Evil Tail Problem

[Jasmine2501]

My tail is screaming - loud, and it shakes up and down. I thought I had it fixed with the Trex hub I put on there, but when it finally gets up to speed, it's not happy. It shakes so hard the tail fin is about an inch-long blur up and down, but only on the left side - opposite the tail.

All of the tail case parts are new, as is the belt and the drive gear up front. Tail boom is new, pitch slider and ball links are new - everything is freeking new! I don't understand what is causing the problem - everything is balanced too.

The only thing I can see is when I look through the little hole at the front pulley, the belt seems to get wider and skinnier as I rotate the head.

I took this helicopter in to the hobby shop and they couldn't figure out the problem either... does anyone have any ideas what I can do? If it's "get the metal parts" then yes, I'll be doing that as soon as they are available, but really, I would like to just get her flying again with the plastic parts. I don't understand how it can go this bad when everything is new...

Is there something obvious that I'm missing??!

[JEB123]

Dumb questions, but do you have new bearings in there too? Are you sure the blades are balanced? It shouldn't matter if they're plastic parts, it shouldn't be that bad. Could you have a bent shaft or drive in the front pulley? Did this start after a crash? Some pics may help.

[Slyster]

Balance. And it won't work to balance just the blades.. but you need to balance the entire tail. Here's how I did it. Put a dot on one tail (just to recongnize the blades) .. put a 1/4" pience of electrical tape on one blade. (take main rotors OFF for this).. spool it up. better or worse? Worse move that piece to the other blades.. totally experiment.. After around 10 minutes (are 20 or so scrunched up pieces of tape) I finallly got it from wild vibe to small vibe. Impossible to get it totally smooth.

[dditch66]

So your saying the horizontal tail fin is what is shaking? But only the left side of it? Unless it's weak itself, that means the axis of rotation is on the right side of the tail fin. Funky. Is that the only thing you see shaking or do you see the entire tail boom shaking and is it up and down, left/right or a twisting shake?

My tail vibration issues have always been related to main blades/head balancing and tracking. But you say yours is balanced. Recently, my tail was wagging cause one of my paddles came loose and was not a 0 degrees, it manifested itself though in poor blade tracking.

Do you have a way to strap the heli down to something and run it up w/ parts of the tail head removed?

[Slyster]

Yes.. when you balance the tail (like the way I mentioned) you must remove the WHOLE head assembly really to get it right. Check for slight main shaft wobble when you have it off too.

[Jasmine2501]

Yes, I can hold it down and run it up. Been doing that with the main head removed, so it's just the main shaft and the tail running - still have the problem. The bearings in the tail case are new, but the ones that hold the drive pulley in front are old. This did happen after a crash in which I re-built the whole helicopter. First flight after the rebuild was ok, but the problem has been getting worse since then, and now the heli is shaking so bad that it shouldn't be flown - although it will still fly.

If you look at this picture, you can see a small shake in the tail fin, which all Blade 400s apparently have. Now imagine that little blur being 10 times that size, and really loud sound from the tail... that's my issue. I know about all the basic things to do, but was really looking for some arcane thing particular to the Blade 400 - some bad part, poor alignment, missing washers, some known issue that isn't common. I've done everything I know how to do and the problem is still there, so was just wondering if someone had a nugget of info that I missed.

[JEB123]

Originally Posted by Jasmine2501

Yes, I can hold it down and run it up. Been doing that with the main head removed, so it's just the main shaft and the tail running - still have the problem. The bearings in the tail case are new, but the ones that hold the drive pulley in front are old. This did happen after a crash in which I re-built the whole helicopter. First flight after the rebuild was ok, but the problem has been getting worse since then, and now the heli is shaking so bad that it shouldn't be flown - although it will still fly.

If you look at this picture, you can see a small shake in the tail fin, which all Blade 400s apparently have. Now imagine that little blur being 10 times that size, and really loud sound from the tail... that's my issue. I know about all the basic things to do, but was really looking for some arcane thing particular to the Blade 400 - some bad part, poor alignment, missing washers, some known issue that isn't common. I've done everything I know how to do and the problem is still there, so was just wondering if someone had a nugget of info that I missed.

How's your belt tension? Could it be too tight, or too loose? If not, I would change out those front bearings. A bad bearing there could cause the belt to oscillate. It would also be noisy. Does it get progressively worse, or does it start to improve again after a certain speed?

[Jasmine2501]

I have tried various belt tensions from way too loose to super-tight, and doesn't seem to get rid of the problem, although super-tight did seem to reduce the problem a bit. I'll change out the bearings I guess - that's the last thing I haven't changed. Does anybody know what size those are?

This vibration gets much worse at a certain speed, just below flying speed is when it's the worst, and it gets a little better above that, but the vibration never goes away, and it's there at lower speeds too, you just don't really notice it till it builds up. It is a harmonic resonance building up, but I don't know what is the source of that. Going to try fixing the bearings and putting in a different belt - then I'll post some video if I can't figure it out.

[JEB123]

Originally Posted by Jasmine2501

This vibration gets much worse at a certain speed, just below flying speed is when it's the worst, and it gets a little better above that, but the vibration never goes away, and it's there at lower speeds too, you just don't really notice it till it builds up. It is a harmonic resonance building up, but I don't know what is the source of that. Going to try fixing the bearings and putting in a different belt - then I'll post some video if I can't figure it out.

Exactly, that's why I asked about it doing it at a specific speed. Could be that the belt is oscillating and the tail tube is resonating at a certain freq. making it worse. Or maybe I'm totally wrong and it's something else! Don't know what bearings that bird uses but I'd definitely at least check them. Good luck with it, let us know what you find! I get good prices on bearings here:

http://www.bocabearings.com/main1.aspx?p=docs&id=3

[Tail boom]

Originally Posted by Jasmine2501

I have tried various belt tensions from way too loose to super-tight, and doesn't seem to get rid of the problem, although super-tight did seem to reduce the problem a bit. I'll change out the bearings I guess - that's the last thing I haven't changed. Does anybody know what size those are?

This vibration gets much worse at a certain speed, just below flying speed is when it's the worst, and it gets a little better above that, but the vibration never goes away, and it's there at lower speeds too, you just don't really notice it till it builds up. It is a harmonic resonance building up, but I don't know what is the source of that. Going to try fixing the bearings and putting in a different belt - then I'll post some video if I can't figure it out.

Hi,

You might want to take a look at the end of the tail boom, the end that slides into the main frame. Sometimes that end can get bent inwards, causing it to actually touch the belt.

Also make sure that the holes of your tail blades are not worn out. They wear out over time and get an oval shape, causing them to be out of balance.

Do the tail blade grips have enough play to "flap" the tail blades?

Does your tail hub sit firmly on the tail shaft?

The tail slider ring can sometimes get caught at the slider pin screws, causing vibes. Just see whether you can spin the slider ring freely.

Is your tail shaft lubed with TriFlow?

Are _all_ of the ball bearings in the whole tail system ok and without slop?

Is the belt tensioner ok or too sloppy or too tight?

The tail case, did you tighten the two halfes too much? Usually, the very end of the tail case shows a little bit of a gap when mounted. If too tight, the tail case bearings might be too much under axial pressure and start to be notchy or lock up.

Long list ...

Best,
Frank
P.S.: Nice landscape in the background!

[sokal]

Originally Posted by Jasmine2501

My tail is screaming - loud, and it shakes up and down. I thought I had it fixed with the Trex hub I put on there, but when it finally gets up to speed, it's not happy. It shakes so hard the tail fin is about an inch-long blur up and down, but only on the left side - opposite the tail.

All of the tail case parts are new, as is the belt and the drive gear up front. Tail boom is new, pitch slider and ball links are new - everything is freeking new! I don't understand what is causing the problem - everything is balanced too.

The only thing I can see is when I look through the little hole at the front pulley, the belt seems to get wider and skinnier as I rotate the head.

I took this helicopter in to the hobby shop and they couldn't figure out the problem either... does anyone have any ideas what I can do? If it's "get the metal parts" then yes, I'll be doing that as soon as they are available, but really, I would like to just get her flying again with the plastic parts. I don't understand how it can go this bad when everything is new...

Is there something obvious that I'm missing??!

so your the other video maker just like to say thanks


so loud vibrating tail eh

try to check its with out the main blades on to see if you still feel the vib
this will determine weather is tail or hub may still be both

the lil belt pully gear in the frame also could be your culprate. check slider control belcrank as this thing will have a bent screw on occation and if your slider bearings are too tight will also cause probs

also the bushing in the tail is of its own size may be a lil long or short

i know this may sound dumb but the tail blades are leading edge controled

and make sure the rex hub bearings are not seizes

hope you find your issues

[Jasmine2501]

Originally Posted by sokal

so your the other video maker just like to say thanks


so loud vibrating tail eh

try to check its with out the main blades on to see if you still feel the vib
this will determine weather is tail or hub may still be both

the lil belt pully gear in the frame also could be your culprate. check slider control belcrank as this thing will have a bent screw on occation and if your slider bearings are too tight will also cause probs

also the bushing in the tail is of its own size may be a lil long or short

i know this may sound dumb but the tail blades are leading edge controled

and make sure the rex hub bearings are not seizes

hope you find your issues

Yeah that's me... I love the Blade 400 and I really just want to get it flying again. I'm tearing it apart now and we'll see what happens. Will be replacing every part that isn't new since the crash... All the bearings on the main shaft, the bearings on the tail drive gear, and got a new belt and boom too, just in case it's that. I looked at the one at the store and it has a little gap in the tail case parts, so I will try not putting it on so tight.