it is written on avinoic motor manual
that  1780 kv gives 650 grm thrust with 8.38 sf propeller

what is the practical way to see

that motor(avionic 1780 kv) is producing 650 or 600 gram of thrust with 8.38sf prop

or what ever grm of thrust

is weight machine is used to calculate that with full throttle   
this seem to be funny so i make fun myself

but getting this information will be very very helpful to model build and improvement in model design

Iyer sir i am waiting

Quote from: wingmanbunty on August 27, 2014, 09:44:21 AM
Iyer sir i am waiting

For details of Test rig?

Bunty, read pages 2 & 3 http://www.rcindia.org/electric-power/selection-of-motor-esc-prop-and-lipo-for-foam-planes/msg194411/#new

Is that only way i mean it is good and simple way but little out of topic but how we measure a paramoror thrust or small microlight engine thrust ,is it same method at large scale.

sorry gone out of topic.

Goo d question, long, long answer

We use a Dynanometer. This can measure torque, rpm, and therefore power. Note: this is only on a motor or engine (or a Prime Mover). When a motor spins a prop, there are empirical calculations to determine the thrust, knowing the RPM.

In simple theory, a 10X7 prop will travel 7" in one revolution. Now this is in a non-compressible media! At 1000 rpm, that is 7000 " per minute. As I said, there are empirical equations (ie extrapolation of measured data for a medium) to give us this data.

Power = torque X rpm, also = rate of doing work = force X distance /time.

For a basic idea about Dynamometers read Wiki. In my college in the Mech. Engg. IC Engine Lab we had Prony Brake & Eddy Current Dynanometers. http://en.wikipedia.org/wiki/Dynamometer

Quote from: wingmanbunty on August 27, 2014, 09:27:32 AM

is weight machine is used to calculate that with full throttle   
this seem to be funny so i make fun myself

It is not funny, it is the correct concept.

The simple test rig is about as simple as it gets. You could tie the tailwheel to a scale and tie the other end to a table leg. I have done this before. But you need 2 people - one to manage the model in case it tilts over and bang! goes the prop and maybe a lot more

Thanks  sanjay sir , kk iyer sir

Here is my thrust testing setup 

Bunty,
Can't make out any detail in the video!
Pl post a pic.

kk iyer sir

i am inspired by your rig , i must say not inspired but i copied it  

ie just fitted inverted prop and fixed the setup on a book with some rubber band and coro sheet .

for testing i put the thrust line at the center of the weight machine to get batter result as you can see in the video

i perform this test to get approx idea of grm of thrust produced by different propeller

i know it is not complete setup ie amp , watt or any electrical or rpm calculation

is not there .

but i really i do not want it right now .

@wingmanbunty
Well done.
You have stumbled across a very important point!
Eent ka javab pathar se nahin, kitab se!

t

my new rc experimental project  (su -30 mki)  with the help of  Mr. bl jangid sir. its totally build up ordinary thermocol material .its in the testing phase as the project completes I will post all the details of the model, I am able to have a maiden flight of the plane.

.

Beautiful bunty. liked your plane.
plane is not much visible in the video. would love to watch clear video.

 

Very nice Bunty 

 

Great Build. !!!