OWB Center Hub tollerance issue.

[SFACV]

So I had the same issues as a few others here with the ticking on spool down, still haven't got a full flight on my heli because it still has vibe issues. I think I may have figured out some of my problems though. The one way bearing center hub does not fit tight on the main shaft, in fact mine if you take it and put it on a mainshaft out of the heli and check side movement there is quite a lot. I had ticking on spool down (only with tension on the belt) and after a couple hours messing around and looking for the source I found the tolerance issue. To fix mine I took the OWB hub and cleaned the ID really well with alcohol and then hit it with spraypaint inside, took 2 wet coats to build it up enough for a tight fit to the mainshaft. Haven't spooled it up yet but spinning buy hand on the bench, which was also ticking before, now is smooth and silent. I could feel it in the frames before when spinning by hand every time it ticked so it was definitely enough to cause issues. I am not sure if this is just a slight inconsistency and there is a few hubs like this or maybe on some helis it doesn't seem to be a problem being loose??? What initially got me looking at this part is that the mainshaft had significant wear (black coating gone) where the hub was located, since there is no movement between these parts there shouldn't even be a mark. I would maybe have 15 minutes of runtime total on this machine, and only about 5 on the new mainshaft and it is worn too. Only thing that would cause this is movement.

I will report back a little later once I get an actual flight. Hoping this fixes the rest of the vibe issue I have too.

[SFACV]

Ticking problem solved but still got a case of the shakes

[heathy]

What headspeed are you at with the shakes? Lower than 1900 by any chance?? Did you grease your dampers and feather shaft?

If shakes are at 1900 or lower then its just your dampers bedding in

[dannylightning]

could your FBL gain be set to high, that will make the helicopter bobble around in flight.

[SFACV]

Originally Posted by heathy

What headspeed are you at with the shakes? Lower than 1900 by any chance?? Did you grease your dampers and feather shaft?

If shakes are at 1900 or lower then its just your dampers bedding in

Yes I am around 1700, tried to bump it up but much more than that it makes terrible sounds and shakes bad. May be V-Bar, I haven't tried higher since adding the Gyro Plate which helped a lot.

[SFACV]

Originally Posted by dannylightning

could your FBL gain be set to high, that will make the helicopter bobble around in flight.

Could be??? But the vibes were messing with the V-Bar, it wasn't hunting.

I think it has something to do with the head - Grips, maybe slightly out on blade tracking yet???

[heathy]

The damper low HS thing always goes away at higher HS so as you say probably something else then, have you checked thrust bearing assembly? And might be worth spinning up on the bench without blades and watching the head to look for out of thack grips etc

[SFACV]

Originally Posted by heathy

The damper low HS thing always goes away at higher HS so as you say probably something else then, have you checked thrust bearing assembly? And might be worth spinning up on the bench without blades and watching the head to look for out of thack grips etc

Spinning on the bench without mains is very clean since I put on the upgraded tail yesterday. Main grips appear to track fine. I added the gyro plate and it is much better but haven't tried 12s to get 2000 yet. Might be ok now that the V-Bar is behaving. Hopefully test this tomorrow. Might just be dampers need time on them at this point. I have had grips apart (along with everything else on this Heli) all bearings are good, replaced all mainshaft bearings just cause but made no difference.

For dampers to wear in does it require hard 3D or would basic sport flying do the job?

[heathy]

I guess hard 3d would bed them in faster but as most of us can't do hard 3d sport flying will be fine,.My second 7 which is getting its 3rd weekend of flying tomorrow has this and i'm just doing basic tic tocs, rolls flips and general hooning about, it'll be gone soon enough and smooth at lower HS like my older one. for now its at 2100

[SFACV]

We have a foot of snow and sub zero temps. Will that have any effect on break in?

[jmackey]

I'm doing maintenance on my 7HV's this weekend and found something similar. There was a lot of wear on the mainshaft where it mates to the autorotation sleeve (09-7103). There was significant play between this sleeve and the main pulley hub (09-7070) too, even thought the two grub screws and the bolt holding it to the mainshaft were all tight.

Like SFACV observed, the main pulley (09-7026) was rocking back and forth during operation. You can hear this clicking on spool down and spinning the rotor by hand. There are uneven wear patterns on the mainshaft that suggest a vibration related to this rocking were it is supported by the mainshaft bearing blocks and also the swash plate.


https://www.helifreak.com/album.php?...ictureid=80036


I have a new mainshaft, autorotation sleeve and main pulley hub on order now to make it right. Hopefully the new parts will have a tighter fit. If not, I'll try the paint trick to tighten it up.

[snaaakeey]

I have recently changed the dampers in mine after a crash and the shakes are back at 1800 rpm. 2100 is perfect. I hope healthy is right about the bed in process . I had this exact vibration when built her last year bandit eased with time. Cross fingers as the head is perfectly balanced! Damper shakes sounds right but others have suggested their shakes have never gone away! Cross fingers!

Sent from my GT-P3110 using Tapatalk 2

[Ah Clem]

Make sure the dampers are coated, inside and out, with silicone grease, or something similar that will not degrade the damper material.

To Danny's point above, too high of a gain on the FBL unit (whether it be V-Bar or BeastX) can result in a very high speed shudder that is frequently mistaken for vibration. Increasing the RPM and/or decreasing the gain can correct this issue. I have run into this on the Atom, the Fusion, and the Trex 450 Pro, when going to harder dampers.

After a few flights, the dampers usually break in, so that the RPM can be lowered a bit and/or the gain can be increased a bit.

[Rob43]

Those green dampers are sooo stiff. I wonder if I will know when it's time to change them? Second completed season on mine, maybe 200 flights or so. Only replaced parts have been the V2 tail upgrade, and main gears.

[GnarfleTGarthok]

Has anyone else been following the Goblin HPS head? Sort of a step backwards but its suppose to let you run soft dampeners and much lower head speeds for those who want to.

[flyer2160]

i think the sab hps head is a good idea, good to see sab taking note of its customers and making a head to suit people who want to run lower head speed.

maybe compass should take note and help out its customers with the wobble, there is distinct silence from compass on this subject.

[heathy]

Nothing wrong with the compass head [ame]http://www.youtube.com/watch?v=uG6uTANQMDM&list=FLH10WqUOH4t4Ca0Qy4NUB6Q& index=4&feature=plcp[/ame]

Also, i'm 100% sure the side to side wobble is caused by the dampers when new, they take a good 20 or so flights for it to disappear. My 2nd 7hv had real bad side to side wobbles @ 1800, 2100 and gone! Now @ 24 flights with it and its now a tiny wobble [ i always check @ 1800 for a while before flicking to 2100 ]

[Ah Clem]

"Has anyone else been following the Goblin HPS head? Sort of a step backwards but its suppose to let you run soft dampeners and much lower head speeds for those who want to."

The Compass heads (Atom 500, 6HV, 7HV, and both sizes of TracX heads) are made so that you can run softer dampers. Softer dampers allow slower head speeds without "nodding".

Unlike some of the heads that appear to be similar at a glance, the Compass heads allow spindle flapping without any additional stress on the swashplate, ball links, bolts that hold the Drive Tube yokes to the head, etc. The Drive Tubes are flexible for a reason (Delrin as opposed to solid aluminum).

The Compass main shafts do not have to be unusually low in order to reduce the amount of linear travel at the swashplate, so the chances of a boom strike are much lower, at lower head speeds, as well.

I have been running the Compass heads with both the Lime Green KBDD Dampers, and the less firm Royal Blue Dampers for quite a while now.

I believe Dave K. has run his 7HV at quite low head speeds (down in the 1500 range-he will correct me if I am wrong here) with no problems.

[flyer2160]

my compass 7hv was great at 1600 to 1750 head speed it only had the wobble at 1800 to 1900. tried royal blue dampers and only slight improvement. put about 100 flights on them.

i have made some delrin dampers and no wobbles at any speed, sab have used a similar material in the hps head.

would like to try the sab hps head on the compass just to compare

[snaaakeey]

Interesting! Did you copy the standard damper dimensions ?

Sent from my GT-P3110 using Tapatalk 2