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BIG Hawk problem!!

Old 04-07-2007, 09:26 AM
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racer-RCU
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Default BIG Hawk problem!!

I have a century hawk pro with and O.S. 37 and I have had a problem with the feathering shaft failing on me. I have been in contact with century on several occasions and they are working with me on solving this problem. The first time it failed on me was when it was assembled from the factory, nothing in the head had been touched. Now if the nut had loosened up I could understand that this wouldnt be an issue but more of my fault because I failed to prepare the model correctly but the nylock nut sheared off the shaft, the threads were flatened. I claimed a bad part with them and they replaced all the damaged parts from the incident and explained to me how to properly assemble the shaft. When the parts were recieved I first greased the shaft and applied lock tight to the threads as instructed and tightened so that the blade grips had freedom of movement and tourqed down according the the thread size on the shaft in accordance with faa publication AC 43.13 1B. After 4 consecutive flights the shaft failed on me again in a hover. The feathering shaft failed in the EXACT same manor as it had in the first incident where I didnt even do anything to it, so that rules out something that i may have done. Upon inspection the threads were again just flatened because the nut just sheared right off of the shaft. ALL of my flights have been performed at 75% throttle....I havent even been to full throttle and this is happening to me. I have been talking to Antonio at helicopter world and we are both baffled at this sittuation and even Adam turner was used to test some shafts to see if they could get them to fail but no luck. has ANYONE else out there had any issues with something like this happening to them, if so please speak up because if this is a manufacturing issue they need to be made aware of it and it will take more than just my claim. If anybody has any insight into this issue please feel free to comment.
Old 04-07-2007, 09:27 PM
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syclic
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Default RE: BIG Hawk problem!!

Man, I have never heard of such a problem!

But I do have a question as I always just tighten the locknuts on any feathering shaft so that they snug up hand tight. I do not know ( and I do not think many of us long time heli flyers) what you mean by :

".....in accordance with faa publication AC 43.13 1B."

As we do not assemble our heli as per full scale FAR practices.

Here I can only think that maybe that is far too much torque and this results in a weakening at the base of the threads (stretching).
Old 04-08-2007, 08:49 AM
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Default RE: BIG Hawk problem!!

well all it is, is a tourque chart to use in accordance with the size of threads and everything....i mean it wasnt gorilla tourque but it still snugged it up. But the thing that troubles me is that it happened in the same maner when it was assembled from the factory....but that doesnt rule out that they overtightened it to. ill try this all again and just snug them up without a tourque spec and go from there.
Old 04-17-2007, 09:46 PM
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CatzAzz
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Default RE: BIG Hawk problem!!

Wow! first I have heard of this, But it seems to me that this would the first part that would fail if you were running a very high head speed.

Cheers, Mark M,
Old 04-19-2007, 09:18 AM
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Default RE: BIG Hawk problem!!

if you happen to be the person that posted this same artical on runryder, we all gave u advice that should have helped. If not disregard and just be sure you dont over tighten the locknuts on the end, dont use locktite on them. I would suggest if you dont have the larger feather shaft upgrade to it.
Old 04-20-2007, 04:40 PM
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Default RE: BIG Hawk problem!!

yeah i am the same i posted on several forums on the same day, i got it all put back together and did everything you guys told me to just waiting on a good day for flying.
Old 04-24-2007, 08:24 PM
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Default RE: BIG Hawk problem!!

I have a problem with my Hawk. It idles fine and then it hovers for just about fifteen seconds and then the engine bogs down. When it lands, it idles fine again. I have adjusted the needle valve and the control screw. Nothing seems to work. I am new to the RC world. I don't know much about the engines or carbuerators. If anyone can help, I would appreciate it.
[]
Old 04-24-2007, 10:48 PM
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Default RE: BIG Hawk problem!!

Hi

Lets first get a setup read out, Engine, servos, ect.

Do you have a pitch gauge? What are your pitch/throttle curves? What fuel? How old is the fuel?

Here is a good starting point

Normal flight mode
Point 1 -3 in pitch, 0% throttle
Point 2 -1 in pitch, 50% throttle
Point 3 0 in pitch 65% throttle
Point 4 5 in pitch, 805 throttle
Point 5 11 in pitch (I am running a os 37 so if you are running an os 32 stay at a 9 in pitch), 100% throttle

We will worry about idle up1 and 2 laiter

When tuning an engine, turning the needle screw clockwise leans the engine, counter clockwise richens.
A lean engine runs super hot because there is less fuel and as a result, less oil. A rich engines runs cool because there is a tun of oil cooling it. If you have to much of either one the engine will loose a lot of rpm's and run BADLY. You are going to want somewere inbetween, but on the rich side for longer engine life. I rich engine will have really poor pickup and during that transition it will worble, spit smoke alot of smoke out the exhaust along with raw fuel and oil. Unless you are really rich the engine should reach full throttle. A lean engine also transition poorley but unlike a rich engine, usually quites before it makes it to full throttle. Lean engines have no smoke comming out and don't hold consistent idles.

As you can see, running your engine to rich or to lean robs power. Your engine might not have enough power to get it into the air. Also, make sure you are not running to much pitch or it will bog
Old 04-28-2007, 06:43 PM
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Default RE: BIG Hawk problem!!

thanks cambo i changed the pitch and changed the ajustment on the carbuerator. Now it does fine so now i'm going to have to go trough the long process of learning to hovering and from there learning to fly. I'm really excited about my hawk pro.
Old 05-03-2007, 09:12 PM
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Don d
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Default RE: BIG Hawk problem!!

Crqshed my HAWK DOING AEROBATICS THE OTHER DAY. I CAN FLY THE HECK OUT OF IT RIGHT SIDE UP, BUT WHEN UPSIDE DOWN STUFF HAPPENS. PUT ACOUPLE OF DENTS IN THE TAIL BOOM AND BENT THE FEATHERING SHAFT. ORDERED NEW PARTS.. JUST FOR THE HECK OF IT, I CAREFULLY STRAIGHTENED THE FEATHERING SHAFT, NOT PERFECT BUT PRETTY CLOSE. PUT THE HAWK BACK TOGETHER AND CAN'T TELL THE DIFFERENCE IN THE WAY IT FLIES.. BLADE TRACKING IS STILL RIGHT ON!!!!!! AM I JUST LUCKY , STUPID OR BOTH????

ONE DIFFERENCE I FIND IN HELICOPTERS THAN FIXED WING IS THAT MY HELI DOESN'T GET BEAT UP LIKE MY PLANES. A FEW NEW PARTS AND IT IS AS GOOD AS NEW! PLANES GET LITTLE DINGS ALL THE TIME AND ARE ALOT HARDER TO FIX.


DON
Old 08-10-2007, 11:00 AM
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madmcphil
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Default RE: BIG Hawk problem!!

Yes, the same thing happened to me. Was on its 3rd flight. Didnt do anything wrong was just in a stable hove about 15ft high. Next thing I knew total loss of the rotor... the heli instantly crashed nose in. I was pleased it crashed nose in otherwise I might not have seen the real cause of the accident. I opened up the tail rotor (pretty much the only thing left) to find at ton of shredded cogs inside. Completely stripped.

Now I know I built the heli perfectly as its not my first. I have a few Hawk Pro's. Keep 2 permanently running and another for spares. It hasn't happened before on the other Hawks I have owned and currently own... but for sure I was shocked too see this!
Old 02-04-2008, 08:14 PM
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Default RE: BIG Hawk problem!!

I have a hawk pro with a o.s.32 eng, Futaba T6EXHP Radio Control System and a Gyro is Futaba AVCS GY 401, and a Futaba S148 standard servo. Well the problem is when it is in flight it does fine till it gets at my 3 o clock or 2 o clock at about 100 ft. away and 50 ft. up an i turn it to where im at its 8 o clock the tail shutters. I first thouht it was a rouge signal so i changed sights 3 times and it does the same every time. It never shutters nowhere else and the tail servo is the only one that does it an it only does it for a split secont enuff to move the tail 6 to 8 in, and thats enuff to scare the fire out u. If i keep my antana on the transmeter pointed at the hawk when its at that spot it willnot shutter i now this is a strange problem but i would apprecite any help.
Old 02-05-2008, 04:01 PM
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syclic
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Default RE: BIG Hawk problem!!

dlc408

May I suggest that in the future you start a new thread when you want an answer to a different question. The reason to do so is that many of us will then look at it right away.

For example, I had read this thread and knew that the question re the original problem, that originated the thread, had been dealt with so I almost did not look into this thread again.

The problem you are encountering is one you will find on all helis who have the gyro gain set a bit too high. As soon as the head speed increases a hair (as it does downwind in your turn (because it is unloading) the tail will do a quick wag until the load returns and the rotor speeds stabilize again. Try turning your gain down 5 or 10 percent.
Old 03-05-2008, 12:58 PM
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Default RE: BIG Hawk problem!!

What kind of grease did you put in the tail rotor gears, and when was the last time you re-lubed? They need something that will stick around to reduce the friction (and associated heat / wear). I use a medium grade axle grease for boat trailers (waterproof with great surface adhesion). I check every few months to see if more is needed, but rarely have to add any.

Good Luck!
Old 03-05-2008, 01:40 PM
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syclic
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Default RE: BIG Hawk problem!!

As the gears are delrin (self lubricating so to speak), I do not use any grease on them.

If you do feel that you want to use a grease, be sure that you do not use any type that is petroleum based. Any petroleum based grease is not good for plastics (gears and gear case in this example). It makes the plastic brittle. This is not good for the gears and in time, it will cause the bearing seats in the gear case to crack and also the gear case itself to do so.

You must always use synthetic gears in any application where it will come into contact with plastics or rubber. You can get synthetic greases for these applications at most hobby shops that sell R/C cars.

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