Do we need suspension?

[DaveW]

I have a honest belief that a suspension is only required because of track or surface irregularities.

I would not like to part a man from his religion, Brian. My only comment would be that the F1 aerodynamic community would probably welcome you with open arms.

I appreciate the tuning tools that you are discussing, but just pick one reason for an imbalance and expand on it.

Tyre temperatures. I shouldn't need to expand.

I can also appreciate that the aero system is capable of generating an imbalance. As an example, does the performance ratio of the front and rear wings always very with speed?

Not in the third universe on the left.

My potted version of this thread:

2 + 2 = 5. Please articulate why you think this is incorrect.
<articulation>
You are wrong. The first 2 is clearly a 3.
<no it's not>
I make the rules & I say it is.

More seriously, I think you should heed JT's advice.

[hardingfv32]

You have yet to develop a reason that cars need a suspension... when the track is dead smooth.

"your balance is fixed and NOT necessarily neutral" So it is tour opinion that the balance is fixed?
So then your only concern, in this narrow regard, is fixing an out of balance situation. Could this be done with a change of camber or tire size for example?

Brian

[hardingfv32]

DaveW

Is it not true that you could fix a tire temp issue with a change of size or compound?

Brian

[Jeffsvilleusa]

It seems the bottom line is that you cannot divorce suspension from tire performance regardless of track conditions. If the proposed hypothetical model is without tire-associated variables it isn't really relevant to car racing.

Maybe in a perfect theoretical world suspension should purely be for dealing with track surface irregularities, but in reality it also perfects tire performance regardless of track conditions.

[hardingfv32]

Jeffsvilleusa

"but in reality it also perfects tire performance regardless of track conditions"

Provide an example where a suspension is the ONLY WAY can improve tire performance when the track is dead smooth.

Brian

[Jeffsvilleusa]

Unfortunately, I am unable to do that. You see, I am what they call a "layman."

So, I took it upon myself to engage in this technical discussion with all the understanding at my disposal, which does not cover all possible areas to maximize tire performance outside of suspension set up.

I should probably take JerseyTom's advice and learn a thing or two before participating in this discussion further. That said, I have found it interesting.

[Ciro Pabón]

Let's help Jeffsville a bit, something I really like to do, by presenting a typical layman tool. It's called "reductio ad absurdum", which is as useful as the mind experiments mentioned by JTom. So, here we go.

Even at the smoothest track surface in the world, one that might comply with hardingfv propositions, that is, dragster tracks specially designed for smoothness, actually, so smooth that the largest difference in height between any two parts of the track is thinner than a regular piece of paper, I repeat, even at this super-hyper-extra-mega-flat track with no curves and essentially no wheel braking you need a suspension.

The reason?

Well, any irregularity in tyre grip not (more or less) handled by suspension will make a piston blow out spectacularly by variations on engine load. That's a common occurrence in dragster races and it is the reason why drag tracks have to be so smooth.

Top dragster blows up its engine. Don't... blink... or you'll miss it.
[youtube]http://www.youtube.com/watch?v=ljYF6IDKu8U[/youtube]

I hope this argument shows that suspensions are there not only to balance car corners, as JTom, always the tyre engineer, presumes happily, but I guess you'll also assume you can drive with seven pistons (or five in Europe) and move ahead. Anyway, don't do it on bikes.

Meet Mr. Piston... Hi, Mr. Piston. Ouch
[youtube]http://www.youtube.com/watch?v=K2GLrZST ... re=related[/youtube]

Comfort comes to mind, but hey, you can also assume infinitely rigid driver butts... (actually, some of them seem pretty rigid)

As you are asking a lot of questions I would like to make just one: how come that you find irrelevant the fact that a car which complies with your propositions cannot move because infinitely rigid tyres (only way to have no suspension at all) cannot give you any grip?

Infinite means "infinite", it doesn't mean "a lot".

No suspension at all is like saying zero suspension and "zero" means "nothing", it doesn't mean "a little bit".

That's why I have to mention that hardingfv's "one molecule thick tyres" would suffer severe degradation through the race: they would go from one molecule thick to zero molecule thick in zero seconds, as you also cannot have grip without spending some rubber, by definition of what grip is.

As I've noted, in an "infinite" car (per your propositions) any road irregularity would cause infinite change in load on the engine, so even in a perfectly smooth track I would advise not to race against not "infinitely bound by rules" competitors.

For example, if I were in front of you during a race, I would throw all my discarded visor covers on your path, causing your engine to explode... by the tiny jump your car would make passing over the visor.

The inevitable conclusion: no suspension would mean infinite change load on engine when passing over anything your adversaries could throw on your way, and, thus, infinite exposure to competitor's tricks (remember the golden rule of strategy: "the others are also playing").

As the load change on the engine of a car passing over one of my discarded visors would be also infinite, and I am assuming an engine made of infinitely rigid materials (otherwise it would flex and damp the car movements, as the Renault damper of years ago) you would have an infinite force acting on an infinitely resistant engine, per your propositions.

The mathematical collapse brought into being by an infinite force pushing on an infinitely hard object would cause an infinite explosion that would devastate the whole Universe.

That would look bad on FIA.

Perhaps that's how the Big Bang came into being: an infinitely naive engineer, like me, built an infinitely rigid car with no suspension, like hardingfv's proposes, and then he started it all.

So, there you have a reason to have a suspension: to avoid the end of the Universe as we know it. Also you can conclude that God is a mechanical engineer. Omnipotent but not omniscient.

Finally, it is my duty as a responsible scientist to recommend you that if you can actually devise a car with no suspension at all you should keep it out of the hands of those people at the Pentagon, taking in account the risk of huge explosions like Big Bang and their possible effects on humankind's ability to survive.

Kudos on your persistence, hardingfv. I think this thread (to survive a bit) needs a few numbers in any kind of first (or zeroth) degree approximation... and I really like this thread.

I hope DaveW learns something from this post: "if you cannot defeat them, join them".

[Lurk]

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

Yes it's foam: nothing more than a very soft tyre with a wide usage window.

My point is that you cannot say that cars with suspension are always far better than cars without. You have to take some others elements and tyre is the first.

If you have no suspension, as a vehicle designer or tuning engineer, you have no way of tuning handling or balance

Depends of what you called suspension. In the scale car I posted, you can change camber and toe. You can also change caster on some.
If in your point of view, they are part of the "suspension system" (even if the car is not suspended) then we agree.

A winning car without suspension is possible, it only depends of the context: track, tyre, weather).
A winning car without any possibility to change its setup (suspended or not)... Well, you can but you must build one car per track, driver and weather condition. Very expensive, and you also need to come with several cars per driver each event, because you cannot guess exactly weather and driver's preferment.

[Ciro Pabón]

Lurk, I've built some RC cars. Those cars don't need so much damper (if at all) because the frequencies of the suspension are very high and rubber hysteresis is enough to damp them. Besides, you spend most of your time sliding, don't you? Finally, the jumps an RC car makes over obstacles (there is a reason why you build planks), if I were scaled to its size and if I were actually driving a tiny steering wheel inside the tiny cockpit, would probably crush my spine. I think that's why ants don't race. Wait... we have Massa. Erm. I mean, that's why ants don't race without a suspension.

[Lurk]

Maybe it would be better for Massa that they ran without. Damn Hungaroring...


Joke apart, road rc cars generally don't jump during race (except when they crashed). They can but off-road are better for this usage

On the first part, I do not see where it comes against what I said. It depends of the tyre. Of course I don't think it exists 1:1 rubber tyre that behave like the 1:8 foam one. So we cannot test.
I just disagree on the generalization did by Jersey Tom because I think he omit the most important parameter which is tyre. I know I'm a little playing evil's advocate but I think it was important to remind that the first thing you must look at before build your car is tyre.


On the other end, I ran rc car on the smoothest track with the most rigide tyre you can imagine: ice with homemade snow tyres (old rain tyre with stud).
Some tries to race with 4x4 road cars and they struggle because of their stiffness. Winner was an offroad with very smooth suspension setup. It was the only way to get all the power on the track and to turn properly.
My car was a kind of intermediate: road oriented but not a true road race car so I can go with smoother setup. I wasn't so bad until my central axe bent and broke my tank...(it was a 4x4 car which I crashed 2 weeks before and it bent the axe, my dad build me another at his job but obviously it wasn't stiff enough)

[hardingfv32]

Ciro Pabón

I can agree with your concerns.

So I will amend my original premise to specify the use of tires that has at least 100 times the stiffness and dampening control of the current F1 tire. These are valid (and attainable) criteria if using a dead smooth track.

I'm try to reduce the normal complications of a pneumatic tire.

Brian

[DaveW]

I hope DaveW learns something from this post: "if you cannot defeat them, join them".

I learn something from most posts, Ciro.

As it happens, I have actually tested an F1 vehicle with rigid links replacing the normal springs & dampers, & dynamic absorbers (complete with depleted uranium masses) attached to each of the four uprights. The venue was Donington Park with Nigel Mansell driving (being the victim). He circulated surprising quickly, but complained bitterly of terminal over-steer & large oscillatory steering loads. All tyres were destroyed in a very few laps. The test was not repeated ..... Now, what will I be joining & how do I join?

[hardingfv32]

May we assume that the tires were not sized or designed for this type of suspension and that the correct tires and aero features would have brought balance back to the car?

What was the actual goal of the test? Were the designers not expecting most of the negative outcomes developed during this test?

Brian

[WilO]

Dave,

The use of depleted uranium was very likely the cause of the ill-handling car; I'm a little surprised at the choice of material....(Whatever you do Dave, don't join them).

Brian, please re-read your last post.

Wil

[DaveW]

... The use of depleted uranium was very likely the cause of the ill-handling car; I'm a little surprised at the choice of material....(Whatever you do Dave, don't join them).

Actually, depleted uranium was readily available at the time (unlike Tungsten & its alloys). Also it was easily machined & had few problems (in my view), provided that it was handled with reasonable care.

May we assume that the tires were not sized or designed for this type of suspension and that the correct tires and aero features would have brought balance back to the car?

What was the actual goal of the test? Were the designers not expecting most of the negative outcomes developed during this test?

You may (assume so).... The goal of the test was to see if there was a simple way of gaining control over the ride height of a skirted tunnel vehicle without resorting to twin chassis, active suspension, etc. (at the time ultra stiff springs & matching dampers & tyres simply did not exist).

Incidentally, I posted earlier (slightly tongue in cheek) that Lurk might have suggested a solution to your problem, provided that RC foam tyres could be scaled. I'm reasonably sure that they could be scaled in most respects, but tyre damping coefficients would, I think, be very temperature-dependent, & an efficient way of dissipating thermal energy from the tyres would be an imperative. I think both would prove to be be intractable problems, although I recall somebody claiming to have found a solution....