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Model Forum / Radio Controlled / Helicopters / June 2004Glitch Gremlin
My beloved old Shuttle ZX is being a pain. About 7 months ago I had it in a low hover when it suddenly went able sugar and thrashed itself to death on the runway. I had no control what so ever. The damage wasn't as bad as it could've been although I lost a new set of nice NHP Razors. I made the necessary repairs to the airframe but due to other pressing obliga- tions I had to shelve my R/C activities until a few weeks ago. I decided to go ahead and replace every electronic component in the Shuttle including all servos, gyro, switch, battery and receiver. I made the first flight a couple weeks ago and all was well. It flew just fine last weekend but yesterday the glitch gremlin came back. It twitched 3 times but at least this time I managed to get in back on the ground without damage. This machine is about 10 years old and I estimate that I've put about 600 flights on it. I do try to take good care of it and repair or replace components before they fail. I did replace the tail rotor, main shaft ball bearings and that special "auto rotation" bearing about 2 years ago, as well as all of the bearings in the clutch area. As to spinning bearings, I guess that leaves the swash plate and tail rotor belt idler. Other than the bearings, I'm not aware of any metal to metal joints that might cause trouble. Everything is well secured. The only other thing I can think of is the small chance of outside interference. I've pretty much ruled that factor out because I've been flying my pattern ship on the same channel with the same transmitter and it's solid as a rock. I fly this aircraft as often as the Shuttle and at the same flying site. Any thoughts? Should I just go ahead and replace every single ball bearing in the ship? Dave Dave, Try a new set of crystals first, if they are the same ones (esp RX end) that were in the crash it might have fractured also check for binding in linkages anywhere which could be stalling a servo and dragging the supply voltage down to unusable levels. Also as you have fitted a brand new rx battery pack, cycle it a few times to make certain it does not have any duff cells and is producing its best voltage. Nimh cells are notorious for not giving full voltage/capacity for the first couple of cycles or failing early in life. I have seen two new NiMH packs with dead/dying cells in the last 6 months that were initially put down as radio interference. Chris > Dave, > > Try a new set of crystals first, if they are the same ones (esp RX end) that > were in the crash it might have fractured also check for binding in linkages > anywhere which could be stalling a servo and dragging the supply voltage > down to unusable levels. Excellent points. The receiver did come with a new crystal, so I guess that rules that out. I've looked for binding, etc., but everything seems to be ok. I've monitored the on-board VoltWatch and see no dip in voltage as controls are moved about. Also as you have fitted a brand new rx battery > pack, cycle it a few times to make certain it does not have any duff cells > and is producing its best voltage. Nimh cells are notorious for not giving > full voltage/capacity for the first couple of cycles or failing early in > life. I have seen two new NiMH packs with dead/dying cells in the last 6 > months that were initially put down as radio interference. I built up the new rx pack with 4 new Sanyo KR-1500 nicads and then cycled them with my AccuCycle several times before commiting to flight. Capacity seems good. All connecting wires and plugs are also new. I suppose there could be an intermittant bad cell, but the glitches are so consistant with what happened with the old flight system and battery pack that I'm left wondering what's left to replace on/in the helicopter. Maybe something metal-to-metal I haven't yet discovered or a noisy ball bearing... maybe I should just buy a new heli :-) Thanks for your reply! Dave > dstaffor[SpamNot]" <"dstaffor[SpamNot]"@calpoly.edu> wrote in message news:cbpi20$4eu$1@cscnews.csc.calpoly.edu... > > Dave, > > [quoted text clipped - 33 lines] > > Dave OK not much left then apart from belt static such as affects some other helis, try earthing the boom to the engine mount somewhere. This is usually only a problem on electric heli's but has been known to affect glow ones as well. You could also try spraying some silicone spray on the belt and pulleys to see if that cuts down on static that's a quick thing to try before drilling holes in the boom to mount an earth wire. Was the glitch accompanied by a change in the engine note? if so it might be worthwhile flushing the carb and tank out incase there is any debris inside causing a brief lean burst and accompanying brief increase in power. Chris Something else worth trying if possible is change the RX. Futaba Dual conversion RX's had a problem with a ceramic filter getting damaged in a bump. The RX would appear to work but would glitch in the manner that you describe. > > dstaffor[SpamNot]" <"dstaffor[SpamNot]"@calpoly.edu> wrote in message > news:cbpi20$4eu$1@cscnews.csc.calpoly.edu... [quoted text clipped - 57 lines] > Checked by AVG anti-virus system (http://www.grisoft.com). > Version: 6.0.712 / Virus Database: 468 - Release Date: 27/06/2004 |
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