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Old Feb 09, 2010, 05:31 PM
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New Jersey
Joined Feb 2003
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Nah me neither. Never had a BEC die, but lots of motors and escs fry.

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Originally Posted by rcnewb View Post
Can't argue that, though I've never had an external BEC die on me, in fact I've never even had one become remotely warm or show the slightest signs of stress during flight, but any component can give out at any time. The circuitry within a BEC is quite simple, which makes it harder to screw them up from a manufacturing standpoint. A built-in BEC (that is part of the ESC) is more prone to failure because it's crammed in there and can't dissipate heat as effectively.

The same is true for servos, if one dies/strips out, game over for the heli.
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Old Feb 09, 2010, 07:19 PM
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Park City, UT
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rcnewb, the UBEC you are using is only rated up to 5S - 23V in the specs but as I recall you are using 6S. Are you using it on 6S? I have a few of these in my planes but have been reluctant to use them on 6S.

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Originally Posted by rcnewb View Post
It's best to use an external switching BEC on a heli. A 3A-5A switching BEC is fine for a 500-sized heli, check out the HobbyKing Turnigy 3A-5A switching UBEC's (this is what I use on my 500GT), they'll only set you back $7.
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Old Feb 09, 2010, 07:41 PM
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tribum - I'm using the Turnigy 3A-5a UBEC on 6S with no issues whatsoever, I'm not sure when they changed the rating to 5S, but that same BEC was formerly advertised to handle up to 6S. After a 7-8 minute flight, the UBEC is always cool to the touch, it has never been even remotely warm.

However, if you check back a few pages and look at some of my power graphs that I posted earlier on, as soon as the motor spins up and load is placed on the power system, the battery pack voltage drops to 22-23V (and gradually drops down from there), which stays within operating range of this Turnigy 3A-5A UBEC. I bought one of these (Turnigy 7.5A UBEC, rated to 10S LiPo) at the same time I bought my 500GT kit, but read somewhere within the EXI 500 thread that it was overkill and that the 5A Turnigy UBEC was more than adequate for 5S or 6S setups. Frankly, I think the 5S rating is a mistake on the product page.
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Old Feb 09, 2010, 07:44 PM
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I am using that BEC on my heli as well as on several EDF's on 6s. I never noticed the 5s limitation until you just pointed it out. I have never had an issue. Maybe I have been lucky.

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Originally Posted by tribum View Post
rcnewb, the UBEC you are using is only rated up to 5S - 23V in the specs but as I recall you are using 6S. Are you using it on 6S? I have a few of these in my planes but have been reluctant to use them on 6S.
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Old Feb 09, 2010, 07:52 PM
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United States, CA, Hemet
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Rcnewb what pinion gear would you run with a 5S pack on the 1800KV HK Typhoon motor?
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Old Feb 09, 2010, 08:23 PM
Gone Flying.
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Western NY
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kc -

From what I've read, I think many are using 13-14T pinions on 5S. As per the dark horse calculator, 13T will give you a max head speed of nearly 2700 RPMs on an 1800Kv motor, that's plenty of RPMs. 14T will put you up near 2800, assuming the motor is 90% efficient. On less efficient motors (I'd put Turnigy in that category), 14T might be a good choice as well.
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Old Feb 09, 2010, 08:46 PM
Martin - AKA mr.sneezy
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Adelaide, Australia
Joined May 2004
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Re internal BECs....

I've not been so lucky. In my early 450 flights I had two in air RX shutdowns from the internal BEC overheating. Twice, because the first time I thought I'd just pulled the auto lever by mistake or something. The second time I suss'ed it out properly.
The shutdowns both happened on a hot summers day, it had been fine during winter time...
I now use a UBEC in both heli's and my six servo glider.

Also, by coincidence I went for a swim to retrieve a friends model from the ocean two weekends ago, when that model (an e-slope soarer) had an ESC burn up and overheat the internal BEC chip (due to a motor upgrade).

It was a nice day for a swim at least :-)
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Old Feb 09, 2010, 08:52 PM
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New Jersey
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I was actually referring to external BEC's. That's how we got started on this topic because someone asked why we use external BECs since the ESC's have them built in. I use an extrernal BEC or a small rx battery for anything over 3s.

Brian

Quote:
Originally Posted by PLMS View Post
I've not been so lucky. In my early 450 flights I had two in air RX shutdowns from the internal BEC overheating. Twice, because the first time I thought I'd just pulled the auto lever by mistake or something. The second time I suss'ed it out properly.
The shutdowns both happened on a hot summers day, it had been fine during winter time...
I now use a UBEC in both heli's and my six servo glider.

Also, by coincidence I went for a swim to retrieve a friends model from the ocean two weekends ago, when that model (an e-slope soarer) had an ESC burn up and overheat the internal BEC chip (due to a motor upgrade).

It was a nice day for a swim at least :-)
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Old Feb 09, 2010, 09:09 PM
Gone Flying.
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Western NY
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Scroll back a few posts and read the one I posted earlier regarding BEC's, PLMS - what you're saying is absolutely correct, on-board ESC BECs are more failure-prone, namely due to poor heat dissipation, based on the fact that the BEC is "mashed" onto the ESC. External BECs are installed separately, and soldered to the ESC battery connector, then the red wire is pulled from the ESC Rx connector so that the ESC is no longer providing power to the Rx, it's more or less an electrical bypass system.

External BEC failures are rare; in fact, of the dozens of guys I fly with who adamantly use external switching BECs, I have yet to hear of one single failure. As for internal BEC failures, I've experienced two of them myself in the past year, and I was using 3S LiPo packs and only 2 servos, I think the internal BECs fried because of the high current draw through the ESC as both planes were speedy (100mph+).
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Old Feb 09, 2010, 11:32 PM
Team Wack-a-Mole
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Maryland
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Looks like Xheli is gonna have some cheap CF 500 heli blades now:
Look at the 2nd row $16.70 for blades
New stuff at Xheli
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Old Feb 10, 2010, 12:23 AM
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Quote:
Originally Posted by kctrading View Post
Rcnewb what pinion gear would you run with a 5S pack on the 1800KV HK Typhoon motor?

I use 1800KV HK Typhoon motor stock pinion 13 and 2 X 2200 11.2 volt.
The power is too much.In idle mode the head will have problem.
I think 5 s is better.
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Old Feb 10, 2010, 12:54 AM
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United States, TN, White House
Joined Oct 2008
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Hello all, Im putting together the 500 gt right now. I just got it a few days ago. I went threw alot of the 1-20 pages of posts. Does anyone know if HK fixed the tail problem on this? Or do I need to change my tail also? TY

Rob E
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Old Feb 10, 2010, 03:34 AM
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England/uk
Joined Oct 2007
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hk 500gt

Rob ,
Hello if you are refering to the thrust races being fitted yes,both the kits that i have received in the last month have this upgrade,
cheers Euan.
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Old Feb 10, 2010, 06:02 AM
Gone Flying.
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Western NY
Joined Nov 2006
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Quote:
Originally Posted by Melnic View Post
Looks like Xheli is gonna have some cheap CF 500 heli blades now:
Look at the 2nd row $16.70 for blades
New stuff at Xheli
Mel -

That's a great price for carbon fiber blades for a 500, they're also selling c/f blades for the 450 at $9.70 each, another great deal. I'll definitely order replacement blades from them in future crashes...
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Old Feb 10, 2010, 12:08 PM
Lloyd Robinson
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USA, MO, St Louis
Joined Jun 2007
777 Posts
Not bad but still not as cheap as these: http://www.hobbycity.com/hobbycity/s...dproduct=10696
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