dragon_not_fly
Heliman
Location: US
My Posts This: Topic Forum | The straw that broke the camel's backIn this post I am going to look at the nitty
gritty performance pluses and minuses with my
current flying setup in regards to flight time.
In a recent above post, I posted my entire
flying components, particulary the addition of
a Feigao brushless tail motor, a Castle Creations
Phoenix-10 brushless ESC that has NO internal
mixing in it and the use of a computerized heli-
copter radio transmitter, namely, the Futaba T7CHP.
In my current setup, I MUST use the Futaba trans-
mitter's internal REVO-mix capability, since the
Castle Creations Phoenix-10 brushless ESC has no
mixing capability and I am NOT using an AVCS system
(Heading Hold or tail lock gyro), but a rate/gain
gyro, the GWS PG-03 gyro. In previous posts before,
I used to fly with a BRUSHED tail setup, namely, a
STOCK Colco Thunderbird II tail motor, a STOCK ESky
HoneyBee tail rotor, a STOCK Walkera tail rotor drive
gear and shaft using a GWS GWT-4A II FM 4 channel
non-computerized transmitter with the ESky 7-cell
8.4 volt STOCK NiMH 700 MAh battery pack, ESky re-
placement part number: EBT024 and was able to main-
tain hovering power for 8 full minutes. I define
hovering power as this: the ability of an r/c heli-
copter to maintain a certain steady altitude typically
chest high above ground over a small spot on the ground
for as long as possible where either the heli runs out
of gas or the charge of the onboard flight battery pack
runs down such that the helicopter drifts down to the
ground if the helicopter is electric powered for the
very first time in the flight. With the aforementioned
BRUSHED setup I used to fly with, I was able to main-
tain hovering power for exactly 8 minutes, then for the
very first time the helicopter would slowly drift down
to the ground and be only able to maintain a hover about
4 inches above ground even at full throttle stick de-
flection. With the brushless DIRECT DRIVE setup, I have
witnessed some very interesting flight times using NiMH
battery chemistry based flight packs. For instance, my
original Walkera kit came with a 7-cell 650 MAh NiMH
flight pack, in my current setup, it can not even lift
the helicopter off of the ground! I could not believe
my eyes, with that battery my aforementioned brushless
setup was dead in the water, even at FULL throttle stick
deflection and with a full charge on that stock 650 MAh
pack, the helicopter could only pop off of the ground as
high as a foot, then it would sink right back down onto
the ground. Simply put, it was useless. Next I tried the
aforementioned ESky EBT024 7-cell NiMH 700 MAh pack and
was able to take off and fly, but I had some very inter-
esting flight times. If I used the stock 700 MAh battery
pack, the EBT024, WITHOUT the helicopter's cabin or can-
opy, not only was the helicopter able to get off of the
ground, but I was able to maintain hovering power for
4 minutes 32 seconds, where right at this point, even at
FULL throttle stick deflection, the heli drifted down into
a sightly less than waist high hover. I let the heli-
copter sit on the ground for a few minutes, then I took
off again, I was then able to maintain hovering power
for 1 minute 56 seconds, right at this point, even with
FULL throttle stick deflection, the heli drifted to waist
level and then below this. I did this two more times and
the first time could manage only 31 seconds, the second
time was at 46 seconds. After this the helicopter would
just manage a 4 inch hover above the ground, so I just
held the heli on the ground and ran the charge down. My
guess is for this never before seen flight duration pro-
blem is due to two things, weight and INCREASED current
draw from the Feigao brushless tail motor/GWS 4530 tail
rotor DIRECT DRIVE setup. These two things, really, the
DIRECT DRIVE tail setup was the straw that broke the cam-
el's back. To make things clear, the 650 MAh 7-cell battery
that came with the original kit flew my BRUSHED tail setup
fine using TREC and a Colco Thunderbird II stock DC tail
motor, while the 700 MAh packs were also able to fly the
helicopter for up to a full 8 minute hover. To make matters
worse, if I placed on a Century Hummingbird canopy that I
trimmed to fit the Walkera #4, I could only manage a 2 minute
hovering power duration and within that time frame there were
two occasions where I needed FULL throttle stick deflection
to maintain a waist high hover, then a few seconds later, the
heli could rise above head high. The lack of hovering power
duration problem was again painfully present. No matter what
I did I could not achieve more than 4 and one half minutes
of hovering power WITHOUT a canopy or cabin on the helicopter
using the new brushless setup and the stock ESky EBT024 7-cell
8.4 volt 700 MAh NiMH batteries. Needless to say, I was com-
pletely caught off guard on this and thought that going to a
brushless tail with DIRECT DRIVE would not have been so diff-
icult. After being stumped and NOT having ANY LiPO flight
packs lying around my house as I still do not use them, I de-
cided to make a small risky purchase for an 8-cell HIGH QUALITY
flight pack, since my guess to this problem was the direct drive
setup was causing the Feigao brushless tail motor to spin so fast
that it was "guzzling" electricity, such that, it was demanding
such a relatively high amperage request from the flight pack, that
the ESky packs could only maintain this for about 4 minutes of
actual flight time or hovering power. So, I ordered a Great Planes
Electrify 8-cell 650 MAh NiMH "stick" pack from Tower Hobbies and
waited for it to come in the mail. When I got the new pack in it
was tricky fitting it into the frame of the helicopter, I got it
in, did ground and air runs to get the REVO-mix to within working
parameters of: HI @ -30% and LO @ -70%. After 3 days of this, the
heli was ready for hovering power endurance tests. I made the flight
with the cabin or canopy that came with the Walkera "bare bones" kit
and the new 8 cell battery. I was able to maintain hovering power
for 4 minutes 52 seconds, right at this point, even at 90% throttle
stick deflection, the helicopter could only maintain a 6-8 inch high
hover above ground. At the 5 minutes 30 seconds mark, the heli was
unable to get off of the ground anymore. Interesting I thought,
there were no indications throughout the 4 minute 52 second hovering
power duration of any lack of power problems as in the previous
tests with the ESky 7-cell packs. With some curiosity, I did not
change a SINGLE parameter within the entire helicopter's setup
except for the removal of the cabin or canopy so I could repeat the
last test to see what the difference would be. I tried as best as
I could to maintain the same height above ground as in the last test
flight(neck high) or the same flight profile. I took off and held
the heli over the same spot on the ground in the last test flight,
I was able to maintain hovering power for a full 5 minutes and 55
seconds, then right at this point, the heli drifted to the ground
and made a fairly soft landing even with FULL throttle stick de-
flection. Without changing a single item in the helicopter's setup
execpt the cabin and flying the same flight profile, I could increase
flight time by up to 1 minute and 3 seconds. Again, as in the last
test flight, there was not a single instant of a sudden lack of hov-
ering power, just one stretch of hovering power and then the pack
dying soon afterwards. I proved that this new 8-cell pack was at
higher quality and did solve the lack of hovering power duration pro-
blem, but flight times were 2 minutes and 5 seconds less than with
the BRUSHED setup, but WITHOUT a cabin or canopy. If using a cabin
or canopy, the flight time was right around 3 minutes less in dur-
ration. Since that test flight, I have abondoned using the ESky 7-
cell stock packs and have switched to the Electrify 8-cell 650 MAh
pack, while I also have not been flying with the cabin or canopy so
as to get some more flight time. What does all this mean? I am
sure I must be the only moron who is currently flying a DIRECT DRIVE
setup with a brushless tail motor with NiMH flight packs of capacity
not exceeding 700 MAh. But, I am a sucker for punishment and really
wanted to see for myself the flight duration characteristics of a
DIRECT DRIVE setup and a brushless tail motor WITHOUT using a LiPO
flight battery pack. There is no question in my mind, at least from
what I have experienced with the direct drive setup, that a geared
tail rotor setup is more EFFIECIENT than a direct drive one and DD is
NOT advisable unless using LiPO battery technology due to its good
energy density. In both test flights and every test flight made
since then, after the Electrify 8-cell flight pack dies, the Feigao
brushless tail motor is HOT to the touch and will burn your finger
if left on there for a long enough time, where the 8-cell pack itself
is almost hot or very warm, but soon cools down. I have come to the
conclusion now with my current brushless setup, either I invest in LiPO
battery technology or go to a GEARED setup with the Feigao tail motor.
I have pretty much concluded that I am going to try a GEARED setup
first, since, in theory, all I need to do is to place on an 8 toothed
pinion big enough to fit onto the shaft of the Feigao tail motor and
then use the stock ESky tail rotor/tail rotor drive gear and tail
drive shaft. As always, I will test this and post my test results.
As an after thought, I did do one ground run test that was pretty
interesting. I did not change ANYTHING in the helicopter's setup
and was running the test with the Electrify 8-cell battery, but
WITHOUT the Feigao brushless tail motor hooked-up. Granted, the heli
was held on the ground and used ~65% throttle stick deflection in the
test with some cyclic control inputs to further put a load on the
fight pack, but I was able to run the helicopter up to 8 minutes and
50 seconds, where right at this point, there was a noticeable drop in
head speed. This was a full 3 minute increase in run time over the
Feigao brushless tail motor and GWS 4530 tail rotor DD(Direct Drive)
setup. |
I am flying a
(( This weekend I purchased a 9
