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Old 05-03-2007, 09:18 AM   #1
TreeFarmer OP
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Hydraulic Help Needed

Was not sure where to go with this question then thought who better than the good folks on ADV rider. If you have ever read my profile you know that one of my things is growing Christmas Trees. Like most people here in the garage, I like to do a lot of things myself & I love a good project. Well I bought myself a new project and have started to work through some of the issues but need a little help with design of a hydraulic system.

I bought a Christmas Tree loader a couple of weeks ago. It's really nothing more than a glorified hay elevator on wheels. I bought it as a starting point. It was in no way what I was looking for but new ones are a little too expensive and you never find a decent used one, so I bought a crappy used one with the intention of completely rebuilding it and re-engineering it. It had been gas driven via belt drive and I am converting it over to a hydraulic drive and going to use the hydraulics to take care of at least one other function on the loader. I will also be converting the former chain 2 section conveyor to a belted 1 section troughed conveyor, but that is neither here not there as I have that part all figured out. What I need help with is the hydraulics...

So really the system is not too much more than a log splitter when you come right down to it. So here is what I have and what I am trying to do. I have a 5.5hp Honda GX160 engine coupled to a 11 GPM Haldex 2 stage hydraulic pump. As I said before I am looking for this to power to functions. First is to power the conveyor. For this I have a Parker hydraulic motor (head drive if you are really into this kind of thing & are curious). I will probably use a #50 chain to make the final drive connection. To actuate this function I was planning on using a ball valve as it would either be on or off, no need for anything fancy here. The second function the power plant will handle is a pair of lift cylinders. I would like to control both up & down going forward. Right now they are single acting and actuated by a hand pump & a small reservoir and a manual one way shut off valve to keep the pressure in the system and the cylinders extended. So here is where my questions begin.... I would like to use a valve similar to one found on a log splitter, but the cylinders are single action. I see where there is a closed off plug at the bottom of the cylinder, can I simply remove the plug and "wala" have a double acting cylinder or what I am probably thinking is I am going to have to have it rebuilt? The biggest problem I can't work out in my head is the plumbing. I can add a schematic to this thread if a pic would help someone. The crux of my problem has to do with the pressure and fluid running through the hydraulic pump when the end power points are not in action yet the gas engine is running and pump is, well, pumping. How do I divert this to the reservoir and then still be able to actuate my power points when I need to? I also may be using the pump to handle a couple of other functions including a front end trailer jack type lift and maybe a drive wheel. This all depends on how complicated I want to make this. None of these items would really be running at the same time so having enough power should not be an issue.

Any help MUCHO appreciated.

T
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Old 05-03-2007, 02:33 PM   #2
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Quote:
Originally Posted by NX650Rider
. . a pair of lift cylinders. I would like to control both up & down going forward. Right now they are single acting and actuated by a hand pump & a small reservoir and a manual one way shut off valve to keep the pressure in the system and the cylinders extended.

. . the cylinders are single action. I see where there is a closed off plug at the bottom of the cylinder, can I simply remove the plug and "wala" have a double acting cylinder . . ?

The crux of my problem has to do with the pressure and fluid running through the hydraulic pump when the end power points are not in action yet the gas engine is running and pump is, well, pumping.

How do I divert this to the reservoir and then still be able to actuate my power points when I need to?
If the actuator is a single-action design then it usually has only a dust seal around the shaft. A dual-action actuator has a pressure seal at the shaft end of the cylinder. A dual-action will also have a fluid input port near the open end.

Instead of buying dual-actuators, can springs be used to retract the mechanism? Or if you need power in both directions, can you mount an opposing cylinder? I know that raises the cost, but maybe you are using 'commodity' single-action actuators. And I believe that a pair of those commodity items, mounted in a complimentary push-push mechanism, are much less costly than a dual-action component.

Maybe think about the fluid path as a free-flowing 'full recirculation' system. When the motor and pump are running, fluid is re-circulating freely in a series circuit running from the pump output, through the hand-operated valves, and back to the reservoir.

When the valves are not in use, they are in the 'open' or 'full bypass' position say.

When a hand-operated valve lever is moved, the fluid path through the valve progressively changes from 'full bypass' to full- . . ahh . . heck I can't imagine what that term might be. But instead of bypassing the fluid, the valve directs it to the desired actuator.

As you can see I don't know the jargon. But while growing up I was lucky enough to live a few houses down from a Massey Ferguson tractor factory repairman. And his garage door was always open.

- Jim

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Poolside screwed with this post 05-03-2007 at 04:52 PM
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Old 05-03-2007, 09:49 PM   #3
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That is a big question. I do not believe that you should start with the engine though, with an unknown load.

Its been a while since I've messed with them, but I believe the "crux" of your situation is just an open center (or was it closed center.....wtf) hydraulic system. That is how they are designed to operate.

We have a store near us (Tulare, CA) called Hydraulic Controls, Inc. and those guys pull slide rules out of their asses to make sure that pump rates, engine RPM, gear reduction, motor, and ram volumes all jive with each other. These guys are pro's who make the fabrication game much easier. I am sure that there is a similar retailer in Oregon.

Happy fabbing,


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Old 05-04-2007, 07:14 AM   #4
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Thanks for the replies they have helped.

First I wanted to say that We do have several hydraulic suppliers here locally that I know could help. I have been able to source most of my parts/supplies via Flea Bay at far superior prices so I have avoided wasting those guys time since I have not bought anything from them. Looks like that might change...

Poolside: I like the ingenuity of your idea using two cylinders to achieve the same outcome. I think I will just stick with my original plan of having double acting cylinders, it's just easier even if I do have to spend a little more to get them rebuilt, it will save in the long run. Your point about the open system was what I was thinking. The Hydraulic valves I have been looking at buying have a "normally open" center position. This would give me the free flow you talked about.

I still have a few questions, so it looks like I am going to spend some money and get some advice at the local hydraulic shop. Not the worst thing in the world.

Thanks again guys, I will post a pic or two when I get done.
T
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Old 05-04-2007, 08:41 AM   #5
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www.surpluscenter.com

sometimes has really good prices on valves and cylinders.

Be careful with double-acting cylinders on the height adjustment. Power-down can be a really dangerous thing in the wrong hands.

You sound like you are on the right path--sourced most of your high dollar stuff fleabay, then head to the local shop for valving and hoses. They can also help you with reserve capacity and coolers. Hyd. motors really heat up the fluid--you will want some cooling if you intend to run this thing for a while at a stretch.
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Old 05-04-2007, 09:00 AM   #6
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Hydraulic Stuff

http://www.northerntool.com/webapp/w...tegory_6970_96

Try this link for some stuff ya might need.
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Old 05-08-2007, 08:47 AM   #7
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Here is a very basic schmatic of the sytem I am designing. The Hydraulic motor should be 293 cubic cm dispacement per revolution & the max rev's per minute is 193
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Old 05-08-2007, 01:07 PM   #8
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Quote:
Originally Posted by NX650Rider
Here is a very basic schmatic of the sytem I am designing
Displacement ratios are identical to gear or sprocket ratios. You know, just like a moto chain. And just like a moto chain ratio, the output shaft sprocket turns faster than the wheel sprocket.

Applying the 'chain and sprocket' analogy to the components in the drawing there is a choice of two 'output shaft' sprockets at the Haldex pump, 3.5 'teeth' or 11 'teeth'. And the Parker motor 'wheel' sprocket is 17.9 'teeth'.

Consider the displacement in gallons (or any other unit) just like sprocket teeth. In your Christmas tree machine, the conveyor drive ratio is either 3.5/17.9, or 11/17.9, in decimal form the reduction ratios are .196 and .615

The ability of the pump to over-speed the motor is a design consideration. I'm thinking that the Honda gasoline motor operates at 3600rpm. The drawing shows the Parker hydraulic motor has a max rpm of 293. Multiply 3600rpm by either reduction ratio, and both results exceed the 293rpm maximum.

Maybe you can turn the Haldex pump with a 1/3 reduction vee-belt drive. That results in 235rpm at the Parker motor.

- Jim

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Poolside screwed with this post 05-08-2007 at 01:13 PM
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Old 05-09-2007, 09:18 AM   #9
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Quote:
Consider the displacement in gallons (or any other unit) just like sprocket teeth. In your Christmas tree machine, the conveyor drive ratio is either 3.5/17.9, or 11/17.9, in decimal form the reduction ratios are .196 and .615
So if I follow what you are saying here, even though the MAX possible flow rate out of the pump is 11 GPM & the Max possible flow rate for the motor is 12 GPM, I might be sending too much fluid to the motor? If I am correct, I would think this would only cause the motor to possibly spin at a slower rate of speed, which in my application would not be a problem. I WOULD think that the ability of the pump to produce more PSI than the pump is rated for might be a problem. The only reason it could possibly not be is that the flow rates are greater in the motor than the pump and it could never create enough flow & in turn create the higher PSI to cause a problem. Any real problem with PSI should be able to be delt with.

Quote:
The ability of the pump to over-speed the motor is a design consideration. I'm thinking that the Honda gasoline motor operates at 3600rpm. The drawing shows the Parker hydraulic motor has a max rpm of 293. Multiply 3600rpm by either reduction ratio, and both results exceed the 293rpm maximum.

Maybe you can turn the Haldex pump with a 1/3 reduction vee-belt drive. That results in 235rpm at the Parker motor.
Considering this is a hydraulic system not direct drive motor to application the buffering of the fuild would/should eliminate "over-speeding" The Honda engine would be hooked up to the hydraulic pump (both rated to max 3600 RPM's)... Fluid flows to the hydraulic motor and the fluid turns the hydraulic motor. The speed of the hydraulic motor is driven by the flow rate of the fluid to this motor not the speed of the Honda engine. That is unless I am truly kidding myself about the little I do know about hydraulics. Any posibility of over-powering the Parker Hydraulic motor should be able to be compensated by a preassure releif valve or something of that nature.

Thanks for the input and keep it coming. More ideas are better than a few. My real question is about controls. I think I have the hydraulic lift cylinder figured out, using a 3-way spool control valve. If that is confirmed, then the only real problem left is actuating the hydraulic motor.

I do like pictures, so here is a pic of the item I am working on just to add a little color to the thread.
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Old 05-09-2007, 01:29 PM   #10
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Quote:
Originally Posted by NX650Rider
If I am correct, I would think this would only cause the motor to possibly spin at a slower rate of speed
That is exactly what I was saying. Consider the pump displacement ratio as the equivalent of the ratio of the number of sprocket teeth, as in a chain drive on a motorcycle. The 'sprockets' are the displacements of the pump and motor.

The front sprocket choice in your system is either 3.5 or 11
And the rear sprocket is 17.9

If the 3.5 sprocket is turning at 3600rpm, the 17.9 sprocket is turning at 704rpm.

The hydraulic motor is a 293rpm max. To reduce the overspeed, a 1/3 vee-belt drive reduces that to 235rpm.

. . . Also, say the speed is reduced by a 1/3 drive, still, 235rpm may be too fast for use as a conveyor drive.



Quote:
Considering this is a hydraulic system not direct drive motor to application the buffering of the fuild would/should eliminate "over-speeding" The Honda engine would be hooked up to the hydraulic pump (both rated to max 3600 RPM's)
I think the Honda motor makes it's rated HP at 3600rpm. And at 3600rpm, the components in the system overspeed the hydraulic motor.



Quote:
I WOULD think that the ability of the pump to produce more PSI than the pump is rated for might be a problem.
It might be, but the system pressure is caused by load. If there is no working load, like if the conveyor isn't lofting a tree, then the system pressure will be very low. And if the conveyor or ram aren't in use, then the system pressure is even lower, and is only as high as the fluid friction in the plumbing and valves.

- Jim

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Old 05-10-2007, 11:21 AM   #11
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Bare with me while I work through this & yes I do appreciate the pushback as it makes me sharpen my pencil again and make sure I am not missing something. I am going to start at the front end of the system and work forward.

Quote:
I think the Honda motor makes it's rated HP at 3600rpm. And at 3600rpm, the components in the system overspeed the hydraulic motor.
Apples & Oranges, I think we are both looking at different things here. I am looking at this as the Honda power plant powering the hydraulic motor only. We can get into the hydraulic motor in a bit, But theses two components are completely compatible and match up perfectly. I didn't put the specs of the Honda engine down, but trust me on this one.


Quote:
The front sprocket choice in your system is either 3.5 or 11And the rear sprocket is 17.9If the 3.5 sprocket is turning at 3600rpm, the 17.9 sprocket is turning at 704rpm.

Again I think we are looking at Apples & Oranges. The 17.9 displacement is cubic inches per rotation, I am not sure I made this very clear in my schematic. The 3.5 or 11 is gallons per min. So if I do the conversion, the 17.9 would equate to 0.0774892 gallons per rotation. Considering the max output of the pump is 11 GPM, the max possible rotation for the hydraulic motor would then be 141.95 revs per min (11/0.0774892 both figures now in gallons) and would never come close to the 193 max capability. Note here, I did screw up, the 293 figure is cubic centimeters displacement per rotation. The max motor rotation is 193 rev/min. Rotation would be slower under load if the pump went into high pressure 3.5 gpm. In that scenario, the hydraulic motor would only spin at a max of 4.52 revs per min... What I really need to do is understand how much load the motor will be under so I can have a good idea as to how fast the motor will rotate and I can get the gearing correct. The Hydraulic motor will use some sprockets and either #50 or #60 roller chain to drive the head roller.

Let me know what I am missing... I'm sure there is something.
T
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Old 05-10-2007, 02:03 PM   #12
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Quote:
Originally Posted by NX650Rider
Note here, I did screw up, the 293 figure is cubic centimeters displacement per rotation. The max motor rotation is 193 rev/min.

The 17.9 displacement is cubic inches per rotation, I am not sure I made this very clear in my schematic.
Nor was I clear in my understanding.

- Jim

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Poolside screwed with this post 05-10-2007 at 03:08 PM
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Old 05-10-2007, 02:56 PM   #13
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Looking at your diagram, You CANNOT simply shut off the fluid flow in a hydraulic systen. I MUST be either an open center or a closed center system. Most are open center , which is the most economic & user freindly. If you have a hydraulic shop locally I am sure they could give you a plan & cost at no charge.
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Old 05-10-2007, 03:03 PM   #14
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Quote:
Originally Posted by GSrider2
Looking at your diagram, You CANNOT simply shut off the fluid flow in a hydraulic systen. I MUST be either an open center or a closed center system. Most are open center , which is the most economic & user freindly. If you have a hydraulic shop locally I am sure they could give you a plan & cost at no charge.
Yea, it seems like the op is having fun with us.

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Old 05-10-2007, 03:42 PM   #15
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If I can find my textbooks I'll chime in on the formulas,, but open center is the way to go, also do not have the shut off valve on the feed to the pump, if its at high rpm and cavitates/creats vacuum in the intake,, it aint perty!
Good luck,
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