Test Bench Info

[allprohydr]

I am working on a hydraulic test bench project for my shop. It is a slow go with not really knowing which way I want to do some things so I am looking more info. I am doing the work myself as I get time and had rather do some research and ask questions than just go and buy and insatll things and they not be what they should.

Doug, at one time you had mentioned making a edc type controller for the pump with a small cylinder and a control valve. Do you have a suggestion for the size cylinder and type of valve, whether pilot valve etc. How much pressure do you think I would need on the valve?

I have a three different motors I can choose from. A bent axis motor Rexroth A6V, a 24 series Sunstrand, or a 26 series Sunstrand Pump that with help from you I can convert it into a motor. I am using another 26 series pump as the drive pump off an 855 Cummins Engine with about 425 HP. What do you see as advantages and disadvantages and which will work better for using as the drive motor to run the pump being tested? Also What is the advantage of a bent axis other than space compact?

I guess I can use a pilot controlled load valve or flow control valve on the return side of the pump being tested to act as a load for it. And then when I am testing a motor I can switch my fluid to the motor being tested and use my drive hyd. motor as a load. If this is correct then I will need numerous load or flow control valves. It seems I need to have them on both sides of the motors as fluid will travel both ways under pressure depending which way it is turning during the test?

Please share your thoughts and ideas with this, Joey.

[Doug Hanson]

I would use the 26 series drive pump that you have and convert your other 26 series to a motor. That way you have maximum torque available as well as variable motor displacement motor to to run fast than your pump. (check maximum speed on this unit it's big so it's probably not that fast).

The poor mans EDC - a cylinder and control valve is kind of crude, there is no feedback, you would basically hold a button down until the tach read the proper speed and then release the button. A small D03 (NG6) solenoid valve will work for this, you can use oil from the charge pump to run this function. Look around for an old cement truck that has the pump behined the front bumper, chances are it will have this same setup.
As the load on the bench increases, the drive will slow down due to inefficiencies in the drive pump and motor, so if you want keep a steady speed, you will have to keep adjusting it. This isn't really a big deal, if you use High RPM / Low RPM * Low GPM / Hihg GPM * 100 = efficiency, then the speed doesn't really matter.

As far as the load goes, there are a couple of options, you can use a relief valve and a reverse flow check in each line, or you can build a bi-directional relief (hard to get running stable) or you can use a rectifier block to feed oil through one relief valve (this is the best as you can also run the oil through the flow meter after the relief valve).

[allprohydr]

Ok, What are you calling a rectifier block and where or how can I make or purchase one.

What is your idea on converting my 26 pump into a motor. I know we spoke briefly on it one time before and I want to make sure I understand. What would I need to change. Valve plate, Would the angle of swash plate work OK?

On a valve plate for a pump. Looking at the plate and the little cut, if it were to the left of the hole, would it need to turn clockwise? And the ones that have cuts on both ends are they bi-directional?

[Doug Hanson]

This is a rectifier block, you can order direct from Sealum. It's just a bridge formed with 4 check valves, you will find one in that regen test bench schematic that I had posted previously.

Rectifier.pdf

(51.56 KiB) Downloaded 1203 times

There are a couple of things that are needed for motor conversion, to do it properly, you need one new ccontrol piston with stroke limiter, one valve plate, a different controller, a different end cap, a transmission block (hot oil shuttle).

However you could get away with using the existing valve plate (you should change it if you can). On a motor valve plate, the lead ins to the kidney ports are bi-directional, as for the pump valve plates,if you think of the notches as arrows, the rotation goes in the opposite direction that the 'arrows' point in"

-Build a stopper to sit in one of the control piston cans that will keep the swashplate from going to neutral. Try and keep the swash plate from tilting to less than 5 - 10 degrees, you can adjust this by threading the pistons can in or out.
-Remove the charge pump and build a cover plate.
-Build linkage to operate the controller and to prevent it going in reverse.
-Plumb a 1/4" line from the service port on your pump to the service port on your motor to provide pilot oil for the controller
-Use an external Hot Oil Shuttle valve
- Port the return oil from the hot oil shuttle valve, into the lower case drain port in the motor, from the top case drain port of the motor, run a hose to the lower case drain line of the pump, then from the upper case drain port in the pump, run a hose back to tank (through a cooler and filter if you wish).

[Chris 21]

Hey Doug,

I am new to this game and looking at building my own regen test bench, i have searched the previous post but i am unable to find the schematic that you had posted previously, is there any chance that you could please post this again,As it would be realy helpfull, also any advice that you can give on building a cheep test bench for pumps and motors,

Regards
Chris

[Doug Hanson]

It's posted in this thread: viewtopic.php?f=3&t=41&start=10

Cheap test bench is an oxymoron. Even going cheap your looking at a large investment. A regen bench can save you money with respect to the size of prime mover required, however it has the added cost of an extra pump, motor and rectifier block.

[Chris 21]

Hello Doug,
Thanks for the info, by cheep i mean cost effective, a regen bench will work well for me as i have limited power avalibility , a regen bench will give me the most efficient use of the power that i have.

Regards,
Chris

[Doug Hanson]

What have you got for a prime mover?
What torque capacity and drive speed do you want on your bench. The best thing to do is work backwards from your drive motor as a starting point. So you want to know max drive torque, max drive speed at max torque, and use 5000 psi as a max drive loop pressure. That will determine the size of drive motor to use. The rule of thumb seems to be that if you size everything up right, you can achieve a simulated load of 3 times what your prime mover is. If you had 50HP you can run a load of 150HP.