Consulting the internet turned up all kinds of potential fixes, all of which involved replacing the gears altogether with a new set. The blame seemed to lie with the 'faulty' or 'weak' gears of the Tamiya system.
But just by removing the turret lid & looking at the mechanism operate, it became very obvious what the problem was: the back of the metal gun mount was simply making contact with the middle 'ring' part of the metal turret support bar.
(3 'dots' above added by me) The 'rubbing' produced by this friction is what caused the uneven 'stuttering' up & down motion, and I could even see the scrape marks on the metal mount (below). This would surely wear out the elevation motor over time!
The best solution was to remove the support bar and grind it down a bit for extra clearance; not only for the flat part of the back of the gun mount but also for the two hex nuts near its sides... they too would make contact if not also remedied.
A quick sess with the Dremel produced a still-strong support bar by grinding with the original curve, instead of just cutting slots or grooves into it. The result is a still-rounded piece, but with the extra clearance needed for proper operation.
Here's a brief VIDEO to show the new smoothed-out elevation... wish I'd shot a 'before' video for comparison, but if you're reading this post then you probably already know what that looks like
https://www.dropbox.com/scl/fi/z9mbr6n1 ... j5gd2&dl=0
I knew there had to be a better explanation than "Tamiya's gears are poor quality" - since when does Tamiya build junk? The alignment of said parts may need some adjustment
but it just goes to show: don't blindly believe the 'popular' opinion!Related post describes what switches I used to mod the Futaba 4YF's firing controls: viewtopic.php?p=380359#p380359
