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Futaba-RC . Fast Lad Performance . Esprit Model

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Miniature Aircraft Nitro/Gas Helicopters > Spectra G tail gears wore out.
 
 
GyroFreak
Key Veteran
Location: Florida ... 28° 50' N 81° 16' W

I lost tail control on my Spectra G yesterday, got it down with no damage. I found the tail drive gears were both worn down to the point the teeth looked like little stubs. This is the closed transmission and I always kept it well greased (molubdenum) and I thought I had it adjusted where the play was very small, no backlash but turns freely. It had about 10 hours on it, no 3D, just mostly hovering. The gears were still firmly attached to their shafts and showed no signs of slippage. All the bearings feel smooth with no rough or slop in them. .
Anybody else have this happen ? I will contact MA Monday and see if they have any suggestions (and new gears).



Support bacteria. They're the only culture some people have. !
03-30-2008 04:24 AM
 
 
Toadster25
Veteran
Location: Iowa

did you ever take apart and inspect the gears for wear or did you just put some grease in through the hole? Just wondering because I was thinking about just greasing mine through the hole because the other 2 times I've had the gears out I didn't see any wear or problems but now maybe I will check them again.

btw I haven't had any problems with my tail gears on my spectra. I wonder if maybe the mesh just wasn't set right? I think one of the reasons MA came out with the open tail gear box was because of this probem that was usually blamed on the gear mesh. It is kind of tricky to get the mesh right on the closed box and the open box was suppost to be easier and you can actually see the gears but turned out that the open box couldn't hold up to the Spectra G vibrations so they had to go back to the closed box.
03-30-2008 05:33 AM
 
 
GyroFreak
Key Veteran
Location: Florida ... 28° 50' N 81° 16' W

One time I took them out to check them and they were fine. I grease thru the hole and this time when I took it apart it was full of grease so the hole greasing is getting in plenty of grease. I'll let you know what Min Air has to say about the type of grease and how to set the mesh clearance. I guess I'll start checking it every few hours until I feel the wear is not coming back since it is fairly easy to open and pull the input drive gear for inspection.

Support bacteria. They're the only culture some people have. !
03-30-2008 05:56 AM
 
 
Dr.Ben
Elite Veteran
Location: Richmond, VA, USA

Smooth and with little or no backlash does not assure an accurate mesh. Think of the two gears as forming the 90 degree corner of a picture frame, beveled/mitered corners and all. If one gear is running shallow or deep to the other such that only part of the total tooth area is covered, then the mesh can still feel smooth and will have little backlash, but the mesh is NOT going to hold up over time. As soon as it wears in just a little, the mesh will start to float. Since the tooth to tooth coverage isn't complete, wear is accelerated and quite dramatic.

It's fairly easy to spot when the gear wear I decribe. Under close inspection of the clean gears, you can see the polish marks from running unevenly distributed across the tooth. Inspect your after a gallon or so of running and see what it looks like.

Also, if there is ANY, and I mean ANY, endplay in either the input or output shaft of the box when it's assembled, the mesh will not hold in flight.

Ben Minor
03-30-2008 04:51 PM
 
 
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Thunder Power RC . Real Raptors . Mikado Modellhubschrauber

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Miniature Aircraft Nitro/Gas Helicopters > Spectra G tail gears wore out.
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