jordy Posted August 1, 2009 Posted August 1, 2009 Hey guys this might sound like a basic question but....... is it ok to ground run an engine ( In this case a 582 in a drifter) without a prop and if so are there any precautions.
Guest Qwerty Posted August 1, 2009 Posted August 1, 2009 No mate. The prop is the only flywheel that the engine has. The prop also provides constant load to the engine which I seem to remember is significant. Short answer....No.
hihosland Posted August 1, 2009 Posted August 1, 2009 Yep one precaution "run like hell!!!" 'cause if you get it to start without a fly wheel, it will instantly over rev and tear itself to pieces.
Yenn Posted August 2, 2009 Posted August 2, 2009 Interestingly, I tried to turn over a jab engine without a prop and the electric starter couldn't turn it with out the flywheel effect.
Guest brentc Posted August 3, 2009 Posted August 3, 2009 Interestingly, I tried to turn over a jab engine without a prop and the electric starter couldn't turn it with out the flywheel effect. I have had no such problems running my Jabiru engine without a prop and have never heard of such a complaint. The flywheel is at the rear of the engine and the prop is not the flywheel so it has no relevance.
tangocharlie123 Posted August 3, 2009 Posted August 3, 2009 Water cooled Don't run a water cooled engine for more than a minute or two without a prop as it has the possibility to overheat as there is no air moving over the radiator. Cheers
Old Koreelah Posted August 3, 2009 Posted August 3, 2009 Surely you jest. Jabiru advise against running without the prop IN CAPITAL LETTERS so there must be a reason. Having a flywheel at the rear is OK but perhaps the engine is designed around having the additions flywheel effect of the prop at the front to reduce twisting loads on the crank. Jabiru put loads of design work into making it light, so I bet the engine relies on the prop for some of its flywheel effect. Lets be very careful with advice here. Old Koreelah
Guest brentc Posted August 3, 2009 Posted August 3, 2009 Indeed the manual says this below, however my comments were moreso regarding: Interestingly, I tried to turn over a jab engine without a prop and the electric starter couldn't turn it with out the flywheel effect.' May I suggest Ian that you try charging your battery if it won't turn over! I've had this discussion with the factory before otherwise I wouldn't have posted, the warning is purely regarding heat damage. New engines, tight rings, easily over-revved etc as it can get away from you very quickly without a prop. You don't see car engines self destructing whilst sitting at the traffic lights! Those Jabiru propellors would have to be the most unbalanced flywheel to ever go on an engine! WARNING Engine MUST NEVER BE RUN WITHOUT THE PROPELLER. Damage will occur in this state.
Guest ozzie Posted August 3, 2009 Posted August 3, 2009 Auto engine has either a very heavy flywheel or a convertor pumping oil for the auto transmission. unbalanced or not the prop is an effective flywheel. accelleration rates need to be controlled. if a two stroke say a robin 440, idles normally at 1200 rpm and removing the direct drive prop and starting will give you 3500 idle i think from memory. and is wizzed right up there real fast.
JG3 Posted August 4, 2009 Posted August 4, 2009 I've ground run both 447 and 912 engines without props. No problems, but be very careful with throttle as they can over-rev very quickly without the load. JG
Yenn Posted August 5, 2009 Posted August 5, 2009 My engine was the 1600 jab and yes it does have a flywheel, but it is very light and the battery was used in a Corolla with no problems. It just couldn't get going enough to get past the first compression.
Knighty Posted August 6, 2009 Posted August 6, 2009 Hey guys this might sound like a basic question but....... is it ok to ground run an engine ( In this case a 582 in a drifter) without a prop and if so are there any precautions. I have started and run a 582 without a prop just to check the timing at idle with a strobe light. I had a funny feeling about getting too close to a 72 inch 3 blade mincer muncher and dicer. No problems occured however the idle was way too high and the motor was very twitchy on throttle responses. Probably not a good idea to run the engine without a prop unless you really have to? If you start your engine on idle as you normally would if you're using choke expect it to idle at around 3500, thats the only advice and info I can give you, I hope it helps. Knighty
Guest ozzie Posted August 6, 2009 Posted August 6, 2009 Knighty when they run conties and lycs in a test cell they use a load prop basically a short club that does not develope much thrust or noise but is suitable to give adequate load for the engine. years ago when i worked for OMC evinrude/johnson. the engines where test run and tuned in a tank whith a no thrust load prop. maybe you should look at something like that or try and transfer the timing marks to the other end or just static time it. i hate tuning the pumper carbs on my lazair you have to get in between the leading edge and the prop to get to them. If i can i run them on the test stand first and then i can get behind the engine. still scarey but risking a finger is better than offering the head. ozzie
rick-p Posted August 17, 2009 Posted August 17, 2009 Ozzie, if that is a photo of your head in the last post...please go ahead and offer it !! Hey girls is it that time of the already!
Guest ozzie Posted August 21, 2009 Posted August 21, 2009 The fan will be providing enough load for a bench test. I really like the accurate balanced throttle control sheesh real pro this guy. i still would not run any engine with no load or flywheel. Onya Major!
Guest Qwerty Posted August 22, 2009 Posted August 22, 2009 WHY???? This tread is just insane. Who knows what harmonics are being developed with no prop. I dare someone to ask Rod Stiff about running Jabs with no prop. Again WHY??? Bahhh I give up.
Guest Maj Millard Posted August 22, 2009 Posted August 22, 2009 The main damage you would do by running an engine and gearbox without a prop is at the gearbox cog contact surface. It is designed and adjusted to have a constant load on the contact surface, not an off/on hammering contact. There could also be possible crankshaft stresses introduced, that they are not designed for. Not the smartest idea really...........................................................................thumb_down
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