CX2 Vibration and TBE After Crash
03-01-2007, 09:37 PM
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CX2 Vibration and TBE After Crash
I smacked my CX2 pretty good today - hit the concrete wall in my basement and fell about 5 feet. Broke both lower blades, one upper blade, and mangled the flybar. I've replaced all the blades and the flybar, and when I throttle up, the helicopter shakes quite a bit. In the air it's controllable, but definitely showing some TBE when I let go of the sticks. I can't see that the inner or outer shafts are bent, but they could be. Could this be a blade out of balance?
Is there an easy way to balance the blades??
7ECflyer
Is there an easy way to balance the blades??
7ECflyer
03-01-2007, 10:05 PM
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RE: CX2 Vibration and TBE After Crash
It sounds like you may have a bent inner shaft. I've experienced the same thing myself. What I do to check it is to remove both upper & lower blades and then power it up till both motors just start spinning. Take a look at the upper head and you can usually see the wobble. If you suspect it is the outer shaft, remove the inner shaft and do the same thing over again.
To balance your blades (you should always balance them) put them together off of the heads and rest the "balls" on two drinking glasses that are of the same height. See which blade raises up and add some scotch tape to the underside of the high blade out near the tip. Put a little on at a time and recheck the balance till both blades are level to your work surface.
Jim
To balance your blades (you should always balance them) put them together off of the heads and rest the "balls" on two drinking glasses that are of the same height. See which blade raises up and add some scotch tape to the underside of the high blade out near the tip. Put a little on at a time and recheck the balance till both blades are level to your work surface.
Jim
03-01-2007, 10:11 PM
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RE: CX2 Vibration and TBE After Crash
Jim,
That's a good idea. I'll remove the blades and check the shafts. Just playing around swapping blades I managed to almost eliminate the problem, but there's still a little vibration and TBE. That really makes me suspect the blade balance. Battery's dead now, so I'll have to wait a couple of hours to check the shafts.
Jay
That's a good idea. I'll remove the blades and check the shafts. Just playing around swapping blades I managed to almost eliminate the problem, but there's still a little vibration and TBE. That really makes me suspect the blade balance. Battery's dead now, so I'll have to wait a couple of hours to check the shafts.
Jay
03-01-2007, 10:50 PM
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RE: CX2 Vibration and TBE After Crash
After a big crash, I remove the upper and lower blades completely, and spin up the shafts to check for bends/vibration. This isolates the problem and lets you determine if it's the shafts or the blades. With the blades removed, move the left stick far left and bring the throttle up. Only one shaft will spin. Repeat by moving the the left stick right and bringing the other throttle up. That'll help you narrow down which of the shafts is bent, if either (or both). Then, you can move on to deal with blade balance.
As far as replacing the flybar... just because it's new doesn't mean it's not bent. This is a big cause of TBE. Roll it on the table (rubber ended weights attached) and see if there is a bend in it. Even a little bend makes a big difference. I've purchased new flybars that have more bend than the mangled ones I replaced. Also, make sure the flybar moves very freely in it's holder... it should bounce easily from top to bottom a few times, if you give it a flick with your finger. If there is any binding in teh flybar at all, that will cause TBE. You may need to slightly sand the ball on the upper blade the flybar linkage attaches to, if this is the case.
As far as replacing the flybar... just because it's new doesn't mean it's not bent. This is a big cause of TBE. Roll it on the table (rubber ended weights attached) and see if there is a bend in it. Even a little bend makes a big difference. I've purchased new flybars that have more bend than the mangled ones I replaced. Also, make sure the flybar moves very freely in it's holder... it should bounce easily from top to bottom a few times, if you give it a flick with your finger. If there is any binding in teh flybar at all, that will cause TBE. You may need to slightly sand the ball on the upper blade the flybar linkage attaches to, if this is the case.
03-02-2007, 12:42 AM
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RE: CX2 Vibration and TBE After Crash
I did exactly that to check the shafts. The outer shaft is definitely bent (slightly), and I'm pretty sure the inner shaft is too. That was a little disappointing because the blades were out of balance, and I'd hoped that was it, but that's RC flying. Since they're cheap, I think I'll replace both shafts, just in case. Now I have to figure out how to replace them. I haven't checked the manual, so I'm digging around here for information on how to do it.
The new flybar is straight. I rolled it on the workbench and all looks well. I also checked the ball linkage for binding, and it's good. Hopefully I'll get the shafts at the hobby shop tomorrow and get it put back together this weekend.
The new flybar is straight. I rolled it on the workbench and all looks well. I also checked the ball linkage for binding, and it's good. Hopefully I'll get the shafts at the hobby shop tomorrow and get it put back together this weekend.
ORIGINAL: ndoren
After a big crash, I remove the upper and lower blades completely, and spin up the shafts to check for bends/vibration. This isolates the problem and lets you determine if it's the shafts or the blades. With the blades removed, move the left stick far left and bring the throttle up. Only one shaft will spin. Repeat by moving the the left stick right and bringing the other throttle up. That'll help you narrow down which of the shafts is bent, if either (or both). Then, you can move on to deal with blade balance.
As far as replacing the flybar... just because it's new doesn't mean it's not bent. This is a big cause of TBE. Roll it on the table (rubber ended weights attached) and see if there is a bend in it. Even a little bend makes a big difference. I've purchased new flybars that have more bend than the mangled ones I replaced. Also, make sure the flybar moves very freely in it's holder... it should bounce easily from top to bottom a few times, if you give it a flick with your finger. If there is any binding in teh flybar at all, that will cause TBE. You may need to slightly sand the ball on the upper blade the flybar linkage attaches to, if this is the case.
After a big crash, I remove the upper and lower blades completely, and spin up the shafts to check for bends/vibration. This isolates the problem and lets you determine if it's the shafts or the blades. With the blades removed, move the left stick far left and bring the throttle up. Only one shaft will spin. Repeat by moving the the left stick right and bringing the other throttle up. That'll help you narrow down which of the shafts is bent, if either (or both). Then, you can move on to deal with blade balance.
As far as replacing the flybar... just because it's new doesn't mean it's not bent. This is a big cause of TBE. Roll it on the table (rubber ended weights attached) and see if there is a bend in it. Even a little bend makes a big difference. I've purchased new flybars that have more bend than the mangled ones I replaced. Also, make sure the flybar moves very freely in it's holder... it should bounce easily from top to bottom a few times, if you give it a flick with your finger. If there is any binding in teh flybar at all, that will cause TBE. You may need to slightly sand the ball on the upper blade the flybar linkage attaches to, if this is the case.
03-02-2007, 08:36 AM
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RE: CX2 Vibration and TBE After Crash
here is a guide with detailed instructions on disassembly/repair of the CX or CX2. Neall
http://www.dacaur.com/heli/bcxhelp/BladeCXAssembly.pdf
http://www.dacaur.com/heli/bcxhelp/BladeCXAssembly.pdf
03-02-2007, 08:33 PM
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RE: CX2 Vibration and TBE After Crash
Here's what I did based on Jim's description:
Remove the blades from the helicopter, and reassemble them with the screws. Now you have a single rotor assembly with the balls at the center. I used two wine glasses because they had very slender rims. Put the two glasses far enough apart so that the balls rest on the glasses. Set the assembly on the glasses and check the balance.
Here's a sketch...
Remove the blades from the helicopter, and reassemble them with the screws. Now you have a single rotor assembly with the balls at the center. I used two wine glasses because they had very slender rims. Put the two glasses far enough apart so that the balls rest on the glasses. Set the assembly on the glasses and check the balance.
Here's a sketch...
ORIGINAL: darticus
Can anyone explain the balancing procedure. I just can't picture what your doing in your procedure.Thanks
Can anyone explain the balancing procedure. I just can't picture what your doing in your procedure.Thanks
03-02-2007, 08:42 PM
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RE: CX2 Vibration and TBE After Crash
Thanks Neall. Found it while digging around last night. I got the two shafts today, so we'll see how it goes tomorrow.
ORIGINAL: ndoren
here is a guide with detailed instructions on disassembly/repair of the CX or CX2. Neall
http://www.dacaur.com/heli/bcxhelp/BladeCXAssembly.pdf
here is a guide with detailed instructions on disassembly/repair of the CX or CX2. Neall
http://www.dacaur.com/heli/bcxhelp/BladeCXAssembly.pdf
03-02-2007, 08:53 PM
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RE: CX2 Vibration and TBE After Crash
The blade balancing procedure using the drinking glasses is really important. It's made a huge difference in the flying performance of my heli.
03-03-2007, 12:53 AM
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RE: CX2 Vibration and TBE After Crash
Thanks Jim. I hope that helps some others. Using scotch tape to balance the blades worked like a charm.
Replacing the shafts was easier than I thought. The assembly manual in Neall's post makes it a snap. It took me about an hour, but that included disassembling, reassembling, discovering that I'd forgotten to transfer the brass washer and bearing from the old outer shaft to the new one, disassembling, and reassembling again. My battery is a bit too low for flying right now, but I powered up both rotors enough to see that the vibration appears to be gone.
These things are a joy to work on compared to my old Hirobo Shuttle!
Jay
Replacing the shafts was easier than I thought. The assembly manual in Neall's post makes it a snap. It took me about an hour, but that included disassembling, reassembling, discovering that I'd forgotten to transfer the brass washer and bearing from the old outer shaft to the new one, disassembling, and reassembling again. My battery is a bit too low for flying right now, but I powered up both rotors enough to see that the vibration appears to be gone.
These things are a joy to work on compared to my old Hirobo Shuttle!
Jay
