Fried chips and smokin' motors - Keeping the vital parts of a Scalextric car cool by understanding "duty cycle"

In order for your Scalextric car to give the best and ongoing performance it is necessary for the key components not to get too hot. The key components discussed in this article is the motor and the digital chip (if fitted). This article uses the notion of "duty cycle" to keep your Scalextric cars cool and running well.

Duty cycle
In this World not all machinery or equipment is capable of running or operating continuously. Some equipment needs to be serviced, some may wear out and some may get hotter and hotter in use. This would indicate that the equipment needs a period of rest between usage periods. This "on" verses "off" time is known as the duty cycle.

For example one of our instant soldering guns can be used for 12 seconds but must then rest for 40 seconds to allow the transformer to cool down. After the 40 seconds cool down period it can be used again for 12 seconds, etc. This on / off period is known as the duty cycle for this soldering gun.
Duty cycle may be expressed in time as in the soldering gun example or as a percentage. For example a 75% duty cycle could mean the equipment can be operated for 3 minutes and then rested for 1 minute.

Smokin' Scalextric motors
None of the motors used in any of the Scalextric cars is capable of continuous racing conditions. They are capable of long term use at slow speeds. As the race continues the motor is unable to dissipate the heat it generates and the motor just gets hotter and hotter. That is until the internal solder joints melt and the motor stops working with permanent damage.
Sometimes a tiny amount of oil contamination on the commutator will start to burn and the motor will emit smoke and smell of burning.
It therefore follows that a Scalextric motor has a duty cycle to let the motor cool down between races. All motors, cars and track layouts will be different but to be safe it is best to assume a duty cycle of 50%. That is race for 5 minutes and let the motor cool for 5 minutes, or race for 10 minutes and let the motor cool for 10 minutes. I'm sure you've got the idea by now.

Fried Scalextric digital chips
The Scalextric digital chip is nothing more than some basic electronics and a single micro chip computer to manage the communication side of things. The chip has 3 main sections; the power supply, the micro processor and the motor power drive. Even when operating in analogue the chip is still regulating the power to the motor. Note, there is no overcurrent protection on the Scalextric digital chips.
The power supply and micro processor are well enough designed to not usually cause a problem. The cause of failed digital chips is the motor power drive transistors. These drive transistor turn on and off many times a second to control the power to the motor. The transistor on time and off time is controlled by the micro processor based on the hand throttle position.
When the motor power transistors are switched on they effectively become low value resistors allowing the electrical current to flow through the motor. When the transistors are switched off they effectively become high value resistors stopping the electrical current from flowing through the motor.
When the motor power transistors are switched off there's no current flow and therefore no heat generated within the transistors. Therefore off is no problem for heat generation.
When the transistors are switched on, the full motor current passes through the transistors and heat is generated within the transistors. So, the more on time the more heat generated per unit time. The more on time, the more power to the motor, the harder the motor is working, In this case full speed racing will generate more heat in the motor power transistors and as this heat builds up there comes a point where the internal silicon of the transistor effectively melts. This will destroy the transistor function - fried chip.
Again the Scalextric digital chip has a duty cycle depending on the chip installation, motor, car and track layout. In this case Silicon cools very quickly so a duty cycle of 75% would be OK. However, we should limit the race time to prevent the heat building in the first place. We recommend not racing for more than 5 minutes to prevent permanent damage to the Scalextric digital chips.

Article from Scalextric Car Restorations

How to service the RX motor in your Scalextric cars

Maintain your Scalextric car's RX motor with these simple hints and tips

Abstract

The earlier Scalextric cars produced in the 1960s were fitted with open frame motors the most common of which is known as the RX motor. A motor similar to this was also fitted to many of the Hornby locomotives of the period. This article shows how an RX motor can be serviced in a methodical way by considering the mechanical, electrical and magnetic aspects of the motor.

Introduction

The RX motor was fitted to most Scalextric cars from the 1960s. In order for your Scalextric car's RX motor to give the best possible performance it has to be in the best possible health. Effectively giving the maximum torque for the electrical power available to it. For any electrical motor to give its best 3 key areas need to be considered; the mechanical condition of the motor, the electrical condition of the motor and the magnetic condition of the motor.

Mechanical

Mechanically the RX motor needs to be in the best condition possible to ensure that no energy is lost and the motor can transfer all of the generated torque to the rear axle. To do this several areas need to be reviewed:

• Firstly check and ensure that all the parts are present and undamaged. All missing or damaged parts must must be replaced.
• Check and ensure the motor armature spins freely with no rubbing or tight spots. This could be caused by missing or damaged bearings or a damaged / deformed motor housing.
• Inspect the motor brush holder for damage and replace if necessary.
• Review the motor pinion gear and ensure all the gear teeth are in good condition. Replace the pinion gear if gear teeth damage is found.
• Add a drop of oil to each of the bearing felt pads.
• Ensure the brush spring sleeve is present and in good condition. Replace if necessary.

Electrical

There are many electrical connections and contacts used on the RX motor. Each of these must be in good condition to ensure the best performance of the motor. To do this several areas need to be reviewed:

• Firstly check and ensure that the solder joint between the wire from the pick-up brush and the eyelet that fits over the brush spring sleeve is complete and sound. Replace or remake this joint if any of the wire strands are broken or not making contact.
• Inspect the eyelet for any dirt or metal oxides that may have formed over the years. Clean the brush spring back to clean shiny metal where it contacts the motor brush.
• Inspect the brush spring for any dirt or metal oxides that may have formed over the years. Clean the brush spring back to clean shiny metal where it contacts the motor brush and the screw that secures the magnet.
• Inspect and clean the motor brushes removing any dirt, oil and carbon deposits. Ensure the carbon block is present and securely attached to the brass strip. Clean the motor brushes back to clean shiny metal where they contact the brush spring and eyelet.
• Remove any dirt, oil and carbon deposits from between the commutator segments of the armature.
• Remove any dirt, oil and carbon deposits from the commutator.
• Check the three solder joints that secure the armature windings to the commutator, remake these joints if necessary.
• The electrical connections for a car with an RX motor are:
  • Contact: Track braid to track rail
  • Contact: Braid contact to track braid
  • Solder joint: Wire to braid contact
  • Solder joint: Motor brush sleeve to wire
  • Contact: Motor brush to motor brush sleeve
  • Solder joint: Motor brush carbon block to motor brush
  • Contact: Commutator to motor brush carbon block
  • Solder joint: Armature wire to commutator
  • Solder joint: Armature wire to commutator
  • Contact: Commutator to motor brush carbon block
  • Solder joint: Motor brush carbon block to motor brush
  • Contact: Motor brush to brush spring
  • Contact: Brush spring brass bolt
  • Contact: Brass bolt to eyelet
  • Solder joint: Eyelet to wire
  • Solder joint: Wire to braid contact
  • Contact: Braid contact to track braid
  • Contact: Track braid to track rail

Magnetic

The magnetic field used by the RX motor is provided by a permanent magnet at the rear of the motor. The magnetic field reaches the outside of the armature by the use of steel plates that are also used as the housing for the motor. To ensure the magnetic circuit is maintained the RX motor uses various materials to ensure the magnetic field is not reduced. Over time the magnet can lose some of its magnet field strength thereby reducing the motor's torque and top speed. A replacement Neodymium magnet is available to restore and improve the RX motor's performance.

• Ensure the magnet is secured by the correct brass screw.
• Ensure both the steel housing plates make good tight contact with the magnet.
• Ensure the aluminum plate adjacent to the magnet is fitted correctly.
• Ensure the brass plate at the commutator end of the motor is fitted correctly.

General

Through experience we have found that some RX motors still do not perform well even with all of these checks completed. This may be caused by a weak magnet or internally damaged armature windings. These faults are outside the scope of this article. There are many other possible faults with the earlier cars with the open frame motors. This is intended as a simple fault finding guide only. If the information above does not resolve the fault then contact us for further information.

About the author:

Gary Harding has been working with Scalextric cars for over 30 years and now operates Scalextric Car Restorations in the UK. Scalextric Car Restorations is a Worldwide internet based business that offers for sale high quality Scalextric cars and Scalextric parts from the 1960s to the present day. All the restoration work is carried out to the highest standards with the highest quality parts available. Only the best cars are selected and the final result is a car that is genuinely like new.
Further help and advice relating to this article or Scalextric cars in general can be found at:

http://www.scalextric-car.co.uk

Scalextric service kit for the vintage Scalextric RX motor

This new service kit can be used on all the vintage Scalextric RX motors used in Scalextric cars including the ‘Race Tuned’ versions with the black coloured frames.

The kit comprises:

• New wiring with motor terminals
• New brush spring with sleeve
• New brushes

We often find that replacing the worn out brushes, the corroded brush spring and the frayed wires along with a good clean can revitalise these great old open framed motors.  It’s also worth checking the motor spins freely with no tight points and adding a drop of oil to the felt pad at each bearing.
Some more great tip from Scalextric Car Restorations

Scalextric pre-wired Johnson 111 motor assembly

The Scalextric cars produced during the 1070’s were generally fitted with the Johnson 111 electric motor.  The long thin, gold can motor has proved reliable enough over the years but can fail due to over lubrication causing overheating and eventually a total burnout.  Repairing a motor that has failed in this way is not really an option due to the difficulty of the repair.
The best option is to replace the failed Scalextric Johnson 111 motor with a refurbished motor.  This Scalextric Johnson 111 motor is refurbished and fitted with new wires, pinion gear and guide.  Which means it can be fitted by anyone with no special electrical skills.

Your classic Scalextric car will be up and running again in minutes giving you all the fun you remember.
Another great Scalextric spare part from Scalextric Car Restorations.

Scalextric cars with too much lubricating oil

Scalextric cars are electro-mechanical devices that need the moving parts to be kept in good condition.  Taking this view from time to time is very helpful especially when we maintain the older Scalextric cars.
The most frequent failure with the old open frame Scalextric RX motor is that of excessive lubrication.  Lubricating oil is good when applied to the right places, oil is bad when applied to the wrong places.  When we service an RX motor we remove oil from the wrong places and put oil in the right places.



The worst place for oil is the commutator of the RX motor as this mixes with the carbon dust from the motor brushes to form a conductive paste which shorts out the commutator segments.  This leads to overheating of the motor and eventually failure of the solder joints that join the armature wires to the commutator.  Once the solder joints fail the motor stops working.

The other place oil is not welcome is on the rubber tyres.  Oil will impregnate the tyre and make it go hard and brittle in just a few weeks.  So, remove all oil that gets onto the tyres immediately, especially if the car is to be placed in storage.

Another great insight from Scalextric Car Restorations

Service kit for the Scalextric RX motor

A new service kit is available for the vintage Scalextric RX motors.  These open framed Scalextric motors were used from 1960 through to the mid 1970 on the majority of the Scalextric cars produced in the UK.  The service kit contains everything needed to get an old and tired motor back to full health.



The service kit contains:

• New wiring with motor terminals
• New brush spring with sleeve
• New brushes

Another great service product from Scalextric Car Restorations

Scalextric slot car motors that smoke

We frequently are presented with older Scalextric cars that emit smoke when power is applied.  Very often the motor runs slow too.  The common interpretation is that the motor is “burned out” which is far from the case.  This mostly affects the Scalextric RX motor, Johnson 111 motor and the Raymond motor.



The smoke is caused by oil burning off which is heated by the electrical current flowing through it.  The oil has become conductive as it has been mixed with carbon dust from the motor brushes.
The answer is very simple.  Dismantle the motor and clean away the oil / carbon material.  With this done and the motor re-assembled, 90% of motors come back to full health.  A small, half drop of light engineering oil should be applied to the motor bearings.

Another great insight from Scalextric Car Restorations