GY401/TREX450 (not so) QUICKIE

[kitkarsons]

Many thanks for all this info. I am currently redecorating which means I'll have to leave off for a day or two. I will have another good look at what you have said but having read through briefly it all sounds like good advice.

Thanks again.
Rich.

[kitkarsons]

Hi again moyesboy




I've reread your post and in fact, what you describe is exactly what I'm seeing: just a little bounce before the tail comes to a dead-stop.

I'm fascinated by your comments on the delay pot as there are so many conflicting opinions about this. At first I listened to the most common advice which is that if you have a fairly quick digital servo like the s9257 then you should definitely not use any delay... 'it must be zero'

But then, when I've been reading various posts that address the many tail-related problems that so many people seem to have, more & more I had been wondering whether or not a little delay wasn't exactly what I needed. Maybe the s9257 isn't as quick as I thought? Or is there another reason why this setting helps? I will definitely try it on my setup, hopefully later today. When you say 'a little' ...how much did you actually end-up using?

As it goes, while I was waiting to find a replacement for my mashed-up s9257, I tried an ACER-LAB D12-MG on the tail which I expected to give a very sluggish response to rudder input, but actually I was pleasantly suprised. This is the newer, improved version of the D12

see video:
[ame="http://www.youtube.com/watch?v=MqfD9OhseLg"]Acer-Lab D12-MG Speed Test 4.8V[/ame])

...and of course, I'm not doing anything adventurous with my heli, but it seemed to move the tail pretty well for a digital, metal-geared servo costing only 12-quid!

Going back to your post, I don't think I've seen a more comprehensive break-down on the 401. Big ta's for your help; I'll defnitely be filing this one away for future reference.

When you say...

When the 401 is first switched on (you must be in HH), and the led is flashing before going steady on, its actually looking at the rudder channel. What it sees for the rudder signal then is what it considers to be no rudder for HH. It doesn't matter what the rudder stick or trim is it will see a bit of rudder trim and consider that to be zero. This is how you can set your 401 to have assymentric end points to its travel and use the full travel of the tail pich - yet still hover straight in rate mode.

By this, do you mean by that to get the rate-mode setup we discussed, but still have your full rudder travel... you just set about 4-degrees worth of ACW sub-trim? Or am I being dense?

I did have a go at chinese-weights by using longer bolts and a couple of larger nuts on each blade holder. I didn't notice a lot of difference but then, again, I'm not pushing any envelopes so maybe that's why.

I did get a set of the KBDD's but lost them soon after in a minor knock so I don't have a clear memory of the way they performed. Have you tried the luminous ones? Pretty cheap at under a tenner I thought.

The CSM-720 looks great, there's an ebay auction on now with the current bid up to GBP 91.00. But I've seen the basic model selling new for GBP 97.00, do you really need the PC interface? In any case, until my current home is sold, I won't be paying for anything but crash repairs/spares... if at all! Good to know about it though. Would you recommend it for a larger model 600/700 or 60/90 ? At least one of these is going on my 2011 shopping list but also, alas ... post-sale. Can't wait!

Cheers again,
Rich.

P.S. Sorry to bend your ear but I've got to tell someone... I know it's only in the simulator, but after 3-weeks of daily practice I am finally managing to perform and recover from piro-flips. At the start, I couldn't even imagine being able to do it, in fact, I couldn't seem to get my head around the movement at all... visually I mean. I understood what was supposed to be happening but couldn't find a part of the heli to focus on for visual cues during the manouver. Then a couple of days ago I got that delicious click where it all just happens and now I can do it more or less at will. And the component which I find I focus on for visual feedback is the disc described by the blade holders as they rotate. This gives me the best idea of whether I'm inverted or not? Anyway... absurdly pleased with myself although I know that I'd throw an infarction if I tried it for real! Still can't imagine that one!

[kitkarsons]

End of...

Brilliant!

After the second tiny tweak of delay, probably in the region of 10 - 12.5 on the dial, my tail is as close to perfect as I've ever seen it.
Looking back, I had stupidly accepted the 25%/75% giro gain settings that my 450 Sport had when it arrived. I paid a build & setup fee and accepted these settings as optimal and have never moved very far from this supposed baseline. It turns out that I've been flying it for months now with a pre-existing handicap. The tail is so snappy now it really doesn't compare (in a good way) to what it was like before.

To recap then for anyone with similar problems:

I now have a zero-pitch tail-neutral position and my 401 is set for digital operation with gains of 11% / 73% respectively for rate & hh. This gives me a super-snappy rock steady HH tail without a hint of drift or the former wagging that was driving me so mad. Adding a delay setting of about 12.5 has removed the teeny-weeny bounce that I was seeing after any rapid rudder input.

Chuffed to bits

Thanks again to all who contributed plus a special thank you to moyesboy for the excellent description of 401 functionality and the delay tip.


Laters...
Rich.

[machasm]

Great ending.
Well done dude.

[moyesboy]

To clarify the bit about the sub trim.

you set the thing up so full left and right uses all the available movement on the pitch slider without binding.
Now the rudder centre position (which only works in rate mode) is one way or another slightly off centre (hopefully right rudder offset if they designed it right).
You then set rudder sub trim to get 4-6 degrees of right rudder pitch. Then fly it in Rate mode and tweak the sub trim so it stays straight. However now the trim makes it turn in HH mode, so you have to teach it the new stick centre for HH by rapidly switching between rate and hh several times, or by switching off and re-initialising.

Unfortunately the rate mode setting will only be accurate for whatever head speed you set up with - thats how rate mode is. There are ways to get round that by using the stick trim for your other head speeds. But to be honest most of us don't bother with rate at all and do all our flying in HH.
If you want to fly scale then Rate is useful to let it weathercock to have no sideways flight in circuits. But a lot of us want to fly sideways and backwards and revolving anyway.

For your tail servo - if you can get good performance out of a £12 servo great.
I picked up a second hand 9650, and fitted 9257 gears (an idea from trextuning, which has joined into helituning) which makes for a slightly faster 9257. However probably the best value tail servo now would be an align DS520.

I sold my 401 for a CSM720. there are a few 720s coming up for sale on her from time to time as folks start to trust their Beast3totalGVbarXs with the tail as well as their cyclics. 401s are stil worth money, because they are easy to set up for reasonable performance, so you might get to swap for a few quid on top. But until you are pulling G into backwards loops (that'll make the tail let go and spin round forwards) or trying to coordinate revolving manoevres then you don't really need the extra performance.
When you fly fast into wind and piroette you can see the heli flick round faster into wind with the 401 (Thats known as being "whippy"). with the 720 the piro speed is locked to the stick position no matter what attitude the heli is in, well, until the rotor really slows down anyway.

As regards the USB lead - you actually use them quite seldom and out of 4 helis with CSM720s I only changed the settings in 2. One just to use a fancy futaba BLS251 servo, and on my 500 I changed to stop gain to get rid a slight bounce. My 450 and 600n are on default settings.
If you buy a used 720 be sure to get the seller to set it all to default if it doesn't come with a lead (ask if its been set for a Futaba BLS251, or 9256).
If you are in a club you can probably borrow a lead of another member.

I heard next season everyone is leaving their flybars at home but taking their laptops to the flying field

[kitkarsons]

Thanks heaps mate; there's another essay for my collection of heli-wisdom!

Hopefully, by next spring I'll be the owner of a couple of new models. I'm gonna go for a larger lecky... probably another Align but this time a 500 or 600. Plus, I think I'll have a go at nitro and for that I fancy something a little more exotic. I don't take holidays nor do I have any dependants (apart from a labrador), so I've have decided on a budget of around 2K5; I should be able to squeeze a CSM720 out of that.

Cheers for now & seasonal greetings,
Rich.

[coptermanic]

Don't you just love a happy ending near Christmas..........aaahhhhh.

[moyesboy]

Soon you learn...
...most of the others here have learned to skip my excessively long posts

[Brian Gifford]

Soon you learn...
...most of the others here have learned to skip my excessively long posts

Their loss, Gordon. Excellent explanations in this thread. Thanks for the masterclass.