Do we need suspension?

[hardingfv32]

fastback33

"Sorry but, this question is a catch 22. If you have perfectly infinite grip you don't need suspension as that is what it is there for, tuning grip. Essentially you cant have one with out the other though. The question is, how do you plan to construct these "perfect" tires, or perfectly smooth track? ANything even at the microscopic level still has ridges and is rough.

Your question is flawed, nothing, no one, can ever be perfect. Interesting thought but has no end value."

The question is not flawed. It is highly restricted to what issue I wish to focus on. I do not want to discuss tires and the issues surrounding their use if at all possible. It makes the topic too broad and everyone quickly becomes lost or bored. This is just a normal scientific research technique to limit or control as many variables as possible. If you can not ASSUME certain thinks are perfect, then disregard the thread.

Brian

[Jeffsvilleusa]

The hypothetical situation makes me think of railroad tracks.

No tires. Perfectly smooth.

Does this fit the scenario, or am I way off base?

And locomotives don't have suspension as far as I know!!

[DaveW]

Of what value is pitch? Isn't it just a by-product of having a suspension? The load transfer is the same regardless if there is a pitch or not.

"The best suspension is no suspension" is a famous Colin Chapman quote.

The change of front & rear ride heights with airspeed are often (GP2 & LMP, for example) used to manage downforce &, particularly, drag, as pointed out by JT.

"If you are in a queue of traffic you are going the wrong way" was also attributed to ACBC. Both statements described his engineering philosophy, I think, & were not intended to be taken literally.

[DaveW]

... And locomotives don't have suspension as far as I know!!

I rather think they did, see http://en.wikipedia.org/wiki/Steam_loco ... components, but I understand your point.

[ubrben]

fastback33


The question is not flawed. It is highly restricted to what issue I wish to focus on. I do not want to discuss tires and the issues surrounding their use if at all possible. It makes the topic too broad and everyone quickly becomes lost or bored. This is just a normal scientific research technique to limit or control as many variables as possible. If you can not ASSUME certain thinks are perfect, then disregard the thread.

Brian

You need suspension to make the tyre work. Tyres that work mean you have grip and you go round corners quickly.

Ignoring tyres when talking about suspension requirements is completely stupid. You can dress it up in talk of scientific method, etc, but it doesn't change the fact that it's a stupid assumption.

Ben

[Jersey Tom]

In addition to Ben's comments (which I certainly agree with)...

Isolation of variables or ideas is a good analytical method in general. For example, I am a firm believer in learning/teaching vehicle handling dynamics by starting with a bicycle model and building from there. However, you DO need to be cognizant of what assumptions and constraints you're making. As Ben says, there's a point where you oversimplify things or make poor assumptions... and your abstraction of reality just becomes a fantasy.

[DaveKillens]

It's an interesting exercise in theoretical concepts, but ignoring real world problems is being in denial. Why not remove the variable of forward velocity?

Heck, if we're going to ignore the sideways shift of forces in a corner, or the forward shift of forces under braking, crosswinds and the movement of the driver as he reaches down to adjust the brake balance, why not ignore the forward velocity component?

That way, the use of square tires it perfectly logical. It's nice to go on a camping trip down into the land of mental exercises, but somewhere along the line we do have to start to take reality into account.

Second argument ...

How does your theory dovetail into this picture, because it's on a glass-smooth track, and only in a straight line, and heck, no suspension travel either. The torque is distorting the tire, do we also discount torque?

[Lurk]

But, given the opportunity, if I had to design and tune a racecar with a suspension to compete against an equivalent vehicle with rigid links, I'm fairly certain of being able to run circles around the competition.

You have some radiocontrol cars which we call in french "planche" (plank)
It has any suspension at all (except tyres, you can't remove them from the equation especially concerning Formula one) and trust me, it competes like hell against the suspended ones.

[Jersey Tom]

Eh...

Racecar:


Not racecar:

[Lurk]

Err... Engine, chassis (sometimes with a carbonfiber-made upperdeck), 4 wheels, even a bodywork which generate some downforce (not visible in this picture but they race with) and more than 2hp per kg. What it is if it is not a race car?

The only difference is the scale. Principles remains the same.

[Jersey Tom]

Your tires are made from foam for one, are they not? Or are they a pneumatic fabric/rubber composite?

[hardingfv32]

DaveW

"The change of front & rear ride heights with airspeed are often (GP2 & LMP, for example) used to manage downforce &, particularly, drag, as pointed out by JT."

There could be something to aero and suspensions, but let's go into more detail with this narrow point:

What is the nature or cause of the imbalance that you are proposing? Is it caused by the chassis or the aero package?

The goal is no suspension, not simplicity. We could have adjustable aero features.

Brian

[hardingfv32]

DaveKillens

"It's an interesting exercise in theoretical concepts, but ignoring real world problems is being in denial."

Ignoring a ...specific part... of the real world is clearly part of the basic question or problem. Consider it a mental challenge and see what you can come up with.

Brian

[hardingfv32]

No suspension and tire issues or complication.

So far the only problem that the tires create that has been articulated is one of damping the tires movements. We can have camber with no suspension, so a the use of preset camber would solve the issue of lateral tire flex. Is this not correct?

The issue of dampening the tires own movements is harder to solve. Could not find much on the subject of tire dampening. Tires do have some damping built in to them, so I supposes more dampen could be added to the tires design.

I think the main question would be:

Why do the tires have flexible side walls?

Is it not just to cope with road or track surface issues? With a dead some track why do I need a pneumatic tire?

....So I will reiterate my bold statement that suspensions are only necessary to cope with track/road irregularities.

Brian

[Jersey Tom]

Consider the following:

Sub-limit handling and limit trim (let's wrap these together and call it "balance") are a function of tire states. Period. Load, camber angle, slip angle, etc. The only reason downforce plays into balance is by changing tire states (load distribution). Likewise, springs and bars (even very stiff ones) are there to adjust tire loads.

If you have no suspension, as a vehicle designer or tuning engineer, you have no way of tuning handling or balance - even on a perfectly smooth track. Only exception to this is nose weight, which may or may not do much, and generally will be insufficient by itself.