Setting Up the GP-750 gyro in T-Rex 250 kit

[PlaneHeli]

warhawk,


I wouldnt expect a reply from align themselves. I dont believe anyone ever has.
Ive only seen a statement from their sponsored pilots or agents.
The LHS should send you out a new tail (paid for by align im guessing).

I know its frustrating. I was too. But like most, I went out and bought the 9257 servo. It cost between 20-25% of the cost of the super combo. But without it i think this heli would spend all of its time on the shelf rather than being flown.

So you may have to bite the bullet and buy a better servo if you cant make it work with the other recomendations.

I think align has sent out the 2mm bearings with the attitude theyve fixed the problem. Yet the torque to drive the tail blades at such high rpms may be too much for the supplied 420 servo, especially considering the tail blade design and manufacturing.

Maybe theyll make some tail grips with chinese weights built in you will be able to 'Buy as an upgrade'. Or design some tail grips like the 450V2, which may reduce the likelihood of binding.
Will have to wait and see on that.

Im using the 37mm batman blades uncut.
The square blades are 40 - 42mm with a greater chord, so I would expect they would need to be cut shorter than 37mm to result in the same thrust (and load).
Put some 37mm batman on uncut.

I had some cut down blades on but found I was running out of thrust to counter the torque when increasing the throttle / pitch quickly. (Well thats my theory). The 37mm seem OK.
With the cut down blades, I couldnt increase the gain anymore to hold the tail without getting tail wag.

Good luck.

[Finless]

The batman blades when they came out for the 450 first were design to help try and remove some of the force of the "Tennis Racket Effect". I plan to use those myself and later add Heim Joints weights.

FYI if you are still using the 2 bearings in each tail grip, you need to get the new single bearings period!

Bob

[PlaneHeli]

Originally Posted by Finless

The batman blades when they came out for the 450 first were design to help try and remove some of the force of the "Tennis Racket Effect". I plan to use those myself and later add Heim Joints weights.

FYI if you are still using the 2 bearings in each tail grip, you need to get the new single bearings period!

Bob

Perhaps we should be trying the 42mm blades cut narrower (ie: reduce the chord). Rather than just cutting them shorter. That may reduce the "Tennis Racket Effect". If im understanding you correctly.

Anyone tried it.

[helidude3]

I don't get a tennis racket effect with my square blades cut to 35 mm. I might try and cutting the batmans to 37. Does anyone have a better way of doing this than using scissors?

[cH@0s]

I'm still a little lost here. So if using Gyro Travel Adjust (DX6i), what values get put in the gyro menu? 0%?

At the moment my Gyro Travel Adjust is 100% up/down. Im using the gyro menu to control my gain.

Also Gyro switch up is HH and down is Rate?

[helidude3]

depends on your settings, over 50, hh, under 50 and your in rate.

[cH@0s]

That cant be, because travel adjust goes from 0 to 125. Yes, gyro menu goes from 0%-100%. But if I wanna use travel adjust to set gain, then do I set my gyro menu to inhibit (INH)? And use the travel adjust settings?

[Finless]

He is talking about the gyro menu. Above 50 is HH and below is rate mode.
Yes if you use gear channel travel adjust INH the gyro menu. Gear switch UP is HH mode and you change that number in travel adjust. Gear switch down and it's rate mode and you can change that number in travel adjust.
Start with 35 on travel adjust for both.

Bob

[cH@0s]

Ok great, thanks a lot!!!

[ryem3]

I got the Align replacement tail kit with the single bearings. I love the way the kit shows the bearings being installed straight into the grips. If you don't add a spacer between the grip and the holder, the tail doesn't turn! Add a micro thin washer and the grips wobble. Did I do something wrong?

[helidude3]

nope, everyone's wobble. The only way to get read of it is the spacer mod w/ double bearings.

[Rexdestroyer]

I now have my tail holding solid with no wag using the GP 750 Gyro and 420 servo. I tried setting my gain using the gyro menu first. The number that worked best for mine using the gyro menu was 68. It seemed like there was a slight amount of wag at this setting but not much. Next I switched to using the gear channel end points. Success! +/- 35 seemed to be the magic number. It is rock solid now with no wag.

Thank you Bob for that great explanation between gyro menu and gear channel. That helped a ton!

[Dwyn]

Just trying to set my tail up on a Futaba 14MZ, finding a gain of over 23 causes huge tail wag what gain is anyone using on futaba gear?

[tommyb]

Just wanted to throw this out there. I have had the 250 for a couple weeks and was having trouble getting the tail to hold. Minor wag, but when I hit the throttle/collective hard it woudl break loose, and on occasion just break loose all together. I thought my tail was holding well based on the thousand or so posts I'd read, but the first time I went inverted, it broke loose into uncontrollable pyros. Fortunately, no crashes, so I'm not that pissed. I tried most of the tips I've read here, but finally, I installed the new tail hub grip combo, and bam!, rock solid!

I have to say, when finless, speaks, listen up. I'd didn't take the new combo apart, but I'd have to assume its the version finless recommends, as the difference is so dramatic.

Still a little torqued that its completely a mfg defect, but for $14 the problem is solved, vs. spending hours trying all the homebrew stuff. It does suck to be beta testers, but that's the nature of the beast with helis.

Have fun, and hope this helps someone.

Tom

[9sec240]

I am so confused. I bought my 250 used and just needed to install an RX and bind it to my DX7se. Everything went perfect and it flew quite well with the GEAR switch assigned to GYRO with settings at 70 on 0 and 30 on 1. In RATE mode (or what I though was RATE mode) the tail held fairly well, no drifting, no wag, slight kick when doing pitch pumps but it would correct. Mechanical seems to be good.... In HH mode it flew exactly the same. Not too bad.

I decided to go though the heli today and make sure everything was set up correctly (as I did not build this heli or set the ESC or Gyro) I was looking at the instructions for the gyro and see that there is a light indicating Heading Hold and Rate. I switch between Gear 0 and 1 and the light does not move. Adjustments on the GYRO menu had no change in HH / Rate indicator. After a bit of research, I finally figure out that when asiging GYRO to the GEAR channel on the DX7se, the switch that changes the mode is RUDDER D/R and NOT the gear switch. How stupid is that???? I use the RUDDER D/R switch for throttle hold just like I did on my DX6i. I made the assumption that GYRO would be on the GEAR switch just like the DX6i also. Well... anyway.

I decided to change the gyro gain adjustments to gear travel adjust. I assign GEAR to GEAR and then adjust GEAR end points to adjust gyro gain. First thing I notice is that in RATE mode, the heli is spinning. It is obvious that the tail is not mechanically set. I play around with the tail servo linkage and get the tail to stay fairly steady even with gain set very low. I figure I can turn the gain up now and the tail should hold well. Umm... no. I turn it up and end up with wagging. Turning it down I get a sloppy tail. I decide to check HH mode and it is the same thing. Lots of wagging with gain turned up and sloppy tail with it turned down.

So my question is... why was the tail holding decently with the original setup with gain turned up a decent amount and the tail mechanical way out of whack? Should I go back and whack out the mechaical on the tail and see if HH works better? I am so confused.

[francisfaustino]

hi, you bought that heli from me... i tried setting it up initially to hover at rate mode but it was just too much of a head ache for a mode that i will never use anyways... the tail setup was not out of whack... it was set up so that tail pitch was at zero when the servo arm is at 90 degrees...

obviously, a tail setup that way is only going to work in heading hold mode and there's really not a clear answer which setup method is better... knowing that my heli will hover at 90 degrees servo arms do make me feel better, but in practice, with heading hold mode, i have given up on the idea...

the only reason i can think of why you can turn the gain up with the "out of whacked" tail is because of the location of the servo arm... if you think about it, a servo arm at 90 will move more in parallel to the tail boom per servo resolution than when the arm is not at 90... when the arm is not at 90, a lot of the movement is also directed perpendicular to the tail boom... meaning that per servo resolution, a servo arm at 90 will have less precision of movement parallel to the boom...

[9sec240]

Originally Posted by francisfaustino

hi, you bought that heli from me... i tried setting it up initially to hover at rate mode but it was just too much of a head ache for a mode that i will never use anyways... the tail setup was not out of whack... it was set up so that tail pitch was at zero when the servo arm is at 90 degrees...

Thanks again for the deal on the heli. I did not mean to imply that the heli was set up poorly by you. I obviously had to put the tail back on when I received it. I was pretty sure I got it close due to the way it flew well out of the box.

I hear your frustrations on setting it up in rate mode. That is the reason for my post. I should have just left well enough alone, but I am a fiddler. Anyway, if the pitch was at zero with the arm at 90°, this would explain why the heli spun in rate mode.

Originally Posted by francisfaustino

the only reason i can think of why you can turn the gain up with the "out of whacked" tail is because of the location of the servo arm... if you think about it, a servo arm at 90 will move more in parallel to the tail boom per servo resolution than when the arm is not at 90... when the arm is not at 90, a lot of the movement is also directed perpendicular to the tail boom... meaning that per servo resolution, a servo arm at 90 will have less precision of movement parallel to the boom...

That does make sense. I am going to play around with the tail control rod today and see if I can get it to hold like it did when I initialy got it. The only other thing I do want to do is take the regular servo arm off and put a round one on.

[9sec240]

Well, I got it all set like it was when I first took it out of the box and slapped the tail in it. The slider is centered and the arm is at 90. I swapped the regular servo arm out of the round one and it flies just like it did before. The tail is ok but moves a bit on punch out. I played with gain and was down to about 25% on Gear EPA. I decided to try out F1 (100-85-100) and the tail wagged HORRIBLY. I had to turn gain down to 15% to get it to fly reasonable. meh.......

[9sec240]

If you have not replaced the tail rotor control arm with the H25092 arm, I would suggest it. The fulcrum is different than the original H25062 but the same as the H25062-1. The hole for the tail slider ball is also much tighter than the plastic H25062 I had on my heli. The slop is gone in the tail now and I was actually able to set my heli up in Rate mode and then switch to HH mode with success. I went from running 15% (DX7 Rudd EPA) to 30% and really good tail control in pumps and piro stops. Clicking up to F1 resulted in slight tail wag but NOTHING like it was yesterday at 15%.

I still need to get an integrated weight tail set (H25095) and see if that helps too.

[stg099]

Hey Ivan, it's John, we met at the Busse field Sunday. wanted to let you know that I got my tail wag/bounce solved for the most part. I modifield the tail grip bearing arrangement and used 1 1mm Gaui bearing, then a spacer, then the 2mm align bearing, which removed the slop in the grips, then made sure all was moving freely in the tail (took a while but I got it smooth now) and also found that the gyro tray was vibrating when the heli spooled up due to it being a tad loose in teh frames, and that was adding to the issue. after securing everything, I ran a gain of 57% on the gyro sense menu and used a Futaba 3154 servo and it hovers rock solid with no wag now. I've yet to fly it outdoors but will report back when I do.

I also ordered a set of the Heim Joint weights for the tail, as well as his bearing spacers, with those added I'm hoping the tail will be good enough to 3D this little thing.

-John