20 replies to this topic

[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.

 

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.

 

 

 

Does it though?

 

Of course there'll be an effect in the real (dynamic) world, but the force pushing on either side of the spring will be equal. It would be the same as if the spring was rock solid, if calculated instantaneously and ignoring any accelerations along the same axis as the spring .

 

I'm probably missing something  . I guess I'll have to think more about see-saw effect of the springs acting around the c-o-g, but that sounds immensely  complicated unless you assume a uniform weight distribution.

[nicklouse]

Ah the looking at a single item and then believing it is true.

Unfortunately suspension has to be looked at as a complete system. As every little change in something effects something else.

[Jayme 1275]

 

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.

 

 

I was at brookes aswell, guessing your in your third year if you are doing your dissertation, if you are i was prob in your lectures before i left lol Left last February after student finance fecking things up for me.

Edited by Jayme 1275, 28 November 2014 - 08:15 PM.

[Wright&Wright]

Ahh that's a shame Jayme! They're not the best outfit I've had to deal with.

Yeah unfortunately the complicated nature of vehicle dynamics means we only get a rough stab in the dark without venturing into complex mathematical models. This wouldn't be close enough for a race car but road vehicles aren't performing anywhere near the edge of the same envelope. I'm more than interested if anybody has some upgrades to the model they feel would be helpful!

[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.
 
 

 
Does it though?
 
Of course there'll be an effect in the real (dynamic) world, but the force pushing on either side of the spring will be equal. It would be the same as if the spring was rock solid, if calculated instantaneously and ignoring any accelerations along the same axis as the spring .
 
I'm probably missing something  . I guess I'll have to think more about see-saw effect of the springs acting around the c-o-g, but that sounds immensely  complicated unless you assume a uniform weight distribution.

I'll try to update the model using cornering stiffness and tyre slip angles to show the effect it has on lateral and vertical forces. The longitudinal weight transfer is affected by the corner stiffness. If you set the model to 0.5 or equal weight transfer at the front and rear, you'll see the effect this has on wheel loadings.

Again, it's all theoretical and was just a simplified version of steady state cornering for race cars. It assumes far too much but at least it gives a representation of how different components of car design can influence balance.

Greg

[Wright&Wright]

Should be noted that the rear corner forces produced in the orange boxes are incorrect.

Q5 in these cells should be changed to Q6.

 

I'll amend the file download but it's just a heads up for those who already have it.