Pre-production Twinn-Rexx build pictures

[Gra55h0pper]

Originally Posted by MadDogDan

To reduce weight, I was going to use a lacquer that doesn't require primer or a clear coat

Saving weight is always a good thing of course. I just weighed the body: 230g. This is before the clearcoat so I think I'll come out at 300g or so for the body with the enamel primer, paint and clearcoat.

The heli itself, without body, with battery weighed in at 1470g. This means the total AUW with the body will be around 1770g or so... I don't think mine will be the lightest around...

[Gra55h0pper]

Just did a quick hover test with an AUW of 1700g (added a second battery for additional weight). Definitely not the lightest heli I've ever flown but it hovers fine and still has additional power to climb. The motor, esc and battery didn't break a sweat. Also measured my headspeed (set as per the video I posted) @ 2300rpm... . Seems a bit on the high side so I dialed it down just a little, aiming for ~2100rpm.

Now I need a (fun)scale heli meet...

[MadDogDan]

h0pper,

Did you install the flybar limiter when you installed your fuselage? I have studied the pictures on Joe's web site and even blown them up to 400% but still cant see or figure out how he installed the limiter.

Any help you could provide would be greatly appreciated,
MadDog

[Gra55h0pper]

MadDog -- I have not installed the flybar limiter (part# TW-803) at this point. I'm not sure whether I'm going to as I don't really see the need. Even though the flybar doesn't clear the rear tower when at maximum deflection, I'm fairly sure it'll never actually hit it when the rotors are at speed. I know this from people installing a Trex 600 in a Funkey MD500 fuse; the same "problem" exists there. The deflection of the flybar when the rotors are turning at rpm, really is *that* big. That said, if you decide not to install the limiter, do so at your own risk though...

To install it, you need to drill a 1mm hole in the main rotor housing approx. 3 mm above the rectangular slot the flybar goes through (which allows the flybar to "pivot"). You then need to route the supplied wire through the flybar slot and the hole you just drilled and twist/solder the wire-ends into eachother. You can use the supplied wire sleeve on the wire in the flybar slot to give it a bit of a "bumper". Now when you try to pivot the flybar, the angle it can reach will be limited by the installed wire/sleeve and it cannot hit the rear tower anymore when the body is installed.

Note: those who do not intend to fly with the body can skip this step

[Gra55h0pper]

Originally Posted by MadDogDan

On another note: After looking at this mixer board, I am going to have to call Joe on Monday to get through the physical hook up of this thing.

MadDog -- Have you seen the wiring diagram pictured here: http://www.tech-mp.com/Twinn_Rexx_docs/TR_WD.PDF?
I suggest to study it closely.

Also, make sure to read the manual on the TH-2: http://www.tech-mp.com/tandem_sw.htm

When setting things up, it's very important that you do not have any CCPM mixing enabled in your transmitter. This means that when applying a cyclic control, only one of transmitted channels should change value. The reason for this is that the CCPM mixing is done by the TH-2 (for both rotors).

Just post your questions here if you have any :wink:

[Gra55h0pper]

Flew for the first time with the fuse today! She's a bit heavier of course, but flies great!!!

Couldn't resist to post a video

Twinn Rexx RC Chinook (2 min 32 sec)

[hoot]

INCREDIBLE! Awesome Beautiful!

[joe@tech-mp]

Great video ! Looks almost scale like in FF.

What do you have stabilizing the DCP ? Looked like some FRVI during FF to hover.


Joe

www.techmodelproducts.com

[v22chap]

Way to go Grass ... first full fuse flying that I have seen ... love the grasshopper on the tial tower

[chinookmark]

Awesome! It looks even better in the air!

[billyd]

Great job gra55hopper!!!! Very stable.

What are your settings for yaw compensation? Did you do it in the TH2 or the Tx?

Thanks for posting the video, it's going to force me to paint my canopy, I am still flying the "visible human" version

[Gra55h0pper]

Originally Posted by billyd

Great job gra55hopper!!!! Very stable.

What are your settings for yaw compensation? Did you do it in the TH2 or the Tx?

Thanks Billy!
I programmed the yaw compensation in the TH2. My theory is that this way the TH2 sees any inputs given by the DCP gyro which induce yaw. The only thing is I'm not sure how much I ended up with and with the fuse on it's a little tough to check now...

[Gra55h0pper]

Originally Posted by joe@tech-mp

What do you have stabilizing the DCP ? Looked like some FRVI during FF to hover.

I have a 240 in HH mode (at 50% gain) on the DCP. The DCP channel is generated (on the heli itself in my case) at ~60% of the elevator channel.

You're right in that there is some FRVI. I don't think I had that when I flew without the body (I spent quite a bit of time on the setup) so I'm wondering whether perhaps the body makes the heli a little more sensitive to it. Perhaps it's the additional weight (the painted fuse is not light and weighs about as much as my 4S 2170 mAh LIPO) or perhaps it's related to the body "messing" with the rotor vortexes (I would expect the lift in the center to be a little less due to the fuse "being in the way" but I'm not sure exactly whether that would explain it).
Anyway, it doesn't really bother me at this point and I'll leave things as they are for now.

[MadDogDan]

For us novices what is FRVI?

MadDog

[tungym]

Drop of tail due to the rear rotor entered into the downtrust/Vortex of the front rotor. Front Rotor Vortex Interference. right?

[billyd]

Originally Posted by Gra55h0pper

Thanks Billy!
I programmed the yaw compensation in the TH2. My theory is that this way the TH2 sees any inputs given by the DCP gyro which induce yaw. The only thing is I'm not sure how much I ended up with and with the fuse on it's a little tough to check now...

Understood, but I'd love to hear the process. I don't even know where to begin.

[sokal]

hey HOPPER that was great very real looking
all u need now is a sling load

[Gra55h0pper]

Originally Posted by billyd

Understood, but I'd love to hear the process. I don't even know where to begin.

Please see the TH-2 support page on http://www.tech-mp.com/tandem_sw.htm. It's explained here how to program the TH-2 through a USB link with your computer. Assuming you've got that working, then there is a program setting called "Yaw compensation". What it does is inside the TH-2 mix DCP into yaw, i.e. when the TH-2 sees an input on the DCP it will not only output the DCP to the swatchplates but also a bit of yaw in order to counter the yaw effect which the DCP input induces.

Hope this helps -- H0pper.

[sokal]

the 47 swashplate has a 45 deg from center position
wonder if thats any thoughts on mechanics of the swash
may be they could intergrate the LCT function with the elev servo

[good2win22]

Actually, the 47 swashplate is phased 38.5 degrees off of the center position. The pitch arm on the pitch varying housing takes up the rest.


This is a fun topic with a new WOJG. It usually takes them a good while to fully understand the positioning of the fixed links/LCT's on both the forward and aft rotors.

Gotta love phase lag....