munchyman64

Well after spending 4 days straight making sure my trex was setup perfectly i take it to a big open conference room for the first flight. Take 1 goes perfectly, i get it up and hover for a minute and set it back down. When i went up the second time, i was hovering and my tail just randomly spun around so it was suddenly nose in 5 inches off the ground. needless to say, being fairly new, I cut the throttle and it came crashing down. Bent the aluminum tail boom and broke this little plastic piece. I guess the gyro malfunctioned, what do you think? Im pretty sure it was the gyro, and if thats what yall think im gonna try and get my money back and go for the gy401. this is the gyro i was using:

hdoc

Doubt it was the gyro, though the 401 is the 'best'. Better check your ENTIRE tail control set-up carefully re servo binding, connections,Belt, etc etc. Also, it could have been radio interference--Keep the Ant. away from the motor, ESC, and frame.

You learned one important lesson--At least experienced a terribly normal reflex reaction.

NEVER SUDDENLY CUT THE THROTTLE --- NO MATTER WHAT (Unless it's coming after you)

It'll go crashing down!!! Always SLOWLY lower the throttle maintaining "Horizontal" control. When properly set up, it'll come down'slowly' at half throttle or slightly less. Try not to reduce it lower before setting down. IT WORKS!!

I learned on the Blade, and came down like that multitudes of times till I finally learned.

Good Luck

Lloyd

munchyman64

Ive been looking at whats left of the tail and remembering the 4 days of setup before I could fly, I dont think it was servo binding or anything. The thing thats bothering me is that it rotated clockwise, fighting the tendencies of the heli to spin because of rotor torque. The servo i have on the tail must have been workin hard to make the heli spin that fast in that direction.

And also the heli was coming right at me, it was like half a foot away from me when it hit ground. I am going to pretend that was the reason for me cutting the throttle.

H0ndaJunkie

What brand and model of transmitter are you using, and what do you have your current pitch and throttle curves set to?

For my normal flight mode, not idle-up, I have a pitch curve set that keeps the pitch at around 1-2 degrees of negative pitch as the motor spins up, and then the pitch curve climbs after 50% of throttle stick travel. It's a great setup for beginners, because if you get the urge to shut-her-down, the throttle will cut back quickly when you move the stick all the way back, but it won't place your blades into a dangerous amount of negative pitch. Most people only use the normal flight mode, if at all, for take off and landing, but it's a good idea to set it up right for a beginner.

The other day, at my office, my buddy finished up his 450XL and took it for a test flight. He got it about 5 feet off the ground, and then his head began to wobble terribly (he didn't build the head properly). So he yanked back on the throttle stick, cutting his throttle, yet placing a lot of negative pitch on his blades, which drove his heli into the gound and caused a lot of really expensive damage. Setting a pitch curve for the normal setting that is something like 40,45,50,75,100 helps out a great deal.

Also, I disagree that you shouldn't cut the throttle in case of an emergency. I think that if you know you're in trouble, and you're in damger of hitting someone or something, the first thing you should do is shut it down. If you maintain a constant throttle, and hit something with the main blades, the force of a working motor will add to the damage. If you shut it down, it will fall out of the sky pretty hard, but the damage to whatever the heli comes into contact with will be minimized. Just my opinion.

hdoc

Not sure I fully understood what you had said, though the Throttle cut issue is critically important.

You mentioned the craft "randomly" spun around--Meaning exactly what? Did it slowly rotate one way or the other, or 'FAST"-- Did you have Rudder control - or even use it. Until the gyro is properly calibrated in HH mode, you still have to control the tail. Once properly "Set-up", and that often takes a few brief flights, it'll hold with essentially "0" rudder stick. Were the tail blades at essentially neutral pitch (as a start) with the tail servo at neutral pitch? Was the servo throw adequate?.....Lot's of questiins. Have you set up heli's before? If not, suggest you get help from an expert or your LHS... Does take time to get it right, but when you do, it's great. Check the last 10-15 posts on the "Trex 450 SE or MX400 " thread. And any "Tail problem" threads as well

Lloyd

hdoc

By the way - as an addition. Strictly follow the Trex set-up instructions if you are a novice. For the normal curve they suggest "0" pitch at "0" throttle around 6 degrees at 50% .. etc. At least this way the momentum of the blades will help maintain some lift until you're at "o" Throttle, rather than "NEG" pitch which will "Push it down fast. And if it was coming at you, the forward pitch setting was off as well. Realistically, if you follow their set-up exactly, then several brief TO's & landings (1-2") from the ground, will allow you to see the tendencies & correct them immediately. Then you can 'trim' out minor abberations with Xmitter trim. Give yourself plenty of room to fly. I spent 2 Mos with a Blade in my garage and after multitudes of crashes, finally learned comfortable hovering. Have been flying the Trex past 2 weeks--mostly in the same 16X75X7 garage and must say that from day 1 it's been great in all respects--Totally stable and a pleasure to fly. Outside it's even more enjoyable. I'm sure you'll be there soon

Lloyd.

munchyman64

I spent days making sure my heli was set up right, and I had a little experience setting up a bcp for different conditions. The tail servo had plenty of travel and the gyro was initialized and it was working for the first parts of the maiden voyage. Then all of a sudden it spun very fast. It was only like 5-10 inches off the ground by the time it was coming my way so I cut the throttle and it fell and tipped over. As soon as the heli started to spin I tried to correct with rudder control but it was coming around fast. I set up the pitch so it was 0 at 0 throttle and it went up linearly all the way to bout 10 degrees.

munchyman64

I need yalls input, I need to decide whether to get a new gyro.

H0ndaJunkie

It just sounds like either a mis-configuration problem or a radio glitch.......I'm not sure that you need to throw out your Gyro just yet.

I have a telebee gyro on one of my TRexs, a GY401 on the other, and a GY401 on my Raptor 60. The Telebee is exactly like the one you have. While it's nowhere near as good as the Futaba, it's not a bad little gyro, once it's configured correctly. However, if you have the money, I would definitely grab a GY401 if you can.

munchyman64

Im just wondering if the gyro might be malfunctioning. Do things like this happen often? I know it was set up correctly because of the checking and rechecking and when I took it to my lhs and had them check it.

H0ndaJunkie

Because those Gyros are solid state electronics, I would say that a malfunction is a rare thing.......others here could probably tell you better than I can on that one. Are you sure that it couldn't have been just regular radio interference?

munchyman64

i guess it could have been radio interference, I just can't think of what in the sticks here would interfere at that frequency range. Maybe it was just a glitch. I really don't want to buy a new gyro I just wanted to make sure it wasn't a gyro problem, and the general consensus seems to be that it was not a gyro problem.

H0ndaJunkie

I don't know.....you can't really rule out anything without more tests.

I've got a little trick I use when I want to check the configuration of my gyro. I bought a Duratrax Pit Stand for an RC car from the local hobby shop. It's a swivel stand, normally used for working on RC cars, but it's great for testing gyro action. I sit the heli on the platform, and place a small piece of wood across both skids and clamp it down to the platform. I can then spool up the motor, and rotate the heli to my hearts content. Seems to work quite well actually.

Outside of that, if you test fly the heli again, but only keep it a few inches of the ground, you might be able to identify the issue if it occurs again. I think you just need to play with it some more, close to the ground to see what happens.

Airotica

Sounds like what my SE did on the first flights, well if you can call 10mm height a flight. I had never flown before but very quickly realized that the gyro was the cause. I had to switch it to reverse

I'm sure you checked this but mine actually hovered for a bit and then it started turning a little clockwise. The backward gyro threw it into a clockwise spin real quick.

bebopin64

My Feedback: (2)

this is munchyman64 on his original sn. I got some replacement parts to fix it and the SE CF frame for better control. Im going to try it out again with different antenea (spelling?) placement.

clive45

If you go to the RUNRIDER forum you will find videos on just about all the setup you need. Also goto trextuning.com lots of info.

clive45

Should have been RUNRYDER.com

Biscuit

I had the same problem with my first T Rex with that same gyro, it would let me fly for a few mins then lock the tail full right, everbody said the same things they have said to you, so kept with it till the last crash when it went in flat out in idle up 2! tried a cheap GWS PG 03 and it was fine, now run a CSM 420 micro on my SE, no problem, just bin that Gyro, wish I had seen this post before, might saved you some time and money.

bdavison

My Feedback: (1)

Make sure you have REVO mixing disabled on your radio. If its enabled and you fly it in HH mode...everytime you bump a little throttle in it...it will spin like mad.

RickP

My Feedback: (2)

sounds like the gyro was revesed. Guess you got lucky on the first hover and didn't need any gyro input....
RP

rcflyerdave

I had my forward alum pully gear for the belt slip on the shaft and caused piroetting.You can test it by holding the tail rotor and trying to turn the main hub.Mine would slip!I have ordered the aftermarket one with the set screw.This was the pulley that was on the blue gear change ratio assemblies. Dave

H0ndaJunkie

There's no way that his gyro is reversed. The fact that he was actually hovering for a few seconds before his heli did the piro thing, tells me that his gyro is not reversed. I've never got a heli off the ground before, if the gyro was reversed.......it usually starts spinning immediately.