Угол атаки серволопастей
Большинство своих вопросов по драгонфлаю 52 я разрешил.
Остался всего один.
Скажите, пожалуйста, должны ли серволопатки иметь нулевой угол атаки? Или, все-таки, необходима их установка под небольшим углом?
P.S.
ЭЛТ монитор, действительно помог померять обороты ротора в различных режимах. Т.е. 60 гц это 1800 оборотов, 75 гц - это 2250 оборотов, 85 гц не достижимо и не требуется.
P.S.
ЭЛТ монитор, действительно помог померять обороты ротора в различных режимах. Т.е. 60 гц это 1800 оборотов, 75 гц - это 2250 оборотов, 85 гц не достижимо и не требуется.
Кстати - я забил на покупку тахометра, ибо прекрасно приспособился мерять обороты своего Ти-рекса в домашних условиях связкой:
- “нательный” микрофон - 99р.
- какой-то халявный виндовый осциллограф “Oscilloscope for Windows95 version 2.51” by Konstantin Zeldovich (zeld@polly.phys.msu.su) - первое, за что зацепился взгляд в гугле.
- excel - для перевода ms в rpm
Алгоритм:
- Ставим рекса на пол
- Даём “гари”
- Аккуратненько подносим микрофон к лопастям
- Фиксируем сэмпл в осциллографе
- Смотрим на него “с прищуром” для определения периода
- Вносим цифирь в excel и смотрим результат.
😜
Нормальный тахометр всё равно хочется, но жаба пока сильнее душит, чем вышеописаный гемор. 😉
[quote=Ancher;366457]
Может вас это обескуражит , но вот :
RPM Tuning
Introduction
Tuning the engine rpm can be a problem. The preferred head speed for flight is 1550-1600 (hovering) to 1800 (3D). There are various rpm measuring devices available, but they are expensive and only the most expensive ones are capable of measuring the in-flight rpm. Furthermore, these expensive ones use a hole you have to look through and then you turn a button until your blades look as if standing still. This is of course not practical unless you have a friend available checking your rpm while you are flying, and furthermore he has to be very quick to measure temporary effects such as quick decents. Here I propose to measure the speed by just listening to the pitch of the engine.
The procedure
Fly the heli and remember the pitch of the engine at the point you want to measure. Then land the heli, find the frequency of the pitch you remembered by comparing it with the tuning fork (or whatever pitch meter you have) and adjust your throttle curve. Alternatively, you could remember or play the target pitch during flight. This pitch gives you the engine RPM (table below), which can be converted to rotor RPM with the appropriate table, depending on the gear ratio of your machine.
A cheap mouth organ or flute (toy shop!), or a tuning fork may come in handy for those who have no absolute hearing. Tuning forks usually give a standard 440Hz ‘a’, toy instruments may have a pitch indication but you’d better check its accuracy.
For the following tables I used ‘reine stemming’, assuming that you use a tuning fork.
pitch of engine
engine Hz
engine rpm
a
220
13200
bes
238
14280
b
248
14880
c
264
15840
cis
275
16500
d
297
17820
es
317
19020
Raptor 30
The pinion to main gear ratio is 9:86, so you can use the following table:
pitch of engine
rotor rpm
a
1380 (way too low!)
bes
1491 (just too low for hovering)
b
1554 (low end for hovering)
c
1658 (high end for hovering)
cis
1726 (low end for 3D)
d
1865 (3D)
es
1990 (too high!)
Raptor 46/50
For the Raptor 46/50, the main gear ratio is 10:85, and in that case you can use the following table. You can see that the engine should sound a full tone lower as compared to the Raptor 30.
pitch of engine
rotor rpm
g
1397 (way too low!)
as
1489 (just too low for hovering)
a (220Hz)
1552 (low end for hovering)
bes
1676 (high end for hovering)
b
1747 (low end for 3D)
c
1863 (3D)
cis
1941 (high end 3D)
Gear ratio
Just for information, for the raptor 30 the tail drive pulley (fixed to the main gear) to tail gear ratio is 41:9 (4.556:1). Setting the main gear at 1, we get a ratio of (86/9):1:(41/9) which would better be written as 86:9:41 for engine/main/tail, or approximately 10:1:5 if you like. Many web sites state a gear ratio of 1:9.56:4.56, corresponding to an order main/engine/tail.
For the raptor 46/50, the pinion gear has 10 instead of 9 teeth, and the main gear 85 instead of 86. This gives a ratio (85/10):1:(41/9) or approximately 17:2:9.
© W.Pasman, 10/2/2