Why no Hydraulic Drive Systems on roadcars?

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mike
mike
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Joined: 10 Jan 2006, 13:55
Location: Australia, Melbourne

Re: Why no Hydraulic Drive Systems on roadcars?

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well Carlos its more about the trend of f1 technology is the past 10 years.
in the pass 10 years the FIA restrict and control nearly all mechanical develop innovation what so ever, so all the F1 teams have to turn to aero for development, hence this forum is mostly about picture-drive threads about aerodynamic devices.
truth be told i do enjoy mechanical threads more like the "mass-damper", zeroshift KERS etc.

i read about a thing called the "snake skin" coating it essentially is design to reduce internal friction of to valves in a engine and i can see it working in tubes or lines on hydraulic systems. much like the concept for fish it reduce the drag on the fluids
http://www.sinusvalves.com/en-us/conten ... ubaru_sti/

Carlos
Carlos
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Joined: 02 Sep 2006, 19:43
Location: Canada

Re: Why no Hydraulic Drive Systems on roadcars?

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A hydraulic Drive system brings to mind another system we had discussed, this might interest you Conceptual. The compressed air drive car.
http://en.wikipedia.org/wiki/Air_car
Your right Mike. I watched the evolution of F1 in it's most innovative phase, the sixties on the the 70's into the 80's. Every few years the cars changed so radically they almost looked like alien space craft. Surface coatings are a cutting edge. Ciro mentioned self-healing surfaces in a thread. I was looking for amorphus materials yesterday and now I've found this which relates to the snakeskin coating. Thanks for the link. Very interesting. This may be of interest.
http://www.faqs.org/patents/app/20090011146

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

Re: Why no Hydraulic Drive Systems on roadcars?

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Professor wrote:Hydraulic systems do not work well in high speed applications, and for road cars they are quite heavy as a percentage of the total weight. They are useful on large, slow, stop and go vehicles like city busses and waste disposal trucks.
Indeed.

The latest (well, when I say latest - I'm talking 2005 onward) JCB 3CX and 4CX diggers have a lock-up "clutch" to remove the hydraulic element (torque converter) from the system to improve "high speed" performance.

Anyone who has drove one of these machines on the road will no doubt know exactly why hydraulic systems are not great for high speed work.


While a torque converter is not quite the same thing as suggested here, using fluid to transmit power is less efficient than direct mechanical linkages.

Conceptual
Conceptual
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Joined: 15 Nov 2007, 03:33

Re: Why no Hydraulic Drive Systems on roadcars?

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Ok, so I understand what is being said about the high speed situation, but I fail to understand how a hydraulic "cam-ring" motor put in place of the wheel bearing could not drive a car down the road...

Or even that setup on a racecar. There, you are almost NEVER come top a complete stop (other than pits) so is it a failure of hydraulics, or a failure of technology?

I personally think that it can be overcome, but obviously, that is my belief.

Can anyone give an example of a failed hydraulic drive car/racecar?

Thanks for all of the posts so far!

Carlos
Carlos
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Joined: 02 Sep 2006, 19:43
Location: Canada

Re: Why no Hydraulic Drive Systems on roadcars?

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Search Term 'hydraulic drive race car'
http://www.autobloggreen.com/2008/02/13 ... ve-braking
http://thekneeslider.com/archives/2008/ ... e-racecar/
http://thekneeslider.com/archives/2007/ ... otorcycle/
http://thekneeslider.com/archives/2008/ ... on-update/


The last link has a Youtube clip of a hydrostatic drive.

Is it just my browser that has Google or do all browsers come with a Googly Thingy? :D

xpensive
xpensive
214
Joined: 22 Nov 2008, 18:06
Location: Somewhere in Scandinavia

Re: Why no Hydraulic Drive Systems on roadcars?

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There is something else to consider regarding the "hydraulic shaft". When hydraulic power is defined as pressure times volumetric flow, to convey 200 kW (272 Hp), you would need a flow of 20 liters per second (320 gpm) even at a pressure of 10 MPa (1450 psi).
Typically, you don't wish to exceed 6 m/s in your flow-lines, why a 65 mm (2.5")ID hose or pipe is needed.
Heavy stuff.
"I spent most of my money on wine and women...I wasted the rest"

mike
mike
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Joined: 10 Jan 2006, 13:55
Location: Australia, Melbourne

Re: Why no Hydraulic Drive Systems on roadcars?

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indeed its heavy, but hydraulic shaft can use a 3:1 gear from the transmission to axle and a 1:3 gear at the other end, effectively reduce the weight by 2/3.

it will work similarly to a high voltage electrical transmission system, using high pressure to reduce the power loss.
if you also taken into account of advance coating systems it may allow fluids to pass through the pipe in much higher velocities

xpensive
xpensive
214
Joined: 22 Nov 2008, 18:06
Location: Somewhere in Scandinavia

Re: Why no Hydraulic Drive Systems on roadcars?

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True mike, but with the same anology as Electric power is Voltage times Current, to limit the hydraulic flow you will need to increase the pressure, or "Voltage".

But that said, if you are ok with using more than 1450 psi, you can obviously reduce flow and size of pipe accordingly.
"I spent most of my money on wine and women...I wasted the rest"

mike
mike
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Joined: 10 Jan 2006, 13:55
Location: Australia, Melbourne

Re: Why no Hydraulic Drive Systems on roadcars?

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i not an expert at hydraulics xpensive, but can you take a look at this for me
http://www.artemisip.com/index.htm

[youtube]http://www.youtube.com/watch?v=CJw5AvvxBqg[/youtube]

User avatar
Ciro Pabón
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Joined: 11 May 2005, 00:31

Re: Why no Hydraulic Drive Systems on roadcars?

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Wow.

Double the mpg in the urban cycle vs manual gearbox? Well, I certainly want one of these. Sad, for its future in racing, is the phrase "no gear changes". It would be a different kind of racing.
Ciro

mike
mike
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Joined: 10 Jan 2006, 13:55
Location: Australia, Melbourne

Re: Why no Hydraulic Drive Systems on roadcars?

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from my understanding it can be programed to have gears, but cvt for them has a higher efficiency, so it could be like, gears in race mode and cvt for urban driving
the hydraulic axle can also free up the space at the rear to build a longer diffuser

xpensive
xpensive
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Joined: 22 Nov 2008, 18:06
Location: Somewhere in Scandinavia

Re: Why no Hydraulic Drive Systems on roadcars?

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I find this most intersting, why I have done some domestic research and found out that Volvo has recently developed a new super-sized truck for lumber tonnage, where the vehicle has hydraulic-FWD at lower speeds!
Currently in real-life testing, why it seems difficult to get data.
"I spent most of my money on wine and women...I wasted the rest"

The FOZ
The FOZ
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Joined: 07 Feb 2008, 23:04
Location: Winterpeg, Canada

Re: Why no Hydraulic Drive Systems on roadcars?

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I have a lawn tractor with hydrostatic drive, if that counts :wink:

The number one reason that comes to mind is efficiency. Somehow, you have to spin a hydraulic pump, and the hydraulic fluid, in turn, spins turbines resulting in mechanical energy that can go to a gearbox of directly to the wheels. That is, in effect, a multi-stage system. Every time you convert energy from one form to another, you are losing some of it to friction, inefficiencies of the process, etc. No machine is 100% efficient. Even a 90% efficient electric motor, for example, spinning a hydraulic pump that is only 90% efficient, that is pushing it's energy to a 90% efficient turbine/hydraulic powered gearbox...90% of 90% of 90% is about 73% or so...each step in the energy chain lessens what you can get out of a system.


As far as dynamic range goes, there are a few problems, the viscosity of hydraulic fluid being a big one. Offhand, I seem to recall that very thick fluids aren't well suited to high pressure situations, and there are issues (lubrication?) with thin fluids, as well. Dynamic range implies the pressure being variable from relatively low to relatively high. However it's achieved, it will create a lot of heat in the fluid, inevitably, and whatever is creating that pressure won't exactly be sittin' cool, either. That heat is lost energy.

The advantage of hydraulics is you can use a relatively small, underpowered engine, and by mating it to the right pump, line size, and rams (or turbine and gerabox), you can push a major sized hydraulic ram, or produce a ton of torque...with nil horsepower and/or dynamic range.

Engineering types, please feel free to correct me as needed.

Giblet
Giblet
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Joined: 19 Mar 2007, 01:47
Location: Canada

Re: Why no Hydraulic Drive Systems on roadcars?

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My daily driver has a hydraulic drive. Slow as hell, but who would want to drive a vehicle quickly when you are operating it from 80 feet above?
Image

So you think you are a good driver?

Driving one of these you get to chuck everything away :)
Before I do anything I ask myself “Would an idiot do that?” And if the answer is yes, I do not do that thing. - Dwight Schrute

Giblet
Giblet
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Joined: 19 Mar 2007, 01:47
Location: Canada

Re: Why no Hydraulic Drive Systems on roadcars?

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I heart double posts.
Before I do anything I ask myself “Would an idiot do that?” And if the answer is yes, I do not do that thing. - Dwight Schrute