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

 

[R_Gator]

Just a thought here, but if you're not really comfortable working with the hydraulic circuit, you may want to consider using a linear actuator.. It wouldnt be as difficult to control as they move pretty slow, and could be easily wired to run off a momentary ON/OFF/ON toggle switch. Heres an example... www.firgelli.com/item35.htm

 

[boustany]

Thanks for the suggestion. In fact my first thought was to use an electrical system (I have a background as an electronics designer) and had thought up a lead screw system driven by a 12 volt motor (more or less a DIY actuator).

But I want to get familiar with hydraulics, and this would be a way of getting the toes wet. /forums/images/graemlins/smile.gif

 

[keeney]

If a cylinder is rated for 2500 PSI, it will likely have no problem being bottomed out at either end of its stroke with moderate flow of under 10GPM at its full rated pressure for many thousands of cycles.

The relief valve should actuate fast enough to avoid too much of a pulse in the system. The rest of the system other than the cylinder is already taking this same pressure pulse when you hit the limit on the FEL, or any other hydraulic system connected to the same control valve.

You already have the right idea that whatever stops the motion has to be beefy enough to stand up to the force of the cylinder at full relief pressure. If your sheet-metal deflector was trying to stop the cylinder before it bottoms out, the deflector will bend before the pressure relief kicks in.

You can also get spacer ringsand/or adjustable threaded spacer rings to fit over the rod of the cylinder so that you can limit its stroke by bottoming out on the spacers instead of bending the deflector, but generally, the mechanism should be designed with the stroke and length of cylinder you plan to use in mind from the start.

The reason the hydraulic motor could not be connected to the FEL control is a mystery to me. The only thing I can think of is that maybe the FEL has too high of a relief setting?

Sometimes, you want a "motor" control valve to run a motor, but this is when you plan to leave the motor running for a while (like on a trencher, perhaps) and you want detents to hold it on for you. Also, for a high flow motor, the flow rate rating of a FEL control valve might not be high enough. Both of these are not issues in the case of using a small hydraulic motor to intermittently turn a chute.

In fact, I would think you would want the fine metering that is designed into a FEL joystick.

Also, having the rotation and elevation angles on the same joystick (connected in the right orientation and polarities) would make aiming the snow in the two directions a lot easier than having two different handles to mess with in perhaps awkward directions.

- Rick

 

[boustany]

Thanks, Rick, I think I understand now.

I have found an almost perfect cylinder for the job that will bottom before bending the deflector. I believe the pressure for the FEL is limited to 2500 PSI, so I should be ok.

As for the motor, the original idea was for the dealer would set it up to use the FEL control it. They apparently tried and tried and it wouldn't work. So, they tied the rotator into my rear remote, which is kinda goofy. If I had a choice the chute motor and my deflector would use the FEL control as you suggest and the lift of the blower would be controlled by the remote.

But thats the way it is. Somebody suggested that the hydraulic needs someplace to go, but the remote only has 2 hoses too, just like the FEL.

I was a little disappointed that Kubota/the Dealer couldn't make it work. I doubt I'm the only 3010 with a front mount.

 

[keeney]

Some hydraulic motors cannot handle any kind of pressure on the return side. Others can handle the pressure but have a case drain that needs to be be returned to the suction side without going through the SCV. If the SCV is putting any kind of restriction on the return side, it might cause the motor to leak a little, but I can't imagine that it wouldn't "work".

Maybe the SCV flow was too slow?

- Rick

 

[boustany]

Rick:

Interesting point. It could be that my dealer was just making up an excuse for the delays (10 days turned into weeks and weeks).

I must admit, hydraulics are a bit of a mystery to me, I mean with loaders having different types of controls, etc..

Maybe what I'll do one day is try hook up the chute rotator myself and see what happens.