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450 Class Electric Helicopters 450 Class Electric Helicopters manufactured by Align, Tarot, SYMA, Airhog, Chaos, HK and similar.


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Old 01-20-2007, 03:56 PM   #1
phemmert
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Default Ball link proper installation

Being a re-tread from R/C airplanes and sailplanes, I thought I would give helis a go! So far very excited about building my new T-rex 450SE. Thanks to all the excellent videos and galleries. Especially Finless Bob, those videos would leave me in the dark without them.

Having not used ball links at all in that other "modeling" life, my basic question is what is the preferred technique for attaching a ball link to a servo arm? Obviousy, this is crucial, as separation can prove disasterous. I'm thinking a screw through the ball, nut on other side, with CA? Input solicted, thanks in advance for answering the ultimate newbie question.
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Old 01-20-2007, 04:08 PM   #2
M249
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Ya, to get a ball on an arm, do the following:

1) make sure the screw (they came with the balls in your kit) hole in the arm is not too tight, if it is, carefully drill it out.

2) Go ahead and screw the ball on, using the provided nuts on the opposite side.

3) Dab a TINY bit of loctite (blue works well, still easy to remove/clean, but holds well) on the nut, as it will run into the threads. Dab off any extra so there is no mess with a paper towel.

This method will get the balls in the arms for good...until you want to remove them, of course.

Oh ya, and when attaching the links onto the balls, make sure the little "A" on the one side of the link is facing away from the direction you are pushing the links onto the balls.

Good luck and have fun with your new Trex!
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Old 01-20-2007, 10:24 PM   #3
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The "A" to the head of the ball.

Personally I don't obey that rule. I don't see that mechanically it can really actually matter. Even if one side does have a fractionally smaller hole.
I try to have them "A" out (just in case)....but if an adjustment needs it in to be a perfect result (eg blade tacking), I don't care which way it had to be put on.

And yes, you are right! It is highly important that NOTHING comes loose on a heli! So always use nuts if you can (eg ball on servo arm), and loctite all metal to metal threads. CA all metal to plastic ones.
I even loctite my pinion to motor shaft. Stuff like that.

Just think logically about what would need some form of "loctiting"...it is pretty straight forward.
Ummm....everything.
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Old 01-20-2007, 11:02 PM   #4
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Quote:
The "A" to the head of the ball.

Personally I don't obey that rule.
Bad boy! There is no reason to NOT use that rule and yes it is important to how your links work a wear. Sure you can use them the other way and they may work good for a while but as they wear you might be in for a suprise!

Saw a dude POP one just recently!

Bob
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Old 01-20-2007, 11:53 PM   #5
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Hmmm...I guess you would see a lot more results than I would Bob!!
But I am going to blame those cases on poor maintenance!
Because.....

From testing then in either direction, and their motions and freeplay, I could see no difference.

Then I checked the balls to see if it is not truly round, which would then tell that the link is likely to not be equal internal curvature from either side. But I could not discern that it was not round. And if it is not, then there is no notable difference in using either direction.
You don't really want a ball that is not perfectly round, because it will alter the friction levels when the link is at angles. And I doubt they would design it around that happening. So I would assume it is truly round.

If the diameter of the links hole is less on one side, once the link is on the ball it will result in identical motion and wear for either case anyway. The link does not really know which way it is on, or which way is the head or mount of the ball. So it will not alter wear rates at all.

One thing I have not checked, and might be the case, is that the smaller diameter hole is on the Non-A side. Though pressing them on either way doesn't seem to show this is the case. (hard to measure with feel tho).
The reason you would make the inner side the smaller diameter is that any sloppy link would always attempt fall off to that inner side of the ball first (as the smaller hole prevents it heading the other way as easily) and thus when it fall 'inwards' you still have some shaft to give some linkage maintained. Rather than where it falls totally off the outer side and you then have zero linkage/control left!

This is only going to happen on notably worn links (or worn balls). So if you were not paying attention to the fact you had one (or more) that loose, then you deserved the result! lol

Ergo....lack of proper maintenance.

So I can see there COULD be some small reason to use them the 'right' way. But I would prefer precise adjustment above that aim. And I will stick to using the 'right' way when it co-incides with accurate adjustments.

Note that one end of a linkage can always have the link used the 'right' way on purpose, whilst the other end one is possibly right or wrong according to your adjustment needs. And it will be 50-50 odds that those rest end up the 'right' way. So most cases (by odds) will have a heli with 75% of the links that 'right' way! hehe

I think the higher precedence aim of maintaining "No sloppy links", and highly accurate adjustment, will easily overcome the 25% likely total of non "right way" link useage being any concern.

Food for thought???

I will let you know the day I have a linkage fall off!! LOL
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Old 01-21-2007, 01:09 AM   #6
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Wel.. you can go on and on about this and it has been discussed many times over and over again... But if it really didnt matter... Then why would they make links this way and not make then universal (like Rocket City links)?
There is a purpose and a reason they are made like this.
Argue all you want but making moldes for these is not cheap and if they didnt have to make a "side" they wouldnt.

Finally there is NO REASON to not use the links properly! You can get tracking perfect using them the way they were designed. It's being lazy that makes you use them wrong.... Thats OK... I will continue to use them as they were designed to be used even if it doesnt matter (which I beleive it does for a better running system)

Bob
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Old 01-21-2007, 01:56 AM   #7
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Who makes ball link pliers that are small and not metal? For one, the set i have are almost too big for my trex and way too big to remove the links from my HDX300 v2 head. Second they are metal and they scuff up the ball joing and scratch the plastic quite a bit.
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Old 01-21-2007, 02:01 AM   #8
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Johnny actually your are right! There are many ball link pliers out there and MOST are junk because the fork arms are TOO THICK! I am buying pliers (and many friends have and love them) from MTA hobbies as they get this green handled pare that say HELIHUT on them. BEST pliers out there and work GREAT on the Trex!

Bob
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Old 01-21-2007, 02:12 AM   #9
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Thanks to those who replied quickly to my original query. I am a pefectionist by nature, and I wanted to make sure this project is not going to be mucked up by shooting in the dark, on something seemingly innocuous.

As to how the links should be attached to to a ball, even as a newbie it is apparent that there is a reason that these links are marked in the manner they are. As an areonautical engineer by education, and a B-737 captain in my other life, I've learned to trust those who design the pieces and parts, whether it's a Boeing jet or these ball links that make up linkages on a model heli. The "A" goes to the outside; if that creates a problem in link length, then I suppose that the distance will have to be made up elsewhere.

I won't second guess those folks who are in the business of designing and manufacturing parts for the "end user." And major kudos to those of you who have blazed the trail..attempting to reinvent the wheel (or ball link, as it were) is a waste of precious hobby and flying time. Thank you!
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Old 01-21-2007, 02:13 AM   #10
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The Helimax ball link tweezers work very nicely also.

What I do is actually tap the servo arms and screw the ball bolt into the arm, then add the nut. The a drop of CA to make sure nothing moves. I put a dot of blue Loctite in the nut before screwing it on. Keep the blue Loctite away from the plastic or it may degrade the plastic and the arm shatter.

Blue Loctite doesn't wick into the joint. They do a make a green "Wicking Grade" that is designed to be put on after the fastener is installed.

As for the A on the link, the bal is round, but the link is not symmetrical. The A side is smaller than the non-A side. When the link is on the ball, the link is offset slightly to th A side. The groove is part of a sphere, but the center line of the link is not the cneterline of the sphere section.
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