Rear hydraulic on Kubotas the less expensive way

[JerryG]

Re: Rear hydraulic on Kubotas the less expansive way

<font color="blue"> The 2 parallel surfaces of the mounting block must be symmetrical with each other so that the clamping pressure of the bolts exerts equal pressure over the whole surface of the "O" rings. Any surface irregularities in the mating surfaces would negate this uniform pressure. I am familiar with the mounting block itself and the mating surface is machined to a high degree of flatness. </font>
In your first post you also stressed that a surface grinder was required. Look at this picture. Those are mill marks. You don't get them from a surface grinder. This is a similar housing cap.

 

[BBELL]

Re: Rear hydraulic on Kubotas the less expansive way

So Jerry, are you saying that you don't have to be real true on the surface, just reasonably smooth? If so Mr. 5030 is a little bit extreme? I think I'm reading this right.

 

[JerryG]

Re: Rear hydraulic on Kubotas the less expansive way

It needs to be reasonably flat, but doesn't need to be as smooth of a finish as a surface grinder gives. A quick mill job is enough, like in the picture. The point is that the surface doesn't interfere with the o-ring seal and clamps even. Mill marks are fine.

 

[AV8R62]

You have done nearly the exact same I intend to do
I have 25 years machine shop experience and a lifetime of farm experience.
with an o ring seal surfaces don't need to be anymore flat than
CRS steel comes and doesn't need to to be paralel at all.
A static o ring is very forgiving on both depth and diameter.
it's a great idea. /forums/images/graemlins/smile.gif

 

[techman]

Re: Rear hydraulic on Kubotas the less expensive w

I want to add my 2 cents as well. I have worked for one of the largest hydraulic OEMs in the world for 27 years. A good weld (even a lowly stick weld) will hold 2100 psi and it will hold 5000 psi. The only time we NDT inspect welds is upon customer request or requirement. While anyone can make a bad weld, getting one that is porous to fluid is a really bad weld.

As for the story of fluid penetrating the skin, it is nearly an urban legend. The most common cause is when there is a hissing leak and some less than gifted individual runs his finger over the pressurized joint to try to find a leak, as one would do on an air leak. If conditions are just right, the oil may puncture the skin and make a small blister below the skin, which drains almost immediately. It hurts, but not much else. Normally the oil stream spreads with distance from the pinhole and looses the pressure to do any damage. Stories of amputations are at best good fireside stories.

In most cases, homemade fittings like this will either work or leak right away. The leak may be from improperly sized o-ring pockets, lack of flatness on the mating surface, or a poor weld. When this happens the owner/builder hopefully notices the leak when he tests his invention, and corrects the problem before loosing the gallon or more of oil that could damage the pump.

The biggest concern is the bolts that hold the plate on. You should use a good grade high strength bolt, not just hardware store handyman grade. The hydraulic pressure creates forces based on the port diameter, which the bolt must retain. Use the origonal cover bolts as a guide.

Hydraulics is not anywhere nearly as dangerous as compressed gas, since it has little compressability and looses it's energy as soon as it leaks to an opening. One should be careful, but not scared.

paul

 

[5030]

Re: Rear hydraulic on Kubotas the less expansive way

Jerry:

Actually, that particular block was machined on a CNC mill using Tungsten Carbide tooling.

The block in the picture was not milled in the true sense of the word.

Because I am a Journeyman Tool and Die maker and I own my own machine shop coupled with the fact that I pride myself on accuracy, in a prototype or one off scenario, I would grind the mating surfaces.

In a production environment, the surfaces are probably fly cut, or shell milled. Nevertheless, if you were to gage the flatness of the piece on a surface plate, using a dial indicator with the block jigged properly, you will find that it's flat and parallel most likely within 0.001 or better.

You might get lucky and find a piece of old stock lying around somewhere that you could counter bore the "O" ring grooves in. I am not saying that it's impossible. What I am saying is that for the block to be leak free and the "O" ring seal to be secure, the clamping surfaces need to be parallel. The chance of picking up an old piece of rusty steel and transforming it into a leak free block with the tools lying around in your garage is a fantasy. Then you are faced with the problem of either welding on the outlet pipes or tapping the block to accept fittings. The welding scenario in a garage type environment with the trusty buzz box or the home Hobart MIG, leaves a porosity question, with the uncertainty of leaks at high pressure a hazardous question at best. The answer would be to tap the block, but then again, the local hardware store doesn't carry the type of taps necessary to thread the holes.

I don't think too many people on this site or for that matter the general public have at their disposal the type of machinery and tooling necessary to perform that task. An angle grinder and a cheap drill press isn't going to do it.

To give you some idea of the cost of a vertical miller alone, My Bridgeport cost over $14,000.00 and that's without tooling.

I could go on for pages about fit classes, tolerances and surface finishes and parallelism, but it's not germane here.

The bottom line is, from a personal safety standpoint, in regards to high pressure hydraulics, it is always better to err on the positive side rather than the negative.

In my opinion and again, my opinion only, you would be better off in the long run to purchase the block from the dealer.

The original poster stated that he fabricated the block at his place of employment, not at home.

 

[BBELL]

Re: Rear hydraulic on Kubotas the less expensive w

Thank you AV8R62, and techman for the support. I guess I'm not just a hic farmer that's been eating dust all day( I've got an air condition cab. LOL) As far as welding I do know alittle about it , I use to be a welding instructor in the ship yard I work in. There is close to 600 welders in this place , and probably some of the best in the country. My speciality was pipe welding. I'll bet my life and my dog, it won't leak. Techman beleive it or not I had a friend that lost a hand to a high pressure hydraulic leak. He did something stupid and ran his hand along a wet oily hose and in a split second his hand was filled with fluid and 2 years later it had to be amputated. So it is dangerous.

 

[5030]

Re: Rear hydraulic on Kubotas the less expensive w

techman:

My 2 cents to you is that you'd better brush up on your SAE specifications and maybe quit reading the sports page in the evening and grab a copy of Machinery's Handbook.

I personally witnessed the injection scenario and the subsequent amputation. For me, it's a grim reminder of what an inattentive moment can lead to.

When it comes to machining, particularly precision machining, nothing leaves my shop unless it's first class.

 

[JerryG]

Re: Rear hydraulic on Kubotas the less expansive way

<font color="blue"> Not stock flat, but ground flat and parallel. That takes a surface grinder which most home shops don't have. </font>
Daryl,
This is what you started out saying. Now it is milled or fly cut. Now milling is not milling. Get it straight. Yes I know what machines cost. I have programed and ran CNC mills. I also taught at a Technical school teaching tool room machining and die making. This is not something that is a NASA project on a shuttle. AND new members don't need to be nit picked to death. Most are to afraid of their hydraulic systems to try to modify it anyway. There are things that they need to learn before trying, but it is not brain surgery. With a little research, anyone or almost anyone can develop a more useful hydraulic system on their tractor.

 

[BBELL]

Re: Rear hydraulic on Kubotas the less expansive way

Jerry and 5030 I've got 2 pairs of boxing gloves, we can settle this once and for all.