The heart of the Dyno is the Pump. There are two ways to measure motor output, with load (pump or drag break) or electricity. Probably the easiest way would be to measure the wattage output and this would be done with Eddy Current brake (Telma retarder). Not being able to find one of those, I opted for the water break and load cell. If you want to know more urge you to read up at YourDyno https://yourdyno.com/brakeabsorber-dynos/
The principle is simple. Create load, measure force from load with the load cell, calculate the end result. Is it 100%? No, but really you don’t need it to be. It is a loss loss system anyway. What you need is to measure change in load over the arc of the RPM of the motor. If you want to know if your carburetor changes helped, then the measured curve of this run vs the curve of the last run is what you need to know. Did our tuning make the motor stronger or weaker? Knowing if it generated 110hp or 111hp doesn’t really help, it just a number.
Where did I get my pump? I have no idea. It was salvage someone else was getting rid of because it was all locked up. I.E Free! When I took it apart, it turned out to just be full of mud. I think it’s an old farm pump for pumping out pond or lakes. For our purposes I have mounted it on bearings. One front and one rear. This mean the pump is free to swing or pivot. We hold it in place with the load cell. That then measures the drag applied when we close down the valve on the output shaft. A 55-gallon drum provides the water, which just circulates in and out. Simple, right?
Not so much. Not know who made the pump or where it came from means no parts and you get to make your own replacement gaskets. In fact I have had work out all the details. If there is any part of this I’m not sure about, it’s the pump. If I can’t make it work I’ll have to find a truck scrap yard and a Telma retarder. But since the frame design is modular, I can just swap these parts and the rest stays the same.
I was supper thrilled when we were able to pump water. It means that the pump is good and likely to do the job we need. Happy workshoping.
Look for the other articles in the series DIY Dyno Frame and Dyno Load Cell.