View Full Version : Evo 50 Tail rod vibrations
Gixxer
04-20-2006, 08:03 AM
i have the stock tail rod in the little holes on the supports. It is vibrating back and forth when it is running and you can hear the buzz it makes from the fast vibration. I have a wicked tail wag and I think its from the interference.
Anyone else's tailrod make noise in the stock supports? Any fixes?
playfair
04-20-2006, 09:14 AM
Yeah, mine used to buzz all the time. I ended up going to a solid carbon rod and don't use the supports any more (even though you can with the bigger guide holes).
You might try moving the supports forward or back a bit, it could be just a simple harmonic set up between the engine/tail rotor/etc. that buzzes the rods. On teh Vigor, the book says not to set the supports at equal spacing for that very reason.
BarracudaHockey
04-20-2006, 10:53 AM
Might be time to take a look at the following items.
Fan balance.
Tail output shaft running true
Dial indicate fan and clutch shaft.
Gixxer
04-20-2006, 10:59 AM
Yea I tried that... I think the carbon rod will have to be the way. I was hoping the stock way would work on this heli but carbon we go. I just hope that is the reason for my gyro interference. I hate chasing demons
Laurens
04-20-2006, 11:49 AM
Engine still running in?
Gixxer
04-20-2006, 11:58 AM
na the motor is out of my other helicopter that planted itself in Birmingham. Ill take some time and look thru all of the drive train and see if everything is still tight. Ill be looking for some help at the FAI event at Stator Gators this weekend fellas!
One other thing, since the start shaft is solid mounted to the engine, instead of fittinginto a oneway bearing, the start shaft has to be near perfectly aligned to keep the vibrations down. I clamped the edge of the motor mount in a vice and used a travel indicator to get the shaft to less than .001 runout at several places along the length of the starter shaft. This made the heli soooooooo much smoother.
Also to check the fan hub, just pull it, blades and all off the heli, grasp a blade grip in each hand and apply pressure like you would if trying to bend the hub. rotate the pressure around in circles, if the hub moves while doing this, it is bent.
Gixxer
04-21-2006, 07:18 AM
I went thru the heli last night and found that the starter nut had some loose and had slop too it. Im hoping that is the source of my gyro glitching. Ill see this afternoon up at the FAI show.
Ivan.... ill take a look at my fan assembly again. I went thru it last night on the heli and everything seems to look pretty good right now (It has only hovered a few times)
The tail rod rattle still bugs me though... thats got to go for sure.
Thanks everyone
playfair
04-21-2006, 08:07 AM
In addition to what Ivan said, a quick fix for the tail rod rattles is to purposely offset the guides on the boom such that the rod as a SLIGHT bow to it, thus forcing it to lightly touch the guide instead of banging around in it.
Gixxer
04-21-2006, 11:33 AM
Thanks PlayF ill check that out today and see if I can get it to pipe down a little. I also didnt want to put un-needed resistance on the servo if i didnt have to but ill try a few different configurations this evening!
Has anywhere put together a complete bolt package to replace the phillips bolts or do you just have to order them all individually... this phillips head things gotta go!
Any why they didnt put at least nylon lock nuts with the phillips bolts we'll never know........
ChrisLaFollette
04-22-2006, 05:49 PM
If you want to convert the rudder pushrod to CF id reccomend one of the MinAir pushrods. Either for the Fury or for the Gasser (the gasser has a little brass sleeve on one end). You will have to cut the rod to size but it should be fairly easy and the rod will fit through the stock boom support "big holes". Good luck.
The screws in the hirobo kits need the JIS screwdrivers. They are not phillips, and having the right screw driver helps a bunch.
As far as not having nylock nuts on them, I don't know, but I haven't had any of them come loose either. I usually check them on the windy/rainy days.
kcasser
07-13-2007, 04:58 PM
Gixxer,
I realize I'm late to the party, but did you find out what was causing your tail rod vibration? I have the same problem, but my fins (horiz & vert) are buzzing, too. I noticed the problem when my tail rod sheared in flight - a clean break. Now I'm going crazy trying to find the cause. I've replaced the fan/hub. I've balanced them & dial indicated them within a .001" of their lives. I replaced the tail case completely. I changed the fins to carbon fiber. I tightened all frame bolts, etc. I'm losing my mind. Any suggestions?
I would definitely check the runout on the clutch shaft. Mine was out by ten thousandths or better. Since this is a solid shaft you will have ot get it centered and straight, meaning to check the run out at various places along the shaft and get it tweaked in that way.
If you replaced everything on the tail case including the blades and hub with known good parts that leaves something high frequency in the heli its self, which is engine problems. Typically, in my experience a tail problem will cause the horizontal fin to blur, and the vertical won't. If both are vibrating, that once again leads me to believe it is an engine related problem.
kcasser
07-14-2007, 10:24 AM
I took everything apart, again. last night. Pulled the main shaft to be sure it was true, checked the rotor head balance. Took the tail apart to check the tail shaft. Dial indicatored the main shaft and the tail rotor shaft - smooth as silk. I dial indicatored the clutch shaft, and it's bang on. Added CarbonXtreme fins, and they still vibrate at 1900 rpm. Checked it out this morning, and a friend says the horiz stab is vibrating only about 3-4 mm, but it's a blur to me. Maybe that's within spec, but I just don't have anything to compare it to. Everything I've read tells me the fins should look solid.
:arggg:
Maybe I'm imagining a problem that doesn't exist? I never noticed vibration on my Raptor 30 V1, but I wasn't looking for it, either.
If it is just the horizontal stab, then chances are it is in the tail. If both are vibrating, then there is the possibly there is something else.
Carbon fiber has high tensile strength, but it doesn't have as much rigidity as people think. The rigidity comes from the resin. A carbon boom will not be as stiff as an aluminum boom, so I wouldn't put a lot of weight on carbon fins not vibrating. Their big advantage is weight savings.
Have you pulled your tail grips apart to make sure the bearings are all stacked in the same way? Also if the tail blades are too tight in the grips, that can cause a problem since they wont find the center of the lead and lag. It would take a He-Man grip to get them that tight, but it is possible. If the blades are too wide for the grips this can cause a similar action, since the tail blades can be out of track that way.
To check for a straight tail hub, I take it off blades and all, from the shaft and grasp the blades and grips and use slight pressure as if to bend the hub and see if the hub turns in the grips. If it doesn't rotate it usually isn't bent enough to cause a problem.
I know how frustrating this can be, and after you get it straightened out, you will have learned something. :arggg:
kcasser
07-14-2007, 01:34 PM
Ivan
Thank you for your advice.
I pulled apart the tail grips - bearings are the same in both. Blades are not too tight in the grips, the swivel with minimal pressure. Regarding tracking, I did the thing where you measure from the boom to the tip of each tail blade, and they're within 1/16" of each other which I thought was fine considering how the thrust bearings allow so much movement. I did your check on the tail hub, and had no rotation at all. Also, I removed the bearings from each side to be sure they could be removed freely, and no problem there. I'll keep looking. :arggg:
I'm gone 'till Tuesday. Thank you for your help. I'll try the heli again next week if I'm lucky.