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Old Jul 14, 2006, 01:38 PM
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Joined Jul 2006
2 Posts
Help!
Blade CX Flight times

Hello all.

First off, let me say, these forums are great. After looking through several threads I've found plenty of different modifications I'm excited to make to my Blade CX; however, I have a rather significant problem I need to fix first: flight times.

I've been having this problem with my BCX for several months now, and after no success with trying to solve it myself or with help from tech support or my LHS, I'm hoping you guys can help. To put it simply, my BCX will not fly constantly for any significant length of time. At most, I can get about a 2 min flight when hovering above the ground. More often, it's around 1 min. During this period I have to slowly increase power just to keep it in a hover at the same height. After 1 or 2 min, with the motors running at full power, the power drops dramatically and the BCX drops quilcky and ends up resting on the ground (its got enough power that I can still move the BCX across the ground, but it doesnt lose contact (think hovercraft here)).

Now, the things I've tried:
I tried moving the throttle trim up to full after plugging in the battery and allowing the 4-in-1 to set (didn't seem likely to be the problem, but I was told by the tech support guy to try this): No noticable effect.
The numbers on both the upper and lower blades both match, though I really doubt that could have the severe effect I'm seeing here.
Next I bought a new battery (I figured I would want a second one anyway, even if this didn't fix it): Once again, this didn't make any difference.
I tried checking to see if the inner or outer shafts were binding against anything, but they move freely (I even wiped them down with a little WD40 when i re-assembled it after I did this).
When I took the heli apart to check this the other day the possibility of binding shafts, I also checked my swashplate. Didn't seem to be coming apart at all, nothing unexpected with the piece.
As sort of a last resort, I even replaced my 4-in-1 with a brand new one the other day. Still no change.

The only things I can think of are:
1. The problem is my charger, not the batteries themselves. I don't, however, have access to another charger, and I'm not too excited about the prospect of buying yet another replacement peice when I don't know if that is the problem.
2. The motors are bad. Once again, I see the same problems as with the charger possibility... no other BCX to try my batteries on, and I don't want to unnecessarily spend any more money replacing pieces that aren't broken.

If anyone has had this problem and fixed it, or has any other suggestions (including how I might check the above without spending $25 on replacement pieces), any help would be greatly appreciated (I'm hoping to have it running well by the time I go on vacation in a week or so).

Thanks in advance,
-Ben
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Old Jul 14, 2006, 02:35 PM
Just call me crash.
Joined Jan 2006
1,308 Posts
Welcome aboard soccerben, first thing you need to do is verify that your packs are indeed peaking. It could be the charger, or less obvious, the charging source. My chargers are fine, but I discovered it was my charging source that was the problem, I was charging it off a 7 amp SLA (nitro starter box battery) and even though the charger said it was charged, apparently it wasn't. As soon as I began attaching the charger to a 15 amp power supply the problem went away.

To tell if you're getting peak, you need a digital voltmeter. On the charging jack you can see visible strips on the bottom/side where you can access them for testing. Put one probe on the CENTER post, then the other probe on each of the two OUTER posts. This taps each cell. When charged, each cell should read ABOUT 4.15 to 4.2 (rarely) volts per cell, and should be within .01 volt of each other. If they are more than .01 volts apart, there is an imbalance issue that may become a problem (but not responsible for this.)

When discharged, they should be around 3.7 volts per cell, in any case not less than 3.5 volts per cell, this is deadly for a lipo. Which brings us to possible cause.

How far down are you discharging the packs? If you run it till it won't turn to rotors, this will kill a pack and quick. Once cell begins to drain farther than the other and begins to die, then on next charge one will charge and the other won't, eventually the pack dies (or blows up. ) If you keep it at around 3.7 VPC at the end of a run, the cells will stay in very close balance and you'll have long life from them.

A good indicator of this, if it won't climb on it's own, it's time to bring it in. This consistently leaves my cells at 3.73, 3.75, somewhere in there, and always closely balanced.

So start with metering your packs, if they check out there are some other things to look at, like you said motors, or something is binding or too tight, or you have a high electrical resistance somewhere that's heating things up.
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Old Jul 14, 2006, 07:30 PM
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Columbia Regional, Missouri, United States
Joined Dec 2002
726 Posts
No----no----never



WD STANDS FOR WATER DISPLACEMENT....It turns into a STICKY goo the militery calls COSMOLINE. It is designed for LONG turm protection on weapons for storage. It is NOT a lubricant! It was never intended as one! Toss the damn thing in the dumpster....Use a very lite OIL. I use a 0 W synthetic MOBILE 1 left over from my car.

I'll get of my box.........
PHIL I.
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Old Jul 14, 2006, 08:16 PM
Just call me crash.
Joined Jan 2006
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Quote:
Originally Posted by phil I.
It is designed for LONG turm protection on weapons for storage.
Say . . . . WHAAAAT?

Quote:
In 1953, a fledgling company called Rocket Chemical Company and its staff of three set out to create a line of rust-prevention solvents and degreasers for use in the aerospace industry . . . Convair, an aerospace contractor, first used WD-40 to protect the outer skin of the Atlas Missile from rust and corrosion.


A little WD-40 never hurt nuttin' . . . unless you use it for After Run Oil on your nitros, now there's a big no-no, I don't give a hoot what Traxxas says.
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Old Jul 14, 2006, 09:32 PM
cjg
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Vermillion, SD
Joined Jan 2006
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wd40 will also soften some plastics. It makes rubber soft and turn to goo. It isn't a good lubricant as it "disappears", it is a cleaner/rust protector.

Plastic compatible oil such as mobile synthetic is a good choice.
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Old Jul 14, 2006, 10:56 PM
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Joined Jun 2006
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Ben, from what you have said I would bet money it is directly related to the battery pack not being fully charged. The odds of two motors being bad is unfathomable. If you had one bad motor your heli would be spinning like a Chihuahua on crack. So the next step is to figure out if... A. Is the charger bad or B. Did you get two bum packs in a row? A $10.00 analog multimeter from Sears would give you the answer.

rocknbil brings up a very good point. If your battery pack is dead and you keep trying to fly it you will end up with a battery pack that will not recharge. My best advice for having a long term healthy battery is to put the heli on the ground before the heli needs full power to hover. If the battery does not have enough power to lift off and you continue to spin the rotors then you are taking a chance at making a good pack all wack.
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Old Jul 15, 2006, 10:45 AM
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Joined Jun 2006
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You are using the right type of battery right? 7.4V 800mAh 2-Cell LiPo and not some nasteh nicad/nimh thing
Id be tempted to think it was the charger myself, and replace it. buy an esky charger like this one theyre real basic but good enough. Been using one on my honeybee cp2 for over 13 months now and its still charging with no probs.
cheap n cheerful for about 10 dollars?.
Swappping the 4in1 was a bit extreme though lol, ahh well least youve got a spare

good luck with yer quest


~SKULL~
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Old Jul 15, 2006, 12:21 PM
Just call me crash.
Joined Jan 2006
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Quote:
Originally Posted by stersman
...A $10.00 analog multimeter from Sears would give you the answer......
Welcome aboard stersman! An analog meter is pretty much worthless for lipos though, you have to be able to tell if the cells are within .01 volts of each other, and you won't be able to accurately tell on an analog meter. Digitals are pretty cheap too.
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Old Jul 15, 2006, 12:54 PM
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Thank you for the replies.

The batteries seem fine. I have one on the charger atm, but the other is reading 4.07 on one cell and 4.08 on the other (this is after i flew with it for 1 min and the heli came back down... I cut the power and measured the voltage on the battery).

Also, after talking to the owner of my LHS (he was in town yesterday as he lives about 45 mins away from here) he said he was having this same problem with his a while ago. He suggested I replace my motors and put a heat sin k on the new ones. I did this. Once again, it made absolutely no difference.

rocknbill u suggested that it might be a high electrical resistance somewhere. Any suggestions of how I might check this, aside from simply replacing all remaining electrical peices (though the servo is the only thing remaining I think)?

As for the WD40, thanks for the advice. I know it has a tendency to eat some plastics, so I used very very little of it. I'll look for a little oil that'll work with plastic here in a bit, give that a try (though it certainly doesnt seem to be binding to me).
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Old Jul 15, 2006, 01:56 PM
Just call me crash.
Joined Jan 2006
1,308 Posts
Man . . . I don't know, especially since you swapped out the 4-in-1. The only thing I can think of is the charging source, what are you using, the stock wall-wart? I was getting good voltage readings too, just 30 second to 1 minute run times. Power supplies are hard to come by (financially) but I do lots of other RC and had one already, maybe you can get the LHS to charge up a pack attaching your balance charger to a DC power supply or even a lipo charger, at this point it's worth a shot.

Another "wild hair" is maybe one of your servos is going bad, it could be putting too much draw on the pack? The way to test this could be kinda dumb but it might tell you, put a weight through the skids, disconnect the servos, and spin it up, see how long it runs.
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Old Jul 15, 2006, 02:53 PM
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Do not rule out the battery yet. Good voltages on a battery do not directly relate to storage capacity. If your voltage reading is bad during testing then it is easy to tell if your battery is bad. However, it is possible to have good voltage reading and minimal storage capacity. A car battery for example can read the full 12.X volts on a meter. This does not mean the battery has enough storage capacity to start a car. I'm not saying your battery is the issue, it is just my best guess. I was also wondering what altitude you are at. I have done serveral flights at 4500 feet above sea level and was able to get around 7 minutes or more of run time. So unless you live at the top of Mt. Mckinnley we can probably rule out altitude. You have said you motors are not binding either?

But letís assume your battery is healthy. 800 mAh is a lot of energy too discharge. So say if you did have some sort of electrical anomaly happening that energy loss would have to be changed into heat if itís not being drained by the motors spinning. Energy does not magically disappear. If it is happening over a very short period of time and you are draining most of the battery pack than you are going to have something extremely hot on your heli. If a servo could find a way to drain your battery pack in a couple of minutes I guarantee you in would turn into a pile of goo. Don't take this the wrong way. I am not saying you do not have some type of electrical wackiness going on. But if you did it should be very obvious.

So after your next flight if you are only able to get a couple of minutes of run time then check for heat, lots of heat. If you do not find anything abnormal you can conclude that your heli is not draining the energy because the energy was never there to be drained.
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Old Jul 15, 2006, 05:57 PM
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Joined Nov 2005
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Quote:
Originally Posted by soccerben86
Hello all.
...
I've been having this problem with my BCX for several months now, and after no success with trying to solve it myself or with help from tech support or my LHS, I'm hoping you guys can help. To put it simply, my BCX will not fly constantly for any significant length of time. At most, I can get about a 2 min flight when hovering above the ground. More often, it's around 1 min. During this period I have to slowly increase power just to keep it in a hover at the same height. After 1 or 2 min, with the motors running at full power, the power drops dramatically and the BCX drops quilcky and ends up resting on the ground (its got enough power that I can still move the BCX across the ground, but it doesnt lose contact (think hovercraft here)).
...
Your problems may not have started with the LiPo but it's a pretty safe bet it's trashed by now. If you keep running the BCX past when it takes a large throttle increment to climb while hovering OUT of ground effect, you will damage the LiPo. The resting voltage might look ok but its voltage under load will drop way too low to be useable.

Stop flying the BCX when the red light on the 4 in 1 comes on with fairly small throttle increase while flying out of ground effect. If you fly until it will only hover in ground effect you will damage your LiPo and severely reduce the number of useful cycles. If you fly until it won't lift off at all, you'll be buying a new LiPo every few flights.

Mike
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Old Jul 15, 2006, 07:29 PM
TB47 flyer
South Petherton, Somerset UK
Joined Apr 2006
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I had the same problem with a twister bell 47

I had the same problem as soccerben86 it turned out to be a bad charger that killed the lipo

I took the charger back to the shop they changed it I bought a new lipo and now get 10-15 minutes flight per charge.
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