is Allan Staniforth's string computer:
http://www.vettemod.com/forum/imageh...b3882825cd.jpg
make mods see where the RC moves near real time. Online analysis available at: https://www.racingaspirations.com/
Huih has made a lot of upgrades on his program over the last few years. Standard disclaimer.
Cheers - Jim
I do a lot of suspension analysis. That is more the case these days with my cars using so many different tire sizes especially at the front.
I do have analysis software but way more important for me is using a drafting program like AutoCad or DraftSight to do the analysis. 2D drawings are the place to start but I prefer to use 3D , wire frame type drawings. With SolidWorks, I can draw the suspension and then animate the drawing to give me the data I need, such as roll center locations and movements, and motion ratios (shock/springs to wheels). Being able to do the analysis in three dimensions really improves the results. This is especially true for bell crank systems. Knowing what the motion ratios of the springs to the wheels and how that changes as the wheel moves is critical to understand the handling of a car. I use my drawings to give me the input data for Mitchell software.
One of the many benefits of belonging to the EAA (Experimental Aircraft Association) is that you can get a student version of SolidWorks, free, as a member. With SolidWorks you can model you entire suspension and animate the movements as it would be on the race track. There is a steep learning curve here but SolidWorks has great tutorials to help that along.
Thanks for the suggestion. Long ago, I started to do just that but after I had located the roll centers, I didn't really know what to do with the information. The interesting thing to me was the movement of the front and rear instant roll centers and Scott's effort to bring them both closer to the car center line and to the same side. Apparently he could used his software to simulate that at a roll angle of 3 degrees.
It seems like it would be a lot easier to do this kind of front to back analysis on a computer than with two big pieces of paper. But you might well be right; it would depend on how challenging the software is. Scott's pictures on his monitor seemed very useful, what package did you get that he was using. How pricey is it?
Thanks!
Quote:
Originally Posted by Hawke
Both the "string method" and Racing Aspirations models keep the roll center at the center of the car. Is this not incorrect? Does not the instantaneous roll center move both up/down and left/right? Curious.
john f
Try rolling the chassis and then check:thumbsup:
Quote:
Originally Posted by scott fairchild
Scott, I assume that you mean to "roll" as in to lean the chassis right or left as if it was in a turn. I couldn't figure out quite how to roll a string model forward and back!
I did want to ask what software you used in your video analysis. Did you look at other packages? S Lathrop is obviously way ahead on this but I need something simpler, less capable, and easier to learn.
Thanks
I use SusProg3d and will be writing on it in my blog and the Facebook Vintage FF page very soon.
I like it because it give a graphical and data version of the suspension in roll, bump and droop. The data shows Roll center height and offset at various degrees of roll and ride height too.
Here is a screen shot of my Crossle 32https://www.apexspeed.com/forums/att...id=89037&stc=1
I like SUSPROG too - but haven't just yet justified the price. They may still have a free trial period - but it is somewhat limited in its scope during trial.
I found a handy tool a number of years back and just relocated it on my HDD.
I couldn't load as a zip, so changed to a pdf extension. It will not open as a pdf.
This is a zip file not a pdf. It is an Excel spreadsheet.
It is a simple suspension analysis program built by a kiwi.
Lets you make changes - check the RC/IC movement.
His blog has gone dark and I have no email address for him, but this works pretty well.
{But it is a bit of effort to download.}
You'll need Excel and a zip/unzip tool
Use these steps:
- RIGHT CLICK Choose Open Link in Another Tab.
- CHOOSE Save File
- CLICK OK to download it.
- Go DOWNLOAD ARROW - upper right corner and LEFT CLICK on the ARROW
- HOVER OVER the Name and RIGHT CLICK
- Choose Open Containing Folder
- RIGHT CLICK choose to Rename
- CHANGE the "pdf" to "ZIP"
- Click YES
- UNZIP - your choice of tools
- Then OPEN in Excel.
- SAVE - if you like and want to keep
Sorry for the pain but it's free. Send George a beer if you like it. I tried t make the actions required as clear as possible. Hope it works for you. I've tested it several times and seems clear...All measurements are metric except the tires. It is a bit limited on the range of tire sizes, but useful none the less.
Cheers - Jim
Jim,Quote:
Originally Posted by phantomjock
Will the Susprog do rocker style? I'm looking at purchasing.
Thanks,
Scott
Scott,
I will look tonight if it does rocker style arms.
Remember though in analysis a rocker arm is the same as a tube attached at that point and your spring assembly is another arm.
Geometry doesn't care how wide an arm is on a triangle if you know what I mean!
Rob
Scott,
Just looked at the suspension types on SusProg3d. While it does not specifically call for rocker arms, it does allow them if you look at them as a variation of an A-arm. So graphically it won't show them connected but instead represent them as the 2 sides of the arm.
As far as setting up your springs/shocks in the program, first you don't have to in order to get most values like roll center and secondly you can set up you spring/shock as a bellcrank/push where the pushrod arm has a zero length and the bellcrank sides are dimensioned same as your rocker arm. I can help you figure it out.
Rob
And when you get your suspension measured, and wish to spend the rest of your life engrossed in data, put it into ChasisSim. It takes all those measurements plus some you didn't know even existed, and even your track with its bumps etc.
ChassisSim [and many other suspension analysis programs too] can eat all your "spare time" for sure!Quote:
Originally Posted by Hawke
There is another interesting program out there - CASIM. I found it when I began designing a dual wishbone IRS for my '78 Corvette. I spent quite a bit of my off time when deployed to work the design, and it felt like I was getting a PhD!
CASIM takes your input suspension points (again all metric based inputs/outputs) and then migrates them (within a range you set) during a simulation. Then you choose the locations for your desired result.
That info can then be put into other programs, like SUSPROG/ChassisSim/etc and validate/verify the results if you like. It can take quite a bit of time to run if you select high precision, but save you a ton of guessing which way to move a mounting point.
Maybe the attached screen shots will better explain what I'm saying. This is the setup tab :
https://www.apexspeed.com/forums/att...id=89044&stc=1
You can animate in the second tab. In this Tab (Tab 3) you setup the simulation.
https://www.apexspeed.com/forums/att...id=89046&stc=1
If interested I can send it to you rather than go through the Zip-masking I did earlier with the BonesApart excel file..
Drop me a PM or direct at chainplates AT hotmail DOT com
Cheers - Jim
I was not clear in my previous post concerning roll center. When you roll the vehicle the first amount the roll center is at some Y dimension and X is zero. All the programs I have seen, including the "string method" or "racing aspirations" continue to roll the vehicle around the same roll center. Should you not roll the vehicle around the new roll center which will have moved in both the X and Y directions? It is called the "instantaneous roll center" meaning that if the point moves, the vehicle will then roll around that, no? This is what I was taught in vehicle dynamics back in school in 1973, but as far as I can tell, not done today. Can someone explain this for an old fart? Thanks.
john f
Is the CASIM program 3 or 2d?
2d
For free that is all I'd expect.... as is Racing Aspirations and Bones Apart.
Jim
Hi Everyone,
for those interested in Suspension Analysis Tools have a look at www.dynatune-xl.com
You can find all kind of MS Excel based tools and in particular our Suspension Design Module which will allow you to create your ownSuspension in a professional manner. It might a bit more complex than a huge piece of white paper, but it does also provide a bit more information.
Thanks
Dynatune
As we are in COVID lockdown here, its given me some time to analyse my rear suspension, and go back to my roots as a pretty ordinary mechanical draughtsman.
I drew up the rear suspension, (note to self - don't do it again at 1:1 scale on an A0 drawing board) and followed Scott Fairchild's recent videos.
What I "discovered" was that my roll center only moved up 10mm in 3 degrees of roll. It did not move left or right. Can this be correct. It is possible, as my drawing has about a million different lines on it, and I could have cocked something up.
Any comments?
You want the roll center (crossing thru the centerline of the car) to be in the same position relative to the chassis thru its range of motion and the virtual swing arm to be 1.5 minimum of track width (preferably greater) at ride height. So 2" of bump lowers the RC 2". I use a simple program called Wishbone that I down loaded from LocostUSA.com. Unfortunately that website has been down for a few days.
I have used a program called WinGeo 4.08 for decades. I do a 3D AutoCad drawing of the suspension geometry and I use the drawing for the input values for WinGeo. The program was written by Bill Mitchell who passed away many years ago. I believe that David Ferguson was planning to offer the Mitchell analysis program through Veracity Racing Data. I do not know if he every was able to do that, though.
For my own work, I start with AutoCad 3D drawing of the suspension system to get the roll centers and swing arm lengths that I want. I use the Mitchell program to refine the details of my bell crank systems so I can get an exact plot of the motion ratios of the springs and shocks as the suspension moves. With the Mitchell program I can change the ride height in any increment I choose and get the motion ratio at the point of the suspension movement. I do use the Mitchell system to help refine the roll center movements, especially laterally, but the bell cranks seem to be an ongoing development process. I am to the point where I am changing bell crank designs to match the shock valving to the suspension movements. The Mitchell program in critical to that process.
I tried very hard to work with the person that Bill Mitchell left the software rights to, but was never able to get access / permission to distribute / maintain that code. For years we kept a list of interested people, but I have finally admitted defeat in this endeavor.
Thanks for the update.Quote:
Originally Posted by David Ferguson
It is a shame that the person who has control of the produce has not maintained and marketed the product. Bill's memory deserves a lot better.
Still in lockdown here, so it gives me an opportunity to look at this stuff in more detail. When I did my final engineering exams, we had to use a sliderule and show workings. Not long after that, I bought a HP25 calculator, which was $273 or about 4 weeks wages. So its been a long time since I've done workings like this.
I ended up using Georges (BonesApart) spreadsheet to work out roll centres. It works pretty well, and illustrated to me how much things can change by moving ride heights. By jiggling ride heights and putting some spacers on the upper front uprights, I got my rear roll centre to 49mm, front 42. With a horizontal shift of 23mm (rear) and 59mm (front) in 3 degrees of roll, and both under 1mm vertical shift in 3 degrees of roll.
My RaceChrono data, has told me that I can get 1.3g when cornering. So with 385 lbs rear load, this suggests a 500lb lateral force. Some data I found suggested that a FF has a rear CoG of 300mm. So based upon the drawings I had done, this is putting a 371 lb force onto the 400 lb spring, so it would deflect it 0.930" or 23.6mm.
If I redraw this, this suggests my maximum roll is exactly 3 degrees. However, I have ignored any resistance from anti roll bars. Or dont you think it really matters?
Your comments would be welcomed.
I have a new(er) laptop computer, but am unable to load Mitchell WinGeo 4.01 onto it. Keep getting an error that states "This App cannot run on your PC. To find a version for your PC, check with the software publisher". I have tried running it in various compatibility modes....Win95, Win98, XP, Me, 2000. Same error every time. I have the software running on my homebuilt PC which was originally built as Win98 and upgraded from there to Win10, so I know the software is capable of running in Win10.Quote:
Originally Posted by David Ferguson
Does anyone have any suggestions on how to load and run the software in Win10? TIA....
Pretty sure it needs a 32-bit OS. All the modern computers (from the last 10 years) would be 64-bit, where as your old upgraded computer probably stayed 32-bit.
Fortunately, or unfortunately, the PC that WinGeo 4.01 is currently operating on is a 64 bit operating system, as is the laptop that I am trying to load the software onto. I do not know where to go from here, but thank you for the suggestion.Quote:
Originally Posted by David Ferguson
I found that the WinGeo install program was the issue and not the program itself. What I did was to load the programs directly into the program files, I created a folder in the Program Files, Mitchell, and load the Mitchell program folders and files into that Folder. I then created short cuts to go to the various Mitchell programs and placed the short cuts on the Windows screen.
I did this for both of my 86 bit Dell confusers. This was done in an earlier version of Windows but the programs work just fine in Windows 10.
I will give that a try later this evening. Thank you, Steve.
BTW: Will we see you at the Runoffs later this month?
I will be there. I have only been going to that track for well over 60 years. There are some cars in the museum the I worked on as a kid. I got to clean the body work after the dirt races.Quote:
Originally Posted by Gary Godula
Hi all, as you are looking for Suspension Analysis Tools, I have created a range of tools that are based on Excel. Many privateers and small teams do use it with great results. You can read more here:
http://www.dynatune-xl.com/dynatune-sdm.html
These 2 documents below have been quite useful for many to enhance their understanding of what is actually important when creating a suspension geometry.
http://www.dynatune-xl.com/uploads/1...ndamentals.pdf
http://www.dynatune-xl.com/uploads/1...ion_design.pdf
if you need more info, drop me a message on my site.
Paul
Wingeo is very good....even the early 3 version.Quote:
Originally Posted by S Lathrop
Jerry Hodges
JDR Race Cars