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Hitec servos [225 bb]

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Old 12-20-2004, 02:22 PM
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MormonMike
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Default Hitec servos [225 bb]

Well, now were losing confidence. Word has that a number of the HS 225BB sevos are failing in flight. Any one have any info on this subject cause I'm not installing them till I here something about these from you guys with a little more expierience. Please respond, MM.[]
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Old 12-20-2004, 05:35 PM
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JohnBuckner
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Default RE: Hitec servos [225 bb]

At last count I think I have around 48 of them and are my preferred servo for my pylon racing aircraft (speeds to around 160) that I try to keep seven to nine airplanes all the time. Avoid the metal gear version, these get noisy and in my estimation are not as reliable. Also used them in some other applications. Yes they have a bad rep but not for me, although I did manage to get three bad ones about a year ago out of the box. Of course they were replaced no problem. I do Run my new servos of all types on a servo-cisor at least a half hour out of the box.

In my opinion the bad wrap has been from use in applications where they are really not suited and that is any kind of airplane forty and over with giant control surfaces that are set up for huge deflections.

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Old 12-21-2004, 08:36 AM
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Default RE: Hitec servos [225 bb]

Thanks John, The results you have don't sound too re-assuring. I'll leave 'em on the shelf for throttle servos only, Thanks again. MM
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Old 12-21-2004, 10:54 AM
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Default RE: Hitec servos [225 bb]

HMMMM, perhaps my communication skills are beginning to deteriorate. All I can suggest is what I once told a gentleman at a local flying field who was quite upset that I had the temerity to show up on a daily basis for years virtually trouble free at a field where it was politically incorrect not to us Futaba Products. What I told him in the sincerest possible terms was: Steal my money, Runoff with my wife but stay the H__L away from my 555's and 225's!

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Old 12-21-2004, 02:06 PM
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Default RE: Hitec servos [225 bb]

I have 225's (nylon gears) in 2 Quickie's and they worked flawlessly all last season. I've heard that they don't hold up well in applications that require constant large movements of the servo such as 3D. I did just take apart some HS-56's that I am going to use in 1/2A pylon racers and found alot of solder balls, flux, and bad solder joints on the motor.[X(] Scary situation. I'll be looking inside all new Hitec's in the future.
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Old 12-21-2004, 04:22 PM
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Default RE: Hitec servos [225 bb]

Some people have luck with the 225s and some don't.

Those having luck seem to be the ones who use them in planes with small control surfaces with small throws -- applications that really won't tax a (supposedly) 65-oz-in servo.

The people having problems are those who actually believe Hitec's claims that these are a 65-oz-in servo and use them in the same type of application where you'd think such a servo should work fine.

For example, I have a plane in which I stripped THREE of these 65-oz-in HS225MG servos, each lasting no more than half a dozen flights (no crashes, no abuse, only smooth landings). I replaced these 225s with a plain old "standard" HS425BB that supposedly have 10-oz-in *less* torque and have since put in nearly 50 flights without a single problem.

I did some tests to see what the stall-torue of the HS225 servos actually was and found that the MP gear (the one that engages with the gear on the motor shaft) strips at less than 85% of the rated torque.

So, the HS225 has a *very* weak geartrain that is incapable of reliably providing the rated torque figures.

When used in an application that requires torque levels of just 35-40oz-in then they should work fine -- but if that's all the torque you need, why not go for the smaller and lighter HS81 or HS85 anyway??

The HS225 is pitched as a "mighty mini" when in fact it should be pitched as a "fragile standard".

Hitec are aware of the problem (although they are unwilling to publicly admit that the geartrains are just not up to scratch) and I wish they'd simply add a sidebar to their product information that states "these servos are not suitable for high-load applications". Right now, anyone reading the spec sheet would (quite reasonably) expect that the HS225 is a stronger servo than the HS425BB -- which it most certainly is not. That's why so many people are having problems.
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