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In order to calculate your RC helicopter head speed, there
are 4 things you need to know:
-
The number of Teeth (T) of your motor pinion. If
you set up your RC helicopter yourself, you should know
that by heart. If you bought the RC Helicopter RTF
(ready to fly) or someone set it up for you, just count
the teeth of your motor pinion. It is a lot easier than
counting the teeth of your main gear.
-
The number of T of the main gear. This is easy to
find – just count the teeth on your main gear. Well, not
that easy – just try it, you’ll know what I mean. I get
a different number every time I count it. Again, you may
find the number of your main gear T on the owner manual.
-
Motor kv -
the rpm (head Speed) produced by a motor
per volt applied.
You
should be able to get the motor kv from the motor
specification sheet.
-
Voltage: This is the voltage of your battery. You
may get this information from your battery specification
sheet or label.
-
Efficiency rate: This is the percentage of your
RC helicopter motor efficiency when you are flying with
your set up. It is the norm to use 80% (.8) or 90% (.9)
depending many factors though you run 100% on your
throttle curve.
As it was said earlier, the result would only give you a
rough estimate of the head speed. A better way is to use a
tachometer to measure your RC Helicopter head speed.
Estimate Head Speed = (Motor kv * Battery Voltage /(Main
Gear /Teeth of Pinion)) * Efficiency Rate
For example, I set up my MX400 with JGF
400HD (KV:
4000-4400)
with a 9 T pinion.
I am going to use 3 cells Li Po battery that produces 11.1
voltage. T of MX400 Helicopter main gear is 138.
Now I want to know what is my MX400 helicopter head speed
is.
**Remember
from your math class, start from the most inner bracket
out when calculating the head speed
(4000*11.1/(138/9))*.8 =
2317.
My MX400 Head Speed would be around 2,317
If I use 8 T pinion on my MX400 for the same set up,
(4000*11.1(138/8))*.8 =
2059.
My MX400 Head Speed would be around 2,059
I broke down the formula here one step at a time for you
to understand it.
-
Main Gear/Teeth of Pinion = Gear to T Pinion Ratio, then
-
Motor kv * Battery Voltage = Maximum Head Speed (rpm),
then
-
Maximum Head Speed/ Gear to T Pinion Ratio = Head Speed
Without Efficiency Loss, then
-
Head speed Without Efficiency Loss * Efficiency (either
.9 or 8) = Targeted Head Speed
If you
know your target head speed and want to find out what the
T of your pinion,
click here
Don't want to read or
search any more? Just ask our Tech Support team at Helitown
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