Hi folks

Hopefully someone can riddle me this...cuz I don't get it. And maybe there is nothing to get, but I thought I'd ask...

Everywhere I read about how important it is to have nice square linkage connections. And how important it is for the tail servo linkage to run parallel to the boom, nice and straight, etc.


So why does my heli (a HeliPro Black Hawk 450SE) and others features a tail servo linkage stabilizer mid-boom which snaps the linkage at the center of the boom? If the linkage is attached at this point (presumably to reduce flex) then it is not possible for the linkage to be parallel with the boom since the linkage connects to a point offset from the center (the tail rotor slider arm connection point).

So if one uses the mid-boom stabilizer thingy then the linkage HAS to be diagnonal along the length of the boom, and not parallel.

So what am I missing? Should I toss this mid-point stablizer of the tail servo linkage which would allow me to mount the servo such that the linkage is much more square and parallel with the boom? Will the linkage then bend? Are there aftermarket linkage stabilizers that I could use? How is this being solved?

Or is it a non issue, and I should stop concerning myself with this level of tuning perfection?


Here is a pic on Ka-plane's site of the BH450SE... notice how even as-new the boom is flexing:


Now that I have my S9650 dig servo installed I was able to eliminate the "bowing" of the linkage that you see in the pic. But I am unable to get the linkage completely "aligned" and parallel with the boom due to the linkage stabilizer/tail boom mounting point you an see at mid-boom. It stabilizes the linkage by snapping the linking into a slot, where it is held loosely to prevent flex and binding. But when snapped in the linkage is centered on the boom. So now what?

Thx in advance

Yep some of the linkage holders are not what they seem. First off you need to adjust the ball link as close to thr centr of the servo arm as you can. You only need about 7mm length on the arm. Or attach to the outside side of the arm away from thr boom. If that is not possible you may need to move the servo closer or further away from th boom to take the bow out. Another thing to do is drill the hole in the rod guide closer to the boom. Some times you have to change a little to achieve the result that your looking for. You need to have "NO Binding"

Good luck,

Jim

Thx for the info


I have no binding at all. I may not have been clear. The pic was provided as an example of what I am using and what I started with. The linkage bowed initially, but the heli flew fine. When I installed my 9650, I was able to get the bow out, but the slight diagonal connection from servo horn to the tail rudder slider arm has me perplexed.

But no..no binding. the linkage works just fine. Is nice and smooth. It's just not *perfect* and I know I could make it perfect but I'd need to either modify or eliminate the linkage holder.

So...

-Do I need the linkage holder? Can I just cut the holder piece off and just retain the boom support/wing portion? And then run without the holder piece, which would allow me to position the servo so the horn is traveling in the same plane as the tail slider arm, and so the linkage is perfectly parallel with the boom.

-If I have no binding and no issues should I just not worry about it? My concern is there may be more perfection to dial in, which would make for an even smoother and more authoritative flight. But maybe I'm worrying about the little details too much. Your comment suggests that binding is main issue so maybe I should leave well enough alone and let the linkage holder do it's job, even at the expense of a few degrees of linkage alignment.


I just dunno. If left to own devices I'll tweak and tune forever. lol



Also...is there a tail servo linkage length calculator or rule of thumb? I have my linkage adjustments set per Heli-Pro's manual (9mm between the linkage and the ball-end on each side of the linkage).

Thx

If it aaint broke dont fix it

Ah, if I had a nickel for every time I should have heeded such advice...

And I didn't tonight either. The urge to tinker is too great. Especially since I'm off of work this week!

So, all seemed to go pretty well. I now have the tail servo swung over on the left side of the boom, with the servo reversed on the tx. The linkage is mounted on the outer-most hole on the horn and mounted inside the horn, and the other end is mounted to the inside hole on the tail slider. This arrangement seems to yield the most bind-free, parallel, squared-up linkage/servo horn/slider arm geometry that I can get out of this heli.

I also pulled off the idler pulley while I was in there. :-) Surprisingly the belt did not need a slack adjustment after that. I thought it would. But it seemed to get from "just barely too tight" to "just right", so I'll leave it be and keep an eye on it.


The only thing bothering me just a tee tiny bit is that the linkage is a hair off-line in the vertical plane. Prob about 1mm or less. I know why...it is because I only spun the servo mounts instead of removing the boom and reorienting them. For now, this seems fine. Next time I pull the boom off I'll flip them around. Just didn't feel like disassembling the tail and boom again this weekend.

Now I'm off to sand my blade mounts down so they aren't so tight. Darn CF


Thx folks. Test flights tomorrow. Will report back for anyone who might be interested.