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islampharm
Starting Member

Egypt
3 Posts

Posted - 02/20/2011 :  10:07:42  Show Profile  Reply with Quote
Hi Everyone,
I was thinking alot about multiplication of the human force to increase the vehicle speed to be close to the ordinary cars.i am thinking in hydraulics as driving force to multiply my pedal force.i searched the internet for this kind of application but i didn't find anything....

is it applicable to use hydraulic drive to increase speed of the bike with suitable gear ratios...with or without chains

Larry Lem
human power expert

South Sandwich Islands
2300 Posts

Posted - 02/20/2011 :  10:45:17  Show Profile  Reply with Quote
Perhaps rephrase your goal, adding details. One cannot simply multiply their driving force (I think you were referring to power.) That would defy one the first law of thermodynamics. You can multiply your force through levers, but torque remains constant (or decreases through mechanical losses).

Are you thinking about energy storage so one can release more energy at a given time to propel a vehicle up to the speeds of ordinary cars? A hydraulic/pneumatic reservoir? If energy storage, you could also sit at home, drive a generator to charge a battery, and then ride a bike with an electric motor. I don't know that there is anything special about hydraulics.

I recall that SAE or Johnson Controls ??? in the USA had a collegiate contest for use of hydraulics in human powered vehicles 5-10 years ago. I could not find anything in a quick search. I am sure someone else here will remember more and can post a link.

There could be no direct drive mechanism between the rider and the wheels; all power had to be converted through hydraulics. But these vehicles did not travel any faster than normal bicycles as the limiting factor in power output is always the rider (with no energy storage).

Larry Lem

Edited by - Larry Lem on 02/20/2011 10:46:52
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islampharm
Starting Member

Egypt
3 Posts

Posted - 02/20/2011 :  11:30:18  Show Profile  Reply with Quote
you are right Larry i mean force not power ...hydraulics multiply the force using fluid dynamics ( i think)
you can see it in car brakes small amount of force generates enough power to stop a car...
http://en.wikipedia.org/wiki/Hydraulic_machinery
i saw some videos on youtube about chainless bikes but my problem isn't in chain but how can use it to generate more speed..i read something about Hydristor and using pumps and motors but i can not see what i'm looking to..
i read about using accumulator to use brake power then reproduce the power again.it's wonderful idea but i'm still want to find the answer of hydraulic as driving force
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teubner
recumbent guru

785 Posts

Posted - 02/20/2011 :  11:40:03  Show Profile  Reply with Quote
I did a Google for "hydraulic bicycle" and got several hits.
Also: http://en.wikipedia.org/wiki/Hydraulic_bicycle

Larry is correct: you cannot increase the power through hydraulics.
Power is torque x RPM. You can only lose throught he driveline, never end up with more.
Storing braking energy is another issue, and there may be some recoverable energy there, if you use your brakes a lot.
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warren
human power expert

USA
4898 Posts

Posted - 02/20/2011 :  12:27:50  Show Profile  Visit warren's Homepage  Reply with Quote
This has been tried several times in the past, and while it is possible to use pedal force to drive hydraulic pumps, it is not practical for bicycles use due to the high friction losses inherent in hydraulic systems.

There was a guy working on a hydraulic transmission for a bicycle several years back. You might find it in the old ihpva HPV list archives (if those still exist). The problem that he could never resolve was that you would have to start pedaling to pressurize the system and it would take several pedal revolutions before the bike would start moving.

For driving other other hydraulic devices for lifting, etc it is certainly more practical.

-Warren.
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Larry Lem
human power expert

South Sandwich Islands
2300 Posts

Posted - 02/20/2011 :  18:33:14  Show Profile  Reply with Quote
Aha! Parker, not Johnson. The Parker Chainless Challenge.

Larry Lem
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Upright Mike
human power expert

USA
3463 Posts

Posted - 02/20/2011 :  19:02:18  Show Profile  Visit Upright Mike's Homepage  Reply with Quote
At the last winter meeting for the Michigan human powered vehicle group, a professor from Western Michigan University gave an excellent presentation on WMU's designs for the Parker Chainless Challenge. I'd suggest getting in touch with them for more info, or ask Google!
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W Hilgenberg
recumbent enthusiast

USA
285 Posts

Posted - 02/20/2011 :  19:33:25  Show Profile  Reply with Quote
We have a hydraulic bike laying around here at Cal Poly. Not sure what happened to it and if it is still being used (they "borrowed" one of the HPV teams Rohloff hubs) but it is still there. The bike itself with all the components on it weighs about 50 lbs. And that's a normal bike. Aside from that there was never a really good working way of getting the power to the wheel. The efficiency was just horrible. All-in-all it isn't too pleasant of a bike to ride. Kind of like riding in sand most of the time. Smooth slick sand but sand nonetheless. Just saps your power.
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islampharm
Starting Member

Egypt
3 Posts

Posted - 02/21/2011 :  03:16:08  Show Profile  Reply with Quote
I saw a video on youtube and i can see there is kind of power loss or delay to transfere power to wheels
http://www.youtube.com/watch?v=zeLJwHZdyow
but in 2008 parker's competition they made a bike reached 40mph speed
http://ceng.calpoly.edu/news/cal-poly-senior-project-wins-unusual-bike-design-a/
i can see it's still not applicable but the question here..is why?




Edited by - islampharm on 02/21/2011 03:19:22
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purplepeopledesign
recumbent guru

Canada
585 Posts

Posted - 02/21/2011 :  11:42:18  Show Profile  Reply with Quote
quote:
Originally posted by islampharm

i can see it's still not applicable but the question here..is why?


Efficiency is 95% of the race when the power source is capable of only 500 watts continuous averaged output (or less). But since you believe it is possible to make a competition hydraulic transmission, then build it and maybe you will make believers out of the rest of us. Until then, I will remain more than skeptical.

:)ensen.

Those who claim to be making history are often the same ones repeating it.

Video of my trike
http://www.youtube.com/watch?v=MdSLRD_2vzc
Photos of my trike
http://www.flickr.com/photos/purplepeople/
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