Contents
Preparations
The first stage (avx1406/2Y, 8cells 15T)
The second stage (avx1406/2Y, 8cells 18T)
The third stage (avx1406/2Y, 8cells 20T)
The fourth stage (avx1406/2Y, 8cells 21-23T and 10cells 20T)
The final stage (avx1406/Rc7, 8cells 20T)
Summary （ここだけ日本語）<<==== Read firstly.
Appendix <<==== Important !!
A heatsink (originally selled for 540 class RC-car) is attached for the cooling of the aveox1406/2Y.
Non-contact thermo-meter (supplied for GP and EP RC-model. This is a Yokomo's article.).
Th upper instrument is the non-contact thermo-meter.
Before the test, I politely
re-adjusted the motor timing in Aveox1406/2Y.
It was done by the slight revolution of the motor end cap.
For the purpose, revolving the end cap,
the Io and KV values were measured and adjusted.
7cellsRC2000mAh + 16T pinion gear + styrofoam main rotor EH-15
--------------
8cellsRC1700mAh(Sanyo) + 15T pinion gear(Asami) + styrofoam main rotor EH-15(Kyosho)
The load rate 87% suggests that the loading is slightly severe (hard)
for Neodyum motor. If the rate is less than 80%,
the output is too large. So, the motor should get rapidly hot.
Inversely, if it is 90-95% at the max main rotor pitch,
the usage of the motor is good and kind.
In every flight, the surface temp was measured.
The final temp always reached over 60degC, as shown below.
I temporally stopped the flight for the cooling down of the motor,
occassionally.
40degC === The motor is normally hot, but we can continue to touch it.
45degC === Hot shower's temp. in bathroom.
50degC === It is very hot. We can touch the motor only for 10 seconds.
60degC === The motor is hard hot. We can touch it only for a few seconds.
over70degC === We cannot touch it, at all. The motor really burns !
flight times,/ date /initial motor temp., /final motor temp./ comments
1st 2000/8/3 30degC ==>> 65degC only hovering (3 stops for cooling)
2 2000/8/3 28degC ==>> 66degC only hovering (2 stops for cooling)
3 2000/8/4 28degC ==>> 67degC only hovering (1 stop, from here with Jet Ranger body)
4 8/4 26degC ==>> 62degC only hovering (1 stop)
5 8/5 28degC ==>> 62degC moderate flight (1 stop)
6 8/5 34degC ==>> 69degC moderate flight (non-stop)
7 8/5 35degC ==>> 63degC moderate flight (1 stop)
8 8/6 27degC ==>> 64degC only hovering (1 stop)
9 8/6 33degC ==>> 69degC only hovering (1 stop)
10 8/7 28degC ==>> 63degC moderate flight (non-stop)
11 8/7 35degC ==>> 66degC moderate flight (2 stops)
12 8/7 39degC ==>> 69degC moderate flight (2 stops)
13 8/7 27degC ==>> 68degC only hovering (1 stop)
14 8/7 27degC ==>> 68degC only hovering (1 stop)
15 8/8 28degC ==>> 68degC moderate flight (1 stop)
16 8/8 37degC ==>> 66degC moderate flight (1 stop)
17 8/8 40degC ==>> 72degC moderate flight (non-stop)
18 8/9 27degC ==>> 65degC moderate flight (non-stop)
19 8/9 39degC ==>> 70degC moderate flight (1 stop)
20 8/9 39degC ==>> 65degC moderate flight (1 stop)
21 8/10 29degC ==>> 66degC only hovering (1 stop)
22 8/10 40degC ==>> 68degC only hovering (1 stop)
23 8/11 28degC ==>> 65degC moderate flight (non-stop, 5.5min)
24 8/11 39degC ==>> 66degC moderate flight (non-stop, 5.5min, RC1.7Ah)
25 8/11 41degC ==>> 69degC moderate flight (non-stop, 6.0min, RC2Ah)
The power feeling is still the same as the start of the test.
These temp. is measured at motor can's surface.
This measurement largely depends on the measured part of the motor and
ambient temp.
In order to increase the output, The pinion gear was changed
from 15T to 18T, and the main rotor was changed from light styrofoam (EH-15)
to heavy wood (Kyosho high grade EH-83).
Don't compare this rpm data with the data of the other pages,
since the main rotor and its pitch condition are not the same.
The load rate may be only able to be compared.
---------
rpm A V W load rate condition
1760 12.9 9.51 0 deg pitch
1690 16.1 9.32 hover
1515 25.3 8.82 86% +8.5deg pitch (<<== I reduced from 1st stage)
---- Short comment for magnet's power of Aveox1406/xY ------
The load rate became slightly low.
For the other Neodyum motors (such as Hacker, Kontronik
and so on), the value is 88-93% at similar output power (180-230W).
For most of Ferrite magnet motors (stock brushed motors),
the value is 70-75%. Note that Ferrite magnet's power is weaker
than Neodyum for the same size magnet. Hence,
I guess that Aveox1406/xY may have smaller Neodyum magnets
than the others (class 480-550 motor).
Otherwise, the Neodyum magnet may originally
have 'weaker' magnetic power. Anybody can
comment about this low load rate ?
Here, the final temp 70-85 degC is examined.
For the purpose, I wanted 19T pinion gear, but
I have not the gear (, at moment). Instead, sometimes,
the second flight on the day is started at higher temp
(by insufficient cooling after the first flight).
In the bench test for the 3rd stage of the test.
The motor axis slipped inside of the magnet rotor.
Finally, these parts which were attached by glue
have been separated, as shown in the photo.
I opened the motor end cap, and then
measured the magnet's power in the technique
shown in the Appendix (below). The four magnet plates
has 1.2kg, 1.4kg, 1.3kg and 1.4kg as the drag power,
respectively. So, some of the magnets have slightly
lost the magnetic power.
---- Aveox's axis shaft ---
This axis shaft is made of soft iron. You can see the 'dirty' shaft surface
of the attachment place of the pinion gear (scratched by a screw of pinion gear). Since German motor (out of Ikarus) has a hard iron shaft, it is almost
no-scratch.
------- The damage and KV change :
Theoretically (Physically), when the magnet lose the power,
the motor constant KV must increase. It is explained
in the page of 1.3 Lecture note. Exactly speaking,
the reduction of the magnetic power is propotional to the
increase of KV.
In this damaged rotor, the total magnet power was
1.2+1.4+1.3+1.4=5.3kg as the drag power. In a no-damage (the other)
rotor, it is roughly 1.4*4=5.6kg. Roughly speaking,
the reduction of magnet power is (1.0-5.3/5.6)=5%,
so that KV(=3180) must be over 3300.
In addition, the no-load current Io must also increase.
It seems that the increase to 3300 from 3180 slightly exceeds
the fluctuation level of the KV value, which is sometimes 3-5%
detected in my the other motor tests.
However, anyway, I cannot say that the motor constants changed
in this test.
I don't know why there is almost no change of KV and Io, at moment.
It may be in the range of fluctuation level of KV.
In such case, I cannot detect the slight increase.
Anyway,
if the constants do not change, the motor performance also does not change.
(The coil resistance Rm does not change in this case, of course. )
Imagine when the magnet power is completely lost,
the motor performance is zero (it is not a motor !!!).
So, the motor contant must change, as the damage proceeds.
---- When did the damage happen ?
As a result, I couldn't know when it happened in this test.
Note that I did not measure the drag power in the first stage.
The damage might had already proceeded in the first stage of the test
(less than 70degC for the motor surface temp).
Anyway, at least, through this about 40 flights (= 1st stage + 2nd stage),
I didn't feel the power down in the real flight.
Also, the flight duration time was not changed.
Therefore, probably, if we keep less than 60-70degC,
the motor life time (in the power feeling)
may 'easily' exceed 100-200 flights. Can you be satisfied ?
On the other hand, if the motor surface temp exceeds 80degC,
the motor may be damaged.
Before I throw the motor,
I tried again to attach the magnet rotor to the axis shaft by epoxy glue.
The repair seems to be successful.
In fact, there is no problem in a few real motor runs.
Already, the magnet has been slightly damaged and lost the power,
but I decided to continue this test.
As a result, the KV value slightly increased
from the previous value (3170-3180).
But, the Io value was not changed.
So, the increase of KV does not directly
mean the damage of the magnet. This (small) change
may be the fluctuation of the KV value, which I am often saying.
In order to increase the power, I use 20T gear (module0.8, Kyosho),
here. This gear is slightly mismatched to EP SR's idle gear,
but anyway, available (So, the gear meshing is loudy).
Conditions ; (MY 2nd) EP Concept SR with Jet Ranger fuselage,
8cellsRC1700-2000mAh, 20T pinion gear,
EH-83 (Kyosho high grade wood main rotor).
This data is very powerful. The looping and roll
should be sufficiently possible. Also, 3D flight is possible.
But, the motor got extremely hot, as shown below.
The heat loss level steadily increases from the 1st and 2nd stage.
This power feeling (= rpm data) is similar
to the data of Aveox1406/1.5Y(Rc7),
12T and 8cells. In that case, 13T resulted in
the serious damage of the motor magnet, as shown in Appendix (below).
Hence, if I change 21T or 22T from 20T,
this Aveox1406/2Y may enter the damgerous
power range for burnning up.
Because of powerful flight, after every flight,
the motor gets much hotter than the previous tests in this page.
Here, I always maintain the start temp
to be sufficiently low, unlike the 2nd stage.
Anyway, it has been revealed that the input over 250W may
cause the destruction of
the linkages of EP SR, even when those were already
reinforced with metal link balls and so on.
If you still use normal linkage, it is out of
the problem !!! It was caused in my 2nd EP SR, but
ECO8 also has weak plastic linkage parts. Be careful !! (2000/8/30)
-----
In 45 and 46th flights, I tried looping with Jet Ranger fuselage.
The loop's shape was dirty, but it was successful.
In each end of every flight, I felt the power down of the NiCd
battery. Since these battey are used over 150 flight times,
these are sufficiently old. Such old batteies
cannot keep the high power (voltage) in active flights (2000/9/2).
-----
In the 55th flight, the magnet rotor was detached from the shaft, again.
It was in flight. I tried to escape by the autorotation, but
it resulted in a hard landing. Fortunately,
the damage was light, but anyway
the motor was broken up, again.
I opened the motor can, again. The magnet still seems to be no damage
since the beginning of the third step of the test.
So, I decided to continue the test after the repair of the motor.
Subsequently, the flight condition in the third step is continued.
In the check flight, it crashed, again.
The pitch linkage was detached in the hovering.
The linkage might have been little
damaged in the previous hard landing.
I got tired. Stupid, again !!!
A wood main rotor, a spindle shaft, a tail boom and so on were replaced.
After the flight, I measured the motor contants, again.
The Io value seems to become higher than the previous data.
The KV is not changed.
In the third stage,
I felt the autocut problem to be dangerous to keep this test.
I cannot safely continue the flight tests.
So, using tighter gear ratio, I decide to terminate this test.
Firstly, I installed 21 and 23T pinion gear, which is
my special made gear with 3.17mm hole. In this stage,
I will 'gradually' increase the load in various ways, until the magnet
is damaged.
In addition, hall sensor unit was detached from the end cap.
It should be caused by either heli's vibrations or heat-loss.
The auto-cut problem may be related to the detachment.
In the next step, I tried to increase the power.
For the purpose, I replaced the 21T gear by 23T gear.
At the hovering, 26A draws. At the max pitch,
over 30A !!! The input reaches around 235W at hovering !!!
In order to terminate the motor,
10cells for 20T gear is eventually used. However.........
The final temp in the 2min flight was 70degC.
The motor easily got hot.
Probably, if the motor run until the end of battery discharge (approx.
4min), the surface temp should reach the dangerous region
(over 80-90degC).
I thought that it is very hard to burn the magnet in avx1406/2y.
Certainly, the magnet have been slightly damaged, already.
It was caused by a continuous run with 2 batteries in the 2nd stage.
So, at least, if we take sufficient cooling time (15-20min),
Aveox1406/2y does not burn up. Probably,
more cell (higher voltage) may result in the overheat (magnet damage),
but the Aveox L160C (ESC) could not be used for such higher voltage and
higher power, due to overheating of the ESC.
In this stage, the magnet rotor was removed from avx1406/2y,
and instead, installed in avx1406/1.5y(Rc7).
The flight condition in which the magnet burned up in fast summer
is examined, again.
----- Condition:
Aveox 1406/1.5y(Rc7), 8cells1700mAhRC, 13T pinion gear and
JRC wood symmetry rotor,
When I opened the motor can,
a magnet plate was ejected from the slot of the iron rotor.
The ejected magnet plate contacted with the coil case,
so that the magnet rotor could not revolve in the motor.
The damage style was similar to the previous one.
The magnetic power for the ejected magnet was 0.8kg,
by the method shown below (Appendix).
The orher magnets are more than 1.3kg.
Hence, the ejected magnet's power have been evidently lost.
The life time of brushless motors seems to be almost forever,
if you use correctly. The following characteristics was obtained
in this page
which is for the Neodyum magnet brushless motors.
--- The upper limit for the input power of Aveox1406/2y:
The upper safety limit was not revealed.
At least, even in summer (25-30degC),
the 2min continuous run at 270W with 10cells and
4min continuous run at 250W with 8cells was safe for the magnet.
Continuous 300W run for 3-4min may result in the magnet damage.
--- The upper limit for the input power of Aveox1406/Rc7:
I have burned up two magnet rotors in this motor. As a result,
the 3min continuous run around 250-270W (30-35A) with 8cells
resulted in the serious magnet damage. In this motor,
the max efficiency rate is established over 50A for 8cells(9V).
So, note that the condition is very
far from the max eff. rate point.
--- The temperature limit for the magnet (Neodyum) damage.
Certainly, there is a critical temperature, beyond which
the magnet is rapidly damaged. Inversely, if we keep
the motor temp at less than the critical temp,
the magnet is almost not damaged. In the case,
the lifetime of the magnet almost seems to be forever.
However, in this test, the temp was not clearly revealed.
Note that I measured the motor surface temp, which
should be much lower than the magnet temp inside of the motor.
'Roughly speaking', in the case of Aveox1406/xY,
the critical temp which is measured
at the motor surface hidden in the heli's fuselage
was around 80-90degC in ambient 20-30degC air.
But, there is a safe case (no magnet damage)
for more than 100degC. Hence, the critical temp should
largely depend on the flight style and ambient various conditions.
If you subsequently fly after the first flight,
sufficient cooling time is required.
The interval time 15-20min is required
for the cooling from 70degC to 35degC.
Insufficient cooling easily causes
the magnet damage due to overheating in the second flight.
--- The other problems for high power flight :
As shown above, out of the magnet damage,
I have experienced various troubles.
The powerful flight may rapidly damage also the heli's mechanics.
For instance, the teared main rotor is very dangerous.
Check the linkage. The reinforce is also required.
In addition,
frequently, electric speed controler (ESC) may be easily damaged
due to the overload. Read the instruction manual of your ESC
and then check the drawing e-current.
出力限界内で使っている分には、ブラシレスモーターの寿命は半永久というか
墜落で壊れるまで、と思えます。ブラシが無いことの効果は絶大です。
ちなみに、ヘリの場合、モーターはフレーム内部に抱え込まれているため、
墜落でも壊れにくいです。しかし、
飛行機だと大抵は頭から墜落するので、モーター壊れやすいです。
------ Aveox1406/2Yの入力限界について
今回のテストにおいて限界ははっきりしませんでしたが、少なくとも
気温25-30degCにおいて、10cellsで入力270Wを2分持続しても大丈夫
でした。また、8cellsで 250Wを 4分持続しても焼きつぶれませんでした。
ただし、下記の通り、測定された温度限界からの推定では、
300Wを3-4分持続だとアウト？という感じです。
------ Aveox1406/Rc7の入力限界について
ずばり、8cellsで入力250-270Wを3-4分という辺りが限界です。
ただし、この条件はこのモーターの最大効率点を大きく外れています。
本来は、8-10cellsなら、もう少し高出力でもう少し短時間運転が、
このモーターの正しい使い方です。つまり、モーターグライダー
向けということ。または、アビオが推奨する通り、6cellsRCカー用なので、
6-7cellsなら連続運転でかなり無茶できそうです。
----- ネオジウム磁石の温度限界
メーカーに言わせると、150-180degCで磁力が消失するそうです。
これはどのネオジウムを用いたすべてのモーターに共通です。
我々がその磁石温度そのものを測定するのは難しそう。
そこで、モーター表面温度を調べてみました。
気温20-30degCだと、85degC以上で磁石はダメージを受けました。
でも、107degCまで焼いてもダメージ無しというケースも経験しました。
おそらく、急激に焼いた場合はモーター内外の温度差が大きくなり、
その場合は表面温度が低くても磁石は危険温度に達してしまうのだと
思います。これはダクトファン機みたいに
モーター表面だけ冷却される場合も同じ。外気温が低い場合も
あんまり調子に乗っていたら「やばい」かも。
ですから、余裕を見て、モーター表面温度が70degCを越えたら
要注意と思った方がいいかも知れません。冬はモーター表面60degC以下
でも危険かも？？
なお、磁石はその（曖昧な）危険温度以下で使われている内は
ほとんどダメージを受けない様に見えます。「果てしなく使える感じ」。
その前にベアリング交換など他のトラブルが発生しそうです。
逆に、ある温度を越えると、磁石は急激にダメージします。
例えば、F5Dレース（世界戦）ではモーターをかなり酷使
（300-500Wで1.5分）しますが、その同じモーターで何度も飛ばすそうです。
ただし、フライトの合間に60分程度の冷却時間を取るそうです。
理論的には、加熱ダメージで磁石が減磁したモーターは
KV値と無負荷電流Ioが増えるはずですが、実際には、
これら数値が増え始めると、一気にそのダメージが進行する様です。
従って、これら数値をバロメーターとするのは難しいのかも知れません。
--------磁石ダメージ以外のトラブル
この様なハイパワーフライトでは磁石のオーバーヒート以外にも
モーターや機体に様々なトラブルが発生します。
コントローラーのオーバーロードもよくあるケースです。
その場合、コントローラーから煙が出たらおしまい。
それと、機体側に関しても、ピッチリンケージ等は
強化しておきましょう。ハイパワーフライトでは
色々なトラブルが生じます。上記の本文（英文）を参考にして下さい。
---
In last summer, I have completely burned out
1406/1.5Y with 8cells2000mAh and 13T pinion gear.
At the time, the max input at the max pitch exceeded 250W (over 30A).
The continuous run for 60sec resulted in the complete overheating.
I did not measure the temp., but I couldn't touch it, at all.
The magnet rotor was distorted due to the heat expansion,
and eventually broken. Fortunately,
we can repair with a spare rotor (50USD cheap !!).
You can see (three of) four magnet plates embedded in the iron rotor.
A distorted magnet is slightly ejected (floated up) from the rotor slot.
In order to examine the reduction of the magnet power,
a coil spring balance is used. By pulling down the magnet rotor
by a hand, the magnet force can be measured.
In new rotor (no-damage), each of four magnets has
the max drag power 1.3-1.5 kg, which
slightly varies on each magnet.
In the damaged rotor shown above,
the max drag power for the magnet plate
, which was distoted and ejected from the iron rotor slot,
was only 0.2kg, and all the other three magnets were 1.2-1.4kg.
The significant reduction of the drag power
indicates the reduction of the magnet power by overheating.
It is remarkable that a magnet plate is only damaged and
the others (three magnets) are almost still alive.
It suggests that the damage of the magnet
catastrophicaly proceeded in the overheating.
In other words, only when the temp of the motor (magnet)
exceeds a critical temp., the damage of the magnet
rapidly proceed. In addition,
in the damaging process, the magnetic load abruptly concentrates
into a magnet from the other magnet.
The concentration accelerates the damage of the one magnet.
As a result, a magnet is only damaged, seriously. (
So, off course, magnet itself generates heat, due to the loading. )
This result suggests that there should be 'a critical temperature'
beyond which the damage of magnet rapidly proceeds in overheating.
I don't know how much it is, but at least, it is more than 70-80degC
(for the motor surface temp.).
1:--- This result is applicable only for Aveox1406.
This may be also applicable for the other Neodyum magnet motors.
However, it is not applicable for Ferrite and Cobalt motors.
These motors' magnet is weaker than Neodyum.
Note that Ikarus X250- is also not Neodyum motors.
2:--- These temp. data was obtained in Japanese summer (25-35degC).
In addition, note that
we cannot directly measure the temp. of the inside of motor,
which is important for the damage of the magnet.
The inside temp. is much higher than the surface temp.
Especially, in winter, the discrepancy between the surface temp and
inside temp becomes very large. Hence, even if the surface temp.
is sufficiently low,
the inside temp may reach dangerous temp. Be careful !
Adjustment of the motor timing :
KV Io(A) at V
3156 3.10 7.97
3220 3.03 7.92
These were taken on 2000/8/2
The motor timing must be determined for the real-load which you require.
I think that these values are almost appropriate for EP SR.
As the motor magnet is damaged, the KV value increases.
Initial benchtest on Kyosho
EP Concept SR :
2000/8/3
rpm A V W
1420 8.0 8.44 68 0 deg pitch
1320 13.4 8.16 109 hover pitch
1230 19.1 7.88 148 +11deg pitch
With this gear ratio, the motor 'moderately' gets hot in summer.
The flight is very powerless.
2000/8/3
rpm A V W load rate condition
1530 9.2 9.68 89 0 deg pitch
1430 14.5 9.39 136 hover pitch
1325 21.0 9.03 190 87% +11deg pitch
Load rate = (real motor rpm)/(no-load rpm)*100 (%)
The motor gets very hot in summer (30degC).
Note that the max efficiency point of this motor is too far
from this flight condition. So, the heatloss is naturally high.
EP SR normally lifts off, but the max input power 190W
is still not so high. 3D-acro is impossible.
I dislike this powerless condition.
2: Long term test (the first stage):
The flight records :
Styrofoam main rotor(EH-15) + 15T pinion gear
(approx. 1.6kg for Jet Ranger version).
The each flight time is 5-6min with NiCd8cellsRC1700-2000mAh.
The data was taken in Japanese summer (morning or evening 27-30degC).
The initial temperature is almost close to the atmosphere temp. However,
the initial temp in the 2nd and 3rd flights on the day
is often higher than that of the first flight.
15min is taken for the natural cooling from 60-70degC to 40degC
(without any cooling fan).
Re-measurement of the motor constants, Io and KV :
flight times KV Io at V date
25st 3192 3.01 7.86 2000/8/15
The KV and Io values are not changed.
So, the magnet is still fine.
Hence, it was revealed that this motor almost has no damage
in flights, upto 70degC, under 200W, with less than 8cells.
3: Long term test (the second stage) :
Bench test :
Wood main rotor EH-83, 18T(module0.8) and NiCd8cellsRC1700-2000mAh
with Jet Ranger body.
This is relatively powerful. Loop and roll will be possible.
But, it easily got very hot, as shown in the next table.
The flight records :
The flight condition is mentioned above.
Jet Ranger fuselage is still used.
In this table, most of flights is 'non-stop' flight.
flight times,/ date /initial motor temp., /final motor temp./ comments
26th 2000/8/18 28degC ==>> 68degC only hovering (5min with 8cells 2Ah)
27th 2000/8/18 60degC ==>> 78degC only hovering (1 stop, 4.5min with 8cell 1.7Ah)
28 8/18 28degC ==>> 67degC only hovering (4.5min, 2Ah )
29 8/18 62degC ==>> 88degC only hovering (4.5min, 1.7Ah)
30 8/19 28degC ==>> 67degC moderate flight including a looping
31 8/19 61degC ==>> 78degC moderate flight
32 8/20 27degC ==>> 66degC only hovering
33 8/20 62degC ==>> 85degC only hovering (5min, 2Ah)
34 8/20 28degC ==>> 71degC only hovering
35 8/20 63degC ==>> 84degC only hovering
36 8/21 26degC ==>> 71degC only hovering
37 8/21 63degC ==>> 82degC only hovering (4.5min, 1.7Ah)
The power feeling is still almost the same as the beginning of this test.
In the 30th flight, I tried a looping (only once).
It was successful, but
the recovery altitude was only 3 meters (from the start alt. 25m)
(due to the heavy weight 1.6kg) !! If the fuselage is not attached,
it should fly well.
Remeasurement of the motor constants Io and KV :
KV Io (A) at V
3170-3180 2.98-3.05 7.8-7.9 (2000/8/24)
These values are still the same as the previous values.
So, I tought that the motor was still no damage, but
it was incorrect. As shown below,
the motor magnet was slightly damaged, certainly.
How was the motor broken ? (2000/8/26) :
Discussions :
Oh ! The magnet rotor survived !!!! (2000/8/26) :
The motor constants; KV and Io (2000/8/26) :
KV Io at V
3270-3280 2.95-3.05A 7.7-7.8
Since I have opened the motor end cap, the motor timing
has slightly changed (I adjusted well, but I could not
set the previous data, again).
4: Long term test (the third stage) :
Bench test :
rpm I(A) V W condition load rate
1960 19.1 9.73 186W 0deg pitch
1850 22.2 9.37 208W hovering
1620 30.8 8.75 270W +8.5deg pitch(the same as the 2nd stage)
1860 17.8 9.20 164W
1760 21.9 9.00 197W
1575 30.4 8.50 258W
These data cannot be exactly compared with the other pages.
Because, some conditions are slightly different.
The flight records :
The flight condition is mentioned above.
Jet Ranger fuselage is still used.
In this table, most of flights is 'non-stop' flight.
flight times,/ date /initial motor temp., /final motor temp./ comments
38th 2000/8/27 28degC ==>> 68degC only hovering (4 stops for cooling)
39th 2000/8/27 31degC ==>> 76degC only hovering
40 8/28 30degC ==>> 72degC only hovering (4min10sec, RC1.7Ah)
41 8/28 26degC ==>> 70degC only hovering
42 8/29 28degC ==>> 74degC only hovering (4min, RC1.7Ah)
43 8/30 28degC ==>> 75degC only hovering (1 stop, crash !)
44 8/31 30degC ==>> 73degC only hovering (4min10sec, SCRC1.7Ah => 82degC, hot !!)
45 9/2 30degC ==>> ?? 3 loopings and moderate flight
46 9/2 30degC ==>> 66degC 3 loopings (slightly cooler than hovering)
47 9/3 25degC ==>> 65degC only hovering (just after rain, so the air was cool)
48 9/5 24degC ==>> 69degC only hovering (4min10sec,1.7AhSCRC)
49 9/5 22degC ==>> 74degC only hovering (After a rainy day, Autumn started. Cool air.)
50 9/5 20degC ==>> 68degC only hovering
51 9/6 21degC ==>> 64degC only hovering
52 9/7 25degC ==>> 70degC only hovering
53 9/7 40degC ==>> 80degC only hovering (The cooling (16min) after last flight was insufficient.)
54 9/8 25degC ==>> 70degC moderate flight (after this flight, cooling for 16min )
55 9/8 40degC ==>> --- moderate flight (crashed, due to detachment of the shaft, again !!)
In 43th flights, the heli lightly crasched.
The tail linkage was broken (detached)
by the extremely strong vibration of the
high power drive unit. Fortunately, the damage was very small.
But, if you would be unlucky, it might lead to the explorsion of heli.
Probably, you may not be able to imagine the serious situation.
Ocassionally, teared main rotor may be horizontally thrown to
the flyer, yourself !!! So, it is extremely dangerous. 
The short rod end (EH-45) was broken up
by the extreme powerful vibrations.
Don't use it. It was replaced by a long type (EH-20).
looping Jet Ranger (1.6kg) !!! Broken up, again. It is stupid.
Re-measurement of the motor constants (2000/9/8):
KV Io at V
3280-3290 2.95-3.12A 7.80-7.95
The data almost does not change from previous data.
Hence, the damage of the magnet is not detected.
Flight records :
Teared rotor was horizontally scattered
(toward flyers, may be). So, the 'exact' eye-level hovering is dangerous.
I got tired for the repeated construction. So, the tail cover of Jet Ranger is not atteched.
56th 9/9 25degC ==>> ??? (only hovering)
57 9/10 26degC ==>> 75degC (only hovering)
58 9/11 23degC ==>> 67degC (moderate flight)
59 9/11 40degC ==>> 71degC (moderate flight, before this flight, 16min cooling)
60 9/11 40degC ==>> 76degC (only hovering, before this flight, 16min cooling)
61 9/11 21degC ==>> 65degC (only hovering)
62 9/11 40degC ==>> 71degC (only hovering)
63 9/11 40degC ==>> 80degC (only hovering, 2 stops due to auto-cut by ESC ??)
KV=3280-3290 Io=3.15-3.30A at 7.75-7.90V (The Io value slightly increases !!!)
64 9/12 23degC ==>> 65degC (moderate flight)
65 9/12 40degC ==>> 75degC (only hoveing)
66 9/12 35degC ==>> 71degC (only hovering, 1 stop due to auto-cut ???)
In the 63th and 66th flights, the auto-cut function of ESC (AveoxL160C)
worked in the air. The power was instantly turned off.
But, after the stop, the motor begun to run normally, again.
I didn't know the reason. The ESC was also not so hot. 
The left is the rotor and can
of PLettenberg HP220/20/A3P6. The right rotor is avx1406/2y's one.
These motors have similar weight (180-190g). However,
evidently, Aveox's magnet is smaller. This is the reason why
the load rate of avx1406/2y is lower than that of German
powerful motors.
The fourth stage :
67th 9/14 24degC ==>> 69degC (21T gear, only hovering, 1 stop, 3min50sec)
68 9/15 24degC ==>> 70degC (looping and roll)
69 9/15 30degC ==>> --- (after a looping, crash, due to auto-cut by ESC)
In 68th, a roll was tried, in addition to looping.
I felt the power to be still insufficient for the roll,
because of the heavy Jet Ranger body.
Subsequently, after 30min cooling, the 69th flight was executed,
and then resulted in a crash,
due to the auto-cut function in ESC. I tried to
escape by the autorotation,
but the skid was broken by the hard landing.
70th 9/15 24degC ==>> 72degC (only hovering, about 3.5min)
71 9/15 30degC ==>> ?? (only hovering, about 3.5min)
Amazingly, the motor was still safe for such extreme high power.
This power condition is almost the same as the condition
of avx1406/1.5y(Rc7) which was previously burned up.
Nevertheless, the final temp 72degC is evidently safe.
So, avx1406/2y may have higher efficiency rate for 8cells use,
than avx1406/Rc7.
72th 9/16 25degC ==>> 70degC (Stooped in 2min. Auto-cut in ESC worked.)
The drawing current was 25A at the hovering.
The input was 275W at the time.
It is larger than that of 70-71th flights (235W).
At the max pitch, it reaches 30A !!!
In 2min continuous run, the ESC abruptly stopped,
due to the heat-protection of the ESC.
In fact, the ESC was very hot.
So, I should have stopped the test.
The final stage :
----- Motor constants.
Io=5.12-5.20A, KV=4270-4330 at 6.7V
The Io value is very high.
It means that heat loss is also high.
This motor (less coil turn motor = less Rm value) must be used
in lower voltage (less cell number).
The continuous run with 8cells is slightly hard.
Bench test data;
1680-1730rpm 25-27A (230-240W) at hovering.
1550rpm 35A at max pitch
73th 9/16 27degC ==>> 80degC (only hovering, 1 stop for cooling)
After this run, Io and KV did not change.
This motor avx1406/1.5y(Rc7) easily gets hotter than avx1406/2y.
74th 9/16 28degC ==>> 107degC (only hovering, non-stop)
The final temp was very high.
But, the motor looks like no damage. In fact,
after this run, Io=5.2-5.3A and KV=3275 were obtained.
Hence, there is no significant change.
75th 9/16 28degC ==>> 91degC (only hovering ==>> abrupt stop in 3min ==>>
eventually, broken up !!)
In this flight, I strictly
repeated the situation in which magnet burned up in last summer.
It was done on a test bench (on the ground).
Firstly, full throttle run (35A) was maintained for about 90sec,
and subsequently, hovering (28A) was continued.
In the total 3min run, the motor was abruptly stopped.
Immediately, the surface temp of the motor was measured.
The temp was 91degC, which was lower than 107degC of 74th flight. 
The magnet's heads are
scratched by motor coil (outer case). 
Two damaged rotors.
One of these is reported below (in Appendix).
In both rotors, only a magnet was ejected from the slot.
Also, the magnet power has been lost.
Summary :
まとめ :
Appendix :
How was the magnet damaged ? :
Be careful !! :