I built one for garden tractor engines as I was pulling them and needed off track tuning..Used a big industrial hydraulic system oil pump [free]..No hp readings per say but great for referance, max pressure made meant most power..I had to learn to let the oil get to 100° at light load and then limit power runs to max oil temp 240°..Could have made water to circulate coil-wise through oil but didn't want to get too trick for a $.79 ribbon..And it gave me enough of an edge to get accused of cheating...
I know these pictures are the worst, but it was the early 70's when we had this thing in operation. There are 4 photos and hopefully it can clarify what I was trying to describe above. All 3 pieces to this where on casters so it could be moved in and out of the shop. Ideally, torque should be read when the load is just high enough there is no RPM rise @WOT, whatever RPM you were at. Unlike computerized equipment of the present, we had to do many pulls to try to obtain any semblance of a curve. Could really make some racket with the throttle wide open and standing on the brake, but the motor and the brake would be worn out before you could use them again. Someone let me know if the file can not be seen and I'll try another method. Tom S. in Tn.
A local speed shop partial to hemis had a dyno and the water heat sink was a 55 gallon drum. The boss/owner told a story about his star ***istant being able to judge the "quality" of the engine build and combination by laying his hand on the 55 gallon drum after a hard pull. "That's a good one."
"in some way the throttle has to operate in relationship to the torque reading device, hmmmm" What...?? <!-- / message -->
It is possible to build a home made engine dyno. The tricky part is the calibration. You have to have the essentials such as an engine cart, and all the basics to actually "run" the engine. The calibration issue can be solved by using a "Load cell". A rotary load cell that produces a torque reading can be used with a digital read out to display the actual engine torque. All you need for the RPM part of the equation, is a good accurate Tachometer. Then you can take RPM and torque readings for determining your horsepower. Horsepower can be accuretly determined by multiplying the RPM by the torque and then dividing by 5252. THat is the basic formula. Horsepower = Torque X RPM / 5252. To save the expense of a costly dyno software package, you can use an excel spreadsheet with the RPM levels listed in increments and type in the corresponding torque readings as you read them from the readout. An automatic formula can be inserted into your spreadsheet to do the calculations for you at each RPM reading. The real problem for me in designing my own home built dyno was how to place the engine under a load. An engine that is bolted to a test stand will run free and easy with no load on it. I was able to design a home made water brake system using a PTO water pump for a farm tractor and coupling it to the flywheel. This also takes some machine work and custom made coupling devices for doing so. I might also add that it took me several years and three tries to get what I wanted. I am still making improvements to my design even today, many years later. THere are many different types of engine dynos. Water brake, eddy current, and even one that uses weights to determine torque just to name a few. This mechanical version was the simplest for me to build and also the most cost effective.
hi everyone, i am a new member..nicetomeet u all i want to design a water brake with stator and rotor but i dont know how to begin designing, can anyone here help me out to design this water brake dyno? i want to use it for motorcycle with max power 23,5 kW / 11000 rpm and max torque 21 Nm / 10000 rpm here is my email: farrell.dvn@gmail.com thank u very much!
Where I work, we cut and grind flywheels for these guys' small engine dynos. http://hewittsinertiadynos.wordpress.com/ Blue
I started making one once using a disc brake and a 1 foot arm. Then I realized I didn't need one. I was only doing it to prove appoint to someone who wouldn't get it anyway. The partially finished dyno was sold with my shop machine shop equipment and far as I know was never finished but doubled as a run in stand. I have since thought a big truck diff with brakes would do the job if pivoted on centre and a torque measured at the pressure point between the frame and the diff housing. As to calibration that requires an accurate scale, an accurate torque arm distance and an accurate tach. The rest is just math. 5252 thing and all. I prefer to judge HP from car weight and MPH. Got so used to using that method it is almost second nature now. Don
Many moons ago I built a small dyno for testing motorcycle engines. It used an Allison coolant pump for the brake. It would handle up to about 60 hp. It was a 2 man operation to get the data on paper. One guy ran the throttle and brake valve and watched the tach for increments. The other took the readings. Even so, we were both VERY busy. The noise drove the neighbors crazy because some of our pulls lasted 30 seconds or so.
It seems like with a load cell, an rpm signal, a computer with data acuisition software, and a big *** water pump you could build one fairly easily. Just build it near a lake and **** the water from the lake!
i want to design a water brake dynousing a water pump as the absorber...i dont know what the calculation or equation for the water brake dyno which has tator and rotor..so i will use water pump then...
Why not use a driveline brake off big trucks ? they are an electro-magnet, they use them alot in off-road trucks in Canada, would be very simple to build a Dyno from one and there should be lots of them in truck boneyards. Chris
I was also thinking of cannabalized off highway logging trucks while reading this thread. Perhaps an Allison transmission retarder with the oil run through a heat exchanger with a fan on it. You may be able to correlate the hydraulic pressure against the rotor vanes into torque. You would also need a driveline brake to bring the whole thing to a stop.
Charlie Broomfield from the "Practical Performance Car" magazine in the uk has built an engine dyno, using "Telma" electronic retarders from a couple of old coaches, by measuring the electricity produced he can calculate the horsepower made by the engine, which i a 27 litre Rolls Royce tank engine fitted into a Rover SD1 Shell, He is experimenting with Turbos and Superchargers I ***ume to attempt an UK land speed record. http://www.ppcmag.co.uk/index.php Perhaps contacting him via the magazine would get you some useful information.
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