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Model Forum / Radio Controlled / Air Models / July 2004burnt out speed control when prop is blocked...
My plane flipped over and the prop hit the ground staying a few seconds locked with 1/2 throttle. When I finally releases the prop, noticed the speed control had burnt out! Shouldnt the speed contls come with any sort of protection to avoid? thanks guys. It was a Great planes c-5 nano spc, hoocked to a 600mah, 7.2V batt. The current has to go somewhere, and will pick on the 'weakest link'. Therefore, "Speed Controller.. You ARE the Weakest Link....goodbye." KayCee Foamie Experimentation Engineer > My plane flipped over and the prop hit the ground staying a few > seconds locked with 1/2 throttle. When I finally releases the prop, [quoted text clipped - 4 lines] > > It was a Great planes c-5 nano spc, hoocked to a 600mah, 7.2V batt. > The current has to go somewhere, and will pick on the 'weakest link'. > Therefore, "Speed Controller.. You ARE the Weakest Link....goodbye." [quoted text clipped - 10 lines] > > > > It was a Great planes c-5 nano spc, hoocked to a 600mah, 7.2V batt. In the earlier days of electric flight, it was standard practice to put a fuse in the circuit. Its purpose was to blow in case the motor was stalled in the event of a crash. Does anybody still do this today? Morris | > > My plane flipped over and the prop hit the ground staying a few | > > seconds locked with 1/2 throttle. When I finally releases the prop, | > > noticed the speed control had burnt out! Shouldnt the speed contls | > > come with any sort of protection to avoid? Some might, but this protection would add to the weight and cost of a speed control. ... | In the earlier days of electric flight, it was standard practice to put a | fuse in the circuit. Its purpose was to blow in case the motor was stalled | in the event of a crash. Does anybody still do this today? Yes, people still do this. In fact, just about everybody should. A fuse is almost always a good idea on any circuit where a lot of current can flow. Exactly where you should put it depends on a few things ... In any plane, you can put one between the ESC and battery, and that's often the safest place, but the danger is that if the fuse blows and you have a BEC, your receiver just lost power and your plane is out of control. Of course, it's likely that your plane is on the ground when this happens, but it's possible for your motor to sieze up in the air too. So for a brushed motor, the best place for the fuse is usually between motor and ESC if you have a BEC, because if it does blow, you can still land your plane. For a brushless motor, you'd need at least two fuses between ESC and motor -- one fuse on one wire would not be adequate. And if your motor has a sensor, don't put a fuse on that wire, but instead on two or three of the three power lines. But one fuse between battery and ESC would certainly work too. In that case, you need to weigh your situation and decide what to do.  SignatureDoug McLaren, dougmc@frenzy.com He was as tall as a six-foot-three-inch tree. Kill the throttle if you are about to meet with the ground! Works every time. No additional weight, cost or complexity. You can train yourself to do it, or add parts to your plane and hope they actually work when you do something stupid and preventable. Fuses don't always burn through when you need them to and sometimes do burn through when they shouldn't. Pick an amp value too high and the ESC will burn out anyway. Pick a value too low and they will burn out just when you need full power to get out of a bad situation. Morris Lee opined >> The current has to go somewhere, and will pick on the 'weakest link'. >> Therefore, "Speed Controller.. You ARE the Weakest Link....goodbye." [quoted text clipped - 14 lines] >fuse in the circuit. Its purpose was to blow in case the motor was stalled >in the event of a crash. Does anybody still do this today? For larger motors, yes. But when a model is under 16oz there is little room for fuses and switches. -ash Cthulhu for President! Why vote for a lesser evil? > My plane flipped over and the prop hit the ground staying a few > seconds locked with 1/2 throttle. When I finally releases the prop, > noticed the speed control had burnt out! Shouldnt the speed contls > come with any sort of protection to avoid? Yes, if you don'=t mind the extra half ounce, the extra $10 and the extra 5% power loss.... > thanks guys. > > It was a Great planes c-5 nano spc, hoocked to a 600mah, 7.2V batt. | > My plane flipped over and the prop hit the ground staying a few | > seconds locked with 1/2 throttle. When I finally releases the prop, [quoted text clipped - 3 lines] | Yes, if you don'=t mind the extra half ounce, the extra $10 and the | extra 5% power loss.... You're exaggerating quite a bit here ... It could be built into the ESC -- an extra chip that cuts the throttle off if the ESC gets too hot or too much current goes through it. There's a few ways they could do this that wouldn't increase the resistance (i.e. reduce power) at all. It would probably only require a single chip, so the added weight would be much less than one gram, let alone half an ounce. I doubt it would add $10 to the cost to manufacture, but they might jack up the price by $10 for the extra feature. The other option is to add a fuse. An automotive mini blade fuse weighs about one gram (I just measured it) and the resistance added is miniscule (I couldn't even measure it when I tried.) The cost was about 40 cents if I remember right. Somebody else suggested just cutting power when your prop is about to hit the ground -- which is a good idea, electric or glow. But it's not the complete answer. First, you can just plain forget. And if your plane starts getting hit with interference and crashes, the motor may try and start up without you even moving the stick. Or if you forget to turn off your plane before the transmitter, it might start up as soon as you turn off the transmitter. And I had an ESC catch fire for some unknown reason right after hand launch -- obviously a fuse wouldn't have stopped whatever the problem was, but it might have saved the ESC well enough for me to figure out what the hell went wrong. Instead, I got to send a melted hunk of ESC to Astroflight and they replaced it for $60 or so. That, and it messed up my plane somewhat. If you ask me, park fliers and ESCs should come from the factory with a fuse already installed inline with the motor or battery. Something large -- like for a 10 amp ESC, a 20 amp fuse, so there's no danger of it blowing during normal use. If somebody wants to remove/bypass the fuse, they certainly can, but they should know the risks first. | > It was a Great planes c-5 nano spc, hoocked to a 600mah, 7.2V batt. SignatureDoug McLaren, dougmc@frenzy.com Geek used to be a four letter word. Now it's a six-figure one. thanks for the replies. I think I have to put in mind that throttle needs to be cut off. In gas, when the prop hits the floor it stops the engine right away and you never have to bother with it. I was taxing when it flipped over, wasnt flying, thus I didnt cut the throttle. Now I learned my lesson. Thanks and have a good time Electric rocks!!!!!! so quiet, so clean....and yes, underpowered... so what? :-) | Thanks and have a good time | Electric rocks!!!!!! so quiet, so clean....and yes, underpowered... so | what? :-) Not always underpowered. You can certainly have an electric that will go straight up and keep going straight up until it's out of sight. It'll just cost a bit more -- and not always that much more. SignatureDoug McLaren, dougmc@frenzy.com You can tune a piano, but you can't tuna fish. You can tune a filesystem, but you can't tuna fish. -- from the tunefs(8) man page dougmc@frenzy.com (Doug McLaren) wrote in news:yzvOc.18589$Gk4.16490 @fe1.texas.rr.com: >| Thanks and have a good time >| Electric rocks!!!!!! so quiet, so clean....and yes, underpowered... so [quoted text clipped - 3 lines] > go straight up and keep going straight up until it's out of sight. > It'll just cost a bit more -- and not always that much more. My take is that the relative cost depends on the size. At the small end, electrics are actually cheaper than their glow equivalents, all things considered. Unfortunately, while big glow engines don't cost much more than little glow engines (frex, an OS .65LA costs about twice as much as a .10LA, with >6 times the power), this is NOT the case for electrics, especially when you throw in the battery costs. To do a more-or-less fair comparison, I'm including the Motor, ESC, and battery for the electric vs. the engine, tank, throttle servo, and receiver battery. At the low end . . . you can have a lot of fun with a $19 GWS RXC motor - I get about 4 oz thrust, and it's not difficult to build a plane for it that's <6 oz ready to fly. Throw in a $20 ESC and a $25 2 cell LiPo for a total of $64 of stuff. My geared 350 cost about the same and probably has more thrust than my glow .061. For a glow, it's hard to get a decent throttled engine for under $40, and you'd want some kind of small servo for the throttle - say at least $15 (I use metal-geared HS81s or equivalent, but they cost a bit more), and $15 for the receiver pack and $3 for the tank, and you're up to $73. Now, it's hard for me to get too excited about a $9 savings, but - trust me on this one - the electric motor will be MUCH easier to start. And it'll have fewer pieces to install (no tank, no fuel lines, no throttle line!). And less likely to cut just after takeoff. And you won't have to screw around with the #$&%$^ clunk tube being too stiff so that the clunk doesn't actually clunk, and - ahem. Okay, I may have some issues with <.15 sized glow engines. On the high end, though . . . you can get a TT .61 for $100, throw in a $10 throttle servo, $20 Rx pack, $5 tank and you're up to $135. I doubt that you can get anywhere near that kind of performance from an electric system for under $300, and I suspect it'll be more than $400. And I *can* get excited by $200+. So below .15, I fly electric. At .25 and up, I fly glow. In between, I agonize and grumble and finally build something either bigger or smaller. sheesh, when did I get so wordy? Signature"Be assured that a walk through the ocean of most souls would scarcely get your feet wet." - Deteriorata It tends to start evening out on the high side, NOT including the batteries. The biggest AXI outrunner & controller prices out in the middle of 1.20 4 Strokes. It's weird to see aircraft that big flying with just prop noise.... PCPhill And yes, I know (believe me, I Know!) the batteries cost more than the motor. "Mark Miller" <dasmillr@pacbell.net> wrote in message > My take is that the relative cost depends on the size. At the small end, > electrics are actually cheaper than their glow equivalents, all things > considered. Unfortunately, while big glow engines don't cost much more [quoted text clipped - 32 lines] > > sheesh, when did I get so wordy? > thanks for the replies. I think I have to put in mind that throttle > needs to be cut off. In gas, when the prop hits the floor it stops the [quoted text clipped - 5 lines] > Electric rocks!!!!!! so quiet, so clean....and yes, underpowered... so > what? :-) Mine aren't. LIPO cells young man. |
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