Lotus E21 Renault

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ringo
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Joined: 29 Mar 2009, 10:57

Re: Lotus E21 Renault

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Crucial_Xtreme wrote:
tony77g wrote:
ringo wrote:
"Pressure builds up and increasing the spring effect" just sounds categorically wrong. We know something that is in-compressible, like hydraulic fluid, cannot behave like a spring. This article is just gluttonously careless.
It's a nice feast for the eyes yes.
In landing gears of the aircraft operation is the same, and the hydraulic fluid and air like a spring
+1
That sentence is not proper english, why not unclouded it and say exactly what is intended?
Fear that it might be incorrect?

Let's get things straight here. Something in compressible cannot behave like a spring. Agree?

The only thing that can behave like a spring is the air spring, due to idea gas laws. This is like an accumulator.

Now I feel the weakness in admitting that the air spring is the spring and not the hydraulic fluid, is that we have to locate the air spring on the car. Some don't want to do this because they know it's going to pretty hard to fit 4 of them on an F1 car. haha.

So we have this distracting theory that oil and a few checks valves a spring makes, which is disingenuous.
So i'd ask Tony to clarrify, what on the landing gear is the spring; the fluid or the air.

Let's do a simple exercise, firstly what's a usual corner spring rate on an F1 car?
For Sure!!


tony77g
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Re: Lotus E21 Renault

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ringo wrote:
That sentence is not proper english, why not unclouded it and say exactly what is intended?
Fear that it might be incorrect?

Let's get things straight here. Something in compressible cannot behave like a spring. Agree?

The only thing that can behave like a spring is the air spring, due to idea gas laws. This is like an accumulator.

Now I feel the weakness in admitting that the air spring is the spring and not the hydraulic fluid, is that we have to locate the air spring on the car. Some don't want to do this because they know it's going to pretty hard to fit 4 of them on an F1 car. haha.

So we have this distracting theory that oil and a few checks valves a spring makes, which is disingenuous.
So i'd ask Tony to clarrify, what on the landing gear is the spring; the fluid or the air.

Let's do a simple exercise, firstly what's a usual corner spring rate on an F1 car?

The oil is said incompressible, but in reality a small portion is compressible.
Its "spring" is made through internal paths that the oil must accomplish within the jack. Must pass through very small orifices, and also there is however also a part of the air. This air is compressible.

sorry for my english...
Last edited by Richard on 30 Apr 2013, 14:43, edited 1 time in total.
Reason: Fixed quote tags

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Pierce89
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Joined: 21 Oct 2009, 18:38

Re: Lotus E21 Renault

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tony77g wrote:
ringo wrote:
That sentence is not proper english, why not unclouded it and say exactly what is intended?
Fear that it might be incorrect?

Let's get things straight here. Something in compressible cannot behave like a spring. Agree?

The only thing that can behave like a spring is the air spring, due to idea gas laws. This is like an accumulator.

Now I feel the weakness in admitting that the air spring is the spring and not the hydraulic fluid, is that we have to locate the air spring on the car. Some don't want to do this because they know it's going to pretty hard to fit 4 of them on an F1 car. haha.

So we have this distracting theory that oil and a few checks valves a spring makes, which is disingenuous.
So i'd ask Tony to clarrify, what on the landing gear is the spring; the fluid or the air.

Let's do a simple exercise, firstly what's a usual corner spring rate on an F1 car?

The oil is said incompressible,
Its "spring" is made through internal paths that the oil must accomplish within the jack. Must pass through very small orifices,
This forms a damper rather than a spring.
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CBeck113
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Joined: 17 Feb 2013, 19:43

Re: Lotus E21 Renault

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Pierce89 wrote:
tony77g wrote:
ringo wrote:
That sentence is not proper english, why not unclouded it and say exactly what is intended?
Fear that it might be incorrect?

Let's get things straight here. Something in compressible cannot behave like a spring. Agree?

The only thing that can behave like a spring is the air spring, due to idea gas laws. This is like an accumulator.

Now I feel the weakness in admitting that the air spring is the spring and not the hydraulic fluid, is that we have to locate the air spring on the car. Some don't want to do this because they know it's going to pretty hard to fit 4 of them on an F1 car. haha.

So we have this distracting theory that oil and a few checks valves a spring makes, which is disingenuous.
So i'd ask Tony to clarrify, what on the landing gear is the spring; the fluid or the air.

Let's do a simple exercise, firstly what's a usual corner spring rate on an F1 car?

The oil is said incompressible,
Its "spring" is made through internal paths that the oil must accomplish within the jack. Must pass through very small orifices,
This forms a damper rather than a spring.
Exactly - you need an accumulator or a return circuit to get the oil back into the chamber for it to function like a spring - the actual spring function is not performed by the oil, but by elements influenced by the pressure changes in the oil. So you either use the direct way with an accumulator, in which the pressurized air works as the spring, or you implement a time difference in which the oil exits and then returns to the hydraulic cylinder.
The first solution is easier, but maybe less flexible (one pressure setting), the second would be a bi**h to get right, due to the numerous factors which need to be controlled (i.e. orifice dimensions, setting delta T through hose lengths, valve opening & closing behavior etc.). Not to mention the viscous properties of the oil itself (could be controlled by heating the oil to the engine temp, but locally pressing the oil through an orifice causes a temperature rise & degregation, changing its characteristics).
I understand why they need so long to "get it right", but I also see the reward being worth the effort. Guess that's why they earn the big $$$ :)
“Strange women lying in ponds distributing swords is no basis for a system of government. Supreme executive power derives from a mandate from the masses, not from some farcical aquatic ceremony!” Monty Python and the Holy Grail

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PlatinumZealot
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Joined: 12 Jun 2008, 03:45

Re: Lotus E21 Renault

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Hydraulics do not a good spring make. Do the maths.
Might as well u use a real spring than hydraulics, because you are gonna need humungous housings to contain a hydraulic spring. Use your God given brains people.
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miguelalvesreis
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Joined: 12 May 2012, 13:38

Re: Lotus E21 Renault

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n smikle wrote:Hydraulics do not a good spring make. Do the maths.
Might as well u use a real spring than hydraulics, because you are gonna need humungous housings to contain a hydraulic spring. Use your God given brains people.
you better tell Andre Citroën about that!

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ringo
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Joined: 29 Mar 2009, 10:57

Re: Lotus E21 Renault

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I did some basic calculations with an air spring bottle. I realized that the bigger the bottle the lower the air pressure needed.
The motion ratio of the suspension to the hydraulic strut, or whatever it's called also has an effect.
for a system with around air at 250psi, you may be looking at a 3 inch diameter bottle. If it is to support 2000lb of downforce and the car's weight. The length of the bottle, which affects the volume has an effect of the air pressure changes when the wheel moves up and down. A 2 inch bottle would mean the pressure would have to almost double to 500+ psi.

The bigger the bottle, the smaller the pressure changes, which makes for less energy losses.
The biggest problem with air springs is the reversibility/energy losses. Infact there is a lot of hysteresis in a hydrualic system considering everything.

So if we are to have 4 of these air spring bottles, then we must find them on the car. Unless the FRIC is still much simplified and there is one bottle, an equivalent to a roll bar connecting front and rear.
For Sure!!

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AnthonyG
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Joined: 03 Mar 2012, 13:16

Re: Lotus E21 Renault

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ringo wrote:I did some basic calculations with an air spring bottle. I realized that the bigger the bottle the lower the air pressure needed.
The motion ratio of the suspension to the hydraulic strut, or whatever it's called also has an effect.
for a system with around air at 250psi, you may be looking at a 3 inch diameter bottle. If it is to support 2000lb of downforce and the car's weight. The length of the bottle, which affects the volume has an effect of the air pressure changes when the wheel moves up and down. A 2 inch bottle would mean the pressure would have to almost double to 500+ psi.

The bigger the bottle, the smaller the pressure changes, which makes for less energy losses.
The biggest problem with air springs is the reversibility/energy losses. Infact there is a lot of hysteresis in a hydrualic system considering everything.

So if we are to have 4 of these air spring bottles, then we must find them on the car. Unless the FRIC is still much simplified and there is one bottle, an equivalent to a roll bar connecting front and rear.
Are the obliged to use air by the rules, or can they use another gas?
Thank you really doesn't really describe enough what I feel. - Vettel

kilcoo316
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Joined: 09 Mar 2005, 16:45
Location: Kilcoo, Ireland

Re: Lotus E21 Renault

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ringo wrote:Hydraulic fluid cannot behave like a spring. And i'm seeing that in this article.
'course it can.


You are assuming it is mounted in rigid pipework that doesn't expand or contract with pressure.


If you have a reservoir with pressure diaphragm, you control the volume of the system. If you can do that, you can make a hydraulic "spring".


You are right in that the fluid itself doesn't provide the "spring" like properties, but that doesn't mean the system cannot. :)

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abw
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Joined: 03 Mar 2013, 15:03
Location: USA

Re: Lotus E21 Renault

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kilcoo316 wrote:
ringo wrote:Hydraulic fluid cannot behave like a spring. And i'm seeing that in this article.
'course it can.


You are assuming it is mounted in rigid pipework that doesn't expand or contract with pressure.


If you have a reservoir with pressure diaphragm, you control the volume of the system. If you can do that, you can make a hydraulic "spring".


You are right in that the fluid itself doesn't provide the "spring" like properties, but that doesn't mean the system cannot. :)
This is interesting. Hydraulic fluid in a "springy" bladder of some sort that provides the compressibility. I doubt that is how anybody makes this work, but it is still interesting. More likely the system involves (compressible, predictable) air-on-one-side and (incompressible, predictable) fluid-on-the-other side pistons. I think that is what Autosport is awkwardly trying to say in the article above.

I'm definitely no F1 engineer. But I can easily appreciate the simplistic concept of linking front/back/left/right with various hydraulic/air gizmos to control ... and here is the key point ... to control low-frequency stuff: coarse-scale heave, roll, etc. Left side of the car compressing in a turn? Use that compressive force via hydraulics to alter the right-side. Duh. Great idea. But when it comes to high-frequency stuff like running over curbs, I (again, not an F1 engineer) would NOT want to rely on slow-ass hydraulic linkages to keep the suspension stable. I would try to tune a hydridized system, where mechanical springs/torsion bars etc. handle the high-frequency bumps and jolts at each wheel independently, but the low-frequency stuff like roll during turning is handled by more sluggish hydraulic linkages.

But (third disclaimer!) I'm no F1 engineer. This is just hunch-level speculation. Ask me about Inconel and I'll have an informed opinion.


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ringo
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Joined: 29 Mar 2009, 10:57

Re: Lotus E21 Renault

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kilcoo316 wrote:
ringo wrote:Hydraulic fluid cannot behave like a spring. And i'm seeing that in this article.
'course it can.


You are assuming it is mounted in rigid pipework that doesn't expand or contract with pressure.


If you have a reservoir with pressure diaphragm, you control the volume of the system. If you can do that, you can make a hydraulic "spring".


You are right in that the fluid itself doesn't provide the "spring" like properties, but that doesn't mean the system cannot. :)

IF the fluid doesn't provide the spring like properties then it's simply not a spring, something else in the system is, a rubber enclosure or whatever else it is you are considering. Hydraulic fluid is used to transmit force, and that's why it's incompressibility is valued. All damper technology is aimed to reduce air bubbles and cavitation, the whole aim is to make the fluid as ideally incompressible as possible.
And judging by the spring rates used in F1 there is nothing in the system that would give a sane spring rate for a f1 car other than an air spring. The natural frequency of a body of hydraulic oil is too high. The article is obviously not correct in that aspect, no point in trying to force it to be logical. There are definitely some inaccuracies.

It is probably feeding off the notion that damper is considered a "dynamic spring". Springs generate force from displacement while a damper generates force from velocity.
Velocity is the differential of displacement (rate of change of displacement, which is a dynamic property) hence the naming of a damper as a "dynamic" spring. It has momentary springing effects as speed is imparted to it, but most crucially it has no steady state spring rate. Once it stops moving there's no force. Hence it cannot be considered a spring. A damper dissipates energy without returning it, hence why when it stops moving there's no return motion. A spring will attempt to return the energy.

You cannot run this FRIC system with no air springs or no mechanical springs IMO. It's just a ridiculous idea that has be taken out of context and misused.
We should probably focus on finding the air springs on the E21 and also the control valve or manifold for the hydraulic suspension.
For Sure!!

aral
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Joined: 03 Apr 2010, 22:49

Re: Lotus E21 Renault

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kilcoo316 wrote:
ringo wrote:Hydraulic fluid cannot behave like a spring. And i'm seeing that in this article.
'course it can.


You are assuming it is mounted in rigid pipework that doesn't expand or contract with pressure.


If you have a reservoir with pressure diaphragm, you control the volume of the system. If you can do that, you can make a hydraulic "spring".


You are right in that the fluid itself doesn't provide the "spring" like properties, but that doesn't mean the system cannot. :)
Hydraulic fluid per se, cannot compress, so therefore there just cannot be any spring in its use. Imagine, if hydraulic fluid could compress or spring, then we would have no JCBs etc or any other machinery using hp oil. Yes, the ancilliaries could be used to provide some give, but the oil itself, CANNOT provide any springing.

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Sebp
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Re: Lotus E21 Renault

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gilgen wrote:Hydraulic fluid per se, cannot compress, so therefore there just cannot be any spring in its use. Imagine, if hydraulic fluid could compress or spring, then we would have no JCBs etc or any other machinery using hp oil. Yes, the ancilliaries could be used to provide some give, but the oil itself, CANNOT provide any springing.
It's not the fluid that is being compressed.
kilcoo316 wrote:If you have a reservoir with pressure diaphragm, you control the volume of the system. If you can do that, you can make a hydraulic "spring".
Have a look at this fine arcticle by scarbs:

http://scarbsf1.com/blog1/2011/11/29/lo ... d-inerter/
scarbs wrote:With Mercury having a high coefficient of thermal expansion, the patent suggests using a relief valve emptying into another chamber is used to ensure the system has a constant volume of fluid.
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