Engine to thrust using prop

[Gibbo]

Guys (and the awesome women)..

 

What would you classify as an 'efficient' Engine to thrust output ratio with a water cooled motor?

 

say 1000cc equals 100kg of thrust at 70% of MaxRpm.

 

 

[RickH]

Hi gibbbo

 

your question is a little rhetorical. Thrust output is going to depend on engine h.p. propsize pitch etc. etc. e.g.

 

1000 cc VW engine puts out somewhere around 35 - 40 h.p. 500 cc rotax engine puts 50 h.p. 1000 cc BMW m/cycle engine puts out around 72 h.p.

 

Check out the RAAus website there are some very good articles on horsepower thrust etc relative to the prop. Regards RickH

 

 

[Gibbo]

I suspect I didn't make it clear.. Dumb Moment.

 

A better phrase might be 'Reactice force'.. Eg early purejets produced maybe 900lbs of thrust in the me262, The japanesse were able to produce 360lbs of thrust using a 53hp engine using an afterburning ducted fan (http://www.meteorflight.com/A55D74/meteor.nsf/pages/jet_age-tsu11). What would a jabiru 80hp (ave prop pitch) produce in terms of reactice force?

 

 

[RickH]

Gibbo

 

like I said mate checkout the RA_Aus web site Thrust produced is dependant on Prop speed, pitch and diameter as well as engine horsepower(ie work done or in the case of engines work capable of being done by the engine in question).Diameter of prop dictates the dia of the tube of air being moved by the prop and in combination with pitch and the rpm gives the volume of air being moved per second. Air in standard atmospheric conditions weighs 1.225 kg/cuM work it all out and you get kilograms or if you like pounds of thrust per second. kilograms or pounds moved per sec(thrust) equates to H.P ie one horsepower =550foot pounds per second. ie one pound of air is moved 550 feet in one second. Like I said check out the website it's all there and a lot more. Jet engine calcs are a bit more complicated ie you have to take into account pressure volume and temperature both in and out ie P1V1T1=P2V2T2 if you manage to spend the time to learn the relevance of this equation you'll have jets sorted as well but you probably don't want to go that far.

 

Regards RickH