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Andrew McKelvey 1

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  1. The only difference between an analogue servo and a digital one is the input amplifier that reads the signal from the receiver which is analogue, it either converts the train of pulses to a digital signal based on length of time the signal is high or it doesn’t, it then compares this signal to what the feedback loop is saying, the position of the servo horn and drives it one way or the other to match what your tranny stick is saying you want it to be. The servo hardware is likely to be of better quality in a digital servo than a cheap analogue servo because they can charge more and yes there are benefits but the digital bit is the amplifier A/D converter call it what you want. The rest is advertising hype but I do use digital servos in my bigger models that require more torque to move a bigger flying surface
  2. I fly a EP Boomerang it has a 13x6 prop and 70amp Esc, I think it’s some where around 1000kv motor and now fly it on 60C 4cell LIPO because my old 4cell 20c Lipo’s where getting tired. This model flys in all weathers and I don’t fly it like a trainer, loops, rolls, and goes vertical etc. Struggles with knife edge and prop hanging. I got it because I had an extended layoff during the pandemic and didn’t want to practise on my hanger queens and I can’t fault it, I had all the bits in stock and the model cost just over £100 a couple of years ago. My Boomerang had the bits to fit IC or Electric and the LIPO goes in the front where the tank would have been, never been an issue swapping a battery out
  3. Futaba on FASTT, 6Ex, 7C 8FG, I think it was the y lead because I put the servo on the tester and it was perfect, sprayed contact cleaner on the terminals of the lead and tested using radio and no sign of glitching, even flown it this afternoon with no issue.
  4. Flew the repaired model yesterday bit of trim tweaking and all ok
  5. I class myself as a reasonably competent flyer have a A so can’t be that bad.. On nice days when it’s calm I fly a Super60 Low Wing and you can never get two decent take offs in a row, ground handling is not its strong suit, but it does fly nice. I also fly a Boomerang and fly that in any weather, stick forward let it rip and normally it flys itself, it has a steerable nose wheel, I also tend to not fly it in trainer mode and have found that thumbs off if you get into difficulty it sorts itself out. You just got to fly three mistakes high. My suggestion would be to get Fran some air time flying the Boomerang, 10,20 flights in and see what happens. My mentor told me all those years ago - you don’t start flying until after your solo / test when you have to figure out what you need to do, it is a confidence thing. As for people sitting too close to the runway ‘jeering’ at some ones dodgy take off, they should be told and should know 50m at least
  6. How long should a servo last? I have read a number of old posts to try and find an answer but most seem about how to test, do you use a tester or radio but my question is this. You are doing your preflight check and your aileron servo is a bit jittery, never was in the past so you abort flying today until you check it out but you think back that plane is 15 years old and the servos are the same age, it is an easy job to stick a new servo in but not nessesarily of the same type, but what of the old servo, I have in the past stripped a servo down given it a spray with electrical cleaner around the pot and brought it back from death..would you trust it. Also I swapped a servo of a different brand into a wing the other day of my glider, not really thinking much about it, but same orientation horn on the same side and did a preflight check and it rotates in a different direction than the original, never seen it before. Have I just been lucky?
  7. Took some photo's today. Not a great lot to see. I have been bonding the foam back together with 12h Araldite because it gives plenty of time for manipulation, once I have it back solid I'll give it a once over and see if I need to do any thing else. I am using the canopy as means to line it all up it is attached with elastic bands at the mo but the magnets do hold it in place.
  8. TBH there isn't much to see. The front of the fuz had bent up and bellied out at the sides and the canopy wouldn't fit, attached by magnets, there is a split under the the fuz basically it needs straightening and staying that way
  9. I have a Calypso glider that I was flying the other day and one minute it is up in the sky and the next it is two fields away and I am struggling with it. Suffice to say It went behind some trees and it gets a bit difficult to gauge where the ground is so fingers off sticks and wait..I had landed out and vaguely knew which direction to go in so off I trot. Two fields away and I am in a field full of mummy sheep and baby sheep and three of the baby sheep are showing interest in what looks like a glider. When I get there and scare the sheep away from chewing the said glider it isn't in bad shape just out of shape, gone in nose first canopy is off but it is intact. Asking back at the flying field how do I straighten that and get rid of the bite marks, the considered opinion seems to be hot water or steam but I forgot to ask what am I looking for when I immerse it in hot water or steam, on no account use a hot air gun it will melt it. I clamped a couple of wood blocks to the outside of the fuz to flatten the bulge and now the canopy fits but I need to glue the bit where it split. The question is 1. If I pour hot water on it what effect am I looking for, what do I do next, of course I used my hot air gun because I don't have steam or hot water in my model room. Does foam have memory, do I heat it and push it back into shape, or do I get it back in shape and heat it, any thoughts. 2. I don't have UHU Por and generally use 5 minute Epoxy Glue from a well known Toolstore which I haven't had any issues with, would PVA do the job, will CA do, do I glue it clamp it and go away for 24hours. 3. How do I remove bite marks. 4, The tail plane and rudder has always had a strange profile, ever since I have had the plane, looks a bit curled up at the ends, there are no stiffeners so should I worry about it, it normally fly's ok, would carbon fibre rods be of benefit. The only thing I found abnormal when rescuing the plane was the elevator horn had become detached from the elevator, it is only glued, I don't know if it came off up a height or when it hit terra firma but I did struggle keeping it up when it was coming down? Anyone any bright idea's
  10. Someone somewhere thinks there is validity in being able to measure cell resistance, my question is what do you do with the answer, no one has gone near an answer yet
  11. The video I watched showed typical resistance values for a new battery 4 cell of between 6 and 8 micro ohms, shown on the charger per cell, so adding them together is more than 20 micro ohm so that would write off a new battery so I took it as a value for each cell of over 20 would be enough to write off a battery of cells. My chargers don’t calculate the cell resistance, probably because they are circa 10 years old and reasonably cheap.
  12. DickW I think I may have found an answer on the t internet, There is a dc test to calculate battery internal resistance, open circuit voltage (OCV) with no load, followed by the second reading with a load; Ohm’s law calculates the resistance value (voltage difference divided by current equals resistance).= internal resistance. My guess would be the higher the load current the more accurate the result? I also found a video of a guy explaining the in’s and out’s of lipo’s, not sure his qualifications but he sounded like he knew what he was on about. His take on it was New battery’s of various capacities return an resistance of below 10micro ohms and continue to be usable up to 20 micro ohms and any thing above that should be retired. I normally use a 12v 60w headlamp bulb to discharge any unused lipos back to storage voltage (actually x2 to increase the current) The effect of the higher internal resistance reduces terminal voltage under load, the prop spins slower and causes more heat to be generated in the battery which makes it hotter and thus not what we want. This has taken most of the day so now I need to test my older lipo’s, thanks for the input guys
  13. I didn’t fly for about three of those due to the pandemic so they where stored with a storage charge and never abused before hand. I have one of those data loggers that got a write up in RCM&E a few years ago and have used that, my charger will only discharge at a few amps, I was hoping to emulate a real life situation and pull about 40A and see what that did to voltage etc but apart from giving me some electrical values how does that equate to how good the battery is? I have only ever binned one battery that puffed up severely, they seem to get demoted to powering hand drills etc but discovered that Li-On cells from laptop packs do a good job there after the ni-mh and ni-cads pack in. Requires surgery with a dremel but at least keeps then out of the landfill.
  14. I have just reinvested a healthy chunk of money in buying some new li-po batteries in the belief that the old ones I have may no longer be up to it. aka 4cell 3300mAh 60C as compared to the same with 20C and being about 6 years old or more. The comparison using my wattmeter with fully charged batteries in my plane setup gives nearly a 100 w difference , ie a difference of about 6 - 8A draw at full throttle and the older battery being about a volt or more down on the new one. I know this is down to internal resistance of the battery which has worsened with age and I could do comparison checks of my older battery's against new one but I am reluctant to do a load of testing with an 12x6 prop wizzing round at full chat just to provide the load plus the wind factor isn't good in the model room. The questions! 1 How do you test an battery for capacity and obtain comparative results 2 If you manage to compute the internal resistance of said item how do you determine a pass or fail 3 Is there a method or a bit of technology I can use that will mean I am not holding down my plane and applying full throttle and trying to read the numbers on my wattmeter. Your thought please will be gratefully received, I have more than enough electrical test equipment to do the measurements I just dont know what the results mean other than the old battery makes the plane unflyable and the new ones make it a pleasure to fly.
  15. I have a HP Envy 4500 think it is about 4 years old now, bought it in Currys, it is combined inkjet printer scanner copier and prints double sided A4 is wifi enabled so you can print direct, via a network or has a printer cable port and for the money was/is a cracking printer cost about £49 and there are newer versions available that has the same functions. Never had an issue with it and setup is a doddle. The downside, depending upon how much printing you do the combined 301 colour and black cartridge pack are around £26 and buying them singly significantly bumps the price up, a 301 Black cartridge is about £19, you can get an XL version but I have never used one, the tri colour lasts longer than the black because I don't print a lot of colour. The upside of this is you can use the printer in single cartridge mode, a setting deep in the software so if your black runs out at an inopportune moment you can still print, single cartridge mode I think it's called.
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