Erfolg Posted August 18, 2016 Share Posted August 18, 2016 Ah, yes, following the design principles of Lotus in its prime and pomp, right on the edge, where the odd component failure was acceptable, in pursuit of that last bit of performance. Quote Link to comment Share on other sites More sharing options...
Stephen Jones Posted August 18, 2016 Share Posted August 18, 2016 Posted by Steven Shaw on 18/08/2016 12:56:28: Shouldn't your wiring be a couple of gauges heavier?>> +1 Spot on. Also you will be losing energy through heating the wires. Steve Quote Link to comment Share on other sites More sharing options...
Martian Posted August 18, 2016 Share Posted August 18, 2016 Could have been a spectacular fiery end Quote Link to comment Share on other sites More sharing options...
Andrew Price 2 Posted August 18, 2016 Share Posted August 18, 2016 Erfolg. I seem to remember reading that Colin Chapman used to say something like "Anyone can design a bridge, that is not a problem. The trick is to design a lightwieght bridge that only just stands up". Quote Link to comment Share on other sites More sharing options...
Mannyroad Posted August 18, 2016 Share Posted August 18, 2016 Yep, its called engineering. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted August 19, 2016 Author Share Posted August 19, 2016 It appears that Depron (polystyrene) has about the lowest melting points of the common plastics about 200 C! The reason for overloading the wire (well over twice it 'rated' current) was two fold. 1. As the motors wires were always going to be long weight is important. 2. And perhaps more important the 70 mm EDF motor is only rated for a 3S LiPo. So it was to either use 'heavy' wire and a 3S and hope the voltage drop was not too significant or light wire, 4S and use the voltage drop to "protect" the EDF. No question the second option seemed a better bet for VTO but what I did not expect was just how hot the wires must have got. What is interesting is that where the wires exit the fuselage to reach the EDF there is no melting of the Depron. This suggests there is sufficient cooling going on to keep the temperature down. Pressing on with the repairs the formers restored and cardboard mounts being added to retain the wires. As a test the cardboard did not "char" from several minutes application of a soldering iron so hopefully those hot wires will now keep clear of the snake! Quote Link to comment Share on other sites More sharing options...
Erfolg Posted August 19, 2016 Share Posted August 19, 2016 I have no issue at all with the old Lotus set up, in that it the design fore filled its purpose to win a race, accepting that the design would have limited life and possibly could unintentionally fail in service. Which for Joachim Rindt lead to his death. It seems that Simon is also at the limit of the envelope. I guess that he is accepting that the model is susceptible to damage, that Lipo life is possibly limited, or is it the fan unit, etc. It is certainly quite an accomplishment. I am guessing that Colin Chapmans comments were tongue in cheek, as designing and building a bridge that is both functional, designed and built to cost, with both a required operational life and maintenance regime is not to be sneered at. Many F1 engineers and aircraft designers could not achieve the requirements. Although this general comment is true throughout engineering, it is a challenge to meet the specification in all the aspects. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted August 23, 2016 Author Share Posted August 23, 2016 With all the skin made good the weather this morning was calm enough to find out if the 'heat resistant' mountings actually worked. No problem with a nice VTO and good 4 minute flight. Of course as everything is completely buried I can't actually tell if anything is melting but as the top snake is still working it can't be that bad! Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted August 24, 2016 Share Posted August 24, 2016 Hello Simon, I sent you a PM, could you have a look, please. Hakuna matata Chris BRU - BE / CTR PM Control Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted December 17, 2020 Author Share Posted December 17, 2020 The story continues. The final demise of my V-2 occurred when its EDF disintegrated as it was lifting off. The result was a very realistic crash almost identical to failed launches filmed at Peenemunde but of course without a fire ball but the damage was pretty severe. Not only the badly crumpled nose but the EDF blades had all separated and damaged much of the complex ducting at the rear as the blades broke free. Not unlike a compressor disk failure! Such a failure was not completely unexpected as the EDF was only rated for 3s not 4 and the 'instant' full throttle required for a VTO only added to the blade stresses. Although not repaired at the time, Aug 1018 ,the remains of the airframe were 'tided up' a bit. Then put into store simply because I hate to throw anything away. Move on two years and my experiments with contra rotating fans indicated I was unlikely to achieve a similar thrust to weight to fan diameter as a plain EDF so a new 'project' was conceived to use a small drone motor driving a 4" 4 blade ducted prop. It could produce a useful level of thrust (about 600g or 21 oz) but it would only use 1/3 the amps of the EDF. A VTO would depend on keeping the total weight sufficiently low. First the old EDF casing was removed. This showed that the basic inner inlet profile of the fuselage was undamaged and would provide a rigid place to mount a motor with a pusher 4" prop. This would allow a suitable light weight Depron duct to be added supported by the fins. However just as with the original EDF version a VTO success is certainly not guaranteed! Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted December 17, 2020 Author Share Posted December 17, 2020 The story continues. The final demise of my V-2 occurred when its EDF disintegrated as it was lifting off. The result was a very realistic crash almost identical to failed launches filmed at Peenemunde but of course without a fire ball but the damage was pretty severe. Not only the badly crumpled nose but the EDF blades had all separated and damaged much of the complex ducting at the rear as the blades broke free. Not unlike a compressor disk failure! Such a failure was not completely unexpected as the EDF was only rated for 3s not 4 and the 'instant' full throttle required for a VTO only added to the blade stresses. Although not repaired at the time, Aug 1018 ,the remains of the airframe were 'tided up' a bit. Then put into store simply because I hate to throw anything away. Move on two years and my experiments with contra rotating fans indicated I was unlikely to achieve a similar thrust to weight to fan diameter as a plain EDF so a new 'project' was conceived to use a small drone motor driving a 4" 4 blade ducted prop. It could produce a useful level of thrust (about 600g or 21 oz) but it would only use 1/3 the amps of the EDF. A VTO would depend on keeping the total weight sufficiently low. First the old EDF casing was removed. This showed that the basic inner inlet profile of the fuselage was undamaged and would provide a rigid place to mount a motor with a pusher 4" prop. This would allow a suitable light weight Depron duct to be added supported by the fins. However just as with the original EDF version a VTO success is certainly not guaranteed! Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted December 20, 2020 Author Share Posted December 20, 2020 Starting to make good the damaged fuselage formers. This shows the state of some of them before the repairs. The Depron duct around the 4" prop. It has printed leading and trailing edges to aid rigidity. Less than 1 mm prop tip gap The four fins do provide good support to the duct but on a 4s it will be rotating at 30,000+ rpm. Whether it is all rigid enough we shall have to see. Quote Link to comment Share on other sites More sharing options...
Stephen Jones Posted December 20, 2020 Share Posted December 20, 2020 I made also made my own duct for my fantrainer and used a larger prop cut down to size as back then we could not get four bladed props. But i made my duct out of 1/64th ply which was built up in 3 layers and epoxy glue used this was because my plastic duct failed due to the difference in air pressure inside the duct causing the prop to cut the duct. Steve Quote Link to comment Share on other sites More sharing options...
J D 8 Posted December 20, 2020 Share Posted December 20, 2020 I just love your optimism Simon as to what will work, still you wont know until you try. Good luck and stand clear, flying goggles on. Cheers, John. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted December 20, 2020 Author Share Posted December 20, 2020 JD 8 This will be a 'minimum power' alternative to using a proper 70 mm EDF as in the original. At just 15A (instead of 45), a tiny Little Bee 20A ESC and a stability rx it should need a much smaller battery than the 1800 mAh original . Added together it still might allow a VTO but still using the same airframe. One thing is certain it will make a lot of noise. First test of the prop and duct on a 4s. It is doing about 30,000 rpm! . Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 3, 2021 Author Share Posted March 3, 2021 It has been worked on between other things so is now virtually complete. It has a Lemon 3 axis stab receiver. Still no flying due to Covid so I organised a indoor thrust test to convince myself it had a thrust greater than its 555 g weight. https://www.youtube.com/watch?v=JGeWGZKc8bA It certainly lifted off! It was running on a 1000 mAh 4s. The intended flight battery is a 850 mAh 5s so it should have yet more thrust provided the prop can withstand it.? 2 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 31, 2021 Author Share Posted March 31, 2021 With the fine weather and the Covid 19 relaxation I took the opportunity to test the MK2 V-2 with wings. https://www.youtube.com/watch?v=61ZvkRic3_E&t=21 It still flies nicely although it does not lift off quite a fast as it did with the 70 mm EDF but then the Mk2 is only using 250W giving 215 W/ib compared to 600W and 300 W/lb!. The Mk2's 4x4 four blade prop (102 mm) is rather more efficient at converting the Watts into thrust than the 70 mm EDF. This also means it can fly on very little power so the total flight endurance is if anything longer on its 850 mAh 5s that it was with the original 1800 mAh 4s. 1 Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted March 31, 2021 Share Posted March 31, 2021 Love it Simon, get it loaded when you come to ours. Quote Link to comment Share on other sites More sharing options...
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