Every R/C boat has a speed control, whether you know it or not...
Really!!!
In the world of radio control, one of the
more important items is the speed control device. Speed controls come in many
different types and are designed for different types of boats. Speed boats and scale
tug boats have a different speed control requirements. Finding the right control for the
right application can be difficult for the novice.
There is a wide assortment of confusing terms (
Maximum Current Load / Maximum Current Rating / Etc. ), to describe what the various speed
controls will handle safely. And it's real easy to buy the wrong one, or more
importantly, the wrong size.
Even when model boat kit manufacturer
recommends a certain speed control system for their kit, the modeler can still get into
trouble. Most of the speed controls used for boats today are the same ones
used in the R/C car industry. The modeler has to be wary, because these
manufactures are always changing and improving their products. So what is available
today, may not be available next year. Remember that the speed controls are mostly
made for cars and not for boats. The technology in electronic speed controls (ESC)
is rapidly improving, but they do not tolerate moisture of any kind. They are
designed for cars, trucks and buggies. There is an exception, where a few ESC's are
made for boats. It's not that you can't use them in boats, just that the
manufacturer's build them for the car modelers.
The speed control simply controls the amount
of energy that flows from the battery to the motor. In other words, it controls the speed
of the boat. Speed controls come in many flavors: Mechanical, Wire Wound Resistor Types, Electronic Variable
Speed Types (Servo Operated), Electronic Variable Types (Radio Operated).
I will cover the types of speed controls and how to select the right one for your
boat. This article will hopefully take the grief out of selecting your next speed
control.
Selecting The
Right Control
When it comes time to
select a speed control for your boat, there are several factors to consider. If you
take the time to consider each of these factors, it will help you select the right speed
control for your application.
1. We use
DC motors in our boats. You need to know how much
"Current or Amps" your motor(s) draw? What is the voltage of your motor
rated in number of cells? (1 cell equals 1.2 volts)
2. Is the motor
direct drive or are you going to use a gear drive system? Gear drives reduce current
loads, lower propeller rpm's to give more realistic speeds and extend run times.
3. What is the diameter of
the prop or screw you plan to use? The larger the prop, and the more pitch the prop
blades have will increase the thrust produced. This will cause a larger load on the
motor, battery and the speed control.
4. How big is your model?
Larger and heavier models need a bigger speed control to handle the bigger
current/amp load. Nuff said.
5. What type of boat is
it? A Deep Vee has a different requirement than a scale Destroyer or Tug boat.
The task for you is to match the right speed control to the job the boat and
you demand of it. For example, speed boats do not require reverse, but scale ships
need a speed control to handle running at very slow speeds. |
|
Does Size Really Matter? Most women say it's not the size, but how you use it. Oh, that's
another subject.... In the world of speed controls, size does matter. Bigger
is better. If the correct size of speed control is not
used, it could over heat and cause a FIRE! This is more likely to happen with
mechanical speed controls which are very inefficient and can sometimes be
dangerous.
This is caused by causing the speed control
to overload. Using a modified motor on a speed control used for stock motors is a
good example. "Speed Freaks" will often fall into this situation.
Most Ready To Float (RTF) speed boats often come with mechanical speed controls. The
modeler often adds a "hot" motor to the boat but doesn't change the speed
control. This can result in disaster.
On the other hand, those who use tugs, scale
warships or tow boats need a bigger speed control. This is because the slower speeds
puts a great load on the speed control. At full speed, the speed control is simply
allowing the full battery power to flow to the motor. But at slow speeds, it must
reduce the amount of energy going to the motors. The process of reducing the amount
of energy flowing to the motor produces HEAT in the speed control.
This heat, if not controlled can cause the speed control to fail. Most ESC's sold
today have heavy duty transistors. The manufacturers even add aluminum heat sinks
to the transistors to help them dissipate heat and cool the speed control better.
Since Tug or Towboats work at lower speeds,
they often also push or pull loads. This can also add to the load that the speed
control must handle. More work the motor has to do will cause it to draw more
amps. The larger the transistors in the ESC, the more amps the ESC can handle.
But as the quality of the transistors increases, so does the cost! Be prepared to
shell out about $50.00 for a good quality ESC with reverse.
Smooth Proportional
Control
Not all speed controls are designed to
operate in the same manner. Be aware of the simple "on-off" or
"step" speed controls. These controls do not give you the smooth
proportional control. This means that the motor increases in speed as you increase
the throttle on your transmitter. This gives you an indefinite range of speed
settings, as opposed to the three normally in a step type of speed control. This is
most desirable for scale boats and ships.
Keep Your Speed Control Happy
As stated earlier, the speed control produces
heat. This heat can build up and damage the speed control. The location of the
installation of your speed control can effect the heat build up. If you install it
in a confined space, a small fan may be needed to circulate air over the heat sink.
Also consider the weather at the time to run your boat. Hot summer days, the sun can
play havoc with the speed control. Pay attention to the heat build up inside the
hull on hot days. Again, a fan may be needed, or just a few ventilation holes may
work.
Novak Rooster Reversible |
