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Hello,

I am looking into building an engine dynamometer for racing go-kart engines. I am planning on using a Micrologix 1500 and RSView.
I am not sure how I am going to do the brake. (water brake, hyd. brake or use a motor to load the engine) Any feedback/ideas are welcome.

Thanks,
Bob

My first reaction for a brake would be electric. However, I don't know what kind of horsepower you are dealing with here so this might not be a real cost-effective solution.
A regenerative DC drive/motor combination would give you an easily adjustable torque setting. It also simplifies getting rid of the energy. Any brake you use will need to be sized so it stays cool. Look at these guys for low-cost DC drives:
KB Electronics
I don't have any experience with water or hydraulic brakes. Those may be the way to go as I would suspect they will be pretty robust. I don't think a friction brake will work for you since it might be kind of tough to get the torque low enough to be usefull for the horsepower dissipation you will need.

Keith

Maybe you should explain what the dynamometer is and..

How it works.

Are you going to build a platform that the go kart can be driven (or pushed) onto then the ....rollers or absorbers are to be used to provide "resistance" or "braking"?

The idea is to apply fatiguing loads to the engine/chassis and verify indications...a form of calibration. Is this correct.

Water and flow control is the common "braking" or "loading" application isnt it? Wouldnt it be prudent to study those systems that already exist?

I can understand wanting to build your own, those things get expensive. I started life as a mechanic and dealt with them some in the racing days but not now.

Kamenges was on the right track I believe, the braking or loading has to be applied in a way that can be measured and monitored.

dynamometer

I developed a dynamometer application that is used for racing car engines. We tried different braking systems and finally settled on using the water brake. Ours measures 10 different readings coming from the engine including rpm, pressures, air and gas flow, temperatures and torque. It is currently controlled by a SLC 503 and interfaced to a computer to display and save the results. That gives them the ability to display and compare the pull results from different types of tests.
One thing to consider is your processor scan times when designing this type of system. Things happen very fast during our tests and your processor must not miss any. They also happen very loud when dealing with a 1500 HP engine. Another thing is the costs, all these analog and digital controls can become quite expensive.

Good Luck and Happy Capturing

This site has a pretty good explanation of the Water Brake
Very Interesting to read that HP & Torque match at 5252 RPM.

Thanks for the feedback and the links.

Bob

Check this link out.

http://www.dynesystems.com/What_is_a_Dynamometer.htm

It gives a good comparison of all the different technologies. I would definetly go for the water brake if this is just for fun. The eddy current is OK also, if you need more accuracy and have the money. The electric option (DC or AC) is most likely out of the question unless you are developing this for a commercial application & even then I don't picture the go-kart market going for that expense.

Our first generation dyno used a hydraulic motor & flow controls. The second was eddy current and the current generation uses AC regenerative drives (VERY expensive option, but very good).

Just don't forget that you need a way to dump all the heat if you use a closed loop water system!

Darren