3320 Power beyond, conversion to Closed Centered operation

jdjllee · Jan 16, 2011

I've been laid up with a bad cold and spending some time studying my 3320 hydraulics and looking for a GOOD way to run a set of limb loppers (or other closed center equipment in general) off my Power Beyond Loop at the back of my tractor. (I'm not a big fan of bungee cords on an SCV). After studying the clippers and tractor hydraulics it seems that the best course in the case of these small clippers might be to operate closed centered. So the question is: how can I provide an adjustable constant pressure hydraulic source and return? To that end, I'm thinking of installing a pilot operated refief valve (rated > 10 GPM) in the power beyond (PB) loop on my tractor. Constant (adjustable) pressure would then be available via QD installed at the relief valve inlet. The outlet of the relief valve would connect via QD to the return (Tank) connector of the PB. An "equipment" return QD would be installed in the PB return as well. The PILOT on the relief valve can be used to completely unload the pump any time either manually (selector valve) or automatically when the equipment is not in use. I don't have it all figured as yet. This circuit 3.12 (link below) shows the basic idea. In this circuit the pump is unloaded (relief pilot vented) any time the valve is centered. The relief valve provides full pressure whenever the spool is shifted to extend/retract the cylinder (relief pilot blocked). For the limb loppers the directional control valve would be converted to two way by plugging the unused port. Comments appreciated.

Hydraulic Circuits Using Pilot-Operated Relief Valves | Hydraulics Pneumatics Engineering

kennyd · Jan 16, 2011

Forget it...You cannot use a CC valve with your system. You are making it way to complicated, the loppers are available in a OC configuration, so that is what you should get.

jdjllee · Jan 16, 2011

Well, I happen to differ but I'll just leave it at that rather than get into a flap
over some simple misunderstanding. This is a forum for discussion of ideas, correct? Often times, I agree, my ideas may seem complicated or maybe they just don't come across well in my writings. So if you did not get a clear picture of what I was proposing I can understand. As for me, I don't always jump on the cheapest, easiest, or quickest answer to a problem. Rather than try to further explain, I'll just work this one out on my own. If I carry this one through ( I am only in research phase right now) and build a working PB adapter I'll still consider sharing it with you folks and maybe even offer up a parts list. No guarantee, some of the things I conjur up, never get off the idea board.

oldnslo · Jan 17, 2011

The P.O. relief will work as long as you have a remote pilot capability. This will add some plumbing and cost but the concept in general is correct. Just note that any pressure in the pilot is going to be an increase in the PB/tank line during normal operation and could be a source of unwanted heat generation.

Roy