For what its worth, I think we (the Power Trac forum at large) calculated the theoretical potential HP at the main PTO of a PT425 at something a tad less than 14HP. You should think about Raw Dodge's comments about fluctuations and what you'd get out of the PTO on the Power Trac. From my own generator, it has a governor. When the load is high, it opens the throttle to boost the gas, to maintain the known RPM that will generate 120V. There's no meter or electronics that control the engine speed. Its just a set throttle of either OFF or ON at about 3600RPM set at the factory. Your Ventrac generator is belt driven, correct? How do you set the engine RPM for proper voltage? Is there a voltage meter and you increase the throttle until you get your 120V and the engine just holds there? I'd suspect if you drove it off of the PT's hydraulics, you'd just do the same thing. Since a fluid is not compressible and belts can slip, I'd think you'd get more consistent power with hydraulics than belts. But you're going to get substantial HP loss of available power from the hydraulics VS the belt. The 13,000 watt generators I've seen recently are running 20+HP engines and those are direct drive. You'll never get that out of the PT425 hydraulic PTO. Using the calculator at this website and plugging in the rated PT425 main PTO pump pressure of 2500PSI and flow of 8GPM you get about 14HP
Hydraulic Calculations | Fluid Power | Advanced Fluid Systems (2500PSI X 8GPM) / (1714 X 85%) = 13.73HP For more on what the 1714 is and why 85% efficiency.... OUCH, my brain hurts! :laughing: 1 horse power = 33000 foot-pounds per minute (by definition) 1 US gallon = 231 cubic inch (by definition) 1 psi = 1 pound per square inch (by definition) In the equation HP=kΔPF where F = flow rate in gallons per minute, ΔP is pressure difference in psi, and HP is power in HP, you need a conversion factor. Doing everything in inches: HP33000∗12∗inch−pounds/min=kΔPpounds/in2flow231inch3/min from which it follows that k=23133000∗12≈11714 In other words, "in plain English that a 9th grader can understand, and yet be correct and true to its purpose and place in life to satisfy seasoned physicists": 1714 represents the numerical scale factor needed to obtain pump power in HP given pressure in units of psi and flow rate in gallons per minute. It is not an exact number - only approximate."
