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radio controlled model boats, R/C, scale, BaD, Dumas, Crockett, Monterey, Warship, ship, model, 1/96, wood, balsa, plank, strip, craftsmanship

All about Motors
by Roger Harper
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Page 2 of 3

There is an entire language that you need to understand when talking about motors.  Current draw, turns, winds and even timing can be confusing.  When each is taken one at a time, this complicating lingo can be easily understood.  Because some of the motors we may use come from the R/C car-truck world, I have included this information as a reference.

Armature Turns & Winds

Number of turns

The number of turns, usually 6 to 20 for modified & always 27 for stock, refers to how many times the wire is wrapped around each of the three (or more) poles of the armature.  The number of turns will let you determine how many rpm's one motor will have compared to another. 

The lower number of turns will mean more rpm's (less wire on each pole = less resistance).  It will also mean the motor will let the current pass through it faster & drain your battery much quicker.  Low turn motors would be a better choice for planning hulls, deep Vee's for example.  High RPM motors are a good candidate for a gear drive system if used in a scale application.

A motor with more turns will have more resistance & turn less rpm's but will produce more torque.  Higher turn motors are easier on batteries and will allow you to use a large propeller before having to use a gear drive system.  High turn motors work better for scale ships and work type boats..

Number of winds

The number of winds refers to the number of strands of wire wound around each pole on the armature.  A typical stock motor is wound with a single piece of 22 gauge wire.  To make the motor faster with the same number of turns you can go to a bigger gauge wire like 21 or 20 gauge, or use 2, 3, or more pieces of smaller gauge wire all wound at the same time.   As an example, if you were to unwind a triple armature you would find 3 pieces of wire on each pole.  Using multiple pieces of wire decreases the resistance thus making it turn faster.  A motor with more winds will have less resistance & turn more rpm's but produce less torque.  Higher wind motors will need to use some type of a gear drive to turn the motors torque into usable rpm's.

Motor Brushes

Brush Compounds

Silver - offer the highest performance by producing the most rpm & power but require the commentator to be trued more often.  Use with higher turn motors 14 to 17 turn modified and all Stock motors.  Silver compound is for serious boat racers only because of the wear they will cause to the comm.

Standard or Copper - offer good performance for general purpose and racing applications.  This compound is easier on the commentator than softer silver compounds.  The standard brush lasts longer than silver brushes also.

Brush Types

Laydown - This is what is used in most new stock motors.  This brush is wider than it is tall for greater brush wrap around the commutator.  This makes the motor produce more rpm.

Normal - This is what comes in modified motors.  This brush is taller than it is wide.

Dual - This brush is designed to be used in either application above.

Brush Faces

Smooth / Full-Face - has a smooth face with no grooves in it.   Takes longer to break in.  For use if you want to cut your own brushes.

Serrated - has small grooves molded into it to break in almost instantly.

H-Cut - have the face of the brush cut into the shape of an H.

There are many different brush face types.  Each manufacturer will tell you that their brush face cut will be the best.  As a general rule the more material that is cut away from the face of the brush the more rpm the motor will gain.   However as the motor gains rpm in this manner the torque of the motor is fading away at the same rate.

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