Go Back  RCU Forums > RC Helicopters > Electric RC Helis > E-Flite Helicopters
Reload this Page >

BCX2 Flybar Frustrations

Notices
E-Flite Helicopters Discuss the line of E-Flite mini and micro helis including the Blade CP, CP Pro, Blade CX, etc

BCX2 Flybar Frustrations

Old 03-20-2007, 03:46 PM
  #1  
joyboy
Junior Member
Thread Starter
 
Join Date: Jul 2005
Location: Annandale, NJ
Posts: 12
Likes: 0
Received 0 Likes on 0 Posts
Default BCX2 Flybar Frustrations

Been flying a new BCX2 since Christmas getting progressively better while spending money like a drunken sailor at my LHS on parts (mostly blades).

Anyway, my latest problem is proving to be incredibly frustrating and I'm hoping to tap into some of the expertise here to help me solve it. I'm having some severe wobbling problems at any kind of RPMs. I have narrowed it down to the very top blades/flybar. Basically, I get absolutely no shake at all until I assemble the top blades & flybar. Everything else is true and tight - just as it should be. The blades all fit extremely smoothly and move without any resistance at all. Likewise, when I attach the flybar everything is super-smooth. But the thing shakes like something is very wrong. I bought a brand new flybar today and put it on - it flew great until I tipped it over on the floor on a takeoff. After that, everything was a disaster. I barely touched it - this wasn't even a crash, but it is unflyable again. The flybar, when pulled off the helicopter, rolls smoothly and doesn't appear to be bent. As near as I can tell it is well balanced, but it sure seems to be the source of my problems. Can anybody give me some advice?
Old 03-20-2007, 04:42 PM
  #2  
Gene Valjean
Senior Member
 
Join Date: Feb 2007
Location: Fresno, CA
Posts: 121
Likes: 0
Received 0 Likes on 0 Posts
Default RE: BCX2 Flybar Frustrations

Perhaps your top blades arent balanced. If you have a digital scale you can figure it out, and add some tape or colored stripes to balance them out. Also, make sure the head is secured to the inner shaft via the screws tightly. Other than that, I dunno.
However, a nice little mod i did for learning was taking the screw that holds the flybar in place OFF. This way, when you do crash, in most cases, it will just pop off instead of bending. Hope this helps.
-Gene
Old 03-20-2007, 05:26 PM
  #3  
soloboss
Senior Member
 
Join Date: Sep 2006
Location: Fort Wayne, IN
Posts: 2,177
Likes: 0
Received 0 Likes on 0 Posts
Default RE: BCX2 Flybar Frustrations

The first step for me when I had (have) these problems is to isolate the source. You have several places where the vibration can come from.
Flybar, upper rotor, lower rotor, outer shaft, inner shaft. If anything listed is out of whack, it will wobble the shaft assembly which makes the flybar think it's out of balance (even if it's fine!). SO, try this;

First remove all of the blades and the flybar. We need to verify the shafts.
When I get a bent shaft, I use this trick to isolate the two shafts so I can determine which shaft it is.
Move the throttle stick to the far right and then add a little throttle. That will run just the upper (inner) shaft. Move the stick to full left and add a little throttle to check the outer shaft. Got it? So, how did you do? Shafts straight? I have a straightening section below. If the shafts are good, your head should spin up to about half rpm and show no wobble at all. No need to run it at full RPM because with the blades on, the rotors will never spin that fast.
On the assumption that your shafts are good, drop the flybar into the hub on top. Fold the linkage over the top and stick it down with a little tape. You don't want that link to throw the balance off. Now spin up to about half throttle - just spin the inner shaft. OK? Now spin both of them. If you suddenly have a wobble that wasn't there with either single shaft, check to be sure your bearings are seated. I changed to the aluminum bearing cups and new bearings (it's a kit) and my heli got more steady. If your flybar caused the wobble, you know what to do. If not, remove the flybar and install the LOWER blades. Spin up the lower rotor. If you get wobble, you have out of balance blades or the pitch of one of the blades of goofy. Replace (DON'T Discard) the lower blades and try a again. We've seen blades that are balanced statically (with a scale or balance) but don't have the same pitch. If you get a shake out of the lower rotor, that will cause the entire inner / outer shaft assembly to wobble a bit. That throws the flybar off-center which makes the flybar hub spin off-center, which bends the flybar rods slightly and shakes the heli. But it looks fine when you look at it stopped.

OK, Let's assume that the lower rotor is spot-on. Remove the lower blades and install the upper blades. Do they move freely? Will they rotate when you pass your hand over them creating a little air movement? If not, fix it. If they move freely, spin up the upper rotor. How's the balance? No wobble?
So we have verified both shafts, the lower blade pair (separate blades don't count - you only verify pairs), the upper blade pair, and the flybar. Now connect the flybar to the hub. Check the ball on the upper blade where the flybar link will connect. Is it perfectly smooth? Do you use needle nose pliers to push the ball through the loop on the link? If so, look for a burr from the pliers. The ball has to be perfectly smooth. Snap the link onto the ball. Everything is absolutely free and almost moves by itself, right? Now spin the upper rotor - Hang on. Let's see those safety glasses. You think you use a lot of blades now, try flying blind! OK, spin the upper rotor only - and spin it fast enough so it tries to lift the heli. Checking blade tracking at low RPM is worthless. Bad tracking shows when the blades have lift. Is your tracking right on? If not it causes shake. Fix it.
Hmmm, what have I missed? If it still shakes, look at the lower blades and spin them up - just the lowers, and put some power to it. Look at the tracking of the lower blades. Of it's off, it's the blades and they gotta be replaced. The lower rotor can suffer tracking issues, but there's not much you can do about it other than swap blades. Anyhow, if you keep swapping lower blades and one of the blades keeps showing in the reject pair, you got a dud. It happens. It's a buck. Deal with it. Or boil it in water. It may return to the correct form.


If you had a bent shaft, we need to straighten the bad shaft.
If it's the outer one, I take the inner shaft out, spin just the outer shaft and very lightly touch it with a felt tip to make a mark on the 'high' side. Then I pull it out, support the shaft on the ends and thump it on the felt tip mark, and try it again. With your heli lying on its side, you don't have to assemble the heli to run the outer shaft. Just stick it through the bearings and engage the drive gear and run it again with the heli on its side. TIP: It takes a pretty good thump to bend the outer shaft. It takes very little to bend the inner shaft. Keep working at it and you’ll get it. I’ve straightened mine several times.
The inner shaft is easy. You need a flat surface (table) so you can drop the flybar hub off the edge – then roll the shaft looking for the bend. Straighten it gently. It’s really soft rod. Or get a drill rod and make your own. Use a Dremmel and cut it to length and grind the little flats on it. The drill rod won’t bend and there’s no weight penalty. You want a 0.078 diameter rod. What’s that in fractions?? You, there in the back row asleep – yes YOU!! C’mon, divide 5 by 64. The calculator shows 0.078, thus .078 is a 5/64ths drill rod. And you thought you couldn’t do this.

Lots of words. That's just me. Maybe the answer to your problem lies in one of these suggestions. And of course, if anyone disagrees with my 'article', post my error. We all learn.
GOOD LUCK!!
Old 03-21-2007, 02:11 PM
  #4  
joyboy
Junior Member
Thread Starter
 
Join Date: Jul 2005
Location: Annandale, NJ
Posts: 12
Likes: 0
Received 0 Likes on 0 Posts
Default RE: BCX2 Flybar Frustrations

Soloboss,

First off, thanks very much for the detailed response. That's pretty much gold for anybody with the shakes.

I stepped through your advice point for point and everything checked out perfectly. I ended up swapping out the upper blades *again* from a new package, and everything works perfectly again. A little bit of experimentation shows me that *any* pair of upper blades from this one pack create a terrible wobble. Pairing a single blade from that pack with another known good blade makes it wobble so bad that it almost falls over. I suspect that weighing them might end the story, but lacking a scale I'm opting for the garbage and calling it a bad pack. Didn't know that could happen.

In any case, thanks for all of the help.
Old 03-21-2007, 04:53 PM
  #5  
soloboss
Senior Member
 
Join Date: Sep 2006
Location: Fort Wayne, IN
Posts: 2,177
Likes: 0
Received 0 Likes on 0 Posts
Default RE: BCX2 Flybar Frustrations

Joyboy, you happy lad,
Go get 'em outa the trash - QUICK!
I've heard of a tale of woe starting with good blades that ended up on the bottom of a large container getting squished under the weight and thereby becoming deformed. Poor blades. Anyhow, the blades can be returned to their original shape by boiling them in water for a bit. Just enough to rehydrate them, restore the original shape, youthful luster and . . . never mind. It's been a long day.
Anyhow, word is out that they can be boiled in water and that will sometimes restore the shape to original. If they are warped they won't work in pairs or - obviously they won't work alone. Hmmm. Give it a try. All ya got to loose is hot water. And you might save FOUR WHOLE DOLLARS!!

I'm not always right, but the price is . . . priceless! Yep. It's been a long day.
Old 03-26-2007, 09:43 PM
  #6  
slip_stream
Junior Member
 
Join Date: Oct 2006
Location: Folsom, PA
Posts: 8
Likes: 0
Received 0 Likes on 0 Posts
Default RE: BCX2 Flybar Frustrations

Follow the instructions of soloboss. Pretty much after a crash, or if my chopper vibrates, i break everything down, balance, check, and make sure that everything is running smooth.

example make sure that the inner and outter shaft dont shake. Run the chopper with out any blades.

Put on the bottom blades, run the bottom blades. Make sure that there is no shake, they are balanced, and that they spin on the same plane.

put on the flybar, run the top rotor, again, level, and no shakes.

put on the top rotors, balanced, and again, they spin on the same plane.

Note, the blades on the top near the hub, have numbers, make sure that they numbers match. If they dont its almost guaranteed they are different weight.

This will get you a chopper that does not shake in the air.
Old 03-27-2007, 04:40 PM
  #7  
soloboss
Senior Member
 
Join Date: Sep 2006
Location: Fort Wayne, IN
Posts: 2,177
Likes: 0
Received 0 Likes on 0 Posts
Default RE: BCX2 Flybar Frustrations

Slip_Stream,
Thanks for the vote of confidence. I still find that the more detailed I am with the setup, but better the little bird flies. Details matter, and at about 180 grams, they matter a lot!
The flybar is the bugger that drives this whole thing and if it's not dead straight, it's wrong.
Anyhow, back to stuff,
Soloboss

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2021 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.