Let's talk about bit from swaybars or antirollbars as those are sometimes called. Simple device, typically metal bar that connects left and right side wheels to each other, when car rolls to right, left side wheel goes down and right side wheel goes up, swaybar then limits right side wheel going up by trying to move left side wheel up also, as swaybar is attached to car's body/chassis it then results forces to try keep car at level. You can attach another swaybar to your car if you already have one by simply attaching new one to old one with metal straps from ends and from center part, surprisingly it works, simple that is. Strength is evaluated typically by diameter, base model cars have thinner and sporty models have thicker. There are also second thing affecting final rate of swaybar, that is effective lever, that is from bar end to typically first corner, longer the distance thicker swaybar needs to be for same effect. In rFactor however simple things get confusing, this is front swaybar settings: Code: SpringBasedAntiSway=0 // 0=diameter-based, 1=spring-based AllowNoAntiSway=0 // Whether first setting gets overridden to mean no antisway bar FrontAntiSwayBase=0.0 FrontAntiSwayRange=(0.01746, 0.0000, 0) FrontAntiSwaySetting=0 FrontAntiSwayRate=(0.0, 0.0) // (base, power), so rate = base * (diameter in meters ^ power) 1st and 2nd line are simple enough, I want to use diameter based because I know my swaybar diameter is 0.01746 meters so first line is 0 that Swaybase and SwayRange mean meters, not spring units, I guess at least. 3rd & 4th line, I'm not sure if I should input my value to base or range though, I want no adjustments for this setting, so I guess base would work too. 5th line is related to above. 6th line is then something that puzzles me, is this some kind of material choosing line, so that I should input alloy steel material's number to that line, which number I have no idea of as car manufacturer's specification states Alloy steel diameter 0.688 inches (varies a bit from source to source from my memory). It probably is just typical spring steel however, same as leaf springs etc. With always so reliable try values from other vehicles I have ended up 0 body roll most of the time, so I left that to zero, there is some effect still, but I don't know if that is placebo really. Then comes question of effective lever, where do you put stuff like 30cm for effective lever? Now if I use values that I can get with car factory, I end up with vehicle that has iron bars welded so that any roll is eliminated completely, but there I can input numbers I can work with, numbers I can find, however it does not work, I did also read somewhere that arb section of it would be buggy, so I guess it is partly of that too. There is also some roll/deg stuff, but parts of cars and their technical documentation are not giving such, can't work with such stuff, especially as I can't get car to measure it's roll, so there is perhaps some other way to this, how people are converting their real world numbers to rfactor numbers and how ISI does this? So word is free, let's talk
Hi, I was just at your page looking at damage information, very helpful. Here is what I did for ARB. SwayBase is defined as, "// extra anti-sway from tube twisting," I think of it as preload. You are correct that Range is in meters, this is what shows in the garage when "SpringBasedAntiSway=0" Setting is the default value selection AntiSwayRate is the important bit, as far as I can see the power parameter to it is always 4.0. Pretty sure this links to the shape of the bar, and since you've got a tube/cylinder, use 4.0. That leaves the base. There are a few equations out there to calculate an ARB rate using diam, and lever lengths google around. I made a rough solid model and used FEA to get the deflection for a certain load. Then I changed what hole the load was acting on. Then math! My actual bar was .0207 in diam. I have 4 settings. I measured 25926.89 N/m for the stiffest setting and 19849.15 N/m for the softest. From the equation 25926.89/.0207^4 I got a base of 1.41211167368099e11. Solve to figure out the lowest diam(.01935) from (19849.15/1.412...e11)^.25 Solve for the step: (.0207-0.0193628026)/(4-1)=0.0004457325 because I need another setting for detached my lowest value is: 0.0193628026-0.0004457325=0.0189170701 With some rounding I get: Code: RearAntiSwayRange=(0.0189,0.00045,5) RearAntiSwaySetting=5 RearAntiSwayRate=(1.412111673681e11,4.0) Most of the equations I've found use Imperial units and some of the constants I could not track down, thus couldn't figure units/conversion. I was using carbon steel as my material for the solids.
Thanks, that explains it quite well, so what I need now is to look for equation for ARB lever and diameter to get rate, then I should get my base with myrate/mydiameter^4 if I understood it correctly.
Correct. Didn't have the time earlier to post links/equations. Here's some good stuff: http://www.optimumg.com/docs/Springs&Dampers_Tech_Tip_2.pdf http://www.speed-wiz.com/calculations/suspension/anti-roll-bar-calculation.htm http://www.v8sho.com/SHO/rearswaybar.htm Thought I downloaded a spreadsheet with another equation more suited to a bladed ARB, but I can't find it on my HD. All of the equations I found estimated high. If you run across the exact alloy someone is using for a bar can you post here. I don't think carbon steel is too far off, but would like to see how the actual material changes things. Right now my bars seem stiff, no doubt related to the crudeness of the 3d solid.
Thx from those, saves lot of my time AMA paper from Pontiac claims same term Alloy steel for rear leaf springs also, no much more of information there either. I would suspect that material is same as with rear leaf springs then. For coil springs one source claims modulus of 78 500 http://www.pontiacracing.net/js_coil_spring_rate.htm I have used 80 000 in my calculator. This site again offers different units, but mentions Chrome vanadium, I think that chrome silica(?) might be possible too, no exact info though, but Mid-west spring has excellent info and calculator (which I can't find from their site now, but I can email that to whom would like to have it) available for free. http://www.mwspring.com/materials.html For conversion, I believe this can be used: http://www.convertunits.com/from/pound/square+inch+%5Babsolute%5D/to/newton/square+millimetre I use that site a lot to convert between imperial and metric units, it can convert almost any unit there is. Oh, I recently found many good PDF files from my temp folder, acrobat seems to not delete anything from temp edit: I just put my observation here as I have no better place for it at the moment. ISI cars in rF1, Howston, Hammer, ZR, Rayzor (Lienz addon cars) seem to use FrontAntiSwayRate=(1.11e11, 4.0), only diameter varies. So they all have same shape and same material ARB I suspect. Then there is unclear aspect for me with swaybar mounting point to lower control arm, as that is usually away from hub/spindle it should induce some sort of motion ratio additional to that near end of swaybar angle that causes lever effect. Need to study that bit more also and also check those links with time that lordpantsington gave as it may become more clear from there, I try to update my understanding then here so that one reading this in future don't need to invent wheel all over again and can just apply known numbers and get result. All due their time, though.
My (shear or torsion) modulus for carbon steel worked out to be 77,519.379845 N/mm^2 [MPa] If we can jump into springs talk too without being OT, H&R was mentioned here as using DIN 54 SI CR 6 for their springs. DERP! Same site: "H&R Sport Sway Bars are crafted from a special (hf) 50CrV4 steel alloy—the highest tensile strength available." lolz http://www.matbase.com/material/ferrous-metals/spring-steel/50crv4/properties http://www.matweb.com/search/DataSheet.aspx?MatGUID=ce07ecf60d4140b08450de0fe9e1e176 http://www.saarstahl.com/fileadmin/saarstahl_extranet/images/04_produkte/walzstahlsorten/english/7102_54SiCr6.pdf Another link showing 78500 for both materials: http://www.fwg.de/fileadmin/Downloads/matde.htm Another site for material properties: http://www.matweb.com/index.aspx I also thought it interesting that all of the ISI have the same base.
That is good info, thank you again Excel formula for solving stiffness: Code: =(500000*D1^4)/(0.4244*A1^2*B1+0.2264*C1^3) Where A, B, C, D is measurements of swaybar according to image on this page: http://www.v8sho.com/SHO/rearswaybar.htm Use imperial units This converts result to SI units N/m Code: cell of result from previous/5.71014716277*1000 This converts again previous N/m to rFactor units Code: =cell of Result in SI units / ((Cell of diameter of swaybar in inches*25.4/1000)^4) Hopefully it is understandable, here is quick recap with cell addresses first and what I have put in that cell. Code: A1 = measurement A B1 = measurement B C1 = measurement C D1 = measurement D B4 =(500000*D1^4)/(0.4244*A1^2*B1+0.2264*C1^3) B5 =B4/5.71014716277*1000 H4 =B5/((D1*25.4/1000)^4) Should be possible to remake with any spreadsheet suite, Libre office being free open source alternative. So anyone has 1967 Firebird swaybar under the bed to get measurements from? I have one pic, but it has nothing known size to calculate measurements from pixels and even that would be bit off, then there is lot of other cars too, but that is another issue Formula for coil springs that I have used is this (metric units, mm) Code: =C2*C3^4/(8*C5*(C4-C3/2)^3)*1000 For leaf springs (this one uses imperial units for change, inches) Code: =B8*C8/12*(1000*D8/E8)^3-14.09 As those are gibberish without knowing what is in the cells, you can download my calculator tools from this link, it includes also damper/shock absorber calculations, but not yet swaybar calculations as I need to make image or ask permission to use image from SVO site. http://jtbo.pp.fi/tiedostot/rfactor/all_calculators_v3b_volvo.zip Of course there might be errors and I'm glad if those can be spotted and tool refined further. Link in my sig says suspension good read, there is more about that and lot more about what makes car to be car and not paperbag, for those interested from this side subject, which is closely related to original subject also.
Found my documents For a Torsion bar: (Imperial units) Spring Rate=1150000*(Diameter of bar^4)/(Bar effective Length*(Arm Length^2))-1150000*(Hole diameter for Hollow bar^4)/(Bar effective Length*(Arm Length^2)) ^This formula was what I was having fits understanding, Sheer Modulus should be 11500000. and a spread sheet which is the same equation you have: http://bndtechsource.ucoz.com/load/suspension_design/tubular_vs_solid_arb_excel_calculator/2-1-0-7
I have been thinking motion ratio aspect and I came to conclusion that it must be same as springs as Swaybar is kind of spring, that increases spring rate of outside wheel and decreases spring rate of inside wheel, kind of. So if I have swaybar mounted middle of lower A-arm, then motion ratio would be 2:1 and as I did calculate 1.36e11 rate, because of motion ratio, rate would become half of that, so I believe that my rate should be 6.8e10 in confusing science numbers. But then again, I had to pick swaybar lengths pretty much by guessing and estimating as I don't have measurements or access to car, yet, so it can be way off still, but at least now car is showing signs of problems in handling that it should, still 0.1G's too much, but slowly to better. lordpantsington, I did try that formula, but for some reason I got negative numbers. Probably I made some error, I did check formula and for me it looks to be same, but as my bar is not hollow I did omit part which has hollow bar on it.
Hmmm, I never really bothered with motion ratio on the ARB. Your logic/math does make sense. Because there is no position location for ARB available to rf, that it is acting directly on the wheels. Follows a trend rf has of just cutting right to the chase. The equation without the hollow component is: Spring Rate=1150000*(Diameter of bar^4)/(Bar effective Length*(Arm Length^2)), still not sure about the 1150000.
In CarFactory by Kangaloosh, there are place for ARB motion ratio also, but there is something funny about ARB calculation of that program as I keep tinkering with values it essentially gives less and less effect what change I type and returning to original values does not give original results, so I can't use that part of CarFactory. I can confirm that formula is missing one zero, 1150000 gives 6.9pounds/inch when 11500000 gives 69 and with other formula I got 73, so it is relatively close. Another thing one should take account is rubber bushings, according to v8sho site image text those cand considerably lower the stifness. What I think is that those might do ARB rate to be more kind of progressive as is case with bumpstops and springs. After some point of roll stiffness is of course more of solidly mounted bar that rfactor model assumes from my understanding. One thing still puzzles me, in car factory generator page there is checkbox to modify output for rfactor v1.xxx and popup note mentions that diameter based arb rate is halved by rfactor. Could it be because there is hardcoded motion ratio and rubber bushing effect in rFactor1? Does this apply to rFactor2? All I know is that with specific diameter and stiffness of bar that has 300mm arm and 1300mm length, I get too stiff bar, by applying motion ratio I get something that is more close to what I have read from the car I'm building. Maybe it could be estimated someway with removal of bumpstops and driving in circle, knowing wheelrate, cog, mass etc it might be possible to figure out body roll that should be and thus amount o suspension movement and from there it might be possible to calculate comparison what roll should be and what it is. However it sounds bit complicated for my head, it is so much easier to look photo of car and drive the same manner and compare to that, not very scientific or accurate though. Swaybars are however important bits together with springs, dampers, cog and inertias those are main parts affect how car feels, of course not forgetting tires, so more effort to get them right is important.
If SpringBasedAntiSway=0 then you will not have to worry about and compensate for the bug. I use Kangaloosh mainly for Kinematic analysis, although I don't trust it completely. I too have noticed funny behavior, mainly dealing with ride height and suspension travel. At one point I figured out that K! is using this: BT=(free bump travel @ X ride height) - X ride height + 1 RT= - (free rebound travel @ X ride height) - X ride height - 1 The +/-1 I can only attribute to error in the code.
That is really good to know, I hope that rF2 does not have same issue, but then again, I'm always using diameter based swaybar as that is values I'm more familiar from real world cars. I make suspension geometry, bars etc with K! as it is bit much for me to calculate location of bars, of course if I can have real data for a-arm suspension, then it would be only matter of inputting coordinates, but pherson emulation goes over my head completely as when I would need to locate bars and joints to get correct camber change and roll center movement, I just hope that software can do it's job. I will learn to do it manually some day as I have learned many other things, but it seem to take bit more than 7 years that I have been now attempted to do it in rfactor
Swaybar material in 1970 Cadillac Eldorado according to GM is Source: http://www.gmheritagecenter.com/gm-heritage-archive/vehicle-information-kits.html Cadillac 1970, in PDF AMA specifications are at the end of document, PDF page 328 of 364 states material for swaybar. Same document specifies material for other Cadillac models to be at page 357.
