I plan to buy a second GP Wagstaff 1/4 scale Extra. My first one stripped one-half of it's dual elevator servos during a spin, and I could not recover (sad day). I was using Hitec the new HS-475HB's, each rated at 71oz (@ 6V). I use a 6V system. Is there a "formula" or "rule-of-thumb" to determine the proper servos to use for a given airframe, performance, and weight combination? It would have saved this airplane.
I can just hear someone say "buy the most expensive one's you can afford". The HS475's WERE the most expensive I could afford! I'm sure most people would rather pay $25 for a 71oz. servo (if it will be sufficient for the job) than pay $80 for a 100oz. servo simply for overkill. How do you know if it will be sufficient for the job before it's too late? I was told by "experts" that these would suffice for this airplane. They were $25 each, and a deal I thought. What is everyone else using on this airplane?
TIA, David
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S
Six_O'Clock_High
WHAT killed it? Are you SURE you did not bump the tail on something and knock a tooth out of a gear that then failed in flight?
A
A.T.
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HS475BB should have been enough for general sports flying. You did not mention whether your motor was within specs or top/overtop of range. Flutter, which occurs when flying some of those model types with large control surfaces to fast, or a hard landing which will cause the large control surfaces to bounce hard back on the gear train which will cause failure in gear trains. How did you determine the gear stripped in flight, not in crash? If gear stripped in flight, air pressure could have cantered that elevator half and perhaps you could have flown home on the other elevator half? The HS645MG would give peace of mind in that sort of model. - well advertised on the Hitec servo websites including spec sheet for HS475BB =
Karbonite Gear Announcement
Due to some reported servo output shaft failures, Hitec has changed the horn screw on all Karbonite geared servos from 8mm to 10mm in length. This increased the strength of the output shaft eliminating potential for a problem. If you have any Karbonite servos with the 8mm screws contact our service department at snipped-for-privacy@hitecrcd.com and we will be happy to send you the new 10mm screws at no charge. Please be aware that there were only a hand full of failures out of thousands of servos sold, but Hitec felt the need to address the issue with this change.
Furthermore, it has been determined that using any chemical thread locking agent like Loctite on the Karbonite gears to help secure the screw can weaken the material potentially causing it to fail. Note that there is no need to use Loctite or any other agent on the screw. The Karbonite gear material will not allow the screws to back out, even under high vibration.
Hitec RCD USA, Inc. apologizes for this inconvenience but felt it was the best course of action to prevent any future problems with the Karbonite geared servos. Karbonite is an advanced gear material technology that allows the servo to handle 4 times greater load without failing and zero wear, even after hundreds of thousands of cycles!
If you have any questions or concerns about these or any Hitec products please contact us at: snipped-for-privacy@hitecrcd.com
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