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HomeAircraftHelicopterGasser Model RC HelicoptersOther › Predator Gasser Goes Down Due to 8700G Failure
04-02-2005 03:53 AM  13 years agoPost 1
JKos

rrProfessor

Redondo Beach, CA

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A flying buddy of mine called today from the St George, UT, fun fly and said his PG went down after the JR 8700G tail servo failed and the heli went into an uncontrollable pirouette. The heli and electronics are less than one gallon old!

Luckily he set it down level on the ground but the spinning made it tip and caused a boom strike. The damage could have been worse. The typical crash kit parts and new main and tail blades should do it. And of course a new tail servo, too.

All right guys, what tail servos are actually working on gassers? We keep hearing of 9254 failures and now 8700Gs. How is the 8417 holding up? 9251?

Thanks,
John

RR rules!

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04-02-2005 04:28 AM  13 years agoPost 2
Jim Patterson

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AREA 51 Roswell

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I recently had a 9252 fail on a gasser. It wasn't the servos fault. It was all mine. I was doing the final set-up and programming while keeping my wife company watching TV. I had not set the limits on my gyro yet , and was turning the heli 180 degrees to set linkages, etc. The gyro was in heading hold, so as I turned the heli the servo went against the stop and stalled. I did not realize this until I touched the servo. It was very warm. I quickly cut power and let it cool. After it cooled, I set the limits on the gyro and tried it out. Seemed to work fine. Next day at the field I was hovering only (new heli, etc.) I finished a tank and set it down. Later I refueled it and picked it up into a hover. The tail started left and I had a hard time holding it with full right stick. I quickly set it down in time to see the servo literally go up in smoke. From now on the first thing I will set on a new heli is the gyro limits. Make sure your gyro does not overdrive the servo. Digitals draw a lot of power and generate heat anyway and even more so if they are stalled.

Jim

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04-02-2005 07:18 AM  13 years agoPost 3
Gearhead

rrMaster

Vt

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I have read about the 9253 and 9254 failing,,,

I had two 9253's fail on my Falcon 50 ( Futaba 401 gyro),,, but I'm now 99.99% sure it was because of the way I had my tail linkage adjusted,,, so I have been wondering if a lot of people are not setting up their tail linkage right,,,

I was using the Futaba long servo "arm" with the ball at the end, my Tx settings in HH for both servos were in the mid and low 50's, if I lowered my Tx settings below the 50's my tail would always drift left (nose right), so I know my servo's failed because they constantly needed to hold my tail from drifting left,,, what I should have done was lower my Tx settings and adjust my tail linkage to stop the drift, keep lowering the Tx settings and keep adjusting the tail linkage until the tail stopped drifting left or just started to drift right, then set the Tx to hold the tail in a wind,,, what do you guys think ??

Jim

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04-02-2005 07:22 AM  13 years agoPost 4
bigalsjets

rrApprentice

Retford Notts UK

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Hi 1heliman

I too had a 9254 fail on my Pgasser ,but it stopped working just as I landed so was lucky. I think it must be the vibration that caused it as I did set the limits up ,I have about 5 gallons through her so I assume it lasted well. I have used 9253 and 9254's on several Raptors without any problems so I am puting it down to engine vibs, which probable means that my engine is not tuned correctly and with the servo being on the tail boom it shakes alot on start up.
I am looking at the servo front conversion in future to see if this sorts it out. These servos are to expesive to keep wiping out. If you find a servo that can stand the test please let me know


thanks

Al

Never eat yellow snow!

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04-02-2005 01:43 PM  13 years agoPost 5
Foxden

rrElite Veteran

Port Charlotte, FL. USA

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John,

Do you know if most of the failures that are occuring have the tail servo mounted on the boom?

I've moved the servo's up inside the frame with the tail relocation kit on both of my P-Max's and my Gasser and haven't had any problems, The P-Max's have 9253's and the Gasser has a 9254

Maybe boom vibration is causing some problems?

Clyde

Clyde Fox
Port Charlotte FL
Team Outrage

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04-02-2005 03:53 PM  13 years agoPost 6
JKos

rrProfessor

Redondo Beach, CA

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This one was mounted up front.

- John

RR rules!

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04-02-2005 03:57 PM  13 years agoPost 7
MrDHEJ

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Taylorsville, Kentucky, USA

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9251 front mounted with 6 gallons on it, about 18 hours.

Never go full retard!

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HomeAircraftHelicopterGasser Model RC HelicoptersOther › Predator Gasser Goes Down Due to 8700G Failure
04-02-2005 04:24 PM  13 years ago •• Post 8 ••
wolfdad

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Southern Maryland

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John,
Count me in on two 8700G failures on my Intrepid, one having failed last October at Virginia Beach, prior to a flight and the second failing about a month ago just after lifting off into a hover. After one full rotation, I was able to get the Intrepid down with no damage. Neither of the servos gave any warning of impending failure and, both were being used with a JR 500T ring gyro. Configuration was the Bergen push/pull control system and, in both cases, the servos had prior successful flights. On the second failure, I was attempting to get my RevLock dialed in and did have some head speed issues (high), however not of any length in duration. Of note and possibly of interest, two flights after the second failure, I developed an almost complete crack in the tail boom around the circumference just aft of the horizontal fin holder. Chris has the tail boom and it appeared to have been a fatigue crack from vibration, althoough I had no noticeable fin buzz or HH problems prior to discovery of the crack and the second servo failure. I have now reconfigured my Intrepid with the heavy-duty gearbox and heavy-duty boom, both out of the Bergen EB conversion kit, but at the stock Intrepid length.

I honestly cannot make "heads or tails" of both servo failures, however, my "gut" feeling is that has something to do with a high frequency vibration that is not evidencing itself or at least not enough for me to see. One additonal item is the fact that, in both cases, I was flying with the Hanson 3D Max Pro engine and with a 13T pinion which I am now getting ready to drop down to an 11T to get more into the power band with this engine.

Maybe some of this will help, but right now, my answer would be "duhhh, I don't know." John, Alderman is out in Utah as I write this and I just spoke with him by phone. If you can get in touch with your bud, you might want to get him to talk to Greg regarding this issue since he also has a good bit of experience with the gasser and was with me on both failures I experienced.

Doc

"There are those who have...and, those who will" IRCHA #2117, AMA #70068, Turbine Waiver #105

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04-02-2005 10:16 PM  13 years agoPost 9
Jim Cimino

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NE Pennsylvania

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I have 8700G's on all my heli's including my Spectra-G and have never had a failure without warning. Ususally they start to get hot during flights and that is the time to send them back. One thing to check is battery voltage. The first thing to go when the voltage gets low is the gyro.
Jim

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04-02-2005 10:48 PM  13 years agoPost 10
Al Magaloff

rrMaster

12,199 Posts- Enough Time Wasted. See Ya!

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What gyro are we talking about?

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04-02-2005 11:48 PM  13 years agoPost 11
JKos

rrProfessor

Redondo Beach, CA

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Sorry, forgot to say that it was being used with a G500T.

- John

RR rules!

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04-03-2005 12:29 AM  13 years agoPost 12
wolfdad

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Southern Maryland

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John,
We may have a common denominator here....both of mine failed while working with a JR 500T.

Doc

"There are those who have...and, those who will" IRCHA #2117, AMA #70068, Turbine Waiver #105

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04-03-2005 12:33 AM  13 years agoPost 13
Ted Toth

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Myrtle Beach S.C.

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both of mine failed while working with a JR 500T.
Do you think this is a related issue?


.

You don't stop laughing because you grow old, you grow old because you stopped laughing.

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04-03-2005 01:06 AM  13 years agoPost 14
Christopher J

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Kansas City, MO Californian lost in land of Oz

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On a Bergen Observer I fly for Aerial Images I had the 9254 shoot craps on me today while shooting video. Got it down in one piece and only suffered a broken tial yoke, links, and tail blades. It has a 401 on it.

I've been told I could use one of Hitechs rudder servos and I shouldn't have this problem again. I'm strongly considering running what I run on my Benzin which is a Futaba 601 w/ 9251.

Christopher J
same as I ever was
"Still all set & Flying the original"

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04-03-2005 04:27 AM  13 years agoPost 15
Chris Bergen

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cassopolis, MI USA

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Chris,

Did you resetup the servo linkage like we discussed earlier?

Chris D. Bergen

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04-03-2005 03:18 PM  13 years agoPost 16
Jim Patterson

rrApprentice

AREA 51 Roswell

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I have had two 9202's fail also, one was on elevator, one on the rudder.
After analyzing the problem, the failure is the start winding(or start circuit) in the motor. If you move the transmitter stick and the start the servo by hand it will continue to work until you stop. It will then fail to restart unless I give it a nudge by hand. I talked to Hobby services about this but they had "never heard of this problem". Out of curiosity, I swapped servo motors in the 9202 and the problem went away. So, imho, the weakness seems to be in the motor construction and is definitley vibration related, again just my opinion.
Jim

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04-03-2005 03:30 PM  13 years agoPost 17
wolfdad

rrKey Veteran

Southern Maryland

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Ted,
Just from the stuff I've read in this thread, the 500T and 8700's are the only "common" denominator I've seen. Could just be pure coincidence and JR with JR should not present a problem, however.........one has to consider the possibilities. Both of my 8700 failures had prior successful flights with time both in the HH and normal modes of operation with no errant tendencies (I trim my aircraft to hover in normal gyro mode with the tail as close to dead still as I can get it, then, while in HH mode, I know the gyro is not consistently fighting an out of trim condition). And, as stated previously, both failures came with absolutely no warning....it was there, then it was gonzo.

After I get the chance to talk to Chris later today, I may follow his lead and switch to a 601/9251 combination.

wolfdad send....

"There are those who have...and, those who will" IRCHA #2117, AMA #70068, Turbine Waiver #105

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04-03-2005 08:24 PM  13 years agoPost 18
AGRAV8

rrProfessor

Mosquito Coast......Houston Texas

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Interesting
I am putting a stretched gasser together now.....and I deliberated last night on the 500T/8700G that I had intended to run in it. I have a 601/9251 on standby now. Also, a 401/9254 ready to step up to the plate.

You guys are making it hard to decide. I have an 8417 servo as well, but I think those have already shown they are not up to the task behind the 500T, correct??

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04-03-2005 08:49 PM  13 years agoPost 19
wolfdad

rrKey Veteran

Southern Maryland

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This all could be coincidental, however it would raise enough questions, from my standpoint, to go with one of the other combinations.

wolfdad sends....

"There are those who have...and, those who will" IRCHA #2117, AMA #70068, Turbine Waiver #105

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04-03-2005 09:54 PM  13 years agoPost 20
sgt1959

rrApprentice

Easley SC

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agrav8
I had a 500T and 8700G go on my predator gasser was hovering great and all of the sudden the tail just let go turned out the 8700 motor stopped working now I have a gy502 and 9254 im my gasser might step up to 601 and 9251 later

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