jetflyer

My Feedback: (5)

For those of you already flying with dual packs, you can skip this message. For the rest of you still using single packs, you might want to read on and do some checking plus consider using 2 packs.

On my turbine Super Reaper, I have 2 servos on the canards, 2 for the ailerons, and 1 for the brakes. Because I have the brakes mixed with down elevator and ailerons setup as elevons I can have 4 or 5 servos working with movement from the right TX stick at any one time.

I recently changed out some servo wire extensions I had for connecting my wings from 24 gauge (home made extensions) to 22 gauge store bought extensions. During my next flight with the wire change, I was doing a pre-flight check of all my surfaces before taxiing out of the pits and after I bounced the right stick a bit, the turbine flamed out. I tried to troubleshoot a few other things first before I placed a Hobbico voltage watch device on my system. It wasn't until then that I noticed the bouncing of the right TX stick was causing the green light to go down into the red showing a voltage drop in my system. I packed up and went back home and tried using a 6v pack and the same problem showed up although I could bounce the right stick back and forth at a much faster rate without going into the red. Moving the stick with normal "In flight" stick movement did not cause the voltage watch to drop into the red. I then decided to try a Mini Hobby voltage regulator with a 6v pack and installed a second on/off switch so I could plug my previous 4.8v pack in. Now, with dual packs, I could bounce the stick without going into the red on the voltage watch.

So for you guys out there who are running multiple servos at one time, you might want to check your voltage. It was not until I changed out my servo extensions that my turbine started to have flame out problems. The voltage was dropping low enough to cause the ECU to shutdown the turbine. All this was not apparent until I actually installed a device to monitor voltage while the radio system was active and under load.

From now on, I will use dual packs and verify the voltage is adequate with all my future planes. And if I make a change to the radio system I will certainly check for any voltage drops.

Now go check your setup!

JR Gautreaux

sideshow

My Feedback: (11)

Do you mean two Rx packs (dual switches) + ECU pack, one pack on the Rx and another on the ECU.....or one pack for the whole shooting match?[X(]

I have two 2150 Nimh packs on the Rx of my Bobcat...along with the 1250 nicad that came with the P-120. My F-15 is using one 4000 Rx pack (w/ failsafe switch) and one 4000 ECU pack, both of which are Li-ions. Eight flights....no charging!

Were you using one pack to run your ECU and your receiver? What was the capacity?

geneh

Hi Jet Flyer.

I am running a 4 cell 1700mah nicad pack for the RX and servos and a 5 cell 1700mah pack for the ecu. I have not seen any problems because of this. I am using 4 Hitec digital servos and two JR 4721 servos as well as a electronic brake valve. I think that I will check mine to see though.

Thanks!

Gene

jetflyer

My Feedback: (5)

Bob / Gene,

I am running the standard ECU battery that came with my Ram 750P. And then I was running a single 4.8v 3000mah NiMH RX battery. Now for RX power I am running a 6.0v 1650mah NiMH with a Mini Hobby regulator and the 4.8v 3000mah NiMH each on separate switches. And now with the addition of the Hobbico voltage watch onboard, I can easily see if my RX batteries are showing OK before each flight. Just a little added visual insurance.

Gene,

I would check the voltage just to be sure. I did not notice the problem until I redid my extension leads, but I don't know if it was happening before either. Since the voltage watch device only has LEDs to show a voltage reading I also made a female-to-female servo connector so I could plug in my Hobbico volt meter and that is when I saw the voltage drop from 5.2 to 3.8 while bouncing the right stick. Of course normal in flight stick movement did not drop the voltage. I'm running Hitec 5625mg servos throughout.

JR Gautreaux

SJN

Im running a single 3300 NiMh 6 volt pack with 2 on/off switches in parallel to the RX so it can get all the juice it needs...

Silver182

My Feedback: (2)

I am changing over to lithium polymer battery packs... the High capacity type sure have the punch... and weight in less than half the weight of a Ni-cad. I just recently replaced my original Jet Cat ECU Bpack with a KoKam HC 1500ma LP pack. It weights in at a third of the original Ni pack. It can be field charged in less than 1 hour ..... the voltages consistently read .5 volts higher than the Ni-cad--- even during the startup phase.

My Rec. is powered by one 3000 mil Ni-cad and one regulated (5.7v) LP 2400ma pack
off to work for now...
Lee

S_Ellzey

My solution in my KingCat was to run the receiver, nose steering, retract, and smooth stop on a 4 cell 1200 Mah Nicad, and the rest of the servos on a 5 cell 2200 Mah Nicad with its power carried back to the servos with 14 gauge wire (one set per side). This supplies very constant power to the receiver, and should I add a gyro in the future it can run on the 4 cell pack. The receiver battery goes all day with out having to be recharged, 250 Mah is about the most I have ever had to put back into it. Doing this requires that you either buy a power buss, or in my case, know how to wire it up your self.

I still like Nicads, they are very reliable, and very rugged. With me and the wife flying, I can charge one plane while the other is flying and go all day with out having to wait for a charge to finish.

Steven

lov2flyrc

My Feedback: (24)

Ummm...... am I the only one who thinks there is a problem with JR's setup???? [sm=confused.gif]

4 flight control servos and a bump of the stick is causing serious voltage drops!?!?!?

JR, from the sounds of it you have a problem in your radio system. I would NOT fly that aircraft till you have put a load checker on the system to check your current draw. I would highly suspect you either have a bind in the linkage or a servo problem somewhere. There is NO reason 4 servos should be pulling that much amperage especially not under any load!

Todd

jetflyer

My Feedback: (5)

Todd,

It does not appear that I have a bind as all servos are in the plain view, but keep in mind that I am bouncing the sticks pretty quickly too. But it is possible that I might have another problem other then what I recently fixed. To be sure I am planning to remove all my servos and plug them directly into the RX without any extensions and see if I get the some results. If all is well, then I will start adding the extensions one at a time until I see the problem occur.

The wing setup is as such: I have 3 extensions - one 12" from wing servo to just outside the wing tube, one 36" to almost the nose section, and one 6" to the RX. Prior I had the wire run from the wing servo to the 6" extension to the RX. The Reaper's fuselage is quite long and I have the RX located in the nose.

If I get some time this evening, I will try and create a video to show what is hapening. Then all can chime in for suggestions...I'm all open.

thanks,

JR Gautreaux

lov2flyrc

My Feedback: (24)

JR,
What you need to do is plug [link=http://horizon.hobbyshopnow.com/products/description.asp?prod=HAN172]THIS[/link]
between your battery and RX and measure you current draw. You will probably find an excessive amount of of current being drawn on the system. You can isolate which servo(s) is causing the problem by simply unplugging them one at a time. Everyone should be using one of these units during initial setup to make sure there is no excessive system draw from servo binding/over travel. I run 4 8411 for the flight controls on my Euro and never see more than 1.5A static regardless of how fast I move the sticks. BTW.... I have 18 Guage servo leads if you need them!
Todd

jetflyer

My Feedback: (5)

Todd,

I ordered your "THIS" recommendation and it is on it's way. I'm going to leaving everything alone until it arrives so I can see what the problem may be. It will be interesting.

thanks,

JR Gautreaux

lov2flyrc

My Feedback: (24)

JR,
Good move..... you will be amazed on how much you can adjust the current draw on the system with it. just a few points of ATV over travel on a retract valve can add substantial draw to the system! You will immediatly see what I mean when you plug this unit in

Let us know what you find
Todd

jetflyer

My Feedback: (5)

The device should arrive on Wed. and I will certainly post what I find out. Good point on the ATV, that might be was is causing my problem. But I will wait until the unit arrives before I go changing things.

I actually ordered 2 of them, one for me and one for another buddy.

JR Gautreaux

sirrom

My Feedback: (4)

Todd,
Out of curiousity what is the maximum current draw you should see on a servo when setting up a plane? You mentioned 1.5amps but is that for all the servos moving at once or is that just one. Excuse my ignorance but just curious.

Patrick.

jetflyer

My Feedback: (5)

Patrick,

I believe our RX's can handle up to 18 amps. The actual amps you see in your system will depend on your servos and the number of them that you have. I know some giant scale guys are seeing 4 amps. One guy was using Duralites and I think he commented the Duralites are rated at either 6 or 8 amps. He was running dual packs and regulators so he could deliver up to 16 amps of current if needed. I might be wrong, but I think that is what he was saying.

I'm really curious to see what my system is going to read out.

JR Gautreaux

seanreit

My Feedback: (60)

Under no load with all digital servos in a typical jet setup, you should be reading max .3 amps per servo under no load sitting at neutral. At max deflection max load you should be reading less than 1.5 amps. I found that an 8411 at 95% max load carried a 1.5 amp draw.

I agree with Todd, it's likely the setup and not the leads. He is absolutely correct in that a few % in ATV can change your max current draw so dramatically you might not believe the numbers till you see them. A good dramatic example is on my isobar I was reading 1.3 amps at max deflection no load at 150% travel. Changed travel to 140% and reading .6 amps no load. It was a pure mechanical bind that really wasn't determinable without the load meter as the 8411 just pushed right through the mechanical bind cause it has so much power.

You can not KNOW what's going on with binding without a good ampmeter. It's critical guys.

Sean

lov2flyrc

My Feedback: (24)

Patrick,
I cannot give you a diffinitve answer to this, It will really depend on each servo and what that servo draws at Idle, max load and stalled load. If were talking 8411's, sean is 100% correct on his #'s.... aprox .03 under no load and around 1.5amps under max load. Stalled these servos can draw upwards of 2+ amps per servo! Now idle draw can vary a bit depending on surface load/weight ... IE: some surfaces may apply some load to the servo to hold neutral (like a flying stab)..... These may raise the idle current load a tad. You can also plug the above mentioned device between the servo and rx to measure draw of a specific servo as well...
Todd

747drvr

My Feedback: (5)

I'm just going through this thread and there definately are issues with this set-up. He was using a 3000 mAh pack which should hold its voltage well under load. When the sticks were moved quickly ( speed of stick movement shouldn't make a huge difference ) the voltage was drawn down to 3.8 v or .95v per cell ! There must be a VERY large load to do that. An ammeter will be very telling.

Another issue with his set-up is paralleling a 4 cell pack to a regulated 5 cell pack. Without going into great detail , the packs should be close to the exact same voltage to properly utilize this technique.

Let us know your findings with the amp test.

Marc

bcovish

My Feedback: (8)

Has anyone checked the load on the flap servo on the KingCat in the up postion? Just curious since the flaps are large.

Thanks,

jetflyer

My Feedback: (5)

Marc,

I am going to end up eventually with the same size RX battery packs, just need to figure out after my test if I will go with two 4.8v or two 6.0v with 2 regulators. I was just trying to sort my problem with the availble packs I had in the shop.

JR Gautreaux

747drvr

My Feedback: (5)

Gotcha ! Have you tried trouble shooting as Todd had suggested by isolating individual servos ?

Marc

jetflyer

My Feedback: (5)

Marc,

I am waiting for the Hangar 9 Digital Servo & Receiver Current Meter to arrive tomorrow. Then I will do as Todd suggested and test each servo out individually and adjust my ATV to achieve an acceptable current drain. I could mess with my system now, but I want to wait and see what the device shows first.

JR Gautreaux

747drvr

My Feedback: (5)

Good idea !

Marc

jsnipes

My Feedback: (3)

Bob-O, I posted some numbers on the KC flap servo for both 8611's and 2721's. Look back in the messages, but I think I remember measuring about 300mA with the 8611's in the up position and about 200 - 250 mA with the 2721's. This is mA per servo, not combined. Both were higher than once might expect, but there is a load on the servo with the KC flap in the up position, as you are probably aware but others might not be. I could get as high as 850 mA or so with both of them when intentionally binding the servo by adjusting the travel volume too far or by pushing the flap with my hand.

I'm flying with the 2721's with no issues after 12 flights. The 2721's are quite a bit more "spongy" than the 8611's, but then again there is a large difference in torque. If it means less risk of losing one in flight, I'll stick with the sponge!

Marc, I agree with you ... something sounds wrong about that setup. JR, have you load tested the battery with a 1A load and read the voltage? It almost sounds like you have a bad cell. After re-reading your post it looks like you had the issue on more than one battery pack so that probably isn't it. Something is amiss. 5 servos is not much of a load for a 3000mah pack to handle. It's "the norm" to have that or even more in giant scale aerobatic planes.

Good luck ... let us know what you find.

Jamie

bcovish

My Feedback: (8)

Thanks Jamie

I have no issue with the 2721's either, but just wondered about the load since the flaps are so large. My KC has about 25 flights or so. No problems whatsoever except the (2) times I did a gear check while the plane was sitting on the ground. A least I didn't do it on the same weekend.

Thanks again