RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Do we know the MTTF (mean time to failure) numbers for the power interfaces? Without that number, it is hard to figure out whether a power interface is likely to be a point of failure in the entire setup.

For dual-battery, dual receiver setup, if both batteries are connected togather to the two receivers, then I do not think there is a single point of failure in the system.

--qc

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Will a single 6v 1950 sanyo handle 5-5955's +1 -425?
Thanks

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

In the worst case, a high-end receiver (e.g., futaba 149DP) can sense the low voltage and set the throttle to idle: just land it. This probably is better than flying it with one-half elevator, one aileron and no rudder, especially in a cross-wing landing situation.

--qc

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

mglaven, i have enjoyed reading this thread and your post. i lost a plane not long ago with 1 10 channel JR reciever, 9 servos, 2 2400 fromeco batteries with regs on reciever set at 5.95 volt each. i had a elevator servo fail and lock up and when this happened i lost almost all radio control of the plane. what control i had was very slow and intermitten. i beleive the reciever was overloaded and or the batteries could not keep up with the power demands. in a case like this i wonder if a power expander would have saved the plane. again i feel you have a lot of knowledge in this area and would love to hear what you think.

randy racer

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Randy,


Just a guess but I suspect the servo motor failure consumed near three amps sustained current and may have passed around some unharmonious noise over the control signal. Intermittent, delayed or slowed response is contiguous prior to PCM lockout or failsafe. A Smart Fly Power Expander would certainly help with power distribution and the like but would do little for short circuit protection and signal blocking in the event of a servo failure. The Emcotoec DPSI RV LDO Servo Interfaces or the ModelBau PowerBox's would have offered some of that desired "headroom" I spoke of previously.

FWIW: A pair of 2400mAh Lithium’s I tested on my programmable electronic load device sustained eight plus amps for well over twenty minutes if memory serves me. Thing is the Lithium-Ions don’t have much if any reserve capacity IMO, using my programmable load I can vary the load from zero to thirty amps over any given test run over and over or anywhere in between, the voltage falls drastically, degradation is imminent when you hammer Lithium-Ions. I'd like to see double the battery capacity with Lithium-Ions in your next model, the slight weight increase is negligible and the simple fact that 4800mAh batteries are redundant in of themselves is pleasing too… (A 4800mAh battery is comprised of four 2400mAh cells in series-parallel. If one pair fails its still operates on the latter pair)

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

nonstoprc

As far as I know the RC Industry and specifically the servo interface industry has yet to perform any MTBF tests due to the costs associated thereof...

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Slyder,

The Sanyo HR-4/5FAUP 1950 cell's should work fine with your servo load. Keep in mind you need to get the power to the servos so don't skimp on extensions and switches, in fact a Smart-Fly HD switch with Deans connector and multiple power pigtails to the RX is highly desirable IMO.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Michael, Would LiPO's be a better alterative than going to 4800 ions. The 4800's weigh more than the 1950 Nimh's and I'm not sure they can provive any better current. The only advantage I can see is a few more flights before recharge. How about two 2400 Lipos.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

thanks mglavin, my next plane will be a 40% size and i was planing on 2 4800's due to using more servos. what you said is more reason for bigger batteries. it was a servo motor that smoked so what you said makes since, i'll look into the units you listed.

thanks again

randy

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Here's a question for those interested: If you could have it, wouldn't you rather have a system that would prevent a servo motor from "smoking"? while letting everything else continue to work?

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

What is the major cause for a servo lookup? The worn gears or component failure? --qc

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

NJ,
After reading some of your statements, I know you know the answer to your question, of course we all would like a system that would work in the face of a locked up servo. From what I've heard you say, you should get to work & design the damn thing! Your knowledge in this area is obviously vast. Find out the short comings of the others & get to work. We will all be glad to do field tests for ya. I can tell you one thing, In all my years of working on things, in the end, its hard to beat simplicity with technology, there is a fine line there where the added complexity of any added on unit no matter how reliable will utlimately have some draw back, weight, size, ect. But usually, the more things in the system the more there is to break which is what was mentioned earlier. However, the new minature electronics may have the answer. In the end, I would be nice if we could list (or try to) list all the practical setups in use today with there good & bad points so the users could decide what they think is best for them. I find this thread very relevant as I'm building my first 35% plane & I just ordered a smart fly pro, Now that I've read this thread, I'm trying to figure out if I've done the thing that I want!!!!!!!!! Thanks all.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

mglavin, have you read anything about the smart fly EQ10. if so what is the differance and do you think it's a good thing?
i plan on using hitech 5955's and using a programer on the next set up. also will the 5955's hold up with 7.2 batteries without regs?

randy

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Why doesn't anyone demand it then? You see a lot of money invested in boxes that can pump alot of current out, but can't deal with a common fault condition. I've heard that a distributor of one popular device proudly demonstrates its ability to burn up a servo extension. Apparently that's a selling point.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

In some cases that would be a sellling point. If the supply can survive until the short kills itself, then It could regain control. Obviously a circuit breaker on the output side ( or fuse) would be ideal. I guess it hasnt crossed the designers minds. This is the american way.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

I know that to be fair, without a box in the middle you have the same basic fault scenario possible. But it just strikes me as odd that when you go to all the trouble of adding something in between that could manage some fault scenarios, it hasn't been done yet.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

From a pure potential stand point, yes without doubt the right LiPo's will work quite well. Were using Duralite Li-Po's together with a Duralite PowerBox in Josh's 100" QQ Yak's, so far no issues. The only consideration is the battery durability IMO, the fragile nature of the cell solder tabs is of concern. So proper battery and power lead vibration isolation is paramount to trouble free performance. Forgo the use of a wimpy piece of foam and a couple of tie straps in lieu of sound bed of vibration protection foam padding and a couple Velcro straps that are NOT overly tightened. Additionally I like to loop the power leads back through the Velcro straps if possible and then on to their final connection.

Two 2400 mAh Li-po's will do nicely IMO.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

:D

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

Tough to answer with any credibility IMO, to many variables in play... But in many-many-many cases improper set-up takes its toll over time leading to motor and or component failure. There is a lot to be said for proper linkage geometry and bind free installations. I have seen time and time again less than desirable conditions with the premature servo failures to attest the shortcomings thereof.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

I looked on Bob's site and didn't see any info on an EQ10?

The 5955's are not rated for unregulated Lithium power sources, (8.4V is static after charge)... Many have attempted this and had less than desirable results.

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

How do you perceive the BOX reacting to a bad servo(s), what specifically do you envision? Would the servo go limp or passive (power down I suppose), hold position, minimize power???

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

From the Hitec Site

HS-5955TG DIGITAL ULTRA TORQUE 250oz/333oz .19/.15 SEC TITANIUM DUAL BB 1.6"x0.8"x1.5" 2.18
* HSR-5995TG DIGITAL ULTRA TORQUE/ROBOT 333oz/417oz .15/.12 SEC TITANIUM DUAL BB 1.6"x0.8"x1.5" 2.18


From the side of the box my 5995 came in;

HSR-5995TG
Coreless Digital/
Titanium Gear Robot Servo
at 7.4 Volts
Speed: Max 0.12 sec 60 deg
Torque: 30.0 kg.cm (416.61 oz. in)

I have one on my rudder on a 50cc Extra running on 6v batteries for many flight hours. The fact that they are factory programmed for 180 degree of travel makes one want to use a servo programmer for airplanes, but the good news is that I could get whatever travel I wanted on the rudder:D

Richard

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

the smart fly eq10, may not be the right model #, there is a thread on FG on the manufacturs forum. KIWI is testing one.

thanks for the info on the 5955 i was told it would run on non regulated fromco pack. looks like i need to stay with the regs.

randy

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

I highly recommend check the 5955 with a programmer. I found the speed on mine is set way too slow (a value of 12 instead of 2) and hence slow rudder response. Regrogramming to correct it. --qc

RE: Can Futaba R149DP handle 5 5955 servo or do i need a Powerbox?
 

You are talking about 2 different servos there... a 5955 and a 5995 not sure if you were aware or not...