Backhoe Design Ideas

[Iplayfarmer]

You could put some short hoses on the pump, prime it, and turn it by hand say 10 revolutions to measure the output in a graduated bucket or big measuring cup. 1 cup = 14.44 cu in.

I took your suggestion.

I turned it 50 revolutions and filled a 8" diameter bucket with 4 3/16" of fluid (I used heating fuel). I figure that's about 210 cubic inches or 0.91 gallons. That would make this a 4.2 cubic inch pump and the output at 540 rpm is going to be 9.8 GPM.

That sounds about right. At 2000 PSI that comes out to 11.5 Hp based on the formula on Wikipedia... Hp = GPM X PSI X 7/12,000. Even considering a large margin of error with my crude measuring, I should have no problem running the pump. I think I'll have room to throttle down if needed to slow things down a bit. I'll probably pass on the flow divider for now.

 

[Brad_Blazer]

Good to go! (and your pump is nice and clean )
2000psi should be enough that you don't need oversized cylinders.

 

[Iplayfarmer]

Good to go! (and your pump is nice and clean )
2000psi should be enough that you don't need oversized cylinders.

Cleaning the pump was another motivation for the exercise.

I agree that I don't need oversized cylinders. I have a couple of larger spare cyinders around though, and now that I have the flow I may use them vs. buying a smaller cylinder.

I'm fighting the temptation to hook up this pump temporarily to my loader. I'm currently running on about 2.5 GPM. 9.8 GPM may just be enough to actually launch something out of the bucket.

 

[J_J]

Where did the 2000 psi come from? I only stated that the Prince PTO pumps were 2000 psi. You will have to put a pressure gage on this pump to see the max pressure, but anyway, put an adjustable relief valve across the input and output, setting it at around 1500 to start with.

Do you know if this pump is designed to run at 540? Are there any numbers or letters on the pump.

 

[Iplayfarmer]

Where did the 2000 psi come from? I only stated that the Prince PTO pumps were 2000 psi. You will have to put a pressure gage on this pump to see the max pressure, but anyway, put an adjustable relief valve across the input and output, setting it at around 1500 to start with.

Do you know if this pump is designed to run at 540? Are there any numbers or letters on the pump.

Last I heard, 2000 PSI was the standard average that this size system uses. I'll have to steal my gauge back from my MIG gas bottle to test the actual pressure of the system.

There's nothing on the pump. I'm going with the fact that it came with a coupler that fits a standard 1 3/8" 6 spline 540 PTO shaft. I'm also taking the seller's word for it that it was the pto pump on the backhoe that I saw in his yard when I pulled up. I don't recall the make of the backhoe, but I do recall that it was a factory unit, not homemade.

 

[Iplayfarmer]

If I'm going to have a PTO pump, I'm going to need some way of defeating the safety switch so that the tractor will stay running with the PTO engaged but no operator in the seat.

How do most backhoe attachments accomplish this? My simple mind says to put a switch somewhere to override either the seat safety or the PTO safety. Is that the best way.

 

[Iplayfarmer]

If I'm going to have a PTO pump, I'm going to need some way of defeating the safety switch so that the tractor will stay running with the PTO engaged but no operator in the seat.

How do most backhoe attachments accomplish this? My simple mind says to put a switch somewhere to override either the seat safety or the PTO safety. Is that the best way.

Anybody?

How do backhoe attachments with PTO pumps work around the safety switches without an operator in the tractor seat and the PTO on?

 

[J_J]

Install a SPST switch across the seat switch. Off position, the switch is open to let the seat switch work as it should. Flip the switch on, and the switch is used to jumper across the seat switch.

 

[dfkrug]

How do backhoe attachments with PTO pumps work around the safety switches without an operator in the tractor seat and the PTO on?

First, the newest tractors seem to provide several interlocks that allow
some off-the-tractor PTO use. My latest will allow the engine to stay
running when you get off the seat if the parking brake is set. Starting
the tractor off the seat with the brake set simply requires you to push
with your finger on the middle of the seat while turning the starter switch.

Other tractors do it differently.

You can simply jumper the seat switch to disable that interlock. That move
is not really unsafe unless yours is a gear tractor. A HST tractor will not
run away when started off the seat.