PLz, Skidpad, autocross and suspension doubts!

[Necrobata]

Well, i wanted to check out the parameters of design of our suspension, my advisors are telling me that i should consider doing the maths based on the most extreme scenario for the suspension.

and i was thinking after watching some youtube videos, the autocross seems to me like the top test for the suspension geometry, but also i think it is the skidpad :s

One of my advisors are telling me, well start the maths by knowing the speed and radius of the turn, that will give you a head start, the other told me that i should do that with a 9m radius turn with 60km/h straight but seems like a little extreme cuz with that speed the load transfer in turns results in a 95%-5% wich seems a little high to me.

So, i know ive been dispersed but here are the questions:

1)should i look for the average speed in the skidpad and base my numbers with that? or should i look for the speed at the hard airpins of the autocross?

2) is it ok to do my math with speeds that are higher than the average? or speeds that no one ever gets? seems to me like it will turn out as an overdesign or am i wrong? my advisor told me straight: get 60km/h on skidpad and i doubt that criteria.

3) Whats the average load transfer in the skidpad? whats the safe/highest value of it? 30-70%? 5-95%?

4)also, i read the milikens suspension part and i quite dont get how the roll axis should be settled (higher on back, lower in front, under or over the floor?) if someone could point me in the right direction i would apreciate it.

Thanks you very much for reading.
Att: Angelo S.

[Necrobata]

Well, i wanted to check out the parameters of design of our suspension, my advisors are telling me that i should consider doing the maths based on the most extreme scenario for the suspension.

and i was thinking after watching some youtube videos, the autocross seems to me like the top test for the suspension geometry, but also i think it is the skidpad :s

One of my advisors are telling me, well start the maths by knowing the speed and radius of the turn, that will give you a head start, the other told me that i should do that with a 9m radius turn with 60km/h straight but seems like a little extreme cuz with that speed the load transfer in turns results in a 95%-5% wich seems a little high to me.

So, i know ive been dispersed but here are the questions:

1)should i look for the average speed in the skidpad and base my numbers with that? or should i look for the speed at the hard airpins of the autocross?

2) is it ok to do my math with speeds that are higher than the average? or speeds that no one ever gets? seems to me like it will turn out as an overdesign or am i wrong? my advisor told me straight: get 60km/h on skidpad and i doubt that criteria.

3) Whats the average load transfer in the skidpad? whats the safe/highest value of it? 30-70%? 5-95%?

4)also, i read the milikens suspension part and i quite dont get how the roll axis should be settled (higher on back, lower in front, under or over the floor?) if someone could point me in the right direction i would apreciate it.

Thanks you very much for reading.
Att: Angelo S.

[Dash]

You could take the top results from the skidpad and use the dimensions they give you in the rulebook to back out lateral g's and velocity. Same thing could probably be done with the autocross scores to give you an average velocity.

Just watching the autocross and endurance races from the sidelines, I can tell you that I've seen a great many teams pick a wheel off the ground in a braking and turning scenario as well as seeing a few beastly cars pick one up in a turning and acceleration scenario.

It is always better to have something that is stronger than it needs to be, a disabled car doesn't earn many points. Something that I will be trying to incorporate in our design next time around will be fatigue factors. This will probably increase the size/weight of a few components.

[StevenWebb]

suspension loads will be higher when the tyres are hot, so going off skidpad times with cold tyres will give you a car that breaks on the 2nd lap of endurance.

one thing to think about is the tilt test- which is designed to make sure cars cans fall over with some of the cornering forces we see at competition. so if the scruitineers think a car might be capable of 1.7g, so should you. add to that what safety factors you want and you can use that as a baseline for your first car. then on next years car you can use some of your own data to help get a more accurate number.

[JDS]

For your roll center height determination, if you are dealing purely with kinematic roll centers (as I believe most teams do), set up a weight transfer spreadsheet that separates weight transfer into geometric and elastic weight transfer. Make changes to the front and rear roll centers to see how the changes effect the individual weight transfers. This will be a good starting point in determining your roll center heights.

[Rotary Sprocket]

What tires do you plan on using? You won't be able to determine any suspension loads until you know the tire's characteristics.

In the way of component design it's probably a good idea to "overbuild" your components just because calculations don't account for every scenario you will encounter. Once you get a car built and test it, you can use the data you gather to refine your designs and start saving weight.

Roll center height (RCH) plays a large role in how the car will handle along with your a-arm geometry. Use your calculations to get a ballpark figure for RCH and then set up your car to make the RCH adjustable around your ballpark figure and play around with the different heights during testing. This way you can see first hand how your car is affected when you change something.