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12-28-2014 05:06 PM  5 years ago
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plankflyer

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Texas

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Grounding tailboom
The manual for the 3X/3SX calls for an electrical connection between the tail boom, motor and frame. I plan on installing a 3SX in a new Trex 500l which has a metal tail boom and wondered if the grounding requirement is as important with a shaft driven tail.

Any insight into this would be much appreciated and if the connection is necessary, how would I go about bonding all three components.

Thanks in advance.
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12-28-2014 05:09 PM  5 years ago
wrongler

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Brewerton, New York

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Wire tail to boom, boom to motor mount would do it.Bill Whittaker
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12-28-2014 06:19 PM  5 years ago
plankflyer

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Texas

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Thanks for the response but that creates several unanswered questions. Why connect the tail to the boom if they are both metal? What about the carbon fiber frames, they are also conductive and I would think need to be connected as well. Would this be accomplished through the motor mount and if so why not just attach to the frames and not worry about the motor mount? Also, what do you think the best method for attaching the connection to the tail boom would be?
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12-28-2014 06:49 PM  5 years ago
dkshema

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Cedar Rapids, IA

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Grounding a shaft driven tail is not something you need to do. A FEW belt-driven helis may need grounding, but it's not a common practice.

Hard anodizing aluminum makes its surface an insulator, it is non-conductive. You would have to penetrate the anodized layer to get to the bare aluminum, to reach a conductive bit of boom. This would explain why in an installation where bonding the tail case/boom/frame generally requires that you drill a hole and insert a screw/bolt to fix the wire to the object in question.

Many helicopters use plastic fittings (or anodized aluminum parts) at the rear of the heli frames that accept the round tail boom and adapt it to the parallel side frames. Since the plastic or anodized parts are non conductive, you would necessarily need to make electrical contact between either an anodized aluminum boom, or a carbon fiber boom and the frames. That explains the need to connect the tail boom to the frame, were you needing to ground the tail boom.

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The idea behind the grounding bit is to eliminate the potential for a static electricity discharge, which can wreak havoc with processor-based receivers, gyros, and/or flybarless system controllers. A static discharge can cause any or all of those to momentarily reset, a bad thing to happen while in flight.

Belt driven helicopters whose tail rotor cases are electrically isolated from the rest of the mechanics can build up a large electrostatic potential (look up Van De Graaf generator to see how) during flight (especially on cold, dry days). At some point, the electrostatic potential becomes large enough to ionize the air surrounding the high voltage potential point, creating a large spark. The spark generates some fierce, broadband Radio Frequency noise and very high (but brief) electrical fields.

Charge builds up as the non-conductive belt goes around the tail belt pulleys. By electrically bonding a metal point on the tail case all the way back through the boom, and frame to either the motor mount of your battery's negative terminal, you eliminate the ability to build up any electrical charge, since the entire airframe remains at the same voltage potential (as all parts are now tied together by the wire you add).

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A shaft-driven tail eliminates the mechanism required to create the electrostatic charge back at the tail case, thereby eliminating the potential for random spark generation.
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Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz
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12-28-2014 07:12 PM  5 years ago
plankflyer

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Texas

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Makes much more sense, many thanks!
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