In Reply to: Re: Golden Jubillee hydrolic pump posted by Ultradog MN on July 31, 2020 at 03:45:15:
I dont consider this discussion a hijack. Its discussing options relevant to the original question.
I have been asked a similar question by the people inquiring about my gear pump conversions. The pumps I use are sized to match the flow rate of the OEM pumps but you could double the flow at the same cost with a bigger pump. So I will give you the same answer I give them.
Open center control valves and systems are sized to handle a maximum flow. Substantially increasing the flow rate can have undesirable consequences. Take the NAA as an example. That valve design employs an unloader spool that acts as a pilot for the main control spool. The main spool is shifted by a pressure differential applied to the valve circuitry when the 3pt handle us operated. Its conceivable that doubling the flow rate may cause enough back pressure that the balance in those pilot circuits is disrupted and they dont operate properly. At higher engine RPM draft and position control may not work properly. That is obviously a gross general speculation in response to a general question and I dont have a definitive answer. I'm sure there is some head room built into all of the designs and you can certainly go a little bigger but how much is difficult to predict. Doubling the flow is a hefty increase. So all I can say for sure is try it and see what happens
I took a look at those later model pumps - only a couple hundred bucks which is cheaper than my conversions. However judging from the picture it's a lot longer than the older piston pumps. Will it actually bolt up on an NAA or Hundred series engine? My understanding is that on those engines there is an issue with little to no clearance for a longer pump. If it will bolt on and work I'd drop my conversions in favor of it and consider just making the bits needed to plumb it into the older machines. That looks like it requires something more than OTS fittings. If you are sure they will bolt up to a 134 and 172 engine I will actually pop for one of those pumps and enlist a Guinea pig willing to try it and see how it works.