mclaren style hydraulic stabilizer bar?

[Xusia]

In static form, it should be an improvement over a traditional anti-sway bar. Where it really get awesome is when coupled with an electronic control system. The adjustability - as well as the potential for pre-action - far exceeds what any anti-sway bar is capable of.

[BrandonDrums]

I think it would actually be quite cheap to build a basic setup like this with the right tools. If someone were to buy some cheap ac delco oil filled shocks, had an air compressor and a tap and die set it could be done. However, as a few pointed out, the pressure spikes would probably cause the system to fail quite quick unless there were flow restriction valves of some sort that would seal if the flow exceeded a certain threshold.

This is where I don't know of the device nor the setting to achieve this but I can think of how one might work using a simple ball and spring valve in reverse.

As to the benefits, there would be lots of handling and ride quality improvements. Handling improvements because there would be more instant and dynamic anti-roll and anti -dive abilities. More handling increases due to having a more optimal and consistent spring-rate for each wheel. With this, only the strut is fighting roll vs. a traditional anti-roll bar which is essentially a torsen bar spring which makes bump and roll scenarios crazy as the different springs work together and against eachother to net all sorts of different effective spring rates through a roll.

Also, you get a much better ride, because you can run lower spring rates while still getting the same flat cornering from a stiffer setup.

Newer, magnetic systems attempt to do exactly what this system does but without all the heavy lines and with the added benefit of a computer. However, I think the hydraulic system can react quicker to more bump scenarios as it's hard to program a computer controlled unit to react to all varying degrees and combinations of bump and roll inputs. Juice flowing just happens so much quicker and seems really f'n cool.

Wish I had time and money to try this out! I love having cheap yet clever things outperform the rich guy's gadgets. I guess that's why I'm an FFR fan!

[Join]

Good evening folks..

Trying to do some math here and searching the web for possible candidates.

I found a possible match: 20mm rod/40mm bore and 200mm travel/14mPa max pressure rating.

That means 2030psi, and at that pressure one cylinder can hold 2966lb or 1345kg.

That means 9,42mm2 area at a 200mm stroke it will push 0,188litres? So, 1,82dl(6,15fl.oz?) of fluid will travel from one side to the other. Not so much at all. With a 10mm ID hose that means 60cm travel in one movement?

Anyone with skills to tell how much friction that will be in 0,5 second?(Time unit for instant) Head conversion tell me that 60cm in 0,5second is 1,2m/s.

Internet calculator result:

Inputs
Pressure at A (absolute): 14mPa
Average fluid velocity in pipe, V: 1,2m/s
Pipe diameter, D: 1,0cm
Pipe relative roughness, e/D: 0
Pipe length from A to B, L: 2m
Elevation gain from A to B, Dz:
Fluid density, r: 869kg/m3
Fluid viscosity (dynamic), m: 16cP
Answers
Reynolds Number, R: 652
Friction Factor, f: 0.0982
Pressure at B: 0.248 psi
Pressure Drop: 1.78 psi
Volume Flowrate: 0.0942 l/s
Mass Flowrate: 0.0819 kg/s

How does that look for a result? In my eyes it doesn't look too bad, but I am not enough into this matter to tell wether is it a reasoneable result or not. Or If there is any mistakes throughout my calculations.

Does it look like a reasoneable size cylinder to work with 40mm dia. and 200mm travel? Remember that when the 818 rest on the wheels the cylinder will not be on one end of it's travel.(Not according to my "plan".)


EDIT:

If the flow move in 0.1sec it should equal 6m/s flow in the lines. Internet calculator result will then be:

Answers
Reynolds Number, R: 3260
Friction Factor, f: 0.0424
Pressure at B: 2010 psi
Pressure Drop: 19.3 psi
Volume Flowrate: 0.471 l/s
Mass Flowrate: 0.410 kg/s

[FinishlineWRX]

Remember the cylinder has to be double action or something to keep the piston area equal on both sides of the motion.

The numbers seem like they work from just looking at them.

This still didn't calculate the pressure spike. unless thats what the pressure B is referring to..

Using your 6m/s flow rate = 19.6 ft/s = V = change in velocity
Density = 869kg/m3 = 54lb/ft3 = rho
C = speed of sound in fluids = √k/rho = 4977ft/s
gc = 32.2
Pressure Spike = ∆P = rhoC∆V/gc

∆P = (54lb/ft3 * 4977ft/s * 19.6ft/s)/32.2
∆P = 163591 lb/ft2 /144in2
∆P = 1136psi spike + Static pressure This is just some rough numbers

[Join]

But. .. Thinking it a little over the effective piston area should be doubled because fluid don't compress or stretch, so there will be equal force pulling and pushing at the same time? That should effectively double force capacity at given pressure? That means that to maintain the needed force the pressure can be reduced to 1015psi for the same result, and there will be a lot of headroom for spikes?

[NonProfit]

However, as a few pointed out, the pressure spikes would probably cause the system to fail quite quick unless there were flow restriction valves of some sort that would seal if the flow exceeded a certain threshold.

OK, I have virtually no expertise in this area, so take this with a grain of salt, but what about a 5th cylinder which would act as a reservoir to prevent blowout? This would require more pressure to compress than the other four. Under normal driving conditions it would remain fully extended. In the event of a spike in pressure the cylinder would compress, reduce system pressure, and prevent failure.

[Benji]

Question: this system replaces the traditional roll bar. Is this to save weight? Or does a hydraulic system have performance advantages over a roll bar?

Roll bars are a fixed stiffness, to adjust them you need to replace them in most instances. This system could almost be considered 'infinitely variable' and 'automatically adjusting'.

That's simplifying a bit too much perhaps but that is the basic principle of it. As mentioned above, top gear found that it rides like a Bentley and handles like a 458.

Interesting that kinetic systems were band from WRC and Dakar in 2006, usually this means it's very very good

[FinishlineWRX]

But. .. Thinking it a little over the effective piston area should be doubled because fluid don't compress or stretch, so there will be equal force pulling and pushing at the same time? That should effectively double force capacity at given pressure? That means that to maintain the needed force the pressure can be reduced to 1015psi for the same result, and there will be a lot of headroom for spikes?

Yeah, your probably right there. Its to late to think right now. I'm not used to driving a cylinder with another cylinder. With a pump the travel speeds will be different depending on the piston area.
I know for all intensive purposes fluids are incompressible, but not sure about the stretching part. Once the pressure reduces below the saturated vapor pressure the fluid will form bubbles...cavitation.

[Join]

OK, I have virtually no expertise in this area, so take this with a grain of salt, but what about a 5th cylinder which would act as a reservoir to prevent blowout? This would require more pressure to compress than the other four. Under normal driving conditions it would remain fully extended. In the event of a spike in pressure the cylinder would compress, reduce system pressure, and prevent failure.

There are 4 seperate volumes that needs to be seperated. So one 5th cylinder will not do the trick.
Remember that the accumulators will work as a shock absorber as well. I am trying to calculate worst case spike load to figure out what psi rating the system need.

[bromikl]

Banned = very very good: HAhhaahahah!!

Join, any estimate on the cost for the components?
In theory, hydraulic stabilization works. Earlier versions performed well. Current versions, spectacularly well.
Obviously we can't rip apart a McLaren for its suspension. At some point, someone needs to build a prototype and test it. Does anyone want to offer a test bed?

[Join]

Join, any estimate on the cost for the components?
In theory, hydraulic stabilization works. Earlier versions performed well. Current versions, spectacularly well.
Obviously we can't rip apart a McLaren for its suspension. At some point, someone needs to build a prototype and test it. Does anyone want to offer a test bed?

Hi!

No idea on the 14mpa candidate yet, but the 250psi cylinders was just shy of $150 a piece ordering 4pcs.

I wanted to know what to ask for before getting a quote on the next one.

This is something I'd love to try out, but it will be 2years +. I tend to stick to my plans.. Hope it is not too far off for you!

Ideally the plan is so far on its road to completion that I can custom order welded plates/bars for me to attatch mounts to the frame direct from F5. Hopefully that can rule any welding out on my part.

If anyone got the scaled drawing on the frame it is easier to make a plan to work with.

Anyone?

[FinishlineWRX]

Hi!

No idea on the 14mpa candidate yet, but the 250psi cylinders was just shy of $150 a piece ordering 4pcs.

I wanted to know what to ask for before getting a quote on the next one.

This is something I'd love to try out, but it will be 2years +. I tend to stick to my plans.. Hope it is not too far off for you!

Ideally the plan is so far on its road to completion that I can custom order welded plates/bars for me to attatch mounts to the frame direct from F5. Hopefully that can rule any welding out on my part.

If anyone got the scaled drawing on the frame it is easier to make a plan to work with.

Anyone?

That sounds about right for the my build schedule. Hope to get the kit mid 2013 depending on release. Take my time building. And seeing what I can modify....

Finding the components and about how much weight its going to add is going to be important to me.

[bromikl]

We could use any vehicle as a test bed. A mid 90's Impreza would work fine. A tube-frame car would be even better.