Case DH4B Trencher/Backhoe Won't Spin Trenching Chain

[r8f1k]

I have tested the pump with a pressure gauge, it holds 100 psi, it simply shudders between 80 and 100 psi when the lever is pulled to engage the trencher motor. The type of pump in post 89, is VERY similar to the pump that is in the unit currently. I am wondering if I could simply re-plumb the system with a simpler system of just a pump and a bidirectional control spool for the motor. I have plenty of hydraulic hose and my own crimping machine. I would also skip trying to use the backfill blade, I would take it off and eliminated it altogether. If someone could help me determine what kind of pump to swap in and what kind of spool would work.

 

[oldnslo]

Do you know the displacement and operating pressure of the existing pump? To get similar performance you need a pump with similar specs.

for the valve I would recommend a 3 position with motor spool rated for flow and pressure of that function.

 

[r8f1k]

The pump I have has a tag on it:
18-2081R LH
87-11-80260

I think it is Case part number:
H672705

Not sure how many splines are on it.....I can pull it and find out, any ideas of how one would properly plumb it? A simple hand drawing would be fine.

 

[r8f1k]

Do you know the displacement and operating pressure of the existing pump? To get similar performance you need a pump with similar specs.

for the valve I would recommend a 3 position with motor spool rated for flow and pressure of that function.

I already have this on hand:

https://www.amazon.com/Prince-RD512CA5A4B1-Directional-Control-Positions/dp/B0025PKDI2/ref=pd_lpo_2?pd_rd_w=lOsUk&content-id=amzn1.sym.116f529c-aa4d-4763-b2b6-4d614ec7dc00&pf_rd_p=116f529c-aa4d-4763-b2b6-4d614ec7dc00&pf_rd_r=3DT220WMYC8ZJ3J9DQJZ&pd_rd_wg=mzCsp&pd_rd_r=9da08fd7-bfb3-4e1f-8732-09249c70f8f7&pd_rd_i=B0025PKDI2&psc=1

I just need the pump.......

 

[r8f1k]

Does anyone know if all hydraulic pumps that have 13 spline shafts are the same diameter? Based on the Danfoos information for my Series 18-2081 pump, it has a 13 spline shaft. Just so I don't have to yank the pump out again, if I knew that most pumps were generally the same, I would order something like this:

Hydraulic Gear Pump 13 Tooth Spline Shaft CID 0.97 - 2.74 SAE B-2 bolts GPM 3-29 | eBay

Find many great new & used options and get the best deals for Hydraulic Gear Pump 13 Tooth Spline Shaft CID 0.97 - 2.74 SAE B-2 bolts GPM 3-29 at the best online prices at eBay! Free shipping for many products!

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Then plumb it to the system as best I can and run it to a spool valve with a detent.
Thoughts?

 

[oldnslo]

Yes 13 tooth spline is a standard for SAE - B.

Some things to consider on this trencher drive:
The current hydrostatic drive provides infinite speed adjustment of the trencher chain. Also allows feathering in both forward and reverse direction if trying to position a tooth to work on it.

• With hydrostatic drive typically if pump is bad the motor will also be bad since the debris circulates between the two components.
• With gear pump and detent valve you have one speed.
• Yes you can probably feather the chain into position but would be very challenging to try and hold a slower speed without a priority flow control in the circuit.
• what pressure does existing pump operate at? Will the gear pump be able to achieve the same pressure?

 

[r8f1k]

Given that the pump I have is Series 18-2081, how does one figure out if it is SAE-B?

 

[oldnslo]

Given that the pump I have is Series 18-2081, how does one figure out if it is SAE-B?

either find a detailed model code break down on the the current unit or take existing pump of and measure it. SAE - B is 4 inch diameter pilot 5.75 inches between mounting bolts.

 

[r8f1k]

Do you know the displacement and operating pressure of the existing pump? To get similar performance you need a pump with similar specs.

for the valve I would recommend a 3 position with motor spool rated for flow and pressure of that function.

1 Spool Hydraulic Directional Control Valve Motor Center 13 GPM 3600 PSI NEW! | eBay

Find many great new & used options and get the best deals for 1 Spool Hydraulic Directional Control Valve Motor Center 13 GPM 3600 PSI NEW! at the best online prices at eBay! Free shipping for many products!

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Would this work? I would like to get a spool that can hold in one position while the trencher is running. I assume a detent is needed? Anything specific to look for on the nomenclature of a spool?

 

[oldnslo]

That valve is not detented per the provided description. With out detent you would have to hold the valve shifted to keep chain spinning.