1st Flight on new Stratus Today = Tail drift

[chrisvau]

Well today was the big day. Took the new Stratus out for its first flight.

Here are some pics after its maiden:

http://www.dslrfocus.com/stratus/StratusFront.jpg
http://www.dslrfocus.com/stratus/StratusLeft1.jpg
http://www.dslrfocus.com/stratus/StratusLeft2.jpg
http://www.dslrfocus.com/stratus/StratusRight1.jpg
http://www.dslrfocus.com/stratus/StratusRight2.jpg

So here is the final rundown on what’s in the bird:

Stratus OS 8.18 Kit
OS 91 SZH Pumped
Hatori 938
Futaba GY-611 Gyro
Arizona Reg with 4800mah Peerless LIO battery
Futaba 9252’all around other than 9256 on tail.
Radix 710 mains
Sab 105 Tails
JR 10DS Receiver

The new OS91 SZH Pumped never been run started first flick of the starter switch. I could not believe it.

Set the needles rich and hovered first tank. Engine was a little rough but the heli felt so stable and crisp. After bench setup all she needed was one click forward trim and 1 click left aileron and she then hovered hands off for 5 seconds no problem.

The tail was playing up and kicking a little left and right also with a very slow anticlockwise drift. I figured this was engine tuning so ignored it for then.

Next tank was a little better. Leaned mid and high end up a tad and it smoothed out some but the tail was still playing up.

3rd Tank same story. 4th Tank leaned it up a little more and felt a little better but still kicking a bit in the tail and still slight drift.

5th Tank we started leaning it up a fair bit and suddenly tail was not kicking and heli was much smoother. Tail drift was now minimal. 1st thing you notice is the power. The thing climbs and one hell of a rate. Just awesome.

6th Tank I did some circuits loops rolls and flips. 1st time I gave full left cyclic I nearly creamed my pants. The thing rolls like a pattern plane. Fast and precise. The heli feels likes it on rails Just goes where you point it and does what you tell it. I’m only a fairly new heli pilot (since Feb this year) and felt comfortable rolling , looping, flips, stall turns, split S, Cuban 8s on its first circuits. I was very happy how it flew. Sure it was a little scary being my first 90 but not intimidating.

Tank 7 engine felt a little rough again and although tail kick was gone I still had a tail drift. There was some vibration as I could see the fuel frothing a bit.

Leaned it a little more and the frothing went away , but tail drift did not.

Tank 8 was just hovering trying to figure out tail drift issue with no success.

So before everyone gives obvious advice, I did have the GY-611 mechanically setup up per manual, no rudder trim was activated in any mode on TX. I tried Gyro with 1 layer of tape, with 3 layers, with without metal plate and it made no difference. Gain settings had no effect on drift. High or low the drift was still there. All settings in 611 were default. Yes I was in AVCS mode.

There a is fair bit of talk about this kind of drift with 601 and 611 on the net, usual suspects are some kind of high frequency vibration. I did balance my whole tail on hi point balancer and my fan and I used a dial gauge to get fan runout to 2 thou so I cant imagine that is the cause. Visually the helicopter looked smooth and felt smooth in the hover. I could see no signs of vibration like on tips of tail vibrating etc… unless engine was rough while tuning/breaking in then I would see some fuel foaming.

Guess I will have to recheck everything make sure nothing is loose.

So right now I am very happy and also a little frustrated. The heli feels like a formula 1 car and I am very pleased the first flight went so well, but the tail drift is just not acceptable and I now have to start trying to figure out what’s causing it. I may move Gyro sensor to battery tray and see what happens.

The only thing I did not do was check the balance of the main blades or paddles. I used digital callipers to set paddles same distance apart and the blades are Radix 710 which I cant imaging would be out of balance to the point of inducing that kind of vibration.

Any other suggestions on where to look would be good.

Also I did notice that the gap between the fan and clutch assembly got much smaller after my first flight. Before flight it was bout 1/2 mm all around. now its very tiny. I can see light through it all the way round but its pretty small gap. Is this normal ?

Best Regards
Chris

[Mille aka Fredrik]

Nice canopy!

[mevigavant]

i think once the engine break-in is done it should fly much smoother and your tail problems should go away. it doesn't say, but do you have a governor on it.

[Jim Platt]

Chris----Hate to say it but .002 is not close enough on a Stratus.... you need to get it below .001, preferbly .00025 or so. Either Dr. Ben or GM1 (can't remember which) has posted a thread on dialing MA fans. Try and find it and follow their excellent instructions. I'll bet this takes care of the drift.
Oh, by the way, very,very nice looking bird-----
Jim

[sookainian]

wow i am running almost the same set up as u got there. Only different is i am using 2400 mah sub-c, Vblades and tail and GV-1. :glasses2:

[Double D]

I had tail drift with mine and I added two pieces of Futaba Gyro tape then the metal plate another piece of Futaba Gyro tape then the sensor and then Velcro around it and tail drift went away.

[chrisvau]

Thats how I had it at the start. 2 pieces of futaba tape. metal plate and another piece, then light velcro strap and the drift was still there. I am going to recheck balance of tail, main blades and paddles then move it to under tray and see if it goes away. If not then I will start pullign out engine and fan.

Any suggestions on fastest way to get engine out ? Also what technique do you guys use to remove fan from engine shaft ?

I think my engine shaft has more than 0.001 runout :shock:

[Alfred]

Carefull with the numbers here Chris
I think metric/imperial is getting confused.

In metric: 1 Thou = 25.4(1 inch) / 1000 = 0.0254mm

The general consent is if you are within 2 thou or below, you are alright.
2 thou = 0.0508mm

Mine is 0.020mm and with that below 1 thou.
That is using a metric Dial Indicator as it is a finer scale.
With my imperial one, my deflection would have been less then one graduation.

[Alfred]

Have you checked your Fan to Clutch driver alignment?
I used a Feeler gauge and checked all 4 sites, this showed me that it wasn't quite right and I re-alinged. Just took 10 minutes to get it very, very close.

[Daniel Jetschin]

Tape your Sensor under the battery tray and the drift should be gone.

[sookainian]

I was very happy with the performance with my stratus today. But i also having tail drifting problem. Mine tail has a slow drifting left ( means clockwise )

I notice Chrisvau tail has a slow anticlockwise drift.

So do i have the same problem as Chrisvau since mine is drifting clockwise ?

[Daniel Jetschin]

My tail was drifting counterclockwise, after moving the sensor under the front tray, problem solved. A friend told me that many stratus fliers he knows had drifting problems and it had something to do with the stratus engine mount :dontknow but after moving the sensor part of the gyro the drift was gone. But the fan has to be balanced and dialed first.

[sookainian]

so does it mean if it drift clockwise or anti clockwise means it is cause by vibration if everthing is balance and dial ?

[chrisvau]

Ok so tonight I took frames apart and took motor out. Checked runout again before pulling fan. It was 2 thou total on my imperial guage on the top surface. Ie +/- 1 thou. I then decided to dial the inside surface where the delrin ball goes. Big shock is was over 4.5 thou.

I only have a simple dial guage which I laid on an angle to dial that surface so not sure how accurate it is doing it that way.

Which is more important ? Top surface runout of fan or area inside where delrin ball goes ?

I also then pulled fan and checked engine shaft. It barely registered on the dial so the shaft looks good.

Will try getting it on again tomorrow.

Also can anyone who installed an OS91 SZH Pumped in their Stratus tell me if they used the stock washer before the fan Collette mine is 1mm exactly.

When I put the stratus together, the gap looked spot on around .025 inches or .5mm After its maiden flights the gap is now only a few thou. I can just see light through it.

I took frames apart and could see signs of rubbing in flight so gap is too small.

I am pretty sure my kit came with new OS base plate. Can anyone with the right plate tell me how thick the base plate the engine mounts to should be ?

Best Regards
Chris

[Daniel Jetschin]

The SZ baseplate has a milled recess where the engine backplate connects to the plate to move the engine down a bit. I used the stock washer and it was fine wit the gap. The runout is critical where the uniball goes, I dialed the outside of the fan just because my indicator feeler didn´t reach the inner section when mounted on my vice and got it to 0.001 but dunno how true it is where the ball runs :roll: But my SZ crankshaft was out a few thou, too.

[chrisvau]

Well after getting a new fan, balancing it then spending 2 hours dialing it to get in to just over 1 thou runout using technique on this site, balancing tail rotor assembly, rechecking head balance and main blades, I was hopefull my tail issues woudl be sorted today. Model ran very smoothly. No visible vibration and hovered rock solid. Very tiny fuel froth but no more than I would expect.

No good! The drift is still there very small by still there that I have to keep feeding rudder every few seconds to keep it straight.

I then redit the gyro setup. Hovered in normal mode. Set tail rod arm lengh till it hovered with minimal input in normal. memorised neutral and tried again in avcs. Same issue.

I definately dont have rudder trim or program mixes or sub trim in my radio. I verified this in servo monitor Servo is at 90 degrees to tail. I am running sab 105 tail blades.

Gyro is at 38 % gain in AVCS.

I then thought stuff it and moved 611 sensor to under battery tray liek many have done to fix drift.

Same issue drift still there.

2 clicks of right trim in flight and its gone. But I know this is just masking an issue.

This is driving me blooming nuts. :arggg:

I have the best of everything in this heli and I have the Raptor 90 boys at my field laughing at me becuase my MA fancy pantsy heli cant even hover straight.

I appreciate hi performance sensitive machinery takes time to setup but I never had any of these type issues on my Raptor and I am now at a loss what to try next.


How sensitive is the model to fan balance ? I checked mine on a hi point and magnetic balancer and it was heavy on one side. I drilled it with about 5 small indents using a 1/4 bit. Fromt his point I could not get a consistent reading adn was at the limits of the quality of the balancer. Ie if I rotated the balancer shaft in the collets the balnce point would change . I figure when it gets to this point its good enough as the mass of the magnet and hi point shaft are so small that if they impact the fan balance it must be close ?

Any suggestions ?

How have you guys mounted your sensor under the tray ? Tape and metal plate and velcro ?

All that aside she flew like an F1 car on rails. I love the cyclic response and precision of this thing. And climb out rate. Yeah baby.....

This tail is tainting the love!!!!

Regards
Chris

[DavidH]

I don't use the metal plate that comes with the gyro. Unless I have to mount the sensor directly on Carbon fiber surface. I have a Tempest and the sensor mounts to the metal gyro mount rails on it. So I don't use the metal plate that comes with the GY gyros. I use 3M products 4408 double sided vinyl foam tape to mount the sensor. One layer.
This is the same foam tape that MA and ACE package and sell.

http://www.futaba-rc.com/faq/faq-gyros.html#q767

Also you might try increasing the gain some. I am using 46% gain in AVCS mode for aerobatics and 70% gain for hovering.

David

[chrisvau]

Ok Good news. My tail drift issue on Stratus is now sorted.

The cure was undoing any balancing I did on the fan by drilling same holes exactly opposite ot ones I made the first time, plus CSM thick gyro tape and mounting sensor on TOP front tray.

I used 3 strips of the thick CSM foam under the metal plate of sensor (you need 3 as they are only about 5mm wide each. I then use Futaba tape on top of metal plate to mount sensor.

With this setup tail is rock solid. Yeah baby I am now a happy boy!

Andrew Donaldson gave it a bit of a workout on Sunday with some mild 3D (Piro flips, tic tocs, hurricanes, some auto's etc...) It survived and Andrew was very pleased with how it felt. His exact words were very stable and very predictable.

I also hot started it twice in a row for about 15 seconds at about 3/4 throttle. (Yes I know I am an idiot. I had not plugged throttle servo all the way in after changing position of some electrics. fortunately I had a good grip on the blades) Anyway needless to say my clutch is now VERY well bedded in. There was black dust everywhere. Is there anything that I need to be worried about because of this ? I guess main sympton is the clutch engages a little later than it did before.

I have another strange problem that I am not sure if its related to the hot starts I did. On start up with OS91 SZ Pumped. It idles very fast and roughly for first 10 - 15 seconds, then settlles down into a nice smooth slow idle. What could cause this initial high speed idling ?


Regards
Chris Venter

[saary]

chris you have 3 strips of csm foam. and you said each is 5mm so total you have 15mm under the metal plate? and another 5mm on the top of that? :!: :?:

[chrisvau]

No I said they are 3mm wide not tall. They come in long thin strips. So you need 3 strips to cover the bottom of the base plate. Each strip is around 4mm thick (tall) so thi sis the height that the plate is off the carbon base of the battery tray.

Regards
Chris

[saary]

aha now its clear :oops: :bomb: and regard your idles. after your engine settles down try to close the fule by your hand but becaurful. and if the rpm gets very high and then the engine dies then you r runing rich but if the engine just dies then you are runing lean. but usually i think your case is normal. i hope this helps.