stuart macrory Posted January 21, 2009 Share Posted January 21, 2009 if any ic engine is running a its lowest idle point without stalling but the plane is still creeping foward is it true or false that it could be doing this because the low needle is too lean? i know for a fact that its not incorrect prop choice. Quote Link to comment Share on other sites More sharing options...
David Perry Posted January 21, 2009 Share Posted January 21, 2009 Two points there- lean low running jet and lowest idle. If the engine is at its lowest idle possible, under any circumstances, then it's producing too much thrust , so change the prop or the engine or the revs. Or live with it! If the engine is idling too fast then i'd say yes, adjust the slow running needle. Or close the throttle barrel a bit more, which will necessitate adjusting the slow running needle.. d Quote Link to comment Share on other sites More sharing options...
stuart macrory Posted January 22, 2009 Author Share Posted January 22, 2009 i remember with a previous plane i owned was doing the same and a guy kindly helped me,he either richened the low end or leaned it but whatever he done it allowed it to idle lower without it stalling Quote Link to comment Share on other sites More sharing options...
stuart macrory Posted January 22, 2009 Author Share Posted January 22, 2009 i suppose what im really trying find out is if you have a model ideling and you lean the low needle valve what will happen(will the revs increase or decrease) Quote Link to comment Share on other sites More sharing options...
David Perry Posted January 23, 2009 Share Posted January 23, 2009 Stuart, Ah, different question. the answer is "depends". If the mixture is too rich to start with, the revs will increase. If the mixture is correct or too lean to start with, the revs will fall or go to zero, unless of course they go up, the engine gets hot then they go to zero.... If IC engines were as easy as abc, there'd be no fun anymore! david Quote Link to comment Share on other sites More sharing options...
Dave S. Posted January 23, 2009 Share Posted January 23, 2009 "If IC engines were as easy as abc, there'd be no fun anymore!" Ringed engines are more fun, then? Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted January 23, 2009 Share Posted January 23, 2009 Dave You know all about "bores" then How about expensive ones? Ringed things (the fairer sex / wives) have cost me about 6 houses -a threesome of boats ( I lived on) & goodness knows how many classic cars I've renovated, not to mention ex-family that don't speak anymore ! Plus one " ex" wouldn't send me all my aeromodelling gear after I gave her my house in France 'She said the postal system told her it might be bomb -making equipment Off thread again -but run the engine ( a couple of tips here ) & only alter your idle screw by miniscule amounts once you've got the top end right ( slightly rich-drop of about 200 rpm from max.) I must emphasise that the top end must be OK before the idle is set . I bet someone is going to disagree & I know it all depends on the engine ! PS Fit a new plug before you do anything ! Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted January 23, 2009 Share Posted January 23, 2009 Now the flashing adds are covering some of my message on my screen Is it on yours Quote Link to comment Share on other sites More sharing options...
Dave S. Posted January 23, 2009 Share Posted January 23, 2009 Myron, no problem reading you loud & clear here. Only two vindictive ex-wives to my name; you make me feel like a beginner! Dave Quote Link to comment Share on other sites More sharing options...
simon barr Posted January 23, 2009 Share Posted January 23, 2009 I don't know, have you guys no staying power? 28 years and counting... Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted January 23, 2009 Share Posted January 23, 2009 Dasve Just seen you are in Finland from your details Any nice aeromodelling type ladies there ,who's father owns a brewery and a runway and a big shed and is over a hundred years old .??? I have my thermal underwear ready to go ! Quote Link to comment Share on other sites More sharing options...
flytilbroke Posted January 23, 2009 Share Posted January 23, 2009 No fool like an ;;;;;;;; Well I think you know the rest. One was enough for me, years together, years apart, more years together. Now I might be the Old Fool Quote Link to comment Share on other sites More sharing options...
David Perry Posted January 23, 2009 Share Posted January 23, 2009 Dave s,...brilliant. I missed that pun completely! david Quote Link to comment Share on other sites More sharing options...
Malcolm Fisher Posted January 23, 2009 Share Posted January 23, 2009 I might have been much luckier than Myron - still with my first wife after going on for 50 years... Not sure that it's been any cheaper though... Quote Link to comment Share on other sites More sharing options...
Dave S. Posted January 23, 2009 Share Posted January 23, 2009 Myron, I'll let you know if find two like that, the first will be mine! Mind you, I enjoy home brewing, will have a runway next spring, have several sheds, and two daughters! Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted January 26, 2009 Share Posted January 26, 2009 Well now its totally off post not a sking term , lets set stuart right. If your model creeps forward even at tick over them you simply have too much thrust .Simple. To remedy simply reduce thrust by fiting a lower pitch prop or slowing the engine . The slow running needle is for mixture control not engine speed control . E.D. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted January 27, 2009 Share Posted January 27, 2009 Stuart To follow on from the E.D.'s advice. All IC engines have a minimum speed below which they will not run (actual speed depends on the engine and the fly wheel effect of the prop). So with a prop attached there is a minimum thrust (actual thrust depends on the diameter and pitch of the prop). If that minimum thrust will move the model (it depends on the weight of the model and the nature of the runway surface) then it will move. Remember many full size aircraft move at engine idle when the wheel brakes are released and models tend to have an even higher power to weight ratio! I hope this helps explain what is going on. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted January 27, 2009 Share Posted January 27, 2009 Well put Simon . One thing I did forget was to ask if Stuart is using a model restraint ? You are Stuart arn't you ? Quote Link to comment Share on other sites More sharing options...
stuart macrory Posted January 27, 2009 Author Share Posted January 27, 2009 yes i am indeed but i still dont think it is ideal to have a model creep foward on idle,it will also increase landing speed,the guy that owned the plane before me used the same set up with no problems and as i say i had this problem with another model and a guy done something with the low end needle to sort it.when he adjusted the needle it lowered the revs at idle without it cutting out which it was doing with me when i lowered the throttle trim. i had the model ideling at its lowest point with out it cutting,it was creeping foward,this guy made the revs drop at idle even lower to stop the model creeping with out it cutting the engine.he done all this by adjusting the low end needle valve only. Quote Link to comment Share on other sites More sharing options...
Braddock, VC Posted January 28, 2009 Share Posted January 28, 2009 Stuart, first off, are you sure you've got the minimum revs. On some engines there are three "needles", one for the top end, one to adjust the idle mixture and the third needle is the throttle stop. This last "needle" is screwed into the throttle body and can have a small helical spring around it so it doesn't vibrate free, it controls two things, 1st the position of the throttle barrel at idle and 2nd it acts as a guide for the throttle barrel as it fits into a helical groove machined into the barrel. If you have a computer radio the first function is almost obsolete, simply unscrew it so that when you look down the throat of the carb you can actually see that none of the "hole" in the rotating barrel is visible, don't undo it too far or you'll discover the third function which is to stop the throttle barrel falling out. You then set up your end point on the idle side of your transmitter throttle stick so that it's just possible to see the hole in the barrel, about 1 mm should be a good start point. Then start your engine and if it won't idle move the end point on the tranny til it does, if it idles too fast slow it down on the end point until it's as slow as you want. Approx 2000 to 2500 revs per min is about right if you can get the use of a rev counter. If you don't have a computer radio, ask one of your club mates to help you set up the idle speed as opposed to the idle mixture, it's a bit more complex than the computer tranny method. Good luck. Quote Link to comment Share on other sites More sharing options...
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