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Old 03-22-2020, 04:58 PM
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Servo?

Hello,
I have a fairly new Futaba S9303 servo that Iím using for throttle on a large bi-plane, my question is will it handle a 6 volt system.

One note ::: in the specs it shows 99 ounce in. torque at 4.8 V, but doesnít list what it does on 6 Volts.
Know itís just for throttle but donít want to ruin the servo motor.

Thank You for all thoughts
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Old 03-22-2020, 05:04 PM
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The 9303 was an older analog design only rated to 4.8 Volts ..... 4 cell nixx battery supply. Some guys ran them on 5 cell nixx power (6V +) and got away with it. I know a friend of mine ran them for years on 6V with zero problems and I ran them in one plane for awhile with good results. Not recommending 6V, just saying some people accepted the risk and did it w/o problems. Draw your own conclusions. They were a good servo in their day.
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Old 03-22-2020, 05:56 PM
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Thank you Truckracer.

Believe it or not using 2 packs 2 switches with nicads 5cells. 32 flights no issues... knock on wood.
Also just thought of it.....in a 27 pound quarter scale Plane I used the old Futaba S 29 servos for about 10 years with no problems.
Do know there’s nothing guaranteed, Will due diligence on preflight like always
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Old 03-22-2020, 06:06 PM
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My only complaint about those servos was the #1 gear that was very fragile. A common problem to many Futaba servos at that time, you could just bump a control surface on the ground and strip that gear. At one time, maybe still, you could buy those gears in packs of multiple gears. I never saw one fail in the air though.
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Old 03-22-2020, 06:34 PM
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Great info, thanks.
Assume the #1 gear is the top gear, never opened it though.
Being able to hurt a servo like that while on the ground is pretty scary.
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Old 03-22-2020, 06:49 PM
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Quote:
Originally Posted by rpw612 View Post
Great info, thanks.
Assume the #1 gear is the top gear, never opened it though.
Being able to hurt a servo like that while on the ground is pretty scary.
The #1 gear is the small gear that runs against the motor pinion.
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Old 03-22-2020, 06:59 PM
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Oh, very good, thanks
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Old 03-22-2020, 07:21 PM
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The servo will fail in time if it’s really a large plane (70cc plus)) I have had several servos give out on throttle from hi tech to jr8611....its all in your set up if you have it mounted back a ways and are using nyrod linkage you’ll be ok but if your putting it next to the engine with a metal rod and ball links it will eventually fail.....
Full disclosure I mount the servo next to the engine and use the metal rod with ball links....getting tired of replacing servos.
Good luck
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Old 03-22-2020, 08:39 PM
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Mounted in fuse about a foot away with the blue w/ yellow insert nyrod. Ball link on throttle and 4/40 Dubro heavy duty clevis attached to servo.
Maybe the throttle servo next to the engine in the engine compartment makes a difference because of vibration.
Comments appreciated.
Thank you rcalb.
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Old 03-22-2020, 08:50 PM
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The main cause of throttle servo failure is over travel causing stalling. No need for that with a gasser as very little power is gained by opening the throttle fully and the throttle plate is quite a ways from fully closed at normal idle. With that in mind I haven’t seen quality servos fail at a higher rate than on any other function.
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Old 03-22-2020, 10:26 PM
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Truck that makes sense, using a da 150.
overthrowing a servo would definitely where it down, no matter for throttle or any other function
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Old 03-31-2020, 03:58 PM
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If you have a large biplane and all that work and money on it, don't you think you could update your servo ? Just asking. Makes common sense, don't you think ?
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Old 04-01-2020, 06:51 AM
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Quote:
Originally Posted by Truckracer View Post
The main cause of throttle servo failure is over travel causing stalling. No need for that with a gasser as very little power is gained by opening the throttle fully and the throttle plate is quite a ways from fully closed at normal idle. With that in mind I havenít seen quality servos fail at a higher rate than on any other function.
Cannot over-stress this enough! Well said.

If you set up your travel for full wide open throttle, as the airplane motor is chugging at way, at full throttle, there is so much vibration and movement, of the motor against the motor mount and firewall, that, even 1 mm of movement is putting so much stress on the servo. So doing what TR is saying is the best. The butterfly does not have to open such that it is 100% open. You can set it to 90% and performance is the same.
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