Anonymous Poster
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Correction...Power-Trac will be at "nursery" trade show in Columbus..."CENTS" as Christy called it...NOT the Power Show.
Hoe
- Thread starter marrt
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OP
marrt
Platinum Member
Just out of curiosity, does anyone know the output rating (in gallons per min) of the PTO pump on the PT400’s? And what is to correct description for this type of pump. In other words, how would I describe this type of circuit? I remember reading somewhere that the output of this pump should not be interrupted. Therefore, I’m curious as to how I would describe this pump to the Cadplans folks if I were to inquire about using the PT hydraulics to drive one of their hoes.
davesisk
Platinum Member
Hey Marrt:
It's a simple gear-type hydraulic pump rated at 8 gpm @ 2500 PSI (or that's the rating on my 1418, I think it's the same for the 400's). The whole hydraulic system is "open-center" to my understanding, meaning that fluid is always flowing, valves just divert it.
HTH,
Dave
It's a simple gear-type hydraulic pump rated at 8 gpm @ 2500 PSI (or that's the rating on my 1418, I think it's the same for the 400's). The whole hydraulic system is "open-center" to my understanding, meaning that fluid is always flowing, valves just divert it.
HTH,
Dave
OP
marrt
Platinum Member
Thanks Dave. For some reason, I thought the 8 GPM was for the variable pump, not the PTO pump.
MossRoad
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- South Bend, Indiana (near)
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<font color=blue>does anyone know the output rating (in gallons per min) of the PTO pump on the PT400’s?</font color=blue>
There are two(or three, depending how you look at it) pumps on the 400 series:
One is the variable volume pump for the drive.
The second appears to be a two section pump on the back of the engine.(that's why I said three pumps; two sections on this one)<A target="_blank" HREF=http://users.beanstalk.net/godollei/pt425/PT425Pictures/PT425PTOPump.jpg> Here's a link to a photo of mine</A>.
You can see from the photo that the section towards the right has small hoses. This is the section that supplies the steering, lift rams and auxillary PTO that powers the quick attach cylinder. Or, by changing connections out front with quick disconnects, the power angle cylinder on a plow, broom, the open/closed cylinder on a grapple or the bucket on the mini hoe.
The section to the left has larger hoses. This section supplies the main PTO, which would power spinning motors on mowers, brush hogs, stump cutters, etc...
The auxillary PTO is operated by the two way lever in front of your right knee. Up moves cylinders one way, down the other.
Now this is the part that I don't understand. The main PTO is operated electrically. There is a switch on the dashboard. It is either on or off. Power Trac says not to operate the switch when no attachment is attached. How is the pump energized? If you look at the photo, and from what I can see, there is no electrical connection to that two section pump. There must be some sort of solenoid somewhere in there that lets the fluid run freely back to the hydraulic tank when the main PTO is not in use. Then, when you flip the switch, it must pull in a solenoid that sends fluid to the main PTO hoses. Therefore, no attachment on the main PTO = no flow if the switch is flipped = possible damage to the pump(at least that's my theory /w3tcompact/icons/clever.gif )
I spoke to someone at Power Trac before I bought my unit. They said that the unit could power a CAD Plans digger, as long as the digger used all open center valves. They did not say which PTO to use; the aux or the main.
Ed said he powers his backhoe off of the aux PTO and locks the knee lever in one position with some sort of lever holder(bungee cord?).
So that brings up several questions:
1. Is it possible to use the MAIN PTO to power a backhoe instead of the AUX PTO?
2. Does the MAIN PTO have more flow, but less power than the AUX PTO or vice versa?
3. Would we get better performance from a backhoe by running it off of the MAIN or AUX PTO?
4. What inside diameter plumbing would be needed on the backhoe and what GPM rating should it be?
I suppose this one warrants a call to Power Trac to find out just how this works and what to do.
What do you folks think?
There are two(or three, depending how you look at it) pumps on the 400 series:
One is the variable volume pump for the drive.
The second appears to be a two section pump on the back of the engine.(that's why I said three pumps; two sections on this one)<A target="_blank" HREF=http://users.beanstalk.net/godollei/pt425/PT425Pictures/PT425PTOPump.jpg> Here's a link to a photo of mine</A>.
You can see from the photo that the section towards the right has small hoses. This is the section that supplies the steering, lift rams and auxillary PTO that powers the quick attach cylinder. Or, by changing connections out front with quick disconnects, the power angle cylinder on a plow, broom, the open/closed cylinder on a grapple or the bucket on the mini hoe.
The section to the left has larger hoses. This section supplies the main PTO, which would power spinning motors on mowers, brush hogs, stump cutters, etc...
The auxillary PTO is operated by the two way lever in front of your right knee. Up moves cylinders one way, down the other.
Now this is the part that I don't understand. The main PTO is operated electrically. There is a switch on the dashboard. It is either on or off. Power Trac says not to operate the switch when no attachment is attached. How is the pump energized? If you look at the photo, and from what I can see, there is no electrical connection to that two section pump. There must be some sort of solenoid somewhere in there that lets the fluid run freely back to the hydraulic tank when the main PTO is not in use. Then, when you flip the switch, it must pull in a solenoid that sends fluid to the main PTO hoses. Therefore, no attachment on the main PTO = no flow if the switch is flipped = possible damage to the pump(at least that's my theory /w3tcompact/icons/clever.gif )
I spoke to someone at Power Trac before I bought my unit. They said that the unit could power a CAD Plans digger, as long as the digger used all open center valves. They did not say which PTO to use; the aux or the main.
Ed said he powers his backhoe off of the aux PTO and locks the knee lever in one position with some sort of lever holder(bungee cord?).
So that brings up several questions:
1. Is it possible to use the MAIN PTO to power a backhoe instead of the AUX PTO?
2. Does the MAIN PTO have more flow, but less power than the AUX PTO or vice versa?
3. Would we get better performance from a backhoe by running it off of the MAIN or AUX PTO?
4. What inside diameter plumbing would be needed on the backhoe and what GPM rating should it be?
I suppose this one warrants a call to Power Trac to find out just how this works and what to do.
What do you folks think?
MossRoad
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Hey, I was right! /w3tcompact/icons/laugh.gif
I went out and looked and here's what I found(I confirmed it in the Owner's Manual):
The little hose and big hose come out of the two pump sections as I described above. Then they both go into a silver block, called a valve body in the diagrams. On the valve body there are two relief cartridges(I'll assume one must be for each section of the pump). The valve body has an electric soleniod on it that must act as a diverter for the MAIN PTO as I thought. There are three hoses coming out of the valve body. Two hoses(a big one and a small one) go to the tunnel towards the front of the unit. The little hose goes to the steering unit(which then feeds the AUX PTO) and the big hose goes to the MIAN PTO connections out on the lift arms. The third is another big one that goes directly back to the hydraulic tank. So my guess is that the MAIN PTO pump is always pumping, it is just returning to the fluid to the hydraulic tank. When you flip the MAIN PTO electric switch, the solenoid must divert the flow to the hoses on the lift arms. I suppose the relief cartridge would save you if you accidentally turned on the MAIN PTO without an attachment hooked up, but it is probably hard on the system.
Again, I would like to hear from Power Trac as to which PTO would run a back hoe better. Maybe I'll call them sometime this week while I'm at lunch. I'll let you all know what I find out.
I went out and looked and here's what I found(I confirmed it in the Owner's Manual):
The little hose and big hose come out of the two pump sections as I described above. Then they both go into a silver block, called a valve body in the diagrams. On the valve body there are two relief cartridges(I'll assume one must be for each section of the pump). The valve body has an electric soleniod on it that must act as a diverter for the MAIN PTO as I thought. There are three hoses coming out of the valve body. Two hoses(a big one and a small one) go to the tunnel towards the front of the unit. The little hose goes to the steering unit(which then feeds the AUX PTO) and the big hose goes to the MIAN PTO connections out on the lift arms. The third is another big one that goes directly back to the hydraulic tank. So my guess is that the MAIN PTO pump is always pumping, it is just returning to the fluid to the hydraulic tank. When you flip the MAIN PTO electric switch, the solenoid must divert the flow to the hoses on the lift arms. I suppose the relief cartridge would save you if you accidentally turned on the MAIN PTO without an attachment hooked up, but it is probably hard on the system.
Again, I would like to hear from Power Trac as to which PTO would run a back hoe better. Maybe I'll call them sometime this week while I'm at lunch. I'll let you all know what I find out.
OP
marrt
Platinum Member
Ok, this is starting to make sense now (after all, its only plumping, right?). MR, while I was reading your most recent response to my most recent question, I was thinking about that valve body you mention in your subsequent post. Coincidentally, I had already gone over to your site earlier today and looked at the picture you linked (after all, you have a great picture and I’m too lazy to get up and go look at the tractor itself). I remembered when you first put that picture up that one hose was bigger than the other one and I assumed at that time what you have now confirmed. (As a side note, its good to know that the fluid does circulate through the hydraulic reservoir whenever the engine is running. I was reading the post about cavitation on cold start, which I have experienced myself, and was concerned that starting the tractor would do little to get the hydraulic fluid to warm up.)
Thinking about it for a moment, I imagine most of the less expensive hydraulic setups (e.g., log splitters and the like) probably use a continuous hydraulic loop where the pump is always pumping. This is probably the most economical and simplest setup. The creative use of valves would allow one to “tap into” the hydraulic flow as necessary. If true, then the valves on the Cadplan’s machines may already be designed for this type of design. I notice that the model 821 recommends an 11 HP engine with a 6 GPM pump. If the PT main PTO puts out 8 GPM, then we are all set. Of course, all of this needs to be confirmed.
Moss, I will call Cadplans and try to confirm that the “continuous loop” (open center) hydraulic setup will work with their designs. I’ll post what I learn.
Thinking about it for a moment, I imagine most of the less expensive hydraulic setups (e.g., log splitters and the like) probably use a continuous hydraulic loop where the pump is always pumping. This is probably the most economical and simplest setup. The creative use of valves would allow one to “tap into” the hydraulic flow as necessary. If true, then the valves on the Cadplan’s machines may already be designed for this type of design. I notice that the model 821 recommends an 11 HP engine with a 6 GPM pump. If the PT main PTO puts out 8 GPM, then we are all set. Of course, all of this needs to be confirmed.
Moss, I will call Cadplans and try to confirm that the “continuous loop” (open center) hydraulic setup will work with their designs. I’ll post what I learn.
MossRoad
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Cool! Now I'm going to bed /w3tcompact/icons/smile.gif
Anonymous Poster
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hey moss -
i have the same similar questions as you do - but i do have a few answers - i hope anyone else out there could chime in like Duane
I know that the Aux has a lower GPM output - not sure why - could be the pump - could be hose size since this pump needs to supply to more than just the Aux PTO (ie steering and lift)
the main PTO is 8gpm and the Aux is 3-4 i think - I don't think you need as much GPM for lift (or backhoe) as you do to run attachment motors - (of course at the size we are talking about) - the pressure needs to stay up though
my backhoe has more than enough power with the AUX - the hydraulics are stronger than the weight of the machine - you would not want an 8gpm backhoe on there - as it is it drags the machine around in heavy digging
even if you look at the large skid steer backhoes - the gpm requirements are 6-8 and these are far too big for the 400 series - some weigh over 1750 lbs without a bucket or dirt in the bucket
- so i would imagine that you would use the Aux for any home made unit - unless you use a diverter of some sort for the main PTO to reduce the output -
I wanted to add an additional Aux ouput that you could turn on and off with a switch - but I need to understand the hydraulic circuits better first - I like what Charlie did - just not for my purposes - geat for a four in one or a grapple, mini hoe etc - but not to run add'l attachments that need to be "on" or "off"
actually it would be nice to have both Charlies system as well as an additional Aux output (along with the PT setup)
I would also like a built in diverter and reversing switch both on the main PTO as well as an additional Aux PTO
As far as the Aux goes - I use a metal clip that pivots on a pin and holds the switch on - I believe there is a relief that allows flow when you are not actually moving the cylinders on the backhoe - but not sure if this is built into the hoe or - incorporated in the PT steering and lift circuit (aux is tapped off this at the main lever valve i think)
anyway some of my ramblings are speculation
i have the same similar questions as you do - but i do have a few answers - i hope anyone else out there could chime in like Duane
I know that the Aux has a lower GPM output - not sure why - could be the pump - could be hose size since this pump needs to supply to more than just the Aux PTO (ie steering and lift)
the main PTO is 8gpm and the Aux is 3-4 i think - I don't think you need as much GPM for lift (or backhoe) as you do to run attachment motors - (of course at the size we are talking about) - the pressure needs to stay up though
my backhoe has more than enough power with the AUX - the hydraulics are stronger than the weight of the machine - you would not want an 8gpm backhoe on there - as it is it drags the machine around in heavy digging
even if you look at the large skid steer backhoes - the gpm requirements are 6-8 and these are far too big for the 400 series - some weigh over 1750 lbs without a bucket or dirt in the bucket
- so i would imagine that you would use the Aux for any home made unit - unless you use a diverter of some sort for the main PTO to reduce the output -
I wanted to add an additional Aux ouput that you could turn on and off with a switch - but I need to understand the hydraulic circuits better first - I like what Charlie did - just not for my purposes - geat for a four in one or a grapple, mini hoe etc - but not to run add'l attachments that need to be "on" or "off"
actually it would be nice to have both Charlies system as well as an additional Aux output (along with the PT setup)
I would also like a built in diverter and reversing switch both on the main PTO as well as an additional Aux PTO
As far as the Aux goes - I use a metal clip that pivots on a pin and holds the switch on - I believe there is a relief that allows flow when you are not actually moving the cylinders on the backhoe - but not sure if this is built into the hoe or - incorporated in the PT steering and lift circuit (aux is tapped off this at the main lever valve i think)
anyway some of my ramblings are speculation
davesisk
Platinum Member
MR: This is precisely my understanding of how this works too. Mine (being an old model without the aux PTO, only the main PTO) uses the right knee lever to turn on the main PTO (rather than an electrical switch and solenoid). Moving the lever either way always runs the flow forward. I believe this is simply an open center valve, and that fluid is always flowing from the main PTO part of the gear pump through this valve and back into the hydraulic tank. Turning this valve on merely diverts flow to the PTO connections. On mine, if I turn on the main PTO with nothing connected, the engine stumbles, then I believe a relief valve opens somewhere. This all sounds right to me, except that the plumbing is just a little different on my old one.
Dave
Dave