zope_pope

Is it just me or this rod is flimsy as hell and the holder below the horizontal wing thing is not lined up correctly.

I am getting a bit of tail wag at all gyro settings (not much) but I think it is because of some slop/binding in the linkage. How have you guys made the rod more stiff, or what did you replace the rod with? Also, are most of you using or cut off that little holder thingy. I am sure once this is resolved, she'll be rock solid (401).

Let me know your thoughts. Thanks.

blacksheep1998

You can get a CF rod, but if you have wag maybe too much gain? Which Rex? Using digital or non for the servo, using z-link or ball joint for the connections?

Pete

zope_pope

450SE, GY401, 9650. 45% Gain, not much wag, but it comes and goes through out the flight. Its kind of odd. I also need quite a bit of right trim on my TX for the tail to stay put. The weird thing is the first flights needed no trim at all, but not all of a sudden it needs a lot of trim. Hmmm.

mxracerx43

You should not use the trim buttons on your TX with the 401 and a digital servo you need to mechanicly trim the rudder. Kepp the rudder trim centered

zope_pope

isn't the gyro supposed to keep it pointing one direction, and the linkage setup so that when everything is centered the tail pitch is centered too?

gt_jumper

i dont know about what i do with my gyro servo setup being correct but it is fool proof. have the transmitter set to hh mode as you plug the battery in, DO NOT move the heli in the first few seconds as the gyro sets its self. judging that you are doing this the red light will be on. I take it you are using the wire control rod with the 2 supplied routing eyelets to hold the rod straight? You can buy a carbon rod and do away with the wire and its all the tail control you will ever need.

Now, your servo has to be at neutral in all trims on the tx and have the horn being at 90 degrees from the servo body and have the endpoints set to 100 for the time being. now switch the gyro to standard mode so the light goes out, turn the limit pot untill the tail pitch slider barely almost touches the stop on each side, if it comes closer on one side more then the other you have to go back and reposition the servo mounted on the boom to get the perfect centre. Now switch the gyro back to head hold mode so the light comes back on. that should be it but the tail wag seems like you are running too much gain. Maybe your servo horn is too long, i like to have the control rod hole about 10mm from the centre of the servo's output shaft. also dull your gain to about 30-35%. Maybe one more thing is to check your delay pot is set at zero for that servo you are running is plenty fast!! Hope this helps.

zope_pope

I am using the eyelets, and the wag has stopped. Played with the gain a few percent. From everything I read online, though the tail doesn't need trimming, however when i setup my servo so that the center with no trim is the center pitch setting on the tail, i have to trim the heli a ton! Does headspeed have anything to do with this?

I am running 2200 rpm on the 325 woodies and a 12t pinion on the 430l. Let me know your thoughts, and thanks for the suggestions so far.

Andrew McGregor

Ok, you need a touch more headspeed if you have the 22T tail drive gear, you don't have enough tailspeed in that case. That might be the problem, but trim may also be the problem *and* the solution.

Contrary to other advice, it is possible and sometimes necessary to use trim with a 401, but you do have to know EXACTLY what is going on and why you're using it.

So here goes:

The rudder channel signal is interpreted as a piro rate in HH mode and as *both* a servo command and a piro rate in normal mode. In normal mode, the gyro will adjust the servo command a little bit to maintain the requested piro rate. In HH mode, it will make up a servo command that should result in the heli pointing where the commanded piro rate would have taken it; if that was nowhere, the tail will be locked, hence 'heading lock'.

That means that if the heli is going to hover right in both modes, the gyro has to know what the neutral trim position is in normal mode, so it can subtract it out in HH mode.

The gyro reads that trim position a) when you first power it on getting it out of the box and b) when you change modes three times within a second and finish in HH mode.

This is important for two reasons. One is that transmitters and receivers vary as to what the center stick position translates into on the gyro channel, so the gyro has to be able to adjust for it, and two because you never want the trim setting to change in flight; if the trim does change, the heli will start to piro slowly.

Most transmitters have separate trim settings for each flight mode, so you should NOT adjust anything using the main trim. Subtrim, however, is safe to use if you do it correctly.

So, firstly, with the power OFF on the heli, go through every flight mode and zero the trim.

Now power up as normal, and do the switch-mode-three-times dance, remembering to finish in HH mode (it doesn't hurt to switch more than three times, so long as you do stop in HH mode). This will reset the gyro so it now knows where neutral is.

Your setup may be close enough that this fixes the trouble, so carefully try hovering in HH mode to see what happens. DO NOT TRIM.

If it won't hold, put it back down and switch to rate mode, and see how it behaves. You'll probably find it turns in the opposite direction and about twice as fast. It will try to twist each time you change the collective, because you have no revo mixing... you don't want that, so only pay attention to what happens in a stable hover between collective adjustments. Try to fix the drift mechanically by moving the servo, but note it doesn't have to be perfect, just good. Once you have it reasonably good, tighten up the servo mount properly. Now adjust the SUBtrim, not the main trim, until it holds. Do the switch-three-times dance each time you make an adjustment before testing it.

Check the limit adjustment at this point and make absolutely sure it isn't binding at either end. Don't worry if it won't go quite all the way in one direction.

Now it should hold much better in HH mode, and you should be able to turn up the gain quite a long way before it starts to wag, or oscillate on stopping a quick turn.

Oh, and get a set of carbon tail blades. The uniformly black carbon blades are the best ones Align make, and are excellent value for money. The difference over plastic is significant.

zope_pope

Hey Andrew,

Thanks for the long detailed explaination. I'll give this a shot tonight. What headspeed should I be looking for? I am a beginner that can just fly circuits and the usual stuff. No upside down quite yet. Thanks again, and I'll post results tonight. Have a good one.

gt_jumper

I alo cannot see any reason why standard mode would be used other then setting up the servo limits in the initial setup stage. i havent gone into standard mode while hovering ever!

zope_pope

Man, this just doesn't make sense to me at all.

I go up in gain and I get tail wag, I go low and the tail is loose, but no matter how high or low the gain is the heli always will need right stick from me to keep it pointing in one direction. I tried andrews suggestions and the tail just didn't hold unless I added sub trim and didn't do the three switch dance thingy. I see most setup their heli so that at neutral servo (at a 90 degree angle) and no input the tail is centered. It just seems that the gyro should be holding better, no?

So the problem is no longer wag or no wag, its just the tail will drift no matter what unless trim is used. I could trim it mechanically by moving the servo and adjusting the rod, but that would severely limit one side of travel because I would need to adjust the servo limit. According to finless's videos too, this isn't the way to set the TREX up...

I am so confused. Help an airplane guy that is new to helis out.

blacksheep1998

Which radio and RX are you using? A futaba, JR or specktrum?

Pete

zope_pope

Futaba 9CAP, 146p rx.

I can get the thing subtrimmed so that it holds in rate mode, but in hh mode it always wants to turn left. The more gain I give it the worse. Its very odd.

I think it has to do with headspeed or something. My inital flight on my trex had a headspeed of like 1600 rpm and it held like none other. I have since cranked the speed to 2200 but that is when the problems started. Could it be related to pitch curves and what not? I am very new to helis...

blacksheep1998

I use a JR, so my setting for gyro are completely different. Finless uses a 7CHP which may be near to what you have.

For beginner, set the pitch curve to like 40 (L), 45 point2, then 50, 75, 100 for points 3, 4 ,and 5 on the scale, unless you have more than a 5 point pitch scale. For throttle leave it linear, 0 at low 100 at high stick. You have a pitch gauge and have checked for no more than -11/+11 when at low and high stick (before you mess with pitch curve), You made sure the tail slider was in center, set travel properly by the limit on the gyro, with the 9650 gyro should be set to DS.

So for the 401, HH is a solid light. For the channel you have the gain plugged into, set the endpoints to 50 each way. Dont mess with the limits, or sub trim for the channel the gyro is plugged into.

Let me know what you have set, perhaps we can figure this out. I am waiting on crash parts to finish setting my bird up. (had a little mishap on first hover, wasted the gear and antenna) Mine is very different as I am using a JR XP7202 so had to play with it on my own to get it into HH, and program a switch to get to standard for limit settings.

Pete

zope_pope

Hey Pete,

Thanks for the help. I was trying to set it up at 2200 rpm constant through the pitch curve which was pretty much linear from -2 to +11. Throttle is like 0, 70, 75, 85, 100. Something like that. Gain is 40%. I have the limits set, I have the mechanical trim set (even this didn't help). The odd thing is, now the thing is rock solid in normal mode, but it drifts in heading hold. The gyro is set per every instruciton I have found so,.... I started to do some experimenting (below)

I dropped the headspeed down to 1600 like originally set and the thing stayed a lot more solid than it did at 2200 rpm. This brings up two conclusions to me that it either is responding to vibrations the gyro is undertaking (higher rpm, more vibrations), or the headspeed has a lot more to do with it than i thought. I am using the stock futaba tape. Is there something better I can use? Also, how do most of you folks make a carbon rod to link the servo to the tail?

blacksheep1998

Seems like you have all your settings right on, throttle curve seems a bit high to me, but perhaps that is because you are running high head speed rather than swaping to the 12T pinion from the 11T?

When you hover, are the blades tracking properly? When spinning the heli up is there any wobble in the disc? If so then may be a blade balance issue.

For the rod, look at the websites like helihobby, helidirect ect..... most have a CF tail rod conversion set for the XL/SE. I looked through all of Finless setup vids, he had a set of stack carbons that were terrible balance wise, perhaps switch to the woodies that came with the SE and see if that makes a difference. For mine I have the align blade balance tool on order to balance mine after seeing how far out his were. If your impatient take a blade to the hardware store, buy some threaded rod that fits nice into the blade hole, and a couple of nuts and washers and make your own balance tool.

And the limits you set, on the TX for the gain channel only, and the gyro for the travel fo the servo?

Pete

zope_pope

Well, got this issue solved.

Mounted elsewhere on the frame, and boom. Rock solid. Vibrations were getting to the gyro. Thanks again everyone.

blacksheep1998

Great glad to hear it, balance the blades still may not be a bad idea tho.

Pete

zope_pope

True. I'll balance them as well. Can't hurt at all. THanks again for helping.