What happened to the trex 700 tail hum?

[-kenny-]

Takes me back to the good old 3gx days. When everybody was reporting a backward drift and align was dead silent about it also

[Tower]

deleted

[rcflyerheli]

Wizza, I think that you hit on the issue I believe sure aggravates the hum issue, and that is side to side play in the tail shaft. I have built 4 of these tails, and 3 of the 4 had noticeable play. Two of the 3 that had the play took .2mm shims and the third took .1mm.

My feeling is that any outward thrust on the tail blades causes the bevel gear mesh to tighten up if there is play in the tail shaft, and cause it to run rough. I know that I could feel the tightness in the mesh just by turning the tail by hand. Once I shimmed the tail shaft, the gears felt smooth and I have had no hum on any of the 4 tails I have built.

I also agree that the TT splines has enough slop that I didn't feel comfortable with it, so I applied one wrap of Scotch tape to the silver end of the TT where the splines are. Any more than one wrap is too thick, but the one wrap fits perfectly and removes the slop.

As far as blades, I have run only Rails and Edge SEs, with equal results. One thing I haven't ever understood about all the posts I have read is that most everyone seems to think that running the Rails just masks the hum. The blade part of the equation is one of a number of fixes that can be done. IMHO, whatever stops the hum is a fix, not a mask. I have no reservations on running the Rails, and when I run out of Edges, that will be my blade of choice for now. I did try the Zeals, but they were a full gram heavier per blade and just didn't run smooth for me.