Here's what I have used for similar projects:  http://labjack.com/  .  The data goes to a text file that you can put into Excel to fiddle with and plot.  Get the HV model.  The voltage input range on the plain one is a little unhandy.  You can calculate power on either side of the motor controller and motor input power from voltage and current.  You can calculate motor output power from RPM and reaction torque.  Anybody have a good transducer for measuring motor reaction torque?

Testing props on a static bench is pointless.  Stunt planes fly at legal highway speeds, though, so you can mount the motor on a stick attached to a car.  This sort of behavior actually attracts chicks, as Chris Cox can verify from our anemometer calibration run in a Miata.

We can get 3600 here.

For what it is worth, I had a thread on thrust static measurement here that was lost in the crash of the web site some years ago.

I use a digital scale and a lever setup the has equal arms and which I attach to the tail skid of my electric Ringmasters. The photos below show the actual setup in operation.

John

Guys,
Interesting ideas, the one thing I like about the Watt meter is that you can see the output as the test is underway. I want to test for amp load and adjusting various setting to the ESC. Up till now I did these with the ship on the living room floor but its a pain (no, really a pain) to keep bending down to mess with this. With the test stand I can mount it in a Black & Decker Workmat and stand up, no mess and much easier on the back. For the rpm what I have done in the house is position a flash light to give the steady light and use the tac pointing toward it to get a good reading.

I might try and work on some type of trust measurement base on something like John's approach only it will be the test stand in some sort of track. I like to know static thrust since I like to reshape props and this is what gets you out of the corners and over the top.

Best,       DennisT

You can't always get what you want.

Good one Howard! 

Your right, I should not have left the word "everything" all alone. It could be easily misunderstood? .....  I edited my post as follows:

        "It gives you ALMOST everything you need (it does not give you a night with a 21 year old movie star, or your own Lear Jet, or World Peace, etc. .... but it does give you some valuable E-Information).   

Thanks Howard for reminding me of the 60Hz in the USA that gives 3600 rpm. I also agree with Rudy that the Eagle Tree recorders are great. I just find that add-on for rpm that uses the motor wires is a bit jumpy. I'm going to make my own interface that use a hall-effect sensor. I did try the Eagle Tree optical sensor, but I just don't get a good reading all the time.

I've done loads of bench testing, and I usually end up with a DC light source like a flashlight etc. pointing through the prop. The hall-effect sensor will suit me better though when I'm playing with the governor software.

Keith R

Will you also use the Hall-effect sensor to measure current? 

Interestingly, the Eagle Tree people live about half a km from me.  I have had a little correspondence with them, but I haven't met them.

The Eagle Tree people are the best.

Guys,
I hope to post some pictures of the stand soon, I am looking into using draw slide rails to allow the stand to be hooked to a scale and give a relative static thrust reading. This would allow some ground testing of different props. I know that the proof is in the flying and I agree. The ground test would give a rough idea of the amp load and the thrust available for acceleration for one prop verse the other.

Best,         DennisT

Dennis, This is exactly what I use my static thrust rig for. I test various props at various RPM. I use my AstroFlight Whattmeter to keep track of the AMPs being pulled. These data are not directly translatable to flight figures but they do give a good starting point.

John

I've been wondering how to do that, too.  You could spin an aluminum disk and put a magnetic field across it, but the disk might get too hot.  If you use a generator, you could drive a resistor in a bucket of water and get rid of the energy that way.  What would be a good thing to use for a generator?  How would you couple it to the drive motor?  Do the RC guys have U joints that would work?  I would think you'd still measure motor output power from RPM and reaction torque, but maybe when you got the generator system calibrated you could use the generator output directly. 

How does it fly?

Bob,

I'm sure that Dennis will reply, but from what I can see there is a large hole in the center of the mounting plate (board) which will allow air to move through to the motor.

I would agree that a few additional openings would help to insure cooling.

John

For what it's worth, here is a pic of my test stand.  I use an electronics lab power supply.  I can set any battery voltage and read amps. 

An non-contact infrared temperature sensor is usefull on the test stand as well as at the flying circle.

Paul

Nice piece of work!

According to the generic Fan Laws power required goes up as the 5th power of diameter however, you are mixing diameters, pitch and RPM to generate a given thrust.  If you wanted you could generate the same thrust and lap time using a 6x10" prop - but you might not like what happens after you do a square corner!

Larger diameter (21% more disc area) will draw a lot more static.  I think you need some flight data to see what is really happening.  Between the props you show, I think the higher RPM will still proably result in higher current draw but nothing like the increment you are seeing on the bench.