20 replies to this topic

[Wright&Wright]

Not entirely sure whether this is the best place to put this but what the hell...

 

I've created quite a basic vehicle cornering model in excel with the settings of a Mini. It basically calculates the vertical wheel loads at each corner, the maximum lateral force available at each corner/axle and then the required lateral force.

 

The parameters on the left are all there for you to have a play about with and I'm sure a lot of people will be surprised by what they find. Might put to bed a few myths and false information people seem to spout about the centre of gravity and its effects 

 

There's the option to simulate what happens when a load from the engine is introduced and the effect it has on weight transfer. 

I'm hoping to create a bit more of a complex model using a look up chart for slip angles and lateral forces. 

 

A bit of food for thought...

 

P.S. If anyone thinks I've messed up with my calcs then feel free to offer corrections!

 

https://www.dropbox....sheet.xlsx?dl=0

 

 

 

Edited by Wright&Wright, 30 November 2014 - 02:07 AM.

[Mini 360]

Wow!  Good effort!  

[Wright&Wright]

Wow!  Good effort!  

 

Thanks!

 

I should explain to those who may not completely understand the notation that, F_y is the lateral force at the tyre, the fraction of weight transfer is largely to do with spring rates and anti-roll bar settings and is at this point, wildly assumed. I'll look at developing the proportion of weight transfer based upon spring rates etc. later on.

 

Also, the engine power 'cell' is there purely to induce a longitudinal acceleration, if you want the perspective of a balanced car at the apex of the corner, leave this value as 0. 

[Dr s]

That might answer the question of those golf cart wheels. 

 

I reckon a mini can easily exceed a load of 250kg on a front wheel with a bit of ambition what does the science say?

[Wright&Wright]

Well that would all depend on the material of the wheel and how hard you're cornering! 

 

The screenshot above has the car cornering at 78 MPH. A corner radius of 160m is akin to the long sweeping Gerard's corner at Mallory.

 

Calculations involving an island of 30m radius and at 36 MPH provide wheel loads that suggest the 'equivalent weight' at the outside front is about 389kg. 

 

I don't think I'd be placing 389kg on top of golf-buggy wheels!

[Ethel]

Impressive,

 

What effect would the spring rates show though? Wouldn't the springs be static & just transfer the load from the body to the wheels, unless there's some acceleration to change the force they are reacting to?

 

You know there's similar commercial software, if you want something to assess your work against.

[Wright&Wright]

Impressive,

 

What effect would the spring rates show though? Wouldn't the springs be static & just transfer the load from the body to the wheels, unless there's some acceleration to change the force they are reacting to?

 

You know there's similar commercial software, if you want something to assess your work against.

 

The effect of spring rate is the transferring of weight, correct. It's this proportion of weight transfer from front to back/corner to corner that affects wheel loadings.

Weight transfers in a greater proportion to the stiffer springs. That's how different anti-roll bar settings can produce different handling traits i.e understeer or oversteer etc. 

 

Yeah, it's part of my degree and dissertation at the moment. I'm developing more complex vehicle models in conjunction with vehicle mounted sensors to estimate tyre models.

[nicklouse]

Question.

I am guessing you are only dealing with constants. So as to disregard the changing roll center and roll axis changing the CoG?

[Wright&Wright]

Question.

I am guessing you are only dealing with constants. So as to disregard the changing roll center and roll axis changing the CoG?

 

Yeah that's one of the major limitations unfortunately, it doesn't take into account suspension geometry. The principle was to educate people on the effects of basic vehicle design. When you look into roll angles, camber compensation, front to rear roll axis etc. then you're getting into the territory of complex video game and race simulation packages.

I'm trying to develop it a bit more so people can get a good understanding of where to start when thinking about coilovers and where to remove/add weight.

[nicklouse]

All you need is some wood and some string.

Google "The String computer"

What degree are you doing?

[Wright&Wright]

All you need is some wood and some string.

Google "The String computer"

What degree are you doing?

 

Haha, yeah I've seen that before.

 

Working out the roll center migration, roll arms etc. isn't the difficult part. The application of that into of the model is. 

I'll end up with a full vehicle package soon!

 

Currently at Brookes studying Motorsport Engineering.

[Jayme 1275]

+10 nerd points 

 

pretty sweet dude, love to see people applying engineering to mini problems. 

[nicklouse]

All you need is some wood and some string.
Google "The String computer"
What degree are you doing?

 
Haha, yeah I've seen that before.
 
Working out the roll center migration, roll arms etc. isn't the difficult part. The application of that into of the model is. 
I'll end up with a full vehicle package soon!
 
Currently at Brookes studying Motorsport Engineering.

Nice and nice.

Have you measured up the front hub ball joints yet? I have the info somewhere.

[Wright&Wright]

All you need is some wood and some string.
Google "The String computer"
What degree are you doing?

 
Haha, yeah I've seen that before.
 
Working out the roll center migration, roll arms etc. isn't the difficult part. The application of that into of the model is. 
I'll end up with a full vehicle package soon!
 
Currently at Brookes studying Motorsport Engineering.

Nice and nice.

Have you measured up the front hub ball joints yet? I have the info somewhere.

Not yet, I'm away from home at the minute but I was hoping to measure up sometime next weekend. If you've got the info it'd save me a lot of trouble!

[nicklouse]

Pm me your email and I will see what I can dig out.

My dissertation is on one of my PCs or might be on a memory stick somewhere.