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I found out electrics are very expensive!

Old 11-03-2008, 12:52 AM
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1fishnfool
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Default I found out electrics are very expensive!

I finally tried to get serious about electrics,and did in about 600.00 worth of stuff today.First off,I will tell you the setup.They were both identical power systems.There was 3200kv brusless,like speed 400 size,just about 1-1/2 time the lenght,bought from hong kong,both had castle 25amp speed controls,and 2200mah 25c 11.1 lipo batteries,running 4.75x4.75 apc speed 400 props.Both had spektrum radio with ar6100 recievers.First plane is,or was a graupner mini viper,and the second was a swallow400s pylon racer from hong kong.I had flown the graupner probably 30 times with the same speed control and battery combo,just with a cobalt 400.It hauled butt,except the cobalt burned up,so I stuck the brushless in it.I launched it,and it climbed out as fast as you could see it,so I cut the throttle to trim it,and got it flying straight,so I brought it down to do a hot lap at about 3/4 throttle.As soon as I did 100% throttle the motor just cut off....I backed off the throttle and gunned it and it took off again and then cut off again.I figured maybe it was drawing too many amps,but I am kinda retarded when it comes to electrics.Anyways,I was just running about 3/4,which was probably easily 110 to 125 mph,when the plane went hard right aileron,hit a power line with the wing,and hit right in the middle of the road.The wing was fine,but the brand new,1st flight battery was smashed were it hit the motor on impact.The motor exited the plane,and after about a half hour,was found,but trashed.The case and shaft were bent too badly.Oh,and it was the first flight on the motor too.Come to find out,the aileron servo had stripped.It was a hitech hs81.I guess it was too much force with the new motor.Oh yea,the speed control was still hooked up when we saw the plane,and it was actually on fire,with flame.Total loss was the battery,Motor,Reciever,2 servos,and the plane is in pieces...it was one of my favorites.Ok,so back on the horse.Second plane was the swallow 400s pylon with same motor and battery setup.First launch did the same as first plane,a couple seconds after launch,motor shut off.Can someone explain this?Is it too many amps?Anyways,I ran it about 3/4 throttle on the ground,and it kept running,so me wanting to fly it,we launched it.Same story,got it trimmed,and decided to bring it in for a hot pass.Motor shuts off,I glide around,throttle back up,and it takes off screaming,but I cut it to about 3/4.All of a sudden,plane goes into a perfect,straight dive towards ground.I cut thrtottle,no elevator at all.Plane hit ground,total loss.Fiberglass fuse trashed,motor smashed,and also battery smashed due to impact with motor,and motor to ground.For some reason,radio works fine,except the elevator channell of ar6100 reciever.Once again,I just took the reciever out of the pack this morning to bind it...brand new stuff,not junk.Bad loss for the day,and I think electric is not in my future.I fly c/l combat,and it just seems so much easier to put on a fora .15 and scream around with it...too bad,because I have 3 more of the same exact swallow 400 pylon racer,and I was going to build all of them to have a little fleet.My question is,does anyone know if the setup of the 25 amp castle speed control,and the motor and battery was too light,or if the second plane got a fried reciver from too much voltage?I am kinda dumb on electrics.
Old 11-04-2008, 10:14 PM
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Matt Kirsch
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Default RE: I found out electrics are very expensive!

A good friend of mine always says that every plane has a number on it... I had one whose number was "3" last summer, and another that was "1." It's a real bummer but as good an excuse as any to buy a new plane

As for what went wrong... That's tough to say. I expect that your problems with the motor cutting out is that you were drawing more Amps than the battery could handle. ESCs have a low voltage cutoff built in to protect the battery and ensure that you have power to run the controls to land the airplane. 3/4 throttle kept the Amps down enough that the battery could handle the load.

The HS81 servo has a "glass jaw" unfortunately. I had many of them in R/C combat planes and have many partial packets of HS81 gears on my parts rack from repairing them. You probably got a little aileron flutter while going so fast, which vibrated the servo and caused a tooth failure. Flutter is a bad thing which is generally caused by excessive speed, improperly sealed hinge gaps, and the tiniest bit of slop in the linkage. The aileron literally flutters up and down at almost vibratory speeds, and you'll hear a buzzing noise on larger planes.
Old 11-06-2008, 04:32 PM
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rmenke
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Default RE: I found out electrics are very expensive!

fishfool:

Welcome to "I should have known? Seems sort of like your first flight on a new bird and the engine quits just after takeoff. You learn to bench breakin the engines and get them well tuned before flying. I killed 4 to 5 new airplanes before I got good enough to takeoff and land. What, don't need no GD insdtructor, after all, I'm a private pilot and fly military jets in the real world, what could be hard about models. Most high hour pilots make this error before they see the real world.

Ok, to your problem. Sounds like your controller is undersized for your application, but you don't know. Well, if you were my kid, it would be spanking time. Why didn't you know? I suspect you don't have a watt meeter so you did not bench test your equipment before flight? You jumped right in there with the high performance stuff where there is very little room for equipment error. How about a good cheepie foamy like a Airfoilz edge 540, and get some good experience and education under your belt before trying to go fast of a budget? Going fast costs a lot of money in almost every form, all the more reason to get it right the first time.

We are very fortunate to have quite a few experts out there in the RCU world who enjoys passing on their hard learned knowledge to us less educated types. I don't claim to be one!!! Start reading as much as you can about this electric stuff. Some of the guys spend their professional life testing batteries or motors or whatever, and have years of real life experience they are willing to and do pass on to us for free yet. Read in Red Schoefields "Battery Clinic" and others as you learn who is who in electrics. Find out who makes the best batteries, controllers, motors for the buck. There is some decent cheep equipment out there that will supprise you, very sutiable for normal flying. But, you gotta go fast, so be prepaired to spend a buck. Wanta race Q-500, and start out with MVVS and OS engines rather than Nellson or Jett. Yep, your dead before you start. First thing of first things, buy a decent watt meeter and learn how to use it. You will be able to ground test motors, controllers, batteries and props. Supprise, supprise, one pitch up in a prop may exceed your equipment limits, and its poof time. Give yourself some wiggle room with controllers, if the motor max says 25 amps, use a 30-35 amp unit. At least the motor will quit before your controller or battery and you have some chance of saving the airplane! Good luck!!

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