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Twinn Rexx
Twinn Rexx Tandem development page
The Twinn Rexx is a mini tandem
helicopter designed to use the very popular T-Rex rotor heads and
drive components.
The goal is to make it fly with the most 3D capability as possible
that is inherent with the tandem configuration.
Flight tests are under way and we will soon see what the true
capabilities of this machine will be... Stay tuned...
Also, the model is designed to give a sport scale CH47 Chinook
appearance with special attention given to the accessibility
of
the internal subsystems by way of a main hatch that operates like
the the cargo doors on the US space shuttle.
Below is the CAD drawing and prototype pictures of the model.
Twinn Rexx CAD Drawing
Twinn Rexx Prototype Setup/Specs
| Motor (initial) |
Align 430L (just for
initial testing) with 11T; 10 to 12 min flights with 3S
2100 |
|
| Motor (now) |
Medusa 028-040-2500 with
11T pinion; 8 to 9 min flights with 4S 2070 |
Updated 4-15-07 |
| ESC |
Align 35A w/Tech Ferrite
Ring Glitch Filter |
Updated 4-15-07 |
| Battery |
TP 4S1P 2070 MAH 25C |
Updated 4-15-07 |
| Servos |
6 HS65HB |
|
| Receiver |
Futaba R146ip |
Updated 4-15-07 |
| Antenna |
Tech Micro Antenna |
|
| Battery Monitor |
Tech LGG-1 Li-Poly Battery
Monitor |
|
| Yaw Axis Gyro |
Futaba GY240 (AVCS off) |
|
| Pitch Axis Gyro |
Futaba GY240 (AVCS on) DCP
Channel |
|
| BEC |
3.5amp Capacity at 5
Volts; Medusa MR-BEC-45035 |
|
| Controller |
Tech TH-2 (Tandem SW
Version 2B005) |
|
| Rotor heads |
Stock Align 450 XL TRex
|
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| Main gear |
Stock Align 450 XL TRex
|
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| Blades |
Tech 325mm High
Performance Blades |
|
| Rear Main Shaft |
Stock Align 450 XL TRex |
|
| Bearings |
Tech High Performance
Bearings |
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| Front Main Shaft |
Tech Model Products |
|
| Driveshaft |
Tech 5mm Hollow Stainless Steel
(Courtesy of Walt Ferar) |
|
| Main frames |
0.062 LASER cut G10
Walt Farrels LASER Cutting Service |
Updated 9-16-06 |
| Shaft to Shaft Distance |
20.25 inches |
|
Here are some pictures of the initial mockup/prototype.
Walt Farrels LASER Cutting Service
Here are pictures of the flying prototype (click on
the pic).
July 4th Update - First Flights
All things finally came together and we were
able to get this bird in the air. A stock TRex 430LF motor was used since
the motor of
choice is backordered 3+ weeks now. Initial flight tests were smooth
and rock solid as expected. On the third flight, the AVCS
(Heading hold) was turned on for the pitch axis gyro and WOW !!!
what a difference. Super stable. The sound of the rotors
wapping
the air is just awesome. Flight testing will continue and the
parameters will be tweaked to get maximum performance. This is the fun
part :)
August 4th Update - Flight Testing Continues
This helicopter is a real pleasure to fly.
It is super stable and rock solid.
We still have a stock TRex 430LF motor for now as we are trying solve a
ground resonance problem
More info
The two gyros are picking up vibrations right
near the lift-off RPM which causes the problem to get worse.
Once airborne everything is smooth.
The weather here has been either raining, windy or to hot to fly so
testing took a back seat for a while.
This
next month should be more productive.
September 16th Update - Flight Testing Continues
I recently re-designed
the main frame with new sides. I beefed them up and changed to a thicker
material (0.062).
The frame is very solid now. The lighter frame allowed for flexing which
was causing a resonance problem.
A new problem developed though. There was a small vibration that was being
picked up by the yaw gyro.
This in turn caused havoc on the main rotors which amplified the effects.
The vibration amplitude increased with rpm
which suggested it was coming from the rotor(s).
I ordered a sensitive accelerometer sensor (+/- 1.5G) that I mounted to
the frame. It allowed me to measure the vibration amplitude and
frequency
(with an oscilloscope). I used it as a guide to find the vibration
source. I simply began removing rotor components until I had the
culprit red handed.
It turned out to be the
front rotor flybar which was slightly off center. I had rebuilt the
front rotor head when changing the frame sides.
I did this late at night when apparently too tired. A minor thing
like this can be a source of much larger problems.
The heli now flies like a dream and is rock solid. It is hard to
describe how realistic it is and the sound the rotors make especially from
the area where they overlap. It has that characteristic "wapping"
sound the full scale birds make.
I am still using the
stock Align 3550KV motor with a 3S 2100 battery. Flights are about 8
or 9 minutes with gentile flying.
We have an AON 4S motor on order and are waiting for it to come in.
It can handle 400 to 500 watts which should really get this bird moving.
Here are the latest pictures with the new frame (click on
the pic).
October 23rd Update - Flight Testing Continues
The weather has been either windy or raining
lately. We are now looking at kits becoming available late spring or
early summer 2007.
There will be a number of choices: Partial kits to full kits in both
metal and plastic versions.
The final power system is still under development (weather permitting) but
will most likely use a 4S battery and motors from AON or Medusa.
The design of the Twinn Rexx frame and mechanicals are pretty much
finalized and tested.
The CH47 body mold construction is underway.
Here is the latest video.
Note: It has been moved to a different
server. Update your links.
January 3rd Update - Flight Testing Continues
We now have 3 test pilots flying and testing
the Twinn Rexx.
The 4S power system is much more powerful than
the previous 3S motor.
I had to add a second drive shaft support since it was flexing too much
and I believe it was responsible for some torsional resonance problems.
We recently received the new laser cut parts to begin testing. See
the pics below
A new version of TH-2 software is being tested
as well. It now has a digital filter on the rudder channel that
filters out high frequency vibration induced noise
from the gyro. The filter has 4 settings - off, low, medium and
high.
Looks like summer 2007 for a release. No exact date yet. Base kits without
the rotor heads will run $250 to $275 (estimated).
Plastic rotor heads will run around $175 and metal heads around $300.
No electronics/electrics included.
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Latest CAD Drawing |
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Twinn Rexx Surgery |
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New Drive Shaft Dual Supports |
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April 4th Update - Flight Testing Continues
We now have 6 test pilots flying and testing
the Twinn Rexx.
The motor mounts have entered production.
They will be stamped (CNC punch) from 0.074" stainless steel plate.
The users/assembly manual has been started and
gets attention as time permits. Not much has been done on it
lately.
The CH47 body plugs are in the process of
being machined (CNC). This will produce two plugs (left and right)
which will be used to make a set of
master rubber molds (female). The master molds will be used to make
the production molds from an aluminum filled epoxy. We will try to
get
some pictures of this process.
June 8th Update - Flight Testing Continues
The motor mounts are completed. They
were laser cut from 0.074" stainless steel plate and formed in a brake.
A great job done by
the Milford Fabricating
Company
The CH47 body plugs are completed. The
engine plugs are in the works and are expected to be ready in a few weeks.
The next step is to drop the plugs off at our local vacuum forming shop to
get some test bodies made. The goal is to
find the right material and thickness which provides the lightest weight
and best strength.
Here are the latest pictures of the body plugs (click on
the pic).
The body and engine plugs were fabricated by
master model builder Butch Sickels at
RS Models.
There are a number of interesting Twinn Rexx
threads on various forums listed below:
Twinn Rexx pics from IRAQ
HeliFreak.com Pre-production Twinn-Rexx build pictures
August 25th Update - Flight Testing Continues
We currently don't have a release date.
We expect it to be later this year.
We finally got the test bodies delivered.
They came out great and the plugs won't need any modifications.
The mounting system for the body to frame is still in the design process.
So far, it looks like it will be light and simple..
The engines are on hold right now (Butch had
to stop work on them) and will be offered later as a separate kit.
The servos will need to be mounted differently
than shown in the pics so far. Most will need to be mounted so the
flange
is on the inside of the frame sides. The rear "E" servo has been
relocated into the body cavity. The rear tower just doesn't
have enough clearance. The existing mounting hole is still provided
and can be used without the body.
Trimming the body from the molded sheet was
easy with a #16 blade. The wide blade allows you to use the body as
a guide.
Here are the latest pictures of the body (click on
the pic).
Note: The body is only taped on and is not
in the exact scale position yet.
November 4th Update - Kits will be rolling out
this month Updated 3-23-08
Twinn Rexx kits will begin rolling out later
this month. Those on our waiting list will be contacted first.
It may take a while before all of these commitments are satisfied.
We will do our best.
CH47 body kits are now in stock
CH47
Body
The Twinn Rexx support page is up and running.
New info is being added regularly.
Twinn Rexx support page
The Twinn Rexx parts page is up and running.
Twinn Rexx parts page
Huge amount of info on the latest Twinn Rexx
Builds etc.
HeliFreak Tandem Forum
April 4th 2008 Update - Kits have be rolling out
Twinn Rexx kits have been rolling out and more
are taking to the sky each week.
There are a number of great videos, build info
etc. up on the Helifreak tandem forum
http://www.helifreak.com/forumdisplay.php?f=70
We are currently working on a 3-blade head for
the Twinn Rexx. It will be articulated with feathering spindles and
dampers.
It has been designed using CAD and we are currently building a prototype
to begin the testing phase. There is no release date at this time.
The goal for the head design is to make it perform as best possible and to
be affordable. Also, it must be repairable/maintainable.
We are holding back on photos/drawings at this time due to our unique
design.
We are also considering producing a CH46
tandem down the road. The decision to do this depends mostly on
economic factors.
If it's worthwhile then we will do it.
Dec 19th 2008 Update
No big news to report this time. More
motor trials are in the works
Reviews of the Twinn Rexx and TH-2 by RC-Heli
magazine have been published recently. These articles are available
below.
Twinn Rexx
RC-Heli Review
TH-2
RC-Heli Review
(added 3-05-08)
Jan 2nd 2010 Update
No big news to report this time. The
economy has taken it's toll on sales.
Currently all efforts towards 3-blade heads and the CH46 model have been
suspended until things improve.
More to come. Stay tuned....
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Products LLC. • All Rights Reserved |
