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Trex control issue

Old 03-11-2006, 09:31 PM
  #1  
larryk9
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Default Trex control issue

Recently I bought a 450 XL CCPM and just finished building and setting it up. I took it out to hover it and
see how the trim etc is setup and as soon as I got it in the air it was like
I had almost no control of it. I set up the ccpm settings on my DX6 Tx this
way: ccp2 45% ccp3 45% ccp6 55%, but I didn't have enough throw. I was
cranking full left right fore aft cyclic and it was barely enough to make
the heli do anything. I barely managed to land it on the ground without
breaking anything except a skid on one side due to a very hard landing. So I
took it home glued the skid back on and went out to the end of our
cul-de-sac here. I added more % to the ccp control. This time I had more
control of it, but still didn't like the way it handled. It was very twitchy
and it wouldn't respond to my inputs until I was at the end of the stick
throw. Then when it finally responded it was very quick to do what it should
have done when I initially made the move. Also the swash doesn't
center/level perfectly after I let off the right stick. When this happens
the servo's just hum because there is still load on them. I am thinking of
buying some new servos, but the thing should fly fine with the servos I have
which are s-75 servos that came with my DX6 Tx. Another thing I was
thinking that may be the cause of the centering issue could be the fact that
all the ball joints are still a bit stiff. At neutral all the servos are
centerd and the swash is level. Any opinions on the issue?
Old 03-12-2006, 12:56 PM
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H0ndaJunkie
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Default RE: Trex control issue

Jeeze, First of all, to help those ball links out a little, I would take a pair of piers and give them a squeeze while they are on the ball.......that helps to seat them against the ball, and can loosen them up a little.

You say that your swash is level, when everything is centered. What I always do when testing the electronics is to either un-plug the motor, or disconnect the speed controller and connect a battery pack to the same channel, in it's place. That way I can mess with the electronics, without worrying about the motor firing up. Try moving all of your sticks around, and observe what happens. You should be able to easily see if one servo is binding etc.

Also, do you have Expo, or dual rates set up on your controller? If dual rates are set, and the controller is in the lower rate mode, you could be only using a percentage of your full servo travel. If your Expo is on, and set to high, it could also give the effect you mentioned. Expo dumbs-down the stick sensitivity around the center point, but doesn't effect the stick at full travel. If your expo is set to high, you would feel like your sticks weren't doing much until they are at their futhest from center.
Old 03-12-2006, 03:41 PM
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larryk9
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Default RE: Trex control issue

Thanks for the reply. I will try loosening up the ball links with pliers. After I re adjusted the ccp % I have a lot of swash plate travel and it was responding better just not smoothly. It was still really hard to control. Granted I have only been flying for a couple months, but my Dragonfly 36 felt so much better when it was setup properly. As far as exponential trim I don't have any of that dialed in. I like the heli to respond with very little stick movement so keeping the right stick movement tight.
Old 03-12-2006, 04:18 PM
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catfight
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Default RE: Trex control issue

larry,

Do you have access to a tachometer? The more headspeed the better control and also easier to fly. Have you tried idle-up yet? I have the DX6 also (but now have superframe v2 so a little different settings) but I had CCPM all 3 set to 60% just as a starting point. I would check the headspeed though- usually the problem is shown by that. When first building a trex the rotor sound can be down right scary :0) so most people set them up too slow.

Good luck!
Old 03-12-2006, 04:29 PM
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larryk9
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Default RE: Trex control issue

I don't have access to a tach and I haven't tried an idle up setting on the Trex yet. I have only hovered it up to about 10 feet so far. What sort of pitch and throttle curves are you using for normal flight? My throttle curve is like this: Thl 0% Th2 70% thh 100% and my pitch is something like this pl 20%(-2*) p2 55%(+4*) and ph 88%(+9*) I am using the 430L motor and 35A esc and the 325mm fiber blades.

Larry
Old 03-12-2006, 06:07 PM
  #6  
catfight
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Default RE: Trex control issue

Mine are set to PL 60 P2 80 PH 100 and TL 0 T2 50 TH 100 but I don't usually fly in normal mode because of the wind at the beach here! Just crashed mine though...sun got in my eyes - sheared the rotor head off, blades OK (amazing- just a slight ding)! cracked flybar cage and tail fin. Total repair cost will be about $20! Amazing heli :0) I have never used fiber blades- do you mean carbon fiber or the ones with foil on them? I use 325 pro woodies.
Old 03-12-2006, 06:27 PM
  #7  
larryk9
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Default RE: Trex control issue

Ok thanks Catfight,

I just finished squeezing all the ball links with pliers and that really loosened everthing up nicely. The swash now levels itself when the sticks are at neutral and there is no more servo hum. Sucks about your crash, but sweet $20 will fix it! THat is one reason I decided on the Trex, cheap and easy to get parts. So I am assuming that you take off in normal mode right? Then hit the idle up just after take off? Do you have it set so you have to be pretty quick dropping the collective when you flip the switch or is your stick position for both modes the same for a hover? I only flew idle up once on my Dragonfly 36 and when I flipped the switch it really climbed in a hurry. Just trying to get an idea of the realationship between the curves in idle up and normal modes as I am still fairly new to this game.

Old 03-12-2006, 06:46 PM
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catfight
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Default RE: Trex control issue

Larry,

I use Throttle Hold (really good practice to get into) and just release it while in idleup- not a problem. I have a Quark ESC with smooth spoolup. The only time I would use normal is if I got into trouble (like low battery or something) and to kill the engine smoothly. Normally just work in idleup with Throttle hold. This is a skill that is really needed I think- I had to unlearn some bad habits before getting here :0)
Setting I use for idleup are PL 0 P2S 50 PHS 100 TLS 100 T2S 80 (sometimes use 90 here) and of couse high is 100.

Old 03-12-2006, 09:08 PM
  #9  
docjoe
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Default RE: Trex control issue

Larry,

I bought the Dx6 for my T-Rex SE and had originally installed the S75s but these servos aren't fast enough nor do they have enough torque. That may explain your problem with the responsiveness to your T-Rex. Also, I didn't change anything to the default settings for CPPM and stayed at 60 for all 3 servos on the cyclic. This seems to have worked well for me so far.

I upgraded my servos to HS65s which were about 25 bucks each. But they are definitely worth it. Also, I bought the 9650 digital servo for the GY401 gyro. This setup is extremely stable for me and I can almost hover without touching the controls. I would recommend getting better servos for the cyclic. My Blade CP runs on the S75s and that machine is a much more difficult heli to control as opposed to my T-Rex.

I hope that helps.

Joe
Old 03-12-2006, 10:58 PM
  #10  
larryk9
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Default RE: Trex control issue

Thanks Joe,

I did take it out today and tested it after I loosened up all the ball links. That made a huge difference and it felt a lot better. Not perfect yet though. I can see how better servos would improve flight characteristics. Especially on the tail becasue it is slow to catch up with rotor tourque when it is applied and it rotates a fair bit when I increase tourque. I only have the gy240 and as I understand a digital servo won't work with it.
On a completely different issue. Nearing the end of my battery today I hammered the throttle to full for a second to see how well it would climb and it got up to about 40 ft or so and the motor shut right down and it came falling out of the sky. it landed on the asphalt and both skids broke off and that was it, no other damage. I unplugged the battery and spun it up (in hand) when I got home and everything worked fine. What could have caused this? I am guessing the esc shut down for some reason.
I was using my 1800mah 10c lipo and it was getting close to dying, but the esc hadn't slowed it down yet or at least I don't think it had. Any ideas?

Larry
Old 03-13-2006, 12:32 AM
  #11  
jh4db536
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Default RE: Trex control issue

the trex is a 20-35amp machine and your battery only allows 18amps to flow out of it...that's why it shut off. a max pitch climbout is probably the most energy consuming move you can make. that amount of current draw probably pulled your voltage under LVC or hit the current limiter.

i think you need to upgrade your equipment before you total the heli. a great heli like the trex is only as good as the worst component that you put on it.

BTW, what pinion are you running??

low headspeed will sap control and responsiveness

honestly i think your problem(s) are:

#1 the battery. 10c is not adequate esp for that 430L motor. that is a hot motor. u probably need 2200mAH 12c-15c at least.
reason-
even if youre using the correct pinion 11 or 13t (assuming you are), that low C rating is probably sapping headspeed (voltage drop) and causing cut outs. Not safe for the heli's sake or your wallet. probably contributes to poor response.
solution-
apex 2200 15c. probably the best & best bang for the buck lipo you can buy

#2 get rid of those s75's.
reason-
they might work on a little BCP, but a trex is like 50% bigger. and we know just how "adequate" they are on the BCP HehE....save them for a slowstick.
solution-
someone mentioned HS65's for the cyclic, that would be a wise move. buy a nice gy240 only to use a poor tail servo? the gy240 is capable with the right setup. if you want a cheap but GOOD tail servo try the hitec hs81. it's bigger than your average submicro, but it gets the job done and it's cheap and easy to get.
Old 03-13-2006, 02:08 AM
  #12  
larryk9
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Default RE: Trex control issue

Hi I am runnning a 13 t pinion and I do have a THunderpower 2100 pro light as well. I just ordered a hitec hs56 servo for the tail and will probably upgrade the rest when my wallet allows.


ORIGINAL: jh4db536

the trex is a 20-35amp machine and your battery only allows 18amps to flow out of it...that's why it shut off. a max pitch climbout is probably the most energy consuming move you can make. that amount of current draw probably pulled your voltage under LVC or hit the current limiter.

i think you need to upgrade your equipment before you total the heli. a great heli like the trex is only as good as the worst component that you put on it.

BTW, what pinion are you running??

low headspeed will sap control and responsiveness

honestly i think your problem(s) are:

#1 the battery. 10c is not adequate esp for that 430L motor. that is a hot motor. u probably need 2200mAH 12c-15c at least.
reason-
even if youre using the correct pinion 11 or 13t (assuming you are), that low C rating is probably sapping headspeed (voltage drop) and causing cut outs. Not safe for the heli's sake or your wallet. probably contributes to poor response.
solution-
apex 2200 15c. probably the best & best bang for the buck lipo you can buy

#2 get rid of those s75's.
reason-
they might work on a little BCP, but a trex is like 50% bigger. and we know just how "adequate" they are on the BCP HehE....save them for a slowstick.
solution-
someone mentioned HS65's for the cyclic, that would be a wise move. buy a nice gy240 only to use a poor tail servo? the gy240 is capable with the right setup. if you want a cheap but GOOD tail servo try the hitec hs81. it's bigger than your average submicro, but it gets the job done and it's cheap and easy to get.
Old 03-16-2006, 09:51 PM
  #13  
larryk9
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Default RE: Trex control issue

Ok so I bit the bullet and bought 4 HS 65 servos and another new 2200mah 16c lipo. I have the servos installed, but I am having some ccpm interaction issues. I'm pretty sure they have been there since day 1 with this heli. I've been over "Bob's Videos" a few times and have everything set pretty much perfect as far as everything being centered and smooth. What is happening is when I hit left or right cyclic and let off the stick the swash plate bobs up or down. THis is of course causing the pitch to bob as well. Nothing is hitting and there is no binding anywhere. I noticed this on my last flight with the old servos as well, but it is easy to see by just watching the swash plate on the bench.

Any Ideas?

Larry

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