Rich Griff Posted September 18, 2021 Share Posted September 18, 2021 I know I have commented about velcro and it's very handy use for holding batteries in place in model aero planes. My comments are used to make builders question its use. Is one square inch of the stuff enough ? When I finally grasp the nettle of electric powered flight I very well may use the method myself, with a long strip taped to the battery, a similar strip stitched to the model fuz "shelf", and, at least 2 strips strapping the battery through/to the shelf, firmly holding the battery in place. The shelf it's self would have to be strong enough to "hold" the load in the fuz, else the whole lot would just get flung from the fuz due to either positive or negative gee overload. Belt and braces, and strong wings etc.. Question, Does modern radio gear have a built in real time gee meter telemetry back to the tx to give a warning of gee overload being approached ? Next question, what value of gee constitutes an overload for that particular model and manouver ? Or am I being "over the top" on this subject. Probably a cautious common sense approach is all that is needed... I will have to look up the formula for centrifugal force...not forgetting to add gravity for the down hill component... Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted September 18, 2021 Share Posted September 18, 2021 You are indeed being over the top with this subject. If your battery is secured with one or more Velcro seat belts which hold the battery in place a small piece of velcro on the battery can be used to stop the battery sliding on the battery tray. Though many of my models are fitted with velcro straps for battery retention I'm also a fan of keeping the battery firmly wedged in place with small wooden retainers that lock into place in the airframe. Quote Link to comment Share on other sites More sharing options...
Dickw Posted September 18, 2021 Share Posted September 18, 2021 50 minutes ago, Rich Griff said: I know I have commented about velcro and it's very handy use for holding batteries in place in model aero planes. ...................................................... Question, Does modern radio gear have a built in real time gee meter telemetry back to the tx to give a warning of gee overload being approached ? ................................. Or am I being "over the top" on this subject. Probably a cautious common sense approach is all that is needed... To continue a discussion we started elsewhere - I have attached a photo as requested. The battery weighs 780 grams and doesn't move however much I throw the plane about To answer some of your questions - yes you can get real time G force telemetry on some modern RC equipment. I can get it from some Gyro assisted receivers I have and I have also built an arduino based stand alone telemetry sensor based on this information https://www.rc-thoughts.com/jeti-g-force-sensor/ The G force that constitutes an overload is dependant on the model design, the materials used, and the current condition of the whole thing, so is almost too variable to be "known" in most cases. Looking at G force logs you can see that the peak forces tend to occur so rapidly that by the time you were aware from telemetry it would be too late to do anything about it. I put G force telemetry in the category of fun to play with but no real use in practice for regular flying. Just stick to common sense. Dick Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted September 18, 2021 Author Share Posted September 18, 2021 As said electric powered flight is new to me, so I am learning. The batteries are a pouch type ? I assume they are seperated to aid cooling ? As a matter of interest how much do they weigh please and what's the duration like at say full powered flight ? Yes I know , full powered flight for the whole flight is not common, but it gives me an idea... Gee meter telemetry ? Thanks. Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted September 18, 2021 Author Share Posted September 18, 2021 Just seen your "reply" helpfully usefully info thanks. I will be asking many many more electric questions as it is the way to go, fuel, prices, noise etc., so it's gunna have to happen eventually. Thanks. Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted September 18, 2021 Author Share Posted September 18, 2021 Woooooo, now that's a very nice looking fuz structure, lots of voided webs etc.. The velco' d battery looks about the size of the " old" nicads car type, same sort of wieght ? Thanks.. Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted September 18, 2021 Share Posted September 18, 2021 Those are a pair of 3s1p Loong Max 4300mah lipos, arranged in series to make a 6s1p4300mah pack. The individual packs weigh in at 343g each, so 686g in total. The sadly missed Loong Max batteries were beautifully constructed and blew many of the more expensive packs out of the water -individual cells had an air gap between them and trimmed back clear heatshrink which helped with cooling. The Aerowatt pictured easily had 8 minutes of fully aerobatic flight and was actually overpowered on 6 cells, I now fly her on a 5s1p 5200mah G-Power pack- those weigh 596g, fully charged. You really don't need a g-meter, either recording of with telemetry and certainly not to determine your battery retention. It would be massively overthinking a non-issue. Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted September 18, 2021 Author Share Posted September 18, 2021 Thanks both, all useful info which I am soaking up/in. Thanks... Quote Link to comment Share on other sites More sharing options...
Dickw Posted September 18, 2021 Share Posted September 18, 2021 1 hour ago, Rich Griff said: Woooooo, now that's a very nice looking fuz structure, lots of voided webs etc.. The velco' d battery looks about the size of the " old" nicads car type, same sort of wieght ? Thanks.. The structure is typical of many ARTFs and in this case it is a Sebart Pitts which weighs just over 3Kg with battery in. https://themodelshop.net/sebart-pitts-python-50e-yellowblack-seb-p50-yb-1047-p.asp The battery is a 6s 5000mAh - very similar to leccyflyer's (and I agree with his comments about Loong Max as I still use one in that plane). Most (if not all) electric planes these days are powered by Lithium Polymer cells (Lipo) as they are much lighter than equivalent sized 'nicads' would be. I have no idea what the "full power flight time" would be as that would be most unpleasant flying. I don't even need full throttle to take off! I fly for 10 minutes at a time and rarely use more than 3000mAh. Even after 10 minutes I can prop hang and climb vertically as far as i like. Dick 1 Quote Link to comment Share on other sites More sharing options...
leccyflyer Posted September 18, 2021 Share Posted September 18, 2021 Dick - I've retired my Loong Max packs, so they are currently sitting at storage voltage, but only because I don;t currently fly anything on a 6s1p pack. The cells are still in excellent shape, without a hint of puffiness and they were bought in 2009. I could put them back into service as 3s1p 4300mah packs I suppose. Marvellous batteries, which IIRC came out as clear winners in the comparative tests that BMFA News did about 10 years ago. The Aerowatt originally flew on 16x2400SCRC Sub-C Nicds, with a Mega R7 brushed motor and had superb performance even then. My dearly missed mentor Peter Wilson designed and built the model for the BEFA Millenium bash and passed her on to me after he developed the design further to make his JP Specials Lipo 1 and Lipo 2 designs. The Aerowatt is my most cherished model and I think of Peter every time I fly her. Quote Link to comment Share on other sites More sharing options...
GrumpyGnome Posted September 18, 2021 Share Posted September 18, 2021 @Rich Griffknowing the duration for Dick's plane is pretty meaningless tbh... unless you have an identical set up and fly the same way, your duration will differ. Some examples... I get 10 minutes of mixed flying from a 260mah 2s in my c-ray; 3 minutes from my 1500mah 3s in my Viper and 6 minutes from my 2200mah 3s in my Wots Wot ... all flown in a similar manner. If I fly pretty much wide open on the Viper, I get around 2 minutes to 3 minutes, dependant on battery make... Go for a battery that will physically fit, allows you to obtain correct balance if possible, that delivers enough power and duration for your needs. A wattmeter, and something like ecalc is your friend... as are people on this forum if you say what you have and what you want. George at 4mac is also a font of knowledge... Quote Link to comment Share on other sites More sharing options...
Dickw Posted September 18, 2021 Share Posted September 18, 2021 I think my Loong Max is probably a bit newer than yours so still in successful regular use. The Aerowatt does indeed look a nice plane, and no doubt improved when converted from Nicds to Lipo. My first big electric aerobat also flew on Nicds back in the early 1990s - in that case 26 x 1200 sub-Cs and a big German 'Geist' brushed motor. Unfortunately the spar proved inadequate for all the weight so it didn't survive into the Lipo era ? Dick 1 Quote Link to comment Share on other sites More sharing options...
Shaun Walsh Posted September 18, 2021 Share Posted September 18, 2021 4 hours ago, Rich Griff said: I know I have commented about velcro and it's very handy use for holding batteries in place in model aero planes. My comments are used to make builders question its use. Is one square inch of the stuff enough ? When I finally grasp the nettle of electric powered flight I very well may use the method myself, with a long strip taped to the battery, a similar strip stitched to the model fuz "shelf", and, at least 2 strips strapping the battery through/to the shelf, firmly holding the battery in place. The shelf it's self would have to be strong enough to "hold" the load in the fuz, else the whole lot would just get flung from the fuz due to either positive or negative gee overload. Belt and braces, and strong wings etc.. Question, Does modern radio gear have a built in real time gee meter telemetry back to the tx to give a warning of gee overload being approached ? Next question, what value of gee constitutes an overload for that particular model and manouver ? Or am I being "over the top" on this subject. Probably a cautious common sense approach is all that is needed... I will have to look up the formula for centrifugal force...not forgetting to add gravity for the down hill component... g meter; Spektrum G meter Next question, what value of gee constitutes an overload for that particular model and manouver ? If the wings fold, you are in an overload situation! If not, you're OK. I never rely on Velcro on the bottom of the battery to secure it from solo flight. All my batteries are either held in with one or more Velcro straps or wedged into the forward section of the fuselage where the only way out is backwards where it will only experience slightly over one G in a vertical climb. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted September 18, 2021 Share Posted September 18, 2021 Just a point but there are constant loads and instantaneous shock loads. Constant G force you can account for but by far the most likely problem of battery security is an shock load. i.e from 'unwanted contact with the ground'. Of a short duration (fraction of a second) but can be 3 or 4 times higher. In this respect Velco is good as it has a degree of 'give' in it to absorb the shock load. So Velco holding a battery down should have no problem with an downward shock loading but more likely a rigidly fixed battery tray could collapse taking the securely fixed battery with it. This then raises the question of designing in what order and how the whole plane structure should fail to protect any delicate items. There is nothing like making a simple solution complex! Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted September 18, 2021 Author Share Posted September 18, 2021 (edited) The idea of a gee meter is to warn of an approaching overload situation BEFORE failure of battery velco'/wings etc...not like an air bag that suggest you have just hit something, but point taken. I would consider a battery box with airflow and locking the battery in via a white foam block, it's self held in place by a hatch or banded wing etc.. just like in my slopers, gliders and powered planes, even boats so ballast doesn't move. Remember a fliers lipo fell out doing a loop recently, not the first time it's happened... I tend to go on the assumption that... A lipo falls out, crap happens...my bad. Another lipo falls out...coinsidence, their bad, crap happens... A third lipo falls out, something is very wrong !!! CAA reports etc. Highlite the problems....report it on here as well so lookers in can learn from the "accident" Safe flying is no accident We can all learn. Edited September 18, 2021 by Rich Griff Quote Link to comment Share on other sites More sharing options...
Dickw Posted September 18, 2021 Share Posted September 18, 2021 55 minutes ago, Rich Griff said: The idea of a gee meter is to warn of an approaching overload situation BEFORE failure of battery velco'/wings etc...not like an air bag that suggest you have just hit something, but point taken. ........................................ I can see where you are coming from with that suggestion, but you don't have to hit something to get sudden high Gs. I flew my Pitts just after I took the photo of my battery straps above and attached is part of the data log showing the G forces in the 3 axes during the flight. Most of the flight is in the 2 to 3 G region or below but there are a few brief excursions up to 7 or 8 G, and I can assure you I didn't hit anything ? they are just flying loads in lively aerobatics (e.g. both sticks in the top right/left corner). Telemetry tells you what just happened, not what is going to happen next. Dick Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted September 18, 2021 Author Share Posted September 18, 2021 8 gee, gosh...just shows how much the airframe as a whole experiences... As a matter of interest how heavy is the aircraft ? Good job the Rx doesn't " black out"... Again, how heavy is the battery ? Quote Link to comment Share on other sites More sharing options...
Dickw Posted September 18, 2021 Share Posted September 18, 2021 Pitts Python 3200gm ready to fly - of which the 6s 5000mAh battery is 780gm. Dick Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted September 18, 2021 Author Share Posted September 18, 2021 Does that mean the effective weight of the battery suddenly leaps to 6.24kg momentarily? Quote Link to comment Share on other sites More sharing options...
Dickw Posted September 18, 2021 Share Posted September 18, 2021 It seems logical that it does. Dick Quote Link to comment Share on other sites More sharing options...
Dickw Posted September 18, 2021 Share Posted September 18, 2021 Of course, if the G sensor is not rigidly fixed in place it could be moving slightly relative to the airframe and giving a false reading! Dick Quote Link to comment Share on other sites More sharing options...
Geoff S Posted September 18, 2021 Share Posted September 18, 2021 It's surprising how high values of G can reach under even apparently innocuous operation. Some years ago (many, now!) I was heavily involved in the design of a radio telemetry system to measure temperature, stress etc in gas turbines. Our electronics were housed in an annular containment ring about 400 mm diameter IRC. It rotated at about 7k rpm and apparently subjected the electronics to 20,000G! All the circuits were embedded in epoxy and we got no failures due to G other than the wires which led to the strain gauges and thermocouples,which progressively failed during a test. We had a graduate who was intending to do a Phd studying failure due to G of integrated circuits and he had a centrifuge to conduct the tests. Unfortunately, he was unable to record any failures which made his proposed thesis a bit thin! The only aircraft I've lost batteries in flight have been, one: a very small Depron biplane with the battery attached by Velcro underneath. The battery fell out and the model did a perfect landing unaided by anything bar gravity! And two, my Multiplex Fun Cub which shed its battery part way through a bunt. It floated gently to earth inverted, again with zero damage. I've made alternative arrangements for battery security and had no further problems. I really don't think there's any need to measure the G forces on a model. I use Velcro straps round the battery and Velcro on the battery and platform to stop sliding. It just isn't a problem. Quote Link to comment Share on other sites More sharing options...
PatMc Posted September 18, 2021 Share Posted September 18, 2021 Is the G force always measured in one plane (not aeroplane) parallel to the fixed plane of the G meter ? Quote Link to comment Share on other sites More sharing options...
PatMc Posted September 18, 2021 Share Posted September 18, 2021 2 minutes ago, Geoff S said: And two, my Multiplex Fun Cub which shed its battery part way through a bunt. It floated gently to earth inverted, again with zero damage. The Fun Cub or the battery ? ? Quote Link to comment Share on other sites More sharing options...
Geoff S Posted September 18, 2021 Share Posted September 18, 2021 27 minutes ago, PatMc said: The Fun Cub or the battery ? ? Guess! Quote Link to comment Share on other sites More sharing options...
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