Building a Dyno

[drivetrainUW-Platt]

Hello,
I was doing some research on building an Inertia dyno from scratch and found that it is a relativly simple task. One example is found here: http://www1.cedar-rapids.net/tdkmotor/ Basically there is a large diameter steel disk with speed sensors mounted to it. The program that I saw used was called DataMite. I know the difference between being able to use an "engine" dyno and a "chassie" dyno can mean a few months, since the car must have a frame, completed drivetrain, and at the least a rear suspension and uprights. The questions I have are:

Is an inertia dyno the easiest to construct, or would something using an alternator/generator or a water pump, or some sort of braking disk work out better?

What have other teams done in the past for in house dynos?

What computer program was used?

What range of horsepower could these dynos accuratly measure? (I would be interested in anything from 15 to 100 hp)

any ideas or pictures would be of help
thanks,

[drivetrainUW-Platt]

Hello,
I was doing some research on building an Inertia dyno from scratch and found that it is a relativly simple task. One example is found here: http://www1.cedar-rapids.net/tdkmotor/ Basically there is a large diameter steel disk with speed sensors mounted to it. The program that I saw used was called DataMite. I know the difference between being able to use an "engine" dyno and a "chassie" dyno can mean a few months, since the car must have a frame, completed drivetrain, and at the least a rear suspension and uprights. The questions I have are:

Is an inertia dyno the easiest to construct, or would something using an alternator/generator or a water pump, or some sort of braking disk work out better?

What have other teams done in the past for in house dynos?

What computer program was used?

What range of horsepower could these dynos accuratly measure? (I would be interested in anything from 15 to 100 hp)

any ideas or pictures would be of help
thanks,

[Garlic]

Inertia dynos are not what you want for engine mapping. They are good for checking power but for mapping if you can't hold the engine steady state, you'll always be chasing your tail.

If you are going to the trouble to build a dyno don't go with inertia.

[ReadySetGo]

We have a waterbrake dyno and it works pretty good. It is great for all load conditions, part throttle to full throttle. Fairly cheap and easy to make if you want to make it yourself. Teamed up with EGT gauges and a lamda sensor you should be able to test very accurately.

We are using a Depac system for the electronics part. Not really the most high tech but definetely does the job.

The actual horsepower, or torque really isn't what you should be after. The repeatability and the ability to see what changes to the engine do to the torque curve are more important. All dyno's differ so peak hp and tq are relative to each dyno.

Also check out the dyno company that was at the 2004 comp. I totally forgot the name of them but I'm sure someone will chime in. Dynomite?

[Tony K]

We use a 175hp eddy-current dyno that was donated to us last year. The initial setup and custom tailoring was a bit much, but now that it's done, it sure is nice to have. All of the controls are run through LabVIEW, so it's pretty versitile. We also recently picked up some Horiba emissions analyzer racks, so once we get those hooked up we should be in great shape as far as engine tuning is concerned.

[John Bucknell]

One of the bazillion side projects I work on Hardman Racing (http://www.hardmanracing.com) has an engine that is so integrated into the car that we needed to construct a chassis dyno that bolts into where the rear axle is (chain drive) to calibrate it in our garage.

We acquired a used 500hp water brake (Go Power, I think), built the adapter, and used an AC pressure sensor off a PT Cruiser (0-500 psi for $10) for the load cell. Calibrated the sensor with a lever arm and known hunks of lead, and ran the whole thing with a servo valve controlling the water flow rate. Best of all, our data acquisition was just our Motec, running the pressure transducer into one of our sensor channels and doing a math function on it. Got decent data too - around 250 bhp with a turbocharged FZR750 motor, but wouldn't hold the FZR1000 motor because the pump from the well couldn't supply enough water http://fsae.com/groupee_common/emoticons/icon_smile.gif...

[drivetrainUW-Platt]

from what I have read the inertia dyno needs a huge disk, the more hp the heavier the disk. what do you use for the water break, like a water pump or something custom, would appreciate some pictures or building processes
thanks,

[John Bucknell]

Inertia dynos just need to have sufficient mass that the dyno accelerates slow enough to get data. So yes, usually they are huge.

Water brakes can be water pumps where you throttle the outlet to vary the load. However, a straight impeller pump wouldn't make the best brake (not that you necessarily need the best) - which is why most water brakes look more like a torque converter with the casing being the reaction member and load is controlled via raising and lowering the water level inside the casing (inlet throttle). I don't have any pics of ours, but this sight is pretty comprehensive: How Dynos Work (http://www.land-and-sea.com/dyno-dynamometer-article.htm). Search a little more on water brake absorber and you should be able to find what you need.

[Z]

Back in the early 1940's (WWII) Ford were making more than 100 Pratt & Whitney 18 cylinder radial aero engines (about 46 litres each) PER DAY! For reliability reasons they had to dyno-test/run-in each engine for 5 hours. If they used water brake dynos that would have been a lot of hot water. Instead they lined up 28 x 1250KW electrical generators, drove each one with an aero engine, and thus provided power to the plant that was building the engines.

An FSAE team could do a similar thing. Find a suitable generator, hook it up to the mains electricity supply, and use it to get your electrical meters spinning backwards! This would require the cooperation of the local electricity authority, and at present cents/KW.hr you might just earn enough to pay for your fuel. A good project for the Elect. Power Engineers.

Z

[Igor]

Although this sounds like a nice theoretical idea, the cost of the equipment necessary to deliver power to the grid is prohibitive for FSAE style budgets.

Igor

[Z]

Igor,

I think (but not sure) that there is already a commercial system that works this way. It uses one generator per wheel, each generator sitting on a small stand and bolting direct to the wheel flange. Thus 2WD of 4WD can be dyno'ed with 2 or 4 of the same units.

Where I live there are a lot of domestic solar power systems. Some of these are connected so that they can feed excess power to the grid. This grid-hook-up is relatively inexpensive. You just have to push the electricity harder into the grid than it is trying to push it out (240/415V here).

Z

PS. Any cost can be amortized over 5-10? years, since it is University "plant".

[Igor]

Don't let the fact that FSAE cars are full of carbon and CNC'd parts fool you that they have money to spend. When most teams struggle to buy dampers, nobody is going to spend money to feed power to the grid with expensive electronic dyno's when they have free university water.
And amortising expenditures in FSAE? In what universe?

Igor

[GTmule]

Also, 100 Hp, for 100 secs is about 2.2 kW-H,how much is electricity? On the order of pennies per kW-H, anyway, right? I wish we had time to use our (theoretical) dyno enough for that make sense.

It's still a nifty idea, especially in the exmple where Frod did it.

As a side note, our department's got an OLD see-through internal combustion engine that gets its load from a motor/generator, it's cool as hell to see it run. Ya gotta get it spun up a bit to get the (rubber) rings to seal, though http://fsae.com/groupee_common/emoticons/icon_smile.gif Runs on methanol, gas, propane, whatever. We considered adding boost with the exhaust from the shop vac, but thought better of it http://fsae.com/groupee_common/emoticons/icon_smile.gif