robertst
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 posted on 16/5/06 at 07:19 PM |
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a-level question (sorry)
am i right to think that when fitting the brake pipes i have to take special care of having each pipe exactly the same length as the other? it does
matter right? i mean, if one pipe going to the front left is only 50 cm and the one going on the front right is 75cm, the front left wheel should
brake harder than the other one right?
sorry, forgot my a-level physics.
Tom
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gary gsx
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| posted on 16/5/06 at 07:24 PM |
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They will be different lenths any way as master cylinder is on the right so pipe would be longer going to left, thats right or im going mad to 
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BKLOCO
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| posted on 16/5/06 at 07:24 PM |
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Wrong. Makes no appreciable difference.
Experience is what you get when you don't get what you want!!! 
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Howlor
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| posted on 16/5/06 at 07:30 PM |
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Pressure is the same in a hydraulic system throughout as the liquid cannot compress hence transmits the same force evenly.
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liam.mccaffrey
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| posted on 16/5/06 at 07:37 PM |
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ok so heres another quetion, it will make no appreciable difference if the pipes are different lengths so does this mean that hydraulic pressure can
be transmitted at infinite speed??
Build Blog
Build Photo Album
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donut
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| posted on 16/5/06 at 07:49 PM |
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What?? my brain hurts 
Andy
When I die, I want to go peacefully like my Grandfather did, in his sleep -- not screaming, like the passengers in his car.
http://www.flickr.com/photos/andywest1/
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andylancaster3000
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| posted on 16/5/06 at 07:55 PM |
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I suppose in theory yes. If all systems such as the pipes, the fluid and pistons worked exactly as they were supposed to.
However in the real world things are never perfect and therefore it will not be infinite. For example, You will never bleed all of the out of the
lines.
Andy
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Liam
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| posted on 16/5/06 at 08:02 PM |
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Yeah, the perfect hydraulic system is essentially a rigid mechanical connection, so should be as instantaneous as a solid linkage or [unstretchable]
cable.
But that's now making my brain hurt!! Theoretically a long rod or perfect hydraulic system could transmit information instantaneously, i.e.
faster than the speed of light??? Sounds like it would break laws of physics, but i guess it wouldn't cos that's silly... oh well.
Liam
[Edited on 16/5/06 by Liam]
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tom_loughlin
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| posted on 16/5/06 at 08:05 PM |
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Im not sure if im right in thinking, there are forces experienced by the fluid from the wall - skin friction. at the start of the brake line, say d=0,
only a tiny fraction of the fluid (i.e. that in direct contact with the hose is slowed), but as you progress down the line, where d is increasing, the
proportion of the free stream fluid is decreasing with respect to the fluid experiencing the skin friction. this is where the the ideal values differ
from the real values, and is about boundary layers.
I think
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JoelP
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| posted on 16/5/06 at 08:09 PM |
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neither energy, information or matter can exceed the speed of light. If you get a metal bar 2 miles long, when you whack one end the other end will
not move instantly, a ripple of compression will move (very fast) to the other end, but the speed of light will never be breached. The same as
hydraulic fluid, it doesnt noticably compress but in fact, it does fractionally.
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MikeR
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| posted on 16/5/06 at 08:15 PM |
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Ah, but as the speed of light isn't a constant and has been proved to vary over the surface of this planet, if you measure the speed of light in
a 'slow' place and whacked the metal bar somewhere else it could exceed the speed of light.
(ok, so this is mickey mouse physics as it wouldn't exceed the speed of light where you are)
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Macbeast
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| posted on 16/5/06 at 08:15 PM |
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You have to take account of reaction time, ie see speed camera -- duh--- brake
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MikeR
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| posted on 16/5/06 at 08:28 PM |
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or if you're like me.
See speed camera one week at night while on the opposite side of the road over taking a car then realise the reason the road suddenly gets lit up is
because its becoming a duel carriage way. Jump on the brakes to find out one caliper is sticking and the car is trying to turn left into the car
you're overtaking.....
"OH-MY-GOD"
7 days later think.....
"isn't there a speed camera around h"
[FLASH]
BRAKE SPEEDO? Whats it SAY BRA
[FLASH]
10 days later i found out exactly what my speedo said.
(this was a few years ago)
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BKLOCO
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| posted on 16/5/06 at 08:31 PM |
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I'm not getting into this one!!!
I feel a headache coming on
Just don't worry about it.
There's more important things in life.
Experience is what you get when you don't get what you want!!!
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JoelP
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| posted on 16/5/06 at 08:34 PM |
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quote:
Originally posted by MikeR
Ah, but as the speed of light isn't a constant and has been proved to vary over the surface of this planet, if you measure the speed of light in
a 'slow' place and whacked the metal bar somewhere else it could exceed the speed of light.
(ok, so this is mickey mouse physics as it wouldn't exceed the speed of light where you are)
true enough, but the real speed of light is that in free space 
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Liam
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| posted on 16/5/06 at 08:46 PM |
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quote:
Originally posted by JoelP
neither energy, information or matter can exceed the speed of light. If you get a metal bar 2 miles long, when you whack one end the other end will
not move instantly, a ripple of compression will move (very fast) to the other end, but the speed of light will never be breached. The same as
hydraulic fluid, it doesnt noticably compress but in fact, it does fractionally.
Guess you're right of course. Just that i was thinking more along the lines of a metal rod extending to about the sun. Pull on one end and
it'd take 8 minutes for the other end to move. Well yeah i guess it would. How interesting. (and that's ignoring pedantic details like
the fact i would struggle to overcome the billions of tonnes of inertia of my metal rod and pull it at all, etc etc etc)
Liam
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JoelP
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| posted on 16/5/06 at 08:58 PM |
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lol, bet superman could do it!
i must confess, ive never actually tested that one myself
[Edited on 16/5/06 by JoelP]
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dilley
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| posted on 16/5/06 at 09:02 PM |
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talk about wandering off the subject!!
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MikeR
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| posted on 16/5/06 at 09:03 PM |
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quote:
Originally posted by JoelP
quote:
Originally posted by MikeR
Ah, but as the speed of light isn't a constant and has been proved to vary over the surface of this planet, if you measure the speed of light in
a 'slow' place and whacked the metal bar somewhere else it could exceed the speed of light.
(ok, so this is mickey mouse physics as it wouldn't exceed the speed of light where you are)
true enough, but the real speed of light is that in free space
Ah, but it can still be affected, its gravity that affects the light waves and speeds / slows them. Sure that exists in 'free' space.
(how come you never have to pay for space? who said its free?)
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flak monkey
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| posted on 16/5/06 at 09:05 PM |
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This reminds me of alevel physics when myself and a mate used to talk nonsense for hours!
Sera
http://www.motosera.com
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owelly
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| posted on 16/5/06 at 09:10 PM |
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quote:
am i right to think that when fitting the brake pipes i have to take special care of having each pipe exactly the same length as the other? it does
matter right? i mean, if one pipe going to the front left is only 50 cm and the one going on the front right is 75cm, the front left wheel should
brake harder than the other one right?
Right, just to answer you question.....
it makes no difference to your car brakes, if the length of your brake pipes are not matched or paired. The longer the pipe, the more chance there is
to get air trapped but other than that, it makes no difference. HTH.
http://www.ppcmag.co.uk
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robertst
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| posted on 16/5/06 at 09:24 PM |
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ok had that in my head as thought B. was starting to dig out my school books to see what you just answered.
how did you guys get from car brakes to discussing the speed of light?!
great forum. never seen one like it!priceless
thanks!
Tom
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MikeR
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| posted on 16/5/06 at 09:26 PM |
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easy - we started out on simple engineering, added complex physics covering levers, added distance and E=MC2
pah ..... now, can someone explain to me why a cat can survive a fall from seven story building but not 6?
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trogdor
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| posted on 16/5/06 at 09:26 PM |
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i find the whole thing about the speed of light being a fundamental constant very fasciating! a good example is if a space ship was travelling at half
the speed of light away from a light source, the light from the source would still be travelling past it at the speed of light, not one and a half the
speed of light!
the thing that changes is the time that is passing, ie the time is going slower for the spaceship than the light source in comparision.
[Edited on 16/5/06 by trogdor]
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Liam
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| posted on 16/5/06 at 09:40 PM |
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LOL
What better place to have a ramble about relativity?!
Ok sorry forget it...
Liam
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