How to keep your slot cars in top running order and tuning tips. Basic Maintenance, Truing Tyres, Motors, Improve Pickup, Gear Ratio.
Below is a basic diagram showing the general overview of the parts in a Scalextric and other models.
Small cross-head screwdriver
Soldering iron, solder & flux
The first thing to do is to check that the chassis is flat. An uneven chassis can cause inconsistent handling between right- and lefthand corners, and cause the car to slew sideways under braking.
Remove the body and the guide, and put the car on a set-up block. The chassis should have a small gap to the track and should not be twisted, with one side lower than the other or one rear wheel up in the air! The front tyres should be resting on the surface of the block, and it should not be possible to lift either front wheel off the surface without lifting the chassis. This shows that the front axle is hard against both chassis "up-stops" at the same time, so the front & rear axles are parallel.
Another check is to press one front corner of the chassis downwards, watch the opposite rear wheel, then repeat for the other side - if both rear wheels lift by the same amount for the same downward pressure, and you cannot see any slack being taken up between the front axle and the chassis "up-stop" on the side you are pressing on, then the chassis is holding the axles parallel and the car should corner the same in both left-hand and right-hand corners. The above checks can't be done on a Formula One car, as they have a separate front axle unit independent of the chassis.
Next, remove the front & rear axles and rest the chassis on the set-up block. The chassis should be flat front-to-rear and side-to-side, with no big air gap.
If chassis isn't flat, it is possible to repair it by using the Slot.it chassis straightening technique!
Gluing and truing slot car tyres will dramatically improve your cars grip, meaning better performance and handling. This technique is mostly used at club and competition level, where cars are usually raced without magnets.
On a Scalextric-type plexi-track with steel contacts, the strength of the magnet and its location in the chassis are dominant factors in the handling of the car. The magnet provides an additional down force, similar to the aerodynamic down force provided by the front & rear wings on real Formula One cars. Just to give you an idea, in some cars the magnet is so strong that it is possible to hold a piece of track upside down without the car falling off!
The effect of the magnet is to clamp the car down on the track, giving higher cornering speeds and better braking. It is more difficult to find the limit of the car, as there is no progressive break-away to warn you when you are getting close - one moment you're on, the next you have flown off at high speed! I find that driving with a magnet on Scalextric - type plexi-track requires a quite different driving technique to driving on a wooden track.
As the DSCC track has non-magnetic copper tape, the magnet in the chassis is redundant. I usually remove it to reduce weight, though I keep the magnet in case we run a challenge event against a club with Scalextric-type plexi-track, when it can be re-fitted.
Make sure that the guide can turn freely in the chassis through its full travel. If it cannot, check for any moulding flash and remove it if necessary, and apply a drop of oil lubrication. If the guide is too stiff it can cause handling difficulties. For example the rear end no longer slides progressively and predictably, and it suddenly steps out when the cornering force is sufficient to overcome the friction. A stiff guide will also not self-centre but will stay skewed to one side when the car comes out of the slot, making it more difficult for a marshall to put the car back on again.
Scalextric cars have a unique problem in that they have sprung sliding contacts to the braids, which provide no self-centring to the guide. At DSCC it is permissible to hard wire the guide for self centring, provided that neither the chassis nor the body are cut away. This is possible with the Porsche GT1 and the Subaru Impreza, but I haven't found a way to do it on the Jordan Formula One yet!
Remove the old guide and throw it away, remove the metal strips and fit a conventional guide (I have found the SCX guides to work best). You will need to replace the lead wires with something longer and more flexible, such as the wire supplied by Oz-Race. Don't forget that you will need a couple of the small eyelets to push into the new guide.
All cars come with hard braids as standard. They last a long time but they are stiff and tend to lift the front of the car high above the track, raising the centre of gravity. I replace them with soft braids that help to keep the front of the car lower. My current favourite is the ultra-thin braid from Slot It, but sometimes I have to use the slightly thicker Pink Kar soft braid to stay above the new ground clearance limit.
I put a 90° bend at the very end of the braid with a pair of pliers, then I feed the braid into the guide so that the bend is at the top of the guide and helps to prevent the braid being pushed through. I then use the pliers to bend the braid against the lower part of the guide with the sharpest, cleanest bend I can achieve. This helps to keep the guide as low as possible in the slot.
The lead wires from the motor have a small metal eyelet with exposed strands from the lead wire poking through it. When pushing the eyelet into the guide, trap the exposed strands between the eyelet and the new braid, to give the best electrical contact. When pushing the eyelet into the guide, press the guide and braids hard down against the set-up block. I usually remove the front axle when I'm doing this, so that all the pressure is only on the guide. This will ensure that the braids are not pushed down out of the guide as the eyelet is pushed in, the bend in the braids is kept sharp and doesn't bunch up, and the guide is as low as possible in the slot.
With Scalextric cars which cannot be hard-wired, I replace the supplied steel braids with softer braid. As supplied, the Scalextric braid comes up from the track surface into the guide, along the top of the guide against the spring contact, then dives down into the guide again and returns out onto the underside of the guide. This return tends to hold the main part of the braid away from the guide, lifting the whole front of the car. When fitting the softer braid, I end the braid on the top of the guide and hold it there with a touch of glue. So the braid no longer lifts the guide out of the slot, and the front of the car sits lower.
Trim the braids to be the same length as the guide. Splay the braids apart to form a 'V', and slightly turn down the very ends to give best contact with the copper tape on the track. Good braid contact is important for a smooth-driving car. On Blue lane on the flyover section, the groove width varies quite a bit and the track height varies on each side of the groove. It is common to see cars stuttering because of poor braid contact, so give the braids an extra tweak before running on Blue!
Bend the lead wires to: (i) make sure that they don't hold the body away from the chassis; (ii) centre the guide in the straight ahead position when the car comes out of the slot, making the marshall's job easier and quicker; (iii) still allow full side-to-side movement of the guide. If the wires are being stubborn, I sometimes use a piece of tape or some glue to hold them in the right place.
Motor response plays a critical part towards the balance of the car when coming out of corners. The motor should be easily controllable; the power mustn't come in with too much of a 'bang' that will cause sliding, wheel spin, fish-tailing or judder. There needs to be a good balance between the motor response, controller resistance and rear end grip to give a smooth, progressive and easy to drive car.
When a motor is brand new, it will have tight bearings and poor brush contact. As the motor runs-in, the bearings will become a better fit to the motor shaft, the brushes will wear to the same curvature as the commutator and stop arcing, and any loose windings will settle and possibly improve the balance of the armature. A run in motor is generally quieter, it has smoother acceleration, more top-end speed and better brakes.
Check first of all that the contrate runs true, by removing the motor and slowly rotating the rear axle. You should be able to see any 'wobble' quite clearly. If there is contrate 'wobble', you're going to have a noisy, power-robbing gear mesh. So throw the contrate away and find a good one.
Then check that the contrate sits centrally on the axle by seeing whether the rear wheels are equidistant from the rear axle bearings and/or the chassis. Quite often they aren't! If this is the case, remove the rear axle from the chassis. Then grip the axle on a nonbearing surface with a pair of long-nose pliers and gently rotate the contrate relative to the axle to centre it. Hold the contrate in place with a drop of Superglue. Make sure that an axle bearing doesn't slide against the contrate at this point, because the glue will run into the bearing by capillary action and ruin it - I use an elastic band wrapped tightly around the axle to prevent the bearing from slipping down.
To move, fit or remove a pinion, it is far better to use a specialist gear puller like the one supplied by Ninco. This avoids the risk of damaging other parts of the motor with the forces involved.
Pinions can move along the motor shaft and out of mesh with the contrate gear. When this happens, exchange the pinion for the same make but with a tighter fit (normal production tolerances). Alternatively hold the original pinion in place with a small amount of solder (brass pinions only!) or glue, making sure that none gets into the teeth.
It is very important to achieve a good, smooth, quiet gear mesh. A noisy gear mesh is robbing power, it can give uneven acceleration and braking, and it is a psychological disadvantage to have a car sounding like a bag of nails! With the motor and rear axle in place but the body removed, turn the rear axle very slowly and lightly by hand in the direction of normal wheel rotation. A good gear mesh gives a consistent feel for the complete rotation of the rear axle. A bad gear mesh will have one or more 'sticking' points, where there is an irregular resistance to rotation (don't confuse this with the normal cogging effect of the motor). Sometimes it is even possible to see the effect of these 'sticking' points, by looking closely at where the motor shaft engages into the hub of the contrate -- a 'sticking' point will make the contrate jump sideways relative to the motor shaft, then back again.
A 'sticking' point is caused when a tooth on the contrate binds against the pinion as it tries to come into mesh. To eliminate the 'sticking' point, you first need to determine which tooth on the contrate is at fault. At a sticking' point, mark with white Tippex correction fluid the contrate tooth that is just about to mesh with the pinion. Carry on rotating the rear axle, it is possible that there will be more than one 'sticking' point, and mark each one.
Then use a sharp scalpel to take off the tiniest sliver from the leading side of each marked tooth on the contrate. This is usually enough to remove the 'sticking' point, but check the gear mesh again and repeat as necessary until you have a smooth, consistent feel for the complete rotation of the rear axle.
The standard gear ratio is 27t (contrate) : 9t (pinion), i.e. 3:1. The gear ratio may be changed only in the Modified class. Ninco supplies a 24t contrate, which with the standard 9t pinion changes the ratio to 2.67:1 and can help to calm down a fast-accelerating, powerful motor. It is also possible to buy 8t, 10t & 11t pinions to change the ratio. Generally, a lower numeric gear ratio will give worse acceleration & brakes but a higher top speed; conversely, a higher numeric gear ratio will give better acceleration & brakes, but a slower top speed. Beware of mixing pinions and contrates from different manufacturers, as they won't always mesh together very well.
With fully tightened fixing screws, check to make sure that the body is sitting properly on the chassis, and that it doesn't catch on anything, trap the lead wires or tension the chassis.
A performance tip is to loosen the front and rear fixing screws by about ¾-1 turn, allowing the body to run loose and float independently of the chassis. This seems to make the car more stable and allows it to be driven harder into the corners. If a screw feels very loose and about to fall out, cover it with a piece of tape to prevent any trouble on the track, or fit a longer fixing screw (supplied by Ninco). If the body is very loose, it can vibrate against the chassis and make a very disconcerting noise, particularly under braking. I haven't found this to be detrimental to performance, though it is a little off-putting! The ideal seems to be to still have the body movement, but to have it damped a little by friction against the chassis - this gives the handling benefits without the noise!
It is possible that the chassis will rub or catch somewhere against the body and restrict its movement, even with loose fixing screws. For example the Ninco Ferrari F50 and Mercedes CLK have the exhaust detail moulded on the chassis but poking through tight-fitting holes in the body, thus preventing the rear of the body from running loose. For the 'box-standard' classes at DSCC, we allow specific chassis detail to be cut away on specific cars, please check the latest rules. In the Modified class, the chassis can be cut away on any car to ensure unrestricted movement.
Some of the Scalextric/Hornby models are fitted with working lights. Again, at DSCC it is permitted to remove them provided that the external lamp detail is retained.
Some people like to repaint the body in their own personal colour scheme. If you're going to do this, (i) don't choose a colour which is the same as a lane colour, because the lane sticker won't be so easily visible to the marshals, and (ii) keep the paint as thin as possible, as you will be adding weight high up and raising the centre of gravity. It does make a difference!
Another tweak for the Modified class is to replace the standard interior with a lightweight vacuum-formed. This has the effect of lowering the car's centre of gravity, and it makes a surprising improvement!
A car's handling can be fine-tuned by adding weight and subtly altering the weight distribution. The added weight improves cornering, reduces sensitivity to bumps and makes the car more robust in clashes on the track, but it worsens acceleration and braking.
As a rule-of-thumb if the front of the car shimmies down the straights or if the car tips too easily, add weight right behind the front wheels as far outboard as possible. If the rear end slides too much, add weight at the rear as far outboard as possible. Beware though of the pendulum effect (once all that weight at the back does break into a slide, it will be very difficult to stop!).
Some people use plasticene when experimenting with the position of additional weight, as it is easy to move or reshape. Once you have found the ideal position, it is better to use small pieces of lead sheet to keep the centre of gravity as low as possible. I usually use Evostick to glue the lead to the chassis, so that I can remove the lead again if necessary.