Tail rotor hub issue

radu7 · 12-20-2012, 01:30 PM

Has anyone else had issues with the bearings in the tail blade grips (or just putting them on the hub by themselves not in the grips) fitting very tightly on the hub? Mine really have to be pushed on with quite a bit of pressure and they don't have the kind of smooth axial play like the blade grips do on the main rotor. I worked them back and forth quite a bit, 30 minutes or more, and it got a lot better, but the axial play is still a bit sticky and if the blade grips get close to the hub center on the conical portion they lock onto it with a vengeance and I have to really yank on the grips to get them back out to the ends. I guess as long as I yank them every time before I fly it shouldn't be a big issue, but it took a lot of goofing around for me to get them working like they are now and it's still not as smooth as I think they should be.

Seems like the tail rotor hub would work better if it had a shoulder at the hub rather than the conical shoulder like the main rotor hub. The drawing in the manual makes it look like it is supposed to have a flat surface there. Should I just work on it some with some emery paper or 600 grit until it is nice and smooth? Perhaps I got a bum tail rotor hub? I do notice that the tail hub is not polished to a mirror finish like the new main rotor hub I have now. The old, sloppy, rotor hub had this same dull finish so that makes me wonder.

Luvmyhelis · 12-20-2012, 01:33 PM

Did you lube up your tail grip bearings? Or just install them? They are kind of dry and gritty until you do this.

Plus, you want your grips tight on the hub. Less slop here is critical to blade tracking.

itsmillertime0 · 12-20-2012, 01:36 PM

With the exception of the main blade grip thrust bearings, aren't all of the bearings in this kit pre-lubed? I was under the impression that they were and oiling wasn't necessary and in fact does more harm than good by washing out the factory grease making frequent oilings a necessity..

Jason O'Connell · 12-20-2012, 01:38 PM

The grips will be pulled out to their running positions by centrifugal force unless they are really REALLY tight. Make sure to add some grease to the thrust bearings mine were dry.

Jason

radu7 · 12-20-2012, 01:46 PM

Thanks for the quick reply LMH! I did clean and lightly lube the insides of the bearings where they slide onto the hub, but it doesn't do a whole lot for the issue. One important thing I forgot to mention is that one side of the hub is considerably tighter than the other (regardless of which set of bearings I put on it) as if that side was machined just micrometers less than the other. My concern is that even after working them back and forth they are still very sticky. To the point that if they move back toward the center of the hub at all they stick such that I don't think the centrifugal force of the rotor spinning would even get the grips out to the ends like it should. It sticks to the point that it will start pulling the bearing out of the back of the blade grip when I try and pull it back off. And you don't have to push the grips very far onto the hub for them to grab like that either. I was thinking it should be a lot smoother than that.

radu7 · 12-20-2012, 01:51 PM

Quote:

Originally Posted by BarnStormer

The grips will be pulled out to their running positions by centrifugal force unless they are really REALLY tight. Make sure to add some grease to the thrust bearings mine were dry.

Jason

Thanks Barnstormer. They really are 'that' tight! I was surpised to see that the thrust bearings in my main blade grips had grease and plenty of it. Well, I say that, but I did not take them apart. I looked inside with a flashlight right before I was going to disassemble them and there was gobs of clear synthetic grease inside. I had to clean some of it out with a tooth pick it was so plentiful. I do want to take them apart to check the orientation of the thrust bearings though as I like the side that is packed with grease to face the mainshaft. Are the bearings fairly easy to get out of the grips? I don't want to jack them up or scratch anything fighting with them.

Thanks again,
Anthony

Jason O'Connell · 12-20-2012, 02:10 PM

Quote:

Originally Posted by radu7

Thanks Barnstormer. They really are 'that' tight! I was surpised to see that the thrust bearings in my main blade grips had grease and plenty of it. Well, I say that, but I did not take them apart. I looked inside with a flashlight right before I was going to disassemble them and there was gobs of clear synthetic grease inside. I had to clean some of it out with a tooth pick is was so plentiful. I do want to take them apart to check the orientation of the thrust bearings though as I like the side that is packed with grease to face the mainshaft. Are the bearings fairly easy to get out of the grips? I don't want to jack them up or scratch anything fighting with them.

Thanks again,
Anthony

The bearings can be a little tricky to remove but if you take your time it is not too bad. I ended up leaving the bottom race for the thrust bearing in the grip as there was no NEED to remove it and it was in there good lol. If the bearings are really that tight on one side you could always use a peice of verry fine sandpaper or some Scotch-Brite on the shaft but, be VERRY careful and slow if you choose to do it. My guess is that a few turns with a Scotch-Brite pad would do the trick.

Jason

cbmd · 12-20-2012, 06:33 PM

Quote:

Originally Posted by radu7

TAre the bearings fairly easy to get out of the grips?

My main blade grips were under-greased. They were easy to remove after putting them into the oven for 5-8min, pre-heated to 150°C. As I had already assembled them, it was more effort to take off the carbon parts, again. I used a wooden barbecue stick to tease the bearings out from the main shaft side (no scratches). Outer bearing, outer thrust bearing race and the ball cage came out, I left the inner thrust bearing race in place. Reassembling was quite easy, too. No re-heating required.

radu7 · 12-21-2012, 07:50 AM

Thanks for the replies and the tips on getting the bearings out of the blade grips! All very helpful information. As for the tail rotor hub I've got it to a point where it should work OK once I get the build finished. I took some 600 grit sandpaper and wrapped it around each spindle of the hub and lightly turned it a few times which helped a lot. I noticed that after putting the bearings onto the hub and pulling them off there were scrape marks (individual lines, not broad scrapes) on the spindle from the bearings. Seems the outer edges of the bearings were not so smooth either so I buffed those a bit too with the same sandpaper. It's smooth enough now (and certainly no slop) that they should spin out to the ends just fine when I try to fly it. Other than a little work I may do tonight my build will be on hold until the 27th. I'm only to the point of assembling the belt tensioner (step 23) as I only have a couple hours here and there that I can devote to the build right now. Hopefully I will have it wrapped-up by the New Year. Then on to a new build until some better weather arrives...

TBur · 12-22-2012, 04:34 PM

Deleted

12-20-2012, 01:30 PM	#1
radu7 Registered Users Join Date: Dec 2011 Location: Southeastern United States	Tail rotor hub issue Has anyone else had issues with the bearings in the tail blade grips (or just putting them on the hub by themselves not in the grips) fitting very tightly on the hub? Mine really have to be pushed on with quite a bit of pressure and they don't have the kind of smooth axial play like the blade grips do on the main rotor. I worked them back and forth quite a bit, 30 minutes or more, and it got a lot better, but the axial play is still a bit sticky and if the blade grips get close to the hub center on the conical portion they lock onto it with a vengeance and I have to really yank on the grips to get them back out to the ends. I guess as long as I yank them every time before I fly it shouldn't be a big issue, but it took a lot of goofing around for me to get them working like they are now and it's still not as smooth as I think they should be. Seems like the tail rotor hub would work better if it had a shoulder at the hub rather than the conical shoulder like the main rotor hub. The drawing in the manual makes it look like it is supposed to have a flat surface there. Should I just work on it some with some emery paper or 600 grit until it is nice and smooth? Perhaps I got a bum tail rotor hub? I do notice that the tail hub is not polished to a mirror finish like the new main rotor hub I have now. The old, sloppy, rotor hub had this same dull finish so that makes me wonder.

12-20-2012, 01:36 PM	#3
itsmillertime0 Registered Users Join Date: Jan 2012 Location: Southaven	With the exception of the main blade grip thrust bearings, aren't all of the bearings in this kit pre-lubed? I was under the impression that they were and oiling wasn't necessary and in fact does more harm than good by washing out the factory grease making frequent oilings a necessity.. __________________ Team Newb Walkera Mini cp - hp06v2, hp02t, custom fet esc's, 550's Blade 130X - hp08s, lots of bling; Blade 130X - ta955, xp12a Compass Warp 360 - CC ice lite 50, MKS DS92A+, iKon

12-20-2012, 01:38 PM	#4
Jason O'Connell Formerly BarnStormer Join Date: Aug 2008 Location: Mequon, WI	The grips will be pulled out to their running positions by centrifugal force unless they are really REALLY tight. Make sure to add some grease to the thrust bearings mine were dry. Jason __________________ "You can still call me Barn To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. " Team Compass USA ProStarHobby.com Scorpion Power Systems

12-22-2012, 04:34 PM	#10
TBur Registered Users Join Date: Feb 2012 Location: Seattle, WA	Deleted __________________ Compass 7HV SK720 Compass 6HV SK720 Compass 500 SK720 Blade MCPx V2

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12-20-2012, 01:33 PM	#2
Luvmyhelis Join Date: Jul 2010 Location: spokane,washington	Did you lube up your tail grip bearings? Or just install them? They are kind of dry and gritty until you do this. Plus, you *want* your grips tight on the hub. Less slop here is critical to blade tracking.

12-20-2012, 01:46 PM	#5
radu7 Registered Users Thread Starter Join Date: Dec 2011 Location: Southeastern United States	Thanks for the quick reply LMH! I did clean and lightly lube the insides of the bearings where they slide onto the hub, but it doesn't do a whole lot for the issue. One important thing I forgot to mention is that one side of the hub is considerably tighter than the other (regardless of which set of bearings I put on it) as if that side was machined just micrometers less than the other. My concern is that even after working them back and forth they are still very sticky. To the point that if they move back toward the center of the hub at all they stick such that I don't think the centrifugal force of the rotor spinning would even get the grips out to the ends like it should. It sticks to the point that it will start pulling the bearing out of the back of the blade grip when I try and pull it back off. And you don't have to push the grips very far onto the hub for them to grab like that either. I was thinking it should be a lot smoother than that.

12-21-2012, 07:50 AM	#9
radu7 Registered Users Thread Starter Join Date: Dec 2011 Location: Southeastern United States	Thanks for the replies and the tips on getting the bearings out of the blade grips! All very helpful information. As for the tail rotor hub I've got it to a point where it should work OK once I get the build finished. I took some 600 grit sandpaper and wrapped it around each spindle of the hub and lightly turned it a few times which helped a lot. I noticed that after putting the bearings onto the hub and pulling them off there were scrape marks (individual lines, not broad scrapes) on the spindle from the bearings. Seems the outer edges of the bearings were not so smooth either so I buffed those a bit too with the same sandpaper. It's smooth enough now (and certainly no slop) that they should spin out to the ends just fine when I try to fly it. Other than a little work I may do tonight my build will be on hold until the 27th. I'm only to the point of assembling the belt tensioner (step 23) as I only have a couple hours here and there that I can devote to the build right now. Hopefully I will have it wrapped-up by the New Year. Then on to a new build until some better weather arrives...