Anyone stripped a Spectra G maingear in flight?

[James Vaello]

* Yes, this is a repost from RumpRyder, seems MA is about dead over there*

I finally got some meaningful flight time on my Spectra today after getting a Torpedo V3 that will actually stay on inflight. On the second flight, I heard a wierd sound on a vertical piro and brought it in to land. At first, I thought that I ate a tooth on a crown gear, only to find a completely toothless main. It looks melted, but it is hard to know.

My clutch takes a little time to engage, not excessive. It might be slipping, but I don't think much. The motor shows no signs of a lean run visible through the exhaust port. Running 720 V-blades with 7:15 gearing, 231, Torpedo V3, and a 601.

I made one flight, waited about 5 minutes, fueled up, and started the second. Halfway through the second tank, I noticed the click sound, heard excess revving and autoed in.

Any ideas? BTW, the gear mesh was perfect when I started.

[bigrcr]

Your clutch should not slip at all except for a split second as it engages. If it is slipping it more than likely has come unglued if it has not been damaged. At any rate the clutch should not do this unless it slips and grabs violently and this you would hear and see in flight.

I would think that the mesh was not correct or the pinion is incorrect. I have heard of some models having an 11 tooth pinion supplied which would definitely blow a main gear. Most of these folks had problems totally with the model. The correct pinion is a 13 tooth, count yours. The main gear will be a 93 tooth.

If you have the correct gear(s) installed then I would check to see if the side plates are slotted and have allowed the mesh to move.

In any of these cases the pirro will always get your gears!! :oops: :arggg: :arggg:


Later,

BIGRCR-John Garst

[James Vaello]

Not confirmed yet, but I think that my clutch is slipping, transferring a ton of heat to the pinion. I am going to tear it apart and look into it soon. I stripped (melted???) another gear in flight. This is nuts...motor is running smooth and cool.

James

[bigrcr]

Ouch, sorry to hear that. :arggg: Did you count the pinion and main gear teeth yet?

BIGRCR

[James Vaello]

Yep, just checked, 93/13. No blueing on the clutch, looks good there. I figured clutch as it takes a bit to engage. Maybe not.

I love this heli, but I am having second thoughts. This is expensive for a 12 minute flight.

Could RPM be an issue? I am running ~1950 with my Revlock set for 14k. I don't think so, I have seen many other helis with 231's at 14k.


EDIT: Just looked at an old post, and no, I built this heli...the frames are not slotted allowing the pinion to drift. But one thing I have noticed is a tight spot spinning the auto hub past one spot on either of the two dead gears. Should I put another one way set in? I have 3 others available.

[bigrcr]

You can try another one way if available as it will only cost some time.

Make sure the liner is still glued into the bell as they can come loose. This should be very noticeable as the motor would over-rev nearly instantly or would snatch the tail (or main gear) as it slipped during flight.

A reasonably tight spot could heat up the main gear and get material melting in that area, then as it builds-up, rip out the teeth.

Sorry, I am just thinking out-loud right now.

12 minute flight hmmmm.., :wink: I doubt the needles are set too lean.

At any rate a slipping clutch is a problem and that needs to be corrected before proceeding.

BIGRCR

[James Vaello]

Just checked the clutch liner, It can't be slipping in the bell. Unless it heats and does, but I would notice it grabbing and slipping.

12 minutes, well yeah, that's about what I get per main gear ;)

A little sooty on the plug, and no scoring ANYWHERE in the engine.

[rbort]

Maybe you ought to drop the rpms and stop the virtical piros and see what happens. You need to get back to a working platform that stays together and then you can narrow down the problem easier this way.

If its any consolation, I've had my Spectra since 9/05 and yesterday I completed flight #301 with it. Each flight is 15 minutes long so that is just over 75 hrs run time. I am still running the original main gear (inner/outer) and my clutch is original as well.

On a side note, I have never exceeded 1750 rpms and most of the time I run at 1650 rpms. I do many pirouettes, but I never let the stick go for an instant stop. I start out slow and go to full speed and then slow it down to a stop. I don't do vertical pirouettes. I tried that with my 1005 gasser -- fast forward flight, roll to knife-edge and piroutte around and release the stick but I stripped the inner gear that way. Decided OK that maneuver wasn't worth the gear.

I doubt your clutch is slipping. When clutches slip, they act like automatic transmission. You throttle up and the engine revs first and then the rotor catches up later. The engine does transfer alot of heat into the clutch bell/shaft, so its normal for it to be hot after a 15 minute flight and is a non-issue. Generally that hotness is hot enough to feel hot, but is not hot enough to burn you. If the clutch is slipping then its the latter but you need more than 300 flights to wear out a clutch, I'm proof of that!

-=>Raja.

[James Vaello]

After talking to Tim today, I think I might have found my problem. First, the upper pinion bearing had been spinning. Second, the bearing between the clutch and the uni-ball driver was shot. It allowed for 2 degrees plus of play. I talked to Jeff regarding the problem as well, and he suggested polishing the pinion with scotchbrite and sandpaper. He also suggested making sure all bearings were green loctite on inners and red on the outer.

We shall see I need to get a main gear ordered from Ricks. The saga continues, but is hopefully solved.

RE: The headspeed, Tim says that 1950 is A-OK. I like the pop that I get from it as well.

[James Vaello]

FWIW, the problem turned out to be my upper pinion bearing. It was notchy and nasty, and replacing it solved the disappearing main gear issue.

Man I love my Spectra now. Time to buy a 26 piston, jug, and ring and work on some porting! :)

James