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HelicopterMain Discussion › How to avoid boomstrike during chaos?
06-01-2004 06:36 PM  13 years agoPost 1
Andreas

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Sweden

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Hi.
Last weekend i was out and tried to learn chaos. I've been working on it for a while and it sure gets better and better. Anyway, suddendly while doing the chaos i heard a smack from the heli. I landed it and could see that the blades had hit the boom. I had a lot of luck because the blades were still fine and i could land the heli without problem.
The heli is a Raptor 90 and i'm running 700mm Razor blades and Rick's o-ring upgrade with a hard o-ring inner, one soft outer and 5 shims on each side.
I run 1800rpm and the blades really really tight.
So, my question is...how can i avoid this to happen again?
Maybe it's my flying style that need some changes?
By the way, i have +-10 degrees pitch.

Greatful for some help here.

Cheers Andreas

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06-01-2004 07:05 PM  13 years agoPost 2
blakka_1

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London/Enfield

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its all timing dude, you have to get your collective and cyclic timing right, too much collective and too much cyclic and your blades will hit the boom.

boomstrikes during chaos can be avoided by

- harder dampers
- higher headspeed
- a well setup engine ( less chance of bog )
- stiffer blades
- blades tight in blade grips
-govenor
-A HELI WITH A STIFF HEAD

you say your running the nhp razor pro's, these blades are pretty stiff so i dont think that was your problem. you also mentioned a 1800 headspeed, that is pretty good, so thats not your problem either. the raptor head is pretty stiff too so thats not your problem. I think it may be a timing issue, try applying collective and cylic movements more smoothly while doing a choas, otherwise its referred to as stick banging, stick banging will boom strike any heli.

main point here dude is - apply collective and cyclic smoother while doing chaos, also try using less collective during choas, i have found that using less collective during choas puts less strain on the heli, but also makes the choas look better.

hope this helps dude

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06-01-2004 07:20 PM  13 years agoPost 3
staraero1

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Atlantic City, New Jersey

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Which helicopter? Was it a Raptor 90?

Staraero1

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06-01-2004 07:23 PM  13 years agoPost 4
blakka_1

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London/Enfield

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The heli is a Raptor 90

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06-01-2004 07:32 PM  13 years agoPost 5
w.pasman

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Netherlands

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Is that 1800 RPM during (while you are doing) the chaos ? Note that it can drop very quickly if you make a sudden extreme cyclic/pitch movement. I can bog down my engine within half a second, and you may not even see anything special happen to the heli !
The only reliable method I konw to detect this is to hear it from the engine tone. I'm pretty sure that even that an optical tach can not be operated quick enough to follow sudden rpm drops.

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06-01-2004 07:55 PM  13 years agoPost 6
Andreas

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Sweden

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Thanks for the replies.
I also run a complete TDG head on my heli so i guess the head must be stiff enough.
I can hear my engine bog a little when i do the manouvre. I use the OS91 C Spec PS and a GV-1 (just to get you some more inputs).
Have anyone tried to run two hard o-rings instead of one soft and one hard?
Blakka: I also think it's a timing issue and that i just have to be smother with the collective/cyclic. The issue is what i'm gonna do to dare trying chaos again after this near to death experience

Cheers Andreas

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06-01-2004 08:00 PM  13 years agoPost 7
blakka_1

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London/Enfield

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dont worry dude, i doubt very much that it will happen again, now that you know it can boomstrike during chaos, you will be more carefull next time. you can only improve, i guarantee you that the next time you try a choas it will be the best one you have ever done, due the fact that your more carefull. more carefull = smoother

get back to choas!!!

good luck dude

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06-01-2004 08:16 PM  13 years agoPost 8
Andreas

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Sweden

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Blakka: Yeah i guess you're right. I'll try it again but try to be a little bit smoother. Maybe use idle up 1 as a chaos flight mode with +-7 degrees pitch and 5 degrees cyclic?

Adrian Law: I use the o-ring upgrade from Ricks. I used the TDG dampers before but i could not get the o-rings to last more than about 15 flights??
No i don't use the TT flybar carrier. Everything above the swashplate is from TDG. I use Freya paddles without weights.

Cheers Andreas

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06-01-2004 09:26 PM  13 years agoPost 9
staraero1

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Atlantic City, New Jersey

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I missed it was a Raptor 90. Did you do the head mixing change on the walking beams in the head by moving them closer into the center towards the head block? If not, it will boom strike here and there if the RPM's fall off, even just a little during the move. If you don't have the mixing change done I suggest you do it. Here is a picture of one that has been done with the exisiting stock head parts.

http://www.rotory.com/ubbthreads/sh...sb=5&o=&fpart=1


This involves moving the walking beam mixers themselves in closer to the head block, as I call them. They almost hit the head block on the pivot on both sides. You take the flybar out, then drill straight through the metal that has the flybar bearings in it. You need to get the mixer pivots closer to the head block. Then you cut the ends of the plastic mixers down, and move the ball links in closer on the long side of the arm like the picture shows. You have to sand the arms a little on the sides to clear everything so they can still move freely for their full travel once moved closer in.

If you use the extended flybar cage arrangement, this actually lets you do this mixing change without any hoop interference with the pivot screws. But the walking beams still need to be moved as close to the head block as clearence will allow. The cage completely removes any hoop binding on the flybar pivot screws. The stock change will work however. Even though the hoops can contact the pivot screws with a stock mod, we have never had a problem with the hoops in flight touching the screws, pulling them off the balls, or wearing them down. The new Raptor 90 SE will incorporate this change to it's head from the factory, as word has it.

With the mixing change you might want to incorporate a tighter damper spindle preload. With the mixing mod done, and the damper grip spindle load tighter, you can still get a boom strike with the Raptor 60 or 90. But for it to happen when these things are done you have to drag the rotor down quite a bit before it happens to you again. Also, a lot of the Raptor wobble you have probably seen in hard manuvers will be gone now, once the change is made to the head mixing. When the rotor drags down a little in very hard moves. Once you do the mixing change, you will see and feel the difference instantly. With the head mod and a tight elevator servo and linkage, almost all the nose pitch up the Raptor 60 and 90 has, in fast forward flight, will be gone as well.

Only Raptors, or what ever the name of that new parts company is, has the parts needed to do the mixing mod new in the package. With the changes already made to them. They bolt right in place of the old parts, as I hear it now. We did all of our mixing changes by hand. If you already have the head mixing change done, increase the damper grip preload a little, and the trouble should pretty much go away. To my knowledge, and by trial and error, once these things are done to the Raptor 60 or 90 head, the only way to get a boom tick is hard climbing forward flips. Assuming the rotor speed stays fairly constant during the manuvers.

Staraero1

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06-02-2004 07:04 PM  13 years agoPost 10
Andreas

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Sweden

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Thanks for great replies.
I think i'll give the head mixing change a try.
Staraero1:
Where on onlyraptor's site can i find the kit to make this?
I've been searching but not find it.

Cheers Andreas

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06-02-2004 07:30 PM  13 years agoPost 11
blakka_1

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London/Enfield

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get those carbon extreme dampers !!!!

i will be ordering some for my 50 as soon as they arrive in england ( should be soon )

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06-02-2004 07:34 PM  13 years agoPost 12
Andreas

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Sweden

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It would be great to try them out.
Does anyone know where i can buy them then?
Thanks alot!

Cheers Andreas

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06-02-2004 07:38 PM  13 years agoPost 13
Andreas

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Sweden

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Just sent a pm to Rappy Tappy, hope he can help me out with the dampers.

Cheers Andreas

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HelicopterMain Discussion › How to avoid boomstrike during chaos?
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