Jellyson,
When you say, "No lift-off on crash repair, requiring pitch adjustment." Does that mean if you crashed and had to replace the main shaft? It all makes alot of sense, seems like I adjust my pitch control linkage to often. But not necessarily after a shaft replacement.
I've only changed out about 3 shafts in the last year, but adjusted my linkage dozens of times. What's up with that? I haven't had the no lift-off syndrome, but can tell that the pitch is off by 1/2 turn or so on the control linkage. Hmmm.
Just a curious question,
Dave / Choppersrule
ORIGINAL: Jellyson
Second:
No lift-off on crash repair, requiring pitch adjustment: I've seen several people reporting this problem and I believe I have found a possible cause. I have carefully measured several main shafts and I found that the height from the top of the main gear shaft boss to the tiny hole for the head-retaining shear pin can vary, in my small sample, by as much as 0.040 inch (~1 mm). That may not sound like much but it is this distance that determines the collective pitch adjustment of the head, and it can translate to enough pitch change at the blades to be noticeable in performance--like preventing lift-off or requiring a lot more or less throttle to lift off.
The way to fix it, of course, now that I understand it, is simply to lengthen (or shorten) all three servo link rods evenly by one full turn. That should adjust the collective pitch evenly to compensate for differences in the height of the shaft hole.
Of course you should check all this with a pitch gauge if you have one.