tail control rod thread engagement 700N DFC

[rhodesengr]

well I had a little problem today. The tail control rod along the boom pulled out of the ball link back at the tail. Seems that when I had the servo at 90 and the arm between the long and short rods at 90, the threaded ends don't go very far down into the links. I guess I just didn't have enough engagement.

The question is how to fix it. The rod itself is not adjustable so it seems like I'd have to run the mid-arm at not quite 90 degrees. If I screw the links on the front rod in more, then I'd have to screw the links on the rear rod down further to compensate. But the middle arm would not be a 90 anymore.

Is there another way?

I noticed that the long control rod part in the kit does not match the manual which shows an adjustable rod going in the front end of the rear rod. I could fix this problem if the rear tail control rod was a little longer.

Just to be complete, this is gas conversion which uses Helibug side frames so its possible the tail servo is a little further forward which would thrown the link placement off.

Anybody else notice this issue with a stock 700N DFC?

[DCflyer]

Thats really weird. I can't see a fresh link popping off like that. How many mm's would you say your thread engagement was?

You could try a Quick UK "rocket city" ball link and ball kit. The links are quite a bit longer than Align's - about 1.5 times as long and really quality links. I think Ron Lund is where I got some. They won't work with Align balls though since the links are a little smaller in diameter so you'll have to get the ball kit as well to replace in the tail linkages. They would certainly give you the needed length and the link body is quite long so them slipping out shouldn't be an issue. They will fit the stock Align rods.

[rhodesengr]

Hey DC, Thanks for the tip. Ali at Helibug also mentioned the QuickUK links but didn't mention the balls.

I am not sure how much was threaded in and had been real careful to try to balance the thread depth at each end they were not in that far.

This was new build. I maidened it last weekend and it failed today on the second time out so its not like its has flown a bunch of times and suddenly failed. It must have been marginal.

[banditpowdercoat]

FYI, My mid arm is not 90 with the servo and tail slider at 90. It is pulled a bit closer to the servo and tail. It gets pretty much 90 when the counter tail tq setting is applied tho

[rhodesengr]

Originally Posted by banditpowdercoat

FYI, My mid arm is not 90 with the servo and tail slider at 90. It is pulled a bit closer to the servo and tail. It gets pretty much 90 when the counter tail tq setting is applied tho

Did you set it that way to get more thread engagement on the long rod? I wish I had done that . I set mine for neutral tail with both the mid-arm and servo right at 90. Then when I added two turns of right rudder, it made the thread engagement even less. I have some of those Quick UK links on the way. I'll use some combination of the Q UK links, cheating the servo forward, and cheating the mid arm forward to force the rod to be shorter.

Seems kind of hit or miss where links end up on Align control rods. The elevator servo links are screwed almost beyond all the way in. It was hard to get the rods short enough. Other links like the tail rods seem too short and hard to get them long enough. You'd think after all this time, they could size the rods so they use like 75% of the thread: enough for plenty of thread engagement but not threaded in so far the rod is hitting the inside of the ball link. Plus be uniform for all the rods.

[banditpowdercoat]

Got mine used. It was how it was set up, I just fly it, and seems to fly great on tail. Same piro speed either way etc.

[rhodesengr]

Originally Posted by banditpowdercoat

Got mine used. It was how it was set up, I just fly it, and seems to fly great on tail. Same piro speed either way etc.

Oh mine was flying great until the tail rod pulled out. Just a matter of 1 or 2 mm's of rod length.

[banditpowdercoat]

Then I wouldnt worry about the middle lever angle. Because its a even see saw. There wont be any curve effect so to speak. If servo end moves 5mm linear, the tail end will move 5mm linear. Even though the ball end travels in a ark. The physical straight line movement of the pushrods will be the same in/out on both sides

[rhodesengr]

Originally Posted by banditpowdercoat

There wont be any curve effect so to speak.

well I don't know if I agree with that. The balls on the mid-arm travel on arc-shaped paths. If you went much past 45 degrees, you would not get much displacement beyond that.

[banditpowdercoat]

But the mid arm is not a servo. Its the degrees the arm will rotate that will change at the extremes, Untill you run out of travel. The mid arm doesnt care what angle it has to turn to get the movement. ie, 2mm shaft movement in=2mm shaft movement out, but say 15* Now move 4mm in, will still get 4mm out, but the mid arm will rotate 43*. Just arbatrary numbers but that doesnt matter. With a servo, we see less Linear travel at extremes because TX stick movement is Shaft degrees. And yes, then at the extremes, the linear distance moved becomes less. But for a mid see saw like this, It wont matter.

[rhodesengr]

so it looks like part of the root cause is a difference between the Helibug frames and the Align frames. See this post if interested with photos.
https://www.helifreak.com/showpost.p...2&postcount=11

With the Helibug conversion frames, the tail is a little over 2mm further back relative to the mid-arm so the rear control rod needs to be that much longer. Since the rod is not adjustable, you'd have to back out the ball links about 1mm each. The longer Quick UK links should fix the problem but I wish I had known there was a difference while doing the build.

[banditpowdercoat]

Ohh damn. Good to know, and they coulda included some longer ball links or something with the kit.