Tail Issues Modifications General Tail Chat

[thefrog]

That is a neat job. Just a word of caution - I used to put a brass insert over the carbon rod but I had two cases of the metal threaded bar snapping. There was some discussion about not leaving any threads exposed to avoid this. So I'd suggest the same in your case - at the tail end turn the ball link all the way to the brass, don't leave any thread exposed. I've moved to a different solution, similar to the titanium rod ends posted above.

[jcflyer]

Originally Posted by smsodhi

Here is what I have come up with to strengthen the end of the CF push rod, not too different from the Brass insert from a tail rotor.Its from a connector. I drilled through the top and cut away the extra brass to make a flat surface and this left me with a nice end that covers the cut end of the CF rod as well.

Hey Satnam that's great I have been doing this since the day I got my Diabolo,
has worked great since then!!!

[smsodhi]

Thanks guys, I'll keep that in mind thefrog, I remember that story.

[trillian]

Is it OK to have a little play in the tail grips? If I pull outward on the grips I can see about maybe half a mm of play. Obviously when the tailrotor is spinning they will be pulling outwards against the thrust bearings.

I just want to be sure that a little play isn't a sign of a potential problem.

The screws holdling the grip assemblies onto the hub seem snug so it does not look like they're coming loose and backing out.

I'm paranoid about the tail and the control rod now!

[smsodhi]

Slight outward movement is normal in the tail grips

[JRAY]

I like that. What kind of connector did you use?

[smsodhi]

Thanks, just your usual 4mm female connector.

[thefrog]

A tail related question - I've installed some NHP 105s after the Rails died. Due to their shape they don't fold properly. For those running NHP tails are you trimming them so they can be folded for storage?

[snbartley]

Here is what I did with the control rod. Took the idea from my Goblin builds. So far no issues. But think I may try the titanium ones soon. Like how clean they look.




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[trillian]

So am I right in thinking that where the problems have happened with the tail pushrod it has been due to the carbon rod splitting at one end?

Mine has been OK so far with just the normal construction of the threaded bit epoxied into the carbon rod. But I am inclined to make up a really bullet-proof overkill pushrod just for peace of mind.

I have lots of them to compare construction with on other helis. One that I have on a Robbe I'm working on has some nifty ali fittings that have a pin through into the carbon rod that looks sturdy but what I'm thinking would really be the most secure would be using an extra long bit of threaded shaft, so maybe two or three inches glued inside the rod so it's definitely never going to come loose and then just some kind of anti-splitting device on the ends like some that have been done here.

[Mercuriell]

Nope the couple of failures I have read about occured where the exposed metal pushrod snapped - presumably due to metal fatigue - I haven't had this issue on other helis but I guessed they're not as high stressed as the Diabolos.

[trillian]

Originally Posted by Mercuriell

Nope the couple of failures I have read about occured where the exposed metal pushrod snapped - presumably due to metal fatigue - I haven't had this issue on other helis but I guessed they're not as high stressed as the Diabolos.

Ah so that's why the advice is to not have any exposed threads, thus having just the threaded shaft unsupported on its own where presumably it can flex just enough to fatigue.

[OverTemp]

And when you glue it in, make sure all the threads are filled with JB Weld!!!

[snbartley]

I installed my new and improved RcTek tri tail yesterday. I have been asked to do a little review on it once it was done so here it is.

After reading many posts about how smooth a tri bladed tail is and how you can run a shorter blade and maintain the same control I decided to give it a go. This was in partly motivated by a hard landing resulting in needing new tail blades because of having no ground clearance when using the stock 130mm blades. I initially installed a add on to the tail fin to gain some ground clearance but did not like the look.



On arrival and initial attempt to install the new tail I found a few issues. The initial design required the use of an Align 600 slide bushing. This however caused several issues. First it was much shorter than the stock bushing resulting in a lack of threads engaged in the yoke which was concerning to me.



It also had a larger head on the bushing which caused binding on the tail case unless I was to change the travel of my tail servo which also would change the tail pitch of course. The yoke was also machined flat where it butted up against the tail slider which caused binding when trying to tighten up the bushing into the yoke. I tried adding some spacer shims which did help but with the addition of the shims there was even less threading to bite and even with red loctite I was not comfortable that it would all hold together.





I spoke with Bob who manufactures the tail and explained my concerns and made some suggestions to improve and help with the above issues. The tail was send back to him and he made the changes. The new and improved design has a yoke that accepts the stock slide bushing. The yoke is still a beautiful machined aluminum piece which now has an inserted Delrin core. This core is threaded for the stock bushing which allows for a tight slop free fitting without the need for loctite, similar to the stock yoke setup. The Delrin core also doubles as a built in bushing to keep the slider bearing from binding on the yoke. This all works great.




To build the slide bushing is removed from the stock yoke.



Then the stock slider and slide bushing are threads onto the RcTek yoke until it is tight with no slop and no binding. Then installed back onto the tail shaft. The tail hub has three grub screws to secure it. One in lined up with the tail shaft notch the other two ensure a very secure fitting.




Did a maiden flight and all is well. Tail is very smooth. I don't have the ability to see vibrations logs but there was no visible vibration. Tail runs very quiet and consistent. Was only able to do a little hovering and pirouettes to see how it works and that went well. Hoping this next week to get out and dial in the gain settings and see how well it flies. Will post more as testing progresses.


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[crash at 42]

Nice job is the tri tail available for purchase

[smsodhi]

Great write up Scott. Really like the look of the tri tail.
I look forward to hearing how it performs under pressure as compared to the original.

Are those KBDD blades, did you need to balance them?

[snbartley]

Yes it is available for purchase from RcTek. Here is a link. They may have it on hold for a bit as Bob makes the changes I listed above. I know as of yesterday he was making a fee final adjustments to get it completely dialed in.

http://www.rc-tek.com/store/index.ht...id=0&x=12&y=13


As for the blades yes those are KBDD blades. Trying out the 102mm blades. I did balance them. Balanced the entire system all together. Will do some testing to see how well it works. If the blades are too soft I will try some carbon blades of some sort. Time will tell.

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[Luvmyhelis]

Scott, excellent write up. I ran mine with three different sized Kbdd's and also a set of plastics Chuck threw in my original box. The blades Chuck sent worked much better and had less vibes. I have four different brand CF blades headed my way for testing this next week on the same tail when it hits this week, as Bob sent mine just today. I had the original prototype before Scott suggested the changes we are seeing in his stellar write up.

As far as vibes went. The tail produced the lowest vibes on any heli's (out of thousands now) vibe logs I have ever seen. Including my own. You need to understand how severely anal I am before understanding that. I am driven towards vibe free perfection. Even in hard stops from piros the tail rarely spiked past a normal (other brand aftermarket) dual tail setups running neutral vibe levels in a hover! Let me rephrase, I saw lower vibes on stops than other tails see in hovers!

Why? Smaller disc area with less turbulence and seriously less shaft deflection due to the inherent characteristics of two bladed systems vs three. If you understood what I just said, you already understand why it works.

[trillian]

Originally Posted by Luvmyhelis

As far as vibes went. The tail produced the lowest vibes on any heli's (out of thousands now) vibe logs I have ever seen. Including my own. You need to understand how severely anal I am before understanding that. I am driven towards vibe free perfection. Even in hard stops from piros the tail rarely spiked past a normal (other brand aftermarket) dual tail setups running neutral vibe levels in a hover! Let me rephrase, I saw lower vibes on stops than other tails see in hovers!

Why? Smaller disc area with less turbulence and seriously less shaft deflection due to the inherent characteristics of two bladed systems vs three. If you understood what I just said, you already understand why it works.

Hmmmm, very interesting indeed. I'm thinking to myself that might be a really good replacement for the Kasama Faifa tail because the Kasamas are very sensitive to vibes due to using a small diameter but very rigid carbon boom and also the stock tail has been known to fail suddenly when the locknuts come loose.

[thefrog]

Originally Posted by thefrog

A tail related question - I've installed some NHP 105s after the Rails died. Due to their shape they don't fold properly. For those running NHP tails are you trimming them so they can be folded for storage?

Hey guys - anyone experienced this issue I'm having?