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CanoMod . Futaba-RC . A Main Hobbies

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e-Robbe Eolo > Tail Vibes problems
 
 
guillaume83
Senior Heliman
Location: Toulouse (France), home of the A380

Hi all,

I have finally put my Eolo back in the air last week after 8 months taking the dust or so....
I originally purchased this heli 2nd hand and it was flying great til I had a small mishap and had to rebuild the heli...ever since I have had tail vibes.

Let me explain: I have some vibes in the tail during spool up,i can clearly see the carbon fin shaking....when i then fly,i get vibes only when i use the tail rotor...say i apply lef or right rudder and the tail then vibrates when i stop applying it.


I thought it was coming from the bearings in the tail when i last flew the heli in August,and i never tried to get round the issue...when i decided to put the heli back in the air last week,I ordered an extra set of HeliUp BB upgrade for the tail boom,meaning i could put 6 BB in the boom if I wished....but i decided to "only" use 5,thinking that was my problem gone...

Problem is,when i flew last WE,i still had the same tail vibe problem.After 4 flights,I even had a tail rotor failure in flight and the heli started spinning on it self at a fair height.Luckily,I was only hovering and had no speed,I attempted a landing straight away and the heli suffered minor damage (tail rotor bridge broken,flybar and vertical stab)...my cheapest crash ever in fact,but the most impressive for sure!

After investigation,it appears that the tail drive short (S5114) failed (the one in the heli,not in the tail).....it just sheared

I am now wondering if the vibes and this failure were linked in any way.

I first thought the vibes were due to a less than smooth movement of the tail rotor assembly on its shaft,so i oiled it..also,i made the mistake not to assemble the tail gearbox and the tail drive bearing block assembly on their own...I screwed the lot with the boom on...so i corrected this and thought i would get rid of the vibes.

What i am now thinking is that the shaft is not spinning true by the tail drive short,and by putting the HeliUp BB to close to it,this is produving vibes because the shaft is trying to spin untrue but the BB is stopping this happening...what do you guys think? this would explain why the tail drive short failed,i cannot see any other explanation.so if i put the BB a bit further to allow more flexibility of the shaft,i should be fine?????

Tonight,i spooled up the heli in the living room,and i still have vibes on spool up..i have to fly it yet and see how it behaves airborne,but i sure would not like the tail drive short failure to happen again.

My set up is:
Twist 37 with TP 3s3p 6000mAh or 10xCP1700
All QUick UK
Nearly all HeliUp
GY401/9253

One of y other problems is that i am not familiar with the GY401 and its initial setting even though i have been reading a lot about it,but it doesn't feel like tail wag.

Any help/comment would be appreciated.My Eolo is more detailed in my gallery if you want to have a good idea of my set up.

many thanks,

Guillaume
02-24-2005 Over year old.
 
 
Reesy
Key Veteran
Location: In the doghouse ... Nottingham UK

Bonsoir Guillaume
Comment ca va?
I had the 9114 bend very easily,unfortunately the best solution is to replace them (both ends) and if they are OK ..well you have spares if the vibes come with FF flight maybe tha gain is too high try turning it down slightly, I tried stock robbe tail blades then hirobo77 but I ended up cutting them down to about 72mm

The 401 is very simple (just don't read the instructions ) what headspeed are you running?

Ting Tong
.... ...... ...from Tooting
02-24-2005 Over year old.
 
 
guillaume83
Senior Heliman
Location: Toulouse (France), home of the A380

Reesy,

merci pour ta reponse

I have no idea what headspeed I am running.
Around 2000 is my guess.

The vibes do not happen during FF,no way I am going to do FFif i am not 100% confident with the tail's behaviour!!!

This is my problem.I cannot do what i want because i am not confident with the tail.
I have changed both S9114....just to make sure the ones I had would not break (had spares ones in my box but they were probably changed by the previous owner after a crash).

What do you think of my theory with the HeliUp BB?

I am going to mount the tail drive bearing block the other way ("upside down") just to see if the shaft is still misaligned with the boom (off centre).


About the GY401,I am not sure about the initial setting,how to set the rod length....some people say not to bother,so say you should adjust it in normal mode so that the heli is not yawing...

Is it fairly normal to get vibes on spool up or is it an early indication of vibes in flight?

Thank you.

Guillaume
02-25-2005 Over year old.
 
 
Reesy
Key Veteran
Location: In the doghouse ... Nottingham UK

401 first I have it at 80% in idle1 and normal (HH) and 20% in idle2 (non HH) hover around in 1 then flip to 2 if tail moves land and adjust linkage et voila .. probably not too important but I like things right.

I don't know about your other idea but had a lot of fiddling with gears etc before I had it running smooth, the tail gears were quite mashed after one crash, you just have to go through each bit until it's all smooth.

Shaking on spool up doesn't mean anything, my Raptor looks like a doggy been for a swim until it's in the air.

Ting Tong
.... ...... ...from Tooting
02-25-2005 Over year old.
 
 
tanasit
Heliman
Location: Philly

guillaume83,

In stead, I will remove the main blades and run it up to see if the vibration is still there. If so, I will remove the tail blades and do the same. If the vibration disappears, then either the main and/or the tail blades are out of balance.
Also, if it is the vibration on the tail horizontal fin (up/down motion), it is likely that the tail blades is not balanced, but if the vertical fin vibrates sideway then check the rotor head and main blade balance.

I will also check the boom support if anything loose.

You mentioned the tail vibe only when you give the rudder input. This is strange but I will check if the tail drive shaft is true.

As for the GY401, set the rudder servo to neutral and set the linkage so that you have a small amount of tail pitch for "right" yaw. Then set limit on the 401 while moving the rudder to extreme and set it so that the throw won't go beyond the physical limits on both ends. Next, turn on with HH setting and once the LED turns steady red, flip to normal mode and start to lift off to set the rudder trim (you may have to reset the linkage if the trim can't correct). Also you may want to set ATV of gyro channel if the tail hunts. My setup is at 40% and the delay is set to minimum. Next, flip back to HH mode and set the rudder trim while trying to hover. Last, you want to fly up high and flip to idle up and again, set the rudder trim.

Hope this help.
03-02-2005 Over year old.
 
 
HeliDuce
Senior Heliman
Location: Nashville, TN

Simular Problem...

I had simular issues with the tailfin vibrating and thought like you that it was due to the bushings inside the tail drive shaft. I bought the upgrade ball bearings and it didn't improve much. I then made some carbon fiber boom supports using 2mm carbon fiber rod and some heavy plastic ball links. They are attached to the landing gear legs at the back with sheet metal clamps I made for about 2 cents each. I then formed the sheet metal around the back legs and drilled holes in the sheet metal to clamp onto the ball links. I fashioned another sheet metal clamp on the boom that captures the two supports and connected them using some left over parts from another project. I have absolutely no tail vibrations now. It has completely changed the handling of the heli! I was able to raise the gain on my gyro from about 50% to 75% with no tail wagging. It also improves the overall control since the gyro isn't being effected by the tail vibrations. You can either buy the twin tail boom supports for around $55.00 or make your own for around $10.00.

Gary
03-02-2005 Over year old.
 
 
Stet
Elite Veteran
Location: Long Beach CA

First off, 80/20 is a bit too high a gain if you are using dual mode and those numbers translate to a gain of 60% 60%. If you mean 80% your gain is much too high. Turnn it down to a real gain of 40% 40% and inch up a bit only if you need to for your style of flying. But this is not your issue with the tail

For the wire drive ends:

1) I found one of mine was drilled wrong and the hole for the wire was not in line with the axis of the part. Install the wire and spin in your fingers to see if this is the case. If so replace the part

2) If it is straight, you will notice that when the wire is installed, the set screw pushes it to one side slightly. Not much you can do about this. It is too bad there are not set screws on each side. If you overtighten the set screw you will make this worse, if you undertighten the screw the wire will come loose.

3) Because of #2, you want to have a good bit of distance between thee fitting and the bearing in the boom, I would say 3 inches is what I have.

4) Make sure you have proper mesh of the tail gears in the tail box. Make sure they are tight yet have a perceptible lash the whole way through the contact path. This means rotate the input shaft 10 degrees at a time and make sure that when you rotate the tail hub back and forth you feel some movement in all positions. The less movement the better, but some perceptible movement along the whole path.

For the tail gears I used to use Bosch purple grease, but it would dry up and come off the gears, so now I use the thick silicone grease that is used in the gas car differentials.

5) Make sure no part of your tail rotor hub is bent

6) Make sure your tail output shaft is not bent.

I had a lot of problems with my tail shaking, and my problem was #1 and #2 above. Personally, I think it is silly to use gears and shaft and look forward to the new belt setup which will eliminate all of this hassle.



keepin' it real
03-02-2005 Over year old.
 
 
dnam
Veteran
Location: Herndon, VA - USA

...
03-02-2005 Over year old.
HOMEPAGE  
 
 
dnam
Veteran
Location: Herndon, VA - USA

It seems the belt drive can be bought at www.robbe.com for 63.19 EUR.

http://at.robbe-online.net/cgi-bin/...7183e0dc121059a

Only problem is the 50 EUR shipping charge so one has to order a lot of stuff at one time for it to be worth it.
03-02-2005 Over year old.
HOMEPAGE  
 
 
Stet
Elite Veteran
Location: Long Beach CA

Keep up with Alex at eRCMarket and get it from him. Shipping would be about 8 euros. I want the fuse kit too.

keepin' it real
03-02-2005 Over year old.
 
 
dnam
Veteran
Location: Herndon, VA - USA

Thanks! I wrote an e-mail to Alex and the answer was that the belt drive will be available on his website in about a months time.
03-03-2005 Over year old.
HOMEPAGE  
 
 
Stet
Elite Veteran
Location: Long Beach CA

I am wondering how that belt system integrates into the main gear, I doubt it is going to drive off the crown gear

keepin' it real
03-03-2005 Over year old.
 
 
dnam
Veteran
Location: Herndon, VA - USA

Yeah, I was wondering about the same things as you Paul. I was just about to purchase the belt drive from www.robbe.com today, but then started thingking on how the heck can I mount it as there doesn't seem to be anything that would mesh with the main gear.

BTW I too have tail vibration problems. I can't get the throttle above 65% as then it starts to vibrate like crazy! The horizontal fin oscillates with a really high frequency and great amplitude. Since the horizontal fin vibrates I took off the tail blades to see if the vibes originate from there, and what do you know, they do come from the blades. Without them the heli is smooth as silk, even at full throttle.The strange thing is that the tail rotor is totally balanced and the tail vibrations actually go away once in a while. Most of the time when I switch above 65% throttle is starts to vibrate, but on a few occasions it stayed smooth. First I thought I might have the tail blades too tights, but no amount of loosening/tightening makes any difference. I am very baffeled by all this. Any suggestions?

I ordered some stock tail blades and will try them to see it that helps.
03-07-2005 Over year old.
HOMEPAGE  
 
 
Reesy
Key Veteran
Location: In the doghouse ... Nottingham UK

Look for Garth2's notes on this the stock tail blades were WAY out of balance, I'm running the hirobo L72 blades but found I was running the gyro gain a wee bit too low so have cut them down.

Try balancing first

Ting Tong
.... ...... ...from Tooting
03-07-2005 Over year old.
 
 
tanasit
Heliman
Location: Philly

dnam,

Since the vibe goes away when you remove the tail blades but you said,"the tail rotor is totally balanced". Are you sure about that? Beside the total weight, did you do the cordwise CG check? Better yet, you can remove the tail drive shaft together with the rest toward the blades side and balance the whole unit. You may want to make a balancing weight attached to the shaft end so it will stay on the balancer or you have to find the metal rod with the same diameter of the shaft but longer. I've experienced with this annoying tail vibe with many of my machine too. You may want to try a new set of tail blades because some will only static balance but not dynamic even though the blades are balance but the flaws in the or even the holes in the root are not exactly at the same angle or the root thickness of one blade is a bit off, or etc...
03-07-2005 Over year old.
 
 
dnam
Veteran
Location: Herndon, VA - USA

Thanks! I ordered new tail blades so should have them soon. I hope they'll cure the tail vibe issues as it is a real PITA especially on such a nice SE kit!

Hey Reesy,

I just sold my Freya X-spec to a very nice gentleman (actually it's Dakine who was selling off his 35 helis recently). Anyway at last I have the funds to buy a 3DMP, so I'll be joining you guys soon on the Henseleit forum! Can't wait!!!
03-10-2005 Over year old.
HOMEPAGE  
 
 
Stet
Elite Veteran
Location: Long Beach CA

My vibs come and go. I think it may be something about the tail gears, and the torque wire loading and unloading. Sometimes it is silky smooth, then other times I get surging in the tail rotor and a wag, especially when the system slows down as the battery gets lower.

I ended up cutting the paddles further, this seems to have helped the overall vibration in the heli. It flies about the same, perhaps just slightly more responsive, but less vibration for sure. I have the paddles within 1 grain of each other in weight, and measured exactly the same distance from the seesaw assembly ends (at the end of the flybar ball connectors). So I think getting rid of some of the paddle weight helped. I tried the Robbe light paddles with the shrink wrap, and they worked ok, but I could not get the shrink wrap to work right behind the paddle holder fitting. I wish Robbe would not have cut out the area behind the paddle hoder fitting, it sure would have been much easier to cover had they not done that.



keepin' it real
03-10-2005 Over year old.
 
 
epilot
Heliman
Location: Brisbane Australia

There is one more point to consider...
Any long driveshaft is subject to flex (more like a twist) due to torque applied by the TR.
The BB are there to minimise the effect but may not be succesfull du to
varying stiffnes along the driveshaft.
In other words it is importent to have the BBs but put them in the right place is the tricky part.

The spacing should never be even to prevent harmonics.

I have installed the the shaft in a router and driven the TR like that.
Inspected the vibes and moved the BBs to the flex spots.
Works!
The mass at the end of the boom is important too. If it is too little the TR vibes are easy to excite. Specially when the TR is slightly imballanced.

Sometimes removing or litening the VF is a bad move.

Boom supports help as well of course.

I am not a prof in Helis unfortunately. Just had a lot of time while waiting for spares to arrive in far Australia


Talk Future , Talk Electric...
03-12-2005 Over year old.
 
 
Stet
Elite Veteran
Location: Long Beach CA

I have the 3 bearing setup, and I made sure that the spacing was not symmetrical allowing a sine wave harmonic in the boom.

I have more of the bearings, and I might consider adding another, but I am fighting tail heavy cg issues already. I think your point about the twisting of the wire may be a big part of my issue. The torque rod acts as a torsional spring. I would like to see a stainless tube torque tube, or the belt drive which is forthcoming. I think the belt is the easy answer and will lead to a much improved tail performance. We will see, I will report as I will have one on order as soon as Alex or Jeremy gets them.

I also just upgraded my tail blades from modified MS85's to the spendy Robbe tail blades, and it seems there is a bit of improvement from that too now.

keepin' it real
03-12-2005 Over year old.
 
 
dnam
Veteran
Location: Herndon, VA - USA

Tail vibe problems solved!

Hey guys!

Today I received the new tail blades for my Eolo, but after trying them on (they were spot on with my magnetic balancer, so no need for balancing) the same tail vibrations were still there above 65% throttle!

I was getting really p***ed, but then a thought occured. It turns out the vibrations were caused by resonance. To change the internal frequency of the resonating elements I zip tied fuel tubing to all areas that were vibrating like mad. Now the heli is totally smooth up to 100% throttle!!!!!! Tomorrow looks like it will be fun!





03-13-2005 Over year old.
HOMEPAGE  
 
 
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e-Robbe Eolo > Tail Vibes problems
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