RunRyder - Predator tail glitch

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Gasser Model RC Helicopters > Predator tail glitch

Bladebuster
Senior Heliman
Location: Bayside N.Y.

Took my new Predator Gasser out the other day to break-in the engine. Everything going good. Hovering a little, then back and forth, not pushing the engine. After flying about one and a half tanks, the heli. suddenly did a 180. Now i have the nose looking at me, and no control. Well, after a second or two i regained control and i was able to land with just a broken landing gear. Very lucky it didn't tip over. This is the first time this has happened to me. The worst part is tracking the problem down. I will be going over the usually things, battery, switch, bearings, servo. Hopefully something will show up. Any suggestions will be appreciated.

04-23-2008 08:58 PM

jschenck
Elite Veteran
Location: La Vista, NE.

which gyro/servo/radio? Did you measure the voltage of the pack afterwords? Was the tail servo case hot?

...yep...

04-23-2008 10:16 PM

lperagallo
Senior Heliman
Location: Westfield, Indiana, USA

That sounds just like a brown out if you are using a Spektrum RX. Been there.....done that....Battery went completely dead on my turbine and because teh FADEC didn't get a radio signal for more then a second, it shut it down and it did a wonderful self landing. Only bent a spindle

Lou

Bergen Intrepid EB, G-26, 720mm; Bergen Turbine, Wren MW54; Raptor 50V2, OS50-Hyper

04-24-2008 02:07 AM

Excalibur
Senior Heliman
Location: Destination: Earth

Hi Bladebuster:

What type of tail servo are you currently using? Futaba 9254's have gotten mixed reviews here. I'm currently investigating the one on my Predator for similar issues. One thing I've noticed (and alot of other people) is how hot they get during a flight. Did this event happen early in the flight or later, like after a half tank or more?

The other thing that is insidious is vibration chaffing your wires. I've been amazed at how fast a servo wire can get damaged from the edge of a vibrating frame, corner or bolt that it's touching. Also, check to make sure your gyro mounting pad is not slipping or coming loose in flight. You'd be surprised how easy this can happen, although it's less likely on a gasser because it's not constantly doused in engine exhaust.

Also, as mentioned earlier, battery voltage that dips too low has been suspected of causing resets depending on the type of gyro you have. How big is your battery pack(s)? You may want to consider a generator to prevent power glitches like this from causing any problems.

Hope this helps - good luck.

Xcal

Camper Fuel: It's Not Just for Breakfast Anymore

04-24-2008 02:15 AM

jschenck
Elite Veteran
Location: La Vista, NE.

If your tail servo is getting hot you'll want to dig in and find out why, it should not get hot. It usually boils down to either some drag in the tail pitch control somewhere or too much gain.

I do wonder if some counter-weighted tail blade grips might help out a lot especially with the large tail blades we run on these gassers.

...yep...

04-24-2008 04:18 AM

Bladebuster
Senior Heliman
Location: Bayside N.Y.

Thanks for the response.
First, about what radio and gyro i am using
JR 9303 on 72mz
Gyro 611 with the 9256 servo
This is the first time using the 611. Normally i use a 411 with 9253 or 9254 servos.
I got a good deal on the 611 from one of the guys i fly with. It's a fairly new gyro.
Upon stripping down the heli. i found two bearings that didn't feel right. One was in the clutch bell. This is sold as one unit. It comes with the bell and bearing block together. The other in the torque tube bearing. I called Century to tell them about the bearings. They said, no problem. Just send them the parts. If they feel they are defective, they will send me new ones.
I also checked the battery, rerouted the antenna wire. I found an NGK plug cap that i forgot i had. Put that on. Trying a different plug. NGK, instead of the Champion. Thinking about getting the Zeal tape for the gyro. Or maybe just doubling up on the Futaba tape. Checked for loose screws. And the last thing i could think of is changing the JR switch. I also found a Super Rocker switch while rummaging through my stuff.
One last thing. Would the rich setting of the engine affect the gyro servo? Remember, i was breaking in the engine, so it was set rich. I also had the gyro in heading hold, if that makes a difference. Just thought that maybe the servo was working harder because the engine was running rough. That's it. Just waiting for Century to send back my parts.

04-24-2008 04:29 PM

Bladebuster
Senior Heliman
Location: Bayside N.Y.

Great service from Century. Sent them parts that i thought were defective on 4/24. Got them back 4/29, no charge. This were the bearings for the clutch bell and the torque tube. They also sent me the old clutch bell bearing, and yes, it was bad.
I asked this question on my second post, no replies. I don't know if anyone saw it. So I'll try again.
I am in the process of breaking in my engine, so i have it set at a rich setting. At this rich setting the engine is running a little rough. Will this rough running overwork the gyro servo? Also does it matter if the gyro is in HH or normal during this break-in period. Just trying to find out what might of caused that tail lockout on my Predator. Right now looks like the clutch bell bearing might be the culprit.

04-29-2008 05:38 PM

AceBird
Elite Veteran
Location: Utica, NY USA

Quote
Will this rough running overwork the gyro servo? Also does it matter if the gyro is in HH or normal during this break-in period.

The engine shouldn't be so rough that the tail wags all over the place. I had no trouble with my 401 during engine break in. The engine will smooth out when you lean it up a bit but you don't want to be in a hurry. How many gallons have you burned?

Ace
What could be more fun?

04-29-2008 05:51 PM

jschenck
Elite Veteran
Location: La Vista, NE.

I use a 601/9251 on my Predator gasser. I have it set in F3C/FAI mode (I don't remember which acronym it displays) not 3D. I run a gain of 42% in Normal mode, 39% in Idle-1 and 37% in Idle-2 as displayed on the gyro. Make sure you have a switch setup to flip it to rate mode, you can check this on the screen as part of the setup.

My initial adjustment is to boot up the gyro in HH mode, bring it into a hover then flip to normal/rate mode. take note which way the nose wants to drift. Then land and adjust the linkage. Do this until there is no drift between normal mode and HH mode. Then flip to HH mode and fly.

Check the tail servo case temp after flying. If it's hot then you'll want to find out why. I don't think the engine kicking will overwork the servo too much as long as the gain isn't too high. My tail stops and holds very well even with the gain at 37%.

do you have a way of measuring the engine temp? If it's running cool you might try leaning out the bottom end just a touch. I've done that and it really helps smooth things out. I'm carefully watching the temp. of the engine at the fan shroud exit and around the exhaust port. Also I'm checking the plug frequently.

The final note is probably the most important. Have you read up on the recent findings and fixes that Billme has posted? Specifically putting the o-rings in the main one-way bearing and adding some baffling to the fan shroud? I have my "predator first aid" kit coming from RHPS right now. Bill assures me this will make a smoother running heli, cooler running engine and he also thinks that the one-way bearing issue may be root cause of some of the predator tail issues such as bearings going out, ect...

...yep...

04-29-2008 07:13 PM

jschenck
Elite Veteran
Location: La Vista, NE.

Oh, also I am using the Zeal tape for my gyro sensor mount. I really like it and one $12 package will cover many gyro installs.

What oil are you running and how much did you mix into the gas? Which gas are you running?

...yep...

04-29-2008 07:15 PM

nicco
Veteran
Location: Sweden

Do you have the servo mounted in the front?

Make sure that the pushrod metall ends, not tuch the screw to the tail boom clamp, it they do, you will have interferance...

/N

04-29-2008 08:45 PM

Bladebuster
Senior Heliman
Location: Bayside N.Y.

Thanks guys. I appreciate the help.
I've done most everything that was suggested.
Yes Nicco the servo is up front, and i am aware of the problem with the push-rod.
Jschenck. For break-in i am using 4oz of Lawnboy. Will switch to two and a half oz. of Amsoil after a gallon of the Lawnboy. Using regular gas. I've been thinking about using the Zeal. Using one piece of the Futaba tape for now. I also just started to read about the fixes from Billme.
Acebird. I've only run 2 tanks of gas. The engine is rich but not rich to the point where the tail is wagging.
Since i found that bad bearing in the clutch bell, i am leaning in that direction, for now. Will change it, and a few other things that i don't feel comfortable with, and try again. I will let you know how i make out. Hopefully it's just the bearing.

04-30-2008 10:37 PM

Makaro
New Heliman
Location: OB,MS-USA

Main Thrust Bearings Installation

Bladebuster,

Did you ever resolve the problem on your bird? I had a similar issue with the tail rotated right on my Predator Gasser. It turned out to be the Main Thrust Bearings were installed incorrectly. The manual shows that the most exposed bearing side rides on the smaller grove half and I had it the wrong way.

Best of luck!

05-15-2008 04:11 PM

Bladebuster
Senior Heliman
Location: Bayside N.Y.

Makaro
I am in the process of redoing the heli. I am waiting for some parts to come in.

05-16-2008 11:45 AM

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Gasser Model RC Helicopters > Predator tail glitch

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