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.

 

[Michael In Tennessee]

Brian, I assume you have no issues with the work ports regardless of what size fittings I use.

 

[/pine]

FWIW...it can be worth consideration to save some money on hoses to use NPSM female pipe swivel fittings/adapters in place of more expensive JIC hose ends...

The swivel fittings come in all the same typical port thread/seal types (SAE etc.) with the angles etc on the fitting/adapters rather than the hose ends...they allow the use of all straight end NTP hose ends...they are a mechanical type 30* chamfer connection no sealant or thread compound required (same as JIC)
Makes measuring and ordering hoses a breeze...

 

[MtnViewRanch]

Brian, I assume you have no issues with the work ports regardless of what size fittings I use.

Correct, work ports will make no difference. Short term flow is of no consequence.

 

[N2DFire]

I'm asking out of pure curiosity (not because I'm trying to be an @$$ - which some would say is vastly out of character for me. LOL) because I'm sure Brian has dealt with more hydraulics this month than I have in a lifetime.

Why so much concern over the inner port diameter between -6 (3/8 or .375 inch) and -8 (1/2 or .500 inch) when the valve itself and the mating ports on the D03 subplate are 7.5 mm max (or .295 inch)?
https://www.sis.se/api/document/preview/603865/

My understanding is that (compared to the length of the entire system) the very short "length" of restriction while flowing through the subplate and valve body itself was considered negligible, if this is true then why not the same for the fittings? I also understand that in series ("stacking") of these reductions has a cumulative effect, but is it really that great?

I further confess I haven't looked at any charts, graphs, or calculations since I took fluid mechanics back in the '90's so I may be totally off base.


In my build, I used the D03 plate with NPT 06 connections and NPT fittings with swivels (BIG MISTAKE) but I had more room to work with. If I knew then what I know now I would have used NPT to JIC adapters in the subplate and JIC fittings on the hoses.

I did use 1/2" hose (with 3/8" fittings) for the lines on the P & T of the Subplate for constant flow and 3/8" hose & fittings for the intermittent flow work ports.

 

[MtnViewRanch]

I'm asking out of pure curiosity (not because I'm trying to be an @$$ - which some would say is vastly out of character for me. LOL) because I'm sure Brian has dealt with more hydraulics this month than I have in a lifetime.

Why so much concern over the inner port diameter between -6 (3/8 or .375 inch) and -8 (1/2 or .500 inch) when the valve itself and the mating ports on the D03 subplate are 7.5 mm max (or .295 inch)?
https://www.sis.se/api/document/preview/603865/

My understanding is that (compared to the length of the entire system) the very short "length" of restriction while flowing through the subplate and valve body itself was considered negligible, if this is true then why not the same for the fittings? I also understand that in series ("stacking") of these reductions has a cumulative effect, but is it really that great?

I further confess I haven't looked at any charts, graphs, or calculations since I took fluid mechanics back in the '90's so I may be totally off base.


In my build, I used the D03 plate with NPT 06 connections and NPT fittings with swivels (BIG MISTAKE) but I had more room to work with. If I knew then what I know now I would have used NPT to JIC adapters in the subplate and JIC fittings on the hoses.

I did use 1/2" hose (with 3/8" fittings) for the lines on the P & T of the Subplate for constant flow and 3/8" hose & fittings for the intermittent flow work ports.

As far as the DO3, plate, I think that I mentioned something about drilling the ports out also?

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.

I suppose that it wouldn't make much difference if you were a person that didn't use much more than 1/2 throttle most of the time. What I do know is that I have seen a 16GPM aux valve burn up a 17GPM pump. I had a customer that burned up 3 pumps on an MX5100, which turned out to be a flaw in the internal plumbing of the tractor's main case.

These failures ended up costing a lot of money and time for something that should have been easily avoidable if the proper parts would have been used.

If you are a person that uses their equipment pretty much to max more than half of the time, these small under sizings can make the difference between longevity and equipment failure.

Just my :2cents:

 

[LD1]

FWIW...it can be worth consideration to save some money on hoses to use NPSM female pipe swivel fittings/adapters in place of more expensive JIC hose ends...

The swivel fittings come in all the same typical port thread/seal types (SAE etc.) with the angles etc on the fitting/adapters rather than the hose ends...they allow the use of all straight end NTP hose ends...they are a mechanical type 30* chamfer connection no sealant or thread compound required (same as JIC)
Makes measuring and ordering hoses a breeze...

Why do you say the NPSM fittings are cheaper?

Everytime I have compared.... they are the same or a mere pennies different

 

[LD1]

What is your definition of a "good" price?

Is $70 a "good" price?
AD3SPS8S DAMAN. ALUMINUM VALVE SUBPLATE. DAMAN AD3SPS8S. | Trausch Dynamics

 

[Michael In Tennessee]

What is your definition of a "good" price?

Is $70 a "good" price?
AD3SPS8S DAMAN. ALUMINUM VALVE SUBPLATE. DAMAN AD3SPS8S. | Trausch Dynamics

+$20 shipping.

Surplus Center has the -6 ORB D03 subplate for $35. Shipping is basically buried in the larger order I need to place. I have lived my whole life optimizing prices. It is very hard to "just do it" when I buy stuff. Character fault, but that is me.

 

[LD1]

+$20 shipping.

Surplus Center has the -6 ORB D03 subplate for $35. Shipping is basically buried in the larger order I need to place. I have lived my whole life optimizing prices. It is very hard to "just do it" when I buy stuff. Character fault, but that is me.

~$75 shipped is about the best I can find delivered. AD3SPS8S - D3 Subplates - Daman | Hydradyne LLC

I am frugal too and always looking to optimize my dollar. If you cannot make NPT work with adapters and a JIC swivel (which will add to your $35 subplate)......then Im at a loss.

At some point.....it just isnt worth the time/effort to squeeze the last few pennies out of a build.

Have you looked into other options? Cartridge valve? Diverter? D05?

 

[Michael In Tennessee]

~$75 shipped is about the best I can find delivered. AD3SPS8S - D3 Subplates - Daman | Hydradyne LLC

I am frugal too and always looking to optimize my dollar. If you cannot make NPT work with adapters and a JIC swivel (which will add to your $35 subplate)......then Im at a loss.

At some point.....it just isnt worth the time/effort to squeeze the last few pennies out of a build.

Have you looked into other options? Cartridge valve? Diverter? D05?

Analysis Paralysis. Part of my nature.

I can use NPT, just don't like 'em. I think I found a rear port D03 subplate in NPT. That eliminates lots of elbows and makes things neat and tidy. I'd just have to suck up my aversion to NPT. I'll have to go out to the tractor and see if hose routing works. The bracket would be a tad more difficult to make since it involves drilling big holes in steel plate. Should be able to use a bi-metal hole saw though.

I have some travel coming up for the holidays, so I won't start in earnest until first week of Jan. I can't guarantee I'll be home for part deliveries.