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Am I stuck with these Karbonite Digitals?

Old 07-20-2005, 11:02 PM
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lewdfinger
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Default Am I stuck with these Karbonite Digitals?

I have been flying Hitec 6975 Karbonite servos (2 per aileron) on my 33% Edge for about a half-year now and have had good success. No slop after about 100 flights. Emboldened by this and Hitec's earlier marketing ("Hi torque servo for your most demanding applications") I bought 6 for the ailerons on my 40% Extra last Fall. Big mistake! I finally got around to installing them tonight.

With the 1.25 inch AirWild MLP arms and the fatter ailerons, their lack of rigidity under load is much more obvious. I tried decreasing the deadband to minimum, but I'm getting about 3/4" of play in the aileron . Either there's a lot of twist going on inside the housing or the holding power isn't what you'd expect for a hi-torque digital. There is no way I can use them safely on this plane.

Now that I look at these, and read what people are saying about the Karbonite servos, I feel kinda stupid, and I wonder what Hitec had in mind when marketing a Hi-Torque digital servo with a weak spine. It seems the angle has changed a little since I forked out the cash. It's not like they're less expensive, either.

Anyway, what are my options? Will Hitec send me some 5945's in exchange, if I pay the diff?

KD
Old 07-20-2005, 11:41 PM
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mglavin
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Default RE: Am I stuck with these Karbonite Digitals?

The marketing never suggested the Karbonites were replacements for metal-geared servos. They are powerful but like the nylon geared cousins they simply are not metal and are not suited for shock loads and high stress environments.

As far as holding power and such, these servos essentially are comprised of the same components as their metal-geared brethren.

Are you suggesting you can deflect the control surface ¾” when the servos are powered up? Can you see the servo arm deflect under the pressure this ¾”?

Once the servos have been installed there is little to nothing Hitec can offer you. If the servos are defective we’ll repair them free of charge. It’s more likely than not you have other issues with either the mechanical set-up, power distribution and or power supply IMO.

Please describe the models power system, wiring, switches and the like. Are you using wyes and extensions chained for the three servos? Heavy Duty 22 gauge wiring components?
Old 07-21-2005, 01:06 AM
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lewdfinger
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Default RE: Am I stuck with these Karbonite Digitals?

Wow - that was fast! Thanks for your reply.

Are you suggesting you can deflect the control surface ¾” when the servos are powered up? Can you see the servo arm deflect under the pressure this ¾”?
Perhaps I should have been more clear. This is with a single 6975 hooked up on the inboard control horn. Of course I'd expect more flex with only one servo hooked up, but when I put even a used 5945 in the same position the centered holding power is much better. It seems to start groaning under load with way less deflection. And yes, I see the servo arm moving. Same with three 6975's I tried.
It’s more likely than not you have other issues with either the mechanical set-up, power distribution and or power supply IMO
Nope. 6V regulated Li-Ions, Super Reliaswitches, Dual Receivers, and Simon Van Leeuwen's PnP custom harness (only the best!) with no extensions. Dubro HD control horns and 4-40 ball links, 1/8" steel push rods and Airwild MLP servo arms.
As far as holding power and such, these servos essentially are comprised of the same components as their metal-geared brethren
That's why I was so surprised when it deflected like it was made of rubber.
they simply are not metal and are not suited for shock loads and high stress environments
Then I shall reserve them for my "second-most demanding applications" (park-flyers, blimps etc.) and get some 8611's

KD
Old 07-21-2005, 09:33 AM
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Default RE: Am I stuck with these Karbonite Digitals?

It makes sense that the 6975 is not as powerful as the 5945, its produces 44oz-in less Torque. This and the simple fact that the long servo arm reduces the Force the servo can provide as well.

8611’s would be more suited for your needs there is little doubt, to make a comparison to the 6975 Karbonites at 144oz-in against the retooled, refitted and now re-motored 8611A @ 280oz-in is a little extreme if not down right unfair. Hitec 5955TG @ 330oz-in or the 5945’s @ 188oz-in would be an excellent and well applied choice and you wouldn’t need any ancillary servo matching devices and their associated electrical losses either. Plus you get the precision and associated programmable benefits and true linear travel arcs of the servo and the TX and more.
Old 07-21-2005, 01:35 PM
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lewdfinger
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Default RE: Am I stuck with these Karbonite Digitals?

You are right of course. Just ordered some more 5945's. I've had nothing but good luck with HiTec digitals.

I guess it's asking too much of the 6975's on this plane, but they work so well on my Edge. The thought of a good digital that didn't need a new gear set every 80 flights seemed like a great idea. They just can't swing the bigger servo arms I guess.

Oh well, expensive lesson learned.

KD
Old 07-21-2005, 01:57 PM
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mglavin
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Default RE: Am I stuck with these Karbonite Digitals?

For a few more bucks the 5955TG's are currently available and these have titanium gears and 330oz-in Torque, to date gear-train wear is not a problem and their very tight when new...

You're not getting 80 flights on the 5945's, right? I have hundreds of flights on many with reasonable gear slop to date.
Old 08-04-2005, 10:59 AM
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lewdfinger
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Default RE: Am I stuck with these Karbonite Digitals?

So I got my new 5945's - three of them have 1.04 stickers and no date stamp, and three have no stickers at all. Can I assume the non-stickered ones are new stock, and the stickered ones have to be sent to Hitec to be fixed? I am running 2 Futaba PCM receivers, so 2 pairs of these will be wyed.

Also, do any of the 5955's have this problem?

I'm still waiting for my servo programmer to get back, and now I get to send servos to Hitec. What a treat!

KD
Old 08-04-2005, 02:54 PM
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mglavin
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Default RE: Am I stuck with these Karbonite Digitals?

Your assumption maybe correct. I checked with Service and they suggested it could go either way on the v1.04 stickerd servos.

Can your dealer handle an exchange for you?
Old 08-04-2005, 04:25 PM
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Default RE: Am I stuck with these Karbonite Digitals?

I already worked out an exchange for 4 5955's. Cheaper, less programming, and don't necessarily have to wye them together.

KD

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