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HomeAircraftHelicopterCentury Radikal G20-30 N640 Hawk Predator › First Crash - T/R problems
07-18-2002 07:53 PM  16 years agoPost 1
Fuj

rrApprentice

Fairfield, CA

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Well, yesterday morning I had my first crash with my Hawk IV. It was too windy for me but I think I had some t/r problems. I've already put it back together and had to change my main blades, lost a rod, and the feathering shaft was bent. I think I got lucky. This morning I already had it back in the air. I was hovering and the t/r seemed to be doing it again. I'm not sure if this is just normal or now that I've flown a bit I'm being more picky. In a steady hover with a little wind, the nose would jerk slightly to the left or right - I think mostly to the left - then stop. I have control of it, but these small jerky movements are making me think something is wrong. I've gone over everything and took apart the tail and all is good. Any suggestions? Thanks in advance!

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07-18-2002 09:24 PM  16 years agoPost 2
driftrider

rrVeteran

Cedar Rapids, IA. (In my own little world)

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I have a couple of questions for you...
What kind of gyro are you using? Tail servo?
What is the gyro gain set at? (Too much gain causes the tail to 'hunt')
Do the pushrod and ball links move silky smooth without any play, slop or binding? (Binding or sloppy tail controls will wreak havok because the commands the gyro give don't get instantly and smoothly sent to the tail)
Is the engine tuned fairly well (not too rich or lean)? (A over rich engine will cause the tail to wag too)
Does the heli vibrate or shake? (The vibrations might be causing the gyro to sense and react to no-existant yaw, turning down the gain will help, but balancing the heli is better)

Another possibility is that there is a glitch somewhere in the heli, or it's getting "hit" by outside interference. Make sure you do an antenna down range check with both the engine off and on. I go out as far as I can still see the swash plate move (about 100ft). I just got done chasing down a glitch in my Raven (the muffler flange was just touching the lower frame when it'd get hot and expand), and it would experience sudden jerking movements from all of the servos (it's really scary in flight). Check for any metal on metal/carbon rubbing, smooth bearings, insulation on wires rubbed off or cut, etc...

Good luck,

Mike

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07-18-2002 10:47 PM  16 years agoPost 3
Fuj

rrApprentice

Fairfield, CA

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I'm using a P2000II - I left the gain alone - in other words I didn't touch it out of the box. It's at 12 oclock. The t/r pushrod doesn't really bind - this could be it. I put the ball link at the servo end on the bottom side of the servo so it won't touch any other rods (as per the manual). I put the pushrod through the guide on the frame that's toward the rear of the frame but the guide at the front I did not. I was told that was the acceptable configuration. The only uneasiness about this is that when I move the t/r it is smooth movement left to right, but the pushrod rolls over that front guide. It doesn't cause any binding, but I'm thinking it should either be in the guide, or the guide should be removed. The engine richness is something I'm still trying to fine tune, but someone else had told me it was set up ok. It starts right up now with no problems and doesn't die on me. I'm hovering rock solid, it's just a minor and occasional movement. Could just be normal - I'm too new to know better.

I just flew it again and it appears to be better. Not sure what it is.

Thanks,
Dan

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07-19-2002 02:19 AM  16 years agoPost 4
ncostes

rrVeteran

Va, US

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Fuj

A zip tie slightly in front of that big front guide will help minimize the rod bending when you push it.

The other thing - make sure you rod guides are lined up so you get the least amount of friction (the first one will be higher than the middle or last one). I assume you ca'd them as per the instructions.

Make sure that when you push the t/r control rod by hand it is really smooth, and it's not stiff - like you have to push until a certain point, then it moves, and then it's ok.

Check out this thread - some good advice how to overcome this stiffness...

http://www.runryder.com/showtopic.h...static+friction

Once I filed down the part down everything was smoother.

You DO have to mess with the gain on the PG2000V2. That's the gyro I have.

What radio do you have? and do you have a channel set up for the gyro?

Basically you want to set the gain as high as possible without causing the tail to wag. You can only do this by increasing the gain until the tail wags, and then backing off a little.

Also - make sure that when your rudder trim is zero'd out, your heli doesn't yaw (turn left or right). If you have to set trim from your radio to keep it straight, you're reducing your throw in one direction. Make this adjustment by lengthening or shortening the t/r control rod.

Also make sure you have the ball for the t/r control servo out far enough from the center of the servo. Moving the ball out further is like increasing the gain on the gyro, moving it in is like decreasing the gain.

But you really should set the gain on the gyro first.

Also - if you set your gain to 100% and it still doesn't wag, you have to adjust the "gain resolution" (thats what they call it) with the little pot right on the gyro itself. Crank it up and then try again.

Try some of these things and let me know - I just finished setting my hawk up perfectly for t/r gyro with this particular gyro and my hitec radio.

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07-19-2002 05:18 AM  16 years agoPost 5
Fuj

rrApprentice

Fairfield, CA

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I'm confused - are you referring to the guides located along the tail boom that are CAd (3 of them)? These are fine - no problem. I'm talking about the two guides built into the side frames. The rear one is okay with the rod thru it - the front one I didn't use - I left the rod outside of it and the rod seems to move around it. Did you file that off? Can you upload a picture?

Thanks,
Dan

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07-19-2002 08:32 AM  16 years agoPost 6
ncostes

rrVeteran

Va, US

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Ok I'm talking about 3 different things.

1. The 3 guides that you CA'd (the ones that slip around the boom).

2. The big guide that's on the side of the frame - that's the one that has some slop - that is the t/r control rod wants to bend out there when you push on it from the front, then it bumps agains the edge of that guide and then it pushes. This is the one you have run your rod through, and that is correct. If you wrap a zip tie through the frame and around the rod at this point, and tighten it slowly, checking what the rod does as you push, you'll get it to the point where the zip tie is acting as an outside guide and working together with the big guide. I'll take a pic tomorrow if this doesn't make sense.

3. The little guide closer to the front of the frame is not used anymore so you're good since you didn't run the rod through it - the rod would not have fit through it.

4. The part I filed is not any of the above. Read this thread

http://www.runryder.com/showtopic.h...static+friction

for info. Look here at the manual...

http://centuryheli.com/manuals/cn10...4/step28_30.gif

Look at the "tail pitch ball links x 2". You see how it looks like an A - and there is the other piece that goes inside the A and then a pin goes through both pieces? The other piece is the problem (the part that is part of the pitch plage). What happens is the piece that goes inside the A "spreads" the A some, and creates a lot of friction there.

You can verify if this is a problem on your heli as follows.

Disconnect the ball link on the tail rotor control servo. Now move the control rod by hand, back and forth, and see how stiff/or slick it is.

Now disconnect both of the tail rotor pitch ball links (the ones that connect the tail rotor blade grips to that A looking tail pitch ball links). Now move the t/r control rod again - if it is much smoother now this is the problem.

The problem is that A ball link being spread by the plastic piece that fits inside there and the pin goes through.

I filed down both sides of the piece that goes inside the A part until it no longer caused it to "spread" then everything was a lot smoother.

If this still doesn't make sense (after reading the link I put up there) post and I'll take pictures.
Nick

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07-27-2002 08:59 AM  16 years agoPost 7
ejs232

rrNovice

Eureka Ca

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tail twitch after crash
I just went through this and I never had a crash. The tail would inconsistantly twitch I thought I might be looking to hard for this twitch except that its still a fairly new bird and I can remember it being rock steady. Check the upper mast stopper that it is pushed against the upper ball bearing and that the upper ball bearing is in good shape, otherwise any slop with a load on it pulls the main gear into the pinion to far and closes the gear mesh. The plastic main gear is fine but not perfect a little wobble in the main gear to close to the pinion will cause a vibration the gyro will pick up. The other thing I wanted to address is the small washer between the pitch slidder mount and pitch slidder arm is very thin if you tighten the bolt to where there is no slop as the arm rotates the the base of the ball on the slidder itself bottoms out on the slidder arm causing it to get tight in one direction of travel. Just add another very thin washer to it and the linkage will work much more smooth.

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07-28-2002 06:13 PM  16 years agoPost 8
Fuj

rrApprentice

Fairfield, CA

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Nick

Can you post pictures of your Hawk IV - specifically in regards to the t/r rod along the right side?

Thanks a bunch - I'll put some of mine up this afternoon.

Dan

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07-28-2002 07:08 PM  16 years agoPost 9
Gearhead

rrMaster

Vt

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maybe it's cut dampers
Dan,,, read my old post,,, my Hawk V2 did this, what I found was the head dampers where cut, the result of a crash !!

Check your dampers !!


Jim


About 4 week ago I greased my Head Dampers with Dielectric Grease, it worked good, or maybe to good !!,,, well, last week I noticed every once and a while I would see my Hawk V2 make a round circle movement (or letter O) with it's nose, and this week it's doing it more !!,,, well, I notice my Head Dampers are cut, so I took them off and what I found was the Dampers are cut where they meet the Head Block opening, the edge on the Head Block is sharp on the inside where the two meet,,, and where the washers meet the Dampers the Dampers have bad ware marks on them,,,,,,,,,, at first I was thinking it was the Dielectric Grease fault , but as I'm writing this I remembered that I did have some ground strikes with the main blades when I crashed, so this must be when I got the cuts in my dampers,,, what do you guys think ?!?!

Jim

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07-28-2002 08:47 PM  16 years agoPost 10
Fuj

rrApprentice

Fairfield, CA

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Jim

Thanks - I'm not too sure what you're talking about but I will take a look and report back. Any chance you can post or email me a picture of what you're talking about.

Thanks!
Dan

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07-28-2002 09:40 PM  16 years agoPost 11
Rotodigger

rrApprentice

Old Orchard Beach, ME ~ Vacation Land!!!

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Just curious...does the tail twitching coinside with the engine changing tone? Check that the engine is running smooth first. A rough running engine will cause the tail to twitch.

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07-28-2002 10:47 PM  16 years agoPost 12
ncostes

rrVeteran

Va, US

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Here are the pics

The part I filed is the inside part that's compressed by the Y arm. This part was spreading the Y arm causing friction.

Below shows where I put a zip tie which is tightened just enough to keep the t/r rod from bowing out just a touch - it acts as an additional guide.

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07-28-2002 11:24 PM  16 years agoPost 13
Gearhead

rrMaster

Vt

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Dampers
Dan,,, the round rubber dampers (or rubber bushings) that the feathering shaft slides in to !,,, part # Hi3181,,, step 1, top of page 4 in the Hawk SE V2 & Falcon V2 manual...

These dampers can get cut on there sides in a crash when the main blades strike something,,, I have had this happen 3 times out of 3 crashes on my hawk

If you need to, Email me so I can get you E address and I will send you a pic !

Jim

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