needed help in calculating the thrust of an engine 
how to know that an engine produces how much of thrust

Hmmm. Interesting question, on small electrics you can put it vertical nose down on a weighing scale (electronic) and see weight with & without power. On a larger nitro? C'mon experts......

  not an expert though......but my common sense says...just take weight of the plane....Add 30-40% more (weight)would be the tentative thrust of that engine.

So if an engine can fly a 1000 gm plane easily  its thrust must be around 1300 to 1400 gm

Its Just my Common sense. I too love to know if there is any formula for it. 

With the engine running hook up the model to a spring balance and let it pull, read the spring balance reading that is your rough thrust/pull with than engine/prop combo. The model should be on the ground (smooth paved surface) and on it's wheel free to roll forward.
If you are looking for pure figures you need a dynamometer 

asinghatiya: that is a cart before the horse! We need to know the thrust to see if it would suit a particular model

boxcar: that is a good idea. Slightly dangerous though, one needs to be careful with anything over a 40

Quote from: sanjayrai55 on April 14, 2013, 10:40:38 PM
asinghatiya: that is a cart before the horse! We need to know the thrust to see if it would suit a particular model

Yeah realized this after posting.

Why to reinvent the wheel....I guess all engines come with thrust details.

OS Engines gives the following data only:

Description    Mfg. Number    Construction    Displacement (cu in)    Bore (in)    Stroke (in)    Output (hp @ rpm)    Practical RPM    Dimensions (mm)
Legend    Weight w/o Muffler (oz/g)    Muffler    Carb    Break-in Prop    Propellers


Difficult to give thrust for IC engines I guess. HP, yes; RPM, yes; therefore Torque is known. Thrust depends on prop for a fixed HP & RPM

This is quite simple - many ways to do it

http://www.rcgroups.com/forums/showthread.php?t=976027

this is just one - will work with glow aircraft engines too
if you make it more robust


You should not hook up a model nose downwards ....readings will be totally off
as a little factor called gravity will come into play.

Thrust readings are not an useful quantifier of power as there are
too many variables - it will only serve to indicate approximate performance
which in most cases is good enough.

That looks good; albeit a little complex

The gravity bit doesn't apply, as you are taking the difference of two readings, both taken with the model nose down vertical, resting on the tip of the spinner

Don't think it is any more dangerous than one's daily life. And the dangers are same with a below 40 or above 40 engine only the potential of damage differs

this is what i use for both nitro and electric....!!

but this is theoretical.. and final values may vary.. but for deciding.. i suppose this works....
http://personal.osi.hu/fuzesisz/strc_eng/index.htm

and to find the optimum prop...
http://personal.osi.hu/fuzesisz/opc_eng/index.html

the parameters are available in the engine manual..

I think just use a device to read the prop rpm on a full throttle then use online thrust calculator by giving info on prop used and rpm you got on full throttle then you cud calculate the thrust.....like a 10x6 apc electric style prop gives 1.2 kg thrust on rpm of 7731