Geoff S Posted May 24, 2015 Share Posted May 24, 2015 The old rule of thumb of 100 watts/lb for aerobatic performance was established in the days of brushed motors , which were both heavier and generally much less efficient than the brushless outrunners we use now. However there's still quite a price range in motors when we compare the Hackers and the Axis with the cheap Chinese motors sold by (say) HobbyKing. I opted for a medium quality motor for my latest project which seems to give better performance than I expected from the cold numbers (max 580 watts for a 6lb model). Am I kidding myself that paying for a fancier motor has paid off in better performance that (say) an XYH 5055? After all they all use rare earth magnets and bearing quality will probably only be felt in long term service. In fact the only motor I've ever had fail was my first brushless, an Axi which shed its magnets. In other words, why should I pay more than rock bottom prices for motors? Are the expensive ones really worth the extra? Geoff Quote Link to comment Share on other sites More sharing options...
Bill_B Posted May 24, 2015 Share Posted May 24, 2015 I think the rule of thumb is 'you get what you pay for', but as with everything in life that's mass produced there'll always be the odd one that's a duffer, and I'm sure your Axi is an example. I've had quality motors and cheap ones and in my experience the branded ones are superior. I have a Hacker, 3 Mega motors and 4 HETs. The HETs are being abused in EDFs and they don't show any sign of distress and the others seem faultless too after much use. Possibly the worst I've encountered are the Hobbyking NTM series (I had two motors that had early life bearing failure and one had a rusty armature when I stripped it), and Emax motors. I've had two of those shed magnets. I guess it all depends on how much value you put on your plane. For small foamie park flyers I wouldn't be too bothered, but for something larger, more expensive or very fast I would always opt for the 'quality' branded name motor, not to mention the ESC, which is another can of worms. Quote Link to comment Share on other sites More sharing options...
Stuphedd Posted May 24, 2015 Share Posted May 24, 2015 a very difficult question to answer truthfully .. If you are happy with what you have , then its the right one , I now over 200 brushless motors of all sorts except MVVS , which on reputation are the best , I have many top end motors , but my favorites are Hyperion , which just go on and on , Yes bearings can be a problem , the place I get mine have 3 qualities , cheap ones from China , not so cheap ones from China , and expensive but excellent ones from Japan . Good motors I recon use brgs from Japan, For build quality HIMax are well put together with their windings protected with shields , but I recon you can get bad ones of all makes as you can good ones . Unless you are a competion flyer, and need the insurance and the good feeling of paying alot for a motor then for me its cheap and cheerful cheers Quote Link to comment Share on other sites More sharing options...
Bill_B Posted May 24, 2015 Share Posted May 24, 2015 Surely reliability is an important consideration? In my experience there's no fun in having a motor throw a magnet mid flight, or having a bearing crumble for that matter. Having read many reviews about various motors on Giant Shark and Hobbyking web sites, there seem to be many cheap motors that have dodgy build quality. Digressing momentarily onto ESCs, I have only ever had one cheap ESC fail (brushed or brushless) and I was very lucky to be able to land the model, wheels up, with no damage. I have a collection of various brands of ESCs and most have been run at or near their limits without issue, but the only one that failed was included in a kit and advertised as 'uprated', typical! Quote Link to comment Share on other sites More sharing options...
andyh Posted May 24, 2015 Share Posted May 24, 2015 I think it's probably a case of buying appropriately - ie cheap & cheerful for general club/sport stuff & something better for expensive (either in ££ or build-hours) or comp stuff the law of diminishing returns probably applies too - I dare day the hacker/Axi stuff is better made, but is proportionately less good value, purely because of western production costs, marketing, etc. I think lekky motors are also far more of a commodity than IC engines - I can't image ever drooling over an electric motor in the same way I might over a Laser - "phwoar - you could run a washing machine with that" Quote Link to comment Share on other sites More sharing options...
Bill_B Posted May 24, 2015 Share Posted May 24, 2015 Oh I don't know, my Hacker has a certain 'je ne sais quoi' about it. The beautifully executed purple anodising, huge silky smooth bearings and as for its rigid shiny shaft, well, what can one say! Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted May 24, 2015 Share Posted May 24, 2015 Only ever had one motor fail on me, and that was the HK Contra Rotating jobbie, one of the motors burnt out under the first power test in the garden after no more that 2 mins running and 5 secs at full chat - was it indicative of general poor quality or a "Friday afternoon" motor - I don't know - the rest - a real mix of dirt cheap HK things and upper middle price ranges all work fine.... Shafts on the cheaper one seem to be soft steel and bend quite easily, whilst oddly the most expensive one (a Multiplex) shattered a shaft in a crash (it looked to me like it was sintered steel) At the end of the day you pays your money and takes your chance..... Quote Link to comment Share on other sites More sharing options...
Geoff S Posted May 24, 2015 Author Share Posted May 24, 2015 I wasn't only thinking of longevity or reliabilty. I was thinking about performance when new. Will an expensive motor deliver more torque/power for the same input current and voltage assuming similar specs (ie kv, max permissible current etc). Are they more efficient and give better flying and hence longer duration from the same energy source? I can see they're better made and will last longer but I wonder what makes a good motor better than a cheap one in the short term? As a retired electronics designer I know why speed controllers can be better for more money. I want to know why a motor would be. When I bought my Axi, they were the cheaper alternative to Hacker etc. The Foxy I bought for my Fantasy is Puffin's replacement for the Axis they first introduced to the UK. Geoff Quote Link to comment Share on other sites More sharing options...
andyh Posted May 24, 2015 Share Posted May 24, 2015 Posted by Bill_B on 24/05/2015 23:14:18: Oh I don't know, my Hacker has a certain 'je ne sais quoi' about it. The beautifully executed purple anodising, huge silky smooth bearings and as for its rigid shiny shaft, well, what can one say! paging Dr Freud ... if the cheapo stuff makes it through the initial down-slope of the "bathtub curve", then it's likely to last longer than whatever model I've put it in, although maybe that's just me Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted May 24, 2015 Share Posted May 24, 2015 Better bearings so less friction losses Smaller air gap between windings and magnets due to closer manufacturing tolerances so more powerful magnetic reaction generated Stronger fixed magnets How much difference does it make? probably not enough to really notice unless your are competition flying But define quality? I recall a corporate "re-education" program... which asked the question which is better quality a plastic carrier bag or a Guchi handbag? The answer - depends on your use for the bag, if its to carry shopping from Tesco's then the Guchi bag is a miserable failure as it doesn't meet the requirements! Edited By Dave Hopkin on 25/05/2015 00:10:36 Quote Link to comment Share on other sites More sharing options...
Andy Hat Posted May 25, 2015 Share Posted May 25, 2015 I like the cheap Emax motors but you need to ensure the cooling is adequate. As part of my "electric motor training" I killed TWO BL2826 in the same model. Initially, I blamed the motors having badly attached magnets, cheap materials etc. After I added proper airflow/cooling, the third Emax motor still runs great after many flights. A posher motor might have survived without better cooling but it doesn't mean that you shouldn't have it. It's tempting to convert IC models to electric by just sticking in an 'equivalent' brushless motor but the models I have converted (quite a few now) didn't allow for adequate cooling by default. Some models that are designed for electric still lack good cooling. With IC, I would swap my few 'treasured and valuable' IC engines between them. With electric, the setups are so cheap these days (as are the electronics, servos etc), you can have many models ready to fly. There's a place for Hackers and the pricy stuff but the quality and reliability of cheap motors is so good and they are almost (dare I say it) disposable. Quote Link to comment Share on other sites More sharing options...
Geoff S Posted May 25, 2015 Author Share Posted May 25, 2015 Posted by Dave Hopkin on 24/05/2015 23:53:31: Better bearings so less friction losses Smaller air gap between windings and magnets due to closer manufacturing tolerances so more powerful magnetic reaction generated Stronger fixed magnets How much difference does it make? probably not enough to really notice unless your are competition flying But define quality? I recall a corporate "re-education" program... which asked the question which is better quality a plastic carrier bag or a Guchi handbag? The answer - depends on your use for the bag, if its to carry shopping from Tesco's then the Guchi bag is a miserable failure as it doesn't meet the requirements! Edited By Dave Hopkin on 25/05/2015 00:10:36 Quality? Perhaps I'd better reread 'Zen and the art of motor cycle maintenance' by Robert Persig. I first read it firstyears ago when I thought it was all about motor cycles when IIRC quality is one its issues You may well be right about more acurate and closer tolerances making for more power at the output shaft for electrical power in. That's certainly the impression I got from my initial flights with the 'one step up the ladder' Foxy motor/esc combo but perhaps I'm trying justify the cost to my parsimonious self Geoff Quote Link to comment Share on other sites More sharing options...
Dave Hopkin Posted May 25, 2015 Share Posted May 25, 2015 Posted by Geoff Sleath on 25/05/2015 11:01:39: Posted by Dave Hopkin on 24/05/2015 23:53:31: Better bearings so less friction losses Smaller air gap between windings and magnets due to closer manufacturing tolerances so more powerful magnetic reaction generated Stronger fixed magnets How much difference does it make? probably not enough to really notice unless your are competition flying But define quality? I recall a corporate "re-education" program... which asked the question which is better quality a plastic carrier bag or a Guchi handbag? The answer - depends on your use for the bag, if its to carry shopping from Tesco's then the Guchi bag is a miserable failure as it doesn't meet the requirements! Edited By Dave Hopkin on 25/05/2015 00:10:36 Quality? Perhaps I'd better reread 'Zen and the art of motor cycle maintenance' by Robert Persig. I first read it firstyears ago when I thought it was all about motor cycles when IIRC quality is one its issues You may well be right about more acurate and closer tolerances making for more power at the output shaft for electrical power in. That's certainly the impression I got from my initial flights with the 'one step up the ladder' Foxy motor/esc combo but perhaps I'm trying justify the cost to my parsimonious self Geoff Dont try to justify it to yourself, just try and justify it to SHMBO! of course ALL my motors cost £4.99 so thats alright!!!! Quote Link to comment Share on other sites More sharing options...
PatMc Posted May 25, 2015 Share Posted May 25, 2015 Posted by Dave Hopkin on 24/05/2015 23:53:31: But define quality? I recall a corporate "re-education" program... which asked the question which is better quality a plastic carrier bag or a Guchi handbag? The answer - depends on your use for the bag, if its to carry shopping from Tesco's then the Guchi bag is a miserable failure as it doesn't meet the requirements! My definition od "quality" is "fit for purpose". I never take a Gucchi handbag when I shop at Sainsbury's. Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted May 25, 2015 Share Posted May 25, 2015 Er,...I have a vision of Pat with a Gucchi handbag now Like most folks I guess I've used both cheap and expensive motors. In the end I've come to the conclusion that its all about probability! If you buy a top end motor then there is a high probability that it will perform well, above spec, and last a long time. There is a very small probability that it will be a dog. If you buy a cheap motor there is a reasonable probability that it will perform at least as per spec and a small probability that it will actually perform really well - if in your particular example all the tolerance just happen to conspire to produce a gem. So, I think it comes down to choice. Buy something like an AXI or an OS electric motor and you will almost certainly be delighted with the performance and quality. Buy a cheap motor and you'll probably be quite happy - you might even be pleasantly surprised, but equally you might be very dissapointed. So when you spend more money I feel you are buying a higher probability of sucess - that's all. BEB Quote Link to comment Share on other sites More sharing options...
Geoff S Posted May 25, 2015 Author Share Posted May 25, 2015 Posted by Dave Hopkin on 25/05/2015 11:22:57 Dont try to justify it to yourself, just try and justify it to SHMBO! of course ALL my motors cost £4.99 so thats alright!!!! Fortunately I have a very tolerant wife who has her own hobbies and there are others we share (not aeromodelling) so I'm not required to justify the cost even though she's the company treasurer (and CEO if I'm honest!) Geoff Quote Link to comment Share on other sites More sharing options...
A.A. Barry Posted May 25, 2015 Share Posted May 25, 2015 A friend of mine, after he destroyed a couple of motors, advocates stripping down all new motors, cheap of expensive before use, and "running" thin super glue in between magnets, since he has done this, he has not lost a motor........lucky maybe..... or perhaps a good idea Barry Edited By A.A. Barry on 25/05/2015 13:17:09 Quote Link to comment Share on other sites More sharing options...
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