Hydraulic Clutch, let's try this again

[Brian Diehl]

Jim, does that mean your clutch pedal pushes on a valve to allow air into the air brake chamber diaphram?

[rv_safetyman]

Yes.  My clutch pedal is actually a brake treadle valve.  It applies air to the air brake chamber.  The air brake diaphragm then pushes on the brake rod which pushes directly on the piston of the master cylinder.  Pretty simple.  Only problem is making it more sensitive to pedal movement (i.e. make it feel and act like a real clutch pedal).

I will be off line for a couple of days to go play in the woods.  If there are more questions, I will be back on line Monday.

Jim

[Len Silva]

This discussion is frying my brain.  I just "invented"  the concept shown here.  I'm sure it's not new but it is to me.  Two hydraulic cylindres of different proportions mechanically interlinked to provide assist. 

What do you think guys?  It looks like it should work but figuring out the numbers or if it is practical is beyond me.

I'm sure you hydraulic engineer types have a common name for this setup.

Len

[Sean]

...I just "invented"  the concept shown here.  I'm sure it's not new but it is to me.  Two hydraulic cylindres of different proportions mechanically interlinked to provide assist. 

What do you think guys?  It looks like it should work but figuring out the numbers or if it is practical is beyond me.

I'm sure you hydraulic engineer types have a common name for this setup.

Umm, I don't think there is a common name because it doesn't exist.

Putting any kind of "black box", whether it consists of hydraulic cylinders, a bunch of gears, or fairy dust, in between two ends of a linkage can't, under any circumstances, alter the force*distance equation, unless that black box is connected to a source of power (such as an external pump, or a source of electricity).  That's simple physics -- it's the First Law of Thermodynamics.

I invite you to build such a system, and press on one end to see what happens.  I assure you, it won't help Brian with his problem.

Brian put it very well when he said "There is no free lunch" -- a great description of the First Law.

-Sean
http://ourodyssey.blogspot.com

[Len Silva]

Yeah, I see it now.  I need to learn to sit on these things for a while before posting.  I do occasionally have ideas that do work. 

Len

[Brian Diehl]

How about a hydroboost master cylinder from a GM truck?  I think the biggest issue might be not having any boost without the engine running. 


Would this cause any issues with the existing powersteering system?

I forgot who mentioned the hydro boost, but my initial google search makes it sound promising.  The only "negative" is having brake fluid in the mix ....

[bus05eagle]

I have a 1 ton Chevy truck with this on it it works off the power steering pump and you can use it 4 time with out the engine running after you stop you still have brake but the pedal is hard to push after the 4 times and you are going to have brake fluid unless you go with a complete air system and then no clutch with out air

[edroelle]

The Bendix Hydraboost is far in excess of your needs.   It was designed to stop 10,000 pound vehicles.  You want an ASSIST, to lessen your pedal effort.

Ed Roelle

[Brian Diehl]

The Bendix Hydraboost is far in excess of your needs.   It was designed to stop 10,000 pound vehicles.  You want an ASSIST, to lessen your pedal effort.

Ed Roelle

Hi Ed,
Do you have any alternative suggestions?

[DavidInWilmNC]

Would a standard MCI clutch air assist cylinder be any help?  Maybe two of them side-by-side would give more assistance?  Good luck with it.  I'd love to lighten my clutch a bit, too.

David

[edroelle]

Brian,

I am not sure of what the answer is, but a brainstorm session with Jim Shepherd, Sean, Jerry, and others would come-up with the best design.

To assist your pedal effort, you need a power source - hydraulic, air, vacuum, or electric.  Levers or unpowered cylinders will not do it alone.

Try for simplicity and proven durable componenets.

I have not understood all of the discussions, so this may duplicate Jims or piggyback on some others.  (I understood Jim's design to use both air and hydraulic components.)

How about using as components, the very smallest brake can, a brake treadle valve, a proportioning valve (I am familiar with hydraulic prop valves but are there air proportioning valves in the trucking industry?) and possibly other valves.  The brake treadle valve would be connected to the clutch pedal with an output air line to the brake can.  The brake can would be connected high on the clutch pedal to assisst your pedal effort.  (Max brake can stroke to equal or be greater than max clutch pedal movement at the pin connection.)  As you press on the clutch pedal, you open the treadle valve to the brake can, to assist in the effort on the pedal.  The proportioning and other valves would allow for developing the "feel" of the pedal.

This would take some develpment as Jim is demonstrating.  I would suggest building a mock-up of the design to do the development work.

Others inputs are desired.

Ed Roelle
Flint, MI

[Bob Belter]

Ahoy, Brian,

Eagle clutch

Here are a few comments on my experience with clutch actuation on my Eagle-01.

First off, the engine which I installed in my Eagle is an M-11 Cummins 400 hp, and the Clutch is a 14" double disc item.  I don't recall the model but even though it is the strongest 14" unit available, it is a bit marginal on capturing the torque of the engine.  The transmission is a Roadranger ten speed overdrive RTO1110.

My first clutch try was an air operated unit.  Friend Andrew had an air actuated clutch in his classic Cortez Twin Coach with a 505 Cummins, 5 spd trans and a single disc "old" clutch.  It worked fine.  My installation did NOT.  Behaved like a dog clutch!!!!  It was so abrupt that my Eagle was not driveable.  So, I finally did a little engineering and a few tests.  I measured the force (air pressure) for clutch actuation right at the clutch arm.  For the cylinder size which I had installed, the air pressure at the first ~~1" of travel was about 61 psi, and for full stroke, about 65 psi.  No wonder it did not work.  It was behaving like a dog clutch.  I suggest that if you have a "modern" double disc clutch, don't even try any actuation method which does not include positional feedback to your clutch pedal.   I expect that the older single disc clutches have some reasonable relationship between stroke and actuation force.  My modern double disc clutch does not.

I installed a hydraulic clutch actuation system which was comprised of two cylinders of 1" bore and 6" stroke.  They use ordinary red mineral hydraulic fluid.  There must be a bleed process for the system, and the way I did mine was to use a solenoid valve ported from the high point at the actuator cylinder to the reservoir. . It is normally closed, and opens with a micro switch when the pedal is ~~ ¼" from all the way up.  The actuating cyl is mounted so that the pressure end where the solenoid valve is mounted is high.  It works just fine.  At the clutch, you must have a light spring to keep the actuating cyl extended    The nice feature of this setup is that you don't have to play with the position of the cylinders.  As long as all the strokes are within cylinder actuating range, you are just fine, with the starting point being established by the bleeder solenoid and micro switch combo.  You must devise a pressure pot system to bleed this setup.  I use a modified old stainless steel fire bottle.  Clean and easy to find.

The hydraulic hose which I used to connect the cylinders was a two wire -4 hose (1/4") about 35' long.  It was something that I had on hand.  The fluid friction in the long small diameter hose made it too slow to double clutch properly.  Easy fix --  Just thin the fluid with mineral spirits – NOT!!!  The reduced lubricity caused friction and o-ring wear problems in the cylinders.

Bigger hose – About $175 worth of -8 one wire hydraulic hose (1/2").  Diametral expansion of the hose resulted in insufficient clutch arm travel. 

Back to the (CAD) drawing board.  I installed stainless steel tubing (½" OD) with short pieces of the -8 hose above to connect to the cylinders.  It all works just fine – finally.

I plan to add an assist system to my clutch.  Probably just be an air cylinder sized an stroked to reduce some of the force.  Actuation will be by a solenoid valve triggered by the micro switch mentioned above.  Again, the components must be sized so that the pedal actuation is not slowed.

Enjoy /s/ RHB