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Model Forum / Radio Controlled / Helicopters / October 2007What happened here?
http://youtube.com/watch?v=FVmHCqeEVsc I'm guessing too low rotor speed and pulling back upon earth contact, but I'm not sure. Am I seeing a flybar and paddles? Either way, it makes me cringe. But, then again it looks like an electric, so it can't be all that bad. :) marco weir -- willhane A shudder ran down my spine.I remember well the early Hirobo Shuttle.It exploded just the same. > http://youtube.com/watch?v=FVmHCqeEVsc > [quoted text clipped - 4 lines] > > marco Boom strike.... > http://youtube.com/watch?v=FVmHCqeEVsc > [quoted text clipped - 4 lines] > > marco >http://youtube.com/watch?v=FVmHCqeEVsc > >I'm guessing too low rotor speed and pulling back upon earth contact, >but I'm not sure. Am I seeing a flybar and paddles? Either way, it >makes me cringe. But, then again it looks like an electric, so it can't >be all that bad. :) It disintegrated from the strain of staying aloft at such a slow rotor speed...;-) rj > http://youtube.com/watch?v=FVmHCqeEVsc > > I'm guessing too low rotor speed and pulling back upon earth contact, > but I'm not sure. Am I seeing a flybar and paddles? Either way, it > makes me cringe. But, then again it looks like an electric, so it can't > be all that bad. :) I can tell that it is a boomstrike. I guess I didn't state the my question clearly.. I've landed my .30 size helis so hard that I broke both landing struts, on more than one occasion, but I've never had a boom strike. After watching that video, I was wondering if I'm just lucky. ? (knock on wood) marco Obviously, you can't tell from the vid how fast the rotor is spinning. A relatively slow rotor rpm "might" contribute to this. However, my experience with such things makes me think he simply had the rotor blades attachment bolts too loose. If the blades are able to swing too easily, that would cause the very result the video shows. In your case Marco, I guessing you tend to run the blades a bit tighter in the grips which would go a long way toward preventing that kind of boom strike although sometimes, luck plays a part in it too! :-) In that case, be thankful for the free helicopter and continue on! Fly Safe, Steve R. PS: Just FYI for those who don't know, a good test to determine whether the main blades are too loose in the blade grips is to pick the model up by the rotor head and skids and turn it on it's side. "Lightly" bounce it up and down. If the blades fall under their own weight, they're too loose. Just snug them up until they hold. You don't want them locked down which is why I emphasize a "light" bounce. Anyway, do this and you'll reduce you're chances of having the kind of boom strike shown in that vid! FWIW! :-) >> http://youtube.com/watch?v=FVmHCqeEVsc >> [quoted text clipped - 13 lines] > > marco > Obviously, you can't tell from the vid how fast the rotor is spinning. A > relatively slow rotor rpm "might" contribute to this. However, my [quoted text clipped - 15 lines] > down. If the blades fall under their own weight, they're too loose. Just > snug them up until they hold. is that correct for all sized birds?? >> Obviously, you can't tell from the vid how fast the rotor is spinning. A >> relatively slow rotor rpm "might" contribute to this. However, my [quoted text clipped - 17 lines] > > is that correct for all sized birds?? Oooo, good question! It works very well for anything 30 size and larger. As for the micro models like the T-Rex 450 and clones, I've not found it to be an issue. I've owned an MX400 and am currently flying an HDX 450 and on both of those machines, keeping the blades from being "too" tight in the blade grips was more of a problem than them not being tight enough so this has never been an issue for me on the smaller birds. Having said that, the blades need to be loose enough so they can find their natural positioning from centrifugal force. From your point of view, you should be able to move the blades in the blade grips with a fair amount of drag but not being almost locked down. What's a "fair amount of drag?" That's very easy to demonstrate in the real world and really hard to describe here in print. All I can suggest is that you snug them up to a given level and go spool up the rotor system. Everything should swing into place and smooth out by the time the rotor is up to full flight rpm. If it doesn't, you're probably a little too tight. If it smoothes out well before the model is ready to lift off, you might be a little too loose. It's a trial and error thing but you'll get a feel for it over time. Another thing that's important is that both blades be snugged the same amount. One being significantly tighter than the other can introduce vibrations too because the individual blades won't be able to move in lead/lag the same. I've found that if, while checking the blade tightness on the ground, it "feels" pretty close, that's good enough. Hope this makes sense! :-) Fly Safe, Steve R. >>> Obviously, you can't tell from the vid how fast the rotor is spinning. A >>> relatively slow rotor rpm "might" contribute to this. However, my [quoted text clipped - 45 lines] > Fly Safe, > Steve R. It makes sense but I might have them a bit to loose on my T-Rex I will have a play later >is that correct for all sized birds?? Yep, but I always throw my back out holding that damned R44 on it's side while shaking it... > Obviously, you can't tell from the vid how fast the rotor is spinning. A > relatively slow rotor rpm "might" contribute to this. However, my [quoted text clipped - 19 lines] > > FWIW! :-) That makes perfect sense to me. The only reason I guessed at a low rotor speed is because it seems that a hard bounce could also bring the tips down low enough and with enough rear cyclic.. marco >http://youtube.com/watch?v=FVmHCqeEVsc > >I'm guessing too low rotor speed and pulling back upon earth contact, >but I'm not sure. Am I seeing a flybar and paddles? Either way, it >makes me cringe. >But, then again it looks like an electric, so it can't >be all that bad. :) >marco Why do you say that ? A bad electric crash can be more expensive than a glow heli. Ken >> http://youtube.com/watch?v=FVmHCqeEVsc >> [quoted text clipped - 11 lines] > > Ken especially when a battery pack on its own could be £100 $200 and thats on top of the tail boom, blades,shafts ETC >especially when a battery pack on its own could be £100 $200 and thats >on top of the tail boom, blades,shafts ETC $300+ for batteries if you're talking anything .50 sized. >>especially when a battery pack on its own could be £100 $200 and thats >>on top of the tail boom, blades,shafts ETC > > $300+ for batteries if you're talking anything .50 sized. Try pricing batteries for something like an Ion!!! My buddy has a couple of them (Ion's that is) and they take "two" batteries per flight so you can take that $350-$400 per battery and mulitply it by two!! Ouch! Fortunately, he hasn't had to deal with a crash serious enough to require replacement of the batteries. He has puffed a couple of them through the years though. >>http://youtube.com/watch?v=FVmHCqeEVsc >> [quoted text clipped - 9 lines] >Why do you say that ? A bad electric crash can be more >expensive than a glow heli. I have yet to have a good crash, glow or electric. :) >> http://youtube.com/watch?v=FVmHCqeEVsc >> [quoted text clipped - 8 lines] > > Why do you say that ? It was my feeble nudge at starting a flame war between gasser, glow-er, and electric pilots. :) Sarcasm be damned, it's just my subtle way of saying that I don't like electric helis, aside from the little indoor dual rotors.. > A bad electric crash can be more > expensive than a glow heli. Exactly one of the reasons why. :) > Ken marco > http://youtube.com/watch?v=FVmHCqeEVsc > [quoted text clipped - 4 lines] > > marco If you slow it right down - you can see - tail boom strike.  SignatureClive Life is not measured by the number of breaths we take..... but by the moments that take our breath away. >> http://youtube.com/watch?v=FVmHCqeEVsc >> [quoted text clipped - 6 lines] >> >If you slow it right down - you can see - tail boom strike. I think it was more than just a boom strike. I've seen many boom strikes and have had a a lot of them myself ... :-( few but I don't see how it could cause that much damage. I'm pretty sure the main rotor came in contact with the boom. That would explain the violent event that took place. My .02 cents worth, Ken >>> http://youtube.com/watch?v=FVmHCqeEVsc >>> [quoted text clipped - 17 lines] > > Ken If the main rotor is carrying enough power, it'll do a LOT of damage when the main blades make contact. >>> http://youtube.com/watch?v=FVmHCqeEVsc >>> [quoted text clipped - 13 lines] > I'm pretty sure the main rotor came in contact with the > boom. That would explain the violent event that took place. is that not what a boom strike is? when the mains hit the boom > My .02 cents worth, > > Ken Boom Strike A devastating event when a landing is hard enough that the momentum of the rotor blades bends them down to the point that one of them makes contact with the boom. This generally destroys the blade, boom, control wire, and tail drive system. This is also one of the most common events experienced by new pilots who overreacted and pushed the heli into the ground. >Boom Strike > A devastating event when a landing is hard enough It can even happen in flight: http://youtube.com/watch?v=0UkMW2dcNNs SignatureRoRo >> Boom Strike >> A devastating event when a landing is hard enough > > It can even happen in flight: > > http://youtube.com/watch?v=0UkMW2dcNNs ouch >>> Boom Strike >>> A devastating event when a landing is hard enough [quoted text clipped - 3 lines] >> http://youtube.com/watch?v=0UkMW2dcNNs > ouch That's not a totally unheard of problem. Early Raptor 30's were known to do this from time to time and that was without all the aggressive flying that's shown in the vid. The earliest model I remember doing this was the original version of the Hirobo Shuttle. It would do what was affectionately called the "woof and poof" but that was a totally different deal. In the case of the guy in the vid, I think he got a "little" too aggressive with a head that was a "little" too loose. Maybe the blades weren't tight enough in the blade grips or the dampers weren't as stiff as they needed to be or some combination of the two and/or some other factor that I'm not thinking of at the moment. He flew for quite a while without a problem and has probably been flying the bird for a while. You don't get to be that good a 3D pilot without burning some fuel. He just caught something at "just" the right time and there ya go. Fortunately, this isn't a problem for us "normal" pilots! ;-) Fly Safe, Steve R. |
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