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Old Apr 11, 2012, 09:11 PM
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Didn't I read somewhere that the CC Bec is affected by high temperature, not a single instance but cumulative.

If that is the case, then our packed fuses, amount we leave the plane in the sun through the day and even fuse color would make a difference.

My Aspire has a CC Bec for a little more than 2 years now, at that time LiFe packs were not widely used so I installed a LiPo and adjusted the CC to 6V. This bec came from a Supra so it is probably pushing 3 year without problems on a yellow fuse...so far

G
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Old Apr 11, 2012, 09:21 PM
PLD
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Elevated interior temps certainly can be a big factor if you're starting out with an ambient of 50'C, that cuts a lot of the usable envelope away.
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Old Apr 11, 2012, 10:53 PM
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In Norway and Denmark where the FS4 went down temperature is not and issue
This time of year.
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Old Apr 11, 2012, 11:13 PM
PLD
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Aaah to have deliciously cool weather Here in rural Australia it's something we're constantly fighting with, both in planes and consumer goods.
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Old Apr 12, 2012, 12:36 AM
Some people call me Maurice
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Guys, the CCBEC is inherently slow and not well suited for F3X with fast servos like MKS. It can handle huge current surges and high temperatures and low batteries and all kinds of stuff, but not fast transients. This is largely a limitation of switching regulators, not the CCBEC in particular.

Regulators are a feedback loop system. They work by feeding raw battery voltage right thru to your servos, but rapidly switching on/off so that the average voltage is lowered. They monitor the output voltage and adjust the on/off ratio as needed just as a motor controller provides throttle control. Like any other feedback loop system there is a balance between stability and responsiveness and there is a hard limit to the minimum reaction time. Adding reasonably sized capacitors will not help these regulators as they mostly add a phase delay and can potentially overload the regulator on startup.

The solution is linear regulators which have exactly the same efficiency and heat as switchers when making small reductions like 6.6V -> 5.5V. Linear regulators are just dumb resistors that vary their resistance with current dumping excess voltage by getting hot. There's no switching frequency or digital feedback loop so their response is extremely fast. The drawback is that they will overheat with large continuous currents or high input/output voltage ratios.
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Old Apr 12, 2012, 09:54 AM
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Is it possible that the jam nut on the elev. clevis interfered with the rudder
servo body or arm causing some of your problems? Just a thought and probably
a long shot.

Ron
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Old Apr 12, 2012, 11:11 AM
Ricky Windsock
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Quote:
Originally Posted by Kiesling View Post
Gordon,

I suggest getting rid of the regulator and using a 4 cell pack. With proper maintenance and care, I've had reasonable luck with the Elite 1500's using both JR/Spectrum and Airtronics 2.4 systems. Unregulated 5 cell packs are too much for the MKS servos. The MKS servos work fine with the 4 cell pack - plenty fast and plenty strong.

While I like LiFe packs a lot, for me, the issues with NiMh don't outweight the learning curve and concerns I have associated with regulators.

It sounds like the problem you had was very repeatable. As a matter of curiosity, you could try recreating the problem by loading up the surfaces by hand and see if you can see the same failure (you will probably need a helper to do this).

FWIW
Tom
Thanks Tom,
I have purchased two 4 cell Elite 1500 packs this morning and will start using them from now on as you suggested. I hate having to give up on the LiFe packs but it's best to eliminate the worry by reducing the risk factor. (Nothing worse for TD skills then having your mind occupied by fear of system failure at any point.)
I haven't the time to experiment with regs or the money to lose another bird.
Thanks for all the suggestions etc guys.
Gordon
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Old Apr 12, 2012, 11:13 AM
Ricky Windsock
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Quote:
Originally Posted by Ronald Mong View Post
Is it possible that the jam nut on the elev. clevis interfered with the rudder
servo body or arm causing some of your problems? Just a thought and probably
a long shot.

Ron
Moving the elev clevis to the inside elev horn hole brought the nut very near to the body of the rudder horn. They are close Ron but don't actually touch. That wasn't an issue.
Thanks anyway.
Gordon
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Old Apr 12, 2012, 12:27 PM
Sink Stinks
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Worth a look

http://planet-soaring.blogspot.de/
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Old Apr 12, 2012, 01:22 PM
Ricky Windsock
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I spoke to Thomas about them yesterday mate. Not available just yet but coming.
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Old Apr 12, 2012, 02:09 PM
Some people call me Maurice
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Nice design. I was worried they'd just offer a crude diode like Align does for their tail servos. The 1.5A version is far more than we'd ever need for F3X and would also be good for main system power on DLGs and small slopers. I assume the 2A version is for their giant scale and heli servos but should also be nice for total system power on small pylon racers and 3-4 servo gliders. Remember that linear regulators don't like high voltages so these will run much hotter on Lipo than LiFe/Ni.
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Old Apr 12, 2012, 03:07 PM
Eggcellent...
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United States, CA, Orange
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Quote:
Originally Posted by Kiesling View Post
I suggest getting rid of the regulator and using a 4 cell pack. With proper maintenance and care, I've had reasonable luck with the Elite 1500's using both JR/Spectrum and Airtronics 2.4 systems. Unregulated 5 cell packs are too much for the MKS servos. The MKS servos work fine with the 4 cell pack - plenty fast and plenty strong.

While I like LiFe packs a lot, for me, the issues with NiMh don't outweight the learning curve and concerns I have associated with regulators.
Agreed...did the same thing with my latest F3B ships since they have MKS in the wings. Really did not want to go back to NiMH packs, but the very big unknowns with regulators far outweigh the nickel-based pack issues.

Tom
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Old Apr 12, 2012, 03:19 PM
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Quote:
Originally Posted by Silent-AV8R View Post
I'm not really invested in any one solution as long as it works, but I have several issues with this per-servo regulator approach. Aside from the obvious weight and mounting issues, the main one I'll bring up now is that by MKS' own words the optimum servo operating voltage is "5.5-5.8v for optimum performance." So I'm curious to hear why they think regulating down to 5.0v is a good solution.

Chris B.
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Old Apr 12, 2012, 04:04 PM
Some people call me Maurice
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Good catch Dude! They seem to have a little trouble with the whole voltage thing. First they rate the servos for 6.0V implying that they should handle 5sNi packs just like every other 6.0V servo, then they secretly whisper something about 5.8V somewhere, and finally they release a 5.0V regulator.

That said, the chip employed is not adjustable so they likely only had the option of 5.0V. Some chips are available in 5.5V versions but they are far less common and more expensive.
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Old Apr 12, 2012, 04:31 PM
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Originally Posted by vespa View Post
They seem to have a little trouble with the whole voltage thing...
Indeed. For nearly all linear reg IC families there are adjustable versions available that only need 2 surface mount resistors to set the voltage so that's not an excuse.

Until I get one of each and test them out I'd rather not editorialize much about how good of a solution this is--yet.
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