eightyknots Posted June 19, 2015 Posted June 19, 2015 Yep. That's the one. Thanks.I was interested in comparing the electric motor with a 4 cylinder petrol engine. Taking the Jabiru J170-D with a 2200 engine: Engine Weight (complete to fit, without exhaust system) = 62 kg Full fuel 135 l = 97 kg Useful load at full fuel = 260 kg - 97 kg = 163 kg 135 l @ 20 l/hr = 6.75 hrs Electric motor: Motor weight (motor + controller circuitry + 21 LiPo batteries): 38 kg 135 l fuel weight in batteries = 75 batteries Useful load: 260 kg + (62 - 38) = 260 + 24 = 284 kg Total number of batteries equivalent to full fuel and engine = 21 + 75 = 96 21 batteries = 1 hour's power, 96 batteries = 4.5 hrs. The big question to answer is: "How many units of horsepower are required to maintain straight and level flight at a constant speed?" In other words, if L = W, how much Thrust is needed to balance Total Drag? OME This seems to happen on many threads: the ubiquitous comparisons with Jabiru 2200 motors.
Downunder Posted June 19, 2015 Posted June 19, 2015 I don't think electric power can be directly related to petrol driven aircraft. At Least not in a linear fashion. It is quite easy to have zero power usage (prop stopped) in a shallow descent. If you have a good glide ratio even better. Anyway, this looks like fun!! 1 1
Phil Perry Posted June 19, 2015 Posted June 19, 2015 I might even do Pommy Phil's trick of lubricating the grey cells with some Cab Sav.OME OI,. . . ! - - - It doesn't work Sir. . . Tried it a few times, great relaxative yes,. . . but not for calclubrication. . . Try some French white cider ,.. oops, sorry Cidre. . . tastes a bit funny but kicks like an angry Roo. . . . . I'm still trying to find Stan Deyo,. . . . he allegedly had access to some formulaic notes with regard to electro anti-gravitics. . . . have not found where he's hiding . . .was very big on the Cosmic Conspiracy rolling lecture tours in OZ in the mid seventies. . . perhaps we could merge the science and consign petrol engines to the history books ? Bet the King of Saudi Arabia will be a little miffed about that. Anyway, best of fortune with the calcs. Don't post on here if you crack it, as someone else will make millions. . .walls have ears an all that. . . . .
Phil Perry Posted June 19, 2015 Posted June 19, 2015 I am hoping Jabiru go into the micro reactor business What. . .? so you can take the mickey out of the build quality of the fuel rod coolant circuit ? ? ? tut tut. . . . 2
fly_tornado Posted June 20, 2015 Posted June 20, 2015 No Phil, I am sick of paying top dollar for foreign imports, I want the simplicity of a direct drive, air cooled steam turbine, that you can fix with fencing wire and lead sheeting beyond the black stump. 1 1
Bikky Posted June 20, 2015 Posted June 20, 2015 Anyway, this looks like fun!! It sure does. I'm not sure about a hard landing in that seating position though ...
Phil Perry Posted June 20, 2015 Posted June 20, 2015 No Phil, I am sick of paying top dollar for foreign imports, I want the simplicity of a direct drive, air cooled steam turbine, that you can fix with fencing wire and lead sheeting beyond the black stump. OK,. . "Foreign". . . .er,. . . .so if Jabberwocky sold a nuclear drive, would they have it imported from Bexland Manufacturing PRC INC. perhaps ? . . .just wunderin. . . ( Love the steam turbine idea though. . . only one downside, have you checked out the price of fencing wire lately ! ! sheeesh .)
Phil Perry Posted June 20, 2015 Posted June 20, 2015 It sure does. I'm not sure about a hard landing in that seating position though ... Ditto mate,. . . . a stiff landing on tarmac could do bad things to one's spine methinks,. . .nice plaything otherwise though.
Keenaviator Posted June 20, 2015 Posted June 20, 2015 It sure does. I'm not sure about a hard landing in that seating position though ... How do stunt people normally land when jumping off buildings etc onto a pad?
Old Koreelah Posted June 20, 2015 Posted June 20, 2015 OK,. . "Foreign". . . .er,. . . .so if Jabberwocky sold a nuclear drive, would they have it imported from Bexland Manufacturing PRC INC. perhaps ? . . .just wunderin. . . ( Love the steam turbine idea though. . . http://www.realclearscience.com/blog/2014/07/why_not_nuclear-powered_aircraft.html http://jalopnik.com/5705672/the-xb-70-valkyrie-almost-the-worlds-first-nuclear-aircraft 1
Bruce Tuncks Posted June 20, 2015 Posted June 20, 2015 I reckon they should be using LiFePO4 which have a bit less energy than LiPO batteries but are safer. I've been using a LiFePO4 for over a year now to start the Jabiru. Model aircraft have mainly become electric and the manufacturers of other motors are going out of business. Mind you, 15 mins is the typical length of a model flight.
Litespeed Posted June 21, 2015 Posted June 21, 2015 Yep , 15 mins is a normal flight but that is often pilot limited for concentration and the want for mega performance and low wing loadings. I have a small hangars worth of models and many could easily be setup for 1 hour or more of flight. AS for the pilot position- could end up with a lithium headbanging as well. 1
Phil Perry Posted June 21, 2015 Posted June 21, 2015 How do stunt people normally land when jumping off buildings etc onto a pad? Sorry, but I don't think that example invalidates the comment Sir. . . there have been ( thankfully few ) some instances in the past where trike pilots, ( And a Kolb Twinstar crew ) sitting upright in canvas seats, suspended above a grp pod enclosure, who have still suffered "some" spinal injuries as a result of heavy landings so it is all a matter of degree. . . . vertical impact velocity and circumstances / design / type I guess. . . It just "Looks" a bit precarious with that seating arrangement, Could be just me getting old and cowardly. Don't really see a fair comparison between this, and a well arranged and choreographed movie stunt though . . . Phil 1
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