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Bb #9
I threw together a BB today while visiting my Fool of a friend here in Florida. This one is my second BBAP1 and my ninth BB total. Power is from a Chinese A22-15M. I didn't quite get to finish it to flyable condition due to some missing gear. We're going home tomorrow so I'm leaving the tailfeather linkages and LG for The Fool to finish. We glide tested it by chucking it around the front yard. With everything but the LG and battery on the plane the CG is right at the aft limit. He should stay spot on if his LG doesn't end up weighing more than a couple of ounces. He has a Dart and we buddy boxed a 4-channel plane today so I don't think he'll have too much trouble with the maiden.
kendall |
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I had planed to leave the diminutive BB off my list but this is the last straw. If you guys are going to keep making these things sound this good then I guess I am just going to have to add one to my build list. Nice build Don. I am kind of surprised that you are running that much battery in it but then again I have to admit that I haven't payed that much attention to what others are running. Can't argue with those flight times. Man you could fly one all day with just a couple of batteries. OK I now have around 8 planes on my foam building list and we are coming into Balsa building season. Oh well I guess the wood can wait. Rob... |
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Hey guys, I've just finished my BB and it flies like a dream except for some minor issues.
My motor will cut out at around 65% throttle, and I can't figure out why. I'm running a TowerPro 2408-21t-3A motor with a TowerPro 18A ESC on a 3S 1000mAh 10C lipo battery. I suspect that perhaps i need a bigger battery (higher C rating) for this motor, but before i buy new batteries i would like to hear your opinions. If the motor cuts out, reducing throttle to 0% and throttling back up will start the motor just fine, up until the 65% or so when it cuts out. The good news is, it flies fine on 50% throttle, level flight around 40% or so. Super neat little plane. But i tend to forget my motor issues sometimes, and that might put me in a tight spot at the worst time. Any thoughts on this? |
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hope this helps |
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It's a Towerpro "Mag8" digital ESC 18A. It was part of the combo from unitedhobbies
https://www.unitedhobbies.com/UNITED...3.8_Prop_Combo I'm running an 8x4 prop instead of the one that they sent with it, if that makes any difference. |
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Visagio, you will have to use the "beeps" and the throttle stick to program this TowerPro ESC. There are other models that can use a programming card, but not this one.
As for your problem, you definately needs new batteries as your batteries can only supply 10A max. The voltage will probably drop quite a lot. I think you are drawing more than the 10A with your motor/prop combination. The motor is rated for 13A. Also, your batts may not even be able to supply 10A without a very significant voltage drop, hence the esc cutting-off your motor. Buy 20C (or better) batteries, 1200mAh or so would be better. Or even 1000mAH 20C would be better than what you have. The rule, if you want a long life for your lipo, is not to draw more than 75% of the rated continuous current of your batteries. Otherwise, it will get very hot and puff relatively soon. Say, if you have a motor/prop combo that draws 15A, then your batteries must be able to supply 20A continuous (not peak!). Likewise, if you have a 1000mAH 20/30C batts, it means you can draw continuously at 20A and peak at 30A. So, to be safe and not have the voltage drop too much, your motor/prop combo should draw less than 15A or at most 20A at WOT. You should not think about going to 30A at wot, otherwise, your batts won't last very long: they will die an early death. chewy |
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Last edited by chewytm; Nov 04, 2008 at 12:40 PM.
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Visaggio: I have the mag8 escs and they are pretty easy to program, unlike an ele that takes up to 16 beeps! counting, counting.....
The other thought that came to mind is whether your battery is fully charged. I've had instances when I either quit charging as I had to leave it unattended, or put in an already partially discharged pack and the motor stalls as the voltage drops. If the 8x4 prop is larger/higher pitch than recommended/supplied then it will drop voltage even faster. So if you know your battery is fully charged, and you use the smaller prop, and can run full throttle, you know it needs a higher capacity battery. |
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In case you don't have it here is a data sheet on the Mag8. Let me know if you figure things out. I followed the instructions with mixed results. It's programmed to the point that it pulls the plane and seems to work OK but I'm not sure it's right. I got the instruction sheet at Greyson Hobbies' site. Do you have any idea what the timing setting should be for the B21??? I think probably 2%. Just a hunch Steve. |
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I went to the local hobby shop and got a new battery. It's a 1600mAh 15C liipo and it solved the issue. I can go full throttle no problem. Although if i go full throttle in flight i think it would rip the wings off.
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Last edited by Visaggio; Nov 04, 2008 at 08:16 PM.
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Vis,
Just a few days back I had the exact same issue for my BB42 & Mag8. https://www.rcgroups.com/forums/show...4#post10855629 I thought I was able to program mag8 for 2S Lipo - but it didnt store the setting in memory so I have to program it every time after I take out the batt Anyway since the default is 3S Lipo - the easier solution would be to just buy a 3S batt & that is what I am planning to do. Read up on that thread - some expert comments are there - may help in future. RcTrooper |
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kendall |
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