Hydraulics questions

[boustany]

So, its labor day, which for a Canadian means winter is just around the corner.

One project I've been thinking of is converting the deflector on my Kubota Front Mount Blower to remote control (I have to change the angle a fair bit when I blow).

Now, I looked at electric, but its clear to me the thingy is designed so a small hydraulic cylinder can take the place of the rod they've got there.

I've never done hydraulics before, so here are my questions:

First, I figure I need a 12" (retracted) cylinder with a 4" (or 6") stroke. I've found one with a 1" bore, but it is rated 2500 pounds, which I figure is less than the pressure of my tractor hydraulics. Will I need a relief valve?

Second, the folks who did the installation had to use my remote to control the chute rotator motor because the FEL control somehow wouldn't work with a hydraulic motor. (I really don't understand why). Anyhow, that leave the bucket dump (i.e. left/right) of the FEL control free. Is there any reason why this wouldn't work on my deflector cylinder?

 

[jmc]

Brian,

It takes about 3200 psi to get 2500 lbs out of a 1 inch bore. That's probably less than your relief pressure of your tractor. Whether or not your chute mechanism will take 2500 lbs may be the question.

John

 

[Junkman]

Which one of your tractors is this going to go on????? /forums/images/graemlins/confused.gif

 

[boustany]

First, its going on my 3010.

My concern is for the cylinder, not the chute mechainism, which is mostly 1/8 mild steel.

If I chose the cylinder right, it's stroke will end before it noshes up the chute. I guess the question should have been does the cylinder have a built in protection mechanism.

 

[jmc]

Brian,

What I meant to say above is that your tractor probably doesn't develop 3200 psi so you will be under 2500 lb. Find out what your max pressure is in psi and multiply it by .785 square inches (for a 1 inch bore) to get cylinder force. And ask the vendor if the cylinder can be bottomed out as long as you stay below the 2500 lbs.

Maybe someone will chime in here that knows how to size flow restrictors. They keep the cylinder from slamming open so you have time to stop them to control position or keep them from instantly developing full pressure. The impact resulting from full flow into a tiny cylinder may be the most harmful.

John

 

[boustany]

Thanks!

 

[R_Gator]

I think some of the confusion your having has to do with the cylinders rating of 2500 Lbs. Did the supplier say it was 2500 Lbs or 2500 PSI? The force created by a cylinder is equal to its surface area multiplyed by the maximum obtainable pressure (Force=Pressure X Area)... Keeping in mind that pumps produce flow (not pressure) the pressure in the circuit is going to be determined by the force required to move the deflector, but here again.....the rod end of the cylinder is going to have a smaller effective rod end area, so its going to take more pressure to retract the cylinder than it will to extend it. You mentioned that the "thingy" is small, so I doubt its going to take anywhere near the full relief valve pressure setting on the existing valvebank to move the cylinder, but keep in mind that the circuit will reach the relief valve setting once the cylinder "bottoms out" (fully extended or retracted). I agree with Brian that the size of the cylinder is going to make it difficult to control, but calculating the orfice size is going to be tricky, as it will not only depend on the actual pump flow, but also if you have the cylinder mounted on a pivot... here again becuase of the effective rod end area vs. the blind end area, the cylinder will retract faster than it extends. Im betting that the valve section used to operate the bucket dump is an infinate postioning valve, meaning you can somewhat control the speed of the cylinder by how far you move the lever.. If it were me, and I had the cylinder in my posession, I would (without physically mounting it) attach the hoses from the bucket to the cylinder and seeif you can safely control the speed using the lever on the valvebank, if not... they sell fittings with orifice holes installed on the ends that would work well.. As far as not being able to use the regular valve bank to power the rotator.. Im guessing they figured that: things in motion tend to stay in motion, so using a closed center valve (the ones usually used on cylinders) wouldnt allow the oil to circulate once you shut the rotator off, and you would blow a hose (if your lucky) or damage the hydraulic motor and/or valvebank (if your not so lucky).. Dont know if this helps, but... thats my take on it.

 

[boustany]

Aha! I guess I misspoke (miss wrote?) when I said it was 2500 pounds. You are correct: it is rated 2500 PSI.

My concern is primarily 'blowing' the cylinder. It only has to push a few pounds, and even with all the snow it'll probably only have to hold a hundred pounds or so pressure. I am pretty sure the cylinder will be fully extended or bottomed without being limited by the mechanism, so if I push the control the wrong way and its bottomed, or fully extended, I don't want to blow the cylinder.

 

[R_Gator]

Im not familliar with your equipment, so cant tell you where the releif valve is set, but we know there has to be one.. With the exception of hydrostats, most mobile hydraulics dont run much over 2500-2800 PSI, so I would figure your ok... Probably the best way to know is to just remove the hose from the one of the bucket cylinders... cap the hose with a 0-5000 PSI gauge. Start the engine and move the control lever.. Wherever the gauge lands is where your R/V is set. *Keep in mind if you move the lever the wrong way you might get wet, so make sure your moving the directional control valve so its directing oil towards the hose you have capped. You're not going to hurt anything capping the hoses to the cylinder as they're protected by the relief valve, but generally speaking its best to tee in a gauge when checking pressures, as you know you cant cause trouble.. If you dont have a gauge, you might be able to borrow one from the local implement dealer where you get your parts... Good Luck with your project!

 

[markct]

you can buy a gauge for less than 20 bucks from MSC or probably McMaster-Carr also, we got one from MSC for checking the relief valve on our loader backhoe, it was liquid filled to prevent shock damage also