# Hydraulic load cell motor testing



## Archer321 (Jul 28, 2016)

So I built a hydraulic load cell so I can test the efficiency effects of things like gear ratios, controller settings, operating voltage, etc on my Electrathon car.

I used a jackshaft so I could run the same sprockets on the test rig as on my car while keeping the hydraulic pump speed within its normal operating range. The pump outputs to a hose with a ball valve and a pressure gauge. The jackshaft has a speedometer calibrated to the size of the drive wheel of my car. The motor is run at a speed that gives the desired wheel speed and then the ball valve is closed to the point that the amperage draw reproduces the same load that I have seen in race conditions. The pressure, speed, voltage, and amperage draw are noted and then become the baseline for comparison of any subsequent changes. If I can find a change that allows for the same speed and pressure to be achieved at a lesser wattage then I have improved my efficiency.

Should make for some fun testing.


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## Archer321 (Jul 28, 2016)

Another view


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## kennybobby (Aug 10, 2012)

Very clever innovation--what range of pressure can the pump generate, and does the ball valve restrict the output of the pump? Can the pump stall the motor completely if the valve dead-heads the pump?


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## Archer321 (Jul 28, 2016)

I'm not sure how much pressure the pump will make. It's just an old one I had laying around. I don't know much about it. The ball valve is used to restrict the output flow and load the motor down in the process. So far I have seen pressures up to 600 psi. I'm not sure what would happen if I closed the valve completely. I would like to think it would blow the main fuse before it popped the hydraulics or stalled the motor.


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## Duncan (Dec 8, 2008)

Hi Archer

You need one tiny change and you will have created a nice dynamometer for yourself

You need to measure torque

That is not that difficult - you can use one of those "wavy wand" torque wrenches

You need to bolt your pump to a separate plate with a pivot point and a limit stop

Simply operate as you are planning and then use the torque wrench to move the plate with the pump on it off its limit stop and you will have the torque that you are absorbing


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## dcb (Dec 5, 2009)

Oh, dynamo-meter assumed with the laptop right there. I imagine torque is essentially a function of pressure too, and rpm signal, nice rig there! Hope to see it in action.


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## Archer321 (Jul 28, 2016)

Yeah, it's almost a dyno but not quite.
I thought about measuring torque but decided I didn't really care at this point.
Since all I am doing is tuning for efficiency and I already have a stock baseline then the specific torque figure seems kinda moot.
At least for now.
Perhaps I'll rework it in the future.


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