Honey Bee FP RC Heli Vibration Manifesto
Posted Sunday May 20, 2007 at 1:48 am
(3 years ago)
Does your Honey Bee FP have a vibration that you can\'t track down? look like it\'s being shaken apart by the paint mixer at Lowe\'s? Or is it just a skid that shakes a little bit and annoys the hell out of you?
The Short Version: Top Five Causes of Vibration
- main rotor blades not tracking together
- flybar out of balance
- bent main axis
- flybar not tracking
- training gear
The Long Version
If you follow these steps, you will fix the vibration—but it\'s going to take awhile to do everything. No real mechanical skill is required, but at least an hour (maybe longer) of focussed attention is crucial. As you work, remember that there are only a few parts that can vibrate. It\'s actually pretty simple to track down vibrations if you keep this in mind and try to isolate individual parts as you go. Vibration can happen for two reasons: either the parts are imbalanced, or one side generates more air resistance than the other as it spins.
Disassembly
- If you\'re using training gear, take it off for now. (That may fix the problem right away—more on training gear at the end.)
- We\'re going to start by taking your helicopter apart.
- Pop the servo push rods off of the swash plate by applying gentle pressure with your fingers.
- Use the hex wrench that came with the heli to loosen the grub screw on the main shaft retaining collar under the swash plate.
- Push the main axis downward through the main frame about 5mm. Don\'t let the big gear go down as well—you want to get the main axis sticking out below the gear.
- Remove the shear pin in the bottom of the main axis. You should now be able to slip the main gear off the bottom.
- Pull the main shaft and the entire head assembly out of the frame from the top. Don\'t force it through the bearings! You may have to sand the bottom of the shaft a little bit first.
- Slip the silicone tubing off of the tail shaft, and remove the tail blade, and tail gear. Your heli should have no spinning parts other than the motors at this point.
Motors
- Motors are unlikely to cause a major vibration by themselves, but
they\'re easy to check. Plug the heli in and hit the throttle. If it
vibrates:
- Unplug the tail motor from the 4-in-1. Throttle up. If it doesn\'t vibrate, you need to replace your tail motor.
- Repeat the step above with the main motor.
Tail
- Reassemble the tail rotor. Make sure the heli is held down
securely, then throttle up. If it vibrates, it\'s either:
- An unbalanced tail blade (one side is heavier than the other).
- A bent tail shaft (unlikely since they\'re carbon fiber, but easy enough to check).
- A warped tail gear (unlikely to cause noticeable vibration).
- Bad bearings (extremely unlikely, but possible.)
Main Axis
- Set the heli aside and get the rotor assembly. Remove the shear pin that holds the head on the main axis (similar to the shear pin that held the gear at the bottom, but smaller). You can do this with needle-nosed pliers.
- You should now have the main axis separated from everything else. Roll it on a glass table top, or chuck it in a drill and spin it up. If it\'s bent, you need to either get a new one (easy), straighten it (hard), or make a new one (requires a drill press and 3mm steel shaft).
Flybar Balance
- If your main axis is straight, move on to the rest of the head assembly. Pop the ring-like push rods off of the rotor head. Gently pull on the rotor head until it pops off of the bearings on the center hub. (This takes some pressure and you\'ll feel like you\'re breaking it, but you\'re not.)
- Pop the longer pushrods (the ones that look like dog bones) off of the paddle control frame. Remove the swash plate.
- Put the main axis back in the center hub, and reinsert the shear pin. You should now have a rotor head that has a flybar but no swash plate and no main rotors.
- Drop the main axis back into the heli\'s frame. Give it a spin. It should spin very freely—if not, check the bearings. (Again, it\'s very unlikely that the bearings are bad, but it is a possibility.)
- Hold the helicoter vertically (nose pointing at either the floor
or the ceiling). With your other hand, rotate the flybar until it is
level (perpendicular to the heli\'s frame, or parallel to the
floor.) When you let the flybar go, does is move?
- If the flybar moved, whichever side went down is heavier than the other side. You\'ll need to loosen the two grub screws on the underside of the paddle control frame, then slide the flybar one way or the other until it\'s balanced. Don\'t forget to retighten the screws!
- Alternatively, if your flybar still has the weights on (which I don\'t recommend for anyone, by the way), you can move them slightly to bring the flybar into balance. I recommend you used the first method though.
Flybar Tracking
- Look at the flybar in profile. Are the paddles lined up perfectly with the paddle control frame (i.e., do they pass through the same plane)? If not, loosen the screws and twist them until they\'re correct.
- Reassemble the swash plate, push rods and servo links, retaining collar, and main gear. Your heli should now be completely assembled except for the main rotors. Do not put the main rotors back on yet!
- Plug in your battery. Keep a good grip on your heli and spin it
up. If there\'s any vibration:
- Are both paddles facing forward? The leading edge is more rounded than the trailing edge.
- Is there a problem with the angle of attack on your paddles? Make absolutely sure that they\'re spinning in the same plane as the paddle control frame.
- Although it\'s unlikely, the vibration could be attributed to your main gear. They all look like they wobble an awful lot, but I\'ve never seen one that was bad enough to cause a serious vibration. You can always pop in a new one and see if it fixes it though.
Main Rotor Balance
- Take your main rotor assembly (both rotors should still be attached to the rotor head). Put two drinking glasses side-by-side, and rest the balls of the rotor head on the rims of the glasses. The rotors should tip freely, like a see-saw.
- Use a ruler to determine if one blade tip is higher than the other. (You need to be certain your work surface is level as well.) Add tape to the leading edge of the lighter blade until the assembly is level.
Main Rotor Tracking
- Reinstall the main rotor by snapping it back into place and reconnecting the ring-like push rods.
- Hold down the helicopter and throttle it up. If there\'s still
vibration, the blades need tracking.
- If there\'s not already a colorful marking on the end of one blade, make one. White-Out works well. It doesn\'t take much.
- Spin up the heli, and look at it from the side. You should be able to see if one blade is moving in a higher plane than the other blade. You can tell which blade it is by the marking you made in the last step.
- Grasp the blade that\'s tracking lower at the base, and use your other hand to twist that blade downward. This adds pitch to the blade. Be careful not to apply pressure to the rotor head when you do this.
Hub and Head Parts
- If you\'ve still got a vibration at this point, you probably have a problem with the rotor head or center hub. Replace these and the vibration should go away.
Training Gear
- If there\'s no vibration at this point and you want to use training gear, you can reattach it now. Training gear cannot cause vibration by itself, but it can amplify an existing vibration that would otherwise be acceptibly mild. If you can\'t hover yet, don\'t fly without training gear—fix it!
- If the helicopter vibrates with the training gear but not without, try adjusting the position of the ping-pong balls. Move them in a cm or so and see if it makes a difference. Continue with trial-and-error until you find a position that works.
That\'s it! Hopefully you found what you needed there somewhere. It can be a finicky little machine sometimes, so don\'t be completely bummed if there\'s a new vibration tomorrow. A jiggling skid is nothing to worry about; just take care of the big things and the things that are easy to fix.