Mannyroad Posted May 18, 2017 Author Share Posted May 18, 2017 Might have a go tomorrow, as tides don't cover the beach at the moment. Quote Link to comment Share on other sites More sharing options...
Anthony Pattison 1 Posted May 18, 2017 Share Posted May 18, 2017 Hi Manny I assume you mean you want to stop flying once you have used 80% of the capacity and stop when there is about 1Ah left in the battery? The ESC will stop once the batteries are near to ‘flat’ and voltage drops down to something like 3.9v per cell I would imagine. To stop at “20% left” you really need to do a few test flights of perhaps 4mins doing your normal flying and then look at how much energy is pumped back in by the charger. If you recharge and put 2500mAh back in after 4min flight you then know that 4mins of flight is about 50% of capacity so you should be OK for about 6 1/2mins. Given you have a battery of 5Ah you could ‘hope’ for 50A discharge for about 1/10 Hr (6mins) and that would give you about 50A * 20V = 1000Watts. Hence the full battery capacity would give about a 1kW for 6 mins – you are looking for less power at 870W so that gives more time and you won’t be at full-chat all the time so 5 or 6 min flights should be pretty achievable for 80% discharge I would hope. It would be interesting to see what figures you get from a current meter and rpm meter when running the prop you have. It is said that optimum prop would give (70% of kV*voltage rpm) so for your setup that would give 0.7*740*20 = 10,360 rpm….. The nice thing about electric is you do have scope to adjust power/rpm/flightime by prop changing and battery changing – 1kW is pretty hectic for a Mirus but it will fly well! Do keep us informed as I do need inspiration to tackle the 3 Mirus-es I have! Tony Quote Link to comment Share on other sites More sharing options...
Mannyroad Posted May 18, 2017 Author Share Posted May 18, 2017 Hi Tony, Thanks for your comments, much appreciated. I wasn't aware about optimum prop sizing to achieve 70% kv; I always assumed one chose a prop that allowed the motor to achieve 100% kv rpm or thereabouts, so the info is useful. Thanks. Out of interest why 70%? I would have thought this suggests the prop is oversize and likely to over-draw on amps. not so clearly. I've read some guys with the same motor are running 11 x 6 props and bigger so maybe my 10 x 6 will rev too quickly. Might need to source a 10 x 7 or 8 to 'push' the motor. But yeas, will check it out with my watt meter and tacho and see what I get. Quote Link to comment Share on other sites More sharing options...
Mark Kettle 1 Posted May 18, 2017 Share Posted May 18, 2017 I'd love to flying that Mirus, have fun Mannyroad. Quote Link to comment Share on other sites More sharing options...
Anthony Pattison 1 Posted May 18, 2017 Share Posted May 18, 2017 Hi Manny Not sure how scientific the 70% is but I think the kV figure is motor 'no load' speed so 70% gives some sort of efficient loading without bogging it down too much I imagine. Let us know what power figures you get and how early flights go. I hope to get back to models shortly but have just finished rebuilding a new (1963) lathe and have bought a new bike (1975 Trident T160) so need to clear out some stuff from garage before I can begin - better clear a couple of bikes and the old lathe for a start methinks! Good luck. Tony Quote Link to comment Share on other sites More sharing options...
Mannyroad Posted May 19, 2017 Author Share Posted May 19, 2017 Mark, I will i'm sure, but gently gently at first methinks, hee hee. Tony, had one of those Tridents back in 79. A Hyde conversion. Nice. Love the Trident. Not flown my Mirus yet as I'm busy sorting out damage to my custom bobber (Indian Larry Grease Monkey replica), after dumping it down the road on a left hander last month (on a test run after taking over two years to build it!!). But I'll get both of them flown within the next two weeks and will update this thread with how it goes. Quote Link to comment Share on other sites More sharing options...
Anthony Pattison 1 Posted May 19, 2017 Share Posted May 19, 2017 Hi Manny Bike sounds very interesting, sorry to hear of mishap! - perhaps you could photo the Mirus with a Bobber in the background next time! Good luck with test flights. Tony Quote Link to comment Share on other sites More sharing options...
Anthony Pattison 1 Posted May 19, 2017 Share Posted May 19, 2017 Unfortunately someone moved the Mirus from in front of my bikes.... (sorry for off-topic pic!) Tony 1 Quote Link to comment Share on other sites More sharing options...
Mannyroad Posted May 19, 2017 Author Share Posted May 19, 2017 Heeeey Tony, a nice stable of machines you have there. That trident takes me back. mine had same tank colours, best colours IMO. Quote Link to comment Share on other sites More sharing options...
Mannyroad Posted May 19, 2017 Author Share Posted May 19, 2017 This is my build project before it slid down the road. Sorry, its blocking the shot of the Mirus, behind. 1 Quote Link to comment Share on other sites More sharing options...
Alan Pennington Posted May 19, 2017 Share Posted May 19, 2017 Nice bike Manny, sorry about the accident after all the work you have done. What is the engine? Quote Link to comment Share on other sites More sharing options...
Mannyroad Posted May 19, 2017 Author Share Posted May 19, 2017 Thanks Alan. Repairs are in progress and hopefully (if my mate pulls his finger out and gets on with repairing the tank) I should be back on the road in a few weeks. Sorting this out has stopped me finding some time to get the planes aloft; hopefully that will get back on track soon too. The motor is an S&S 84" performance motor. Rare as hen's teeth. Quote Link to comment Share on other sites More sharing options...
Stuphedd Posted December 17, 2017 Share Posted December 17, 2017 This new Mirus turned up today , MVVS 28 powered . 1 Quote Link to comment Share on other sites More sharing options...
Mannyroad Posted December 17, 2017 Author Share Posted December 17, 2017 Its a plane with great prescence howling through the sky. How did it go with that set up? Quote Link to comment Share on other sites More sharing options...
Gwyn davies Posted January 30, 2023 Share Posted January 30, 2023 I just bought one, it an original 1980s model, just wondering can you tell me where the C of G is supposed to be? I'm praying somebody will see this I mean it is 2023 now!! Super tiger 45 sports upfronts cannot wait to fly this little beast👍 many thanks Quote Link to comment Share on other sites More sharing options...
Piers Bowlan Posted January 30, 2023 Share Posted January 30, 2023 (edited) This was posted earlier in the thread. It shows the C of G behind the aft wing bolt, the question is how far behind, there is no scale on this plan? It also assumes the rear wing bolt on your model is true to plan! Perhaps you will just have to wait for someone with a Miras to post. Miras Plan.pdf Good luck with the maiden, it should be exciting 😁 Edited January 30, 2023 by Piers Bowlan Quote Link to comment Share on other sites More sharing options...
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