Nick Farrow Posted May 11, 2010 Share Posted May 11, 2010 Hi, I was wondering what is so special about the props for electric flight. I appreciate why this might be for slow fly, but not for sports type flying. So you can get an APC 9x5 on a typical foamy, that could either be and e' type or not (e.g APC 9x5e). As far as I can see these take about the same revs as non 'e' types, so is there another critical difference? Just curious! Thanks nick Quote Link to comment Share on other sites More sharing options...
Ultymate Posted May 11, 2010 Share Posted May 11, 2010 I think Nick that the "E" props are more lightly constructed than the IC versions, being that they are not subjected to the same stresses and vibrations. Therefore I would say at a pinch it's ok to fit an IC prop to an electric sports model but never the other way round. This is my understanding Edited By Ultymate on 11/05/2010 12:29:33 Quote Link to comment Share on other sites More sharing options...
Plummet Posted May 11, 2010 Share Posted May 11, 2010 Just guessing, but... Vibration? Flywheel effect? An electric motor gives thrust through all 360 degrees. An IC one only for perhaps 60 degrees on 360 or 720 for four strokes. Also the flywheel effect of the prop is actually driving the engine during the compression stroke. An IC prop has a lot more force on it than a leccy one. Also, the aerofoil section of the two types is different, so the drag/thrust characteristics will differ. So a 9x5 leccy prop and a 9x5 IC prop may draw different currents when both used on the same lecci setup. Plummet Quote Link to comment Share on other sites More sharing options...
Bruce Richards Posted May 11, 2010 Share Posted May 11, 2010 E props are more lightly constructed. This is possible because they do net need to contend with the shock loadings generated by an I/C engine with one power stroke per revolution. Electric motors deliver power in a smoother fashion. Bit slow of the mark there Edited By Bruce Richards - Moderator on 11/05/2010 12:31:41 Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted May 11, 2010 Share Posted May 11, 2010 Yup...thats about it. Quote Link to comment Share on other sites More sharing options...
Plummet Posted May 11, 2010 Share Posted May 11, 2010 Isn't there something we could disagree about. It would be more fun! P Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted May 11, 2010 Share Posted May 11, 2010 iI don't do electric flight so I might be dead wrong here - but when I look at props on electric powered models they seem to me to have a pitch profile change very close to the hub - like a sudden increase in pitch in this area. You don't see this on ic props. It could be that actually, aerodynamically, that is the absolutely most efficient way of forming a prop - ie that you need the apparent pitch increase near the hub because it is the slowest moving part of the blade - and maybe ic just doesn't do it because it would weaken the blade close to the hub. Don't know - has anyone else noticed this or got any views on it? BEBEdited By Biggles' Elder Brother on 11/05/2010 15:03:16 Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted May 11, 2010 Share Posted May 11, 2010 Posted by Plummet on 11/05/2010 15:01:00:Isn't there something we could disagree about. It would be more fun! P Dont tempt fate - we are busy on admin work and cant afford to be throwing cold water on you lot! Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted May 11, 2010 Share Posted May 11, 2010 Posted by Biggles' Elder Brother on 11/05/2010 15:02:19:iI don't do electric flight so I might be dead wrong here - but when I look at props on electric powered models they seem to me to have a pitch profile change very close to the hub - like a sudden increase in pitch in this area. You don't see this on ic props. It could be that actually, aerodynamically, that is the absolutely most efficient way of forming a prop - ie that you need the apparent pitch increase near the hub because it is the slowest moving part of the blade - and maybe ic just doesn't do it because it would weaken the blade close to the hub. Don't know - has anyone else noticed this or got any views on it? BEBEdited By Biggles' Elder Brother on 11/05/2010 15:03:16 You could be right there BEB - but just to keep Plummet happy.....dont talk such rubbish man Quote Link to comment Share on other sites More sharing options...
Plummet Posted May 11, 2010 Share Posted May 11, 2010 Rubbish? Rubbish? You think that was rubbish? You should see some of the other stuff I have written! Stomp stomp stomp. P Quote Link to comment Share on other sites More sharing options...
Roberto Gava Posted May 11, 2010 Share Posted May 11, 2010 As far as I know, IC shafts are subjected to strong torsional vibrations that should be supported by the prop. Also the prop works as a flywheel to give smooth idle. In electric motors there isn't those requirements so props can be lighter to give more acceleration and its shape could be optimized aerodynamically because there is less structural requirements. Quote Link to comment Share on other sites More sharing options...
Nick Farrow Posted May 12, 2010 Author Share Posted May 12, 2010 Hi Guys, Thanks very much some good stuff here! nick Quote Link to comment Share on other sites More sharing options...
Erfolg Posted May 12, 2010 Share Posted May 12, 2010 Yep I am sure the consensus on the vibration/cyclic nature is correct. I do not know where I saw it, on U tube, but some one, has somehow used a strobe? to show how a IC prop pulses slightly backwards and forewords on each rev, showing clearly two tracks when moving. Yet when turned by hand, both tips tracked the same path. I did think, it could be that each blade had a differing stiffness level. I just accepted it would happen, but would it be sufficiently great to practically measure. This really surprised me, I believed the variation in angular velocity took place, again thinking the practicality of measuring the change was not practically achievable without considerable effort. Measuring vibration on the 3 axis should be do able. But who would cares? One thing I have noted though, there seems to be no one design concept or material for electric props. Ranging from, slow fly, then JKX carbon to folding propeller systems. Erfolg Quote Link to comment Share on other sites More sharing options...
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