Maiden preflight tuning, result 1 then 2 failed hs 635 servos
 

I have been building a cmp 140 mustang for a number of years now and finally finished it this weekend. It has a magnum 180 fs which gave me a bit of trouble initially but is running great now. During this time the motor was running very roughly and I noticed one of my ailerons was not moving smoothly and upon inspection it had stripped the gears around the neutral position.
I continued with my tunning and then noticed the same from the other aileron, so now both aileron servos have failed in the same way. and yes they where fine before, what would be a good servo to replace these HS 635hb as I don't trust them now?
thanks Greg

I didn't realize that the 635' had HB, or Carbonite servos. I know the 485's are carbonite, and those gears are brittle and break easily. I have had multiple carbonite servos fail in high vibration environments. I wouldn't use them in anything but an electric.

I don't think those servos are recommended for models over 12#. The material used for the gears is unsuitable for larger models, and their associated higher vibration.

I use Hitec servos, but stay far away from the Karbonite gears.

Heck I used to read that way back in the day they only used plastic gear servos in large gassers.

But don't do it!

I almost lost my Topflite Gaint P40 last weekend. Im not sure what I was thinking at the time of building this one but I had Futaba S3010 plastic gear servos on the Ali

While I installed a new Iceman 3axs Gyro on it and was on my 7 flight of the day adjusting the gyro I almost lost my bird. Even with 2 6.6life 2500 and 2 switches the survo put my plan in black out for 2 sec.

After I got it down I found out the left one completely stripped and the other side was striped a few teeth and was about to let go

HS645 are great low dollar gaint war bird servos

mike,

Glad you saved your plane. How did you like the big P-40?

I only use 645MG's

I have the top flite gaint p51, p47, fw190, and p40

I was worried about the narrow location of the landing
Gear but it has been great. The Robart air retract have been amazing

It flew odd compare to the others but one day a friend of mine made me latterly balance it and I had to put a huge chunk of led in the outside servo bay in the wing that helps a lot

I actually won 1st in 2 NASA Scale events with it so it flys great with a DLE55

I just put that iceman gyro in and wow!

I was flying in a 20mph with gust close to the 30 with the gyro on it felt as there was no wind at all. With the gyro off I had to use rudder to get it around and it got blown around like a foamy.

Put full flaps and lands with the power stick very very easy almost lands its self

I've had one for 3 years and once I got used to landing fast, it has become my favorite. Been using Xoar 20x10x3 props but will try a Mejzlik 20x12x3 early next season. The plane looks damn good on a fly-by!

Also, Robart sells an airline restrictor that slows the gear to about a 7 second cycle speed. You might try one for a cool effect.

Mike,

I've got 3010's on my P-40 all around. I have the linkage set up for max leverage (huge control horn with the rod close to output shaft center). They seem plenty good to me, but what should I be looking for in terms of warning signs? You've got me worried....

Same as we do in our jets with it powered up try to move the controls by hand. The one that was just a little bad moved fine but when I put my hand on it I could tell.

Also like all servos. When powered off move them through there range of motion and listen for different sounds or grinding nose

Thanks for the input, and after posting I did a fair bit of reading and it confirms that hitec carbonite gear servos are not the suitable for my application. I will use hs 645 mg servos.
Regards Greg

You're welcome.

Well, I almost exclusively use Hitec and the majority of my servos use the carbonate gears. The largest airplane I use them on is a 8lb pattern plane. The only time I have ever had trouble is if I bumped a control surface and had that force transferred back into the servo. I fly the snot out of Hitec and they have been problem free. But yes, they are fragile when moved without the power on.

I remember back in the day flying 33% Extra 300's with a couple Futaba S148 servos on everything but the rudder.... How technology has changed :)

Yep.

I had a Hangar-9 25% Edge with a Moki 2.1 and Airtronics 94102's all around. When I first built the Y/AA Hornet, I was surprised to see what servos were shown in the isometric drawings. I think the stab servos were 90-ounce, plastic-gear analogs. The first one I saw flying had two O.S. 91's and Futaba S148's all around. Go figure....

I flew a 100" Bf 109 with 148s. LOL

I know my. Byron f16 had 50oz plastic on its elevons. Crazy

But I think the issue is there a big difference in vibrant between a big nitro motor and the new dle motors

The issue is Karbonite. Hitecs nylon geared servos are fine.

The problem is not with the servos' but the 4 cycle engine. If you research mounting techniques for installing this type of engine you will find they recommend soft mounting. This method is to negate the negative power stroke that induces extreme vibration level in the airframe. I found this out after numerous servo arm screws had backed out from the output shaft of the servos. Using locktite solved this problem but not the vibration. The gear train in your servos suffered from this problem.

I use Hitech 5645 metal gear servos. They work great and the price (38 to 40 bucks) is a good price point for quality.

Glenn

i wouldnt exactly call 5645's quality. I used to be a member of the 5645 servo crowd, then I flew an airplane with Real quality servos and noticed a difference.
5645's is on the top of my list for worst servos ever. Their centering abilities are absolutely atrocious.

Hi,

Those are the ones that would inexplicably reset themselves after being programmed days before. Just turn on the radio and 'oh look, one of your stabs is backwards again.' I think the worst servo ever is the digital version of the HS-225. Analog one is great, though.

Why for the sake of a few dollars would you not put metal geared servos in a Gas/Petrol plane when that is what is reccomended due to vibration.

Hitech 5645MG servos have worked fine for me. I dont program my servo's except with my radio (futaba 14SG). I am sure that invertmast is correct about higher end servos being better, all I am saying is that for 40 bucks it is a good servo. My experience has been fine with these on a gas prop powered plane.

I agree 100% they are the only hitec servos I have ever burned up

I really like sovox servos.