Tail hold/wag problem on Hornet CPX - RC Groups
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Feb 09, 2004, 10:28 PM
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Barry Janzen's Avatar

Tail hold/wag problem on Hornet CPX


I am back to working on my CPX again. I got frustrated with it and put it on the shelf for a few months. I never could get the tail solid. I tried everything to get the vibes and slop and sticks out of the setup. Question is--should I be able to have a tail that will hold under climb outs?

Tonight, I found that my front cone gear was slipping so I CA'd that. I also found that the rear bell crank seems to touch the gearbox. Anyone else run into this?

Should I have full stop to stop travel on the T/R? Mine seems to bind after about 50% of the throw.

Please help....
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Feb 09, 2004, 10:41 PM
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It's nice to get the slop out but friction is the worst part. You want to get full travel IE: all the way against the case/bearing to the other extreme, against the hub. Try using a ton of lithium grease on the "threads" for the grips, widen the holes on the pitch slider "ears" where they attach to the grips(just to the point where theres no friction). Be sure the "ears" on the slider aren't rubbing against the grips as you move the slider back and forth. If it rubs, bend the folding point until the "ears" don't cause friction.
Feb 09, 2004, 10:43 PM
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By the way,

Once you've done all this and it STILL wont fly right (probably wont) . Let us know what the tail is doing and we can debug from there

Also, what gyro? if you don't have a GY240, consider one.
Feb 09, 2004, 10:51 PM
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Barry Janzen's Avatar
Thanks Chris,

I am running HS 50's all round, GY240 in HH mode at 75% gain, Razor Heli V2, Etech 3s1p, cc10 in high rpm Gov mode.

I will try the lithium on the threads. Haven't tried that yet.

Feb 09, 2004, 11:28 PM
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If you need me to take pictures of the steps to take to unbind the tail I have no problem doing it.
Feb 09, 2004, 11:45 PM
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Barry Janzen's Avatar

I have good WL grease. No problem there.

I have two questions.
One--What moves on the threads in the blade grips--the thread in the plastic grip or the thread in the T/R shaft?

Two--How can I get the slider to move better? I have greased it VERY liberally.

The binding is in the pin where the pitch slider goes into the bell crank. Do you think a anti-rotation setup on the top would help it move better?
Feb 09, 2004, 11:54 PM
Registered User
1. threads in the T/R shaft

2. Is it binding on the shaft alone without the bell crank? if so try wet sanding the shaft lightly and then reapplying grease.

Put the pin from the pitch slider inside the bell crank and "pinch" the bell crank with a pair of pliers until it loosens up. Try not to create slop within the bell crank though, a little bit at a time. If this doesn't help an exacto knife gently shaving the inside away would help but take it easy and check tolerance often
Feb 10, 2004, 12:21 AM
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Barry Janzen's Avatar

Should I glue the threads in the plastic blade grip? They turn very easy in there right now.

The binding is in pin/bell crank spot. I have loosened it up some and it is a lot better. Maybe it will only be perfect if I have a ball link there.

I just got back from flying it and the wag was much worse. The oscilation was three times as fast. I reduced the gain from 75% back to 45% and the wag is GONE!

Now I tried some climbouts and the tail would spin 30-45 degrees and then hold. Should it be able to hold heading? Am I expecting too much?

I have the HS-50 long arm on the middle hole. Should I try moving it in?
Feb 10, 2004, 12:26 AM
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Barry Janzen's Avatar
BTW, my headspeed is 2K.
Feb 10, 2004, 12:33 AM
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Glue the screws into the grips if you must, but be sure they're equelly screwed in so when you screw the assembly into the hub, the blades are equel distances.

Walts bell crank is the best available, I've heard too many bad storys about the helihobby version. So if you do upgrade it get Walts(it's what I run).

I doubt you'll beable to run 75% gain, but anything around 50% is great. If you have random drifting it's most likely the gyro seeing vibrations. The best way to dampen the vibes are mount the tail servo ON the vertical fin. This takes a little work but in the end it really does pay off. The V1 Hornets boom is just too thin in my opinion.

As for the spin on climbout, NO it's not acceptable. The tail should hold almost as well as a 30+ size when flying correctly. I know you probably have done this but, check your revo on the tail in all modes and be sure it's disabled.
Feb 10, 2004, 01:10 AM
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Barry Janzen's Avatar

I will glue the screws in the grips. I think one of the screws is a different length. Should I cut it off? I assume the slot will go into the shaft then. Right?

Dennis doesn't have any of Walt's bell crank in stock. Should I make my own? What ball link should I use? I have looked through my stock and can't find a ball that fits it.

Do you have your servo on the tail fin? Where is your battery in that case. Is it out front? Would you mind shooting and posting a picture or two???

No no no on Revo. I think I am getting flex on the T/R grips and flex in the linkage from the servo to the bell crank. Will focus on this next. Should I drill out the t/r blades so the bolt pinches them?
Feb 10, 2004, 10:07 PM
Registered User
Hi Barry,

Don't cut the threaded rods down for the grips, just make sure the grips are even distances from the hub once screwed in. To get the best distance away from the hub, screw the grips all the way into the hub and back them off a turn. This should make the grips very smooth with the white grease (forgot to note, others have tried diffrent lubes but later tried white lithium grease and elimated a lot of wag).

You can contact Walt directly for his mods (but I see on the Hornet form he's informed you).

Here are some photos of the tail mount setup, very easy


Erics an awesome pilot and that Hornet has done the best 3D ANY Hornet has

And don't drill the tail blades out! they don't have to dangle freely.
Feb 10, 2004, 11:57 PM
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hornet_dave's Avatar
I used a 2mm ball link (dubro maybe?) from the lhs to make the ball link bellcrank. I had to shave the peg on the tail pitch slider just a hair to get it to fit, but it works pretty darn good. The next time you need crash parts, buy a couple extra bellcranks (they're cheap) and try making one for yourself.

With enough massaging, the tail pitch slider will travel from hub to bearing without binding. All it takes is patience and grease.
Feb 11, 2004, 12:03 AM
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Barry Janzen's Avatar
Thanks Chris and Dave,

I have gone back to non-gov mode and finally got it flying right. You can see my saga here---http://www.hornet-heli.com/cgi-bin/bbs/ultimatebb.cgi?ubb=get_topic;f=3;t=005108

Will check with the LHS on the ball link. Thanks.

Thanks for the link on the H2. That is new to me. Will look it over further.


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