Q-500 Racing Discuss AMA 428, AMA 424, and any other variants of Quickie 500 racing

cheap servos

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Old 07-15-2009, 12:17 PM
  #1  
daven
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Default cheap servos

Just about lost a plane last weekend due to a cheap servo. Shut the motor off, prepared for landing, and Poof, no Aileron control.

Thankfully, I was able to land it about 1/2 mile away using rudder with minimal damage.

The servo was a new (roughly 1 year old) JR MN-48 sport that maybe had 30-40 flights on it. The wing was a viper wing, with very easy surface movement, so it wasn't being over stressed.

I was just lucky the servo stopped at complete neutral or I never could have landed it. Not saying these are bad servos, I have used them a bit for 424 type quickies, first one I have failed. Any other issues with these?? I switched it out with a 3121 out of my polecat (R.I.P.) and everything appears to be working perfectly.
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Old 07-15-2009, 12:48 PM
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Default RE: cheap servos

Sure, now you bring it up.. I have 2 of the MN-48's in the V2 I was flying on Sunday..


Here's a pic of the new V2.. aka Fruit Stripes

****** Edited per the request of the 2009 428 Nat's Champion ***************
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Old 07-15-2009, 12:57 PM
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daven
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Default RE: cheap servos

Its Fruit Stripes, not Juicy Fruit
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Old 07-15-2009, 01:09 PM
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luv to race
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Default RE: cheap servos

I gave my speal on this before. And everyone knows that I fly for JR.. so I speak the truth.

That is a perfect sport servo for small type planes. You might get away with them in Club40 or even 424 (maybe?). I still think 424 is pushing it. And certainly a big no no for 428 or 422 planes. The servo was built for the budget minded sport flyer. Not the avid racer.

Randy Bridge
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Old 07-15-2009, 01:18 PM
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Default RE: cheap servos

So Randy, what is the recomendation for servos in the 428 and 422 classes? IMWTK??
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Old 07-15-2009, 02:02 PM
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luv to race
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Default RE: cheap servos

Well.. If you choose to fly JR. I like the 3121's and the 3421 Digitals. Now I know they are $69 to $89 dollars, and that instantly makes people cringe. But I remember before I was sponsored on with JR, I flew HiTec servos like the 225. Someone talked me into trying 2 JR 3121's on my vtail, because I always fighting trim issues with every plan and it drove me nuts. As soon as I switched to 3121's, that trim issue was over...I honestly couldn't believe the difference. I could take the plane apart, hang it on the wall for a few weeks...go fly it and no trim was needed. I couldn't believe how spending a little extra money changed my performance.

So I spent the next 6 months, buying 2 of the 3121's each month...because that was all I could afford. And when I crashed, I could not believe how cheap it was for Horizon Hobby to repair it all. They didn't know me at all, and sometimes my bill for an entire crash pile of stuff was as little as $35 bucks.

just my 2 cents...
Randy
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Old 07-15-2009, 02:14 PM
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Default RE: cheap servos

I am currently flying a Spectrum DX7 and I want to move up to a JR. I am deciding whether to get the 9 or 12 channel. There does seem to be considerable difference. There is an old saying something like you will always complain about the quality of a cheap deal but never about the quality of a quality deal. I will start trying to move up to a b etter srevo. Thanks
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Old 07-16-2009, 06:34 AM
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Default RE: cheap servos

Buy the BEST, and only cry ONCE !!
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Old 07-16-2009, 06:40 AM
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daven
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Default RE: cheap servos

Randy, I know what your saying, I use the good stuff for 428 and 422, but I am always looking for an inexpensive (dependable) servo for the beginners.

Its a hard enough sell to get someone going, and then telling them they need $70 servos when they are use to using $12 standards. I had good luck in our version of 424 with with the Expert SL-451's, which I assumed became the JR Sport MN-48, but now I am reluctant.

I started with mostly Hitec 225's (Like many racers), and even with there centering issues, work pretty darn good for 424. Whenever I build a sport plane, I always have an old 225 to use for throttle now. Going to give the tower equivelents (TS-35s) a shot on my next 424, picked a few up on Towers last sale for $19 each.
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Old 07-16-2009, 08:24 AM
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Default RE: cheap servos

at least your cheap servos lasted long enough for me to cut out before you went on your free flight last weekend.
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Old 07-16-2009, 09:29 AM
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daven
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Default RE: cheap servos

It was amazing that it worked fine for the complete race, and then died the second I shut it off.
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Old 07-16-2009, 10:23 AM
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Default RE: cheap servos

Well, I think you can have bad servos of any type. I’ve had the Futaba 9202, 9206 and a 9402 fail before in models and helis. Funny I can’t recall having the standard Futaba 3004 or the older standard bushing servos ever giving any trouble after many flights. I’m currently using the GWS HPX Mini BB servo in my Quickie 25 and 424 planes with no issues at all. I like them because the cases are clear and you can inspect the gear train without taking it part.

We've had good success with the HS-225 in John’s racers. We tried the HS-81 on throttle but they have failed several times even with a TT Pro .40. The Nelson gave it a hard time also. Yes the digital servos center better but the units I’ve seen used in the big 3D airplane tend to buzz and hum a lot because of their tight centering tolerances. This constant buzzing has to cause some battery drain but with the short time our races are this should not be a problem.

Running these servos on 6+ volts may cause some problem for the amplifiers even if the manufacturer says OK. They are designed for 4.8 volts with a safety factor for surges. 6 Volts I would suspect lessens that safety factor.

I believe that one of the key issues with any servo is vibration. Be it from the engine or possible flutter of a surface. If mounted correctly with the grommets vibration related issues should be greatly reduced.

Bob Harris
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Old 07-16-2009, 11:30 AM
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luv to race
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Default RE: cheap servos

rarely do "cheap and inexpensive" run together with "dependable". I always stuck by the phrase, "you get what you pay for", learned that from experience.

With that being said, I completely understand wanting to save some money. I save as much as I can every day. However...when I drop $500 on my favorite racer, or spend many hours building my $250 dollar kit. I want to do everything in my power to be sure I have the best systems inside to keep it from thumping the ground. So for me it's worth a some extra expense to save my models. I've also had the luxury of watching many types of servos fail, meaning that they all fail and nothing is bullet proof. I just try hard to minimize my risk.
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Old 07-17-2009, 09:25 AM
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Default RE: cheap servos

You get what you pay for.
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Old 07-17-2009, 10:21 AM
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Default RE: cheap servos

I just want to say, I have all ready been down that road with 225,and 5421 digital servo from Hitec .And had many trim issue.Randy, Gary JR have helped me in so many ways and taken many hrs of there time to help me.I have many Vortex planes,and i only use the Jr 3421 in all my planes .TOO me The Best servo for your $$$$ .
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Old 07-17-2009, 11:24 AM
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daven
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Default RE: cheap servos

I am strictly talking the slower stuff here, AMA 424 max.

I understand the importance of good servos on the faster stuff, just looking for alternatives for the newer guys to get started without breaking the bank.
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Old 07-17-2009, 01:00 PM
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Default RE: cheap servos

What is the futaba servo of choice for you Futaba Teamers
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Old 07-17-2009, 01:21 PM
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Default RE: cheap servos

For the fast stuff (428, 422) I really like the 9650's..
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Old 07-17-2009, 01:26 PM
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Default RE: cheap servos

They are using 9650s or 3002'sfor ailerons and elevators and 3102's for throttles and 422 rudder.

For the most part, may be some variation, but those are the popular futaba current servos. At least from what I saw at the tech inspections at the Nats.
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Old 07-17-2009, 07:11 PM
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Default RE: cheap servos

One thing I found out over the many years flying is that more expensive is not necessarily better.


I bought and used about 12 of the JR sport MN-48 servos:

One of twelve servos purchased was bad upon first use.

The main issue I've seen is that it is easy to strip out a gear due to a stalled servo. I did that when adjusting an engine kill.

They seem to be as reliable as others in that size category.

I've used Futaba 9650 servos and like the speed. An elevator servo jittered after just a few flights on a Q-40 model.

Over the years I've also flown JR servos. They seem to have the best for reliability. I've had them quit also. When mine quit it was without warning.

I will probably continue to use the MN-48 on 424 and lower cost projects. I'm a little reluctant to use them on my higher powered models.

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Old 07-17-2009, 07:54 PM
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Default RE: cheap servos

I just bought some Hitec HS-5245 dig. servos today. It's just a digital version of the 225.
Anybody have any history with this one? It has metal gears and about 10% more torque
than the std 225. I have 26 flights on a 428 with 225's with just Karbonite gears and they
have done fine.
Anybody use these?

john g.
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Old 07-17-2009, 09:17 PM
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Default RE: cheap servos

Remember the Futaba S35's? The coreless motors would up and die without warning.. I still have some of those laying around, too.

Sooner or later, they'll all give out. Some just sooner than others. Glad to hear you saved the plane, Dave - that's what counts.

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Old 07-18-2009, 07:08 AM
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daven
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Default RE: cheap servos

John, many of us have tried those hitecs, for the most part they have worked pretty good, but we've seen some failures. I'd say more than we have seen with the JR 3121 / 3421 or Futaba 9650s.

I've heard that you can replace the metal gear on that servo with the nylon servo from the 225 to tighten up the slop and to reduce weight.
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Old 07-31-2009, 11:30 AM
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Default RE: cheap servos

I use 5245s and I'm generally happy with them even though the gears wear out a little sooner than I think they should. I like that the servos are programmable and I can reduce throws to suit in the servo rather than the transmitter. That way I don't loose resolution. Be careful with them. If allowed to stall near the end of travel they will be done in a couple of seconds. They don't let smoke out but a component on the board fails.

Denis
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