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How about a cheesy rudder servo for excitement?

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Old 09-29-2003, 11:18 PM
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rustyrivet
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Default How about a cheesy rudder servo for excitement?

No fooling here with this question. I'm new to big birds, and want to know what you think of my reasoning:

Why put an expensive digital servo on the Big Bingo rudder. Can't I put a cheesy $39.99 high torque servo on there, and save the $50 bucks to buy a spinner or something else? Seems to me, as long as I put good digital servos on the elevators, and ailerons, thats all I need to get back home if the rudder servo goes broke on me? Right?

Now, I have never experienced a bad servo in flight, and don't know quite what they do when they go broke. I'm hoping you'll tell me they just kind of go limp against the wind? Hmmmm.....don't tell me when they break, they stay in full turn position, do they?? [X(] Don't think I'd want to try to land my plane that way!

SO, JUST WHAT ACTUALLY HAPPENS DURING SERVO FAILURE? HAVE YOU GUYS HAD THE SERVOS FREEZE UP IN EXTREME POSITION? I don't want too much excitement!
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Old 09-30-2003, 10:48 AM
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Default RE: How about a cheesy rudder servo for excitement?

You get what you pay for my friend... If a digital servo fails with a good geartrain chances are it will look in any position but centered. Once you start using cheesy servos you begin to have a cheesy airplane. I don't know what else I can say about this...

-Kelly
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Old 09-30-2003, 02:57 PM
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Default RE: How about a cheesy rudder servo for excitement?

You should be fine with a high torque servo. I can't remember the exact size and weight of the Big Bingo but unless you are seriously overpowering it you should be fine.

My Choice Cut has a 90in. wing span and weighs 19-20lbs. 6 standard servos with smoke and one 1/4 scale servo on rudder. I use my rudder as much as any other control and many times with more than 45deg. of throw. So it does take a beating. For "normal" flying it would last longer but I'm on my third rudder servo and it is about to go also. The rudder is the only one with a long pushrod (should have gone pull-pull) and the vibration from the Quadra 50 eventually eats the pot.

The first two servos were "cheap" Hobbico 1/4 scale servos ($25). The present one is a Futaba 1/4 scale ($40 and big bucks at the time). The failure starts with twitching around center and then quits altogether. When the first two quit they were not locked up, they just quit working and the airstream centered them. I have to add that this plane is more than ten years old and I have never had one of the standard $12 servos fail (futaba and Hitec) other than accidentally kicking the plane and stripping gears.

I'm not suggesting you skimp on radio gear but remember that planes flew fine, and still do, before there were digital servos. Fly what you can afford.
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Old 09-30-2003, 04:52 PM
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Default RE: How about a cheesy rudder servo for excitement?

There is not way to predict what will happen in a servo failure. That's why it's called a failure =) Typically any number of things can happen, From locking up at extreme deflection, stopping responding, totaly flipping out, or going limp. Don't buy a 'cheesy' high torque servo, buy a high quality high torque servo. Digital or not.
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Old 10-01-2003, 07:41 AM
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Default RE: How about a cheesy rudder servo for excitement?

What is your defenition of cheesy, 40 bucks will get you a hitec 645, 133 oz of torque (6v), metal gears, a Fine servo for most applications. for about 7-10 dollars more you can get an mpi 870 100 oz torque (4.8) coreless motor and very fast. I would not call either one of these servos cheesy. What is cheesy is the mindset that if you didnt pay 100 dollars plus for a servo it is a crappy servo. Marketers love that attitude
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Old 10-01-2003, 10:05 AM
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Default RE: How about a cheesy rudder servo for excitement?

SMALL FLY,

For the sake of the manufacturer reps who frequent these threads, I didn't want to mention any names and insult anybody. But when I said $39.99, and you said $40, and the torque figure is exactly the same....... do you think maybe we're talking about the same name servo? Yep, that's what I'm planning on putting on the rudder. If you check the archives here on RCuniverse about this servo, you will find some guys say it's "cheap" ( or my term: "cheesy" ) and it is of simple/crude technology. But of course as with everything else reviewed, there are always those who say "it works great!". I am of the old school though, that with a few exceptions, "you get what you pay for". But again; this is why I intend to put it only on the non-essential rudder surface.

CAUSEITFLIES,
has pointed out to me, he has already had two failures occure with other brands during flight, and his servos just "quit, and the air stream centers them". That's pretty much what I wanted to hear, and eases my mind about using it on only the rudder. The digi's or better grade coreless Futabas will go on the remaining surfaces that are responsible for getting the plane home safely.

Just to make the point as the devils advocate, logic seems to dictate too: that who's to say the top quality $90 servos I will use on the other surfaces can't fail and lock in an adverse deflection? Yes, though I will buy them and use them on most of the surfaces, I'm sure they eventually will wear out and break too.

Thanks guys. You've been very helpfull in educating me on this matter, and helping me to sort out what I will buy.
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Old 10-01-2003, 10:41 AM
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Default RE: How about a cheesy rudder servo for excitement?

Randall.... don't worry if any of your servos (cheesy or beefy ) is damaged while in flight you (and the fellows around you) will get excitement all right by trying to bring the bird down (in one piece.. of course :bananahea)
I think you're reasoning is right.. just get a sturdy non-digital high torque liek the ones smallfly suggest and get the digital$$$$$ on the other surgaces.. and presto you have $40 to spend in a spainner or carbon fiber gear.....
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Old 10-01-2003, 10:49 AM
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Default RE: How about a cheesy rudder servo for excitement?

If it makes you feel better I have hitec 645's on the ailerons and rudders servos and 625's on the elevators on my GP patty wagstaff. I have been flying it 1 year (in 2 weeks) and have well over 125 flights on it (I dont count just guessing) and the servos still function just fine. there centering is acceptable. I have just replaced the metal gearsets in all of them as they were getting quite sloppy after a year. (lot of vibration from the bme 50 on her) but that is a problem with all metal gear servos. I have done blenders and all sorts of 3d with this plane and the servos have done fine. and all for just 39.99 each
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