Brushed Motors

• Introduction
• How they work
  • 1. The axle.
  • 2. The stack of laminations.
  • 3. The commutator/collector.
  • 4. The wire
  • 5. Holes or putty - Balancing methods
  • 6. Brushes
• Motors for the Eco 8
• Maintenance

Introduction

Whilst there are several key components in any helicopter, the one component that really makes a difference is the type of motor that powers the thing. The standard Eco 8 is just a basic kit and allows you to purchase any motor, speed controller and other components that suit your personal preference, however most people tend to buy the packaged deal when purchasing the Eco 8 helicopter, which includes the Ikarus “Sport” motor. This article looks at the various motor options available for the Eco 8, mainly concentrating on the brushed design.

How they work

There are two types of motors that are often used in electric model helicopters, brushed and brushless. The two vary in design, function and price. As a typical brushless set up can cost £250 – £350, it is generally out of the reach of the newcomer to the hobby, who tends to be on a fairly tight budget. This article will therefore deal with the standard brush type.

So what are the main parts to a quality brushed motor

1. The axle.

The axle is normally made of hardened stainless steel with a thickness of 3.14 mm. (0,125 inch) with a flat spot at one side for the pinion set screw. Very rarely nowadays we see axles without flat spots.

2. The stack of laminations.

The 3 pole stack is made up out of very thin "slices" of silicone steel, which are pressed together to a length between 21.5 ( minimum regulated size ) and 22.5mm. For protection against damage and rust and prevention of the sharp edges cutting the wire while winding, the stack is often coated.

There are various inside designs used, the most used are the straight or tapered leg (the part the wire is wound around) The difference in these designs is small but can make a difference to the performance of the motor, the more silicone steel material, the more punch/torque.

3. The commutator/collector.

This part is the most important part of the motor together with the brushes. Looking at the collector is easy to discover that it has 3 separated thin segments, which are made of pure copper. These segments are baked on a ceramic insulation material, which is pressed and/or glued on the axle.

4. The wire

The wire is wound around the 3 poles in such a way that it will react in the magnetic field created by the magnets when power is applied to the commutator. If the wire can move it will create 2 things: an unbalance and a possible short circuit in the wires. To protect the wire from moving on the stack the armature will often be dipped in a special corrosion preventing epoxy coating and heat hardened treated for maximum strength. The number of turns around each pole, and the number of strands of wire used generally dictate how the motor will perform. The Ikarus Sport motor has 23 turns of a single wire (referred to as a 23 single or 23 x 1)

5. Holes or putty - Balancing methods

Holes on top or /and epoxy putty on the side of the stack is the method used to balance the armature. This balance is necessary to increase the RPM and to increase the life of ball bearings and bushings.

6. Brushes

The last part is the end-bell, which house the brushes and springs. The end-bell fits over the top of the shaft and has the fixings for the power cables from the speed controller. The current is fed to the motor via a set of carbon brushes, which are held against the commutator by wire springs. Brushes vary in type and hardness and have a profound part to play in the performance of the motor.

Motors for the Eco 8

OK so now you know the components of the motor, what can you expect to get from them. Well in short, most motors will provide enough power to lift the heli off the ground with the right combination of batteries and pinion. The Ikarus motors work well on 8 cells with the stock 10 tooth pinion, however fitting a slightly larger main pinion can increase the head speed and the performance of the Eco dramatically.

The one thing you will notice is that the stock Ikarus motors are expensive, with the performance and power motors having an RRP of £60 and the Sport retailing at £40. Investigation has as yet not shown these motors to be anything special in terms of winds etc. But what alternatives are there, in a word – LOADS !

How cheap do you want to go, how about £4.50, that’s right less than a fiver will get a super motor that will give stacks of duration, and power. It’s called the Hurricane from Overlander Batteries. However you will need a 12 tooth main pinion if used with an 8 cell battery pack and 14 tooth pinion with 10 cells gives it a very spirited performance. The downside it that you can’t maintain the motor by cleaning or changing brushes etc. So it becomes a throw-away item when the performance drops off.

If you want something a bit more powerful and something that has limited service ability, then the next step is a “buggy” or 540 class motor. Most model shops will have a selection of motors for model cars, ranging from £10 - £100. The cheaper versions tend to have fixed end-bells so the only thing that can be done to maintain the motor is replacement brushes and cleaning the commutator using a comm Stick. For around £12 you can get a Team Orion Havok motor which using 10 tooth pinion and 8 cells will give a lively performance. A word of warning though, don’t go below a 21 turn single wind motor as the current drawn will fry a typical 35 – 40 amp speed controller. If you are after longer flight times, with less performance then a 27 turn single wind (often referred to as a stock motor) is ideal. If you spend a little bit more, say £20 you should be able to get a rebuildable motor that can be stripped down and cleaned.
In short, you should be able to find a motor to fit within any personal budget.

Maintenance

Which ever motor you chose its efficiency will decrease as it is used as carbon deposits build up inside the motor and arching damages the copper on the commutator. If you have a rebuildable motor you should remove it from the Eco and dismantle it for cleaning after every 20 flights or so. Most motors are zero timed, however it’s worth making a mark in the end-bell and the can so they end up back in the same place after the strip-down. Un-clip the springs and remove the brushes, then undo the two screws securing the end-bell. Remove the end-bell and place to one side. Inside the can there will be a retaining disk, which needs to be rotated so the slots line up with the dimples on the inside of the can before it can be removed. Then remove the armature, checking to see if any small washers are left inside the can.

Now squirt some WD40 (damp start often used on cars) inside the can to release the carbon deposits. This may need repeating several times, with the application of a paper towel to wipe up some of the fluid. The can should then be rinsed in warm water and left in a warm location (airing cupboard is ideal) to dry. Now do the same to the end-bell and the armature, making sure you don’t lose any washers or insulators.

Once dry you can re-assemble the parts, however you should also polish up the commutator by placing 1000 grade wet and dry paper on the com and gently rotate it whilst applying pressure with your thumb and fore-finger. Always rotate in one direction and not back and forth. Now once assembled install a fresh set of brushes and re-align the timing marks, job done!