Jon Posted September 15, 2008 Author Share Posted September 15, 2008 Hi Bruce...I have not made any changes at all, its as supplied as a combo deal from BRC... it has been working well for a few months before this started to show. It had had a few nose up landings when I landed on the strip but then ran out of cut grass and stopped in the long grass. Snapped the prop a few times. The problem showed its self a few times prior to a vertical nose down landing which caused a fair size repair job. It was then that it really started to play up so I purchased the new motor only to find the same problem but not quite as bad as the old motor.... PS...I'm not sure what you mean by the term "pusher"... jon Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted September 15, 2008 Share Posted September 15, 2008 Yes incorrect timing would show up as you describe - however the fact that it worked fine before is puzzling. The crash seems key here - perhaps you dislodged a magnet which occasionally grinds on the rotor as it spins?"Pusher" means drug dealer....oh no sorry, wrong forum Pusher is where the motor / prop is at the back of the airframe as in many flying wings. When the prop and motor is at the front as "normal" then it is termed "tractor". Quote Link to comment Share on other sites More sharing options...
Jon Posted September 15, 2008 Author Share Posted September 15, 2008 Yes its a "Tractor" then... Have just been on the landline to BRC... they say that without a doubt its a timing thing.. Needs to be set to "Hard or High" they said... follow the instructions the man said ...what instructions said I ... I'll email you some said he..... Still waiting for the instructions to arrive!So if he & Steve (see above) are really cleaver clogs then what do you think changed the settings ?As it all worked well before and it was not a sudden change, more like a gradual worsening on the first motor ... I now know why they call it electricery! Some learning curve this flying lark is Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted September 15, 2008 Share Posted September 15, 2008 yep...very steep Jon, very steep. Quote Link to comment Share on other sites More sharing options...
Former Member Posted September 15, 2008 Share Posted September 15, 2008 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted September 16, 2008 Share Posted September 16, 2008 Hi Jon.....yes incorrect timing & subsequent "screeching" can indeed stop the motor......pretty much stop it dead in fact.....this hapened to me with the motor mentioned above & it was very embarrasing to have to shout "dead stick" with an electric model.........especially as I'd just been telling everyone in the pits how reliable they are...!!!!!As I understand it, what happens is that the forces pulling the rotor (& hence the prop) around get out of synchronisation & rather than pulling the rotor around simply stop it dead......No idea what could have changed the settings.....ESCs are a bit like women & computers....they can change their mind for no reason at all & forget to tell you... Quote Link to comment Share on other sites More sharing options...
Jon Posted September 16, 2008 Author Share Posted September 16, 2008 I have had a second chat with Scott at BRC (very helpful chap he is too) and he made me aware of a "card" as he called it that I could purchase for £5 or £6. It allows the checking and setting of these ESCs & Motors and if I have got it right simply plugs into the ESC via the RX cable/plug... So I am waiting for the post at the moment..... Think he's sending the instruction sheet for this combo with it too...I find this all very strange as I have done quite a bit of reading up on this electricery business but cant remember reading about this sort of problem or even the mention of Hard or Soft settings... but I surlly I must have?, but I cant remember it. oh and before anybody comments ,yes, it could be the start of me getting old! and forgetting Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted September 16, 2008 Share Posted September 16, 2008 Not all ESCs have this feature & it is fairly obscure to the average club pilot (me included) who just wants to plug & play. It is possible to play around with e-Flight for ages & never come across motor timing.....It may not be the cause of your problem but it seems likely to me......Scott visits this forum quite often I believe....I don't know him but I hear hes a good guy.....even if he is Cumbrian!!!!!! Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted September 16, 2008 Share Posted September 16, 2008 Yes Scotty is a good guy - and does indeed frequent our merry throng from time to time for a good argument The programming card is great, I have a couple here for various ESCs ( they are not universal I am afraid ) and it does simplify the job of the settings tremendously.PS did you confirm that you havent got a loose magnet / knackered bearing?? Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted September 16, 2008 Share Posted September 16, 2008 Easier than waggling the Tx stick & listening for a new beep or two anyway .....!!!! Quote Link to comment Share on other sites More sharing options...
Jon Posted September 16, 2008 Author Share Posted September 16, 2008 Bearings seam ok on both motors but on the first motor the little grub screw which fits into the cut out slot on the main shaft had come loose a little allowing the main shaft and the outer case to move forward by about 1mm! Think the only thing then holding it was the E clip on the back end! this came off when I touched it... which was the start of this thread. The first motor had one loose magnet (came loose during the vertical nose down landing) which I glued back into place allowing a very small amount of glue to also spread and dry around all the others. My thinking for this action was "I did not want to upset the motor balance" so all magnets got a little extra glue to spread the load and also to make sure they were firm fixed. This action worked well but I still had the screeching.jon Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted September 16, 2008 Share Posted September 16, 2008 I still cant help thinking that the crash was the cause - why else wpould it suddenly start mis-behaving, especially if you have not re-set the ESC settings from those of the original runs. Quote Link to comment Share on other sites More sharing options...
Jon Posted September 16, 2008 Author Share Posted September 16, 2008 Hi TimboWe did have the screeching prior to the crash ( during the couple of months before the crash) but not as much.. I must admit.... I think that both the new motor and the old are ok ..its just the ESC settings which have changed and the crash was the final straw.... Anyway once I get it reset with the card according to the great GODS of electricery it'll just go away!My hands are clasped tight... jon Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted September 16, 2008 Share Posted September 16, 2008 Sending large wads of used notes to the High Priests of All Things Electric (ie me & Timbo ) can often work wonders too.....!! Failing that, sacrificing an ESC by the light of a full moon every other February the 29th can help.....Or you could try.....(contd page 94....)Let us know how you get on Jon........ Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted September 16, 2008 Share Posted September 16, 2008 PS...if you had the screeching before the crash & still have it now then what has changed? Not a lot as far as I can see.......Maybe the ESC left the factory in "screech" mode (ie with the wrong timing) & has always been set that way..... Quote Link to comment Share on other sites More sharing options...
Jon Posted September 16, 2008 Author Share Posted September 16, 2008 Hi Steve Well it is a trainer and it did get a few knocks from time to time abeit at worst a broken prop apart from the final nose dive... Your comment about "when it left the factory " has made me think (no Eric not for the first time) , you may well be right as now I think back it did make some worring sounds from time to time in its early day's.... I think I even metioned it on this forum when I was building/testing the plane It was sold to me as a Combo deal so being a newbie I assumed that Combo meant "combination" which in turn lead me to think it was a matched/tunned pair This learning curve may have just become a vertical climb!Think you may have hit the nail on the hammer Steve...jon Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted September 17, 2008 Share Posted September 17, 2008 Well.....even if the ESC did leave the factory with the "wrong" timing that is not a fault per se.....it's a bit like buying a Radio & finding it is already tuned to Radio 3.......nothing wrong with the radio but its not set up the way you want so you have to change it. Granted this can be difficult if you haven't got any instructions & frankly most of the ESC instructions are a bit rubbish to say the least.....full throttle...half throttle..was that 5 beeps or only 4.....& written in Chinglish just to make it even more difficult.......need I go on!!! The programming card you have ordered will make everything so much easier..... Mind you we might be getting ahead of ourselves here...we don't yet know the timing is actually "wrong". By the way do you have any relevant numbers you can share.....maximum allowable current for the motor & actual current drawn would be useful/interesting........For me part of the fun of this hobby is that you never stop learning.....for instance I recently learned that you can't bring a new & expensive model home & not spend a few nights on the sofa if you haven't cleared it with your wife first......now who would have expected that ?????In your case you have now learned about motor timing & the next time you hear a screeching motor in the pits you can walk over confidently & say "Yer timings wrong mate..." & revel in the looks of admiration & awe from your clubmates Quote Link to comment Share on other sites More sharing options...
Jon Posted September 17, 2008 Author Share Posted September 17, 2008 Wow...Thank you, I can now become a big head on the subject and really look good like all the others in my flying shades.. I don’t think so some how... little more of that dam learning curve to go yet me thinks..With a bit of luck the card should arrive in the post today...then with the permission of her indoors I may be granted time to try it out... then we should know ...fingers cross ...All I can tell you about the motor details are on this BRC page... I have been using a 12 x 6 prop and 2 parallel 2500 mA 18C to 28C 45Amp to 70Amp Lipos ....I now also have a pair of 20Cs that I can swap during my lessons....jon Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted September 17, 2008 Share Posted September 17, 2008 Not so much a "Big Head" as sharing your knowledge......we are ALL standing on the shoulders of Giants after all...... The motor Combo looks good.....plenty of headroom on the ESC & battery.....on a 12x6 I would guess you're pretty close to the 35A max of the motor.....what does the BRC motor/prop/battery sheet say about the current on a 3s set up with that prop? Do you have access to a Wattmeter? if so use it..if not beg, borrow or steal one....as a last resort buy one as they are only cheap -ish these days here & here. I cannot stress how important a Wattmeter is in e-flight. Sooner or later (probably sooner) you will burn out a motor or an ESC or puff up a battery because you've overloaded it. Using a wattmeter will prevent this & thus save you money in the long run...... Quote Link to comment Share on other sites More sharing options...
Jon Posted September 17, 2008 Author Share Posted September 17, 2008 Hi you were a bit quick for me...see above its been added.Yes I have a watt meter....jon Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted September 17, 2008 Share Posted September 17, 2008 Yep.....see above...I edited mine too!!!!!Plug the wattmeter in & see what it sez......... Quote Link to comment Share on other sites More sharing options...
Jon Posted September 17, 2008 Author Share Posted September 17, 2008 I forgot to tell you the Lipos are 4s... The whole set up was BRCs ideas , prop, motor, ESC, and lipos....Will run it up on the watt meter once more and repport the numbers to you.... cant do that at the moment as her indoors has other plans for me.... I'll be back Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted September 17, 2008 Share Posted September 17, 2008 Interesting......you definitely need to check the current IMO.........I wouldn't presume to second guess the BRC guys as they are much more expert than me, however I have a similar motor but with a slightly higher kv of 1100. This pulls 38A on 3s on a 11x7 prop......you have a 12x6 prop & a 4s battery......methinks you will be well over 40A with this set-up & given the motor is rated at 35A continuous I fear you maybe entering "magic smoke" territory......& you are definitely at the top end of the motors' capability which may explain the screeching even if the timing is correct. If you are pushing the motor harder than it wants to go it will screech as the phases get out of sync....ether that or it wil melt!!!!As I say though BRC are much more knowledgable than me.........The watt meter is your friend in this situation..... Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted September 17, 2008 Share Posted September 17, 2008 The difference will likely be that your motor is only 919Kv whereas Steve's is 1100. I have found that when you get up to quite big motors like these ( 500watts +) a hundred Kv here or there actually makes a large difference to current draw. The prop itself alaso affects things quite bit more than people realise - one make versus another ( even the same size ) can often show a few amps difference. I also await the results with some interest Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted September 17, 2008 Share Posted September 17, 2008 Yes indeed...I've just been looking at a few other motors around the 900kv mark & 12x6/12x5 seems to be about correct...pulling about 40A on a 4s........if we assume about 13volts under load, maybe a bit less then 500watts equates to just over 38A....still over your motors max current but comfortable as long as you don't use full throttle all the time...... Quote Link to comment Share on other sites More sharing options...
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