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Hitec Karbonite

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Old 08-20-2004, 11:23 PM
  #1  
3db
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Default Hitec Karbonite

I have used high end JR and Hitec servos in all of my cars and planes and I am wondering about the performance of the new Hitec Karbonite gear servos. Some questions about the high end digital Hitec Karbonite servos such as the 6925 to the 6945...

How is the gear tolerance in comparison to the metal geared servos? The same or tighter?

How is the strength of these gears? Are they breaking, stripping, or do they hold up?

Any info on these servos would be great. I would like to hear what people are experiencing with these servos.

Thanks
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Old 08-21-2004, 12:08 AM
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Default RE: Hitec Karbonite

The karbonite gears are stronger than nylon, although some people feel they are also more brittle which means that this incerased strength isn't always realised as improved resistance to stripping due to vibration or shock.

They certainly appear to wear much more slowly than metal gears whcih means that you don't get the same degree of slop appearing in the servo output over time.

I still prefer to go for metal gears in high-stress applications where you really don't want them to strip under any circumstances, but karbonite are a great improvement for over nylon for most other applications.
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Old 08-22-2004, 05:33 PM
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Default RE: Hitec Karbonite

I think the jury is still out on the Karbonite. I had one strip on an elevator on hard landing. Should not have stripped. There was no damage to the plane. I will be watching mine very closely.
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Old 08-23-2004, 10:03 AM
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Default RE: Hitec Karbonite

I think the jury is still out on the Karbonite.
Actually, I think the jury has finished their deliberation, at least for the Hitec standard servos with Karbonite gears.

My personal experience:

Great Plains Christen Eagle II -w- Fuji BT-50SA gas-ignition engine.

(6) Hitec HS-5475s, (4) airlons, (2) elevators.

After the 3rd flight all 4 airlon servos had stripped gears, 3 of them one tooth at neutral spot. Granted the 4th was probably caused by the control surface breaking 2 of 3 hinges. I don't know what caused the hinges to break (CA) though they probably did because not enough gap. They might have broke due to the stripping of the servo gears causing the the control surface from react to the digital high frequency updates.

I replaced all the stripped gears ($38.00), replaced all of the CA hinges with Robart hingepoints, and sealed the bottom of the hinge line with monocote.

3 flights after repairing the airlons I again stripped one of the bottom wing servo gearing.

Solution: I removed all of the airlon HS-5475s and replaced them with metal-geared HS-5645s.

BTW, Great Plains recommends servos with at least 50oz of torque for the airlons and elevator. The HS-5475s are rated at 76oz of torgue???

When I reported this to Hitec their initial reaction was my airplane had a flutter problem. When I informed them of the actions I took to eliminate and/or greatly reduce the flutter potential they effectively just put the blaim on Great Plains for improperly rating the airplane for 50oz servos. They neither acknowledged that there is a problem with the Karbonite gears nor did they really deny their was one. BTW, on one post from a Hitec rep, he relay'd to me that they beefed up the gear mass in their upper-end servos.

My Guesss: The Karbonite gears might be stronger than nylon and wear better than metal but they are much more brittle than nylon and are probably adversely effected by vibration. In my case, the vibration from the Fuji BT-50SA gas-ignition motor, which is smoother than most gas engines.
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Old 08-23-2004, 11:45 AM
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Default RE: Hitec Karbonite

I have them for ailerons on a 60 size plane for a year now and they have worked very well and have virtually no play ! I have seen one failure at our field on a 50 cc gas powered plane.

My guess is as above post !!!... some how they are not handling the vibration of the big engines
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Old 08-24-2004, 04:56 PM
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Default RE: Hitec Karbonite

They have outstanding precision and absolutely NO slop. As for breaking them, I did not break any and I have 3 of them (5975) on my 1/4 scale cap 232 which weights 11 lbs and is powered with a YS 140 DZ that is far from being a very smooth runner as it is hard mounted. I have about 100 flights on 2 of these servos and they do not show ANY sign of wear so far. The third one was added last week.

2 of the 5975 are on the elevators and one on the rudder. I had last year 2 5925 on the elevators and removed them to save some weight in the tail of the plane in favor of the 5975s. This to say that I have about 100 flights on each set of servos and I can say that they all hold up pretty well but the metal gears have a tiny amount of slop (maybe the same amount of slop as a brand new servo).

The Hitec rep says that one should not put a single servo in a plane larger than 12 lbs. It seems a rather small plane but when you consider that big guys put 4 servos on the rudder of their 40 lbs airplane or 10 lbs per sorvo, the 12 lbs limit seems well within reason.
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Old 09-23-2004, 12:33 AM
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Default RE: Hitec Karbonite

I replaced 5625's with the new 6975's on my 33% Edge ailerons (two per wing). They are sweet! I never realized how much blowback I was getting with the 5625's. Not to mention that the gears got pretty sloppy after 70-80 flights.

I have about 20 (hard 3D) flights on them so far and not even a micron of gear play. I hope they don't snap on me. Think I'll stay with MG servos on the elevators for now

Also have the 5975's im my Hawk Sport heli. I've flown thru one case of fuel with no problems. It bit the dust HARD today (stupid pilot) and no stripped gears or snapped-off shafts.

So far I'm impressed

KD
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