I am running two 6 volts packs, through two regulators and two switches into two channels. Wonder if mine would be less sensitive to the voltage spikes.

Mike

How about running seperate power wires to the servos and just use the signal wire off of the gyro.

Although my failure happened soon after I added a 6V reguator, IIRC, DavidR and Vernon both had these hard-over failures with an unregulated, freshly charged 5-cell pack. That doesn't seem to jive with the above postulation... Also, I'm already running the heaviest gauge extension leads that JR provides. (BTW, how come they don't provide the servos themselves with heavier duty wire ? ;-)

I know that my hard-over failure happened on the ground while the aircraft was stationary; IIRC, David also had failures on the ground.

Gordon

The regulator is just one of the factors that could be contributing, eh? What about the length and guage of their leads?

Ok guys I'm ready for my first flights on my Bobcat, and this stuff I'm reading is making me a bit nervous. I also have a JR 450 Gyro
and JR 3421's on the rudders, I also am running two 6 volt battery packs thru Elecrodynamic's Powerbacker regulator. Maiden flights are nerve racking enough, couldn't I just leave the gyro out of the loop for the first flights? Have any of you guys flying your Bobcats flown it without a gyro? Is it a must? Just curious

Thanks Jack

Jack,
I flew my first bobcat without a gyro and it can be done. The only thing you have to be ready for is when you are getting ready to land the plane will be rocking back and forth due to the gear doors/speed brakes. This is the reason I went with a gyro on my second bobcat.

Patrick.

Jack,

Don't worry about the gyro. I flew mine 6 times w/o it. Then I added it with only about 15% gain. Not much of a difference because gain is so low! The wiggle on landing is really not much. In fact, I am tempted to just unplug the darn thing and fly it again w/o the gyro.

Good luck on first flight. You will love it. Just remember that it will balloon when you put the gear down if going too fast, so slow it down or be ready for it.

Mike Jensen

I still think we are looking at two different problems here. The first that Vernon, myslef and Gordon expereinced with the servos crapping out, and the second being a gyro issue. Maybe they are related maybe not. I just put the voltage regulator on mine and will be flying it this weekend at Austin with that configuration, I have also programmed in a ZERO throw rate on my rudder rates. If I should have a problem with a hard over (GYRO related) condition I can switch to zero rate on the rudder and land.

I can agree with BMT's analysis of the current spikes but have also seen people with LARGE aerobatic planes with as many as 3 and 4 servos on the rudder with a JR 450 Gyro with no problems like we are experiencing as well. If these digital servos are overloading the wiring in our models what are they doing to the power bus in our recievers as well?

Rdjetflyr, I have an Electrodynamics Pow'rBack'r too and, I am not certain of this, but I do not believe that it has a regulator built in. Of course Andy can tell us for sure. I know there is a voltage drop associated with the unit (that's why if ya wanna use his little voltage checker thingy, you gotta get the one calibrated for use with the Back'r), but I thought that was due to internal circuit resistance, not an integral voltage regulating circuit.

but David I am not sure that zeroing the rates will prevent the gyro from commanding an excursion of the rudder if it is so inclined? The value of the rate (even zero) is probabaly just a variable in the firmware ont he micropcontroller in it??

Errr ummm I was just about to post that. It does not affect the gyro deal. Scratch that idea. Maybe I will add another mix that will turn the gyro gain off, or I can just reactivate the knob. Either way I am going to have a way I can turn my gyro off.

Woketman,

Yes you are correct, I should have said it delievers a constant 5.1 volts to the reciever. It uses .9 to operate according to the instructions. I used the same setup in a Kangaroo and didn't have a problem, of course I just had the gyro on the steering and not the rudders.

Jack

This does not address the gyro issues (I've never used one on a plane, just helis), but my Pow'R Back'R has always been rock solid and perfectly reliable. A quality product.

David,
You made the statement that you were going to set up the gyro so that you could turn it off. How do you turn it off? Did you mean set the gyro to 0 gain?

Patrick.

When my Bobcat is done, I'm contemplating trying to use the rudders as speed brakes instead of the gear doors by deflecting them both inward along with flaperons. I know Bob is trying to keep the airplane very simple, but if I have the capability with the radio.. why not use it?

-Doug

Hi Guys,
Let me just say my postulation posted earlier is just that. I have no experience with using that many digital servos on one system using a gyro. ( I use 8411's and 8417's) I have not tested any of the voltage regulators out there. I am speaking from the viewpoint of general electronic engineering experience, much of which gained designing RC related sytems. These include our own ECU and GSU as well as RX's for long range use in target drones. Our ECU used a switch up/down switching regulator that can work from anything between 2V and 12V for the very same reason. Unless I analyse such a system close up, I would only offer it as a possibility. My main issue is with adding gizmos to a system not included in the design brief of the very good JR R&D engineers. But I hope the issue can be resolved before someone loses another jet. I did not see the impressive twin AMT Rafeale go in at FJ but I heard the very sickening sound of tarmac rash, reportedly due to a similar problem. The solution may be as simple as adding some low ESR high value capacitors in the Gyro voltage regulator circuit to keep the analog amps happy.
The need for good voltage tolerance on the RX is well taken care of on JR's. The RF section works from a regulated 3.3V
Cheers
Andre

Yep, I am going to try butter flying the rudders "out" on my Bob Cat. You can set them up to go in or out and I choose OUT. It takes three channels to implement this setup, one for each Rudder and one for the nose gear steering. I'm hoping they add a little drag and help stabilize the wiggle. I will know shortly as maiden flight should happen this week! Using the 10X I still have an extra channel Aux. 2. I'm using the match box on the elevators. and separate channels for ailerons. Flaperon for the differential capability, and maybe a little flap! All of the extra functions are easily switch able on and off for testing. Also has anyone tried flying the Bob Cat without the main gear doors, they are easy to remove! Drag aside, is the wiggle completely from the doors or are the low profile fins the real cause of the wiggle?? I did vent my gear doors per Tony's solution also. I should know the answers to all of these questions within the next two or three weeks.
Lee -----

Patrick,

Since the gyro gain on mine is set up on a seperate channel I can set up another mix, gryo gain to gyro gain, and set the mix value as zero and activate it with the mix switch on my 10X (back right corner) and with the switch on have it as 100%. I think this wil make it where if I flip the switch off it sets gyro gain to zero. I will try this tonight and post if it works or not.

David, if all this works for you on setting up the Gyro and all, if you have the time and data safe, could you put the program on a floppy and bring this weekend to Austin? I realize the time is your enemy right now.

Bob,

If you only knew........!!!! I will try to do it, if I don't I will have my notebook with me to download flight info from the JetCat, so we can do it at the field.


David Reid

My reasoning for thinking of going IN on the rudders was to keep the drag closer to the centerline of the aircraft, to reduce the potential yawing effects. I'll be interested to hear your results.

-Doug

Going "in" may cause some pitching effects due to the increased pressure under the elevators. Who knows, the pitch down that may cause could eliminate the possible pitch up effect of the slanted rudder hinge line. Flight test will confirm this. My prediction, you can't move the rudders enough to really make a significant drag increase. Kind of like flaps, 10 degrees of flap hardly changes the drag, 40 degrees causes a big increase.

I have flown my BC without the gear doors. The yawing oscillations were eliminated, but I'm glad I was on the lakebed when I did it. The model just wouldn't slow down, and that was with the idle thrust of a 500.

It seems to me that the fault really lies with the design of the Bobcat. If it didn't snake around, elaborate gyro fixes would not be needed. Maybe BVM should contract Bob Parks to fix the plane.

DAVID,

CAN'T YOU SWITCH THE GYRO OFF FROM AN AUX CHANNEL OR FROM A MIX?? THE GYRO'S I USE COME WITH A SWITCH THAT TURNS THE POWER OFF TO THE GYRO. YOU CAN PUT THE SWITCH TO AN AUX CHANNEL, OR MIX IT TO ANOTHER ACTIVATION POINT. I HAVE MY GYRO ON NOSE WHEEL STEERING ONLY, THE GYRO GOES OFF WHEN THE FLAPS ARE IN THE FULL UP POSITION. ROGER HAS HIS GYRO OFF WHEN THE GEAR IS UP POSITION. WORKS REAL GREAT. SOUNDS LIKE U MIGHT WANT TO JUST PUT IT ON AN AUX SWITCH & TURN IT ON & OFF WHEN U WANT.


SEE YOU THURSDAY!!

DAN M.

OK guys, after 130 flights on my last Bobcat my rudder servos were still working without a failure, that was untill I threw the batteries out of the canopy in a couple of intesne inverted snaps. Rates were 10% gain with the gear up, 50% gear down, all done with dual 4.8 volt batteries, a single 950S reciever, both rudders and nose wheel steering coupled into the 450 gyro. Also the gyro adjust was done using the gyro adjust menu (44, I believe) in the 10X radio.

As for the fault lying in the design of the Bobcat, I doubt that. The Bobcat was designed with ease of building and maintenance in mind. Designing the Bobcat without flaps and with the thought of guys using a six to eight cahnnel radio to get it in the air, equalled easier and cheaper for the entry level customer. With that ease comes compromise, believe me I see it in full scale military fighters as well. The main gear speedbrake paddles are needed to slow the bird down during approach and make it easier to land. that brings in the gyro due to the "Karman Vortexes" coming off of them. If we would have had to hinge flaps, add two more servos, etc, complications go up as well as cost.

I am firm believer and lover of JR equipment. Lets face it guys, if everything worked perfect and correct the first time out this would get a little too easy. There have only been a small number of problems/failures in this area. Give JR time and I am sure they will come up with an answer as to why this is happening. Also I am sure BVM is checking into the problem as well. BV is more concerned about sucess and safety than a few guys here might believe. Those of you who know BV, know he is here to support and deliver the best products possibly with todays technology in the model field, without compromise and with all safety concerns as well. We also know JR is commited to the same.


I am still wokring feverishly getting my newest Bobcat into paint by hte end of next week. Probably won't make it for St. George but I am trying.

John Redman
BVM, Jet Cat USA Rep