CR4 - Blog Entry: Is NFPA on the Right Road?

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Peter Nachtwey Associate Join Date: Apr 2009 Location: Vancouver, WA, USSA Posts: 29 Good Answers: 2	#1 Re: Is NFPA on the Right Road? 09/10/2009 3:28 AM
	I haven't seen the road map but it doesn't sound like it addresses one of my biggest pet peeves, a lack of specifications that mean something. Show me a part that doesn't have a transfer function or differential equation stamped on it an I will show you a part that is kludged or evolved and not designed. Until the hydraulic designers of hydraulic components provide better data that can be plugged into a simulation program, the hydraulic world will be kludging or evolving systems too instead of designing them. When I get into the field I can ask what is the gain in the extend and retract direction, what is the natural frequency of the system and all I will get is blank looks and shrugged shoulders. I want to know the hydaulic capacitance of pipe and hose per unit of length. I want to know what the pressure loss is when oil comes out or in through the valve of an accumulator. I want to know how the swash plate of a hydraulic pump moves as a function of pressure and command signal. Is there slew rate limiting? I want to know the forumla for leakage in a valve and the case drain leakage in a hdydraulic motor. I wan to know the inertia of the motor and the friction of the motor as a function of angular velocity. I want to adjust the proportional band of a pressure compensated pump. I want to make it narrower, increase the gain, when there are accumulators in the system. There should be a common way of rating valves. Comparing two valve when one has a bode plot show a response to a 95% signal to another valve that has a response to a 50% signal is like comparing apples to oranges. Rating valve at 90 degrees is nuts. You can't operate a valve anywhere close to that in a closed loop system. As soon as you add another 90 degrees of phase lag due to integrating velocity to position you are at 180 degrees and oscillation. This isn't even taking into account the phase delay due the time it takes to pressurize the oil. Give the engineers some information to design with and you may get engineers to do real hydraulic designs.
	Good Answer (Score 2)