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dh79
Hi everybody, first post here. Looks like an interesting site.

I have some questions regarding a hydraulic system. I have a volume of pressurized fluid. I want to make a master-slave hydraulic system to use this pressure to apply work in another location. The pressurized fluid will apply the force to the master cylinder thereby transfering the force to the slave. I need to increase the force at the slave cylinder, so of course this means I need a relatively small master cylinder with a relatively larger slave cylinder. The problem is that I need to push enough volume to move the slave cylinder a relatively great distance when the master cylinder can only move a short distance. I'm limited by space on the master cylinder side. So is it possible to use more than one master cylinder connected in parallel to a single slave cylinder? What would be the result? Will multiple master cylinders provide the same force multiplication of the single master cylinder but with increased volume? All master cylinders would be the same size and powered by the same volume of pressurized fluid.

Please let me know if you require any further information or clarification. Thanks for any insight,
dh
StevenA
Can you use a larger diameter slave cylinder instead of operating multiple ones in parallel, or would the increased force from a larger surface area defeat the intent?

(I dislike the patent/I.P. system but admit I helped an employer get a patent on a plunger type solenoid I designed that uses a matching piston behind it in order to maintain a balanced force across it so very little work is necessary to drive it ... you can probably tweak the idea a bit and come up with something a bit novel. Also, if the master solenoid is electromechanical, there are many ways of increasing the efficiency. I've done some designs able to reduce power consumption by over 90% with a greatly extended life for actively controlled systems as you can avoid a lot of wear by reducing drive power once the solenoid is in motion ... and with a few tricks you can even turn a "bang-bang" system into a servo system. I've gotten switching times down to under 1mS, with a frequency response using closed loop position control over 1KHz, using basically an off-the-shelf hydraulic solenoid and for a joke at work, I played some music through a hydraulic system at work just by altering the drive circuitry for a solenoid.)

Fun stuff, though I don't believe I'll ever apply for a patent again. It's a system that allows legalized theft of ideas (not simply copying but true theft, as in an ability to deny someone using their owns thoughts). There are other ways people can sell their ideas without needing to claim sole ownership of an idea. Vested interests in physical property is something you need to protect, as it can be physically impossible for two people to share the same property without conflict, but ideas shouldn't be treated as if only one person can own it (it might sound ok on paper but it's a system that's abused way too often and I believe it's stagnating technology, at least in the U.S. It turns engineering into a virtual minefield of lawsuits and if someone has a truly novel idea, they already have a de facto monopoly on the information and can sell the idea for whatever they want without needing to ask permission from anyone to do so ... so it seems an insult to me to be expected to do research into what other patents exist or to feel obligated to ask permission to use your own thoughts and knowledge to solve some problem and in any event you still run the risk someone will claim they did that first ... being the first person to solve some problem should be enough of a reward without denying others the same opportunity)

/mode rant off

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dh79
Thanks for the reply.

Maybe I'm wrong about this, but I don't think I can use a large single master cylinder because then I would lose the force multiplication at the slave cylinder.

Making up numbers here, but lets say my pressurized volume of fluid is at 10 psi. If I had a master and slave with the same diameter, then the slave would also have 10 psi. Correct? But say I need 30 psi at the slave to do the work I need. So again, correct me if I'm wrong but this is only possible if I use a small master cylinder with a larger slave. Then I can multiply the force 3x at the slave. And of course the other problem is that in my problem the master cylinder can only have a short stroke while the slave requires a long stroke. So then maybe multiple small master cylinders with short strokes all working off the same power source (volume of fluid at 10 psi)? It seems to me it could work, but this isn't even close to my field of expertise so I could be totally wrong.
thanks for any input,
dh
StevenA
I apologize for not reading your initial post more closely.

By increasing the number of master cylinders, you're effectively increasing the area of the them, and in order to maintain the same pressure gain, the area of the slave would need to increase as well.

You're basically encountering a limit for energy transfer. If you increase the flow, you drop the pressure and visa versa.

So, you can run multiple cylinders in parallel, but this will increase the flow to the masters and in order to maintain the pressure gain, multiple slaves would be necessary.

Though it would seem more reliable and efficient to resize a single device and increase the area of both master and slave in order to accomodate the required flow.
dh79
Ok thanks. That makes sense. I guess I'll have to use multiple slave cylinders since I'm limited in space for a really large single slave. I'm got some more figuring to do...
thanks for the help,
dh
StevenA
QUOTE (dh79+Dec 16 2006, 07:41 PM)
Ok thanks. That makes sense. I guess I'll have to use multiple slave cylinders since I'm limited in space for a really large single slave. I'm got some more figuring to do...
thanks for the help,
dh

I don't know what the application is, but you might consider using multiple cycles of the cylinder at a higher rate to pump an adequate amount of fluid. That would add some form of directional valve and likely create some ripple in the output pressure, but it could be one way to keep the envelope small.
dh79
Ok, what is the relationship if there are multiple master cylinders but they are connected in parallel with directional valves separating the master cylinders. If say 4 identicle cylinders isolated by valves were actuated independently wouldn't that be analogous to having one cylinder actuated 4 times? Now what happens if all 4 are actuated at the same time? I suppose that if all the the valves are open at the same time then it would be as before where the cylinders are connected in parallel without valves.
thanks again,
dh
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