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Home✈️Aircraft🚁HelicopterThunder TigerOther › Tail case breaking
09-05-2006 11:19 PM  14 years ago
Yug

rrMaster

UK. Herts

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Tailblade balancing is as important as main blade balancing. Go on 'ave a go, there's nowt like a smooth running heli.Vegetable rights and Peace
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09-06-2006 01:35 AM  14 years ago
2LTime

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Walworth,NY

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Check the bearings in the tail grips. My case failed that way and right after I realized a couple of he bearings were pretty notchy.

Jeff
If you can't learn to do it well, learn to enjoy doing it badly.
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09-06-2006 01:48 AM  14 years ago
Yug

rrMaster

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2LTime - same here, but then after using different tail blades, the problem was resolved. An interesting issue that I tried hard to resolve was that when switching to idle up (2k), the boom would immediately be pulled into the frames. I spent ages replacing and checking everything, even play in the sleeves on the pitch slider. I got heavily into dynamic balancing, by fitting the whole hub/blade assembly onto a dremmel so I could spin it up to 9k and literally feel the vibes. For this of course, the the blades would be able to find centre pitch, but you can really feel the vibes if there is any static inbalance. Then putting the blades on the heli, WALLOP, switch to idle up and all hell breaks loose. All bearings and shaft are perfect. I then change the tail blades and no problems at all.
When I had the problems, I was using NHP95s cut down to 92mm. I thing the square edge of the cut blades may have introduced some tip vorticees which didn't show up in the dremmel test, but ofcourse the normal blade pitch on the heli is about 8 degrees, so the behaviour may well have been different, resulting in assymetrical thrust between the 2 blades. This results in a rotational vibration about the axis of the beem and hence explains why my boom got dragged into the frames due to the force of the belt tension.
Vegetable rights and Peace
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09-06-2006 03:14 AM  14 years ago
RCtaz

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Leander, TX

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When I had my rappy 50 I went through 3 tail cases bam, bam, bam!!

Come to find out my tail shaft was .002 out, replaced it and no more busted tail cases.

Would be willing to bet thats your problem and just because the output shaft is new dont mean its not bent!!! I had 2 in a row .002 out right out of the package!!!
~Texas Renegade Rotorz~
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09-06-2006 03:11 PM  14 years ago
Slowpoke

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Dublin, OH

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Picked up some new ones last night, I'll chuck them up in the lathe and put the dial on them before before I use them. Thanks.
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09-09-2006 01:33 AM  14 years ago
Slowpoke

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Dublin, OH

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Got a new tail case. checked blades for balance and they are very, very close. New tail shaft, checked runout, about .001". Bearings feel ok.

1st tank, just hovered to make sure the engine was running well and the tail was holding.

2nd tank, hovered for 1/3 of the tank, and then just did gentle circuits for the rest. Landed nice and soft.

THE FREEKIN' TAIL CASE WAS BROKE AGAIN! In the exact same place as the 3 previous ones. After only 2 tanks.

Boom is new, standard Mavrikk boom. New belt. New main gear and autorotaion gear.

I'm at a loss. What else can I look for?
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09-09-2006 01:44 AM  14 years ago
Yug

rrMaster

UK. Herts

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Slowpoke - 0.001" runout could be better, but you may have an inbalance between the aerodynamic performance of the 2 blades inspite of achieving near perfect static balance. Are you having any problems with the tailcase rotating on the boom ?Vegetable rights and Peace
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09-09-2006 02:41 AM  14 years ago
Slowpoke

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Dublin, OH

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Yug - no, the tailcase snaps into the holes in the end of the boom quite well, everything seems solid. It did seem like the tail kicked a little once while I was hovering. I'm wondering if somehow the belt snagged something and put a load on the case. I'm going to tear it apart again and see if can see any wear marks on the insides.
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09-09-2006 04:20 AM  14 years ago
fliggyg

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Albertville, Al

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Slowpoke you have my sympathy.... Nothing worse than having a problem and not knowing what is causing it.. GOOD LUCK MAN!!!

AS for the QUK tail.. I spoke with Nathan at ricks and he told me he would have the tail case in about 2 weeks.. however, there is a website I found that mail orders them from the UK I believe.. Dont know which would be quicker to get... I can post the website if anyone is interested


If at first you don't succeed... Spend MORE money and TRY again!!!
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09-09-2006 06:10 AM  14 years ago
2LTime

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Walworth,NY

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Bent tail hub?

Jeff
If you can't learn to do it well, learn to enjoy doing it badly.
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09-09-2006 01:17 PM  14 years ago
HUTCH964

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Taylor,Texas 76574 local airport T74

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You will be spending more on plastic tail case's than a Quick UK metal upgrade tail case at this rate!

Check all links and tail control rod make sure you have the washer that goes between the tail case and tail control bell crank & the case.. If all is free moving I think your better off getting the QUK tail case too prevent anymore problems ..


Sorry you had so many problems with the tail case!


Good Luck!

*****
Tim
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09-16-2006 06:45 PM  14 years ago
Slowpoke

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Dublin, OH

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Finally got some new tail cases in, and I saw something that might be a clue to what's going on. I wanted make absolutely sure the belt was twisted correctly, so i put just the left side casing on with the pully and shaft in it so I could look into the boom and see if the belt was catching on anything. I slowly turn the head, watching the belt and pulley turn, when I felt a 'catch' in the head. Continuing to turn the rotor, I saw the belt go slack on the right and tight on the left, and the belt pulled the tail casing into the boom. I think the teeth of the belt were catching each other. I know the belt wasn't at the proper tension because I just had the parts lightly attached to the boom, but I'm wondering if the belt is catching on itself and breaking the casing when it's all together and flying. When fully assembled, I have to run the tail belt fairly taught to not experience these random sticking situations when turning the rotor by hand. The guide pulleys are straight and in the proper place, belt is new. Several people have advised me to back off the belt tension, and I certainly can see the wisdom behind that, but on mine, I can't. I've got the belt fairly snug and I'm going out to test it.
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09-30-2006 08:08 PM  14 years ago
Slowpoke

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Dublin, OH

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Well, I think I've found the basic problem, but can't seem to figure out exactly what's causing it. I made a brace for the tailcase to keep it from breaking long enough to try to do some troubleshooting.

I took it out today, new tailcase, new tailshaft, new guide pulleys, made sure the belt was only twisted a quarter turn in the proper direction. The belt was taught, not overly tight. Belt is centered in the guide pulleys.

I hovered it for about a minute or so, and landed. With the motor running just fast enough to keep the blades turning, I could clearly hear a clattering noise like the belt was catching on something, and could hear what I think is the belt slapping the inside of the boom. I didn't hear these noises when I first started it up, it's only when the belt gets loose.

Turned it off, and sure enough, the belt was very loose. It seems something is causing the belt to grap or snag, and I think it's pulling the boom into the frames, and that's what was breaking the case before I had the brace on it. It's pulling the tailcase enough to crack it. I've torn the heli apart several times but can't find anything unusual. I've got two other 50s, and have never had the problem on them.

Could it possibly be the oneway bearing?? Both the grey and white gear are new, and seem to be running true. Turning the rotor by hand everything seems to be smooth if the belt is tight.

I'm at a loss guys. What else can I possibly check??
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09-30-2006 08:51 PM  14 years ago
Yug

rrMaster

UK. Herts

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That's exactly what I had except it only happened when switching to idle up (2k HS); a loud zzzzing sound so I'd land to find the belt loose, ie, it had been pulled into the frames. All my bearings and shafts were good. Eventually traced it to my tail blades. At the time, these were NHP95s cut down to 92 and balanced to perfection. I changed them to SABs and have never had a problem since. I've had problems like this with NHPs on other helis as well. Perhaps their profile is not as symmetrical as it should be, resulting in axial vibration.Vegetable rights and Peace
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09-30-2006 08:51 PM  14 years ago
Peefor

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Norfolk UK

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Looking at your initial pic, I wouldn't mind betting that big carbon push rod has a lot to do with the problem, especially if it's not supported anywhere.

Pete
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09-30-2006 08:55 PM  14 years ago
Yug

rrMaster

UK. Herts

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are you thinking that if the carbon pushrod is vibrating, it is causing oscillation in the TB pitch ?Vegetable rights and Peace
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09-30-2006 09:06 PM  14 years ago
Slowpoke

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Dublin, OH

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Ok, I'll switch back to the stock tail blades and give that a try. The tail pushrod is supported near the middle, but it still is a lot of mass, I know. I'll try the stock blades first. Thanks.
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09-30-2006 11:03 PM  14 years ago
Peefor

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Norfolk UK

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are you thinking that if the carbon pushrod is vibrating, it is causing oscillation in the TB pitch ?
The thin standard wire on my R50 vibrates on occasions with the three proper supports. Looking at the location where the case was broken, it just seemed that a heavy pushrod vibrating would cause such a fault line.

Also bear in mind the numbers of cases being broken, so it has to be something very drastic.

Pete
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09-30-2006 11:40 PM  14 years ago
Slowpoke

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Dublin, OH

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Pete, Drastic is right! One case only lasted for about a tank and a half of just hovering!

I'll keep an eye on the pushrod to see if it's vibrating excessively.
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