Diy Engine Dyno

[Jason]

So atm I'm planning on making a engine dryno/test bed. So I though i would share my ideas and hopefully get some input on my design.

 

My current plan.

 

[Motor] > [Torque converter] > [Disk break]

 

Torque converters don't load linearly. Therefor conversion dyno maths would be hard to match it.

 

But why bother putting it into kw or n.m?

 

So my thoughts would be to set up an 'performance bench mark' setup of the brake. Which would measure acceleration of the motor over a set period of time or time from idle to redline. To take into account brake pad ware. Have a predetermined torque that the brakes apply to the converter. Eg 100Nm is required to turn the converter. That after every run would be reset and checked.

 

 

thoughts?

 

j.

 

ps If you want to help :D

Edited July 7, 2008 by Jason

[camerondownunder88]

Mate of mine built his own engine dyno to test his jet engine using the brake method. Worked well adn readins were spot on after the maths can be done is accurate. Mate did use a drum brake but he said calculations were easier. But I am sure for you disc or drum you could cope with the maths.

 

Or what about a air dyno or an electric generator and load it up? Just ideas.

 

 

Cameron

[Jason]

I though about an electric generator, but then when you think about how much power your trying to get rid of (300kw + for next motor )it starts to look a little scary :D

 

How long could he run the brake setup. The reason I'm thinking about the torque coveter is to be able to manage extended runs. I havnt seen any working diagram of an air dyno, hmmm ill look for some. But I'm trying to keep it as gehto as possible :yes:

Edited July 7, 2008 by Jason

[irokin]

Why don't you use an eddy brake like real dynos?

[Jason]

O ive been looking at how to get a DIY one :D

[irokin]

The other brake commercial engine dynos use is a water brake. Not exactly sure how they manage to measure HP output however...

[camerondownunder88]

Ok air dyno output haft BIG ASS FAN turn fast. But If I can ill get pictures of the air dyno at my work handles 2000+HP all day and it is just a BIG BIG fan well more like a paddle steamer boat the fan dlades are FLAT..LOL So ill see what I can do there for you.

 

Now maths for moving air is pretty easy fan dyno could be an idea and could be done ghetto.

 

Another idea is drive a compressor. Now after some maths you can calculate the shaft HP used to drive a centrifugal compressor. Not build a gear box say 1:15 so you step up say 6000RPM motor to 90,000RPM and drive a compressor that has to push air through an orriface so it makes pressure then it is piss easy to find horse power the compressor is using etc. Now for an idea from memory to spin my compressor in my engine it is 217HP at 80,000RPM making 35 PSI proba bit of an advanced way of doing it but could be ghetto built eg balance rotor and shaft on glass etc can be done. As I said weird idea but would work just depends on the amount of moeny effort etc going into this.

 

Will dyno be used more than once could be cheaper to pay some one?

 

 

Cameron

[Jason]

Definitely going to be used more than once :D

[philbey]

At uni we had a water brake dyno, but I never really had the chance to look properly at the workings of it. That was a good little test bed, i'd love to take a squiz at it again some day.

 

Used it to do efficiency practicals, good times...

[irokin]

I've just learned that Scania road trucks have 24v eddy brake retarders. Then thinking of retarders I looked up the capacity of the hydraulic retarders of our dump trucks at work. 662kW CONTINUOUS load. The only thing that might screw you with using one of those is a) RPM (gear it down) and b) price. I'll ask works mechanic when I see him next if its possible to get the retarder unit separate from the gearbox. I'm sure there is a dumpy that comes with a separate hydraulic retarder unit. These also have easily varied load (pull a lever or push a peddle).

[Jason]

Just playing around with an old hdd. The eddy current breaking is quite significant. Using the magnets (i think there Neodymium by how strong there are?) can really slow down how fast the disk spins.

 

Now to step it up...

 

Order some FREE ENEREGY magnets. And some how find a large copper / aluminum disk.

 

 

Any body got an old dingy and a home blast furnace?

Edited July 7, 2008 by Jason

[Jason]

Things around the home : Lawn mower flywheel - nice chunky piece of aluminum, has cooling fins. Also the armature of a alternator, peice wire copper, just need to short the windings. Might burn out?

[Jason]

BRAIN EXPLOSION!

 

After a little more thinking i may have just come up with a simple way to get torque directly out. Almost no calculations.

 

Going on the idea of a water based load cell. Once water is introduced into the turbine cavity it will create restriction and so forth, ok nothing i didn't already know. But if the water pump house is floating, ie on a bearing. I simple force gauge can be mounted on the casing of the pump 'holding' it in place. The force as the pump torques up it trys to turn, Putting force on the force gauge. Simple Force X Length = Torque!

 

It wont give an accurate reading but it will give a comparable reading.

 

This could work for a torque converter no?

 

 

This is soooo doable. I could even get a data logger and plot the toruqe vs rpm on a screen.

 

Now that i think about it, any load cell will work with this setup.

 

Hmm i quick wiki search shows that this is the normal way of measuring torque. zzz

Edited July 8, 2008 by Jason

[camerondownunder88]

^^ Data logger hey...

 

Can you share info brand inputs analogue or digital etc? I am in the market for one need about 6 analouge inputs etc.

 

But mate who made a dyno made a Prony Brake style dynamometer. He made a steel drum attached to the output shaft of his engine.

 

He cut up old brake linings and made a custom brake pad for it. On the top he used a pneumatic cylinder that he can vary with air pressure remotely.

 

To the sides of the custom brake pads he made he attached steel rods that go down to a set of fish scales. These give him accuracy to 5% and he added water mist spray to the drum hub to help with cooling etc. He has input up to 14,000RPM into this setup of his and never failed or anything so good system.

 

Pic below:

 

And what he does is ballances the drag of the brake with RPM or power turbine and gets his torque reading off the spring scale. Then just sub that into a basic horsepower calculation:

 

Horsepower = Torque (in lb-ft) x RPM / 5,252

 

He got an accurate reading.

 

Also the rods off the side of it are 12 inches long to make calculations easier.

 

Cameron

[Jason]

Nice :D

 

what kind of power was it seeing?