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leapfrog
05-11-2007, 04:11 AM
Joe Orlando (Tech Model Products (http://www.tech-mp.com/index.htm)) is designing a CH47 utilizing Align 450 heads, and was gracious enough to let me give a pre-production kit a whirl. Thanks Joe! (he's a class act, in my opinion)

The model is called a "Twinn Rexx", and you can see it here (http://www.tech-mp.com/twinn_rexx.htm).

This thread will document the build as I work through it... there is currently no formal manual - just build notes, schematics, and pictures. I've started a notebook of my own, and will be (have been) making a few notes of my own for future reference. There is currently no body for this kit yet, but Joe is working on that... I'm also looking for a subject ship for a scale build, and will gathering further documentation on that as I go along.

An interesting aspect of this build is that, because it's a tandem rotor machine, one rotor head turns clockwise, and the other counter-clockwise. The clockwise head (in the rear) is a standard Align head setup... nothing tricky there... but the counter-clockwise head (the front head) is also a standard Align head that requires modification for CCW rotation. It's not too bad, and in fact is pretty easy if you take some time to do it correctly.

I've already got the model mechanics pretty much done, and will be starting on the servo setup and electronics in the next few days... but don't worry... I've taken pics of the build over the last few days and will be posting them below.

Hang on... for tandem-freaks, this is gonna be a fun ride.

CHELLIE
05-11-2007, 06:28 AM
Wow that looks really complicated :) I am lucky just to get my regular heli, balanced and adjusted and flying :) , best of luck to you, Take care & have fun , Chellie

leapfrog
05-11-2007, 08:43 AM
Not too complicated.... really... just the mixing part is different from standard heli setups... Here's where I am with it now... but the build is the fun part... and is coming soon.

CHELLIE
05-11-2007, 10:04 AM
that looks nice, I have a century swift 30 size heli that I am building, I am just getting all the parts little by little, all I need now is a 6 cell lipo charger, My Triton charger just wont handle 6 cells :) and I have a shogun v2 with a brushless setup, its fun to fly, hope I can handle the 30 size heli :) It should be fun, Take care & keep up the good work, Chellie

leapfrog
05-12-2007, 08:38 AM
Here's the build: The first attachment is the overall kit as it arrived.

Okay... the build notes started with the heads... so I did too. I elected to use the gun metal gray head parts (because I think they look better - and will better fit the body when it is available). The rear head is a *standard* Align 450 head, so there is little need to cover that. I've built/rebuilt so many of them now I bet I could do it in my sleep. The front head, however, is the CCW rotating bugger... and it needs to be built in "mirror".

The easy parts of *that* endeavor are the 1. blade grips (just install them upside down), 2. the seesaw holder (just install it backwards), 3. the flybar cage - install the ball offsets backwards, and 4. the washout linkages (just pull the balls off of the swash and install them from the outside - like all Align links, the washout links are "one way" installs - Attachment #5).

The more interesting parts of a CCW conversion are the flybar control levers, and the washout base.

First the washout... the bushing is offset, as you know... and to build a "mirrored" head it needs to be installed upside down. So... I needed to press the bushing to the opposing offset. I don't have an Align bushing press (and they don't sell them, anyway). Attachment #2 is the tool I built to do that job. I took an old shaft, cut it off to length... used a sacrificial shaft collar (lock ring), an old bent flybar, and an 8-pt socket that fit around the bushing. I loaded it all in a vice (attachment #3) and preloaded it. I then used a flame-less heat gun to release the locktite... when I saw the bush move I ran the vice down to the appropriate offset (about 1mm showing). It worked great, and allowed me to just install it upside down.

Finally, the flybar control levers needed to be flipped... but when I tried it, they didn't quite fit correctly. It seems that the bearings are installed a bit offset, so I had to dress the "outside" flange (Attachment #4). I then used *both* washers on the inside and just let the screw heads capture the inner bearing race... that worked like a charm.

The rest was simple... and the last attachment shows the mirrored heads.

Weeeeeeee! Next up, the front and rear frames.

CHELLIE
05-12-2007, 09:02 AM
Well this is definatly interesting :) so i will follow your build, I always enjoy learning something new, I made a build thread on a rifle stock video camera holder if your interested, it helps to keep the planes, helis in the camera lense, I will be testing it tomorrow on my planes and get some flying videos, take care and have fun, Chellie

http://www.wattflyer.com/forums/showthread.php?t=19572

leapfrog
05-12-2007, 09:56 AM
Okay... frame build. The first attachment shows the frame parts... front and rear frame halves, center spine, drive shaft, bearing blocks, and bevel gears. Notice the edges of the frames and the holes are darkened... that's from the laser... the frames are laser cut, and I have to admit *very* precise. I didn't care too much for the residue, though... and used a bit of 180 grit sandpaper to clean them up (not necessary... but it's my heli, so I do as I please. *big grin*)

So attachment #2 shows the front frames joined with the stand-offs... both front and rear frames are built the same way... first the stand-offs... then mount to the center spine, then add the bearing blocks. I used blue locktite on the screws going into metal... and it is recommended that the parts be degreased with acetone. Attachment #3 shows the frames mounted to the center spine with the motor mount, but what is not shown (sorry didn't take a pic) is a spacer on the left side between the frame and the spine. The build notes say to use a square align the frames to the spine (parallel to the mainshaft). The tolerances of the mounting holes are tight enough that there is very little movement of the frames to the spine, and the front frames were basically square already.

Attachment #4 shows the rear frame buildup... spacers first... attachment #5 shows them joined. The rear frame attachment holes are slotted for driveshaft adjustment, but they are installed just as the front frames... with a spacer on the left side of the spine.

Next up... the bearing blocks for the main shafts and the driveshaft.

CHELLIE
05-12-2007, 06:15 PM
Okay... frame build. The first attachment shows the frame parts... front and rear frame halves, center spine, drive shaft, bearing blocks, and bevel gears. Notice the edges of the frames and the holes are darkened... that's from the laser... the frames are laser cut, and I have to admit *very* precise. I didn't care too much for the residue, though... and used a bit of 180 grit sandpaper to clean them up (not necessary... but it's my heli, so I do as I please. *big grin*)

So attachment #2 shows the front frames joined with the stand-offs... both front and rear frames are built the same way... first the stand-offs... then mount to the center spine, then add the bearing blocks. I used blue locktite on the screws going into metal... and it is recommended that the parts be degreased with acetone. Attachment #3 shows the frames mounted to the center spine with the motor mount, but what is not shown (sorry didn't take a pic) is a spacer on the left side between the frame and the spine. The build notes say to use a square align the frames to the spine (parallel to the mainshaft). The tolerances of the mounting holes are tight enough that there is very little movement of the frames to the spine, and the front frames were basically square already.

Attachment #4 shows the rear frame buildup... spacers first... attachment #5 shows them joined. The rear frame attachment holes are slotted for driveshaft adjustment, but they are installed just as the front frames... with a spacer on the left side of the spine.

Next up... the bearing blocks for the main shafts and the driveshaft.

Your smart :) I see you are using blue lock tight, Good for you, it really helps keep things together, the build is looking great, keep up the good work, Chellie

leapfrog
05-15-2007, 08:10 AM
Whoa... sorry for the break... had to visit mom for Mother's day, and I was gone for a few days... I have a pile of pics I need to process for the attachments... but I am getting to them as fast as I can...

So, let's do Bearing blocks... really simple and they pretty much put themselves together (Joe has a great kit here, great fit and finish)...

First up are the main bearing blocks (attachment #1) and they are just like any other 450 heli I've built with the bearings press-fit into the blocks and installed facing up on the top, and down on the bottom. I won't bore you with any other details because there aren't any.

Attachment #2 shows the driveshaft (DS) bearing blocks for the center spine. They are "flanged" bearings, and basically install into the blocks with a close tolerance fit, but are retained with a screw against the flange (and the screw is fixed with a bit of CA). Attachment #3 shows the assembly.

Attachment #4 shows the DS bearing blocks that attach in the frames (front and rear). They are smaller bearings that more closely fit the DS directly (the center bearings ride on spacers placed on the DS and are fixed in place by locktite 609 - the green stuff). Attachment #5 shows the assembly.

leapfrog
05-15-2007, 08:23 AM
Next up... landing gear... attachment #1 shows the gear parts, and #2 shows the gear assembly. Leave one side free to insert into the frames. The assembly is pretty simple, as the struts insert into the delrin blocks, and are retained by screws and locking nuts. The wheel assemblies are centered on shaft pins, and fixed in place... I used Zappa-Dappa-GooII, and they hold great. Notice the remaining pins in the bag after assembly. These are used to fix the gear in the frames at the proper alignment. I'll show that next.

leapfrog
05-15-2007, 09:02 AM
Now let's put the gear on the frames...

The rear gear mount to the rear frames, and utilize aluminum spacers for stiffness and geometry. I affixed one side pin guide (the outside plate you see) with the spacers and screws (locktite, of course). I then inserted the alignment pin in the strut (fixed with ZDG), and shoved it through the frames (okay, it was more finessed as the fit is very good), seating the pin in the slot. Then I inserted the other opposing alignment pin next to the frame (fixing with a bit of ZDG, again), and installed the remaining pin guide plate with the remaining screws.

The front gear install in the front DS bearing support in the same way, except that there is only one aluminum spacer.

I then attached the outside remaining gear assembly to the struts, and the gear installation is completed.

CHELLIE
05-16-2007, 03:35 AM
Its looking great, i think I would be afraid to fly it, I would hate to crash something so nice, take care & keep up the good work, Chellie

leapfrog
05-16-2007, 08:22 AM
Hehe... Actually, if I build it... it will fly. If I crash it, I'll rebuild it. I don't do hangar queens... I'm *way* past that.

It does take a bit of awareness to put a lot of time into something that may only take an instant to demolish... but it is the trip, that makes it all worth while in my book. (<-- whoa, that was almost zen-like... is someone getting this down? This is good stuff...)

Murdock1
05-16-2007, 04:33 PM
Hiya Leapfrog,

Fascinating after watching the video. This answer may be obvious to some, afraid I'm not one of them. How are the rotors kept from contacting each other?

This is really cool. So Airwolf must be taking second seat for a bit eh?

leapfrog
05-16-2007, 05:28 PM
There is a pinioned driveshaft between the two heads... actually the front head is the "driven" head by the motor... and the driveshaft then transfers power to the rear head via the miter gears. The blades are therefore "locked" at a 90-degree phase angle. You can see the configuration in the picture above (beginning of thread) that shows the mechanics basically completed.

Actually, I'm still working on "The Lady" too... I'm trying to build some decent nose gear doors... stay tuned.

Murdock1
05-16-2007, 06:28 PM
So per the specs listed there's one rx which means it must be split / doubled up between the 6 servos right? I'm assuming that the rotors respond to cyclic and collective input in tandem and that the rear rotor responds to left stick inputs for nose direction at the same time...am I close?

leapfrog
05-17-2007, 09:05 AM
Pretty stinking close, my friend. There is a "mixer" that programmatically controls the two heads depending on the RX input... (and the various gains by two gyros - one for pitch, the other for yaw). Pretty much like what I did for my wolf's gear controller - only a bit more busy. *Both* heads respond to yaw, however, the front one way, and the rear the other... not just the rear. Both heads also respond to roll (same direction), and both to pitch (one collective positive, the other negative)... this mix is called "DCP" or "Differential Collective Pitch". There is a pretty good explanation from Joe's site (copyrights apply to his content, obviously):

Tandem Control Software Flight Controls

The TH-2 provides four basic flight controls - Yaw, Pitch, Roll and Vertical ascent/decent.
These controls map to the familiar transmitter joysticks layout (mode 2).
Yaw - Left transmitter joystick LEFT/RIGHT.




Vertical ascent/decent - Left transmitter joystick UP/DOWN.

Roll - Right transmitter joystick LEFT/RIGHT.

Pitch - Right transmitter joystick UP/DOWN.
http://www.techmodelproducts.com/TH-2_manual_figures/FC_AXIS.gif
Yaw Control
The TH-2 performs yaw control by tilting the front and rear swashplates differentially along the roll axis.
http://www.techmodelproducts.com/TH-2_manual_figures/YAW_AXIS.gif

Roll Control
The TH-2 performs roll control by tilting the front and rear swashplates along the roll axis.
http://www.techmodelproducts.com/TH-2_manual_figures/roll_AXIS.gif

Vertical Ascent/Decent Control
The TH-2 performs Vertical ascent/decent control by increasing/decreasing the front and rear rotor pitch collectively (each the same).
This is known as collective pitch.
http://www.techmodelproducts.com/TH-2_manual_figures/CP_AXIS.gif

Pitch Control
The TH-2 performs performs Pitch control by increasing/decreasing the front and rear rotor pitch differentially.
This is known a Differential Collective Pitch (DCP).
It also blends in for/aft cyclic with the ratio determined by the gain settings.

http://www.techmodelproducts.com/TH-2_manual_figures/CYC_DCP_AXIS.gif

leapfrog
05-17-2007, 10:00 AM
Now, let's install the driveshaft... I assembled the front head, main gear, and miter gear assembly (attachment #1)... and left the front miter gear (and spacer) loose for reasons that will become apparent soon. I installed the assembled bearing blocks (in order) on the DS and set it in place... and then started at the front and worked my way back. There may be a better way, but that's how I did it. I installed the front miter gear to the DS, and then fixed the front frame bearing block to the frames (attachment #2). Then the front center bearing block (attachment #3). I then fixed the rear center bearing block into it's frames (attachment #4). Next up was the rear miter gear to the end of the drive shaft, and affixed the rear frame bearing block in place (attachments #5 and #6). Finally, I installed the rear head/shaft assembly into the rear frames and affixed the miter gear to that assembly (with the rear frames loose on the center spine - also attachment #5). I then worked the mesh/interaction of the four miter gears to the proper positions, and affixed the rear frames to the center spine (using a square to assure alignment of the frames to the spine). Finally, I affixed the center bearing spacers to the DS - sliding then into place - using the 609 green locktite (I think it can be seen in attachment #4) centered on the bearings...

Finally, I pushed the front mainshaft miter gear up out of the way, and aligned the two heads for proper interaction (90-degree phase), and then slid the miter gear/spacer down and affixed them to the front main shaft. With the miter gear spacers, I aligned the holes with my 2mm hex tool... and slid them into place aligning the shaft holes with the tool, also... it made inserting the fixing screws *much* easier. I also inserted the screws into the miter gears with the smooth space facing the head of the screw, and the recessed side for the lock nut (it actually allowed the nut to seat and maintained a more even spacing for balance).

Next up... the first "issue" I encountered on the build (not a big thing, though)...

Murdock1
05-17-2007, 03:52 PM
I'd bet my next paycheck or two that you're just chompin at the bit to get this bird in the air...

Keep on it this is great. It's almost like bein there. I can't wait to see the video.

Is he gonna let you hold onto this for good or will you have to send it back?

leapfrog
05-18-2007, 03:28 AM
Hehe... no bet. You're correct... And just keep checking in, I'm planning on doing the entire build here.

I'll be keeping it - I paid for it.

There are still a few "unknowns" for this bird... like what motor/pinion/bat configuration will be optimum... but I'm planning on trying a *bunch* of stuff out - and that helps him, too... so we'll see.

leapfrog
05-23-2007, 04:02 AM
I'm building this thing from Joe's kit... without formal documentation... and in looking at his prototype from the site there are a few things that he is also obviously working on... one of which is the hardware (screws/nuts) that he is planning on using for his kit. If you look at the previous pics, you'll notice that the frame screws are all 2.5mmX30mm SS slotted units, with lock nuts backing (not so with his prototype). I ran into an issue with the top main bearing blocks, and this selection of fasteners...

I attached my solution... as you can see the upper bearing block mount screws would have interfered with the "pitch" servo (on a T-rex) servo-to-swash linkages (compare with the rear bearing block fasteners in the pics)... so I dremel'd off the extra screw length screw, and used a standard 2.5mm nut (and 609 lockite) to fasten them... it works well, and will allow adequate clearance.

leapfrog
05-23-2007, 11:28 AM
Now I am humbled... Joe posted pics of this heli flying in pre-prod dress in Iraq (http://www.helifreak.com/viewtopic.php?t=39153) (built by a serviceman currently serving in Iraq)... Totally awesome.

leapfrog
05-24-2007, 04:12 AM
Okie doke... back to the build... I had to focus on another issue with my "lady" build...

I spoke with JGF, and the recommendation is that I swap the bell on my 500TH to make it a 500T (1950KV)... pretty easy change... and the result is a slower but still "torque-filled" little amp eater. I'll have to jump up in pinion size (either a 12T, 13T, or 14T) to get the headspeed, and 4S for longevity... but at least we'll be in the right range... It should run a lot cooler, too...

So for this motor at 4S:
14.8 X 1950 = 28860
-15% -4329
Motor speed = 24531
12T pinion = 12.5:1
Headspead = 1962 RPM

or 13T pinion -
11.5:1
Headspeed = 2133 RPM

and if there is more loss...
with 25% loss motor speed = 21645
and 13T pinion, headspeed = 1882 RPM

and with a 14T pinion, headspeed = 2022RPM

So there are many options... and this is a *lot* of fun to play with... I guess it's going to boil down to empirical data... and I can't wait to start playing with the *actual* numbers... and trying to figure out the loss... I have to tell you, the driveshaft is *really* free from binding once I got everything adjusted properly... it's a really free-moving pair of heads, so 15% be closer than 25% on the guess. Theory is fun to play with...

So I ordered the bell replacement for my 500TH, and also some extra pinions (I've got a lot of those, now)... so I'm ready for the fun to begin.

Whoops... but I have to finish my electronics and wiring harness build (remember, I didn't order any of the cables... I'm making my own), and I got a bit distracted. Going back to that now...

Stay tuned, all... pics are coming.

CHELLIE
05-24-2007, 05:01 AM
That was a cool video :ws: wish i could do that ;-) your build is looking great, hope to see it flying soon, take care, Chellie

leapfrog
05-24-2007, 09:42 AM
So I am knee-deep in building the wiring harness, and thought I'd show the process using the front servo extender board as an example (the front servos are powered directly from the BEC, but the signals for the servos come from the TH-2 mixer mounted at the back). The individual servo signals are brought forward by a single three-conductor servo cable... I don't know what everyone else did... but I chose black = Pitch, Red = Elevator, White = Aileron... why? Because I could remember "pitch black"... get it? "pitch black"... I kill me sometimes)

Sorry, bad pun... but it works for me and my old brain. So the attachments are:
1. get out the "kit"
2. strip the wires (I use a higher grade cable than most "pre-made" servo cables)
3. crimp the connector one-by-one
4. completed connectors (trust me, they are crimped... the wire will fail before the connection is broken)
5. shove them into the connector housing
6. Success! The completed extender... ready for sleeving!

The nice thing about building a custom harness, is that there is no "slop"... or left-over cable to bundle up somewhere. Rather makes it "neat".

leapfrog
05-27-2007, 08:22 AM
Wow... Okay she's ready for maiden. I've decided to wait till Monday - Memorial day - for her first flight in honor of our men and women currently in service... it's a really small thing - seeing as she's just a toy that I am playing wth... But Joe posted some pics of one flying under the crossed Sabres... and it really started me thinking... mine is not worth anything, compared to that one.

Every year, about this time, I think more and more of my father (I think of him daily, but on a different light). He served in WWII (I Corps) and I have some really great pics of him in a grass skirt in New Guinnea... I also have his medals, and his flag... so... I decided to put off the maiden till Monday... and just enjoy memories...

I'll be following up soon with the wiring harness build, so stay tuned as I process the pics.

Thanks to all that have served - and to those that are serving... I pray for you every night.

Frodo
05-28-2007, 12:16 AM
Wow... Okay she's ready for maiden. I've decided to wait till Monday - Memorial day - for her first flight in honor of our men and women currently in service... it's a really small thing - seeing as she's just a toy that I am playing wth... But Joe posted some pics of one flying under the crossed Sabres... and it really started me thinking... mine is not worth anything, compared to that one.

Every year, about this time, I think more and more of my father (I think of him daily, but on a different light). He served in WWII (I Corps) and I have some really great pics of him in a grass skirt in New Guinnea... I also have his medals, and his flag... so... I decided to put off the maiden till Monday... and just enjoy memories...

I'll be following up soon with the wiring harness build, so stay tuned as I process the pics.

Thanks to all that have served - and to those that are serving... I pray for you every night.

No, it is not a small thing. It is a nice tribute to your father and all who have served our country. My father served in Korea 1953-1954, he is gone as well. He died of cancer in 2004. In this case it trully is the thought that counts.

leapfrog
05-28-2007, 06:09 AM
Next up, my "sleeving made easy" 101... hehe...

The attachments show the process... I use a knitting needle that I whacked off to a manageable length... I remove the connector housing (on pre-made cables), and tape them to the needle... then it's a really simple matter of cutting the sleeve to length and sliding it on. I then secure the ends with a piece of electrical tape, and cover that with heat shrink.

The last attachment shows the harness layout board I used to build the cable lengths, and test fit prior to installing on the heli.

leapfrog
05-28-2007, 06:12 AM
Okie doke... here's another mod I made to the frames (to become clear in a sec)... I drilled some cable retaining holes (Joe *could* add these to the layout... but it's up to him, really)...

First attachment is the left side front frames, second is the right side front frames, and the last is the right side rear frames...

leapfrog
05-28-2007, 06:16 AM
Weeeeee! And now we install the sleeved servos and stuff... layout on the front is as follows:

Attachments in order:
1. Front Frames, left side
2. Front Frames, view from the left rear quarter
3. Front Frames, rear view
4. Front frames, right-rear view
5. Front frames, right side

Notice what I did with the cable retaining holes mentioned above...

leapfrog
05-28-2007, 06:31 AM
Thanks for the sentiment, Frodo. I do miss my dad - he taught me more than I will ever know.

As for this build... it truly is *nothing* compared to Sean Hayes' little birdie. I'm totally speachless by the fact that not only did he build one of these... but flew it in Iraq under the crossed sabres.... There is *nothing* that can compare to that.

We have so much to be thankful for because of the work and dedication of those like your father, my father, and Sean... and I am thankful.

Murdock1
05-29-2007, 04:37 AM
We all owe everything we do and take for granted in our daily lives to those that have been willing to go and serve and sacrifice all they had. They had and continue to have the ability and desire to respond to a call deep within themselves and because of them we are able to enjoy our daily freedoms.

Never forget them and always honor them.

leapfrog
05-29-2007, 07:05 AM
Amen, Murdock1... Amen.

And now...

SHE FLIES! WoooooooooooHoooooooooooo!

I have to admit I was a bit nervous (there is a *lot* of interaction on this thing... and trying to set it up on the bench perfectly prior to flight is really a difficult proposition)... but she spun up well, with no vibration. Just sat there with the rotors spinning through zero-degree pitch... came up to speed rather quickly, even though it is set for slow start (I'm using a RCE-BL75G ESC - and it wants more weight out there)... So I then played with the controls - cyclic first and everything seems to be moving in the right directions... aileron, elevator - whoa... the nose actually lifted on me... with the tail planted... rudder is actually a really neat check because you can *see* the rotors counter each other... so far everything is good.

So for lift off... I actually brought the nose up with elevator while adding power/pitch... and she came right up into a pretty level hover... wanted to rotate left on me... but I could counter... and added a bit of right trim until she settled down... What surprised me is that she is really a nimble little bird... *very* responsive. Collective especially seems "sensitive"... she'll pop right up on you... although she seemed to want to wander a bit in yaw on those maneuvers... I'm only using the base gain settings on the gyros (non-AVCS on either... as is suggested)... and fore/aft movement seemed to induce yaw also... I've got some trimming to do... and that series of posts will be forthcoming... but for now, it was *way* good for me. I put two bats through her... about six minutes each... and I haven't charged them yet to find out what the load was... but the ESC was basically cold after the flights... the motor was a bit warm (sorry I forgot to pack my temp gauge... so I used the "finger" method)... and the bats were warm. I'm flying my 430XL with a 10T pinion and 3S Air Thunder bats... I'm looking forward to the other motor/bat tests... I have three other motors to try, and I need to get some 4S bats to complete the testing. I even forgot my optical tach so I am clueless on what she was spinning... I guess I was just too excited to remember everything. No worries... Stay tuned.

I had a blast, and she was a bit of a handful at times... but that is what "tweaking" is all about... it looks very apparent to me that she's gonna easily be one of those "thumbs-off" type flying helis after I get done with the trimming (studying the TH-2 docs for the "constants" now).

Joe, you're a prince for letting me get my mits on her early... stay tuned... you're not gonna believe what I do with the body... *huge grin*

And now I need to process some more of the gozillion build pics to get it caught up to this point...

CHELLIE
05-29-2007, 07:49 AM
Congrads on the maiden :) I bet it was a hand full, very nice job on the build and the wiring looks very neet, take care and have fun, Chellie

Murdock1
05-30-2007, 06:23 PM
Wow...Too cool. I can't wait to see some video. Good Job Leap good job!
What do you think your total build time was?

Kai_Shiden
05-30-2007, 09:38 PM
Cool deal leapfrog, I've always loved tandems.

So when the CH47 body becomes available, are you going to go to these heads? http://flying-hobby.com/catalog/product_info.php?cPath=3_25_114&products_id=1528 (Trex size 3 blade head)

The head looks rigid, so probably the new MS Composit flexible FG blades: http://www.mscompositusa.com/gfc-main-blades-325-mm63-white.html

-Kai

leapfrog
05-31-2007, 04:09 AM
@Murdock1: hehe... it is pretty cool... I'm still tweaking a bit, and have three different motor/bat combinations to try out (and maybe more, actually). So the build continues... as for time to this point? I don't really have a clue. That is something I didn't track... I should be fired. If I had to guess (I only had an hour or so on the nights I did work on her - work and other projects shared my attention), I'd say 10-15 hours... but I've also taken my time and planned things out, and actually designed and executed a formal build plan (remember there was no documentation - and I am planning on sending my documents to Joe to help him out).

@Kai: You betcha buddy... not sure *what* heads, or what gear... but there are dual triples in this girl's future.

leapfrog
05-31-2007, 11:41 AM
Okie doke... let's continue with the details... the elevator horns don't quite center on the swash balls... and there is really only one way to fix that... get'em as close as you can. That means to grind off the standoffs... so it's back to a rig I built a *long* time ago to hold the ball ...

Attachment 1 is the rig, attachment 2 is the ball pre-ground, and attachment 3 is the ground ball.

leapfrog
05-31-2007, 11:43 AM
So we're building the horns... and the kit included the balls for the horns... the attachment screws, and that's it. But I'm a "belt and suspenders" type guy... so I wanted lock nuts... I just happen to have a supply of 2mm nuts... so this is what I finished with...

leapfrog
05-31-2007, 11:47 AM
Now... the heads are pretty much standard fare... (well, the rear head is... if you've set up an Align T-Rex 450 head... it'll be totally familiar)... but the front head - besides being CCW for the setup - it's a bit different. You use two of the standard links (and lengths... pretty much) but they are reversed in location, and you have to make up a *special* link (parts provided) to set it up.

For the front head, you use the "ele" link on the aileron servo, the aileron link on the elevator servo, and a "special" link on the pitch servo...

Here are the pics...

leapfrog
05-31-2007, 11:51 AM
I guess, the rest is the wiring harness and the layout... here's what I ended up with.

Murdock1
06-18-2007, 11:30 PM
So how's it comin Leap? My guess is you hafta just about be wrapped up by now...I'm thinkin fuse and all here. Let us know please.

leapfrog
06-20-2007, 12:08 AM
Hey Murdock!

It's going great! I guess I'm behind in posting... sorry 'bout that. The birdy has been flying great... and I did have my first crash at about the eighth or ninth bat. Very little damage, considering. She's already rebuilt... and modified a bit. I'm getting ready to start the motor testing (I have four motor/pinion/bat combinations that I want to explore).

I've been *very* busy at work lately - long hours... but I'm still finding a bit of time at night to play. I'll update the thread soon with more pics and explanations.

How've you been?

leapfrog
07-05-2007, 04:00 AM
Here is a lineup for the motor testing for this bird to come shortly... with two different ways of attacking the propulsion equation... higher RPM motors with smaller pinions... and slower RPM motors with larger pinions... I'm gonna try it all. Target head speed will remain constant at around 2000RPM, as well as the main gear... pretty much all else is going to be changed during the tests. There is another motor that I'm gonna get from Joe (as well as some 4S bats)... so there are going to be several rounds.

I'm moving my Eagle Tree FDR off my belted 600 for these tests, so we should see some emperical data... hope it is interesting.

The attached motor lineup includes a 450TH, 500T, and 500TH... (and my money - at this point - is going to be on the 500T on 4S... but that is just an opinion)

My current setup is a 3700KV 430XL on 3S and a 10T pinion... and I'm getting 7-8 mins... I'll run a set of FDR data when I get the ET moved over (and to be honest, now that I have the bird trimmed out and flying well... it's been difficult to want to change stuff... I've just been putting Air Thunders through it as fast as I've been able, and having a blast. I also have a funny story to go along with flying this thing, but that will come later).

Stay tuned...

leapfrog
07-05-2007, 04:01 AM
Interesting CH-47 side note:

A friend pointed these vids out to me... quite interesting. And they sent chills through me (you'll see why when I get the static test pics posted of how I set the tracking for each of the heads... I did it separately for each head, then a verification runup with both heads and shot bags affixed to the landing gear...)

Here is the Side View of the CH-47 Resonance test (http://www.youtube.com/watch?v=RihcJR0zvfM)
Here is the Rear View of the CH-47 Resonance test (http://www.youtube.com/watch?v=D2tHA7KmRME)

...-*sigh*-...

And I loved the old newsreel (http://www.youtube.com/watch?v=fepY4CvrYic) of it's introduction.

and the Demonstration vid (http://www.youtube.com/watch?v=k0HypHoiTV0) of it's flight characteristics.

leapfrog
07-05-2007, 04:04 AM
Okay... so I finally decided to ground the bird long enough to make some mods (and rather why I am getting behind on the build posts - I've been playing with it almost exclusively)... it's a fun bird to fly!

So... I'm swapping out the main gear that Joe provided with the new Align part... why? Because it is already machined for the FDR RPM sensor magnet (using the hall effect sensor - I use the opti on my 600)... It seems that Align got with ET for the mod because it is *perfect* for the magnet installation... (see attached)

Next up, we start the motor/bat combo trials... but I *really* need to catch up the build pics because there is a *lot* missing...

I should be fired.

leapfrog
07-05-2007, 04:07 AM
Okay... let's back up a bit (I was getting ahead of myself)... we need to center the servos individually, prior to adjusting the links. I always get it as close as I can mechanically... then fine tune. So I set the pitch curve on the TX to a flat line 50% (that's our zero point, and setting the curve keeps "accidents" from happening while working on the bird). I like to use the double arm for rexes with HS65 servos... if it's not close to level on one side, it'll be closer on the other. I then trim the unused side off and dress it... then drill out the hole 15mm from center to about 1.5mm... attach the balls, etc, etc (see the arm pics above). To complete the adjustment... we need to program the TH-2 mixer... yep, it's "comp time".

Install the "Tech Link" software first (that'' install the USB drivers necessary for the TH_2). Once done, don't fire it up... plug in the TH-2 to the USB port... and when asked for the drivers point to the driver folder (default is C:\program files\Tech Link Vx.x\driver), and let the drivers load. When complete, it'll recognize the TH-2 when it's plugged in, and the green LED on the TH-2 will light solid. Then fire up the Tech Link software. Now to initialize the TH-2 to a default, you'll have to load the constants file sent by Joe... to do that (refer to the attachments) from the main screen, select "Constants" then Load. Point to the default file, and let it load. If successful, you'll get a confirmation dialog.

leapfrog
07-05-2007, 04:09 AM
Okay... now we are at "default" settings. Time to adjust the servos individually (like adding subtrim on your TX - except you can't use subtrim unless you want to move *multiple* servos... this adjusts *each* servo individually).

So - referring to the attachments again - select "Constants - Modify"... and you get a screen with all the really cool stuff you can play with... select each servo directly and play with the settings until the servo is centered. Here is the "pooky" part... you really need to load the adjustment... disconnect the TH-2, and initialize with your TX... check the position, note the next direction/amount... unplug the TH-2 from the bat and plug it back into the comp, and repeat the process... it takes a bit of time, but patience is a virtue. To be honest, I only had two servos I had to tweak... and even then ever so slightly (I had great mechanical alignment)... so the pain wasn't so bad for me... it could have been worse.

leapfrog
07-05-2007, 04:09 AM
I also forgot... you can reverse servos if necessary... but if you set them up as shown in the previous frame pics, using right-front for pitch, left-front for aileron, and rear for elevator (on both heads) you'll be there with the default constants file from Joe.

So, now we have the servo arms centered (level)... I made a little tool that I use to get the arms perpendicular to the servo case... a gauge, really... but do what you do normally. We need to make up the links... Just use the standard Align link lengths - 31.3mm, 40.3mm and 45mm to start... the rear head is pretty much there. The front head swaps the aileron and elevator links, and the pitch link started around 69mm center-to-center.

Next up, leveling the swashes... setting the pitches, and adjusting the tracking.

leapfrog
07-05-2007, 04:10 AM
Previous post... just catching up:

POOH!

First Twinn Rexx crash tonight... very interesting... it was in a nice hover, and I was trying to learn the aileron/ele/rudder interacton by making gentle eights just in front of me. It started to "shake" (that's the best description I can come up with), and then did an uncommanded total hard right aileron and rolled in.

It was pretty spectacular... blades went *everywhere* ... but on quick inspection it seems that *both* main shafts and heads are okay... flybars are okay... but the DS has a torsion bend in the *exact* middle. All of the gears are okay... but I think there are a couple of servos that are gonna need new gearsets... very little damage for as violent as the crash was... I'm clueless as to what caused it... it was flying so well. I probably had eight or nine bats through her and was just finishing the ET installation... gonna download the data and see if there is anything there that will help.

Stay tuned. Gotta give Joe an order for a new DS and spacers... (he just shipped the 4S bats... hehe).

Well... all links are intact... and in position... I think this was electronic in nature... the TH-2 was separated (meaning the servo connections card was partially unplugged from the controller board - after the crash)... I can't be sure whether the crash caused the separation, or the separation caused the crash. Not sure I'll ever know... I relied on the heat shrink to hold those two boards together - and that was *my* fault. I was going to install a retainer, and now I will during the rebuild. And the FDR says there was no data... I have data from the previous test flight that was power only (no RPM or temp)... but this one wasn't recorded. I thought that was strange.

leapfrog
07-05-2007, 04:13 AM
So let's continue the build, shall we? I've got lots of pics I need to get posted, and now I can spend a little more time doing that. Where were we?

Oh yeah, swashes and tracking. The swashes are easy... I've personally never used a leveling tool - do as you wish... but I have calipers and a pretty level eyeball - and have done just as well. And to be honest, after having the links pre-built to the specified lengths, and the horns leveled... the swashes came out *really* close. Very little tweaking... so I'm not sure what I can add. I think I turned all three links on the front head up two turns to match the pitch with the rear... and the front pitch servo link was built to fit... but I had the same throws front and rear, and level out of the gate. My final link lengths were (measured center-to-center, if I wrote them down correctly):

Rear:
Pit = 31.5mm
Ele = 41.5mm
Ail = 45mm
Front:
Pit = 69.5mm
Ele = 46.5mm
Ail = 41.5mm

As for tracking, my blades were well balanced... and I think I had one turn on one of the front grip links (none on the rear) to make things totally track straight... well, that was on my "second" set of blades. I had a bit of difficulty with the first set. There were warp issues, and I had to set some pretty strange asymmetric adjustments... and I decided that I'd try different blades.

I went back to zero on the adjustments, and put the new blades on with the above results... and things were great (well, for at least eight or nine bats... hehe). I set the tracking individually... starting with the rear head... I used shot bags to hold the heli down for spin-up.

I then *removed* the rear blades and installed the front set. Tracking there was easily achieved by one turn of a grip link.

Finally, I reinstalled the rear blades and ran then together. They both tracked well (and I fell in love with the rotor noise). The attachments show the rear tracking setup and then the front tracking setup.

leapfrog
07-05-2007, 04:18 AM
Okie doke... she's rebuilt and ready for maiden #2...

25 points will be granted for each modification to the original setup that is called out (I don't have the FDR installed in these pics... I want to show how I set that up in a different series) ... there is no reward, other than the satisfaction of knowing you stared at a bunch of pics *way* too long.

leapfrog
07-05-2007, 04:21 AM
Another quick update, and an announcement...

The update: FDR installation... so I'm getting ready to try out several motor/pinion/bat combinations... and the best way to document the performance between them is a flight data recorder... I'm moving the Eagle Tree from my belted 600 to this bird for a while... and this is what I did to accomplish that.

First off, in addition to power - I'm going to measure rotor head speed and motor temperature. I have the hall-effect RPM sensor (I used the optical sensor on the 600 - and it's staying there), and have installed the magnet in the main gear already. That is shown in earlier posts.

To mount the sensor, I had to build a little bracket to hold it above the magnet... and this frame made that *really* easy. The first and second attachment show the bracket I built, and it is adjustable through a 3mm range. The third attachment shows the installation of the sensor (it works great... very steady RPM measurements). I taped the temp sensor to the motor, and laced the FDR to the main tube. It is a temporary arrangement - only for the motor trials... so I didn't spend any time on it at all to make it "pretty". It is *functional*... and that is the important thing.

Now for the announcement: SHE FLIES AGAIN! WoooooooooHoooooooo! (actually I already have four or five bats through her... all indoors, and rather easy... I'm just late on posting).

Funny thing... It may just be my perception, but I think she flies better now than before the crash... I can bring her up into a hover and go thumbs off... she'll basically sit there for quite a while. I did add a little expo on cyclic (about 20%), but will probably take that out. There were no other changes other than the rebuild and, of course, reset/verify all trims. I've got to get her outside where I can let the reigns out a bit (<= shameless Kansas expression).

Stay tuned. The motor trials are beginning.

leapfrog
07-05-2007, 04:22 AM
Here is the "benchmark" for the motor testing. I started with the 430XL(3700KV) motor, 10T pinion, and 3S Air Thunder bats. I'm getting 7.5 min of flight (flying to cutoff), high headspeed (too high), and low temps. See for yourself. I'm going to swap the 10T for a 9T and repeat for this motor... and then pick one of the other setups and just keep going... watch for more data as I continue.

BTW, this heli is *really* fun to fly... and here is the "funny" thing I mentioned in a way earlier post - it seems that I watch the head of my helis when I fly them - in addition to the frame (I feel it telegraphs what the heli is about to do). Well, I'm having to *unlearn* that... hehe... it really doesn't work at all with this heli, and I've found myself a bit behind it at times because of it. Still, I've had no problems with the flights so far... and have taken 10% of the expo out (down to 10% total)... I'll probably take the rest out pretty soon... I like the responsiveness... and this heli has it.

leapfrog
07-05-2007, 04:24 AM
And here is the first full motor test (I decided that since I had the 9T installed on this motor already, I'd revisit the 430XL later).

First up - The Just Go Fly 450TH...

It's specifications:
Outrunner @ 3000KV
250-300W
7.4-14.8V
55gm

I think this is "the little motor that could"... and don't let it's size fool you. Very nice performance (as you can see below). My personal feeling is that I would probably settle on 10T and 3S.

It is *really* scale-like at 9T/3S with the slower headspeed... but I would change my throttle and pitch curves to support a 90-100% throttle at hover and up (I am using the same curves for all tests to just keep as many variables constant - and I'm just holding hovers for the *entire* test flights). There is also the possibility for rotor stall in this configuration if one was a bit sloppy with collective management (like I am). The bird actually "feels" heavier on the sticks and is pretty docile, but you have to stay ahead of it. The time aloft was really great, though. *big smile*

The 10T/3S configuration has a little more headspeed, and a broader envelope. It is more responsive on the sticks, and became a bit more "stable" (my subjective opinion). She pretty much just sat there in hover... happily swaying away with my inputs. The time aloft was a bit shorter, but not so much as to penalize the configuration.

The 11T/3S and 9T/4S were really too high on headspeed... and the bird was *really* touchy... almost twitchy (you can even see a little bobble in the 4S graph up front where I over-controlled a bit, but gathered it up).

So that's it for the 450TH... now I need to pick another (I still have the 430L, 430XL w/9T, the 500TH, and 500T motors to try).

leapfrog
07-05-2007, 04:26 AM
Here are the Align 430L (3550KV) tests... and an observation.

It's specifications:
Outrunner @ 3550KV (yep, it's an outrunner)
200-300W
7.4-14.8V
58gm

This is probably the most common T-Rex motor out there (well... by Align's specs, anyway)... it's a great little motor, as I have several of them and have yet had a problem with one. I've got one that has way over 300 flights on it... and it still pulls like it was new.

Now, for the observation... check out the motor pic... see that white dust everywhere? That's the main gear... it seems I hurt it with the 9T runs... I mic'd the 9T gear and it is *way* out of round (not surprising, as it is one that I machined from a 2.3mm stock pinion)... and it has been on four different motors now. I've had good luck with machining them out, as long as I don't disturb them once setup. They (like every other pinion) will take a set and run fairly true if you don't mess with them. Being bounced between the motors probably weakened the walls - and the differential tightening of the set screw probably made it worse. I tossed it.

I checked out the main gear under a 12X glass... and the face/flank radius has been worn severely (the pitch circle has increased in diameter). The teeth are pretty much triangular with flat faces. Not good, for lash... if you know what I mean. No worries... it's the "new" type gear, and I can replace it easily without messing with the hub/one-way bearing setup. I'll do that before continuing with the motor testing.

Anyway... I also attached the results. Stay tuned for more.