Twinn Rexx owners' thread

[billyd]

Thanks chinookmark. Yes I realize that, and I certainly wasn't expecting the tail authority of a standard tail rotor. But I was just wondering if there were settings you could play with in the TH2 (which at this point in my small experience is a black box) or the gyro. I already have -30% expo in the rudder per the instructions. It's going to be a long time and take alot of studying on my part before the TH2 becomes something I will feel comfortable playing with. Just looking for some cheap expert advice, but as an early adopter it looks like I will have to experiment until we get some guru's posting their ideas. I also need to create an elevator-rudder mix in my Tx which I haven't gotten to yet. Joe mentioned the TH2 could do that as well, but I haven't a clue how to do that.

Regarding the power wires, I think it's a good idea to follow Joe's advice. Like you said he's spent alot of time on this beauty. Besides it's a piece of cake to do. I simply created a "Hydra" type power cable that attached to the bec output. Sent one part to the receiver, one part to the TH2 and the final part to the extender board. Took about 10 minutes to make the cable. With as much wiring as there is on this baby, and all the back and forth comms going on between the components, it's not hard to imagine a glitch interrupting power to something which could lead to a very expensive crash.

[SoupZ]

SoupZ

On the TH-2 you might get by with just power from the aileron channel, but I'm not going to try, and I wouldn't recommend you to either. The TH-2 has been out for a while, and Joe has been testing the Twin Rex for over a year, so I imagine he has good reason for recommending the extra power wires.

As for the extender board, it needs it's own power lead. The wires that connect the TH-2 to the extender board are signal wires only.
oic...thks mark,:lol:i'll go look at the wiring diagram agn:YeaBaby:

[v22chap]

billyd
I don't know what to change in the TH-2 for rudder help ,,haven't got that far my self .. I actually have moved my rudder expo back to -16 .....and seem to like it there ... I aggree with chmark that probably more ATV on it might do the trick .

on the mix ,,it should have mix 1 input , mix 1 output and mix 1 percent ... if I remember right and you just put in the numbers that correspond with the channel you want to mix and the percentage of mix ,, save the constants and you have a mix .
The elevator to rudder mix is only needed for when you start doing prolonged forward flight to counter the yaw effect that prolonged elevator control will have on the bird .

[joe@tech-mp]

Not much can be done to speed up the rudder response other than increasing the cyclic response of the rotor discs. The only options are to use larger flybar paddles and/or increase head speed. Head speeds over 2K can cause problems since vibration goes up with heads peed as well.

I would like to see some experiments carried out to get the yaw channel gyro working in HH mode. Some of the early test pilots were going try the GY401 delay function but it never got done (that I know of).
Any experimenters out there?

It would be icing on the cake if we could get this working.


Joe

www.techmodelproducts.com

[billyd]

I am having an interesting issue. When I turn off hh on the dcp gyro, the heli lifts off evenly with both rotors in plane, but when I engage hh and lift off the front rotor is coming up ahead of the rear (just a small amount, it is flyable).

Essentially there is more lift in the forward rotor with DCP HH engaged than without. It's a small diffference and can be trimmed out, but then I also have to trim agains the yaw as well. I end up chasing the trims back and forth.

[joe@tech-mp]

Remember in HH mode, the gyro will track the stick movements (elevator) resulting in an offset. If you re-initialize the gyro and don't touch the elevator stick until lift-off, the offest should be zero.

Try it as an exercise. This assumes the bird is properly lift balanced.


Joe

www.techmodelproducts.com

[v22chap]

I have an extra 401 laying around and will try to play with it a little to see what I can find out .:happyd

[chinookmark]

Heading hold on the DCP seems to have some interesting effects. Play with the elevator control while the blades are stopped. If you hold forward stick, the forward swash will drop, and stay low, even after you release the stick. Same is true in reverse, if you hold back stick, the forward swash will rise, and stay there. If you play around a bit, you can control how the helicopter takes off. If you hold some forward stick before you lift off, the helicopter will pick up it's tail wheels first, and by holding just a little aft stick, you will stop the heli from creeping forward while it dips it's nose towards the ground. Again in reverse, if you hold some aft stick in before liftoff, you can balance on the rear wheels. Playing with the elevator and thrust, I can make the heli perform a pretty realistic looking taxi.

As for the elevator - yaw mix, I took mine out. I might try again in the future, but I always ended up making the mix too strong. I find it actually kind of fun to have to steer it as much as I do, especially since it's so stable in the other directions.

[rdlohr]

Post some more footage. That thing is way cool!

Rick

[chinookmark]

What a heli-freakin' day! I let a friend of mine - a fellow flight engineer - fly the Twinn today. Even with a clear body, that thing is soo cool to watch just lazily float around. The huge grin on his face made me think there's a Twinn Rexx in his future. He handed it back to me, and strangely, it wouldn't start.

Long story short ... For what ever reason, I burned out the motor and speed control. I swapped in the RCT-FM450 motor (3500kv) and RCT-40A(S) (aka Guard 40) ESC from my yet unfinished Diablo. 11T pinion, and dropped the throttle curve from 0-75-85 to 0-50-60, and believe it or not, the thing flies pretty darn good. Obviously, running a 50% throttle curve, it's not the ideal setup, but it got me in the air.

Actually, it was flying so well, I started doing a pinnacle landing on a large 4" thick foam block. Goaded on by the other FE's, it turned into a slope landing. Before you know it, I'm doing left, right, up, and down slope landings on one of those floor safey wire covers, and pinnacle landings on toolboxes and actual Chinooks. This helicopter is awesome. It is definately getting a cargo hook.

[chinookmark]

Post some more footage. That thing is way cool!

Rick

I got some cell phone footage today, but I haven't been able to get it off my phone yet. I will definately get some videos up in the near future.

[chinookmark]

I would like to see some experiments carried out to get the yaw channel gyro working in HH mode. Some of the early test pilots were going try the GY401 delay function but it never got done (that I know of).
Any experimenters out there?



Since I turned my Diablo into a hangar queen today, I'll rip the RCT-G730 gyro off and try it out. I haven't used it at all yet, so it kind of throws the scientific method out the window, but it's suppose to function very similar to a 401.

[chinookmark]

By the way I am using the 500t motor and 35 amp castle creations speed controller and the 4s 2200 mah battery and I am pulling about 8.35 amps at hover. I put the power monitor on it tonight just to see. Figured I'd post it here for anyone interested. The power monitor adds a little weight so maybe without it that number drops a little, but then again I'm flying without the canopy so it's probably about a wash there.



What pinion are you using, and what do your pitch and throttle curves look like?

[billyd]

12 tooth pinion. Right now the throttle curve is just the basic 0 25 50 75 100, (don't forget I just got this flying two days ago so it's still pretty stock). The pitch curve is 46 48 50 66 82 (that gives me -4 and +8 at the extremes per Joe). I haven't set an idle up yet, lol, I don't think I'll be flying 3d with this one. (Although I'm sure you could do it).

I am going to switch over to governer mode when I get the chance to tach the blades and set up the esc (hopefully this weekend).

ps. chinook I've been doing that as well. I was able to taxi down my driveway yesterday. Can't do that with a Trex !!! This heli really draws alot of looks. I do my test flying on my front lawn and the neighbors usually don't even stop to look up from their walks. But both times I brought out the REXX I've drawn a small crowd. People are amazed at the design. My wife couldn't care less about my Heli's but she has come out to watch it fly every time. That's a huge endorsement.

Pss I find when I stabilize the heli on takeoff then the yaw kicks in so I have to pull back with the elevator and push right rudder to take off straight. But then I fight the gyros for awhile till she settles in. I'm still learning how to fly the tandem, I have a tendancy to over control it right now. I'm not used to the scale behavior of the "tail". But I am getting better. I think when I get it set to governer mode she will behave alot better (I think my rpms are too low at hover right now). My job is in the way for now. The weekend can't get here fast enough.

[chinookmark]

I've got a -4 0 +8 pitch curve, too. I suggest going to more of a plateau type throttle curve. IE: 0-65-70-75-80. That way you have a more consistent RPM to work with, and you're not dropping RPM in a decent. I tried a flat curve (0-70-70-70-70), but it just doesn't sound scale, since it spins faster at flat pitch than in a hover. I like the way the heli just purrs along with a nice low headspeed. I cranked it up to 90%, and it flew fine, but the sound just wasn't becoming of the Twinn Rexx.

I don't have any experience with governor mode. I will be setting up and using idle up when I start flying outside. I never use normal mode outside -- I don't want to worry about loosing power when I'm fighting the wind. The one time I flew the twin outside, it felt like a feather -- the wind just wanted to pick it up and move it around. It was a little wierd, but that was before I set heading hold on the DCP. I think it might be signifigantly better with HH.

[billyd]

Well governer mode is excellent, except you do have to set up a flat throttle curve. Typically between 70 and 85 is the number in throttle curve, depending on what headspeed you want and the capability of your esc and battery.

The huge advantage of governer mode is your head speed remains constant regardless of pitch, so you can dial in the best rpm and your bird flies the same throughout the pitch curve (stability wise). In our case we just have to pick the right pinion and use fixed end point mode to find around 1900 to 2000 rpm with a tach and then use that number for our pitch curve in governer mode. Finless has videos on setting up a castle 85 for governer and it's all pretty much the same procedure.

Regarding stock sound, you can always set up a slow start and cutoff and disable the brake. To use it in governer mode you just spool up at 0 pitch (mid throttle) until the head speed levels off and then takeoff.

[v22chap]

Just did a couple flights with the 401 on rudder augmentation in HH ... also full delay and it seems to work great in hover anyway and it stops the hunting rudder problem . I am going to do a little more testing with it ...but doubt that I will get any forward flight as we are suppose to get snow again tonight and it is just to cold for this old man to fight the elements to fly outside ....the garage is bad enough :thumbup:

I will start bringing the delay down to see what happens and how far down it can come .Waiting for batteries to charge again.
Also had to put my last XPS 2.4 8 ch RX on it to get enough channels to do the remote for the 401 and it seems to work great with the TH-2 also

[Gra55h0pper]

v22chap ... That's good data! Eager to hear more about your experiences with a 401. As far as I know you're the first one to report experiences using another gyro than the 240 and since the heli is plenty stable in the elevator and aileron planes, the rudder deserves most attention! Let us know once you've got some forward flight experience. I may be switching myself to a 401 also as I figure that shouldn't it help, it shouldn't hurt either.

[v22chap]

Two more hoops with the 401 ... this time I run the delay down to 50 ...was still o.k. and the next pack down to 25 and still o.k. Next up will be o delay ... not sure what will happen ,,, any body got an idea ???

I suspect that it will only happen in forward flight and wind conditions ??!!!:shock:

I think that it will be an osolation much like a to high of gain on the tail rotor ...but not sure ??
I only have the gain set up to 38 ... I may move that up too.

All I know is it doesn't happen moving back and forth across the garage nor if I make a sudden tail turn .The only thing I am noticing is when it initializes ,,,sometimes it takes about 2 or 3 beeps to find it and it pulls the cyclic down pretty far .

[speedy2007]

I had been flying about one year non stop till I had family emergecies, and had to sell my helis. Things are getting better and I would like to get back into the hobby; my question is would I be making a mistake buying the Twinn Rexx as my next heli, or do you guys think I would be ok? Im not into the 3D flying I mostly like scale. Hope some one could answer my question. I really want one of these.

Thanks

[v22chap]

Speedy ,,, what did you fly for that yr??? And how good were you ... can you do nose in hover and forward flight yet ?
If you can do that without crashing with a trex size or larger bird ,, I think you could handle the twin . It is just a question then of can you handle the expense and the expense of a twin rotor crash (double the blades and main head parts ) :bawl

[speedy2007]

I started with a Raptor .50, sold that heli and got a Fury Extreme .90. Only had two crashes, one was due to tail servo malfunction. My second crash was all pilot error. My foward flight was decent, I think it could be better.

[v22chap]

Sounds to me like you can probably handle it ... go for it ..:thumbup:

[billyd]

Just finished setting up governer. I have a castle creations 35 amp esc and 12t pinion, with the 500t motor.

I have the throttle curve at 79.5% flat and get 1938 rpm. At 80% I am at 1978 rpm, but I want to stay closer to 1900 rpm. I didn't like the sound of the blades at 2000 rpm. Unfortunately I ran out of daylight before I could really flight test it, but it feels alot better already.

Speedy, the twinn rexx is a blast and a great kit. It's not that hard to fly, but you can certainly lose it. It handles like a big bus, so you can't get too silly with it. But it looks fantastic in the air, very scale looking. I think you will want to get a regualar trex as well so when you want to fly for speed and agility you will have that. Think of the twinn rexx as a big luxury car and the regular 450 trex as a 2 seater. There's a time and a place to enjoy both rides. The tandem certainly tests your flight skills, not so much from a reaction standpoint but rather keeping her in control and on course while moving quickly. FFF is very tricky.

[chinookmark]

Hey speedy,
The Twinn Rexx is both easier and more work to fly than a regular 'rex, if that makes any sense. You have to work the rudder more, but it just kind of floats around. Like billyd, I recommend a regular Trex/Diablo/CopterX to go with it. You can do your warmup and try new stuff to keep yourself sharp on the standard 450, then fly the Twinn when you want that challenge. It's kind of like owning a project muscle car ... it's awesome, but you need that daily driver to beat on.