DK55 and general hydraulic questions

Piney Woods Rooter · Nov 28, 2006

I'm looking at various 3-point attachment, remote hydraulic connected log splitters. Most manufactures can tell you how many tons of force the splitter will produce at a given input pressure (tractor's hydraulic system output pressure).

With this in mind, and thinking about other hydraulic powered attachments, I've come up with the following questions:

1) What should the main hydraulic system pressure be on my '03 DK55?

2) The specs for the new DK55 show a flow rate of 9.9 for the main pump and 4.3 for the steering pump for a total flow of 14.2 GPM. Should that be fairly close to an '03 DK55? What's more important in the real world, main pump capacity or total capacity?

3) Does the power steering pump contribute to or otherwise affect the main hydraulic system's output pressure?

4) Does engine RPM affect max pressure and flow rate or just flow rate (cycle times)?

Am I missing anything else that I should be asking about - regarding hydraulics?

Thanks in advance,

PWR

KiotiDave · Nov 29, 2006

Hi,
There is only one pump in that system. The pump has a diverter valve that dedicates a certain flow to the steering system.
If you put a guage in the remotes you will find aprox. 2300psi at idle when turned on. This will vary with the consumption rate of the attachment you are using. You can increase volume with a higher RPM, but you won't increase pressure as it is set and regulated with several relief valves in the system.
This pressure should be enough to run most attachments except hyd motors with big flow requirements.
Hope this helps,
KiotiDave

County Sawyer · Nov 30, 2006

To try and answer some of your questions, the following are rules or what ever for hydraulics or for that matter nearly all non variable pumps. First of all, a pump does not pump preasure, A pump, pumps volume or flow. Preasure is created as resistance to flow. If there is no resistance to flow then there is no preasure. The displacement of a non variable pump is given in cubic measure per revelution. As you said the pump is rated at a given gallonage per minute at a certain rpm. Hence, increase the rpm, more gallonage or decrease the rpm, less gallonage depending on the physical configuration and restrictions of hoses, fittings or what ever are in the system. As for most tractors that I have worked on, they have two pumps built into one running on a common shaft rather than a priorty system. In priority system, like for power steering, if the rpm's drop then the output drops but the flow to steering remains constant and the flow to attachments etc. could be very little or none. That is why they have duel pumps in one housing. Increasing the rpm's will increase the flowand increase preasure against he load, but only to the point of the releif valve setting. The releif valve governs the maximum preasure in the system. As for combining the flow from the steering with the main flow. No, that does not happen because it would cause back preasure on the steering and hence no steering. Hope I've helped with your questions. Go and enjoy your tractor and all the things it can do for you.

KiotiDave · Dec 1, 2006

Hi Piney Woods Rooter,
Your DK55 does have a DUAL PUMP, County Sawyer is correct. It is a single housing with 2 gear set ups on a single shaft. The priority does nothing but keep a constant flow no matter the RPM'S to the steering(safety).
I hope I didn't mislead anyone.
Take care,
KiotiDave