The most forgotten feature about NiCad cells is
DISCHARGING. In order to avoid the Memory Effect and
increase the lifetime of the battery pack it is highly recom-
mended to discharge the battery completely after use.
Use a 30 Ohm/10-15 VA ceramic resistor, available from
your hobby or electronic shop for 6 h on the complete
pack or 5 Ohm/1
VA
for 24 h on the single cell and dis-
charge until both, the resistor and the battery are back to
normal temperature. It may not be practical to discharge
the packs after each use but you should do so at least
after 3 charging periods. Watch the electric model car rac-
ers for their charging and discharging equipment. They
usually have the best stuff.
Watch for the recommendation of the manufacturer. Avoid
overcharging as poisonous gas may escape from the cells. Do
not dump NiCad batteries, do not expose them to hot sunlight
or throw them into fire. Never open the cells. Handle damaged
cells with care and wear eyeprotectors and gloves. Damaged
and worn cells can be recycled and should be treated properly.
Finding the correct gear ratio is a rather delicate subject and
needs some experience and trials. Assuming that the motor
has its best efficiency at a certain, specific speed, it must be
your aim to operate the motor in this specific range. Here
efficiency means best energy economics at best power
output. In practice it is not very efficient to operate a motor at
50% speed with high energy consumption as it would per-
form better at 70% speed at even lower consumption.
Let us discuss the following example:
You have a motor with nominal 25,000 rpm . The efficient
speed would be abt. 17,500 rpm being abt. 70%, depending
on the motor's quality.
The target speed of the main rotor is abt. 1,300 rpm so we
have to find the proper gear ratio.
Various pinions are available from your IKARUS dealer. Let
us do some calculation:
17,500
------------ = 13.46
1,300
The 13 t pinion would offer the longer -, the 14 t pinion the
shorter transmission. Select the shorter one in order to com-
pensate possible deviations on the motor.
Another example. You have a very powerful motor that runs
12,000 rpm only, effective 9,500 rpm. To get the same main-
rotor speed, a pinion of 24 t will do.
There are other factors that may influence your decision: If
you go for hot aerobatics, 1,500 rpm mainrotor speed are
interesting. To obtain 1,500 rpm with the 17,500 rpm motor,
the 15 t pinion should be the best.
It is never easy to estimate the efficient speed of your motor.
Consider 70% of the nominal speed as a good value to start
with and select a pinion in the range. If you have doubts, go
for the smaller pinion.
The battery is the second sensible source of energy eco-
nomics. NiCad-batteries offer very good efficiency and per-
formance data - if treated well. The fun with NiCad cells is
that they allow high energy input while charging and very
high output if required. In car racing these cells often have
more than 100 A output.
To get a good performance you should have an eye on the
charging. NiCad cells tend to remind certain states of dis-
charging which may influence the capacity. The so called
"Memory Effect" may damage your cell if not treated cor-
rectly. Let us have some first remarks here:
-
Charge your batteries just before you intend to start.
-
Discharge your batteries correctly after use.
-
Use a suitable charger to improve the batteries lifetime
and performance.
In detail: 12-20 cell packs are available in any hobby shop. If
you have the choice use selected or matched types.
Remove the shrink folio for better ventilation. Use silicon or
Your experience ...
... that the motor does not run
freely.
... that the motor runs free but
the helicopter seems to be slow
in response.
... that the motor and the
battery are very hot after the
flight.
... that the motor and the
battery are rather cool after the
Help:
Try 2 tooth less on the pinion.
Try 1 teeth more on the pinion.
2 tooth less on the pinion are
possible.
1 tooth more on the pinion is
possible.
TOO MUCH HEAT IS A SIGN OF POOR ENERGY
ECONOMICS. ENERGY TRANSFERRED TO HEAT WILL NOT BE
TRANSFERRED TO FLIGHT TIME AND FLIGHT
