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Bypassing DC hydraulics on a LT70??

Started by stavebuyer, November 23, 2012, 07:55:55 AM

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stavebuyer

I am in the process of setting up my LT70 stationary. I have two external 3phase AC hydraulic power packs that will be plumbed to run the infeed deck, green chain, and roller beds etc. I'd like to bypass the DC pumps built into the the mill in order to increase the speed of the bed functions and eliminate the power strip maintenance. I know Bibbyman and maybe a few others have done this. I have a couple questions; WM recommends the Dexron fluid I assume because its thinner and easier on the DC pumps. When switching to an external pump did you need to stay with Dexron or will the valve body and cylinders on the mill be ok with regular aw-32 hydraulic oil if supplied by an external pump? The plumbing on the mill looks like the pumps feed a flow control valve that then is routed to a bank of solenoids that are operated by my remote joysticks. What is the volume and PSI that I should have coming into the flow control valve or does the valve itself take care of regulating pressure and flow to the valve body?

customsawyer

I can't answer your questions about amount of flow or the psi. You will not be able to eliminate the power strip completely as you will still need to be on the strip to operate one of the functions on the log deck. If your log deck is a WM that has the toggle switch to change from the loader to the chain feed. I run a blend of hyd. oil and ATF. It is a little slow in the cold mornings but soon warms up to running speed.
Two LT70s, Nyle L200 kiln, 4 head Pinheiro planer, 30" double surface Cantek planer, Lucas dedicated slabber, Slabmizer, and enough rolling stock and chainsaws to keep it all running.
www.thecustomsawyer.com

ElectricAl

We used Dextron II in our remote power pack. Seemed to work fine.
The hoses from the power pack went right to the WM valve bank manifold.
For 12 volt we used a 12v power supply from Radio Shack to trigger an unloader valve at the pump.
The unloader or bypass lets oil go from the pump to the tank when no pressure is needed. When the WM lever is pulled the 12v circuit is completed and the bypass closed sending instant GPM & PSI to the system.

Worked great for our 1993 LT40HDE15.

When sizing the system GPM & PSI  ~  an AC powered pump has a constant GPM through out the PSI range. However a DC powered pump GPM declines as PSI increases.

Call the Manufacture of the DC pump with the pump model and code. Find out what the GPM is at 500 PSI.
Most WM systems run with some back pressure 500-600 PSI.

Once you have the flow for one pump you just double the number to get the flow of your DC system.

One of your power packs may be enough for the sawmill but you may need both to run in tandem for the log deck. That can be done with wiring. I'd set the second pump to only start when it's really needed.
At the point where the two are tied together you'll need a hydraulic back flow preventer on the second pump.
Linda and I custom saw NHLA Grade Lumber, do retail sales, and provide Kiln Services full time.

MartyParsons

Hello,
The system is 4 gal per min. The only reason WM specs low visc hydraulic oil is so the electric pumps will run when cold temp. You should have a hydraulic pressure gauge on the hydraulic valve and the relief should be set at the factory. There should be a hydraulic relief on you AC pumps also.
I am not sure about running two pumps on the same system.
M
"A pessimist sees difficulty in every opportunity; an optimist sees opportunity in every difficulty." -Winston Churchill

Bibbyman

The pump system we're using on our LT40 is filled with A32 light weight hydraulic oil.  8 years and 3000 hours with no problems that I can contribute to the oil.
Wood-Mizer LT40HDE25 Super 25hp 3ph with Command Control and Accuset.
Sawing since '94

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