? ID Hydraulic clutch line

[robertglines1]

is .210  a proper ID line size. I'm using the Volvo system and the best I can tell that is it. The only difference is I'm running it 35 plus ft instead of 6 or 8ft.  The next size up is .275ID.  I'm not a hydraulic guy and do not understand the liquid compression problem if the line is to large or to long.  The master and slave are a matched set..   Bob

[luvrbus]

Bob, I have no idea what the Volvo trucks use but on a 45ft Prevost the clutch uses a 5/16 steel line from the clutch pedal to the slave cylinder

good luck

[robertglines1]

Thanks: Have local supplier for stainless 5/16 stainless. That's the way I'll go. Just wanted to make sure! Feels good to making final hook ups!! The .210 is the 1/4 line.  The line he has is sold OD that's why .210 ID  Will Buy the 5/16th rated 2700 psi   Bob  

[rusty]

Bob, I would use stainless steel tubing. Jim and I have had long discusions on this. Because the cylinders (slave and master) are small if the rubber hose swells at all under pressure it will take more movment of the master cylinder to make the clutch work. Jim says the rubber hose will not swell but he is a rubber guy . Also are you using any asssistance to help make the clutch engage easier? You will find with the extra length the volvo system will be harder to engage. I have an untested system that I am using on my 15. You can see it on my project page at Eagles.

Wayne

[luvrbus]

Prevost and MCI use no assist on clutch and the pedals are easy to push but I like the idea of a assist

[rusty]

That is true Clifford but they have the correct geomertry for a bus that is 40 foot long. I look at using the one out of prevost but did not like having to fill it under the dash. I did not look into MCI.

Wayne

[luvrbus]

Wayne they sell a kit to remote mount the reservoir just about anywhere for those fwiw

good luck

[robertglines1]

Rusty;have a print out of your system including air assist. Also have air assist cyl (came with set up from Dick E.) Also have print out of Jim's system. What was missing was line size.  I will be using the seamless stainless . 50ft roll 5/16th 79$. Fittings to terminate $11 each end then short rubber from termination block to slave cyl to take up any engine movement/vibration.  Sound correct?    I took complete master and slave out of volvo truck.Bob

[rusty]

Robert, Sounds good. If you would please let me know how the system works when done. Also if you have some pictures of the assist that would be nice if mine doesnot work.

Wayne

[rv_safetyman]

Just to be clear, I used two wire braid hydraulic hose.  My system will go to about 300 psi (against the clutch brake) and the hose is rated for probably 10 times that (working pressure - burst is 4 times WP).  I am pretty sure that I am not getting any expansion.

I went with hydraulic hose, as I have access to some pretty good prices (not Gates  ) and it is a bit easier to route.

Jim

[bevans6]

I personally would use -4 Aeroquip teflon lined braided hose.  Rated to a couple of thousand pounds, very thin and flexible, easy to fish, easy to install ends after installation if that's appropriate.  I use it on all my race cars, -4 is 1/4" ID.  Pricey though.

Brian

[robertglines1]

FWIW the stock truck line is stamped 6mm . I have a empty 2 inch PVC straight shot from front to just above clutch location. Thought a termination block there then rubber to slave. Same in front-within 24 inches of master cyl. The air cyl looks just like your picture Rusty 2 inch stroke.  I have used the Teflon line on dune buggy's etc but this time things are a little less accessible in case of a problem..Bob

[bevans6]

I forgot to say the reason for choosing the size of the line.  In hydraulic brake systems, there is very little movement of the fluid and compressibility is more of an issue, so a smaller size line is selected.  Typical is 3/16 hard line or -3 flex line, in race cars people often use -2 flex line and get reduced weight and a harder pedal feel.  With a clutch, the requirement is for quite low pressures so compressibility is not an issue, but a relatively high high volume of fluid is transfered through the line.  With a skinny line, fluid velocity is increased and you can get cavitation and subsequent release of gases that lead to bubbles in the line and ongoing bleeding issues.  Going to a larger line reduces fluid velocity and eliminates cavitation. 

Brian

[belfert]

I thought brake fluid for normal hydraulic brakes was considered non-compressible?  When I went to air brake school the instructor said that drivers of air brake vehicles don't typically notice warped rotors because the air compresses, but hydraulic brake drivers feel warped rotors in the pedal because the fluid doesn't compress.

I've been working on a lifting system for rockets and everyone says to use hydraulic cylinders instead of pneumatic because the pneumatic will not be smooth due to the air compressing.  The hydraulic is supposed to be smoother because the fluid doesn't compress, or at least not much.

[luvrbus]

Any liquid can be compressed with enough pressure I doubt you will ever get enough pressure on a normal system to compress brake fluid