If you are experiencing Wrenn 152 AC Vibrator-motored Cars for the first time it may well be that you have opened the cars and wondered how they actually work since they do not have a recognisable motor. I have heard many descriptive comments over the years and the nearest I have discovered is that the vibrator motors are likened to an old door bell. I apologise but the following is a bit like a school Physics lesson but it may assist with your comprehension of the principles, so please bear with me. When the electrical power is applied to the coil around the metal core it becomes a magnet which attracts a plate (armature) and when this gets to a certain point the current is cut off. This in effect then de-magnetizes the metal core so returning the plate to its ‘rest’ position and then the whole cycle starts again. Each cycle only moves the Ratchet Wheel on the rear axle a few teeth but then since the power is automatically switched on and off quickly it is sufficient to move the car very rapidly and also gives the vibrator motored Cars their unmistakable buzzing sound. Coupled with this is the ability to free-wheel around corners which then requires a very different driving technique.

I would strongly advise anyone who has AC Vibrator-motored Cars for the first time to consult the AC version of the A10 – Wrenn 152 Instruction Manual for initial set up and tuning advice. However you may need the following additional advice when using the Wrenn 152 AC Vibrator-motored Cars for the first time since they will not be new and they are all now over 50 years old. They just need a little care and attention and they will continue to hopefully provide many more years of pleasure.

• Firstly check that the Contacts are clean – I use a small piece of very fine grade of emery paper slid between the silver contacts and then turned over and inserted again to clean the opposite one.
• Secondly check that the Contacts actually touch each other in the ‘rest’ position, especially if you have carried out the above. Then check that there is a gap between the Contacts when the Armature (plate) almost touches the magnetized metal core. Gently squeeze the Contacts together or slightly open them up, as required. The armature should just break the contacts at the end of its travel.
• If you are still experiencing problems it may be the Pawl which is causing the issue – the black Pawl has a very thin, clear nylon filament which keeps the Pawl assembly engaged onto the Ratchet Wheel and is retained in a recess in the Armature. The filament can be worn (meaning that it is bent, it should be straight) or it can have slipped out of the small recess. If you flick it out, the Pawl can be rotated backwards and the filament checked. The filament can be easily reinserted into its recess again with a very small screwdriver and without any components being removed.

If you are a recent Wrenn 152 convert it may be that you have just bought the Wrenn 152 Set or Track and if you are using pieces of Track for the first time the track sections may well not have been used previously for a number of years. If this is the case, there could be rusty sections of the conductor rails or even sticky deposits on the Track surface which will all inhibit your Cars running smoothly. Very often after all of these years some items of Track can also have a discolouration of the grey polystyrene surface.

• I always clean the conductor rails first and should any of them have any rusty sections these can be cleaned with a track cleaning eraser. These erasers can be bought from a model shop, which are meant for the cleaning of model railway track or you can use one of the fibreglass erasers for more stubborn areas. This latter item is like a large pencil and has a number of very fine fibreglass strands which protrude from the end and are extended by a twisting action, similar to a propelling pencil. If you have not used one of these previously, do please be careful, the used filaments can get everywhere and they are a distinct irritant when they get into the skin or extremely dangerous if inhaled. After this I use liquid lighter fuel, which is luckily still available, and this will remove most ‘other’ deposits and give the conductor rails a final clean.
• Then I look at the connectors on the end of the track rails. I use the same process to clean these as above cleaning the top but also both sides of each. Usually the connectors themselves only become rusty in a very few cases, so a quick wipe is usually all that is required.
• There is another point to consider here and that is to look at, and also feel, the top surface of the rail at the end of each where they connect to another piece of Track. Sometimes the steel conductor rails have a distinct burr at the end of the rail on the top surface. Since this is where the car Collectors run over this joint on every lap, if it is standing up it will eventually wear the pick-up wires meaning that the Collectors will need changing more frequently. Whilst I appreciate that these items will have been in use from the day that they were originally purchased, just a little bit of fettling will ensure that they continue to provide a good surface for your cars to run on. I usually just run a fine file over this carefully to remove the burr, leaving a smooth running surface. This can be checked easier by fitting another piece of Track to the one that you are cleaning and then just feeling the conductor rails.
• At this point I usually make up a layout with all the pieces of Track available and see if the electrical circuit on each lane, both outer and inner conductor rails are working. If there is a ‘break’ at any point in the electrical continuity, I insert a thin screwdriver into the underside of each of the relevant connectors, at that track joint, and gently twist it. This opens out the sides of the connector to widen this slightly to ensure that it is fully mating with the open end of the adjacent Track rail. Then you should have all of the pieces of Track operational.
• Next the Track surface should be addressed. Depending on the condition of the grey polystyrene will mean varying degrees of treatment to clean it. The very first step is to use a light detergent on a damp lint-free cloth or paper towel. After this you can determine if a deeper or alternative clean is required. I then again use the liquid lighter fuel which will remove most ‘other’ deposits. I have noticed that some pieces of Track over the past fifty years can discolour with a yellowish film and the lighter fuel can remove this with a bit of ‘elbow grease’.
• Finally you will be able to assemble your track in a layout of your choice and have reliable running. Once you have initially carried out the above it will be easy on subsequent use to just give the Track a quick dust to clear out anything that may have fallen into the track slots in the meantime, from when you used it previously, and then you will be up and running.

Prompted by the influx of new converts wishing to try Wrenn 152 for the first time, this section aims to assist them when purchasing a Set, or individual items, to easily recognise the difference between the two different Controllers. As the majority of you may already know, Wrenn did ultimately manufacture two different types of Controllers for their different motors within the two Car types.

At the time that Wrenn first introduced their Formula 152 range of slot cars in 1960, you have to remember that slot racing was really its infancy with a number of companies entering this new mass-production market with slot racing products for home use for the first time. So new and different technologies were being tried to find the best solutions for each different manufacturer. Whilst I do appreciate that various different company products had sporadically been available since the 1930’s but it seems to have been only after the rail racing hobby had taken off in the 1950’s that the improvement to using a slot as an alternative which ultimately forced the rail racing fraternity to adopt this new style of racing.

Since there were no readily available motors small enough to fit into their new 1/52 scale Cars, Wrenn decided to design their own motors. The first Cars were powered by a vibrator motor so the E1-Controller was designed with a simple spring-loaded on/off button. This was similar to Scalextric’s solution to controlling their first tinplate cars although that company’s solution was to combine the two controls into one unit and their cars did have relatively standard rotary motors.

Wrenn did provide an option of having their Controllers either permanently fitted to a baseboard for use or just as a method of retaining them safely when not in use. In order to fit the Controllers to a baseboard they were provided with a pair of Black polystyrene slider rail sections with each having two countersunk holes to accommodate 2No fixing screws and an angled side. The Controllers could then be slid between the pair of rail sections and either used directly on the baseboard (similarly to the unit that Scalextric was using as described above) or having them just retained there for protection and then removed for racing. Please see the accompanying photos.

One of the distinct advantages of using a Vibrator motor was that when the power was off, the car could just free-wheel. So driving the Car effectively was to use its ability to power down the straights and then free-wheel around the corners. Wrenn also developed a way of limiting the maximum speed of the motor to enable young children or new drivers to become accustomed to using the slot cars and also to provide another Car, under its own set speed, for individuals to race against. This was achieved with the Cars having their own Speed Control Lever under the Car and for the latter use, the Controller could be locked in the ‘on’ position with the smaller Red slider button.

During 1964 Wrenn introduced their new DC-motored cars and this necessitated the use of a new Controller. This was designated as a Mk2 version of the E1- Controller and whilst it retained the previous style of a Black polystyrene top cover with the addition of a small plinth, a new base was needed to accommodate the additional, but very small, resistance coil which gave the new controllers their variability of supplying the DC power. This meant that the original Red on/off button needed to be upgraded, which was done by enlarging the button to provide a longer travel. The slider button was retained and therefore the controller could now be locked at a set speed since the DC motored Cars did not have the Speed Control Lever to pre-set the speed of the Cars as previous and therefore all control of the Cars was now concentrated within in the Controller. Wrenn also did provide a speed limiting screw under the base. With this increase in overall height of the Controller it also meant that the previously supplied slider rails were now obsolete. So these items are normally found either within the early Sets or within the separate E1-Controller cartons.

So even if you cannot see the identification text under the Controller it is still possible to easily identify the two different versions by firstly looking at the height of the main button and then looking at the height of the base. Please see the accompanying photos to appreciate the differences described.

Ideally the E1-Controllers should be used with the Vibrator-motored Cars and the Mk 2 versions with the DC rotary-motored Cars as Wrenn intended, but it is possible to use an early E1-Controller with a DC Car and vice versa. The only problem that will be encountered is with the actual type of power supply that you intend using. Whilst a Vibrator-motored Car can easily run from a DC supply, the DC Cars cannot run from an AC supply. Another issue with using an E1- Controller with a DC car is that the power will either be on or off so the Car would be almost impossible to control.

At the recent exhibitions that I have attended, I have successfully used a 12 volt DC power supply for both Vibrator-motored and DC Cars, along with the corresponding ‘correct’ Controllers. The only downside is a relatively minor one, of an inconvenience, with having to clean the Vibrator-motored Car’s Contacts a little more frequently.