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02-13-2012, 04:22 PM | #21 (permalink) |
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Join Date: Apr 2011
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I want to know who sets up a heli such that radio input can cause a boom strike? Seems pretty odd to me, do you have the same issue if you use full cyclic?
No one else has reported any failure mode for a DX8 (or any TX afaik) that will result in servos ending up in positions they cannot reach under normal use.
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02-13-2012, 04:31 PM | #22 (permalink) |
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well i know for fact that my fail safes are set up to idle throttle, and -2 degrees pitch. also that the motor and engines did shut off during all this because a boom strike would normally cause the gears to strip. so mine and two others theories is that the TX told the heli to shut motor off, and overrode my EPA settings and just jammed the swash. those servos are capable of pushing it to jamming, just not with my settings in the TX.
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02-13-2012, 05:42 PM | #23 (permalink) |
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My DX8 told my toaster oven to shut off, but thankfully the toaster oven didn't listen and cooked my toaster strudel just right this morning!
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Bill Rainey AMA 16192 Huntsville, AL T-Rex 600N Pro, miniTitan E360 |
02-13-2012, 08:51 PM | #24 (permalink) |
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I dont buy it, too many different failures have to have occurred to get that result, just too unlikely you have the TX deciding to kill throttle, ignore you endpoints and behave as if full cyclic was used. I can see one of those happening but not all 3 at once (especially since no one else has reported either of the last 2). If it actually was the TX then this is certainly the only time I have heard of something even close to this.
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-DX8 -MSH MiniProtos Stretched, SK720, DS95/DS95i, Hyp 4S 25C 2500mAh -MSH Protos Stretched, Brain, Hyp DS16/BLS251, 6S 3000mAh -Goblin 500, HC3SX, Hyp DH16/MKS980BL, Scorp 4015-1100 |
02-13-2012, 09:01 PM | #25 (permalink) |
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So if you dint think it's the TX, what explains a 250 going crazy, and two 600 size helis having booms strikes in a hover, no input added, with the throttle being killed?
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02-14-2012, 08:06 PM | #26 (permalink) |
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Most Spektrum Rx's have a failsafe only on the throttle channel, all others would hold the last commanded position in the event of signal loss. For those Rx's that do have programmable failsafe for all channels, binding an Rx and then performing a setup without re-binding afterwards could result in the failsafe being set with different endpoints than you intended. Power failure is a different story entirely.
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02-16-2012, 04:21 PM | #27 (permalink) |
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callouscade,
when you say your 250 "went crazy," did you notice a fluctuation in throttle/pitch? if you did, i would check your leads, especially the motor to esc. I remember the first time my 450 "went crazy" and crashed. I was using airtronics 2.4 system at the time. I thought it was my radio, at first. Then after switching to the spektrum dx7, my heli "went crazy" again. It was less crazy, but no crash. I replaced the motor and esc and no more problems. Recently, I was playing with my plane and noticed my throttle would cut at high rpms. I thought it was my DX8 glitching just after receiving it from service. After doing other tests, I thought it was my esc. After even more testing, I figured out that the problem had to do with the bullet connectors. Vibration from the plane caused the bullet connectors to, somehow, cut the current intermittently. Now that I think about it, it was probably the same thing happening to my 450. Now, the motor in my plane is soldered to the esc and no more problems. Needless to say, I'm not a big fan of bullet connectors. |
02-16-2012, 04:30 PM | #28 (permalink) |
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My ESC and motor are workingfine I just fixed that problem recently. It was more of an aileron issue when it "went crazy" it just tilted itself sideways.
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02-16-2012, 04:39 PM | #29 (permalink) | |
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Join Date: Nov 2008
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Quote:
are you using the dsmx or dsm2 rx? might sound rediculous, but I wouldn't use a dsm2 rx with anything more than a indoor/slow/park flyer airplane. |
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02-16-2012, 04:42 PM | #30 (permalink) |
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They were all DSM2 receivers. The receivers all flew on previous birds for months... nothing makes sense! can't wait to hear back from spektrum, sent them the TX and all three RX's.
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02-17-2012, 04:06 PM | #32 (permalink) |
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So am I, I hope they say they found something wrong with my TX, or I have some serious issues on my hands. To test out the receivers and TX i'm putting them all on the trex 250, doing 20 flights each RX, and seeing if anything glitches.
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02-17-2012, 04:16 PM | #33 (permalink) |
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please keep us updated. maybe they will replace your rxs to dsmx.
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02-17-2012, 04:20 PM | #34 (permalink) |
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Join Date: Oct 2010
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I'm just thinking here:
If the tx gave command to run the servoes to extremes, i would expect the heli to take off in one direction before the boomstrike. I can't see how you would get a boomstrike without running the pitch in maximum + or - and having more than max cyclic at the same time. The rotorblades are spinning at 1800-2500 rpm. A swashplate run to extreme angle would affect posision of both blades. The servoes may be fast, but there are a great deal of lift generated from those rotorblades. A hardware failure on the other hand would be instant. As a sidenote, i have used my dx8 since september 2010 without a single glitch. I just sent it in for service, and got a dx6i as a "loaner" while i await my trusty dx8 to return. First flight with my 600efl on the dx6i radio my servoes freezes on a tic--toc and my heli tumbles to the ground. Now it is easy to blame the radio, but vbar log shows sudden power loss. I too am running the align 2 in 1. The device is still working after the crash, but i wont trust it anymore. EDIT: Also there is a service bulletin out on tx8 for a while ago, regarding hold issue on some recivers in dsm2 mode. Also an cheaper way to check may be to buy a "simstick". Then you can check for glitches with the rx using a simulator instead of a expensive heli.
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02-18-2012, 12:29 PM | #35 (permalink) |
Join Date: Jul 2010
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this sounds a little odd to me also. I have had my dx8 now for about almost 2 years, and I have never had a problem with it ever. I also did have one of the recalled ones, in which hh literally sent me a new one and i sent my old one back. even with the recalled one, I never had a single issue ever. In the above post if your swash is moving that extreme it is going to cause the heli to do something other then just hover and boom strike. the only time i have ever boom struck ever is when I landed way to hard, and bounced the blades off the tail boom. interesting.
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02-25-2012, 08:44 AM | #36 (permalink) |
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Horizon said they found nothing wrong with my DX8 or any of the three receivers... however they did replace the gimbals and recalibrate it.... the only other thing could really be signal loss+sucky fail safe or interference becasue the motors quit (into their 'signal loss' or failsafe position). I was flying right next to a school, and both times the school's resource officer was leaving, and I know that 2.4ghz primary use is police/military comunications, not RC... I'm just stumped. doing a bunch of testing on the 250 before I go and fly the big birds again.
thanks everyone for your feedback |
02-25-2012, 12:40 PM | #37 (permalink) |
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About the only way I know of that you can have a boomstrike without losing a link is when for whatever reason the blades turn in the grips.There could be a number of reasons this can happen.If the motor slows down and your headspeed is low you will be adding a bunch of collective trying to keep it up.Then the motor comes back on and the pitch and throttle are high.The torque of the motor accelerates the headblock faster than the blades can keep up with and the blades turn inside the grip.Try it in hold on the bench.See what the blades do? On top of the fact that the blades are no longer sticking straight out of the head and they are sagging now the air is not flowing over the blade completely perpendicular to the airflow and you lose lift.You try to put even more collective in to keep it from sinking and whammo.This all happens in a split second.
Without the motor actually having a momentary failure I tend to think the same scenario would be possible if you get your pitch curve ahead of the throttle curve.Put pitch in faster than the motor can accelerate the blades themselves and the centrifugal force is low enough to not keep the blades pulling themselves straight in the grips.The headblock acceleraes faster than the blades and they turn in the grips. I had this happen once bailing out of an auto with a 450.Coming down I got to about 15ft and realized as I was putting pitch back in that I had no energy in the head.Flipped throttle hold off with the stick almost all the way up and the heli exploded pretty much instantly when the motor came on. Im sure there are other scenarios as well.Also other physics acting on the system to aggravate this action. Not saying this is what happened to you.Just saying that there are other reasonable explanations.
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02-25-2012, 01:54 PM | #38 (permalink) |
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That could be it.... I doubt it though because of the governor and how insanely tight I keep my blades. I can't fold them from the root with my wrist, gotta go all the way to the end of the blade, just for 3D so I DON'T have boom strikes!
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02-26-2012, 10:35 AM | #39 (permalink) |
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The way I kind of confirmed this was to put a non busted blade into the grip before I tore it down and lined up the strike mark on the boom with the blade.It was pretty obvious that it hit forward of the little horizontal stab at a pretty good angle.I deduced the only way that could happen was if the blade was turned in the grip and a bunch of positive pitch was present letting it swing down into the boom.I had the same kind of scenario from simply landing very hard.Its pretty obvious there are some tremendous forces at work in a spinning head assembly.
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Too many helis & Too many planks Lots of DX radios & A couple Futaba 72mhz radios AMA member & Full scale plank driver HELIFREAK !!! |
02-26-2012, 01:27 PM | #40 (permalink) |
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With my DX8 the motor starts at about 20% throttle (using 0-50-100 curve) and same thing with the sim, about 30%. The throttle endpoints are calibrated according to CC procedure and calibrated in the sim case too, is this normal?
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