HBK2: Z-Bend to Ball Link Conversion - Pics and install notes

[orlbuzz]

A+

orlbuzz

[netdog]

So the final verdict is to use a seperate bec ? Thanks for the reply by the way.

[gregor]

Yes, I would run a BEC. Many people don't and don't really know how close they are to the BEC's limit. There's can be fine line between "I've never had a problem" and running dangerously close to an undocumented limit. You can't take the mfg's word for it. My ESC was rated to 2a but only delivered 1a. My tail servo was pulling twice its rated current. Put these together and what do you get?

Its not too uncommon to hear about another BEC failure in either the Esky ESC or any of inexpensive ESCs. I was luckly, I discovered it on the bench. The BEC I'm using is switching (vs linear) and was only $12.

[netdog]

Thanks again. I will definately go with an external bec. By the way, What servo would u recomend for the tail ? Rightnow I have the esky hh gyro, but will soon upgrade. Maybe a futaba 401.

[gregor]

That's a good question. I've not been too happy with my HS81 and was considering trying out the JR185. Cheap fast, but no replacement gears. I just hear someone else say they went from the JR to the HS81 and really loved the difference. Go figure. I've done a lot of work on the tail and its better than it ever has been. So its likely, the servo was never the problem. But be aware of the HS81 current draw. If my is "normal" then it sucks almost half an amp.

For a while I was considering the Futaba 3154. A little more expensive, but digital. Of course if you have the money there's the Hitec gyro/servo combo.

I'm still running the HS81 with the 2100t. Its fine for what I'm doing right now and I'll more than likely have a different heli by the time I need more out of the tail.

[xrbcoronalogoflyer]

hey gregor...you were the inspiration for this mod...btw, jag hobbies carries the upgrade linkage set, which eliminates the z-bend...ken

[orlbuzz]

xrbcoronalogoflyer,

Jag Hobbies is great! Very accommodating!

Tell me though, is that an upgrade kit, or just a regular kit? Could you give a specific link?

Thanks,

orlbuzz

[xrbcoronalogoflyer]

xrbcoronalogoflyer,

Jag Hobbies is great! Very accommodating!

Tell me though, is that an upgrade kit, or just a regular kit? Could you give a specific link?

Thanks,

orlbuzz

hi orlbuzz...here's the special links that i used for the servo to swash...
http://jaghobbies.com/images/rc_planes/hbk2/ek1-0598.jpg
the balls are alum...one of the links is long (maybe that servo should be upside down?)...i cutoff some threads and made all 3 the same length...ken

[gregor]

xrbcoronalogoflyer,

Thanks for the update. I'd be interested to hear the background for your mod as well as its effects on performance.

Regarding the balls, since they are aluminum, I wouldn't use them. I have the CNC head and it came with all aluminum balls (except 2). All of the balls wore quickly and even new ball links had slop. I've since replaced all the balls in the head with either Align balls where they fit and the B400 balls which are stainless steel.

The Align balls are also stainless and larger than stock, which requires larger links. I prefer the Align links to the Esky/Eflight links anyway. Since the Align balls are larger they don't fit everywhere.

[xrbcoronalogoflyer]

hi gregor...thanks for the advice...i have a bag of the short b400 balls, so i'll replace the alum ones...btw, the entire head assembly is so tight and slop-free, that when twisting the grips, the only play comes from the links-to-balls play...i'm waiting for a tail servo, then test fly...ken

[gregor]

the only play comes from the links-to-balls play...


When my head had serious tracking issues, one of the areas that was most problematic was the ball/ball link connection. I'd go further to say the only slop that has ever caused me issues was the ball/ball link connection. This is the main reason I put so much focus on tightening up the connections using B400 and Align balls. the link from the mixer arm to the blade grip has been replaced with Align balls, Align ball links and a short shaft. That link was the one that seemed to introduce the most slop and the stock parts are one piece, non adjustable.

[xrbcoronalogoflyer]

hi gregor...now that you mention it, the links that came with the esky alum balls were excessively loose...normally, with balls and links, i've had to pinch them to decrease binding...looks like i'll replace the balls and links with the b400 stuff - they seem to have tighter tolerances...thanks again...ken

[zimatosa]

So, I went to the ball links on my servos and have a few questions.... I have tower pros on the cyclic so I really do not have much room at all. I am either hitting the elevator servo with the threads on the ball of the pitch servo or hitting the motor with the elevator servo ball threads. I did the grinding technique to the threads but the glue does not seem to be holding very well on the threads. Do you know what the best glue for this application is specifically? Also, I was thinking of using balls that require the inserted screw instead of the attached threaded posts. I would be screwing them through the horn then through ball. Anyone try that before??

Thanks,

Z

[gregor]

I used CA (aka super glue) on the metal to plastic connection.

With large servos this setup will be tight. You can try moving the ball on the PITCH servo to the backside of the servo horn. I know one guy that ran it that way. I looked at it and it seemed like it'd be close to the canopy mounting pin. You'll need to experiement and see if it works.

The elev connection is also quite tight. I have mine filed flush with the servo horn and there's only about 1mm of clearence to the motor. I put some servo tape between the servo and the frame to try to flatten how it sits against the frame. Otherwise the servo tends to sit a little sideways, which pushes the horn more toward the motor.

The other option I had considered (but never needed to do) was to soften the servo horn (melt it) and push it back a tiny bit. I didn't like this option as it might slightly alter the travel when compared to the other 2 servos. If you have a computer radio you can fix things with endpoint adjustments. But you'd also need a swash leveler to do it correctly.

I'm not familiar with the balls you using. I've see the ones where the screw goes through the ball into the horn, but not the other way around. The balls I've seen like this are the Align balls which could be a little too large for these tight spaces in our tiny bird. The B400 balls are small and work well.

[zimatosa]

I actually have the ball on the inside of the horn already on the elevator and on the pitch servo. I used the "superglue" method but the threads in the servo horn failed to hold a few times during tests(non-flying).

The balls used on the Trex tail links I know for sure are hollow because I installed that part last week. I am thinking now that they might not sell those balls except in the tail kit?? I will look for them...They are hollow and would allow me to use a flat head screw from the opposite side of the horn(maybe even slightly counter sunk). Since the hollow part of the ball is not threaded, I would need a small nut with lock-tite. I would at least be able to trust it in flight. I will try your method once more though and maybe use a smaller pilot hole to start for tighter fit.

Did you use a tap or just screw the ball into a pre-drilled/sized hole?

Thanks for the input..

Z

[gregor]

The Align ball pack I used was HS1155T purchased at the LHS. My pack included SS threaded balls. I noticed that the same pack online is the hollow with screw type. Not sure why the LHS version was different.

Regardless, in the servo horns I'm actually using the B400 short balls. I used one of the existing holes and enlarged it using a small drill bit. Then I threaded the balls into the hole. The fit was very tight. I backed them out, coated the threads with CA then re-installed. They've held well for 200 flights. There wasn't enough threads to get a backing nut installed or I would have gone that route.

[zimatosa]

Kewl....Thanks again for the quick reply. I will start with fresh servo horns and drill smaller at first for tighter fit. Dying to fly!

Peace,

Z