Kubota MX4800 3rd function - roll my own - check my work

[Michael In Tennessee]

I've been reading everything I can on a roll your own solution for a 3rd function and am ready to commit to fabrication.

The MX4800 has a flow rate of just under 10 gpm, so the commonly used Northman electric spool valve on a D03 plate seems to work here. (Northman SWH-G02-C6-D12-10) I'd get that from Northern Hydraulics.

I'd like to avoid NPT fittings as much as possible so the D03 subplate I found is -6 SAE ORB at Surplus center. Given I have a backhoe installed, the main hose routing is pretty simple. PowerBeyond alreaedy goes to the rear of the tractor using a 1/2" hose with a -8 JIC fitting. I can use that directly for the output of the 3rd function. It looks like it will bend to where I need it just fine. Then a short 1/2" hose with -8 JIC ends between the loader valve and the 3rd function and the main hydraulic loop is done. I'll be using 90 degree -6 ORB to -8 JIC fittings on the subplate. SAE fittings will swivel to where I need them without issue, which is way better than forcing NPT fitting to clock correctly.

To service the 3rd function, 3/8 hoses with -6 JIC fittings will run up the loader arm and I'll modify some dual hose clamps to work with the existing welded hard line tabs on the loader arm. These tabs are currently unused and are there for the Kubota branded hardline kit if one were to pay that price. I'll have to fab up a bracket on the loader cross tube for two JIC to NPT bulkhead connectors and attach QDs to the NPT side. Haven't found an elegant way to avoid NPT fittings here.

I'm still working on the electrics, but I'm leaning on using a Polaris Glacier Pro Gear shift plow knob for control. It has two buttons on the face that would control the 3rd function. The shaft diameter on a Polaris is 1/2" or so, so somehow I'd need to sleeve the knob or joystick shaft to adapt diameters. I haven't seen great details on how to do this on-line yet, but apparently others have used this handle in similar applications. https://ranger.polaris.com/en-us/shop/accessories/brutus-accessories/2879227/ I have no idea if this knob will work well and if someone has a better idea, I'm all for it. Obviously, I'll run the switches through relays due to current limitations as well as just for good electrical practices.

The 3rd function valve will fit below the loader joystick and I think a simple vertical plate bracket below the loader valve and in front of the treadle pedal will be out of the way. I can't exit from the right side of the tractor anyway, so a little more stuff there is no big deal.

So, thoughts?

 

[ovrszd]

Go for it. With pics of course.

 

[Michael In Tennessee]

You'll get pics. .

 

[N2DFire]

Here's the write-up on my 3rd function build on a Kioti CK35. I used the John Deer grip for mine. It's meant for low current so I put in relays too but another member here has been using his without them and had no trouble.


Just be ready for there to be something you didn't plan for, no matter how much/well you plan.

Best of luck with your project.

 

[MtnViewRanch]

Just a heads up, it's not really a good idea to have 10GPM flowing through any #6 SAE fitting. It is a restriction on that amount of flow. You might want to find a work around for the application.

 

[Michael In Tennessee]

well, I really hadn't thought much about -6 SAE being much different from 3/8 NPT. However, it seems so. Most folks go 3/8 NPT and have no issues. I just hate NPT fittings and in my application, I'd have to get 4 elbows aligned just right, which sucks with NPT fittings. I can get 3/8 NPT or -6 SAE D03 plates for a good price. The -8 SAE is harder to find at a good price.

I have not found any good engineering data that actually says recommended flow rates of various fittings nor any data on internal flow area of various fittings. Do you have any references? I looked through the parker catalog, but really, they only have a few curves and 10 GPM is just off the curves for a -6 fitting. I also found a military narrative discussing in generalities about various hydraulic fittings and they do recommend -8 SAE or 3/8 NPT for my application, but has no engineering data to back it up.

 

[MtnViewRanch]

well, I really hadn't thought much about -6 SAE being much different from 3/8 NPT. However, it seems so. Most folks go 3/8 NPT and have no issues. I just hate NPT fittings and in my application, I'd have to get 4 elbows aligned just right, which sucks with NPT fittings. I can get 3/8 NPT or -6 SAE D03 plates for a good price. The -8 SAE is harder to find at a good price.

I have not found any good engineering data that actually says recommended flow rates of various fittings nor any data on internal flow area of various fittings. Do you have any references? I looked through the parker catalog, but really, they only have a few curves and 10 GPM is just off the curves for a -6 fitting. I also found a military narrative discussing in generalities about various hydraulic fittings and they do recommend -8 SAE or 3/8 NPT for my application, but has no engineering data to back it up.

Just measure the IDs. They will easily flow more than a -6 fitting and that's all you need. If you use the fittings that I had linked to in the block, there is ZERO problem orienting 90s as needed.

 

[Michael In Tennessee]

Just measure the IDs. They will easily flow more than a -6 fitting and that's all you need. If you use the fittings that I had linked to in the block, there is ZERO problem orienting 90s as needed.

Yes, but that extends the 90s further from the subplate making hose routing less tidy, as a minimum, and impossible at a maximum. I'll have to see if there is enough room. I haven't had a chance to get down to my supply house to measure fittings, but I'm surprised I can't find such info on-line.

 

[MtnViewRanch]

Here is another option, not recommended, but I have done it with no issues. Take the sub plate that you want to use and the -6 fittings and simply drill them out to -8 ID sizing.

 

[Michael In Tennessee]

Thought of that. Not sure of the prudence of that idea though. They have a wall thickness for a reason. It looks like the SAE fittings are rated for 6000 psi, so drilling them out for a sub-3K psi tractor would work. Oddly enough, NPTF fittings are rated at 3000 psi best I can figure. NPTF is adequate, but just so.