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HelicopterCentury Radikal G20-30 N640 Hawk Predator › Hawk head in a bind, of a different sort....
08-07-2009 04:49 AM  8 years agoPost 1
YKZ

rrNovice

yellowknife NWT

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hey guys, converted my 500 defender (raven/hawk platform) back to a 2 blade system from the 5 blade while i wait to order a new shorter set of blades for it. i just put a fresh head on it, new bearings, feathering shaft, dampers. I should mention the collective servo is 9252, so theres lots of power there for the 2 600mm blades. on the ground not running everything is free, lots of pitch, +11/-11, but once i am up to rpm i increase collective to the point which it starts to seem unreasonably high and it will not lift off. i can actually put full pitch in and it just lifts off. not right. i can visually see that the swash plate is not going full travel. i believe the grips are binding for some reason under load. disconnected the grips have already developed a notchyness. I had this same prob the last time i used the 2 blade head so i put in new bearings thinking that was the prob, but again, same prob, same notchyness....any thoughts? pretty hard to screw up assembling a hawk head but maybe i have missed something. 1 nut and 2 washer at outter, 2 bearings, spacer behind inner bearing, another washer then the brass bushing and big washer and damper.... any thoughts?

thanks
YKZ

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08-07-2009 08:02 AM  8 years agoPost 2
Furious Predator

rrProfessor

Kitchener, Ontario, Canada

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I'm not sure about the pitch problem. something doesn't sound right about that. If you have it set to go as far as +11 on the ground, then it should do it in the air. Like you said, those servos are more then up to the task as well.

Perhaps you should take a look through this thread and just re-check that everything is correct, especially if you suspect binding.


But i can say that the Notchyness you feel is normal. When you tighten the nuts on the spindle, your loading up the bearings. Once the blades spin up, they will cancel out that load and the notchy feeling will go away. You can see this for yourself by pulling out on the grips and rotating them at the same time.

Shawn
Team Leisure-Tech
Team HelixRC

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08-08-2009 03:13 AM  8 years agoPost 3
oldfart

rrProfessor

Vancouver, Canada

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I will bet that you have installed the two outer washers on the feathering system in the wrong sequence...the smaller one goes on the inside (to ride against the inner race only of the bearing) and the larger one goes on the outside of it.

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08-08-2009 06:34 AM  8 years agoPost 4
YKZ

rrNovice

yellowknife NWT

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thanks guys, but strangely enough i have borrowed another serviceable hawk head and it works fine. Quite weird and i cannot nail it down to the prob. Everything is assembled correct, all the washers in the right spots for loading the bearings correctly. the only visible difference between the two head assemblies is the blades, the one that works has the 550 CFs, the head that doesnt is running 600FRPs. Also on a seperate note, the was a fuel dripping from the engine area on this hawk, found all the head bolts less than finger tight. Not cool. Should run like a champ tomorrow.

YKZ

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08-08-2009 08:28 PM  8 years agoPost 5
Dilbeck

rrElite Veteran

Springdale Arkansas

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I experienced this same problem and as oldfart mentioned I had the washers reversed, It worked fine on the bench but once I spooled it up it locked up the bearings and would not lift off!!

Clint

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08-26-2009 03:49 AM  8 years agoPost 6
YKZ

rrNovice

yellowknife NWT

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just finished doing the 6mm feathering shaft upgrade. Upon closer inspection trying to figure out my problem i think i have it figured. I put new bearings in this head three times and it had the same problem after about 1 or two times hovering on each head, gradually it would increase in pitch less and less to the point of not even pulling enough pitch to hover. it was like it was chewing up the bearings. I believe that what it was, was that i was rebuilding the heads using bearings from RCscrewz.com, which have lasted very well in all places i have used them. Turns out that the seal cover for the cage of the bearings must be ever so slightly thicker than those of century as when the outter smaller washer that buts up against the inner race for proper loading actually touches the seal. You can can see where the washer has been running against the seal. One would assume that once the bearings are actually loaded(trying to pull apart axially) this touch of the seal would be even more pronounced and most likely dragging on the bearing cage and probably loading it up to the point of not allowing the grips to turn much. I think knowing this i could have probably used a washer against the inner race with a reduced OD, something that was only the OD of the race that could not interfere with the seal/cage. Thats my thoughts on this problem! Something to watch out for!!

YKZ

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HelicopterCentury Radikal G20-30 N640 Hawk Predator › Hawk head in a bind, of a different sort....
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