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Old 12-12-2012, 02:25 AM   #1
Ty89m
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Default Tail Shaft

Well, another question for you all. Got the tail case/shaft installed, curious if I should be able to spin the tail shaft/gear (without belt on the gear) with my fingers and have it spin freely on its own after letting go? It's fairly smooth, but certainly can't just spin it with my fingers and have it keep spinning. Loosened the case bolts a bit, and it really doesn't make much of a difference. I know how important a smooth tail is, so am a bit concerned. Thanks
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Old 12-12-2012, 07:19 AM   #2
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It should do at least a few revolutions after u give it a flick, check your bearings, also make sure everything is in the right order and seated properly.
This is not the most important thing on the tail.
The pitch slider action is the thing you need make smooth as possible
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Old 12-12-2012, 08:28 AM   #3
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Spin it by itself? With the Spindle on? Grips? Blades? I mean, with blades, it will spin quite a bit. It should turn like the inside of the bearings it sits in otherwise. New bearings are klind of sticky.
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Old 12-12-2012, 11:44 AM   #4
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Nothing else installed bit the shaft/gear and guide pulley. Def. can't give it a twist and have it make a few turns on its own. Really not sure why it's not easier to turn, main shaft was much better... Will tear it down and check bearings. Can those nylon nuts take a few cycles of taking on/off before they no longer hold as well?
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Old 12-12-2012, 12:01 PM   #5
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Is the belt on ? It wont spin but a turn with blades on the tail, if that, with the belt on. Yes the lock nuts will cycle several times. if you cant spin the nut all the way past the nylock with just your fingers (no tool) without a lot of force or discomfort then they are still good to go. Do not over tourqe the tail case. Tighten only till the halves touch each other and no more!
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Old 12-12-2012, 12:55 PM   #6
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I know when I took mine apart a couple of days ago to put the belt back on, The shaft had become all nice and polished. It was spinning inside the bearins so your not going to get a free wheeling shaft like that. Its all kind of mickey mouse.
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Old 12-12-2012, 03:03 PM   #7
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Belt is installed, but moved it off the gear/shaft to see how smooth the shaft spins. Not near as free spinning as I'd have thought it would be. Might take it apart and check the bearings. Wonder if the shaft is not at perfect 90 to the gear/tail case and causing a bit of binding...
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Old 12-12-2012, 03:17 PM   #8
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New bearings never feel super smooth as there is still some excess grease in them. If you run your finger over the shaft with some downward perssure it should feel like it is "on bearings".

On my Gaui i could rock the tailshaft a little in its bearings. This caused a lot of vibrations above a certain rpm. Fixed it with a tiny bit of green loctite. essentially glueing the bearing inner race to the shaft. Makes replacing the bearing a hassle but my tail is super smooth now. Also if i push/pull on the tailshaft i noticed the pulley was not properly fixed between the bearings. Added a washer just thick enough to give a slight lateral force outwards against the bearings without losing any rotating smoothness. This bearing compression reduces any play in the bearing races, making the tailshaft run even more true..

I am not saying it is a needed mod on the miniP. I don't have mine yet but the plastic assembly looks similar.
Keeping the tailbox halves square is obviously essential.
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Old 12-12-2012, 03:31 PM   #9
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+1 on the loc tite. But on Mini P, when it throws a belt, sometimes you need to rip the tail apart. Could be problematic. Polishing the tailshaft with rouge makes it go together better with that CNC tail pulley and a I had to use a little 600 grit in the shaft ends to get it to slip over. Very tight tolerances there.

http://www.nmbtc.com/bearings/engineering/fitting.html

LocTite 609 is the stuff to use if you want it locked down.
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Old 12-12-2012, 05:17 PM   #10
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After it has been run up a few times it will get easier to rotate.
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Old 12-12-2012, 05:20 PM   #11
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Yes, used one of my Cape Cod polishing cloths on the tail shaft, everything slid on smoothly. Does anyone's tail spin super easily when the belt is not on the gear? It just seems to me that it should be able to keep spinning after giving it a good twist with the fingers, it's not near as easy to spin as my main shaft was. If its normal ill leave it alone. Will investigate tonight. Thanks for all the input guys!
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Old 12-12-2012, 05:31 PM   #12
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actually, this is what i do with the shim.
http://www.nmbtc.com/bearings/engineering/preload.html
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Old 12-12-2012, 05:57 PM   #13
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Quote:
Originally Posted by Ty89m View Post
Yes, used one of my Cape Cod polishing cloths on the tail shaft, everything slid on smoothly. Does anyone's tail spin super easily when the belt is not on the gear? It just seems to me that it should be able to keep spinning after giving it a good twist with the fingers, it's not near as easy to spin as my main shaft was. If its normal ill leave it alone. Will investigate tonight. Thanks for all the input guys!
Just as long as you are confident you have not over tourqed the tail case it is normal. It will run in and get easier after the grease in the bearings breaks down a bit. You can help it along with some triflow oil on the bearings. It will never rotate as "freely' as the main shaft as it does not have the weight or large surface area of the main gear to act as centrigual force. Remember those table top spinners as a kid. The larger diameter ones spin for ever while the small diameter ones peter out quickly/ Put it together. put some triflow on the bearings and run it up/ All 3 minis I have built had a lot less friction on the tail shaft and bearings after being run in a bit.
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Old 12-15-2012, 12:53 AM   #14
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Well just tightening it down until the two halves touch, it still feels pretty "notchy" though I notice if I loosen the bolt that goes through the tail pulley, it frees up a bit, but then the pulley has a lot of play left to right, not sure if that'll cause extra vibrations or not. I also noticed the bushing that came with the metal tail gear was much too large in diameter to fit in the tail pulley bearings, but the one that comes with the kit fit, I've read of others having this issue, but not sure it'll make any difference. I've tried two sets of tail case plastic pieces and two sets of bearings, both with same results. Every set of plastic tail casings seem to be bowed out on each end, which I'm sure doesn't help. As long as the tail pulley can have a bit of lateral movement side to side, I should be ok.
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Old 12-15-2012, 11:22 AM   #15
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Not sure what you mean by a lot of play. I have about 1mm of play or less side to side in the tail guide pulley. The belt keeps the pulley in the middle of the shaft when it is on. The tail pulley has no play side to side. I know when I put the tail pulley on the first time, the pin almost snapped in to place. Perhaps there was something in it interfering. The bushing then slipped inside that side of the pulley about 1/2 way. I dunno, seems to work fine back there no rubbing or anything.
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