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Jett FIRE 60 LX - 3/23/2006 1:50:41 AM   
huey-pilot


 

Posts: 297
Joined: 7/12/2002
From: Enterprise, AL, USA
Status: offline 		I have a Jett FIRE 60 LX mounted on a Diamond Dust and I am having problems with throttle servo failures. The servos that I am using are Hitec HS 81's and the Futaba 3101 micro. I have had problems with stripped gears and electronics failures. I have the throttle linkage set up like the folks at Diamond Dust recommend but still problems. I would like to stay with micro size but I am willing to try anything that may last. I would like a recommendation of a good servo and throttle linkage set up.
       Post #: 1

RE: Jett FIRE 60 LX - 3/23/2006 2:35:45 PM   
bob27s



Posts: 4637
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline
quote:

ORIGINAL: huey-pilot

I have a Jett FIRE 60 LX mounted on a Diamond Dust and I am having problems with throttle servo failures. The servos that I am using are Hitec HS 81's and the Futaba 3101 micro. I have had problems with stripped gears and electronics failures. I have the throttle linkage set up like the folks at Diamond Dust recommend but still problems. I would like to stay with micro size but I am willing to try anything that may last. I would like a recommendation of a good servo and throttle linkage set up.


Sounds like the failures are more from vibration than loading...

Most micro servos will fall apart under high vibration loads. Most regular servos will too... be careful.

Try the HS 225 servo. Its pretty rugged, and not that much bigger than the HS81.

Be very sure (especially with that engine) to balance the props. At those power levels, you can get a lot of vibration energy entering your airframe from just a tiny out-of-balance condition.

Also, make sure to support the throttle pushrod. Do not run it straight from the servo to the engine... run it through a guide or tube somewhere if at all possible. It will change the loading the servo sees a bit. Id suggest also to add a partial bend or z-bend in the rod somewhere.

Bob


_____________________________

Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to huey-pilot)
       Post #: 2

RE: Jett FIRE 60 LX - 3/23/2006 4:01:39 PM   
rmenke


 

Posts: 1684
Joined: 6/25/2004
From: Merced, Ca., CA, USA
Status: offline 		Bob:

What rpm should my 91L with the 91 LX muffler be turning with a 11 X 8 APC. Motor does not have much time on it, maby 15 runs at the most. New tach says 12800, seems a little shy. Will start cutting the tips down to get normal rpm as needed. Thanks, have not forgotten your picture wants of the Alley Cat.

(in reply to bob27s)
       Post #: 3

RE: Jett FIRE 60 LX - 3/23/2006 4:54:35 PM   
bob27s



Posts: 4637
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline 		Should be up over 14,000 with an 11x8. An LX timed engine will get the prop over 15K rpm

I seem to recall you are not at a real high altitude..... so you should be able to hit this.

Since it has run in the past, been through break-in, but not run much, put an 11x6 or 11x7 on it...... or clip that 11x8 down to 10" dia. Get the rpm up. Any of these will easily get to 15K rpm and higher with an engine with some run time on it. Run it a few times like that... about 500-600 rpm off of peak. Then try the 11x8 again.

Of note, it if is showing that far down on rpm - check the liner installation. Make sure it didnt turn. Look in the exhaust port.


_____________________________

Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to rmenke)
       Post #: 4

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