Explaing electric motors, gearboxes and much more here at Rundles

Gearboxes at Rundles- Buy online
Gearboxes at Rundles- Buy online
Gearboxes at Rundles- Buy online
Gearboxes at Rundles- Buy online

Electric Motors

Choosing the correct fixing position for your electric motor

What are the fixing points on an electric motor - ask Rundles


There are 5 main fitting options available as standard, these are standardized throughout the motor industry, so it is irrelevant which brand of electric motor you buy as all fitments should be identical.

  • Foot mount (B3) - This is where there are bolt holes through the base feet of the motor for bolting down to a surface
  • Face mount (B14) - Here the motor is bolted directly onto the fixing plate with the bolts coming off the machine into the motor
  • Face and Foot mount (B34) - Sometimes refered to as B3/B14 this type of fixing has both a foot mount (B3) and a Face Mount (B14). A typical use for this would be where the motor was fitted to a free standing pump and therefore the whole unit is fixed by bolting the motor down by the foot plate
  • Flange mount (B5) - Similar to the Face mount (B3) this fixing type fit directly onto the fitting plate on the machine, except here you can bolt directly into the fixing point or use stand alone bolts whichever is your set up.
  • Flange and foot mount (B35) - Also, like the face and foot mount version this has both options and is sometimes referered to as B3/B5

Mounting Size Chart

  • Frame Size - What is frame size? this size is judged on a motor fitted with a Foot mount (B3) so all motors, irregardless of the type of mount would have a frame size 'as if they did have a foot mount'. A motor with a foot mount placed on a flat surface frame size would be the measurement from the flat surface to the centre of the drive shaft. see fig-1 . So in effect the larger the motor the larger the frame size. All makes of motor will have the same frame sizes throughout the industry.


Frame sizes by Rundles Engineering

Electric motor frame size with shaft diameter chart by Rundles

Image showing the shaft diameter of an electric motor

Chart showing the electric motor shaft lengths to frame sizes

Image showing the shaft Length of an electric motor

Chart showing the hole positions for the length of a foot mount on an electric motor

Image showing hole positions on a foot mount electric motor

Chart showing the measurement for the width between hole centres on a foot plate on an electric motor

Image showing where to measure holes on an electric motor foot plate for the width

Chart showing hole widths on a B5 flange electric motor

Image showing where to measure for an electric motor to match flange sizes

Chart showing hole measurements for a B14 standard face mount electric motor

Image showing where to measure a standard face mount electric motor for the fixing points

Chart showing the spigot sizes for a standard face mount electric motor

Where to measure the spigot on a standard face mount electric motor

How to measure the spigot on a flange type electric motor

Image showing hot to measure the flange for the spigot measurement on an electric motor

Chart for bolt sizes to fit a standard face mount electric motor

Bolt size measurement for a standard face mount electric motor

Motor Speed

The motor speed is represented by RPM 'revolutions per minute' some people describe these as purely rpm's or revs per minute and others may refer to it as 'poles' The reason for this is the amount of windings in the motor, if a motor has two poles its revolutions will be around 2800 rpm (known as a category of 3000 rpm) The more poles a motor has the less speed it can do so if you double the poles you half the speed.

  • 2Pole - Approximately 2800 rpm (categorized as 3000 rpm)
  • 4Pole - Approximately 1400 rpm (categorized as 1500 rpm)
  • 6Pole - Approximately 950 rpm (categorized as 1000 rpm)
  • 8Pole - Approximately 700 rpm (categorized as 750 rpm)

The Power of a motor is described in Kilowatts or it is sometimes referred to as Horse Power - so what is the difference? quite simply 1 horse power (hp) = 0.75 (3/4) of a Kilowatt (kW). Example would be a 2.2 kw motor would be the same as a 3hp motor.

Diagram of the internal workings of an electric motor

Squirrel Cage Motor?

A squirrel-cage rotor is the rotating part of the common "squirrel cage" induction motor. It consists of a cylinder of steel laminations, with aluminum or copper conductors embedded in its surface. In operation, the non-rotating "stator" winding is connected to an alternating current power source; the alternating current in the stator produces a rotating magnetic field. The rotor winding has current induced in it by the stator field, and produces its own magnetic field. The interaction of the two sources of magnetic field produce torque on the rotor. courtesy of Wikipedia

Squirrel cage induction motors sold online at Rundles

Single Phase Motors

Capacitor Start : Capacitor Run and Permanent Capacitor, what does it all mean? Unlike 3 phase motors single phase electric motors don’t have the capability to start running themselves. So they need a little help to get going. Therefore, capacitors were introduced to store energy to alter the current to the motor windings which, in effect creates a rotating magnetic field and induces the electric motor to start spinning.

There are two main types of capacitor used in single phase electric motors and they are Permanent Capacitor and Capacitor Start : Capacitor Run, so what is the difference between the two?

Permanent Capacitor – this capacitor is connected in series with the winding of the motor and helps start the motor turning. One the motor is up to speed the capacitor is switched off automatically.

Capacitor Start : Capacitor Run – Single phase motors with these capacitors on are found to be much more economical to run and produce a higher performance. The main reason for this is that they stay on all the time so remains in circuit which evaluates to much smoother running.

An easy way to distinguish between the two is Permanent Capacitor (Permanent cap) has one and Capacitor start : Capacitor Run (cap start cap run) has two.

motor start capacitors for electric motors from Rundles


motovario and Bonfiglioli gearboxes - ask Rundles

Which Gearbox?

There are Four main questions to ask:

  • Do you want a box which is straight through (inline). Where the power enters one side of the gearbox and the out put shaft is inline with the motor? These are mainly referred to as Inline, Straight through or Helical Gearboxes
  • Do you require a 90 degree angle gearbox?, so the outlet shaft is 90 degrees to the motor. These are mainly called 'Worm Gearboxes'
  • What speed do you require? This will determine the ratio of the gearbox
  • What power motor do you have or want? This will determine the size of your gearbox

View of typical helical gearboxview of typical worm gearbox

There are many uses for Motovario and Bonfiglioli gearboxes, we mention these two makes as, in our (over 100 years) experience, we have seen these grow into the market leaders. A few examples of uses are, Amusement park rides, water treatment plants, factory automation, hoists and lifts, processing machines in the food industry and much more.

Using a reduction gearbox can produce the same or higher torque, and is simply used to reduce the speed of the input motor. To be able to ascertain the correct speed we use 'ratios' to put it in simple terms a 1000rpm motor with a gearbox ratio of 500:1 would give an out put of 2rpm (2 revolutions per minute)

There is a massive mathematical range of ratio's that can be achieved by using combination gearboxes

Non Destructive Testing

Non destructive testing by Rundles Engineers

What is Non Destuctive Testing (NDT)?

Nondestructive testing (NDT) is the process of inspecting, testing, or evaluating materials, components or assemblies for discontinuities, or differences in characteristics without destroying the serviceability of the part or system. In other words, when the inspection or test is completed the part can still be used.

In contrast to NDT, other tests are destructive in nature and are therefore done on a limited number of samples ("lot sampling"), rather than on the materials, components or assemblies actually being put into service.

These destructive tests are often used to determine the physical properties of materials such as impact resistance, ductility, yield and ultimate tensile strength, fracture toughness and fatigue strength, but discontinuities and differences in material characteristics are more effectively found by NDT.

Today modern nondestructive tests are used in manufacturing, fabrication and in-service inspections to ensure product integrity and reliability, to control manufacturing processes, lower production costs and to maintain a uniform quality level. During construction, NDT is used to ensure the quality of materials and joining processes during the fabrication and erection phases, and in-service NDT inspections are used to ensure that the products in use continue to have the integrity necessary to ensure their usefulness and the safety of the public.courtesy of ASNT

Different types of Industrial Fans

Industrial fans from Rundles

Which types do we sell?

  • Centrifugal Fans- These types of fans are classed as a Low Pressure fan with a direct motor drive coupling. These fans can be used for the removal of clean or slightly dusty air. They have high efficiency and reduced noise level, the fans of this series are largely used, ventilation, conditioning, drying, cooling, mechanical draft, and toxic gas elimination plants.
  • Flame Proof Fans- As the name suggests these fans are designed to work in hazardous areas where flammable gas or dust is present
  • Ventilation Fans- Again as the name suggests these fans are used for ventilating large area and buildings
  • Roof Fans- For use in extracting heat or fumes from the roof
  • Portable Fans- At Rundles we manufacture a portable version of the above centrifugal fan, this can be used in a variety of applications such as agricultural grain drying or produce such as potatoes