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futaba servo problem

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Old 04-25-2010, 11:40 AM
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Default futaba servo problem


I have set up a pair of 3003 servos as elevator servos (bird is a mid size gasser sunday flyer arf) after throws and end points set and checked I found when holding full up/down you can move the elevators back aginst the motors through full throws with out stripping the gears, So bad motors? servos are side mounted in the tail long servo arms about 11/8 push rods 41/2. Note this is the secound set of new servos used and same problem. do to limited space can't change mounting with out some major mods to the fuse.

Bob t
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Old 04-25-2010, 11:46 AM
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Default RE: futaba servo problem

3003 servos in a gasser? Do you mean a 40 size sport nitro plane or are we talking a true gasser?

If its a larger gasser than you need decent servos.
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Old 04-25-2010, 03:35 PM
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Default RE: futaba servo problem




ORIGINAL: rt3232 I have set up a pair of 3003 servos as elevator servos (bird is a mid size gasser sunday flyer arf) after throws and end points set and checked I found when holding full up/down you can move the elevators back aginst the motors through full throws with out stripping the gears, So bad motors? servos are side mounted in the tail long servo arms about 11/8 push rods 41/2. Note this is the secound set of new servos used and same problem. do to limited space can't change mounting with out some major mods to the fuse. Bob t
S3003 torque @ 4.8v is only 33oz/in.Calculate the load you place on the servo given the crowbar effect oflong horns/pushrods when pushed by hand - many pounds of pressure as opposed to a few ounces. Pushing back on a servo in such a manner is the fastest way to burn out servo motors (especially digitals).
Gears of cheap under powered servos do shearwithshock, especially flight induced shock (e.g. flutter and the higher vibration of petrol powered motors) and bounce on a hard landing.
Futaba S148 &S3003 Specification and History
101 - Servo FAQ & picking the right servo for the job
See also sub Section "Servo - Alterations, Calculators, Databases, Leads, Repairs, "
and moreunder
"Radio Systems, Accessories, Alterations and FAQ." at:
Alan's Hobby, Model & RC FAQ Web Links



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Alan T.

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Old 04-25-2010, 04:16 PM
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Default RE: futaba servo problem


Ok
This is a new bird and a gasser G-38 and as I said just a sunday fly'r has not been in the air and will not go till I get the servo thing solved. the servos I used are brand new but have been in the shop from back in the nitro days (5 years maybe) just trying to get some thing that will fit in the bays, its an arf, and from what I now see it was not well planed, just nice looking, any way, I still ask the question have anyone had the condition as posted above where you can push the servo arm back aganist the moter with out stripping the gears end point to end point???

Bob T

PS futabas spec says 57 oz@ 6v so with 2 should be enough for the type of flying
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Old 04-25-2010, 04:28 PM
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Default RE: futaba servo problem

Get you some hitech 635MG's or 5625's

Those servos aren't going to cut it on a gasser.
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Old 04-25-2010, 04:45 PM
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Default RE: futaba servo problem


ORIGINAL: rt3232 <snip> I still ask the question have anyone had the condition as posted above where you can push the servo arm back aganist the moter with out stripping the gears end point to end point??? Bob T PS futabas spec says 57 oz@ 6v so with 2 should be enough for the type of flying
Please refer post #3 - Majority of servos can be pushed end to end by hand when under power.
The torque generated by your hand along the rods/horms far exceeds the stall torque of a S3003 @ 6.0v= 57oz - in.
This has been demonstrated in shop and club house on a number of occassions over past 20+ years.
Not only a very fast way to burn out servos, turning by hand can lead to bent gear shafts or elongated sockets in the case allowing for "sticking" points in the gear travel.
Servo - FAQ : Servo Torque (How is it measured) and Conversion Kg.cm <> oz in
Servo - Do not turn by hand

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Old 04-25-2010, 08:25 PM
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Default RE: futaba servo problem

Not to mention stripped gears.
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Old 04-25-2010, 09:19 PM
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Default RE: futaba servo problem


Ok
Guys I am with you but in my 40 years in rc I have never found servos that acted like this, did not move them on purpose, the bird was on my mobil bench I ducked under the tail and raised up to sone while my budy was holding full down and just the wieght at the tail let it go to mid range so then I just held my finger under one side at a time and both servos reacted the same.

Like I said it will not fly with these servos on the elevators, it is now a question of finding some that will fit with out doing surgery (dam ARF's)

Thanks for all of your comments

Cheers Bob T
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Old 04-26-2010, 02:01 AM
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Default RE: futaba servo problem



Teamxcore digital servos maybe can meet your needs, you can check it on www.teamxcore.com, thank you

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