Simon Chaddock Posted January 24, 2014 Author Share Posted January 24, 2014 A double whammy with my Concorde The left hand inner ESC failed. A MOSFET jad blown. It was running on short battery leads and each fan only takes 12A maximum so it should have been well within its 20A rated capacity. The only thing I can think of was this was the ESC I was using when I 'cooked' one the fans running on a 3S with may have over loaded it. Nevertheless it is a concern so I thought whilst I had the left hand ESCs exposed I would est the other LH fan and ESC to check nothing got too hot after say 60 full power running. It did not prove possible as the fan disintegrated as it was being run up to full speed. These EDFs are an all glued assembly cannot be repaired. A new fan and ESC are ordered. New fan and ESC have been ordered but I am reluctant to take the airframe construction any further until the all the EDF have been fully tested as everything but the battery will be fully built in once the fuselage is complete.. Quote Link to comment Share on other sites More sharing options...
Martian Posted January 24, 2014 Share Posted January 24, 2014 what a blow Simon or not as is the case sad to see, those mosfet device only have to experience one spike and they invariably will fail . I understand from my past exp as a technician the spike blows a microscopic hole in the device Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted January 26, 2014 Author Share Posted January 26, 2014 Having cooked one EDF trying to run it on a 3s another has thrown its blades and an ESC has blown it means I have now bought 6 of each, enough to power an XB70 Valkyrie! As I am still waiting for the last EDF to be delivered I had a quick look at a Valkyrie 3 view. Bigger and much heavier than Concorde it first flew 5 years earlier and eventually cruised at Mach 3! With those engines all grouped together I did wonder if it would be possible to 'bury' a single oversized EDF and still retain a scale sized inlet and exhausts. Quote Link to comment Share on other sites More sharing options...
riverlandgirl. Posted January 26, 2014 Share Posted January 26, 2014 Quite a machine. One EDF would certainly simplify things! (by the time the concorde's flying, you'll have everything sorted any way) Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted January 26, 2014 Share Posted January 26, 2014 Blimey Simon, so you're already dreaming up the next one! In high speed flight, the Valkyrie outer wing panels were turned down into a steep anhedral, (30/45 degrees)? Would you try and build that feature in, or is it going too far? It would be complicated. I know this plane has been modelled successfully before, although I don't know if anyone has done the wing feature just mentioned. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted January 26, 2014 Author Share Posted January 26, 2014 The tips actually went down to 65 degrees in supersonic flight and until the advent of the big swing wing bombers it held the record for the largest moveable surface. Folding the tips down apart from controlling the shock wave lift also moved the centre of pressure forward quite a bit so countered the need to move fuel about as they did in Concorde. It also added to the vertical area so allowed the fins to be smaller than they would have had to have been for good supersonic lateral stability. Apart from the novelty there would be no advantage at slow speed and they would be quite an hazard for a belly lander! Apparently the XB70 suffered from bad adverse aileron yaw at slow speed such that applying aileron to lift a low wing could have the opposite effect. The second XB70 had 5 degrees dihedral added to improve the roll stability but it made the adverse yaw worse. One of the pilots when asked how it flew replied 'busy' which I think means 'quite a handful' in test pilot speak! I did go as far as to outline the biggest single fan that could be installed inside the scale outline. But its just doodling really. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted January 26, 2014 Share Posted January 26, 2014 Thanks for filling in the detail Simon, my memories were a bit vague. The single bigger fan could be the way to go and actually, this might be a more straightforward project than the Concorde? You could of course make a F104 to fly in formation with it, although a degree of caution would need to be exercised, if I remember that bit correctly! Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted January 27, 2014 Author Share Posted January 27, 2014 It would appear that in America the XB70 has a following almost like TSR2 does here in the UK and for not dissimilar reasons. Technically hugely advanced, eye wateringly expensive and designed to meet a specific objective which did not fully take into account a rapidly changing environment. Originally a fleet of 60, and 3 prototypes, then cancelled, then 12 reinstated in a slightly different role, cancelled again and finally reinstated as 2 high speed research vehicles with the 3rd prototype scrapped part complete. A single fan version would indeed be simpler than Concorde and would concentrate all the electrics in the centre but dividing the airflow into 6 individual nozzles, although impressive, would be rather inefficient. Quote Link to comment Share on other sites More sharing options...
Martian Posted January 27, 2014 Share Posted January 27, 2014 the loss of one of the prototype was sad and the way in which it was lost was weird..Simon you could experiment with the multi nozzle setup by building a thrust module before committing to the full model that way you could ascertain it's efficiency just a thought (it happens sometimes ) Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted January 28, 2014 Author Share Posted January 28, 2014 Martian A six nozzle test duct? Funny you should mention that......................... Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 2, 2014 Author Share Posted February 2, 2014 At last the new ESC and fan are installed. The new ESC has an additional small heat sink over two chips. These do seem to get quite warm so the remaining ESCs will be modified in the same way. These heat sinks will be exposed through the wing upper surface. Thel extra heat sinks installed. The radio is the next item. Once this is in the battery can be approximately positioned to achieve the 'guestimated' 50% chord CofG. Quote Link to comment Share on other sites More sharing options...
Martian Posted February 2, 2014 Share Posted February 2, 2014 nice and neat Simon ,have you run the fans up to max yet . I sincerely hope they are successful this time and you get to fly her,should have great presence in the air Quote Link to comment Share on other sites More sharing options...
Bernie Posted February 2, 2014 Share Posted February 2, 2014 you guys amaze me what you can do with some depron and you make everything look so easy ,I have followed you'r build to date and I must admit I'm sat here with a mug of tea and a plate full of sausage rolls transfixed .I will be following the rest of you'r build with intense interest.best regards Bernie Quote Link to comment Share on other sites More sharing options...
SR 71 Posted February 3, 2014 Share Posted February 3, 2014 They are good arnt they Bernie, been following Simons builds for a long while now, I think he is brilliant the way he builds the things from his head Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 5, 2014 Author Share Posted February 5, 2014 Thanks for the comments Every thing is on hold at the moment as I am waiting for the radio. I thought I would try one of the neat Orange combined Rx and gyros. Ordered from Hobby King but it did not work at all! HK accepted the return for replacement but now out of stock and on back order! The CofG is quite critical and everything has to be placed along way forward to counter the aft fans and ESCs so I really need it all to be connected up to find out exactly what needs to go where. My next thought is to reduce the amount of wiring by combining the all the reds and blacks for the ESCs and servos and only leading the individual signal wires with just one pos/neg forward to power the radio. It would use just six cores instead of twelve as at present. Worth all the trouble? Not sure but I want to test it with the radio first! In the mean time I have built a 'test' duct (out of Depron of course) for a XB70 Valkyrie! Not that I intend to build one (yet!) but it will be interesting to see how much thrust is lost. Just waiting for the slow boat (747?) from China to deliver the fan! Quote Link to comment Share on other sites More sharing options...
Keith Simmons Posted February 5, 2014 Share Posted February 5, 2014 Maybe a silly question ! How do you work out the CoG? Do you build a test model and test fly it to find the sweet spot by experiment? If you did the calculations, how does it compare? Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 5, 2014 Author Share Posted February 5, 2014 Keith I did build a half size simple chuck glider for my Depron Skyray but that had a plain delta wing so I guessed a simple plank version would be close enough and it was. My Concorde on the other hand has a scale wing with lots of twists and curves so I suspect a flat plank might not be good enough. The full size had CofG limits of 51.8% to 54% root chord for take off. Models tend to be set up a bit nose heavy so I am aiming for 50%. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 18, 2014 Author Share Posted February 18, 2014 You may have noticed a paucity (nice word!) of posts. This is because I have not made any progress to report. The reason is I have had another EDF failure! This time its the bearings. The RH outer outrunner bell has so much play that the fan blades can touch the casing. It has not been run for more than about 2 minutes! So yet another 40mm (the seventh!) is on order. The really niggling bit is I now have one EDF with a good motor and broken fan blades and another with a broken motor but a good fan. The problem is these tiny AEO units are glued together and cannot be taken apart! I don't want to continue with the remainer of the fuselage skinning until I have had an opportunity to test the motors/ESCs thoroughly so everything is on hold until the new fan arrives. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 22, 2014 Author Share Posted February 22, 2014 On removing the EDF I discovered that it had not suffered a bearing failure in the conventional sense but simply the front bearing was no longer in its housing! The layout of the motor is such that the rotor is only restrained correctly for forward thrust. No problem for an EDF. The only thing that prevents rearward movement is the back face of the fan against the front of the motor. In this case the fan had been glued on about 3mm short which allowed the front bearing to simply work out of its housing. If I can satisfactorily glue the fan back on the motor shaft I will put this EDF back on again. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 24, 2014 Author Share Posted February 24, 2014 With it all back together (the fan glued back ok) and the wiring simplified I fear I have run into what could be a serious problem. With all four fans running it gets to about half power, drawing some 17A in total, and then one motor (it may be more and it is difficult to tell which) starts to slow down but the others continue up to full power. Disconnecting either the the right or left hand pair and running them up alone achieves full revs & power drawing 21A which is about the expected current. It appears to be a function of having all four motors connected yet the fault starts to appear at quite a low current. It is almost as if there is some input interference which is causing one (or more) of the ESCs to 'loose it'. Is this a manifestation of the long and branched ESC to battery wires causing some sort of harmonic pulses that are interfering with the timing of the ESCs? I fear the only practical solution is to completely reorganise the electric layout to greatly reduce the ESC to battery wire length but to do so will require considerable 'butchery' to the wings which at the moment have beautifully smooth with one piece Depron skins. I shall have to think about whether it is worth the effort given that using 4 tiny EDFs in this way had no guarantee of success in the first place. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 12, 2014 Author Share Posted March 12, 2014 So reorganise the wiring it is. First the ESCs have to be removed and the duct wall made good. Now I have to find a way to run the six motor wires forward through the wing to the ESCs that will be mounted at the front of the duct. A process made more complex by the fact any cut outs in the wing surface must be kept as small as possible as there is no internal reinforcement. All the loads are carried by the wing skin itself. Quote Link to comment Share on other sites More sharing options...
Keith Simmons Posted March 12, 2014 Share Posted March 12, 2014 Hi Simon. Sorry to hear your problems in the electrical set up. I expect you had run two motors together in the test nacelle, but not all 4 in two test nacelles to test loading, wire lengths in a full set up.? i do hope you can solve and work out all the problems and not lose (destroy) any more fans. i must try this method myself to confirm it is workable in a model and CoG wise in the future. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 12, 2014 Author Share Posted March 12, 2014 Keith Indeed on full scale prototypes it certainly is/was normal practice to build an operational 'systems rig' with all the components in their correct positions to detect any problems. To be fair at the time I was (and still am!) very concerned at the thrust level (or rather the lack of it) so I went for a minimum weight/maximum efficiency set up rather than best practise. Oh well! Hindsight is a wonderful thing. Quote Link to comment Share on other sites More sharing options...
Keith Simmons Posted March 12, 2014 Share Posted March 12, 2014 Lol simon, there are many things where Hindsight can be useful. Many a Doh moment !!! Best of luck and hope you can beat the challenge. I think depron is the way to go for EDF and balsa/ply for prop powered aircraft. regards. Keith Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 13, 2014 Author Share Posted March 13, 2014 The RH ESCs moved forward. The heat sinks are flush with the underside in the mouth of the duct. They are just dry positioned at the moment. The next step is to connect them up with the appropriate wires but all externally to make sure it still works. If it does then a method will have to be found to feed the wires actually through the wing. If it still works then ESC to battery wires can be fed forward through the wing at an angle towards the battery and tested again.. Then there will be the other side to do!. This is going to take some time. Keith Whilst I agree balsa/ply/GRP is probably the only practical way to handle the vibration of IC planes Depron works well with electric prop too particularly scale types where weight can be an issue. Edited By Simon Chaddock on 13/03/2014 11:20:07 Quote Link to comment Share on other sites More sharing options...
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