i3dm

My Feedback: (51)

Hello guys,

My friend has a Fei Bao Hawk, and after this:
http://www.rcuniverse.com/forum/m_7123279/tm.htm

He decided he wants to go back to 72Mhz for now, to avoid this trouble.

A couple of the Israeli pilots are insisting that a plane of this scale requires a PowerBox or SmartFly power expander, and my personal opinion is that its WAY overkill and un needed.

The plane carries:
2 x JR 8711 digitals (elevs)
2 x Mini 5125 Hitec digitals (ailerons)
2 x 5645 Hitec digitals (flaps)
1 x Analog Futaba (retracts)
1 x Analog Futaba (nose steering)
1 x 5125 Hitec sigital (rudder)

This is currently powere by TWO Fromeco 2600 7.4V Li-ions, on a Redundant PB Gemini, as recommended by Mr. PowerBox himself - Emmerich (the owner of PB systems).

What is your opinion guys ? is a power box \ power expander needed with this setup ?

thanks.

seanreit

My Feedback: (60)

Can your friend afford it?

And if not, does he really need to be flying jets?

Do you guys build your airplanes around other people's opinion's and insistances? Or are you guys accomplished enough to use your own minds as to what is best for you?

I would agree your list appears to be not that much servo power, but a overbuilding does not really hurt.

Billy

My Feedback: (15)

I would recommend the Powerbox in any aircraft that it will fit. It is a great way to get redundancy. I have used them in all my planes. Here's where I mounted it in the FB hawk. I mounted it to the side of the fuse.

Billy

Ehab

My Feedback: (44)

Hey Billy; I noticed you have one of the Rx's on top of the fuel tank. There was an earlier thread about the possibility of Kero blocking the 2.4 signal, any opinions?

Billy

My Feedback: (15)

I didn't seem to have any problems. I have a similar set up in my flash too. I will check into it though, thanks

adrian-RCU

mmnn- absolutely
\

Dave Wilshere

I3dm

He should go for an Evolution PB. The Gemini switch is great and would provide enough power, but the isolation on the Evolution would be a good idea with the amount of leads run around an aeroplane like that.


Dave Wilshere

i3dm

My Feedback: (51)

Thanks guys,

Keep the ideas coming !

Billy

My Feedback: (15)

I personally like the new Royal by Powerbox. Way more than you need for this hawk, but WOW it has alot of features. Just FYI

schroedm

My Feedback: (1)

Yep! VERY nice! Just starting to plan the install of that in my Skygate Hawk.........

clguru

My Feedback: (5)

WOW thou has spoken!!!!

i3dm

My Feedback: (51)

Here is the reply of Mr. PowerBox himself:
----
I think it is possible with the PB Gemini, the power is enough.

I read that Dave Wilshere from England write the PB Evolution. This is also possible if he want have not all the channels and servos direct on the receiver. The PB Evolution has more power and all the servos what he connect on the box are decoupled from the receiver, no HF and other interferences…
----

joeflyer

My Feedback: (48)

The truth is that most of the planes out there with powerboxes don't need them. It would be a relatively simple excercise to measure the current draw of each of the servos, add them up and see if you are exceeding the capacity of a standard receiver. Another simple test is to start with a fully charged battery, recharge after one flight to see how much current is use during a flight. Hard data is always better than opinions.

Many guys in the jet community, including some of the self appointed experts, lack a basic understanding of electronics or simple mechanics. The easy thing to do is throw money at it, then not worry and there is always someone willing to sell you the latest gadgets whether you need them or not. It's part of the more is better or I've got to have the latest technology mentality. A lot of jets around today have 400 in. oz. servos and 5000+ mah batteries that nobody had a problem with flying 5 years ago on 100 in. oz. servos and 2000 mah bateries.

If you properly size your servos and set up the linkages to not bind and with appropriate mechanical advantage you will minimize your current loads. Certainly some applications need a powerbox, and some could benefit from one, but those tend to be the larger most complex ones.

In the case of your friend's plane he has way oversized servos on the elevators (over 800 in. oz.). If it were my plane I'd have 8411's, or at most 8611's on the elevators. Also he'd be better off with analog servos on the flaps to minimize current draw.

Joe

i3dm

My Feedback: (51)

Just a note: we noticed about 150 Mah out of the battery after each 6 minute flight - thats about 1.5Ah avarage current draw, which leads me to believe that his problem in the other post was never battery related, but thats just my opinion.

adrian-RCU

lior - what you dont seem to grasp its not the total amp draw over a flight but the sudden burst when all of a sudden you draw a lot and the voltage drops for a split second below the rx's minimum volt requirement - this is when the rx goes to lock out - this is like a small spike and thats it - its not trying to justify anything here only to resolve the issue - thats why a powerbox works because it supplies constant voltage to the rx first before the servos, preventing lock out. so the issue of enough c's is the redundancy factor here - that you maybe have had an antenna issue remains a possibility - my point, never under supply your 2.4 rx - also follow up why people use the capacitor??

i3dm

My Feedback: (51)

Jan / Adrian,

What you dont seem to grasp is that im a student of electrical engineering, and i actually know 1 or 2 things about electric systems and currents \ voltages etc.

I agree with everything you said but even peek momentary currents should not have degraded the battery's voltage so much that it would go (after the regulation) to 4.2V, even for a pilot second, and lets not forget you need to degrade TWO packs simoultaniously not just one.

I dont see it happening. might happen if you use 1 pack \ 1 reg or even a Nicd \ Nimh pack, but the Gemini has 2 independable regulators, and making them both drop the voltage so low sounds like a hard task using only 4 digitals on such an application as the Hawk jet, i just dont see it happening.

Believe me i understand where youre coming from and i read many posts about these issues, but with THIS SPECIFIC setup, i dont see it happening, there's a very long list of setups that might cause this voltage drop easily, this is not one of them. thats my point.

See you this weekend.. i missed you guys from last year.

PS - current spikes, believe it or not, always happen for a reason (i.e. a large load on the servos of some sort). i personally flew this aircraft MUCH harder than Nessy did, for several flights, on the same packs and one 1 charge, and had zero issues. this is another reason why your theory doesnt quite fit to this specific setup.

After some more talk with Nessy, there might not have been a radio lock out at all, it seems he went vertical, stalled, and had the plane enter a flat spin ! he then did not manage to recover from the spin (thinking he had no radio control) until Ofir took control of the Tx and flew the Hawk out of the spin. the question still remins though weather Ofir had a lock out too when he was flying... i'll have to have a word with him.

Another thing thats strange is that the plane elegedly locked out for about 5 seconds (!) and fail safe didnt kick in (throttle didnt lower to idle)..

adrian-RCU

and my father is an Electrical engineer - so by the way

enough said!!

i3dm

My Feedback: (51)

Adrian,

Thats great, i didnt realize we are going to share the same proffesion !!

In that case im curious to what he thinks might cause such a high current peak in the system, to cause this voltage drop down. for sure, just normal servo load wont do it.

adrian-RCU

many factors but it seems that the current draw of 8711's are very high like most digital servos - i have read it over and over in many forums and discussions and most every time it was concluded that a sudden current draw causes the supply to drop for an absolute split second below the rx minimum and causes it to lock out before even failsafe can activate- why do you think spektrum and horizon added the capacitor, special regulators etc - for this specific reason - anyway this can continue forever - the goal here should be the fix it and thats it!!


im out!!

i3dm

My Feedback: (51)

Well, he did install the PB already with the two PB 2800 batteries. that will take care of any electrical problem if there ever was one for sure.

Of course the goal is to fix it, why do you think we are debating ? we are debating to try and conclude whether there is a chance that this was not a battery issue after all, and other areas might need adressing. Please dont take it personal, because it is not and never was.

Your explination makes sense, but still doesnt explain how I flew the plane so much (loading it more then Nessy) and had zero issues. this still doesnt add up, due to the simple fact that loads happen for a reason, not just out of the blue.

As far as this goes, im out too, C ya on Thursday my friend !

adrian-RCU

This info directly from spektrum

Performance modelers have known for some time that care must be taken to assure adequate power supplies for their airborne system. It’s true for all radio systems, but it’s doubly important when using high-performance servos, flying harder maneuvers, and trying to save weight with inadequate batteries and/or regulators.

Spektrum systems are designed with an operating threshold of 3.5 volts, and lower voltages cause the system to shut down. When adequate power is regained (usually the drop is momentary), earlier Spektrum systems re-boot and rescan for two previous channels before control is restored – a process usually requiring two to five seconds.

The new QuickConnect feature, however, eliminates the scanning delay and restores control almost instantly. We have been integrating this upgrade into receivers in a running change. Here’s how to identify if your receiver has QuickConnect:

With the system operating normally, simply switch the airborne power off, then on. If your system shows virtually no delay in regaining control, your receiver includes the QuickConnect feature.
Flashing LEDs indicate low voltage alert

QuickConnect allows most flyers to fly through common low-voltage situations caused by insufficient battery "headroom" – in many cases, without knowing a problem ever occurred. As a result, Spektrum engineers decided to program the system so that the receiver LEDs would flash, should the QuickConnect feature be triggered in flight. This can also be demonstrated on the bench, by toggling the airborne power.

If your receiver is missing one or both of these features, first off, it's important to recognize that the vast majority of flyers using "normal" servos with "normal" properly charged batteries will be unaffected by low-voltage issues.

However, if you're using numerous high-performance servos and wish to have your receiver system modified, simply return it to Horizon for free upgrading. Please return your receiver and all remotes, as all components must have the upgraded software for the new features to function. The best fix, however, remains assuring adequate power supply to the airborne system with sufficient voltage headroom.

Your flying success is of paramount importance to Spektrum as the leaders in spread spectrum technology, we're constantly moving the bar upward. Also, whenever you have questions regarding your Spektrum equipment, please feel free to contact our Product Support Team at 877 504-0233.