Help!!

[AliC]

Help!
I feel kinda foolish.
Although I am a regular 'lurker' this is my first post, and that is why I am even more sheepish.
Tonight I was putting the finishing touches on a 20" Nutball electric foamy ( see this link http://www.rcgroups.com/forums/showthread.php?t=836389 ). This was to be the ideal low cost airplane to take me off the simulator and into the sky!
I had very diligently measured the max amps of my prop/ motor/ batt combo to ensure that I wouldn't fry my esc.
I was delighted that the max draw was below 10 amps - perfect for the Turnigy Plush 10A esc I had been hording since buying it from Hobbycity almost 10 months ago.
I carefully slit open the exotic plastic pouch (tongue poking through side of mouth - eyes bright) and gingerly soldered on the appropriate connectors. I then plugged it into the motor (already mounted on Nutball) and connected the RX and battery connections. Both were lying loosely on the kitchen table beside (behind the prop arc!) the Nutball.
I switched on the transmitter (also a shining new never before used Futaba T7C 2.4gig FASST unit : P ) and after the obligatory tone from the esc, gave the throttle a couple of smooth blips. All is well ! 'Sexy' was what I was thinking!
I then switched off the transmitter so I could permanently attach the Rx, battery and esc to the airframe. Thats when it happened!
The esc sounded a couple of short tones to I staring dumbly at it . I was wondering "what the..?" Then the motor suddenly jumped into full speed and the Nutball took off across the kitchen (narrowly missing me!) and dragging the esc battery and FASST receiver behind it until striking the coffee machine and coming to rest on the bench top only a short distance away! All of this happened in a nano-second!
Luckily the kids were in bed and the wife is away visiting the in-laws for a few days.
To cut the story short, the end result is that everything 'seems' to be OK - except the most expensive bit! The FASST receiver (this one http://2.4gigahertz.com/receivers/futl7627b.jpg).
It lay on the bench - wounded like some poor, run-over creature! Its lower plastic case pulled off and both its antennae ripped out. One (found across the room) appears to be the full length - albeit detached. The other was not so lucky! I found (so far) only a 5cm portion of it (again, flung to another part of the kitchen). The rest, I believe, may have disappeared into 'the atmosphere'!
Now, to the questions.
Can anybody tell me what these antennae are made from (braided wire?), and what their proper length should be?
I have discovered that these receivers are the best part of $100 US (about $4,500,284.26 Aust with the appalling current exchange rate!), so the cheap side of me has decided that 'we can rebuild him'.
Any help is greatly appreciated!
I hope this long-winded explanation will be my only post over ten words.

Kind regards
Ali :eek:

The Futaba Spec on this shows a weight of 4 grams
(ie $100US /4grams >> $25,000US/ Kg !!! :eek: :eek: )

[dmccormick001]

I suggest you send your Rx back to Futaba and let them check it out and install new antennas in it.

By the way, I hope you've realized your mistake? Always turn the radio (transmitter) on first, then the plane (receiver), and always turn everything off in the reverse order, plane first, radio last. The idea is that you don't ever want to have the Rx on when there is no signal from the Tx to control it, especially with electric motors. With no instructions on what to do/not do they can go berzerk and hurt you.

[rc404]

Actually with the Futaba Fasst it doesn't go berserk, it goes into failsafe. For the Fasst than means all channels, except throttle, hold their previous position. Throttle goes to a preset position intended to be idle/off. For some reason someone very much smarter than me will need to explain, Futaba has their throttle direction reversed from what most ESC manufacturers build in (you probably had to reverse the direction on throttle stick to get the ESC to arm??)

The throttle failsafe can be programmed to anything you want. But the default is what Futaba considers idle and reversing the throttle direction affects only the transmitter and doesn't change the failsafe position that is programmed into the receiver. So when you turned the Tx off, the receiver went into failsafe and the throttle went to what Futaba considers idle, but most of the ESC world considers full.

When you get it all working again, you really need to set the failsafe throttle position to true off. Sorry for the misfortune.

[rich smith]

Switching TX off before plane is an incompetent move regardless of what failsafe features are imagined to exist.

[AliC]

Yep!
Realised my mistake 2 secs after aircraft went wizzing by my ear.
Thanks guys.

Ali

[rich smith]

Yeah, tell me about it. "Incompetent" is my middle name. Fortunately the el cheapo DSP RXs usually just beep instead of take my finger off. They are getting better but still pays to be careful.

Yep! Realised my mistake 2 secs after aircraft went wizzing by my ear. Thanks guys.
Ali

[BushmanLA]

The antenna wire shouldn't be anything special, just solder a new piece of wire back on of the same length. Hopefully you can get the length from someone, I don't have one of those.

[AliC]

I feel pretty foolish.
I take safety very seriously!
But all it takes is a slight lapse in concentration and you are suddenly 100 grams 'lighter' with a couple of your 'once attached' digits lying on the floor, and you left wondering how you will explain to your employer that you no longer have an opposable thumb to be able to grasp the controls of their heavy equipment! :eek:

I just found a miniature gold elbow connector next to the microwave this morning.
I'm sure it belongs to the FASST Rx.
This is all beginning to look a little bit too 'spekky' for a home band-aid job.
I think I'll take the advice of dmccormick001 and send it back to Futaba, or, sell one of the kids and just fork out the $4,500,284.26 Aust for a new one.

Ali

[rc404]

Switching TX off before plane is an incompetent move regardless of what failsafe features are imagined to exist.
Was not recommending a practice of relying on failsafe. Just trying to point out that the FASST system has a default failsafe that can be highly dangerous if not reprogrammed. The off switch isn't the only reason you can loose RF contact and put the receiver into failsafe.

[AliC]

Thanks BushmanLA.
I will see if I can obtain the exact spec from someone who might have the same Rx.

Cheers,
Ali :p

[dmccormick001]

The throttle failsafe can be programmed to anything you want. But the default is what Futaba considers idle and reversing the throttle direction affects only the transmitter and doesn't change the failsafe position that is programmed into the receiver. So when you turned the Tx off, the receiver went into failsafe and the throttle went to what Futaba considers idle, but most of the ESC world considers full.


Assuming the FASST system works as you describe, and I have no reason to believe otherwise, I have a question or two. If the Rx has a pre-programmed "default" failsafe setting for the throttle channel, whether it's full one way or the other, or last known position, or centered, or whatever, and if you reverse the throttle channel in the Tx's programming in order to make it work correctly with your ESC, are you telling me that it doesn't change the failsafe direction automatically for you? You have to go into the failsafe menu and modify the settings there, too? What do you do, tell it to go to full throttle instead? I mean, if that's really how it works that's the craziest thing I've ever heard!! I can't believe that changing it in one place doesn't change it everywhere else.

My second question, is this true of ALL Futaba radios that have a failsafe feature, or is it just unique to the FASST systems? I've been flying with a Futaba for a long time, but I've never checked to see if reversing the throttle channel makes the default setting on the throttle failsafe wrong. I probably reverse the throttle channel on my planes as often as not, depending on whether I'm using a 4-stroke, inverted, etc., and I've never thought to look at this. You can bet I'll check them when I get home this afternoon.


EDIT: Thanks for pointing this out rc404! I've been flying with an older Futaba 8UA for quite a while now, and had NEVER realized that reversing the throttle direction in the Tx didn't reverse it in the failsafe settings, too, but it doesn't. Evidentally, they realized the stupidity of this situation and changed it in the next model they introduced, the 8UA Super, but mine is just as you described. My club has had a couple of incidents where models seemed to lose signal and crash, but were WFO when they did, and we were never able to figure out what happened, because the owners had thought their planes were set up correctly with the failsafe settings in place. This may have been the reason for some of them. What I can't figure is this..if they changed it at one time to operate as you would expect, so that changing the throttle direction one place changes it everywhere else that it might affect something, why in the blazes did they ever go back? Makes no sense. Anyway, thanks again for bringing this to my attention. As they say, "Ya' learn something every day."

[Tomapowa]

Some info here on FASST replacement antennas:
http://runryder.com/helicopter/t431237p1/

They mention these antenna might have special connectors on them... i.e., not soldered.

I think the FASST antennas are around 5" long... as mentioned here (not sure where this is measured from... maybe actual antenna length from connector to tip/end):
http://www.rcdude.com/servlet/the-706/Futaba-R617FS-2.4ghz-FASST/Detail

[Tomapowa]

Well look what I found here! :)

http://cgi.ebay.com/HSP79493-Futaba-2.4GHz-FASST-Receiver-Antenna-Cable_W0QQitemZ110341638693QQcmdZViewItemQQimsxZ20 090123?IMSfp=TL090123111003r4108

And yet another discussion:
http://www.rcgroups.com/forums/showthread.php?t=853454

[pilotpete2]

Regarding the throttle failsafe on Futaba and Spektrum receivers.
The throttle failsafe is set at the time the receiver is linked or bound to the transmitter. If the throttle channel is reversed anytime after linking or binding the receiver, the failsafe will be wrong. when a setup is complete you should make sure the throttle is closed, then relink or rebind the receiver and test to see that the throttle failsafe is correct.
Pete

[pilotpete2]

The antenna wire shouldn't be anything special, just solder a new piece of wire back on of the same length. Hopefully you can get the length from someone, I don't have one of those.

A simple piece of wire it ain't. It's a specific type of coaxial cable for 2.4Ghz use ;)
Pete

[dmccormick001]

Regarding the throttle failsafe on Futaba and Spektrum receivers.
The throttle failsafe is set at the time the receiver is linked or bound to the transmitter. If the throttle channel is reversed anytime after linking or binding the receiver, the failsafe will be wrong. when a setup is complete you should make sure the throttle is closed, then relink or rebind the receiver and test to see that the throttle failsafe is correct.
Pete
Here's a portion of some information I copied straight from Futaba's web site today. I looked up the owner's manual for my radio, the 8UA, and the site explains that the only manual available for download is for the newer 8UA Super that was released shortly after the 8UA, and it lists the differences between the two.

Please note that the following features do not apply to your 8U radio:

The 8U's digital trim buttons did not beep when moved past center.
The 8U's trainer function did not offer function/normal modes (see our F.A.Q. for extensive details).
The 8U's stop watch did not have a power-switch ON mode.
The 8U's F/S data direction for throttle did not change automatically when the throttle channel servo's direction is reversed.

This last one blew me away. Like I said, I've been flying with this radio for a long time now, I really like it, how it feels, etc., and I've even put some parts in it to keep it going, and never realized before today that the failsafe might not be set correctly on some of my planes. Glad I haven't needed it before now. I'll bet there are a host of guys out there with older radios who don't realize it either.

I don't own a 2.4G radio yet, not sure if I want one, so I can't speak to the discussion about the "default' setting on the throttle channel and most ESC's and all, and whether or not reversing the channel in the FASST radios also changes the failsafe setting, but I can tell you that on my radio, it evidentally does not. I guess the lesson is, if you own a Futaba you'd be wise to check it by watching it while you turn your Tx off.

[rc404]

I guess the lesson is, if you own a Futaba you'd be wise to check it by watching it while you turn your Tx off.
I think the lesson applies to any radio with a fail safe. And all the 2.4GHz radios inherently use a digital protocol, they all have some kind of fail safe logic. Its best you know that it really is what you want it to be.

[AC5FF]

Ali
I'm sorry to hear about your mis-adventures... I'm sorry to say that I've been there (still got the scar on my knuckle from the prop!)... Just takes once - I've not forgotten to unplug my RX before turning off my TX since! :D

[AliC]

Thanks to all, especially for the links to the replacement antennae.
AC5FF - The hard learnt lessons are the ones that stick the best (particularly when you have scars to remind you)! :p
I'm glad the outcome for me wasn't as bad as it could have been - I'm kind of used to having a matching set of ears attached to my head! :eek:

Cheers,
Ali :D

[pilotpete2]

dmccormick001,

The information in your Futaba manual only relates to failsafe settings with a compatible Futaba PCM receiver. This info is not at all relevant to the throttle failsafe provided if using a Futaba FASST or Spektrum conversion module in your radio, both systems only have a failsafe on the throttle with receivers of 7 channel or less, this failsafe is receiver based only. Full failsafes settable from the transmitter are only available on the native 2.4Ghz systems starting with the X9303 for JR/Spektrum and the 10C for Futaba, and then only if using a receiver of greater than 7 channels with either radio.
In the case of a Futaba radio, it is almost carved in stone that the throttle channel servo reverse setting must be set to reverse when using an ESC, with a throttle servo then, as with any radio it's a coin toss, so it's important when setting up any new model to get the throttle correct, then relink or rebind the receiver so that the throttle FS is correct and will go to idle in the event of loss of signal from the transmitter.
Pete

[jesolins]

Suggestion for Futaba 2.4ghz antenna replacement: You can just get a typical U.FL coax for laptop wifi and cut the outer shield to size to expose 2cm of the inner teflon shield and wire...works for me;) You can scavenge it from a dead laptop, or get some on EBay: This one gives you two antennas and 29cm of wire to make a longer antenna run if needed for $3.99. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=250478326593&ssPageName=STRK:MEWAX:IT
Cheers,
Jim