White bushings in 2010/2011 head

[abanihani]

Originally Posted by jointer

The first guide here, from someone who done it, was not to put the grub screw in and use black/black.
Working well for me, except sometimes resonation during first spoolup.

When i got my white pushes, Jan lift me a note to use an inside red ring, outside black ring and fly several flights to let the mechanics adjust first, after that he said move to the black and black for maximal rigidity.

[mkovalcson]

Originally Posted by marcosp

You are missing that you'll have an egg boiler too!!!

On the custom winding sub forum I read the Xera is cooler because it has air channels that help in refrigeration, so the better efficiency is a myth. However, it pulls the same power and comes down cooler. I like it a lot.

So you are not a fan of the Scorpions for ventilation reasons?

I guess this is where those Heat sink motor mounts and NACA ducts fit in.

[marcosp]

Not really, nothing against Scorps. The 4525 is just one specially hot motor. Cool running is more a merit of the Xera than a demerit of the Scorps. Pyros have the best ventilation for that matter.

The variables that affect efficiency, heat and power are so complex that it's narrow minded to say that a cooler motor is more efficient on that measure alone, that was part of my point talking against the Xera actually, saying its cool running has nothing to do with it being more efficient. Since they managed to have less winding to put air channels and still puts out the same power I really like it a lot.

[Danny_Swe]

I have cooling issues on mine, the ESC get too hot, and the motor feels uncomfortably hot. Will try make a hole in the canopy, have a Duct but it's not enough.

(YGE 120HV, 4035-560)

[mkovalcson]

So far it appears I have no cooling issues at all with the monster heat sink on my Jive 120HV or with my Pyro.

[marcosp]

I was at work today thinking about my TDR, as usual, and it occurred to me that I might have bent the spindle in flight. It's brand new, but I do fly aggressively at times. Will check and come back with the intel for the group's communal knowledge.

[zmooth]

I was thinking mine might be bent too since it started to show a slight wobble in hover, turned out it was fine as were the thrust bearings etc. I tried black dampers and it was solid in the air but really wanted to sort this out on white ones. Replaced any loose links and re-aligned everything, swash was fine but I noticed a slight tracking had developed which was most probably the cause since its rock stable now.
Maybe black dampers are more forgiving to tracking/vibrations ?
I must admit I did enjoy them back on, heli becomes very pleasant and relaxed, maybe should keep them on on the backup model ? Hmmm

[swalko]

Yes, black dampers may eliminate small tracking problems. This is mentioned in manual too.

[jointer]

Yes from me too; but if you are experiencing "shake" in hover with white inserts, try to adjust RPM slightly and run mode 11 in Jive (governor with RPM hold).
Also, if the heli is new, you may have bigger problems with this, it is usually possible to use RPM where the heli was shaking again after you done 20-30 flights.
The black inserts are more forgiving, relaxing, where white ones give more precision and agility, they are more sharp.

[helicraze]

I never bend harndened spindle, only the original 09 one.

[marcosp]

I changed white bushings two weeks ago, the originals had developed play after some 80 flights. Put in new double black dampers and have new spindle and shaft. I do have an ever so tiny play in the main shaft. Tiny up and down, almost un noticeable sideways and front to back. Main bearings are new too, so the lateral play me be caused by the need to re shim.

What puzzles me is the heli has very heavy shakes on spool up which converts to a slight vibration perceivable on the canopy at 1400 rpm, definitely main rotor rpm frequency, and it is still there at 1600 and 1850. All the range has this vibration. I swapped blades and it is exactly the same. That is why I didn't try to do slight changes in rpm, it seems to be all over the rpm range.

Can the main hub bearings that support the spindle ball (that withstood 2 crashes) cause this? I never sensed roughness but who knows.

I'll be working on the heli tonight and flying tomorrow. I'll re shim and check the spindle. I'll let you know how it goes.

[marcosp]

The vibration was already there with the previous white bushings and red/black dampers.

[marcosp]

Some work done. I removed the head and checked the spindle. I seems straight though at some positions on the radial bearings on each blade holder it seems to have an uneven spot. The radial bearings, though quite new, are not in the best shape. I bet they would really improve with re greasing but I don't have the appropriate tool for that. The bearings on the main hub that hold the spindle are rough too. I don't think this matters much since the movement is minimal. If they are seating unevenly they might be throwing the spindle out of whack, so if all the work doesn't pay off I am aiming at these next.
I re shimmed the top of the main shaft and it is tight and nice again. Even the sound of the crown gear changed, don't ask why, I really don't know, but the whole drive system is back to its full glory.
I discovered my swash had a bent arm from the last crash, the one that was attached to the elevator link. I can't believe I did not see this! I was having some weird elevator behavior on some piro maneuvers, a sudden down elevator correction by the Vbar. I attributed it to the low frequency vibration I am chasing affecting the Vbar. The log did not help diagnose since every blade fart is a high vibration anyway. I am confident it was the bent swash.
When I put the blade holders back I measured space of each one with the hub. The difference was considerable (0,1mm) enough to make me place them at the equidistance measuring carefully and tighten the spindle set screw. I still don't understand how that tiny screw holds the spindle from moving against the major forces placed by even the tiniest unbalance between blades. I bet if Jan put it there it must work ok!

So, all in all, lot of maintenance and corrections so I am hoping my first spool up tomorrow shows a marked difference with last weekend. I'll be back with news tomorrow.

[Stolla]

I've bent spindles in flight, only way to see is to roll on glass and listen, you will hear a click click noise, no problem you fly logos,600 drop in replacement and doesn't bend!

[ZuvieleTeile]

@ Marcos
After I re-shimmed my spindle a while ago I did some flights without tightening the grub screw (unintentionally) and she flew perfectly. Most of the helis don't have a means of fixing the spindle anyway.
@ Stolla
I find it hard sometimes to discover a tiny bend in the spindle on a glass surface.
I remove one blade, loosen the grub screw and turn the spindle with an extended Allen key.
The remaining blade acts as a huge lever arm and shows the tiniest bend of the spindle as movement up and down.
If I have a really picky day, I remove the other blade and do the thing vice versa, because it could be that only the other side of the spindle is bent.

[marcosp]

I know most helis don't use the grub screw but since this one does I could only think "will this tiny thing withstand the force?". I tried it without the grub and it flies fine. I check the spindle rotating it in place too. Leaving a blade on is an excellent tip!!!

All the work didn't pay off. Shake was there exactly as before, and it's effect on the vbar worsened in flight. Sudden left aileron (a clear sign of sensor blur, always to the left on many helis, don't know why) and some down elevator on piro maneuvers. Fast piro to the right throws the heli out of wack severely, as in 45 degree back and right, I checked the log and the readings is: at 1500 raised vibes most of the time, high at moments, at 1700 raised all the time, high at many times, extremes at some times, at 1850 high all the time, extreme many times.

I checked the TT for length (warning in the manual) and it was ok. I took the chance to space the 3 bearings unevenly, just in case. I set the crown mesh a little looser. Nothing, still shaking.

After a drift of inspiration I lowered the gains 5 points on all banks. I hadn't done it after putting double black dampers. The shake at 1500 disappeared, at 1700 and 1850 it was almost unnoticeable. The funny vbar was more sporadic but still there. The last flight of the day showed a strange behavior on the vbar. On spool up a severe shake, I mean really really severe, stopped it and after that swash is wacky and moves very uneven up and down. Reset, check everything is back to normal and flew a 100% uneventful flight, no shake, no strange vbar stuff.

I think it's two different problems. The shake was too much gain (was at 100 for 1500, 90 for 1850). It never ever happened with vbar to have too high a gain and not notice it in flight but have it resonating in the hover. I usually detect too much gain in flight, I know which maneuvers uncover it. The wacky vbar could be a sensor starting to act funny. We'll see, I am flying carefully now, not soft, just a bit higher and finger on the Hold switch at all times, and very conscious to even the slightest misbehavior.

Oh, I lost the plastic cap on the hub that last flight hahahaha, inverted so no hit on the blades, and it got lost in some bushes outside the field. Baaaah, couldn't care less...

[swalko]

I tried to solve shaking problem for a long period. My TDR was flyable and shaking was noticeable in hover, more noticeable on low rpms, less on higher but it still was there. Gain increase or decrease have effect on this but i was not able to completely eliminate shaking with low gain. In a combination with resonance from 2009 head shaking was very very violent and my TDR seemed as it want to kill himself ... At the end this was caused by worned Pyro bearings. Now i we done complete TDR maintenance, only one old bearing and one old shaft stayed in TDR. With cyclic throw on 89 i am able to raise gains to 126 (1400 and 1770 rpms) without any negative effects and TDR is pretty locked, but i do not like so high gain because it feels too robotic.

BTW i tried more fbl units and VStabi is clearly the best in a case of handling high TDR vibrations or noises from worned bearings.