FBL Gyro Tuning B.D. Axon Gyro on my T-Rex 700X

[Heliman450]

That's some beefy landing gear you have there Phil... Should do the job nicely!

Hi Steve, I just want to be able to do my next tests without waiting too long and expecting another breakage with associated costs added on. I'll wait and see if this works longer term, however, I've got a new set of landing gear just in case as the heavy duty version pictured weighs in a bit over twice that of the standard one. The guys in the local hobby store said they know all about the breakages during cold weather, nice little earner, I suppose!

I'm currently setting up to sort the batteries and 550 with the Supra X connectors. One of our friends is not at all well so things have turned upside down in the last week. I'm hoping to get stuck in on Friday. Still snowing out there and very cold so I don't feel the urge to dash off to the heli pad anyway. Last winter didn't have anywhere near the same amount of snow for us. Fingers crossed.

 

[Heliman450]

Hi all, latest update in the saga............... long story short. During my maiden hover, I noticed a tendency for the tail to drop (rear swash tilt). This was my target for resolution when my landing gear broke

I made some enquiries with B.D. and checked over the info drop-downs in the software to find out why it could be doing this. Xmas and New Year holidays at B.D. delayed their response, however, I came up with some info from the software that sounded like "tune the gyro DURING the test hover". The only way I can think of to do this is via the trimming buttons on the Tx., a big NO-NO! It turns out that it's necessary to go through the setup process once again, so in this case, not during the hover.

The sequence of photos and screen shots below show what I discovered and what was done to correct the situation.

Aileron Servos Before Elevator Servo Before

Aileron Servos After Elevator Servo After

Settings Before

Settings After

Finally, my modified tail rotor for setting up. Why? I hear you asking. So that I can still see it from the computer as it's so far away



Next job to put the rotor head back on and check the pitch range

 

[Heliman450]

Hi again,

Rotor head back on and main blades pitch checked out. It needed a couple of turns each end of the link rods and a small change in the software to bring them back to the settings as below.

Min. Stick Mid. Stick Max. Stick

That's all for today. Next stop is in my workshop to change out the tail gear set, finish off the new HD Landing gear followed by battery connection changes and finally another run through all the settings to make sure before my next trip to the heli pad.

 

[Smoggie]

Looks good Phil. As you say, trims on the Tx is a big no-no on any flybarless heli. I disable trims on all my heli setups.

The swash looked a fair bit out, was it checked for level during the build? I'm often too lazy to remove the head to fit a swash leveler, so I use the 'ghetto' zip-tie method:

It's just as accurate.

 

[Heliman450]

Hi Steve,

Yes, the swash was perfectly level prior to the first hover. That's one of the things that surprised me most. I'll dig out the B.D. wording later today.

Presumably you spin the rotor around to check each swash 'horn' individually using the cable tie system as pictured. I've heard of it but never seen or used it myself going for the 'locked-in' feel of the correct levelling tool. I'll give it a look-see and maybe your "lazy" way will feature for me at some point. It would definitely have given me an opportunity to see what had changed whilst at the field but not the ability to do anything about it until I got back to my laptop.

Bye for now.

 

[Smoggie]

Yes, you just turn the head and check the lugs on the swash individually. If nothing else it's a quick way to do a course check if you suspect a problem and dont want to go to the trouble of removing the head. In fact I think it's probably just as accurate as a 'proper' swash leveller, possibly more so because the levellers do have a little play on the shaft which allows them to tilt ever so slightly.

The 'proper' leveller is easier if you also want to check the swash at the top and bottom of the collective travel range (which is good practice).

 

[Heliman450]

Hi all,

As mentioned below here's a screen shot of the drop-down info from the software.



If you read the whole thing, I think it makes less sense the more you read it. The most misleading part is the last bullet point. Presumably the "sensor" is the gyro itself. "Trim the swashplate" is obviously carried out in the software. "Trim the heli mechanically" I presume means to re-check the swash alignment etc. FOLLOWING the first flight, not DURING the first flight.

I managed to change-out the front tail drive gear set this afternoon and tomorrow, will be doing my first session of battery connector change overs to Supra X so that I can use the batteries between both the 550 and 700.

Bye now.

 

[Heliman450]

Hi all, I returned late Tuesday afternoon from a trip over to the UK for a friend's 60th birthday. A really good bash! Back to my project with what's not quite on topic, but is progressing me towards my next test hover after suffering from the broken landing gear. Here are some photos of my new landing gear after modifying it a bit.

#01 #02 #03

Photo #01 shows the tilt now built into the landing gear as version one was the same height front and back and also much taller. My main objective was to introduce some spring into the gear as before it was solid. By trimming down the struts to take off the vertical sections and introducing some holes, there is now a bit of give in the arrangement. It remains to be seen if it becomes my normal landing gear or only my winter set. I'm sure there's still some improvements that could be made, but that will have to wait for now.

Photos #02/03 show the temporary landing gear underneath the new version. It was only temporary as it wasn't a standard set and only had a tilt of 1.9 degrees on the tail. I decided on less than the 5 degrees of the standard 700X gear in favour of the 3 degrees (always did like their music ). I also decided for an extension to the side rails so that it doesn't tip back when I remove the batteries. I think it will also prevent the tail fin from coming so close to the ground when landing as the back end will touch before the tail.

I also completed changing over the battery and ESC connections to Supra X so after I'm finished putting the 550's ESC back on, I will be able to take both to the heli pad in future (probably not just yet as the 550 only has the summer landing gear). If the 700X proves to be ok, I'll see about making up a set for the smaller T-Rex.

Bye for now!

 

[Heliman450]

Hi Steve, I just want to be able to do my next tests without waiting too long and expecting another breakage with associated costs added on. I'll wait and see if this works longer term, however, I've got a new set of landing gear just in case as the heavy duty version pictured weighs in a bit over twice that of the standard one. The guys in the local hobby store said they know all about the breakages during cold weather, nice little earner, I suppose!

I'm currently setting up to sort the batteries and 550 with the Supra X connectors. One of our friends is not at all well so things have turned upside down in the last week. I'm hoping to get stuck in on Friday. Still snowing out there and very cold so I don't feel the urge to dash off to the heli pad anyway. Last winter didn't have anywhere near the same amount of snow for us. Fingers crossed.

Here are some photos of my T-Rexes. The 700X is ready to test fly again after the beefed-up landing gear. The 550 just needs a couple of things doing and then a run through the Spirit Pro to check everything's still OK. Here goes for uploading in the new software.........

 

[Heliman450]

I like the new format for displaying the attachments

 

[Heliman450]

Hi all, quite a long time since my last update........... lots of other stuff going on.

I'm still on the case and have made up a test frame to help reduce the likelihood of damage during the testing, seems to work fine. I tried Steve's suggested method to level the swash plate using a cable tie but I need more practice before I'd rely fully on it. Yesterday, I managed to get to the field and did a quick test but felt the need to do a further check on the swash alignment. Below are a couple of screen shots showing how the settings have changed. Not a lot but the discrepancy still keeps turning up. It should be ok now so I'm going back to the field today along with my video camera.

 

[Smoggie]

Phil,
If you accurately level the swash, then later find it's gone out of level when you haven't adjusted anything, that would be cause for concern. It might mean that there is a servo problem.

A guy I know just got himself an Axon, it's fitted to his new Goblin 570. He's only had a couple of flights but seems very impressed. On the first flight he accidentally had self levelling turned on and couldn't figure why the heli was didn't respond as expected to cyclic. But once he figured it out and turned levelling off all was good.

 

[Heliman450]

Phil,
If you accurately level the swash, then later find it's gone out of level when you haven't adjusted anything, that would be cause for concern. It might mean that there is a servo problem.

A guy I know just got himself an Axon, it's fitted to his new Goblin 570. He's only had a couple of flights but seems very impressed. On the first flight he accidentally had self levelling turned on and couldn't figure why the heli was didn't respond as expected to cyclic. But once he figured it out and turned levelling off all was good.

Hi Steve, thanks for your feedback. I just returned from a really good session of testing this afternoon and am beginning to think that something's amiss. Maybe it is a servo problem. I'm thinking that if it is, then the main suspect is the 'Aileron #2' (right-hand or 'Pitch' servo). I also needed to wind the gyro setting right down below where I've ever set it on a heli to stop what was a terrible wag (25% and 30%). B.D. mention to set the value down for the first hover but only mention 10% less than "normal" or "what you'd expect it to be" I think is their wording. I videoed everything, there was no good part really other than my newly constructed training/test gear worked like magic and I suffered no damage even despite some very iffy situations.

Next job is to check everything out again ready for another test session asap.

 

[Smoggie]

Funny, I was flying my 700X and also 'playing' with gains though it's impossible to compare numbers directly as we are using different Tx and FBL. For head gain I had is set at 96 in the Vbar. I increased this to 110 and got some oscillation when pulling out of loops, so I dropped it to 100 which seems fine.
On the tail I increased gain as far at 80% at the Tx and there is still no sign of tail oscillation so it can probably go higher.

 

[Heliman450]

Fully appreciate your observation on that Steve. I'm running through the checks now. Just connected to the laptop so here goes...................

 

[Heliman450]

Hi all, latest update..........................

I managed to do a quick visit to the field on Friday but unfortunately I can't make the changes without the software. I've got my stuff at home so can check things out during my free time in the evening, too. I did some more changes and yesterday afternoon got the heli into the air without it wagging itself to pieces. It still shows a marked tendency to drift left/forwards and seemed to need lots of pitch to lift off. I gave it some thought overnight and ripped into the software again with a vengence this morning. I reckon that there should be a marked improvement next time out. Here's a summary of what I did............

1. Rechecked the swash alignment and lengthened the left-hand (Aileron 1) link rod by two turns.
2. Went through the servo travel settings and increased (a) collective range to give +/- 12 degrees. (b) Increased the cyclic travel, rechecked the cyclic degrees and made changes.
3. The B.D. description of how to do this is terrible, so I relied on previous experience combined with some considered trial and error as follows................ First I set the Collective to 50% and then I zeroed my pitch gauge to the tail boom and with the blades side to side checked the Elevator degrees and increased the Elevator link rod by one turn to achieve their stated 9-10 degrees (9.8 to be exact). Then I zeroed the gauge across the stand and with the blades in line checked the Aileron cyclic, which was fine (10.1)
4. Finally, I tweaked the left/right tail travel to give the same attack angle to both blades (deflection from zero degrees with a protractor). Note that I'm currently using plus 6 degrees of offset to counter torque in rate mode so that I don't need to give any stick movement for lift-off. I'll remove this when I've convinced myself I'm ready to engage Heading Hold mode.

I'm still concerned about what seems to be very low gyro settings to prevent tail wagging but I'll see how things go for now. At least I can make those changes without delving into the software. All feedback appreciated.

I'll keep you posted on progress.

P.S. My home-made training/test gear is working perfectly

 

[Smoggie]

Sounds good Phil. Personally I've never bothered with rate mode on the tail, I always fly heading hold. Other than for very specialist purposes like maybe scale helis, and speed helis I cant see any reason to use rate mode.

I wouldn't worry about having to use low gain settings, as long as the tail is working fine then it's good. Coincidentally I found the limit of the tail gain on mine today, I was trying to do tic-tocs and the tail was shaking as I applied collective (you have to be aggressive with tic-tocs).. So on my high headspeed I dropped gain to 66% in the Tx, moderate headspeed is 75% and low headspeed is 80%. This seems to be close to optimal for my setup but you cant directly compare % values with different FBL and Tx, so not much help to you I'm afraid.

 

[Heliman450]

Bad cold ........ staying home weather not good but at least feeling better so I'm expecting to test again on Thursday

 

[Heliman450]

Hi all! Thursday testing went fine as far as weather was concerned and resulted in a stripped set of front autorotation gears. The main autorotation gear is fine, so only the transfer gears are ordered up (2 sets). Whilst checking out the Align website, I noticed that they've now got loads of various options and thought "WOW! What does this lot mean??". This prompted me to create the attached PDF in Excel to work out exactly what does it mean. This task developed into quite a research project but now I'd appreciate some feedback on the results. This thread started as tuning my new B.D. Axon but I reckon has opened up a can of worms for me, as I'll need to return to my 550/Spirit Pro combination, too. Here goes................

If you check out the PDF, the top section numbered 1 to 4 are all control variations using my standard 700X gearing. The bottom three are various options of available gear sets, which can be fitted albeit that the 112-toothed main drive gear is 13.5mm thick and needs mods to the frame to accommodate it as the standard 110-toothed is only 11mm thick.

It looks to me that I've been using far too high a throttle setting. Align recommend a maximum of 2200rpm for the main rotor, so I set 85% to start off with. After doing some changes and resetting stuff as per previous threads, I actually increased the throttle to 95% resulting in an excessive value of 2443rpm with the tail increasing from 11,271rpm to 12,597rp!. No wonder the Axon seemed to be struggling. Next time out, I'm going to drop my head speed well down to approximately 1600rpm, which is the figure generated by Steve's head speed calculator he uploaded a while back.

That's enough for now, I'm looking forward to some feedback.

 

[Smoggie]

Hi Phil,

The tail gears are an interesting subject. You have to use them in pairs. the 104t auto with the 22T spur is the standard ratio and good 90% of flyers. The 102/23t option gives lower tail RPM for those why fly at very high headspeed and like doing screaming overspeed auto-rotations.

You cant mix the 102t auto with the 22t spur or the 104t auto with the 23t spur for two reasons:

1. The PCD of the gears is slightly different so they need to be used in matched pairs to maintain shaft centre to centre distance
2. In order to prevent anyone trying to mix them Align made the slant on the gears opposite hand.

The 21t spur gear is for the 700 nitro only. Due to reason '1' you cant use this on the electric heli.


You will also notice that all the new TT drive gears are red. I'm not sure if this is just because someone at Align lilkes red or if the red plastic is stronger? Align have also recently introduced a beefed up tail boom case because under very hard use the original one could flex and allow the mesh of the bevel gears to open up. the new tail case has thicker plastic where the small bearings are mounted. I got hold of and fitted one of these new cases just last week. I got it direct from Taiwan as they hadn't arrived in the local dealers: ALIGN T-Rex 700X Tail Boom Mount Set H70T013XXW New | eBay To make a complex situation even more complex this updated tail box needs to be used with updated gears, the old gears don't quite fit but as I discovered are easy to modify to make fit.