Gas engine test bench

[Kiwi]

OK all you petrol heads. Help me out here.

I have the basic idea of an engine test bench capable of 50cc to say 350cc gas aero engines. My big test bench does up to 2000 hp but it is not much use for my DA50.

Why do I want to build one of these. Simple, I am sick to death of the estimated Hp etc using thrust calcs version 1.03 etc etc etc.

Just for the hell of it I want to build system that will tell us exactly what the little pony produces. What it does with what prop is another story but raw horsepower and torque mean everything.

So my basic idea is an engine stand that is variable in height and width to accomodate any engine, no matter who's.
Where the prop bolts on I can build adaptors for any make or model that will connect to a horizontal shaft mounted on bearing blocks at both ends. That way there is no side loading the crankshaft bearings which they were not designed for anyway.

Using a low friction belt much like a modern alternator belt driving an electric generator. The belt is normally slack and gets pulled up tight by a jockey pulley on an over center crank. That lets me start and warm up the engine without any load on it. The generator or alternator then has a variable load applied with the appropriate volt and amp meters, from which I can deduce the power of the engine from.

Cooling the engine with a seperate blower system ducted over the engine as suited.

Parameters to be measured for example.

1. Peak Hp @ x rpm
2. Peak torque @ x rpm
3. Cylinder head temp, forward and rear.
4. Exhaust temp. (ideal to get the mixture absolutely smack on)

Does anyone have anything already so I dont need to re invent the wheel, or more so any ideas on doing this. This is not for money, just curiosity and fun. Plus real information as well. Less BS.

Imagine being able to really see where the pipes cut in on your DA150 as opposed to farting around with 500 bucks worth of props until you get the engine in the G spot.

Guys there must be dozens of you out there who can give me some cues on the ducks nuts of doing this. Plus every iota of info etc will be shared on here.

Waiting to hear from you all.

Kiwi

[mfuess]

You will probably have to fend for yourself on a "true Dyno" thats small enough to do what you are looking to do.

[adrian]

i understand the dynamics of rolling road and engine dyno's but to get it small enough is a good challenge - as you mention the side bearing pressure from belts and when the engine is a full tilt how to imply the electric brake without to much friction and other losses - marvelous challenge and I will certainly hang over your shoulder often.

[mfuess]

A dyno brake will be the least of your problems... as brakes are available in small sizes. The remainder of the components will be difficult. Forget belts. The engine will have to be direct coupled using a flex-coupler. The stand must be able to rotate (axially) slightly and it must connected to a high-quality strain gauge. All the controls will require I/O ports connected to a fairly fast computer with lots of storage capacity (depending on the sample rate you select). Then when all of that is accompolished, you will need software to manage the I/O controls as well as analyze and calculate the massive flow of data. It may or may not require AD converters depending on the equipment you find.

I've built 2 dynos over the last 20 years... and you can spend a lot of money on them.

I believe you would do much better with an in-flight data recorder and sample "real-world" data.

[adrian]

senor Kiwi - news??