FSAE - Solving Suspension Forces with Matrix Method

[@martinfillola733]

Thank you, xRacing appreciates

[@ИванНовожилов-э9з]

great explanation - big thanks!

[@ShayWard-h9w]

Thank you for this walkthrough, can you please explain to me what situation you would change the moment arm values?

[@fsaeillumina7391]

assuming you mean 'in what situation would you change the point that you take the moment arms about?', and the answer is really just the first time you fill in the spreadsheet, it can be a useful check that nothing is wrong with your calculations... You should be able to set the xyz coordinates anywhere, and the output of forces in your control arms should never change- if they do you have a mistake somewhere.

[@bhushansalunke1205]

Very much helpful !

[@CCNproductions1324]

Hey quick question. So if your coordinate system is set up how I think it is (x- positive forward, y positive to left side of vehicle, z positive upwards), I understand why in a braking and right hand cornering case your input x is negative but why is your y positive? If we are looking for max load on the left side of the car, shouldn't the y be negative to simulate a right hand cornering case?

[@fsaeillumina7391]

Good catch! Looks like for loadcase 21, our inside wheel, most of the arms should be in tension, but they're in compression! I think you're right.

[@adityanarayan5641]

Under Maximum Braking conditions why is the longitudinal g negative instead of positive, the load transfer is on the front wheels of the tires??same while a right-hand turn in vehicle the load transfer will be on the outer tires the left tires so the lateral g should be also positive, but it is provided negative.

[@harshaskv3215]

How do you find Fx_applied?

[@fsaeillumina7391]

Did the same method as Fy

[@mjswoo]

Is there a double wishbone geometry example? or how can this be applied on to a double wishbone suspension?

[@fsaeillumina7391]

This is for double wishbone

[@thegoldenkeyboard8961]

@@fsaeillumina7391 man thought it was a 3 bone suspension or smt 😂

[@henrydrums8825]

how did you measure acceleration on a "reverse braking" case?

[@fsaeillumina7391]

Just conservatively guessed based on braking G's without aero.

[@pedromelro4257]

hi mate, can u just explain to me how did you get those values that are in blue tables based on your car model? I know they are your measurements but explain them a bit better. i appreciate your work

[@haeyoon3793]

did you find the answer if you find it, i want you to share the answer please

[@fsaeillumina7391]

m_carPlusDriver is the mass of the car plus driver h_centerOfGravity is the height of the center of gravity of the car. r_tireLoaded is the loaded radius of the tire. Essentially how high the center of the axle is off the ground when there's a driver in the car (basically accounts for tire deflection). For track/wheelbase google will help you out.

[@haeyoon3793]

can you explain how to get blue forces of 36:30 screen?

[@harshaskv3215]

May I know how you found Fx_applied while you were calculating applied forces

[@fsaeillumina7391]

Just vector addition of the forces at the ball joint. Since my example is a pullrod, the vector sum of fore upper control arm, aft upper control arm and the pullrod. For the lower one, just the vector sum of the two lower control arm tubes.

[@thegoldenkeyboard8961]

Terrifying these things, trying to grasp how the universe works, just look at what were doing, what is a force? A Material? What am I saying? I have been staying up for a month just about ready to give up. What is giving up? What if I give down. I apologize.

[@Alejandro-tp8hd]

you're making a good point