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Retract Servo problems

Old 04-02-2012, 05:54 AM
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benboy17
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Default Retract Servo problems

I have a hanger 9 Mustang that keeps frying the retract servo. The servo seems to work fine until I get the plane off the ground. I have a futaba fast reciever with a 6v battery hooked up. First flight the servo would not pull the gear up, landed and nothing the servo was dead. Ordered a new hitec bb servo installed it work fine soon as I hit the swith to pull the gear up when off the ground again I had nothing. Landed the plane and again servo does nothing. Any ideas what is going on would be helpful.

Thanks
Old 04-02-2012, 06:59 AM
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MinnFlyer
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Default RE: Retract Servo problems

Make sure the servos will handle 6v. Some retract servos won't
Old 04-02-2012, 07:05 AM
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benboy17
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Default RE: Retract Servo problems

Thanks Minn I did do that and it says it does. That was my first thought
Old 04-02-2012, 07:18 AM
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Default RE: Retract Servo problems

Got any pics of the setup?
Old 04-02-2012, 07:26 AM
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Default RE: Retract Servo problems

I had the Hangar 9 P-47 getting the gear adjusted right is such a pain....... you have got to make sure that you have enough travel to stop the servo once retracted.....I was using JR servos...my retract servo could not handle 6V.....If you want dependable retract operation contact Down and Locked Retracts
Old 04-02-2012, 06:17 PM
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Default RE: Retract Servo problems

This may seem like a dumb question, but are you using an actual RETRACT servo? Specific retract servos have very high torque ratings?
Old 04-03-2012, 05:53 AM
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Default RE: Retract Servo problems

Yeah it is a retract servo. Is a hitect bb servo. Im thinking it might not be going the full 180 degrees. gonna check it out again and make sure
Old 04-03-2012, 06:00 AM
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Default RE: Retract Servo problems

Yea, if the servo binds and isn't allowed to rotate it's full 180, it will burn out
Old 04-03-2012, 06:09 PM
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Default RE: Retract Servo problems

Mechanical retracts can be a headache to install and adjust. You have to get the gear to be fully retracted in both directions and the servo to be fully rotated in both directions at the same time. It can be a hassle to say the least.
Old 04-04-2012, 04:05 AM
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Default RE: Retract Servo problems

Actually its pretty simple to set up. I'm sure Mike has his neat mechanical drawings somewhere.

Measure the stroke of the pushrod on the retract mechanisim from lock to lock.

For simplicity lets say its 1"

Use a round servo wheel and drill holes exactly one inch apart and 180 degrees from each other.

That will give you lock to lock without binding.
Old 04-04-2012, 04:40 AM
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Default RE: Retract Servo problems

Ah that makes sense!!! Ill try that and see what happens. Thank you
Old 04-04-2012, 07:24 AM
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Default RE: Retract Servo problems

Adjustment of the mechanical installation has always been the achilles heel of mechanical retracts that everyone has the most trouble with.

The adjustment that gives so much grief that BH talks about in the post above is the total throw of the pull rods provided by the servo wheel and that is so often looked over because it often is best done by drilling your own holes in the round oversize servo arm blanks. If ya ever wondered what these are for well now you know.

I have often fantizized about a simple factory moulded arm that is double sided and functions much like the hitec infinately adjustable slider that is intended for throttles.

Now what I do want to mention is the simple method of confirming that the gear is fully extended or fully retracted and not bound. It serves well for quick checks before flight or anytime and very easy to do.

To confirm that the gear is fully extended and not bound (servo under load) just lift a wing up a little and wiggle the gear leg. If properly adjusted there will be some free wiggle. Sometimes with the cheaper gears this wiggle even seems excessive but it must be there. If the gear is tight with no wiggle then its not locked and the motor is bound.

Now retract the gear and just give it the same quick wiggle test in the retract position. There must be some wiggle or it not fully in the up lock position and the motor is holding it up.



So in short each of the gears must have a slight wiggle in both the up and downlocked positions or there are going to be problems.

John
Old 04-04-2012, 08:14 AM
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Default RE: Retract Servo problems

To add to what John said, many mechanical retracts will bind if not mounted perfectly flat. Get a pair of hemostats and make sure you're not getting binding when you manually actuate them.

Frank Tiano used so sell some very nice machined retracts with titanium struts that pretty much dropped right into the H9 Mustang and eliminated a fair amount of the retract grief with that plane.
Old 04-07-2012, 07:25 PM
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Default RE: Retract Servo problems

One of the problems with retract servos is the end point is not adjustable making adjusting the linkages critical.

Too slack & the retracts won't move & lock, too tight & you fry the servo.

Spektrum have released a retract servo that you CAN adjust the end points.

http://www.spektrumrc.com/Products/D...odId=SPMSA7000

Could be the answer? - John.

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