Saturday, May 10, 2008

Maintenance and common issues

With time, I've found some common failure points that need to be anticipated and addressed timely in the dragonus.

1) Anti rotation pin does not slide smoothly in the rail
2) Vibration: Dragonus vibrates at high rate.
3) One-way bearing shaft (R01CP071) wears out.
4) Pitch control arm (R01CP075) separates from the internal bearing.
5) Brand new 3K CARBON STABLIZER BLADE(Paddle) won't fit in flybar.
6) Unable to remove a bearing from an aluminum part

1) Anti rotation pin does not slide smoothly in the rail

It's a common mistake to overtight the screw that holds the plastic sleeve.
Don't. The black sleeve should have a gap, rotate freely over the screw.

Sometimes RCer packs a threadless screw, some times they don't. Use threadlock or CA as needed to hold the screw in place and make sure the black plastic sleeve rotates freely.


(c) Photo courtesy of Butuz from RCHeli Addicts

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2) Vibration: Dragonus vibrates at high rate.

Cause: something is out of balance

Symptoms:
  • Erratic Gyro behavior
  • Blurry-looking landing skids and/or tail when in hover (this may lead to a broken landing skid basemount (R02TP088) and/or damage somewhere else)
  • Tail wag
Fix:
  • Balance all tail and main blades / change them when troubleshooting.
  • Measure and balance flybar / paddles
  • Check main shaft (R01CP121). Hardened shaft is recommended as the original bends at high speeds.
  • Check bearings.
  • Check head speed as too much speed leads to vibration.
  • Play (slackness) between Main Rotor Housing and Main-shaft: Make sure that joint is very tight and the bolt is well loctited. Otherwise this will make the whole rotor shake. This issue is more common in the aluminum head than the plastic version, to the point some pilots prefer the plastic head just because of this:


Make sure this is tight and loctited

3) One-way bearing shaft (R01CP071) wear: This shaft wears away with not much time of use.

Symptoms:
  • Sudden and brief drop when in hover, repetitive, random.
  • Or sudden and brief jump when hovering, repetitive, random.
Cause: The bearing loses grip of the shaft. This is not easy to detect and the wearing is barely noticeable.


Here, the one at the left needs to be replaced.

Fix:
  • Change the shaft. One-way bearing (R01CP135 - RFC6 Bearing) may also be defective and needed to be changed.

4) Pitch control arm (R01CP075) separates from the internal bearing.


The bearing shown by the arrow, may pop out into the boom direction.

Symptoms:
  • Wear of pitch control arm plastic links.
  • Tail stuck -> lost control of the tail rotor.



Since the bearing may come out, the wear between is quite noticeable.


Another side effect of the same issue.

Fix:
  • Review before flight. Loctite (red) between the control arm and the bearing for aluminum part and CA for the plastic version to prevent the bearing from coming out.

5) Brand new 3K CARBON STABLIZER BLADE(Paddle) won't fit in flybar

Symptom:
  • Paddle will not fit / will break when screwing it in.
Fix:
  • Drill/dremel the hole in the padde until you get a good fit.
6) Unable to remove a bearing from an aluminum part

Cause: Bearings come loctited from factory.

Fix:
  • Heat the part using a torch until you see smoke coming out of the bearing. After that it will come out easily. Watch it with your fingers, as very high temperatures are obtained in this procedure. Also bear in mind you may melt the aluminum as well if too much heat is applied.

4 comments:

SLum said...

I have problem with my dragonus cnc swashplate. A ring came off during flight and i have to push back in every 2-3 flights.

How do I solve this issue..

anyway great dragonus blog..Like it..

http://www.flickr.com/photos/slumberjer/4432287698/

Mike said...

I have a problem with the motor bogging down when going from mid to reverse pitch, and then back up to mid. This is why I keep crashing when going inverted, the heli will hover inverted for a short time, before bogging down and loosing power, consequently hitting the ground like a brick, even though I am putting in full negative. It also makes a strange sound. I have double checked my pitch and throtttle curves.

Rod said...

You may have forgotten to tight the stopper at the main shaft. When powered off, see how much drag is felt when you push down the head at the same time you rotate it.

Unknown said...

Those really look sturdy and very stable for supporting an object. Good quality for sure.
white metal bearings

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