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Ribcracker · 07-08-2010, 05:03 PM

Guys, I'm rebuilding my EXI 450 after a wicked crash. After replacing the feathering shaft I discovered a lot of slop in the head. With the grips fully tightened to the horizontal shaft, I can rock them like a see-saw. The grips also have a lot of lateral end-play. I can pull the grips outward by an eighth inch or so even though they are fully tightened down.
What am I missing? Any ideas about possible remedy?

Bob O · 07-08-2010, 05:18 PM

Wrong feathering spindle?

Ribcracker · 07-08-2010, 06:08 PM

Thanks, Bob. But no, the spindle is the standard EXI part (31146) that I've been using since I've had the heli. The offending head is a cheap ($30) metal upgrade from Xheli which has been giving good service for a good while.
The original plastic head is tight and solid so I could always put it back on but I'd like to figure out what went wrong with the metal head.

Bob O · 07-08-2010, 08:05 PM

Something must have been left out upon reassembly. Did the washers and thrust bearings get put back in and in the correct orientation?

Ribcracker · 07-08-2010, 08:35 PM

You may be onto something. I'll take it back apart and do some forensics. Meanwhile, I did a search on "sloppy head" and discovered some other possible issues; the rubber dampers may be worn out. Some folks add a few extra to each side. Some folks shorten the feathering shaft to eliminate end-play. Also, I've heard that the thrust bearings could be damaged...or the seat where they sit.
Which is the thrust bearing? Is it the normal looking bearing or is it the bearing disk that is sandwiched between the two grooved spacers?
Thanks,
Bud

Patriot996 · 07-08-2010, 09:13 PM

Quote:

Originally Posted by Ribcracker

Which is the thrust bearing? Is it the normal looking bearing or is it the bearing disk that is sandwiched between the two grooved spacers?
Thanks,
Bud

The thrust bearing is the one where the bearing disk is sandwiched between the two grooved spacers.

Dusty1000 · 07-09-2010, 06:47 AM

You may also find the diameters of the holes in the middle of the grooved spacers are different. If they are, the ones with the smaller diameter hole likely go on the outside (furthest from the main shaft)

Dusty

Ribcracker · 07-10-2010, 07:54 PM

Dusty,
The diameters of the holes turned out to be identical.
There seemed to be a lot of vacant space in the feathering race so I wrapped plumber's form-a-gasket cord around the shaft and stuffed as much in there as I could. She's solid now! The dampening rings are on order but this seems to be working quite well.
After replacing the main, horizontal, and tail rotor shafts along with many other twisted/broken parts, my 450 is dead quiet and solid as a rock. To be honest, I never thought it would fly well again. How 'bout that!
Thanks for your ideas.
Peace,
Bud

Ribcracker · 07-20-2010, 08:21 PM

Guys,
I finally got some proper dampers installed and my head is solid as a rock, BUT...
I'm now experiencing tail-bobbing. After prolly a hunnert or so flights, my 450 has never done this.
Is it possible that the extra damping could cause this or do you think it's an unrelated issue? Any ideas on what might cause tail-bobbing?
Thanks for any insight y'all might have.
Bud

Ron_R · 07-21-2010, 02:40 PM

If your crash was as bad as you say (wicked), I'd disassemble the tail and make sure everything is in order. Many things can cause the tail to bobble. Check the tail components first including the boom. Then check the tail servo and the gyro and make sure they are functioning correctly.

Ron

Dusty1000 · 07-21-2010, 02:48 PM

Quote:

Originally Posted by Ribcracker

Is it possible that the extra damping could cause this

Yes, vertical bobbing can be caused by too tight a head. Low headspeed can also be a factor. So depending on your throttle curves, it might be worth upping them to see if the problem disappears.

Dusty

Ribcracker · 07-21-2010, 07:34 PM

Thank you, Dr. Ron and Dusty. Both of your ideas were helpful. I had crammed three dampers into each side of the horizontal shaft. Once I removed one from each side, the bobbing was a lot less pronounced. Then I did some forensics on the tail and discovered that my belt tension was unequal - one side of the belt spur was more taut than on the other side. So I re-centered it and that improved things even further.
Now there is no bobbing for several minutes but then a slight bobbing shows up briefly and then disappears for another couple of minutes.
I can live with it but my heli has never done this before so I'm gonna continue to chase it.
I'm rather new to helis so I'm still flying in "normal" mode with a throttle curve of 00-60-70-80-90. My hover is right at half throttle and that has worked well for me.
I'll need another fifty flights and a bit more courage before I hit that "idle-up" switch.
Peace,
Bud

07-08-2010, 05:03 PM	#1 (permalink)
Ribcracker Registered Users Join Date: Dec 2009	Feathering Shaft Slop Guys, I'm rebuilding my EXI 450 after a wicked crash. After replacing the feathering shaft I discovered a lot of slop in the head. With the grips fully tightened to the horizontal shaft, I can rock them like a see-saw. The grips also have a lot of lateral end-play. I can pull the grips outward by an eighth inch or so even though they are fully tightened down. What am I missing? Any ideas about possible remedy?

07-08-2010, 05:18 PM	#2 (permalink)
Bob O Member My HF Map location Join Date: Dec 2008	Wrong feathering spindle? __________________ ):>

07-08-2010, 08:05 PM	#4 (permalink)
Bob O Member My HF Map location Join Date: Dec 2008	Something must have been left out upon reassembly. Did the washers and thrust bearings get put back in and in the correct orientation? __________________ ):>

07-09-2010, 06:47 AM	#7 (permalink)
Dusty1000 Registered Users Join Date: Sep 2008	You may also find the diameters of the holes in the middle of the grooved spacers are different. If they are, the ones with the smaller diameter hole likely go on the outside (furthest from the main shaft) Dusty __________________ Blade 400, mSR, mCPX - Sonix SX450SE - Walkera 1#A, 4#3, 4#3A, 4#3B, 4G3

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07-08-2010, 06:08 PM	#3 (permalink)
Ribcracker Registered Users Thread Starter Join Date: Dec 2009	Thanks, Bob. But no, the spindle is the standard EXI part (31146) that I've been using since I've had the heli. The offending head is a cheap ($30) metal upgrade from Xheli which has been giving good service for a good while. The original plastic head is tight and solid so I could always put it back on but I'd like to figure out what went wrong with the metal head.

07-08-2010, 08:35 PM	#5 (permalink)
Ribcracker Registered Users Thread Starter Join Date: Dec 2009	You may be onto something. I'll take it back apart and do some forensics. Meanwhile, I did a search on "sloppy head" and discovered some other possible issues; the rubber dampers may be worn out. Some folks add a few extra to each side. Some folks shorten the feathering shaft to eliminate end-play. Also, I've heard that the thrust bearings could be damaged...or the seat where they sit. Which is the thrust bearing? Is it the normal looking bearing or is it the bearing disk that is sandwiched between the two grooved spacers? Thanks, Bud

07-10-2010, 07:54 PM	#8 (permalink)
Ribcracker Registered Users Thread Starter Join Date: Dec 2009	Dusty, The diameters of the holes turned out to be identical. There seemed to be a lot of vacant space in the feathering race so I wrapped plumber's form-a-gasket cord around the shaft and stuffed as much in there as I could. She's solid now! The dampening rings are on order but this seems to be working quite well. After replacing the main, horizontal, and tail rotor shafts along with many other twisted/broken parts, my 450 is dead quiet and solid as a rock. To be honest, I never thought it would fly well again. How 'bout that! Thanks for your ideas. Peace, Bud

07-20-2010, 08:21 PM	#9 (permalink)
Ribcracker Registered Users Thread Starter Join Date: Dec 2009	Guys, I finally got some proper dampers installed and my head is solid as a rock, BUT... I'm now experiencing tail-bobbing. After prolly a hunnert or so flights, my 450 has never done this. Is it possible that the extra damping could cause this or do you think it's an unrelated issue? Any ideas on what might cause tail-bobbing? Thanks for any insight y'all might have. Bud

07-21-2010, 02:40 PM	#10 (permalink)
Ron_R Registered Users Join Date: Jan 2010 Location: Cherry Hill, NJ	If your crash was as bad as you say (wicked), I'd disassemble the tail and make sure everything is in order. Many things can cause the tail to bobble. Check the tail components first including the boom. Then check the tail servo and the gyro and make sure they are functioning correctly. Ron

07-21-2010, 07:34 PM	#12 (permalink)
Ribcracker Registered Users Thread Starter Join Date: Dec 2009	Thank you, Dr. Ron and Dusty. Both of your ideas were helpful. I had crammed three dampers into each side of the horizontal shaft. Once I removed one from each side, the bobbing was a lot less pronounced. Then I did some forensics on the tail and discovered that my belt tension was unequal - one side of the belt spur was more taut than on the other side. So I re-centered it and that improved things even further. Now there is no bobbing for several minutes but then a slight bobbing shows up briefly and then disappears for another couple of minutes. I can live with it but my heli has never done this before so I'm gonna continue to chase it. I'm rather new to helis so I'm still flying in "normal" mode with a throttle curve of 00-60-70-80-90. My hover is right at half throttle and that has worked well for me. I'll need another fifty flights and a bit more courage before I hit that "idle-up" switch. Peace, Bud

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