Simon Chaddock Posted March 5, 2020 Share Posted March 5, 2020 The sudden stop at 58 amps is almost certainly the ESC over heating and cutting out. Don't keep doing it or the ESC will give up completely. If the fan still runs smoothly at low power then the ESC may still be ok. 58 A at less than full power means something is very wrong. The blades may turn freely but to me it sounds like when under load the motor armature is moving forward and rubbing on something. It could be an internal motor short in which case it must be replaced. You are sure it is a 3 s battery you are using. I fear the EDF has got to come out for investigation, bench testing or maybe just straight replacement. Quote Link to comment Share on other sites More sharing options...
Steven S Posted March 6, 2020 Share Posted March 6, 2020 When I tested my fan I got 559 grams thrust at 33.85 Amps for 351 Watts of power. The basic FMS 50mm fan from Banggood. Quote Link to comment Share on other sites More sharing options...
Geoff Gardiner Posted March 6, 2020 Share Posted March 6, 2020 A bit of good news, or should I say, less bad news. Leaving the fan unit in situ, I have wired in another ESC and am getting full throttle (32amps 350watts). So.... a bad ESC. Just need to dig it out and replace it. Tricky, now the side inlets are glue on, but better than having to remove the fan unit. Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted March 6, 2020 Share Posted March 6, 2020 Geoff, Sounding much better but if that is max amps it sounds a little low compared to my results and you will be needing the maximum thrust you can get if other folks JP’s are anything to go by. Tim Quote Link to comment Share on other sites More sharing options...
Geoff Gardiner Posted March 6, 2020 Share Posted March 6, 2020 Hi Tim. That reading was with a part used battery so probably a bit down on power. Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted March 6, 2020 Share Posted March 6, 2020 Geoff, In that case sounds like your fan survived and you will be good to go with a new ESC. Wrong thread I know but have you flown your oodalally yet. (Just completed the fuselage on mine ) Tim Quote Link to comment Share on other sites More sharing options...
Steve Jones 2 Posted March 6, 2020 Share Posted March 6, 2020 Great News then Geoff, esc would have been my first investigation.. Yes also my Provost is a bit sluggish away from the hand launch but once upto speed fine... the Gnat of the other hand goes away like a scalded cat and is too fast at full power. so check the power once your sorted and get a good launcher.. others have suggested make the cheat hole a little bigger to help inital get away Good luck Steve Quote Link to comment Share on other sites More sharing options...
Piers Bowlan Posted March 6, 2020 Share Posted March 6, 2020 Before you chuck the old ESC, could the ESC timing have been wrongly set (at the factory) causing the high amp draw and low power? Just a thought as an appropriate programming card might tell you how the ESC was set up? Edited By Piers Bowlan on 06/03/2020 14:22:45 Quote Link to comment Share on other sites More sharing options...
Geoff Gardiner Posted March 6, 2020 Share Posted March 6, 2020 I did have to extend the ESC to motor wires slightly - I wonder if that has caused an issue. Has anyone else had to do that? Tim, the one decent day I've had this year I took the Oodalally out for it's maiden. Annoyingly on the first attempt I hit a rabbit hole and the undercarriage parted company. Weather has been rubbish ever since. Note. I didn't use the wire version as per the plan - I used the alloy one from my Wot4 Fomie. I have beefed up the ply mount a bit now. Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted March 6, 2020 Share Posted March 6, 2020 Extending the motor wires will not cause a problem as long as they are the correct gauge, I have done this a few times. Do not lengthen the battery leads. Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted March 6, 2020 Share Posted March 6, 2020 Geoff, wire extensions from the ESC to the motor should be ok. It’s from battery to ESc where you need to take care. I have large extensions from the two ESC’s on my twin and have had no problems. Shame about the 🐇 hole. My u/c will be my first attempt at a homemade carbon fibre set. Secured through 1/8 lite ply into a 1/4 ply plate underneath. I even kept Peters ply side reinforcement pieces to spread any load . 🤞 Tim See Martin beat me to it ! Edited By Tim Ballinger on 06/03/2020 15:28:50 Quote Link to comment Share on other sites More sharing options...
Dickw Posted March 7, 2020 Share Posted March 7, 2020 I always loved the look of the Gnat so just had to get one of these. I got the full kit from TN and everything went together really well - most impressed with the quality of it all. Unfortunately other matters kept intruding so progress has been slow, but nearly there now - just the decals to add. In a fit of madness I decide to "paint" rather than "film" so that added a few weeks of work that I really could have done without, but I am quite pleased with the result and the two 1/12 scale guys from "Real Model Pilots just finish the look. Tissue covering followed by primers and topcoats have added 56gms to the bare wood, so probably similar to film. Colour scheme is based on XR538 from the Gnat display team. All up weight with 4s 2200 Lipo, twin elevator servos, and telemetry sensors is 677gm - a little under 24oz. Thrust with the 4s FMS fan (measured by nose down on the scales!) is 680gm at 560 watts (about 38 amps) so with near 1:1 thrust weight ratio I might even have a decent vertical performance. Flying will have to wait for decent weather though!!!!! Dick Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted March 7, 2020 Share Posted March 7, 2020 Nice looking model. Good idea using twin elevator servos and I have already decided on that if I build another in the range because trying to get a smooth operation with a `Y` either with or without tubes is well nigh impossible. I ended up with a 2.5kg servo on my Gnat. I think that tissue/paint will not have added any weight. Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted March 7, 2020 Share Posted March 7, 2020 Dick, Very smart and you have done well on the weight. It’s going to go like a rocket 🚀. Tim Quote Link to comment Share on other sites More sharing options...
Dickw Posted March 7, 2020 Share Posted March 7, 2020 Thanks guys - and I like rockets What sort of control throws are you ending up with after the initial flights - might save me some scary moments! Dick Quote Link to comment Share on other sites More sharing options...
Geoff Gardiner Posted March 7, 2020 Share Posted March 7, 2020 Dick, That looks good. I prefer a paint finish (I usually glass and epoxy) but went with a film finish for fear of adding too much weight. I had not considered tissue and paint, having not used tissue before. It's interesting to know that this method gives a light finish. I may well try it on my next mini jet build. Geoff... Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted March 8, 2020 Share Posted March 8, 2020 Dick, I set up med rate with the deflections Tony suggested in his build notes and a bit less and a bit more either side. I have 10 % expo on all settings. I felt no need to change from the med rate settings on my first 2 flights and had no dramas and twinkle rolls certainly seemed to twinkle. if you do not have the article I can dig it out but can not remember the actual numbers other than they are very small ! Tim Quote Link to comment Share on other sites More sharing options...
Toni Reynaud Posted March 8, 2020 Share Posted March 8, 2020 Finally got the Jet Provost to the patch on a sunny and not very windy day. Got a club member to launch - it sank a bit, wobbled a bit, gathered speed, and away it went. A good flight, if a bit twitchy - it turned out I put a 4S2100 instead of a 4s2500, so the balance point was a bit rearward - manageable but not the best. It went quite well on half throttle, but kept climbing. When it slowed down, control response was not good.On the approach I got within spitting distance of the patch and cut the throttle and it glided in very nicely. A good maiden, and my first EDF, and I'm sure that when I next fly it with more nose weight, it's going to be good. Weight with big battery 720 gm, 25 oz full chat - 13.5V, 30A, 380W, 540 gm thrust. Quote Link to comment Share on other sites More sharing options...
Dickw Posted March 8, 2020 Share Posted March 8, 2020 Posted by Tim Ballinger on 08/03/2020 08:34:32: Dick, I set up med rate with the deflections Tony suggested in his build notes and a bit less and a bit more either side. I have 10 % expo on all settings. I felt no need to change from the med rate settings on my first 2 flights and had no dramas and twinkle rolls certainly seemed to twinkle. if you do not have the article I can dig it out but can not remember the actual numbers other than they are very small ! Tim Thanks Tim - I suspected Tony's guidance would be spot on, but it is always good to get confirmation. Incidently, in an earlier post you were trying to work out the number of magnetic poles in the motor. I think it is a 6 pole motor so set my telemetry up that way and recorded 51,500 rpm at full throttle (static) which is about 75% of kV x volts at that time - so that looks about right to me. Looking forward to seeing the in-flight data. Dick Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted March 8, 2020 Share Posted March 8, 2020 Dick, You are absolutely correct I got my pole pairs confused with poles. I guess i managed to count 6 magnets and never divided by 2 before entering the data. Should have done the kv check sum like yourself. So all my rpm numbers needed multiplying by 2 which i think would give me a peak of 49,000 rpm. Tim Quote Link to comment Share on other sites More sharing options...
Raymond Richards Posted March 17, 2020 Share Posted March 17, 2020 Here is my little Provost, still to fly , but fun to build......the scheme is made up ...not one for the purists Quote Link to comment Share on other sites More sharing options...
Tim Ballinger Posted March 17, 2020 Share Posted March 17, 2020 Made up or not it looks really smart . Tim Quote Link to comment Share on other sites More sharing options...
Raymond Richards Posted March 17, 2020 Share Posted March 17, 2020 Thankyou Tim, a nice aeroplane the Provost, but close ups can get rough . Flying field is shut till April 6th in the Netherlands and working from home, so much building , zero flying Ray Quote Link to comment Share on other sites More sharing options...
Geoff Gardiner Posted March 17, 2020 Share Posted March 17, 2020 Looks good Ray. Out of interest, how much does it weigh - flight ready? Geoff... Quote Link to comment Share on other sites More sharing options...
Raymond Richards Posted March 17, 2020 Share Posted March 17, 2020 Hi Geoff, and thanks .......including a 2200 4s Lipo she is 24.9 oz RTF. No nose weight, only a nose light Ray Quote Link to comment Share on other sites More sharing options...
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