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Hydraulic Pump Capacity on 1971 DB990

Posted: Thu Apr 08, 2010 2:19 am
by paulver
Hi Guys!!
It's been awhile since I've posted here, and I have a question regarding the capacity of the hydraulic pump on my 1971 DB990 Selectamatic. I'm planning on building a 3 point log splitter to put on the tractor, and I need to know the gallons per minute that the pump will put out. The book I have says that it'll put out 6 U.S. gals. per minute. That seems kind of low to me for this size tractor. Is that because the pump uses the transmission fluid to operate the hydraulics? And, would that be enough to efficiently power a log splitter?

Thanks.

Paul, in the U.S.

RE: Hydraulic Pump Capacity on 1971 DB990

Posted: Thu Apr 08, 2010 6:23 am
by erkki
6 US Gallons per minute is about correct. With full throttle it gives 28 litres/min.
Hydraulic flow is originally designed for using rear lift, where it is well sufficient. If you have a large ram on the splitter, it will be slow and powerful, small ram will be quicker but not necessarily sufficient for spliting a large lump. The flow is enough for log splitter if the ram is correctly chosen. One possibility is to make the plumping a little more complex and make the splitter double speed unit. With heavy splitting the oil flow is given to one side of the ram piston which gives max push. When quicker operatios is needed the flow is given on both sides of the piston, which reduces the push to the area of ram arm.

For light work 4...5 tons is sufficient, for heavy jobs double of that, depending of course of the quality of the timber and shape of the wedge.

The system gave pressure of 140 bar as new, an old system can be different.

Good luck

RE: Hydraulic Pump Capacity on 1971 DB990

Posted: Mon Apr 01, 2013 4:16 pm
by johnh
sorry to resurrect this thread but Erkki would you explain in more detail what this double speed plumbing would be like?

thanks,

RE: Hydraulic Pump Capacity on 1971 DB990

Posted: Mon Apr 01, 2013 6:42 pm
by kato
Maybe this is off topic, but..

Might be other methods, but here is the one I know..

You can connect a device, dont know the term in english, between the hydraulic cental and the ram of the logsplitter. This device leads the return oil from the "rod-side" of the ram to the piston-side of the ram. This connection is shut of when pressure bulids up on the piston-side of the ram.

-Or you can use a central that has this function built in. Then you will have two "gears" when running the ram out. 1, fast and low force. 2, slow and full force.

Brgrds,
Kato.

RE: Hydraulic Pump Capacity on 1971 DB990

Posted: Mon Apr 01, 2013 10:38 pm
by johnh
Thanks Kato.

my ram has two hoses which go straight to a double acting valve. what do i need to put in there to give this 2-speed feature? or can you do a circuit diagram?

RE: Hydraulic Pump Capacity on 1971 DB990

Posted: Mon Apr 01, 2013 11:33 pm
by kato
Here is a link to a pdf that has a diagram and a sketch of the part. The text is in Norwegian, so I dont know if you will be able to read it.

http://www.okonomi-deler.no/skjema/A32.pdf

But, you take the two hoses from your ram and connect it to this device. Then run two hoses to your central (or double acting valve). There are also centrals availible that has this function built in. Maybe worth checking the prices of both alternatives..

Hope this was some help.

RE: Hydraulic Pump Capacity on 1971 DB990

Posted: Wed Apr 03, 2013 8:40 pm
by johnh
Thanks for the link Kato but i can't find any more info on this device, even on the okonomi-deler website. do you know what individual hydraulic components it is made from?

RE: Hydraulic Pump Capacity on 1971 DB990

Posted: Wed Apr 03, 2013 10:56 pm
by kato
The unit is a block with 4 connection and 1 adjustment. I don't know what parts you would need to build one. But I have seen a design once, that had a couple of non-return valves and a few other parts. -But I could not locate it.

Been looking around the web a bit. And it looks like it's, in english, called: Regenerative design or valve.

Here is a link to a "english-speaking" web site that has a central or valve that has this feature built in. It does not look like the ones that is for sale in stores here. But the function seems to be the same. http://www.cylinderservices.net/catalog ... did=601852

Also found a link to some thing that looks like the first one I posted. http://www.sunhydraulics.com/PDF%20File ... _regen.pdf

And here is a description of how it works: http://www.hwhcorp.com/ml37939.pdf

Sorry that I could not answer you question..

Feel free to PM me your email adress if you thing I could be of further assistance..