Oldbaldfella Posted July 21, 2013 Share Posted July 21, 2013 Hi, recently took the plunge with my first effort at putting my first electric powertrain together. Unfortunately all I ended up with was a smoking engine! I bought the Phoenix 2000 electric glider airframe from HK, a 1450kv brushless outrunner to power it, a 25-30a esc and a 1500mah 11.1v lipo. On the end of it is a 10" folding prop as supplied. Giving it a trial blast in the garden, not many seconds of full power resulted in a smoking engine. I do not believe they are meant to do that! Where did I go wrong, please? Quote Link to comment Share on other sites More sharing options...
Phil Green Posted July 21, 2013 Share Posted July 21, 2013 I think your motor is far too high a kv for a large folding motor-glider prop, but the first mistake was not using a watt-meter to check the current drawn. With that prop the motor would have been working very hard indeed. A wattmeter is pretty much essential when setting up a new power train. Cheers Phil Quote Link to comment Share on other sites More sharing options...
Oldbaldfella Posted July 21, 2013 Author Share Posted July 21, 2013 Thanks Phil. If I remember right, smaller kv for a bigger prop? What kv would you recommend for that size prop? Cheers. Quote Link to comment Share on other sites More sharing options...
WolstonFlyer Posted July 21, 2013 Share Posted July 21, 2013 I would suggest something around 1000Kv for the Phoenix 2000 with the supplied prop.Such as this:**Link** Quote Link to comment Share on other sites More sharing options...
Oldbaldfella Posted July 21, 2013 Author Share Posted July 21, 2013 Many thanks Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted July 21, 2013 Share Posted July 21, 2013 I've also posted this link before, it's a free (yes free) motor/prop/battery calculator, if it doesn't have you exact motor in the database then just pick one with the same Kv you can then get an idea of the motor rpm and amps it will draw. I have found the results to be pretty close to actual readings on my combos. But a 1450kv motor on a 3s lipo will be trying to turn prop at over 14,000 rpm, would be like having a pylon racing 40 in the nose of you electric glider. Quote Link to comment Share on other sites More sharing options...
Oldbaldfella Posted July 22, 2013 Author Share Posted July 22, 2013 Posted by Frank Skilbeck on 21/07/2013 23:57:35: I've also posted this link before, it's a free (yes free) motor/prop/battery calculator, if it doesn't have you exact motor in the database then just pick one with the same Kv you can then get an idea of the motor rpm and amps it will draw. I have found the results to be pretty close to actual readings on my combos. But a 1450kv motor on a 3s lipo will be trying to turn prop at over 14,000 rpm, would be like having a pylon racing 40 in the nose of you electric glider. Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted July 22, 2013 Share Posted July 22, 2013 Posted by Oldbaldfella on 21/07/2013 10:10:29: ... I bought the Phoenix 2000 electric glider airframe from HK, a 1450kv brushless outrunner to power it, a 25-30a esc and a 1500mah 11.1v lipo. On the end of it is a 10" folding prop as supplied. ... You've got good advice so far, but you also need to be aware of the volt and amp rating of your motor. There's quite a few 1450kv motors around, and there may be some that can handle your 10" (10" by what?) prop on 3S supply. though lower kv would be better, as has been mentioned. For any given motor, battery voltage and prop size (diameter and pitch) are the factors which determine how many amps the motor will draw. Usually you can get a good idea of the right prop either from the motor manufacturer's page (if they quote a range of sizes, and a range of volts, the largest prop will correspond to the lowest voltage), from calculators, or from other users. But you should always check your actual setup with a wattmeter, for manufacturing tolerances in motors and props can make a difference. Quote Link to comment Share on other sites More sharing options...
Oldbaldfella Posted July 22, 2013 Author Share Posted July 22, 2013 Posted by Allan Bennett on 22/07/2013 08:44:11: Posted by Oldbaldfella on 21/07/2013 10:10:29: ... I bought the Phoenix 2000 electric glider airframe from HK, a 1450kv brushless outrunner to power it, a 25-30a esc and a 1500mah 11.1v lipo. On the end of it is a 10" folding prop as supplied. ... Thanks Allan. Can I go back to ic, please? You've got good advice so far, but you also need to be aware of the volt and amp rating of your motor. There's quite a few 1450kv motors around, and there may be some that can handle your 10" (10" by what?) prop on 3S supply. though lower kv would be better, as has been mentioned. For any given motor, battery voltage and prop size (diameter and pitch) are the factors which determine how many amps the motor will draw. Usually you can get a good idea of the right prop either from the motor manufacturer's page (if they quote a range of sizes, and a range of volts, the largest prop will correspond to the lowest voltage), from calculators, or from other users. But you should always check your actual setup with a wattmeter, for manufacturing tolerances in motors and props can make a difference. Quote Link to comment Share on other sites More sharing options...
Allan Bennett Posted July 22, 2013 Share Posted July 22, 2013 Yes, i.c. is much simpler in some respects. But after spending a couple of Sundays instructing a beginner with his glow-powered Arising Star, I remembered why I went electric -- no holes in the fuel lines, no disconnected clunk, no hydraulic lock in the engine, no duff glow plug, and no fuel all over my clothes and model! Here's a very simple calculator that I use to get my motor and prop size **LINK** for a new model; click on Software and then on Web-O-Calc. With that, and a wattmeter to check the actual amps, I've never had a failure with any of my dozen-or-so e-conversions yet. Quote Link to comment Share on other sites More sharing options...
Erfolg Posted July 23, 2013 Share Posted July 23, 2013 As Phil Green as written, a watt meter is essential, a must have with electric flight. You are not the first one follicley challenged one (I am sure I beat you) to be caught out in the way you describe. I have no issues with calculators, as they are useful in confirming your own judgement or guess. Yet neither they or the data sheet, if available, can be solely relied upon. The watt meter tells you what is happening. You are a lucky guy, if you were unlucky, the motor shorting out, or the ESC frying would probably wipe out your model and equipment, if occurring in the air. I am not trying to frighten you or make it out to be difficult to fly electric, because in essence it is not. It just needs a little care, in setting up. Quote Link to comment Share on other sites More sharing options...
Oldbaldfella Posted July 23, 2013 Author Share Posted July 23, 2013 Thanks for all that. I have just installed a 1050kv and a mate at the club has a watt meter which we can try so........ I have to say, the lower kv motor seems to be pulling much stronger. Weird! Much obliged. Quote Link to comment Share on other sites More sharing options...
Swissflyer Posted July 23, 2013 Share Posted July 23, 2013 Quote of Frank Silbeck I've also posted this link before, it's a free (yes free) motor/prop/battery calculator, if it doesn't have you exact motor in the database then just pick one with the same Kv you can then get an idea of the motor rpm and amps it will draw. I have found the results to be pretty close to actual readings on my combos. Quote of Allan Bennet Here's a very simple calculator that I use to get my motor and prop size **LINK** for a new model; click on Software and then on Web-O-Calc. With that, and a wattmeter to check the actual amps, I've never had a failure with any of my dozen-or-so e-conversions yet. Totally agree with Frank & Allan These two tools complement each other. DriveCalc will also warn you if you are going to exceed max. safe prop rpm. One can learn a lot by using DriveCalc to measure one’s own motors and finding that predictions really are within 3% when you do it well. Above all it lets you see that max power claimed by HK etc. are often fictions to be avoided. WebOCalc is especially useful in setting up the right prop diameter & pitch together with the right kV motor for your model. There is a lot of sophisticated physics built in the model that includes the prop constants for all the props it suggests. Props are modelled using the Abbot equations which will let you discover a lot of “free” thrust by optimizing prop diameter & pitch speed. BTW Oldbaldfella, a correctly sized 1’450 kV motor on 3S with a 10x6 folder (more like an 11 inch prop) is going to try and draw 600W so your smoke was well justified. If you had run it on 2S, it would have drawn 185W & given you about 1kg of thrust at 20-25A & might have survived. So please follow Frank’s suggestion & get familiar with DriveCalc. I do hope you next flight is less smokeful BR Mark Quote Link to comment Share on other sites More sharing options...
Oldbaldfella Posted July 25, 2013 Author Share Posted July 25, 2013 Once again, many thanks all!!! The 1050kv is now installed and successfully maidened yesterday. There have been some staggering amounts of thermal lift down here recently which hopefully will continue. Quote Link to comment Share on other sites More sharing options...
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