36" to 48" extensions
12-28-2007, 08:28 AM
#1
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36" to 48" extensions
Hey Guys, putting together a Jet(Elan) that requires a couple of 36" and 42" extensions. I have in past used 30" extensions with no ferrite rings or inline filter/amplifiers. I have seen Jets and Gassers that use them and some that don't, how important is it to use anything if the extensions are well isolated? does the amp draw of the servo complicate things?
Thanks for any info
Angus
Thanks for any info
Angus
12-28-2007, 10:20 AM
#2
RE: 36" to 48" extensions
I've got several 48+ inch extensions in my jets/gassers, i made them with 22 awg servo wire with no filters at all and I've never had any problems with radio interference. i do keep any interfering components (ECU/Ignition module/Fuel pump/etc...) as best away from any radio gear as i can as well. i've found that making my own extensions so everything is the perfect length for how i want it installed/routed with no extra length to tuck away or extra connections from joining multiple extensions when necessary helped rid allot of potential interference problems.
12-28-2007, 11:00 AM
#4
My Feedback: (1)
RE: 36" to 48" extensions
I too custom make my own extensions at any length. Since wire is a heavy item I'm always conscious of using bare minimum gauge ie 20g-24g and even combo pos/neg to dual servos and run smaller gauge yet for signal wire. I've never had any issues and believe longest runs for me in the 40" range?
I do however use only twisted wire as a feel good cure. Even the flat wires on servo's, I will decouple the plug end split wires and twist them, as well as any other wire in the model, ie, turbine wires, glo plug lead, batteries.
FWIW, I'm not a big believer that these things draw such large servo current, ie, plugs and receiver buss bars have NEVER changed from the original designs from the mid 70's even though servos have grown by 400% torq values. Also even in larger models with all 8711 servos QQ big YAK only uses a total 7.5 amp voltage regulator,....
Quote:
UPDATE: Quique’s “unscheduled landing†(ie crash) during noon-time demo at SEFF underscores the importance of an adequate power supply when employing 8711 servos.
Quique flew his new Python biplane, equipped with the new JR9303 2.4 and seven 8711 servos, during the noon-time demo at the fantastic SEFF event last weekend. As usual, his dazzling display of high alpha rollers, on-the-deck high speed slow rolls and other superb maneuvers thrilled the crowd. However, after about 5 minutes of hard flying, he was doing a torque roll and lost control, sending the model into the grass with relatively minor damage.
A team of Horizon engineers retrieved the model and along with Quique, set about to find the cause. As we all know, often crashes are hard to explain, but after some investigation, we were able to determine the cause of the crash beyond a reasonable doubt.
By employing seven of the 8711 servos, the demands on the power system increased. As needed to produce the 403 ounce inches of torque, the 8711 will draw more current to do more work. Fact is, the 8711s sustained current can be 3.9 amps.
Quique’s voltage regulator was a 7.5-amp version, and probably survived his test flights in Ohio due to the lower ambient temperature. But at SEFF, with temps higher than he’d flown in, the operating temperature of the voltage regulator soared, causing voltage to the receiver to drop below the operating threshold of the receiver (3.5 volts), resulting in a system shutdown.
We know this for two reasons:
In the hangar, we were able to apply light loads to the servos, and in short order we observed the voltage drop below minimum operating voltage. Even operation of all servos simultaneously (with no load) indicated a significant voltage drop.
Upon retrieval of the model – before the power was shut down, we plugged in a Spektrum analyzer to review the number of fades and see if the system received any dropped frames. Normal flight will usually see a number of fades in the multiple receivers (this is normal, as the best signal is utilized between receivers with the Spektrum technology) but in Quique’s model, the counter showed “0†for all parameters. The only explanation would be that the receiver had been shut off in flight (data is not stored when the power is disconnected).
What’s the lesson? 8711 servos are powerful, and allow your model to perform as never before. But steps must be taken to assure the servos receive adequate power supply.
Furthermore, while regulators have their place in certain applications, we urge all fliers to review their use and use caution when old-generation regulators are combined with the new generation of high power servos. And to set the record straight: The buss bar power system in JR/Spektrum receivers is very robust, capable of withstanding continuous current far in excess of 20 amps.
I do however use only twisted wire as a feel good cure. Even the flat wires on servo's, I will decouple the plug end split wires and twist them, as well as any other wire in the model, ie, turbine wires, glo plug lead, batteries.
FWIW, I'm not a big believer that these things draw such large servo current, ie, plugs and receiver buss bars have NEVER changed from the original designs from the mid 70's even though servos have grown by 400% torq values. Also even in larger models with all 8711 servos QQ big YAK only uses a total 7.5 amp voltage regulator,....
Quote:
UPDATE: Quique’s “unscheduled landing†(ie crash) during noon-time demo at SEFF underscores the importance of an adequate power supply when employing 8711 servos.
Quique flew his new Python biplane, equipped with the new JR9303 2.4 and seven 8711 servos, during the noon-time demo at the fantastic SEFF event last weekend. As usual, his dazzling display of high alpha rollers, on-the-deck high speed slow rolls and other superb maneuvers thrilled the crowd. However, after about 5 minutes of hard flying, he was doing a torque roll and lost control, sending the model into the grass with relatively minor damage.
A team of Horizon engineers retrieved the model and along with Quique, set about to find the cause. As we all know, often crashes are hard to explain, but after some investigation, we were able to determine the cause of the crash beyond a reasonable doubt.
By employing seven of the 8711 servos, the demands on the power system increased. As needed to produce the 403 ounce inches of torque, the 8711 will draw more current to do more work. Fact is, the 8711s sustained current can be 3.9 amps.
Quique’s voltage regulator was a 7.5-amp version, and probably survived his test flights in Ohio due to the lower ambient temperature. But at SEFF, with temps higher than he’d flown in, the operating temperature of the voltage regulator soared, causing voltage to the receiver to drop below the operating threshold of the receiver (3.5 volts), resulting in a system shutdown.
We know this for two reasons:
In the hangar, we were able to apply light loads to the servos, and in short order we observed the voltage drop below minimum operating voltage. Even operation of all servos simultaneously (with no load) indicated a significant voltage drop.
Upon retrieval of the model – before the power was shut down, we plugged in a Spektrum analyzer to review the number of fades and see if the system received any dropped frames. Normal flight will usually see a number of fades in the multiple receivers (this is normal, as the best signal is utilized between receivers with the Spektrum technology) but in Quique’s model, the counter showed “0†for all parameters. The only explanation would be that the receiver had been shut off in flight (data is not stored when the power is disconnected).
What’s the lesson? 8711 servos are powerful, and allow your model to perform as never before. But steps must be taken to assure the servos receive adequate power supply.
Furthermore, while regulators have their place in certain applications, we urge all fliers to review their use and use caution when old-generation regulators are combined with the new generation of high power servos. And to set the record straight: The buss bar power system in JR/Spektrum receivers is very robust, capable of withstanding continuous current far in excess of 20 amps.
12-28-2007, 12:48 PM
#5
My Feedback: (15)
RE: 36" to 48" extensions
c/f,
Where do you get your twisted wire (20 or 22 gauge), plugs and tools for splicing? I need to make several twisted extensions and have not done this before. I would like to make mine as "good" as the JR heavy duty wires that have served me well for a long time.
Thanks
Dave D
Where do you get your twisted wire (20 or 22 gauge), plugs and tools for splicing? I need to make several twisted extensions and have not done this before. I would like to make mine as "good" as the JR heavy duty wires that have served me well for a long time.
Thanks
Dave D
12-28-2007, 01:14 PM
#6
RE: 36" to 48" extensions
i get mine from Air Wild Hobbies.
http://www.airwildhobbies.com/MoreIn...&level=2&id=40
I've gotten it from BP Hobbies in the past and recently picked up two packs of 50' for 5 bucks each on Closeout Price, but they seam to be closed out of those
http://www.airwildhobbies.com/MoreIn...&level=2&id=40
I've gotten it from BP Hobbies in the past and recently picked up two packs of 50' for 5 bucks each on Closeout Price, but they seam to be closed out of those
12-28-2007, 03:18 PM
#8
My Feedback: (1)
RE: 36" to 48" extensions
[quote]ORIGINAL: ddennison
c/f,
Where do you get your twisted wire (20 or 22 gauge), plugs and tools for splicing? I need to make several twisted extensions and have not done this before. I would like to make mine as "good" as the JR heavy duty wires that have served me well for a long time.
Take a look at Servo City. I got twisted wire and connectors from them.
12-28-2007, 10:31 PM
#9
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RE: 36" to 48" extensions
Angus, I have used the JR filter rings on all my extensions and have never had a glitch..... If you are not on 2.4, those long leads can act as antenna for interference both from within the jet, and from the emf environment you are flying in. The very worse case is that they don't work, but cause no adverse effects. I believe, though, that they are very effective.
