Front Tail gear set chewed out

[manphil]

Ok guys .....what went wrong.

I am general sport flyer ,,,loops, rolls, flips, some inverted ..aggressive 3D is way above my skill level.

I have been ramping up the ESC gov gain ...Talon 120 HV ...while trying to understand collective control and head speed bogging.

On my last flight I did a couple of demonstration tests of the rescue mode in the Spirit FBL ...both from an inverted and non inverted attitude.
The 'rescue' mode is set to revert back to normal level flight , right side up.

It does this in a way, far more aggressively than I can do in normal flight and once it attains level attitude it is set to climb at about 50% pitch up.

After that flight I discovered this ...just before the next flight.




So:
1. Is my ESC Gov gain too high.?
2. Something wrong with the meshing of the gears?
3.It ate some foreign object...unlikely me thinks.?


suggestions/comments???

Phil.

[SamCSx]

Ouch. This is a bit worrisome to me since I have a 550X and it has the exact same tail drivetrain. Maybe the Spirit's recover is just so violent that it partially stripped the tail gears. At any rate, it's lucky you noticed that before you flew it again. It's really buried down in the there and not all that easily visible unless you're specifically checking that area.

[manphil]

Hi SamCSx,

Yeah, I noticed the tail not spinning up on the next flight spool up and shut it down.

There has not been any scuttle-but in the forums about the torque tube gears, so I have no reason to think there is a design or parts issue here.

I am leaning to the view that it was something in my construction, as when I replaced the parts I noticed that the boom clamps did not match up to the boom supports ..so the boom was not in the same position as before ...only few millimeters ...but enough.

So, I am guessing the gear meshing might have been a little bit out ..and together with the aggressive rescue manoeuvrers ......

This is only my second build of a kit Heli ....ever!!
...(not counting rebuilds of 450x and 500x ..lol) .....so I live, and learn

The 550X was my first ...and she is flying great.

Phil.

[Uriah]

When you install your tail boom or tail case, push it in as far as it'll go and then back it out 3mm. This will allow your torque tube and gears to "float" so they don't melt from excessive heat and friction. You can either back the boom itself out 3mm or back the tail case out 3mm (whichever you prefer). This doesn't mean the gears will have a huge backlash, it just means that the torque tube will not be cramming the gears against each other during hard piro reversals when the torque tube flexes, such as what you'd expect during a hard FBL bailout when the tail has to correct for the sudden torque of the main rotor.

[Smoggie]

It's the governor gain that does it. If the gain is too high it causes a oscillation in the drive train similar to the tail shake you get if you have tail gain too high. You can sometimes hear this as a 'chirping' sound under heavy collective. The oscillation rips out the gears.

Here are the TT gears from my Trex 600 after increasing Castle ESC gov gain:


The gain on Castle ESC's is pretty aggressive, best keep it on 'low'.

I'm not familiar with the Blade TT design but if it's anything like the Trex (an I'm pretty sure it is) the boom position does not affect the mesh of the bevel gears. The gears are supported by bearings and the bearings themselves hold the bevel gears in tight mesh. The TT is designed to have a bit of end float, it's not intended to hold the bevel gears into mesh.

If you do want to adjust the mesh of the gears you have to use shim washers placed between the front bearing and the shoulder on the front TT bevel gear.... But I'm 99% sure that it will just be the gain at fault.

[manphil]

Thanks for the Replies Uriah and Grumpy.

Grumpy, I am thinking that, I agree with your comments
..as in my O.P. ...number 1 on the list was ESC gov.

But look, thanks for the confirmation! ...at least I have still got my head going in the right direction ...soooo much to learn in this endeavour!

I am deeply indebted to all of the helpful folk that post in Helifreaks.

A bit of a wet and miserable day here in my part of Australia ...a flight is not likely. ...keep flying guys!!

cheers,
Phil.

[SamCSx]

Originally Posted by Grumpy_Old_Man

I'm not familiar with the Blade TT design but if it's anything like the Trex (an I'm pretty sure it is) the boom position does not affect the mesh of the bevel gears.

You're right on the design. The TT bevel gears are captured in the plastic boom block. But, there is a tiny bit of pre-set gear lash. If you ram the boom into the back of the block and the tail gear box into the back of the boom, you'll force the TT forward enough to jam up the gears removing any pre-set lash and that's a problem. Vibes at a minimum and melted/stripped gears at worst. So, yes, fully seat everything and back the boom out a couple of millimeters to allow a bit of play or "float".

[manphil]

Yeah, Sam and Grumpy,

You guys are spot on with the set up of the gear set.

The torque tube gears on each end have to be pressed in to the bearings. When 'seated' all the way home, the bevel gear sits about 1 mm proud of the casing. See picture in O.P. ......I believe this is correct.

This positon should automatically set the correct gear meshing / play / lash, when the rest of the gear housing is screwed together.

In the 4 kits I have seen, there is no need to 'shim' the gear set. ( well not in my view)

If you did not 'seat' the bevel gear in the bearings, then you would have a very tight mesh.

I am reasonably sure that this is all Ok on my helis.

But it is good to mention, as some folk may get tripped up.
...and also to have a little bit of float in the torque tube.

Cheers,
Phil.

[Uriah]

Originally Posted by SamCSx

You're right on the design. The TT bevel gears are captured in the plastic boom block. But, there is a tiny bit of pre-set gear lash. If you ram the boom into the back of the block and the tail gear box into the back of the boom, you'll force the TT forward enough to jam up the gears removing any pre-set lash and that's a problem. Vibes at a minimum and melted/stripped gears at worst. So, yes, fully seat everything and back the boom out a couple of millimeters to allow a bit of play or "float".

I sold my 600X a while back so couldn't remember exactly how the gear lash was setup. I just remember that the gear mesh was too tight if I didn't pull the boom out a few millimeters; thanks for confirming this.

Anywho, even if the gear mesh isn't altered by boom position, having the boom crammed into the gearbox can potentially cause the torque tube to flex. So either way it's best to back the boom or tail case out a few millimeters.

[nc-dogman]

what if your running fixed endpoints in esc. I saw this same thing in my 550x build i just finished. Only had 4 test flights throwing hard rudder piros and doing hard punchouts to set everything. Was messing around with tail gains and parameter menu tail settings and Tx gyro gain. Calibrated esc edge 130 for fixed endpoints high throttle and low throttle. She is about dialed in, and I saw the gears....front and rear sets are toasted!