BobCat Elevators
 

I am finishing my BobCat and I have two questions/problems:
1) The elevator servos do not travel perfectly in synch. I am using JR 3301's with a 10X transmitter programmed for dual elevator servos. I can get the center and endpoints matched up but they seem to travel at different rates, with one servo lagging in the middle then catching up. The linkage geometry is as good as I can get it. Does the Matchbox solve this? Or is this even a problem? I have used dual elevator systems before without any problems. I guess I just never noticed the difference since the elevators were farther apart.
2) I have never used a gyro, but I have heard lots of rumors lately. Which one should I buy?
Thanks for any help.

BobCat Elevators
 

Spence,

What you are describing is normal. Once verything is set up I would go to screen 24 (servo speed) and dial down the speed of the faster servo until they travel very close to the same speed. I want to say I have one servo set at normal speed and one set at around 271 degrees for the two servos to travel at the same speed.

John Redman
Team BVM, Jet Cat USA, Shutlze Chargers

gyro
 

Roger

Check with Kevin W. about a gyro. Kevin is having good luck with the one he is using. I going to use the same one.

BobCat Elevators
 

One of my elevator halves travels farther than the other. No noticeable issues with this. Thought I'd see a change when pulling up hard, like in a loop. No problems. Also, I flew mine 5 times before installing gyro. Not really sure it's needed. If you want to test fly over here in Dallas, let me know. We have a new field east of Denton.

Good luck with it.

Mike Jensen

Re: gyro
 

Bob,
What gyro is kevin using?? Almost lost my BC last outing when the JR460T locked the rudders at full deflection :stupid: Somehow...I managed to get it home safely.....

Todd

BobCat Elevators
 

kevin is using the gya 350

http://www.futaba-rc.com/radioaccys/futm0807.html

i'll let him elaborate on the way he has it set up. an automatic "heading hold" kicks in that you want to avoid.

Re: Re: gyro
 

Hey Todd - what rudder servos are you using, how many cells in your battery, and are you using a regulator (if so, what voltage).

David Reid, Vernon, and myself all had this full-deflection problem happen with 3421 servos and an unregulated 5-cell pack. Installing a regulator seemed to cure the problem, and then shortly after that BVM started recommending a different rudder servo - perhaps partly because of the above issues, and partly because BVM rep Harley Condra managed to melt his servos.

BTW, I have the 450, not the 460 - not sure what DavidR et al had.

You might also want to look at what gain you are using. Following our full-deflection issues (discussed here at great length on at least two different threads), a lot of people were recommending backing away from the very high percentage gains that were common at the time.

Gordon

BobCat Elevators
 

FWIW, I am using JR 8417 servos on my rudders in the Bobcat and the old JR 450 gyro. Settings are 5% rate for gear up and 60% rate for gear down.

Also running 2 1700 mah 4 cell batteries wth regulators.

John Redman
Team BVM, Jet Cat USA, Shultze Chargers

BobCat Elevators
 

Gordon,
I hear ya and remember that thread well! This was not a servo lockup but a gyro lockup. Here is what I have installed:

JR460T Gyro
JR8411's on rudders
5 cell 1800mah receiver pack
MH 5.2volt regulator

I am running about 40% gain gear down and 0% gear up. The gyro went full left deflection with the gear in the UP position?? I did have some concerns about this gyro since I would have to sub-trim the rudders every day I went out, depending on the temperature the rudders were always out of trim either to the left or right. Once trimmed for the day all was fine. I was performing some low speed vertical snaps just before the gyro went south, once the rudders went full deflection the plane snapped on me several times in level flight. I fought the snaps trying to get myself lined up to land. I then dropped the gear and the rudders centered and allowed me to land. With the gear up the gyro deflects full left, gear down it is fine. Last time I will be using a JR Gyro :-(....
Todd

BobCat Elevators
 

I have two 5 cells with regulators. 460 gyro, 0 gain at wheels up and 35% wheels down. using the original BV recommended servos. 35 flights so far and no problems.

Mike Jensen

BobCat Elevators
 

Hey Todd;

I do not want to insult you, but when you turn on your plane you must NOT move the plane for a few seconds. That time allows the gyro to find center. If you turn the plane on and move the plane or bump it in any minute way, your trim will be changed every time. This MAY be part of your trim problem. (Some Peizo gyros drift due to temp and loose mounting too)

My Bobct has a dutch roll on take off. Right after the gear is up, it flys great. On windy days, I need almost 100% gyro gain to stabalise landings.

Also, I had the same problem on my elevators servos NOT tracking well, it showed up in loops and pull ups. I ended up with gluing a half an inch tab to the bottom of the faster elevator (one elevator side only) at the trailing edge. That allowed true tracking when moving up.

BobCat Elevators
 

I never can remember that number for some reason. :D

This gyro uses the ATV on the controlling channel to adjust the gain (from -100% to +100%), the AVCS (futabas goofy heading hold function) kicks in when the ATV on the contrilling channel goes anywhere above +60%. You want to make absolutely sure that the AVCS is not able to come on!!!!!!

I have mine set to go to as much gain as possible without AVCS coming on (probably about +60%) when the gear is down, and 0% gain when the gear is up. The gear channel is Y'ed to the gyro to control gain, this creates problems since it is neccessary to adjust the gain of the gear channel to properly control the gyro, but then the gear servo will be out of adjustment for proper throws to move the retract valve. I had to experiment with servo arm length and linkages between the retract servo and the retract valve to get it to operate correctly without binding. This would not be a problem if you were to use a seperate channel to control the gyro gain. If you have a radio that allows you to disable switches you could mix the gain control to the gear channel and not even have to worry about any other switch positions, my radio (PCM10SX) does not have this function so I chose to use a Y and avoid complicating my preflight and landing checklist.

BTW, for what it is worth I am using 9011 servos on my rudders and a single 4-cell (2400 mah) battery pack.

BobCat Elevators
 

Ehab,

No insult here :-). Yes, I am aware that you have to pause during power-up for the gyro to find center. Problem is, center was never the same from day to day and I always had to sub-trim the rudders for first flight of the day. The gyro is securely mounted as well. This is definitely a defective gyro.....

Todd

BobCat Elevators
 

Todd,

Other than the PITA setup of the GYA 350 and the gain which is limited by the useless AVCS on the upper end of the scale I have been very happy with it's performance. It centers perfectly ever time, even with the huge variations in temperature that Texas weather requires us :D to fly in. I have around 60 flights on my Bobcat with no (knock on wood) gyro problems.

BobCat Elevators
 

Thanks for the info Kevin, I ordered the 350 on moday so I should have it soon... Hope this eliminates all my gyro issues :-)

Regards,
Todd

Bobcat
 

I had the JR gyro for the first 5 flights in my Bobcat, I had problems with it centering(I had to keep trimming the rudders before each flight), I tried different gain settings with my radio but it did not seem to correct it, I switch to the Futaba gyro and use the same settings that Kevin is using and have had ZERO problems with the rudders.
I did have an experience this past weekend that concerned me. I did a level high speed pass over the runway, when I got to the end of the runway I went to pull up and I had to pull the stick all the way back to get the plane to respond. I have read in other posts that a few Bobcats have been lost to elevator failure, I also talked with Kevin, he has the same experience pulling out of a dive. Has anyone else experienced this?
I am going to switch to JR9411 servos on my elevators, These are higher in torque(82oz vs. 56 oz with the JR3301)and they also have metal gears. I just don't want to lose my Bobcat to servo failure, I enjoy flying it to much.
Roger you will love the way the Bobcat flies. Post some pics of your Bobcat when you finish it so we can see it.
David

BobCat Elevators
 

Getting full gain without heading hold from the GYA350, or any other Futaba gyro is quite easy.

If the gain control channel is set to -100% you get 100% gain in normal mode. Set the control channel to +100% and you get 100% HH gain. Set the control channel to 0% (the center position) and you have zero gyro gain.

If you want 50% normal gain, set the gain control channel to -50%.

If your radio displays the channel output as 0% to 100% instead of -100% to +100%, then the gain would work like this:

Radio
Settingʰʰʰ Gain
===============
0% ʰʰʰ 100% normal
25% ʰʰʰ 50% normal
50% ʰʰʰ 0%
75% ʰʰʰ 50% HH
100%ʰʰʰ 100% HH

BobCat Elevators
 

:thumbup:


Thanks for the tip Phil!!

Todd

BobCat Elevators
 

The problem I had/have is that I am using the retract channel to control gain (two position switch) and without reversing the servo (or changing the mounting and linkage) the gain would only go the the side with AVCS (HH) with the gear in the down position.

I have no problems with the way my airplane is set up and flying now so I don't really want to mess with it, but I do realize now that there are some other options for setting this gyro that might be a little easier.

BobCat Elevators
 

Thanks for all the help guys. I'll let you know how it works out.

BobCat Elevators
 

For others out there, Horst Lenerz's electronic retract valve is handy is this application, use the gear channel to set the gyro gain, and then you program the retract valve, both direction and pulse width, independantly.

df
 

Todd
I remember Tony F. saying that when the rudders deflect full left in flight it's like the Gyro was shorted out or turned off and on again. Similiar to power up before flight. I'm just about done with Bobcat #2, when I went to get servos and another 460t, the price seemed low. The hobby store clerk told me they were being discontinued and didn't know what the replacement would be. I hope someone comes up with a remedy.
Scott

JR Gyros
 

The 460T problem that you all are encountering is nothing new. I bought a 460T when they first came out and almost lost my bobcat to the problem. I put the problem out on here and had everyone swearing up and down that it was ME with the problem and not the gyro, I even had one of the JR Reps that prowl the board saying that it was a superior gyro and that it was probably my fault. Since then I sold both of my 460T's and was lucky enough to buy a JR 450 gyro which works flawlessly.

As far as futaba gyros everyone that I know who has used them has fallen in love with them.

As far as JR products I think they are having some serious problems with quality control. After losing my bobcat to a faulty elevator servo I have gone to hitec. I am not trying to start a flame war but for the company that is supposed to make the best servos and gyros they have been quite marginal lately.

Just my .000000025 worth.

patrick.

Servo
 

Patrick,
What servos were you using and what hitec servo are you going to use?
David

servos
 

David,
I was using what was recommended by BV. Now I am going with the hitec 5945(?) 180oz all the way around. I am also going with flaps on this bobcat so I won't need the gyro.

Patrick.

BobCat Elevators
 

Since we're talking about gyros---What are your thoughts on the JR NEJ 3000 gyro??? I'm thinking about using this gyro in a Sabre I'm building as I have one lying around not being used. This gyro used to be the top of the line JR gyro until the 5000 came out. What do you guys think?????

Kevin


PS---The 5000 is a head holding gyro....The 3000 is not.

BobCat Elevators
 

Last month I asked the tech at Horizon who was working on my trans. about the JR 460 "problem." He stated that he had NOT heard of any "problems" with the 460. When I described what I had been hearing, he dismissed it as typical internet rumor. He said he uses the 460 in his planes.

My 460 still seems to run just fine (knock on wood)

Mike Jensen

BobCat Elevators
 

Mike,
With the confirmed loss of at least 2 Bobcats to a 460T gyro and almost loosing mine from the very same gyro why would you want to take the chance?

Todd

BobCat Elevators
 

Good question! Did not really follow that thread. I was too busy on a new project and a new house to think about the bobcat gyro thing. The new one (a Mig) does not have a gyro. Not sure they are worth the risk. I think I'll just go back to flying the Bobcat w/o a gyro. It worked fine for the first 5 flights before I installed it.

Thanks

Mike

BobCat Elevators
 

I have somewhere around 300 flights on my Bobcat, several different gyros, and several different servos on the rudders. The last 200 flights have been with the third 460t gyro and have been flawless. If you test the gyro throughly using a hairdryer as a heat source you should with no thermal drift you should be ok. That being said if I were building another Bobcat right now I would install a Futaba gyro in it.

BTW when the gyros went out on my Bobcat It never exhibited the tendency to snap on me. It yawed very hard to the direction it failed, in every case to the right (I had 4 different gyros fail.) Full deflection of the surface. Must be my superior piloting skills though.....:rolleyes:

BobCat Elevators
 

Were ther any bleachers on the right as the Bobcat tried to pull to the right?

Mike Jensen

this is for DC1163
 

For the record, I lost my BobCat XL with elevator non-response (failsafe hold, I guess) a few weeks back - seemed to be having the same problems with elevator response that you are. I was having problems sometimes getting it to respond to elevator commands using the recommended 3301's - it would act like I had switched to low-low rate on the elevators when I hadn't done anything. I wasn't able to completely isolate EXACTLY when it happened, but it seemed to be fairly random and seemed to sometimes happen when I did a low pass (1/2 throttle or so) and started pulling up into a pretty tight turn at the end of the runway while going to full power for climb out (I had a P120 on the BC). Sometimes it seemed to be slow coming around in a tight level turn at altitude, but I kept thinking it was a speed related thing. The BC acted like I only had about 1/3 to 1/2 my normal elevator throw and was so slow coming around I almost bent the elevator stick pulling so hard on it each time it happened. I found that if I backed off the power, it would come on around faster - almost like I was getting elevator blowback which shouldn't have happened using the digital servos. I never did figure out what was happening, so I changed the 3301's out for 9411's for more holding power and torque - just in case I was getting blowback. On the first flight with the new elevator servos, I was about half way through the flight and decided to do a 1/2 throttle, low pass down the runway - like I did before when I had the elevator problem. I lined the airplane up with the runway centerline, let it descend gently to about head height, and when I pulled elevator to level it, NO response - I had NO elevator. In about 1/2 second the BC splattered flat on the runway and self destructed - there was absolutely no indication of an elevator problem prior to the crash. The only real damage was the airframe (all my hardward survived unscathed - thank goodness my gear was retracted and the BC hit pretty flat) but the engine got really hurt. The radio (TX, RX, flight pack, and 9411's) were sent to JR for a complete go through, and everything else was checked thoroughly. Horizon changed the servo gears on one 9411, found a broken antenna wire on the RX (we don't know if it was pre or post crash damage) and pronounced the radio to be perfect after repairs and a checkout. The battery was a 4 cell 1400 mah and was cycled regularly. It cycled just fine after the crash, but JR checked it out also. I'm still flying the radio and RX, and so far haven't had any glitches, but still am not comfortable with the final lockout I got while flying the BC - AND I STILL don't know why it was so slow to respond to elevator commands sometimes. Sure makes me nervous about building and flying another jet (but I'm still working on another one anyway)!!

Hope someone else might shed some light on this issue.

Wish me luck.

Regards, Les

BobCat Elevators
 

About two weeks ago I asked a question regarding unequal elevator travel. Here is the follow-up. After trying a number of different progamming tricks (nothing worked) I discovered that some of the horns were loose. I then redid all of them. Still no success in getting the elevator halves to track together. Finally I realized that one of the halves would not move all the way though its range of motion. After fixing this the elevators now travel in near perfect synch even with just a Y-harness. Sometimes I'm just dumber than I think I am!

BobCat Elevators
 

PS Does anyone know where to get small air tanks- the ones that are only about 3 inches long?

BobCat Elevators
 

SpringAir!

www.retracts.com

Todd

9411's
 

I can't find them. Horizon doesn't even list it. Can someone point me in the right direction?

George

Loss of elevator control
 

Interesting comments about the Les' BobCat. I lost a HotSpot about 2 years ago with identical findings. 2 flights before the crash, elevator commands seemed to be getting soft coming out of loops or reverse cubans. Then on the final flight, after a high speed pass and pullup and 45 deg downline on downwind, no elevator. No bobbing, rolling, pitching....nothing. Went straight in at 45 deg down. It had 8411's on the elevons.

Battery was salvaged and check O.K. Heavy Duty JR switch got trashed, but still functioned. Plane had over 225 flights. 8411's were fairly new, having replaced older 4721's about 50 flights before the crash. Both servos were stripped, but after replacing the gears, worked fine. RX was junk.

My final impression was I lost power to the elevator servos. I was wondering whether a long term high current going to the servos fried the output to the elevon channels, but why both at the same time, or just lost power to everything, but why the soft elevator on the 2 previous flights?

Tom

BobCat Elevators
 

George, Horizon doesn't list them with the number. It's listed under "mid digital". Here's the link though

http://horizon.hobbyshopnow.com/prod...rod=JRPSDS9411

Try Chief Aircraft though, they will probably be cheaper.

http://www.chiefaircraft.com/

Bob

BobCat Elevators
 

Thanks Bob.

Air Tank
 

Roger

Call Dan at Cedar Park Hobbies in Austin. They have the small Spring Air tanks in stock. At least they had some yesterday.

512-331-2943