500 Derek's Trex 500 hover test

[Derek]

Thanks for your two and three cents, Gaba! I have tried rotating the servo arm to see if it would fit in different positions and each time it lines up the same. I'll go through my spare parts and see if i can find one of those round servo arms. Maybe the holes on a round one will line up.

 

[pvolcko]

Yeah, I agree with Gaba. You should be able to find a position that that horn lines up a lot closer to 90 without any subtrim. Just like with a fbl system, you cannot use subtrim on your tail servo with a gyro on it. The gyro will interpret this as a stick input and will move the tail servo accordingly in heading hold mode. That's why it is jumping to a new position when you switch to HH mode at the end of the vid.

With it at 0 subtrim in rate mode the servo is in it's "reference" or center position. Take the horn off and rotate it around to find the position closest to 90. If they are all off, you need to get another horn and try with it. Remember, the distance the ball is from the servo axle is important so whatever horn you use needs to have close to the same ball position offering as the stock horn you are using.

In my opinion, it does not need to be exact. Some people go nuts trying to get things exactly centered and exactly 90'd. Yes, you will have an ideal balance between throws in either direction if it is exact, however this is not strictly necessary, especially with a heading hold gyro where the gyro will work to achieve the rate of yaw you input as opposed to your stick movement directly translating into a servo position, as it does in non-gyro and rate-gyro mode.

 

[Derek]

Trex 500 in the air - YouTube

So...we have positive progress. The tail wag (hunting) issue is MUCH better, but the tail just feels soft or spongey. I'll move the tail to one side or the other and then bring it back and the tail seems to bounce and then get steady. What's even more weird is that according to many people here on the site, on YouTube, and the Trex 500 manual...they all say that my gyro setting should be around 75ish. Truth be told, my gyro is set to 25 on my DX8.

I did buy a new tail servo, the other day, got it home, only to find out that it didn't work. I did take it back and got a working servo (tested it before I left the shop). I'll put the new servo on the 500 tonight and I'll try again tomorrow. It's getting dark now, so...no more flying.

 

[breeze400]

Looks better anyways!

 

[Derek]

Yes, it sure does, Sam! I'm feeling much better about this but it's still not where it should be. I was able to get the 500 about 7-8 feet in the air and not feel that it was going to go nuts. I just lowered the collective and set it down gently. It was nice! Still got some tweaking to do, but I'm still on it.

 

[Tony]

I didn't read through but a couple of posts and can't watch teh videos cause of network issues, but I want to clear something up right now. You CAN use subtrim to center a servo if it has a gyro on it. If you couldn't, how are you supposed to trim out a 500 fbl with teh single straight arms? subtrim is NOT going to hurt or mess anything up. But if no one wants to take my word for it, that's fine. Hope you get it all figured out.

 

[Derek]

That sucks that you can't see the short video right now. I had my 500 about 5-6 feet in the air and I was holding it very well. I'm happy with the progress. There just seems to be a bit more tweaking that is needed.

Now, as far as the "Sub Trim" topic. Tony, I have followed your advice for nearly a year now and you haven't failed me yet. If you say that Sub Trim can be used, then I fully believe you. Some people may choose to not use it and that's fine, too. No worries buddy!

 

[coolgabsi]

Subtrim should t hurt it like tony says.


Just that tail servos in general ( I have used a few) come out with perfect 90 on servo horns just giving them A shot ..



I learned from tony. He basically setup my first bird lol . so please don't think I said tony was wrong . He isn't.

I don't know why that is happening. But just if subtrimis causing it.. A different horn might be an easier work around is all

Fly safe!! have fun!

 

[Tony]

Was finally able to watch teh first video. Every time you adjust the subtrim in the rudder, you MUST reinitialize the gyro. When you put that subtrim into the Tx, the gyro sees it as you have just moved teh stick. In HH mode, it's going to hold left rudder until that helicopter moves into the heading that you just told it to go. And since it was initialized with a different "0" heading, it will keep holding that thinking that you are wanting the heli to do a piro constantly. Unplug the battery (if you do this again) then plug it back in and everything will be golden. Or should be. IDK. 3 hours of sleep, it's going ot be a LONG night.

 

[coolgabsi]

That actually might be it. Re initialize after subtrim...

Fly safe!! have fun!

 

[coolgabsi]

Btw : that's an awesome hover there!


Good job

The gain seems low (slow wag) on the tail.

Fly safe!! have fun!

 

[Tony]

Finally watched teh second one, damn storms. Try adding a little more right thrust and see if that takes the hunting away. Or just raise your gain, or both. I don't think you will be able to go to 75%, but you should be able to get to around 40%. Also, you can try putting the tail servo ball another hole in. That should help tame it down just a bit more. Waiting to see the new servo and if it helps.

 

[Derek]

Oh , ok. I didn't know that I should have reinitialized the gyro after the setting change. I think I remember that someone mentioned it.

But...I did find a different servo horn that allowed me to get the desired 90 degrees. I'm looking forward to daylight coming, in about 6.5 hours so that I can try the 500 again. I am so close!!!!!

- - - Updated - - -

The gyro setting this afternoon was a low 25. Any higher than that and the wag or hunting comes back stronger. I'll move the ball link to another hole tonight and we'll see what happens tomorrow. Now...moving the ball link to another hole won't give me the 10mm that is suggested in the manual from the ball link to the servo screw. Or...are you suggesting to move the ball link to a different hole that is 10mm away from the servo screw?

 

[pvolcko]

All I was saying on the subtrim is what you said, Tony. The gyro was seeing it as stick input. I didn't know a tail gyro could be "reinitialized" to accept a given subtrim setting as a new zero. On the ikon and 7200bx you have to use fbl trim to get things 90'd out. Figured tail only gyros had something similar.

 

[Tony]

Nah, even the 3GX you have to use subtrim in teh DIR menu to set up all of the servos, including the tail. The Ikon and others that have just come out are now wanting you to do everything in teh gyro so that the gyro knows exactly what is going on and why.

And Derek, if you have found a horn that can get you 90 without subtrim, great. Just make sure you are putting it on the new servo. And test the new servo before moving the ball. 10mm is where it should be.

 

[Derek]

I can do that!

- - - Updated - - -

Btw : that's an awesome hover there!


Good job

The gain seems low (slow wag) on the tail.

Fly safe!! have fun!

Thanks a lot, Gaba! The 500 definitely hovers much better than it did with the stock head. Tony helped me install and setup a cnc flybarred head that I bought. The cnc head is so much smoother and I love the DX8. The feel of the sticks is much better than my DX6i.

 

[coolgabsi]

Nah, even the 3GX you have to use subtrim in teh DIR menu to set up all of the servos, including the tail. The Ikon and others that have just come out are now wanting you to do everything in teh gyro so that the gyro knows exactly what is going on and why.

And Derek, if you have found a horn that can get you 90 without subtrim, great. Just make sure you are putting it on the new servo. And test the new servo before moving the ball. 10mm is where it should be.

Yep cause instead of sub trimming they change servo center frequency to give you the right position

Fly safe!! have fun!

 

[Derek]

It was suggested to me, by a friend on Youtube, to try hovering my 500 in Rate Mode and see how the heli behaves. Ok, I'll try that. I've never flown my heli in Rate Mode, so this should be interesting. I spin the blades up...get light on the skids and up in the air...about 3 feet or so. The heli slowly turns to the left, as it was looking for a "left side in" orientation. I use the rudder to correct the orientation back to tail in and then center the rudder stick. It slowly turns to the left again.

I'm going to try adjusting the length of the pushrod and see what happens.

 

[Derek]

I took the main blades and the tail blades off the 500 and spun it up. 100% zero vibration going on (at least to my eyes while the heli was on my garage floor). It spun up nice and soft. I slowly increased the throttle to full throttle (75% in normal mode) and slowly backed it down. I even gave some sudden throttle increases, as if doing pitch pumps, and the heli just sat there. Ok, I was happy with that.

Let's put the tail blades on and try it again.

Spin it up...in HH mode, the heli wants to turn slightly (on my garage floor) to a right side in orientation. Hmmm, flipped to Rate Mode. Now the heli wants to turn to a left side in orientation. Hmmm. Perplexing!!! I decided to lengthen the tail push rod and see what happens. Did that and spin it up. Ok...in RM, it wants to turn to a left side orientation still but it's a bit slower. Ok, lengthen the push rod one more turn. Now...while the 500 is sitting on my garage floor, after two "lengthening adjustments", the heli sits rock solid in RM with a very slight turn to the left, as to go to a right side in orientation. Now, I took that as "normal" because a heli will want to drift a bit to the left...right?

Ok, lets put the main blades on and try the hover test in the yard again. Spin it up. Sitting in my grass (wow, i need to mow) the 500 spins up, light on the skids and in the air. In HH mode (50% gyro setting on DX8) the heli begins to wag. Lets try RM (-50% gyro setting)....very nice and smooth with just a bit of turn to a right side in orientation. I went back to HH mode and lowered the gain to 40%, still wags. 30%, still wags but is less. 25%...yep...still apparent...and now my battery is very low, so I'm waiting for the battery to charge and I'll try it again.

I really feel that I am just "trying this" and "trying that". I just don't know.

 

[breeze400]

Did you change the servo yet?.