Simon Chaddock Posted February 23, 2021 Author Share Posted February 23, 2021 Martin I did wonder about a ferrite ring but I simply couldn't find one for the test. Dad_flyer I suspect twisted servo wire might be the answer after all why is it used? The test was using a servo tester running from a 5V BEC with an 1800 mAh 2a LiPo but I suppose it could be a signal voltage issue with the servo tester itself. The longest servo wire I have on a plane is about 1.2 m and that does not show this effect. Twisted servo wire is on order. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 23, 2021 Share Posted February 23, 2021 (edited) I was thinking more along the lines of signal voltages being induced between the two long leads (especially if run closely together over a considerable distance) and being fed back into the receiver. Beat me to it Simon! Edited February 23, 2021 by Martin Harris - Moderator Crossed postings Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 27, 2021 Author Share Posted February 27, 2021 I have replaced the long lead with twisted servo wire. There some reduction in the servo 'hesitation' but it is still there compared to a short lead however it is at a level I can live with - I think! I suspect it will require some more experimentation to try to establish whether the problem is at the servo or the receive/servo tester end (it does the same with either). I do wonder if the very small size of the 3.7 g micro servo has made it more sensitive to interference as the effect was less noticeable with a basic 9 g one. This may have been a problem all along but a 'crazy' person would use such a 3.7g servo on a size of plane that needed a 1.5 m length of wire! Unfortunately the Lemon stab receiver I ordered appears to be 'lost' in transit. The package has China Post 'track and trace' but for the last 6 weeks has been showing "Delivered to carrier" but no sign it has arrived in the UK. To save weight everything but the battery will be 'built in' so I need the receiver to establish the correct lengths of the servo wires. In the mean time the above wing fairing has been built up to met the nacelle under side. The intention is once the nacelle is glued in place the wing will be removed out side ways. I have to hope the gap left behind is big enough for the down turned wing tip to get through. ? 1 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 2, 2021 Author Share Posted March 2, 2021 As the engine nacelle will eventually be glued permanently in place it required a change to be made to the rear centre wing bolt as it would not be possible to get at it! Structurally the centre bolt gave the simplest and lighted fixing so I was reluctant to use two rear bolts as I did at the front. After much thought I chose to angle the single rear bolt degrees so it missed the nacelle but it would require a long screw driver.? The bolt is enclosed by a simple paper tube which also 'guides' the screw driver. Canting the bolt over at such an angle is not ideal for strength but it is only taking about 1/6 of the load of each of the front ones. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 12, 2021 Author Share Posted March 12, 2021 (edited) With the motor nacelle glued in place the next job is to run the motor wires forward and mount the 20A OPTO ESC at the top of the fuselage just ahead of the cockpit. To run the wires required a couple of assess holes to be cut into the fuselage. Being an all stressed skin structure the section of skin cut out can be simply glued back in place. An unusual picture taken through what will be the battery hatch showing the elevator, aileron and ESC plugs which have been run forward. The Lemon Stab receiver will be mounted low down on the floor of the fuselage. The battery box is next. Edited March 12, 2021 by Simon Chaddock Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 16, 2021 Author Share Posted March 16, 2021 Ran into a serious problem - servo hesitation. This video demonstrates it. https://www.youtube.com/watch?v=WiBbuDZHRSw It effects all four servos although the elevators are worst. Hard to image all four servos are faulty, they were all tested prior to installation, so is it something to do with the long 1300 mm servo wires? or the fact servo pairs are on a Y lead? The switch BEC is rated a 5A and the servos are not under load so draw only about 150 mA each. Obviously there is no point in trying to fly the He162 with the servos behaving like this. I doubt the Lemon stab Rx would do very well either. Have to have a serious think. ? 1 Quote Link to comment Share on other sites More sharing options...
Stephen Jones Posted March 17, 2021 Share Posted March 17, 2021 (edited) Hi, Simon. What gauge are the servo extension wires ? If they are thin could it be signal loss. Have you tried the set-up externally to reproduce the problem, And try doubling up the extension cable or use a thicker gauge wire . or try making your own servo extension cables out of screened cable. Steve Edited March 17, 2021 by Stephen Jones typo Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 17, 2021 Author Share Posted March 17, 2021 Hi Stephen What puzzles me is the HE 162 set up is nothing that I haven't done before. These are the elevators of the even bigger AN124. https://www.youtube.com/watch?v=5KTwjab7r1k Two 5g servos, coupled with a Y and on the end of an even longer 1500 mm long lead. In both cases the Y joint individual cables are soldered and shrink wrapped. As everything on the HE 162 is rather 'built in' and will require some 'surgery' to get at I will follow your advice and set up an identical installation with pair of servos on a similarly long lead to see if that behaves in the same way. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 20, 2021 Author Share Posted March 20, 2021 (edited) Just an update. Two new 3.7g digital servos have cured the hesitation problem. The wiring between the Rx and the servo Y joint is unchanged. https://www.youtube.com/watch?v=W_t-eqlj3uU Required some surgery to extract the old servos and to re solder the Y but so far so good. Edited March 20, 2021 by Simon Chaddock 1 Quote Link to comment Share on other sites More sharing options...
GrumpyGnome Posted March 20, 2021 Share Posted March 20, 2021 Relatively good news. Will be flight ready soon hopefully. GG Quote Link to comment Share on other sites More sharing options...
Stephen Jones Posted March 20, 2021 Share Posted March 20, 2021 Well i guess there's always one bad apple that will let the bunch down. Glad you found the problem. Steve Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 24, 2021 Author Share Posted March 24, 2021 The saga continued. One of the aileron servos did exactly the same 'hesitation' thing so some new digital servo on order. Just out of curiosity I did a test on one of the old elevator servos connecting it to the as delivered length lead, then with a 1000 mm extension and finally with a 1500 mm extension. https://www.youtube.com/watch?v=af3Yg0RMPT8 You have to turn up the volume if you want to hear the hesitation. The bizarre thing is on the 'as supplied lead' its operation is to all intents and purposes perfectly normal and would not be rejected it as faulty. Just to add to the annoyance the aileron servos will be rather harder to extract and replace "invisibly" than the elevator ones. So given the delay I thought I had better start painting it, particularly the fuselage as a light coat of thinned acrylic white not only seals the surface but is seeps into and seals any plank join cracks which makes a surprising improvement in the local stiffness. Important as it is a belly lander. ? It certainly does a reasonable job of hiding the plank joints. When fully dry the hard surface enables a bit of sanding. With weight in mind I will follow this paint scheme as it is about the simplest I have found. This is actually in its 'as delivered' scheme before it acquired the individual Staffel markings. 310003 became 'Yellow 5' although the basic camouflage was unchanged. I think I will wait until I know it flies before giving it is final decoration. 1 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 28, 2021 Author Share Posted March 28, 2021 Took the best part of a day to do but the 'built in' aileron servos have been replaced with digital 3.7g. Each was tested first with a 1000 mm extension to make sure it worked properly. ? One advantage of using printed lattice braced ribs is there is a lot of room in the wing so the servo wire 'runs' are very free runnng making it easy to use a 'pull though' when the servo is cut out and just as easy to pull the wire back through again once the new servo has been solder on. The only mark on the wing under side is the panel cut out to extract the servo. Not quite 'invisible' but not bad. It did means lots of soldered and heat shrink connections in 32 awg servo wire. Not my favourite job! Made some progress painting the fuselage. Getting concerned at the weight of the paint simply because there is rather a lot of surface and it is a very light weight structure. ? This could all end in tears! 2 Quote Link to comment Share on other sites More sharing options...
alan p Posted March 28, 2021 Share Posted March 28, 2021 Hi Simon 12inch span jetex scaled up to 32" with 50mm EDF. waiting for maiden may fly may not? Watching yours with interest. 1 Quote Link to comment Share on other sites More sharing options...
GrumpyGnome Posted March 28, 2021 Share Posted March 28, 2021 Like buses those.......... Quote Link to comment Share on other sites More sharing options...
alan p Posted March 29, 2021 Share Posted March 29, 2021 Hi Simon Don't know what paint you are using but Veljao Model Air has good coverage and pigment for little weight if you have an airbrush. You have already sealed the surface previously. Quote Link to comment Share on other sites More sharing options...
Erfolg Posted March 29, 2021 Share Posted March 29, 2021 I have found that most, if not all, water based paints (for art work) and or inks, applied by spraying, add pretty much undetectable (by ordinary means) weight. Also the covering power tend to be excellent, if the surface has no dark markings. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted April 10, 2021 Author Share Posted April 10, 2021 The basic painting more or less complete. Just a battery hatch. With all the servos replaced by 3.7 digital the servo hesitation was cured. Still not sure why the a long servo lead causes the problem. 0n a reasonably calm day I did fly it using its intended 450 mAh 4s. Just about enough power but it showed the most severe adverse aileron yaw. It banked readily enough but the direction of flight hardly changed until at close to 45 degrees the nose dropped and provided it had height to recover the direction altered about 180 degrees. Not a wise manoeuvre for a plaqne with very marginal power. It was by then flying down wind. It did not fancy landing like that so attempted to execute another stall type turn to get it heading into the wind for a landing, In my desire to get it facing into wind quickly I probably added to much bank and likely encouraged the stall with a bit of up elevator. Bog mistake it simple flipped on it back and pancaked onto the grass in a fully fully stalled state.? Dislodged the nacelle but no other damage. I have a suspicion the CofG was a bit too far back but the severe lack of thrust rather limits what can be done. Some tests suggest the lack of thrust is due to the prop being right at the back of a long duct. On a 4s it is possible to hear the motor note change just before fun power is reached with a just audible 'throb' emanating from the front of the duct. Is part of the prop blade actually stalling? I have some true EDFs that work fine at the back of a long duct but is possible the multiple broad chord fan blade are better able to cope with the lower inlet pressure. Rather than re fix the nacelle I wondered if the motor and prop were moved to the front of the duct it might cure the prop starvation. Moving the motor forward by about 550 mm would certainly make moving the CofG much easier. In addition the motor to ESC wires would be shortened by a similar amount reducing voltage drop and saving quite a few grams at the same time. it would allow the Rx to be positioned right under the wing which would also shorten all the servo leads by nearly the same amount. On the face of it any difficulty in extracting and remounting the motor in the duct seems to offer significant benefit elsewhere. We shall see. ? 2 Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted April 10, 2021 Share Posted April 10, 2021 Sounds like a plan Simon. ? Quote Link to comment Share on other sites More sharing options...
alan p Posted April 11, 2021 Share Posted April 11, 2021 Well done Simon, glad no damage inflicted probably due to your light build. Mine yet to maiden waiting for my 2nd jab first. My edf is positioned at the mouth of the duct, idea being unrestricted airflow with about 85% swept area at exhaust. Good luck with your mods. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted April 23, 2021 Author Share Posted April 23, 2021 (edited) Extracting the motor from the rear of the duct proved easier than I imagined. The rear of the nacelle with the motor was simply cut off and a new nozzle printed that picked the existing inlet duct. The Depron outer skin can than be made good. Of course it has lost the distinctive scale after body but at the moment raising the level of thrust takes precedence. The next task was to print a new inlet bell that incorporated a motor mount. My intention would be to simply cut out the existing bell and sufficient inlet duct that the motor mount could be glues back in without disturbing any of the outer Depron. Much easier to say than do but after several attempts and printing suitable make up pieces a 'front motor'' installation was achieved. It certainly now runs up to the full 4s speed without any problem but with how much, ifr any, more thrust is not yet known. It certainly feels like it is pulling harder.? Now to decide on the 'what and how' of the associated fuselage modifications. Edited April 23, 2021 by Simon Chaddock 1 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted April 27, 2021 Author Share Posted April 27, 2021 (edited) The first task is to make the canopy removable as the likely position of the battery means it will become the battery hatch. A penalty of using printed formers as they are almost impossible to cut cleanly unlike balsa or foam. A big hole! The nose is now very 'floppy' and will rely on the cockpit internal walls to restore rigidity. The solid cockpit 'canopy' is reused but with new printed internal frames. Although the frames are new they are printed using the same coordinates as the original 'one piece' formers so 'touch wood' the canopy should fit exactly in the cut out aperture. It is at about this time you begin to wonder why on earth you chose to build this plane in such an unusual manner and materials. By comparison converting a foamy chuck glider to RC & power seems so much simpler and with a greater chance of success as well!? Edited April 27, 2021 by Simon Chaddock 1 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted April 28, 2021 Author Share Posted April 28, 2021 I do not have any 3 mm Depron so the cockpit is lined out with 5 mm EPS laminate underlay. Softer and more flexible than true Depron but quite adequate for this application. The 20A OPTO ESC and 5A UBEC glued onto the floor of the cockpit look almost 'lost'. A 650 mAh 4s with an XT30 connector slides into the front. The Lemon stab receiver is now mounted virtually at the CofG no because it has to, it is only a 'rate' gyro so does not auto level, but simply to reduce the lengths of the servo wires. The Lemon is set for dual ailerons so the differential facility can be activated of the Tx. Hopefully this will result in the CofG a bit further forward, a bit more thrust and aileron differential to reduce the adverse aileron yaw with a very modest increase in weight going from an 450mAh to 650 mAh battery. Quote Link to comment Share on other sites More sharing options...
Dwain Dibley. Posted April 28, 2021 Share Posted April 28, 2021 Fascinating stuff Simon. D.D. Quote Link to comment Share on other sites More sharing options...
Stephen Jones Posted April 28, 2021 Share Posted April 28, 2021 Has your depron supply run out Simon. I got some 5mm Depron from B&Q. Steve Quote Link to comment Share on other sites More sharing options...
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