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#51
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High-capacity NiMH cells -- very rapid self-discharge common?
On Fri, 4 Jul 2008 16:59:06 -0400, "Neil Harrington"
wrote: "John Turco" wrote in message ... Neil Harrington wrote: "John Turco" wrote in message edited for brevity I was most intrigued by rubber-powered, stick-and-tissue airplanes, during my model-building days, long ago. edited I remember the rubber-powered stick and tissue models with great affection, though I was never very good at building them. I'd be tempted to get back into rubber-powered free flight now myself, if I didn't already have too many hobbies and too little sense of organization and discipline. Hello, Neil: My first such kit was a Guillow's Hawker "Hurricane," which I purchased at a local "Rexalls" drugstore; it cost the "exorbitant" sum of 69 cents, in 1966! (Hey, that was a lot of money, for a 12-year-old kid, back then. g) I remember the Guillow's kits, also Cleveland kits and plans, and Comet kits in the '40s. Comet kits were usually 10 cents as I recall, and that even included a tiny glass tube of model airplane cement. Not enough cement to actually put the plane together, unless perhaps you were very skillful at economizing on it. Those 10-cent kits were of course the smallest of the several sizes. Wing ribs and fuselage formers, etc., were all printed on a thin sheet of balsa and had to be cut out my hand -- very hard to do with an ordinary razor blade. The first time I attempted to make a kit I glued several sections together using a page of newspaper to protect the table. When I tried to remove the glued sections, great chunks of newspaper came up with the section. I bought a number of kits but never succeeded in finishing one until finally I completed a (somewhat larger) Fokker D.VII when I was about 16. That flew reasonably well but I got tired of doing all that hand-winding of the rubber motor for a very short flight. It wasn't until much later that I learned about more serious modelers using a geared hand-powered drill to wind the motors. That would have saved me a lot of aggravation. I remember hand-winding until the last few turns, and accidently letting go of the prop. Finger-buster. Mostly as a kid I experimented with hand-launched gliders, made entirely of balsa sheet and not requiring any of that tricky building. I didn't return to stick and tissue models until the '60s or so, and then only briefly. I had a brief experience launching balsa sheet gliders from my grandparents' second story porch. I'd glue a thick string of yarn to the body, soak it with lighter fluid, light the plane, and send it off to spiral down like the fighter planes in the RKO newsreels. Great fun...until one landed on a neighbor's automobile's convertible top. Luckily, it only scorched the top, and I was never caught. Never tried it again, though, -- Tony Cooper - Orlando, Florida |
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High-capacity NiMH cells -- very rapid self-discharge common?
"tony cooper" wrote in message ... On Fri, 4 Jul 2008 16:59:06 -0400, "Neil Harrington" wrote: "John Turco" wrote in message ... Neil Harrington wrote: "John Turco" wrote in message edited for brevity I was most intrigued by rubber-powered, stick-and-tissue airplanes, during my model-building days, long ago. edited I remember the rubber-powered stick and tissue models with great affection, though I was never very good at building them. I'd be tempted to get back into rubber-powered free flight now myself, if I didn't already have too many hobbies and too little sense of organization and discipline. Hello, Neil: My first such kit was a Guillow's Hawker "Hurricane," which I purchased at a local "Rexalls" drugstore; it cost the "exorbitant" sum of 69 cents, in 1966! (Hey, that was a lot of money, for a 12-year-old kid, back then. g) I remember the Guillow's kits, also Cleveland kits and plans, and Comet kits in the '40s. Comet kits were usually 10 cents as I recall, and that even included a tiny glass tube of model airplane cement. Not enough cement to actually put the plane together, unless perhaps you were very skillful at economizing on it. Those 10-cent kits were of course the smallest of the several sizes. Wing ribs and fuselage formers, etc., were all printed on a thin sheet of balsa and had to be cut out my hand -- very hard to do with an ordinary razor blade. The first time I attempted to make a kit I glued several sections together using a page of newspaper to protect the table. When I tried to remove the glued sections, great chunks of newspaper came up with the section. That sure sounds familiar! . . . I wouldn't be surprised if every kid did that the first time or so. I bought a number of kits but never succeeded in finishing one until finally I completed a (somewhat larger) Fokker D.VII when I was about 16. That flew reasonably well but I got tired of doing all that hand-winding of the rubber motor for a very short flight. It wasn't until much later that I learned about more serious modelers using a geared hand-powered drill to wind the motors. That would have saved me a lot of aggravation. I remember hand-winding until the last few turns, and accidently letting go of the prop. Finger-buster. My main worry was getting in a turn too many, busting the rubber band with resulting damage to the fragile fuselage. That never actually happened but I always worried about it. Mostly as a kid I experimented with hand-launched gliders, made entirely of balsa sheet and not requiring any of that tricky building. I didn't return to stick and tissue models until the '60s or so, and then only briefly. I had a brief experience launching balsa sheet gliders from my grandparents' second story porch. I'd glue a thick string of yarn to the body, soak it with lighter fluid, light the plane, and send it off to spiral down like the fighter planes in the RKO newsreels. Great fun...until one landed on a neighbor's automobile's convertible top. Luckily, it only scorched the top, and I was never caught. Never tried it again, though, :-) Does sound like fun. Neil |
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High-capacity NiMH cells -- very rapid self-discharge common?
In article ,
"Neil Harrington" wrote: I recently bought some cheap no-name (actually "Tenergy," whatever that is) 2600mAh AA cells on eBay. I haven't tried to assess the accuracy of their rating, don't know how I'd do that anyway, but I'm flabbergasted by how fast they self-discharge -- a couple days or so, sometimes almost overnight, it seems. Tried leaving them on charge overnight, no difference. Tried "conditioning" them in a Maha C204W, still no difference. Charged with a Maha C401FS, individual charging circuits for each cell, still no difference. So far they do not seem to improve with use either. So I tried some more cheap no-name (really no-name this time, just cell info on a pale green case) 2600mAh cells from a different eBay source. Pretty much the same thing. From fully charged they go flat amazingly fast with no use at all. Not actually zero-voltage flat, they'll still light a two-cell flashlight, but flat enough that a couple of days after charging they won't operate an old four-cell Minolta S404 for more than a few shots. I've used no-name (or unheard-of name) NiMH cells from eBay sellers before, with excellent and reliable results, and most of those cells are still giving me good results after several years. But they were of lower capacity, 2000 mAh or less. So I'm wondering if fast self-discharge is a characteristic of these newer 2600mAh NiMH cells in general, or if it's just that cheap cells ain't what they used to be. Neil Some NiMH cells will discharge extremely rapidly when they're hot. I have seen NiHM cells left in a hot car go dead in one day. Generally they're not so bad at normal room temperatures. A faster discharge rate probably indicates poor quality. Throw the 300mA Maha charger in the trash. Fast chargers must produce between 0.3 and 1 times the Ah rate in charging current for the battery to show signs of nearing a complete charge. Your new set of batteries require a charge current between 780 mA and 2600 mA. Below that current, all detectable parameters of the battery are more influenced by external factors than by the charge level. A slight breeze or a passing ray of sunlight can cause the 300mA Maha chargers to terminate charging early or never at all. Some good general NiMH data is he http://data.energizer.com/PDFs/nicke...ide_appman.pdf -- I will not see your reply if you use Google. |
#54
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High-capacity NiMH cells -- very rapid self-discharge common?
Neil Harrington wrote:
"John Turco" wrote in message edited for brevity My first such kit was a Guillow's Hawker "Hurricane," which I purchased at a local "Rexalls" drugstore; it cost the "exorbitant" sum of 69 cents, in 1966! (Hey, that was a lot of money, for a 12-year-old kid, back then. g) I remember the Guillow's kits, also Cleveland kits and plans, and Comet kits in the '40s. Comet kits were usually 10 cents as I recall, and that even included a tiny glass tube of model airplane cement. Not enough cement to actually put the plane together, unless perhaps you were very skillful at economizing on it. Those 10-cent kits were of course the smallest of the several sizes. Wing ribs and fuselage formers, etc., were all printed on a thin sheet of balsa and had to be cut out my hand -- very hard to do with an ordinary razor blade. Hello, Neil: My recollection of Comet, is that it churned out tons of garbage, during the sixties and seventies. The company even sold pre-assembled, rubber-powered planes, offering plastic fuselages and foil-covered balsa wings and tail surfaces. None of those pathetic products had any hopes of flying, whatsoever; they were simply toys, rather than scale models. At the opposite end of the quality spectrum, was Sterling. Its superbly crafted kits contained precision, die-cut parts, silk span (instead of ordinary tissue paper), nicely finished hardware (e.g., wire landing gear, rubber wheels, etc.) and an in-flight "working feature." (This last item could entail dropping bombs or leaflets, firing rockets, etc., depending on the aircraft in question.) Too kewl! g I bought a number of kits but never succeeded in finishing one until finally I completed a (somewhat larger) Fokker D.VII when I was about 16. That flew reasonably well but I got tired of doing all that hand-winding of the rubber motor for a very short flight. It wasn't until much later that I learned about more serious modelers using a geared hand-powered drill to wind the motors. That would have saved me a lot of aggravation. Mostly as a kid I experimented with hand-launched gliders, made entirely of balsa sheet and not requiring any of that tricky building. I didn't return to stick and tissue models until the '60s or so, and then only briefly. Yeah, those "North Pacific" cuties were loads of fun, and they could be had for a nickel apiece! Of course, the rubber-band birds ("Skeeter," "Sleek Streak," etc.) were a bit more expensive...starting at the alarming price of a whole dime. ;-) edited Hip Pocket Aeronautics http://www.hippocketaeronautics.com That site is interesting, but I can't seem to find anything there (or elsewhere) about the slow-flying indoor models covered with microfilm. (I *think* microfilm was what they called it, but it wasn't what you usually think of as microfilm. I believe it was some sort of collodion, and the method of covering wings and other surfaces, including the prop, was to pour some of this stuff on water where it formed a thin film, and then pull the framework of the wing or other surface up through it. Or so I understand; I never built one myself.) Whether "microfilm" is the correct term or not, those models' covering was essentially transparent and weighed next to nothing -- much lighter than tissue -- and it was amazing to see them fly. The big props would turn very slowly, lazily, and the models would fly in large circles, climbing until the rubber motor started to run down. They were so light and flew so slowly that even flying into a rafter near the ceiling didn't damage them. They were only flown indoors in some large space like a big gym or very large aircraft hangar, as they could not have coped with even the slightest breeze. Regards, Neil As for myself, I only saw the "microfilm" babies in magazines. They always struck me as somewhat bizarre, to say the very least. g Cordially, John Turco |
#55
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High-capacity NiMH cells -- very rapid self-discharge common?
tony cooper wrote:
On Fri, 4 Jul 2008 16:59:06 -0400, "Neil Harrington" wrote: edited for brevity I remember the Guillow's kits, also Cleveland kits and plans, and Comet kits in the '40s. Comet kits were usually 10 cents as I recall, and that even included a tiny glass tube of model airplane cement. Not enough cement to actually put the plane together, unless perhaps you were very skillful at economizing on it. Those 10-cent kits were of course the smallest of the several sizes. Wing ribs and fuselage formers, etc., were all printed on a thin sheet of balsa and had to be cut out my hand -- very hard to do with an ordinary razor blade. The first time I attempted to make a kit I glued several sections together using a page of newspaper to protect the table. When I tried to remove the glued sections, great chunks of newspaper came up with the section. Hello, Tony: I did something similar, during my debut...as I'd failed to heed the instruction sheet's advice, regarding the use of wax paper. :-) Actually, if I recall correctly, I intentionally glued the balsa parts, directly to the aforementioned sheet. It seems that I didn't know any better, and was tackling a kit too advanced for my tender age. g edited I had a brief experience launching balsa sheet gliders from my grandparents' second story porch. I'd glue a thick string of yarn to the body, soak it with lighter fluid, light the plane, and send it off to spiral down like the fighter planes in the RKO newsreels. Great fun...until one landed on a neighbor's automobile's convertible top. Luckily, it only scorched the top, and I was never caught. Never tried it again, though, Naughty, naughty! :-J Cordially, John Turco |
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