question about the new HS-475HB servos (Full Version)

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Bill Rademacher -> question about the new HS-475HB servos (11/13/2003 3:25:38 AM)

Hi,

I received four of the HS-475HB servos from Servo City, for installation in a heli, as an upgrade from standard servos.

I took it out in my yard for a hover, to make sure everything was right. I lifted off, and had no (aileron) left/right control. I landed it, almost like a dart, sticking the skids in the downhill side of a gentle slope of the drainage ditch next to my house. It was still running, and it all looked fine (Later I discovered I bent the mainshaft). It didn't hit hard at all, but I bent the mainshaft. I though it would be more robust.

aaaaanyway, The aileron servo horn, which has a pushrod/ball link on each side, had broken off completely, with the drive spline from the servo ouput gear still inside. I figured, well, maybe something I did. Who knows.

I decided to swap out the servo with another on the throttle, and as I was pulling the servo arm off, same thing happens.

I have ordered two gear sets, but I wanted you to know about it. The plastic seems very brittle. Much more so than a regular servo output spline, which almost seems unbreakable. Maybe a flaw in the plastic composition?

The other two seem to be fine. I'm scared to touch them! :)

Hitec service is superb. If I was sure it was the plastic, I'd send them in.

thanks

Bill Rademacher



MikeMayberry -> RE: question about the new HS-475HB servos (11/14/2003 8:56:40 PM)

Please send them back so we can look at them. We have recently switched to a longer 10mm screw that makes the output shaft much more durable. Contact service@hitecrcd.com and we'll figure out the fastest way to fix you up.

Mike.



Bill Rademacher -> RE: question about the new HS-475HB servos (11/15/2003 3:40:23 AM)

Ok, I'll try to swap them out and send them in.

thanks!

Bill Rademacher



Bill Rademacher -> RE: question about the new HS-475HB servos (11/19/2003 3:54:02 PM)

Well, I am definitely sending them in. The third servo output gear just broke off, on the ground. It was handling the pitch control on the heli.

Standard servos will easily handle these loads. I was upgrading for better centering. The average servos get sloppy after a time.

There has to be a flaw in the composition of the plastic.

I'll send them in this week.

thanks



PowerPlay -> RE: question about the new HS-475HB servos (11/20/2003 4:15:26 PM)

Bill

Are you using Loctite on the servo screws? Loctite will make them brittle, I know this from personal experience.



Bill Rademacher -> RE: question about the new HS-475HB servos (11/20/2003 11:24:23 PM)

Yes, as a matter of fact, I used a little blue on the screws. It would make them that brittle?

wow



PowerPlay -> RE: question about the new HS-475HB servos (11/21/2003 3:19:25 AM)

Yes. It makes the output shaft brittle, not the screws, just to be clear. Never use Loc-tite on plastic for this reason. I don't think these servos need any type of thread lock. Metal geared servos do need thread lock to prevent the screws from loosening.



Bill Rademacher -> RE: question about the new HS-475HB servos (11/21/2003 3:48:47 AM)

I used it because I have had a couple servo screws on the heli vibrate loose before, long ago.

Why have the other servos not become brittle? I suppose the plastic is a different composition?

I'm not sure that is the swiftest design move, in that case.

I have never read anything that said to not use the locktite...might be something HITEC can add to the instructions perhaps.

Bill



MikeMayberry -> RE: question about the new HS-475HB servos (11/21/2003 6:54:48 PM)

The horn screw self taps into the output shaft so there is no need to use anything on them to keep them from backing out like you do with metal geared servos.

Karbonite is a very unique material and is four times stronger than standard nylon and will not wear. It is a great step forward in servo gear technology however, it does appear to be susceptible to loc-tite which we were not aware of until now. This actually may be related to the other failures; we'll have to look into that!

We will post this info to inform others so hopefully, they wont have the same problem.

Send the servos in and we'll replace the gears for you.

Mike.



Bill Rademacher -> RE: question about the new HS-475HB servos (11/21/2003 7:29:12 PM)

OK, I'll send them in.

I would bet there are a lot of folks using locktite on servo arms for helis. The reason is that, although the arm is tapped the first time, a person setting up a heli may make several adjustments to the arm, and the screw/output gear might become a looser fit, susceptible to vibration. At least I did. I never need to move servo arms in an airplane, but I have moved my servo arms a few times on the heli.

thanks for your attention to this problem. How many places can you get a response like this!

Bill Rademacher



MikeMayberry -> RE: question about the new HS-475HB servos (11/26/2003 4:50:57 PM)

The screws will not back out of the Karbonite geared servos even if they have been removed and replaced hundreds of times.

Mike.



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