RE: High amp 5955 servos
 

Same here, this is the most useful thing I have ever learned in this hobby hands down.

RE: High amp 5955 servos
 

Troy built models has a page on their website where they test current values, torque,
and the effect of extension lengths and terminal junctions. Expect a 25% reduction in applied
torque with significant lengths of extensions (20 + in)and multiple terminal junctions.

RE: High amp 5955 servos
 

The specification sheet for the 5955: ( http://www.hitecrcd.com/product_file...IFICATION..pdf ) says the servo will pull 4.2amps @ 6volts stalled that means when I was stiring my sticks with three of these attached and a throttle servo and getting a 15amp draw I was not far off, if you are getting a less draw than this I can only assume you are not trying hard enough. Changing direction from one extreame of movement to another, taking the weight of a large surface will get to the stall position of the servo IMO

Mike

RE: High amp 5955 servos
 

THis spec also implies careful and prudent battery and switch selection and maintenance. ON a large model, let's say 6 of these 5955's, it is probably good practice to have a battery/power system that can provide 6 x 4.5 for some short durations without voltage depression!!! Even assuming just a "flight loaded" transit current draw of 1.5 amp per servo (I have measured this), that means at least 10 amps has to be available, if demanded.

That'a a LOT of current, even for a short time, and we have to design around those demands.

RE: High amp 5955 servos
 

That's why I use a 3700Mah sub C five cell battery for the Rx and servo's. The only concern now is can the PC board copper lands inside the Rx take the strain? (rhetorical question)

Mike

RE: High amp 5955 servos
 

Mike,

All servos will have a high amperage draw when stalled. If you are truly stalling your servos simply by moving them to a full surface deflection, and indeed incurring that high of an amperage draw, you have only confirmed what some may have already suspected. Your installation is dead wrong and you don't know what you're doing.

Sorry to put it that way but I don't know, nor have I ever known, anyone that sets up their servos and linkage in a manner that permits stalling a servo in a no load condition. That's dead nuts. Simply moving surfaces through full range of motion will not stall a servo until and unless the linkage binds, the servo is being over driven, or the surfaces weigh more than the servo can lift. Any of the three indicates a lack of installation planning.

RE: High amp 5955 servos
 

THAT is always been a question in my mind, rhetorical though it is..... those RX designs were not done anticipating these incredibly amp-sucking servos. Wonder how this will continue to unfold...

RE: High amp 5955 servos
 

The "underinformed " will continue to f--k things up.

RE: High amp 5955 servos
 

Also true.
But - manufacturers of receivers *should*, IMO, publish a "nominal" total current capacity of the receiver connectors, and certainly publish a "maximum continuous", particularly if we're starting to look at higher power current draw servos and more of them as the "standard" configuration in bigger planes.

Part of being informed is a manufacturer providing information....

RE: High amp 5955 servos
 

Agreed.

RE: High amp 5955 servos
 

Okay -- if your average 30-40% plane needs a power system that can supply 10 amps what steps need to be taken? You can replace the switches and the connectors up the receiver with higher amperage units (Fromeco switches, Deans connectors, etx), but what about the connection to the receiver? A standard servo connector is good for 3-5 amps -- right? Even a dual battery setup with two connections to the receiver is right at the ragged edge for a 10 amp load. Do we need to go to triple batteries so each connector is supplying less than 5 amps? Or are we at the stage where power expanders (Smart Fly) are going to be the norm for models in this size range?

RE: High amp 5955 servos
 

This is the original question of this thread. You can get Fromeco's regulators with two or three outputs. This will provide 6 to 9 amps to the RX. Use 2 RX's, switches, regulators, and batteries, you now have 12 to 18 amps supplied to your system. There are other ways also, such as a powerbox or matchboxes with their own power source.

Jim

RE: High amp 5955 servos
 

OR-- you can get maximum power (really) with two, A123 cells with two sets of heavy duty leads - No regs to heat up no batteries to accidentally over discharge etc..
You guessed it ,I don't care for regs unless absolutely required then, I like external switching regs not linear type . The 2.4 system does not appear to be sensitive to the rf emissions from these.
The 123 cells will simply blow away any LiIon cell. But many guys are happy using the iLiIon/ linear reg setups with power distributing networks n regs etc.. No skin of'n my nose.
The "One charge last all week end "is a great adv ploy - but to me - of no value .
I charge as I refill the gas tank - My charger reads out actual remaining charge in cells ( CellPro A123 )as it tops em off
it will probably take a couple of years before the "word is out". The cells will crank out huge power -which means -- the voltage depression under our puny 4 -5 -6 amp loads is nothing to them - (I pull 40 50 amps from em with out even warming them and the voltage drops a little over one volt--under this load)
the problem now lies in connections and wire size . and --of course -the genious who stalls the servos -or under sizes the servos and operates em in an effectively stalled condition . Oh well -It's just a hobby-
Batteries , for many "fly one in a while guys"-- have been good/bad and indifferent - powerful servos and new radiosystems mean you have to bring your batts up to the present - No Ray O Vacs please.

RE: High amp 5955 servos
 

This is really my question. For a 10 amp load it appears that standard servo connectors and heavy servo wire are inadequate... Unless you address this end-to-end you will have a weak point...

RE: High amp 5955 servos
 

I am not entirely sure these power assumptions are realistic to begin with. Theoretically this is the sum of what people read when they plug measuring equipment and measure the load, them multiply by the number of servos.

In reality (at the field) the power provided from the batteries (let's assume they are cheap LiPos or Lions) with 10C or 15C packs, going through regulation and into the Rx (using 20G wires, Deans to Spektrum Rx), seems to be quite sufficient.

I run normally 5 Hitec 5955s or 8611a servos (86" QQ Yak or 88" EF Yak) and never seem to get into a power shortage situation, regardless (let's assume the throttle servo is moot in this equation).

Furthermore, when charging after several flights, the amount cosnumed seem to be much lower than what would be expected from the dire predictions related here - typically 150mah to 200mah per 12min flight on average. If the servos were to draw 10amps, even momentarily, I would expect overall consumption to end up much higher.

I don't claim this to be scientific or an answer to this question, but it seems that based on field data, people are making provisions for quite a bit more power than is really required - at least for typical 50cc class aerobats...

RE: High amp 5955 servos
 

I find all of this interesting... and while all of it is widely debatable it leads me to the same old question..

3D and high-end servos (not 5955s or 8711s) have been around for several years and some of the big names or even just got pilots have been flying 35 and 40%ers with 1 or 2 receivers, 2 switches, and 2 NiMH packs and flying the heck out of them without problems... now that new technologies are out and everyone started selling power expanders there is all this hype.

If we could do all the extreme flying before without thsi technology why are so many people jumping on this bandwagon and spending so much on all of these gadgets... is it really good marketing or am I just missing the point :D

If people would spend more time and energy on setting up their linkages / planes correctly the need for all of these gadgets goes down dramactically.

RE: High amp 5955 servos
 

yarom i am with you i have great sucuess without all those gadgets and plenty of servos on a receiver.

RE: High amp 5955 servos
 

many of the gadgets are just eyewash an trinkets - they work for the most part but necessary?
not for me .
the name of the game tho -IS more immediate servo power
This is whre measuring ampere Hour can be totally misleading
you really want a system that will respoond with instant huge driving force . no lag .
to do this the servos must swallow really deep chunks of power-
a system which will do this does two things
1 it maintains a reasonably constat voltage
2 the sudden draw of power does not appreciably drop the voltage -----UNDER LOAD--------.

The best batt I have seen for this is the A123. The NiMh super low impedance sub Ccells are also very good just heavier -in most cases the battery weight is highly over rated.
going to multi LiIons and regs - can work but the limits are in the regulators if they over heat -look out -it is a real problem

RE: High amp 5955 servos
 

Although not a 40 percent bird this 30% flys on one 1950 battery through one switch, a smart fly with two leads into the receiver.
There is no power shortage here and I work em hard[>:] I can even get about 7 flights that run 10 to 12 minutes on the 1950 and on the money I saved on widgets I bought a spare battery. Pull the velcro loose, pop in the spare and you are flying again for another 7 flights. I have done this to the tune of over a gallon of fuel in a day and again, there are no power shortages. Servos are 5945's and 5955 on rudder. I have flown it to the point that the rudder servo warmed up to 115 degrees F from electrical use (about 45 over ambient temp) and still no power shortages. I agree with Dick Hanson's statement.

RDB

RE: High amp 5955 servos
 

Don't mean to pick on you, but how do you know there are not power shortages?

Jim

RE: High amp 5955 servos
 

I did hear at a flyin I was at that the next gen of FUTABA servo's are going to be 7.4V lipo compatible. Suposed to be out this summer.

RE: High amp 5955 servos
 

Cause it goes where I point it:D:D

oh and comes down in one piece[8D] so far. Figure if something was to happen it would have in the first 130 flights.

But if you guys are looking for redundancy you might think abuout dual receivers. Had one of those go bad and caught it in time. The manufacturer said it was a "bad solder on the bus bar.

RE: High amp 5955 servos
 

Here is a 95 inch aerobat with the same battery/switch setup only add two extra digital servos 5945.

It goes where Ï point it too and comes home too. Can only get 5 flights on a battery charge.

RE: High amp 5955 servos
 

Just because it goes where you point it and comes down in one piece doesn't mean you weren't short of power. That's my point, how do we know if we have power shortages? I'd rather have too much power than not enough.
You might be O.K. on your 30%er. You probably have 6 servos in the plane and only one is a 5955. Get 9 or 10 servos with 8 of them being 5955's and it's a different story.

Jim

RE: High amp 5955 servos
 

If I had that many that you speak of I might be flying a 40% plane."I agree that that would have a different power requirement.

Look again at post #1

""Aileron - 2
Elevator - 2
Rudder - 1
Throttle - 1
Electronic Kill Switch - 1 "

Sounds just like a 30% plane, no?

Also, what difference is there if your 30% plane with xyz square inches of control surfaces and xyz weight flys on a 5945 or 5955? You can only get so much leverage out of the flight control at the same airspeed regardless of what servo it has. It only works badly when your servo is too small. IMO that just because the servo can go to 300+ inches of tourque doesn't mean it will use it all.

What if you put those 300+ inch lb servos in a .40 size trainer? Would you need monster power to drive them then?

http://www.csd.net/~cgadd/eflight/calcs_servo.htm