Slot Car Tuning - Part 1


	Tuning Your Slot Car - Advice and Tips by Mark Rampling - Dunton Slot Car Club Many thanks for allowing us to use this on our site.

	1. Ideal Handling I prefer a car that is stable going into a corner, and has just the right amount of grip to slide the rear end a little when powering out of a corner. I believe this to be the quickest way round a corner. If a car has too much grip at the rear it tends to dig-in and tip out of the slot without warning. If the car doesn't have enough grip at the rear, it will slide too much, it can't put as much power down and it will be slower down the next straight. The quickest, smoothest and most consistent way is to just have the rear end slide a little, so that the driver can see that the car is on the limit of adhesion. For the best race times it is far better to have a quick car that is easy-to-drive, rather than the out-and-out fastest car that is difficult to control. The factors that influence the handling of a car are (in no particular order): your driving style; the model of car being used (its height, width, weight, weight distribution, centre of gravity, motor layout, length from guide to rear axle, rear end overhang); controller resistance; whether the chassis is flat and free of distortion; friction in the guide system; type of braids; motor characteristics; gear ratio; friction in the motor/gears/rear axle; how true the rear axle/hubs/tyres run; rear tyre size & rubber compound; how 'floppy' the front axle is; fit of the body to the chassis; additional weight ballast. I will try to cover most of these in this document. 2. Driving Technique Slot car racing is all about what I call "controlled aggression" - running as close to your car's limit as you possibly can, for as long as you possibly can, without actually going over that limit and falling off. Watch a driver who has just been taken off by someone else - sometimes he gets the "red mist" and is able to drive more aggressively and faster in his efforts to catch up again. The ideal is to harness this and be able to drive like this throughout a race! The most important points to emphasise are smoothness, consistency and staying on! There is absolutely no point in being super-quick, but only being able to stay in the slot for a couple of laps at a time. Every time I fall off in a race, I lose up to half a lap before a marshall puts me back on and I can get going again. It is very difficult to recover the lost time without falling off again, so I find it better to calm down, stay in the slot, run my own race and stay out of other people's incidents. I've found that the best race technique for me is "slow in, fast out", meaning fast-ish into the corners, and totally on-the-limit out of the corners. This is the least risk, most consistent performance (from my driving point of view); it keeps the car smooth, stable, balanced and predictable, and gives the fastest race times. When a car is going into a corner, the ideal is for the car to still be braking so that the weight transfer presses the guide down into the slot and stops the car de-slotting. If I start braking too early, I will slow down too soon and actually have to apply power to enter the corner. This is totally the wrong thing to do! When applying the power again, the weight transfers to the rear, making the front of the car go light - so it can more easily de-slot, exactly what I don't need when entering the corner! Alternatively, if I brake too late and I'm going too fast into the corner, at best the rear end will swing round and 'hang' for a split second; at worst the car will fall off. The skill is in lifting off at just the right time to be still braking when entering the corner, but not going too fast and losing time. During practice I go a little faster into corners, just to find where the limit is. In a race I prefer to minimise risk by being a little below the limit into the corners -- unless I'm behind and I'm trying to catch up! It is easy to be slow in the middle of a corner by being on the brakes for too long. Just as it is important to start braking at the right time, it is also important to stop braking at the right time. By coming off the brakes at just the right time and applying the power again, I can 'carry' the speed through the corner. To be on-the-limit coming out of corners, the power is being applied to just make the rear end slide progressively in a single smooth arc, then 'snap' into line at the very exit of the corner. The weight transfer is now to the rear, giving extra grip to the rear tyres but making the nose light. If the car has too much grip, it can dig-in and tip out of the slot without warning, so it has to be driven below its limit just to make sure it doesn't fall out. If the car slides too much, so that the rear is noticeably sideways or even fish-tailing, the power cannot be put down effectively - the car will be slow down the next straight. Some people apply the power too harshly in my view, causing the rear to step out quite noticeably. This isn't the fastest way; it is better to squeeze the throttle for optimum traction and 'drive' into the next straight, rather than 'banging' it down. It may seem less dramatic, but the lap times tell a different story! Over a race distance, there are some things a driver can do to stay out of trouble and achieve a faster race time: Put the lane colour sticker on the front of the car, so that it is not covered by the marshall's hand when he picks the car up. Place the sticker at an angle to other features on the car, so that it is clearly and quickly visible. Try to run your own race at your own pace. Don't try to match someone else who is slightly quicker than you, you'll end up "over-driving" and falling off. If a car is coming up to lap you, let it past - I have seen (and experienced!) many times that the driver about to be lapped tries to see if he can go as quickly as the approaching car, he falls off and takes the other car with him (which is pretty frustrating for the faster driver!). Don't try to overtake someone on the outside of a corner, unless you trust that person not to nerf you off! Try to build up an awareness (almost like a sixth sense) of what else is going on round the track, especially incidents where you may have to slow down. If a car is off across your lane, don't run straight into it as you could be knocked off yourself -- wait for the marshall to remove the other car. If a car comes into your lane, don't try to blast it out of your lane by applying full throttle - drive gently to bring the offending car to the next marshall, and let him remove it. 3. Cars Most clubs run 'box-standard' classes for Sports/GT, Formula One and Saloon. The most popular cars in each class are: Sports/GT The Ninco McLaren has the best combination of low height (& centre of gravity), maximum width and rear track, longest distance from guide to rear axle, minimum rear overhang, wide rear tyres, and even weight distribution (48/52), creating a very stable and easy-to-drive car. Other Ninco cars used successfully at DSCC are the Porsche GT1, Ferrari F50 and Mercedes CLK. Formula One The SCX Indy Lola and Ferrari are very popular, though the Ferrari is no longer available. They are also very stable and easy-to-drive due to their light weight, low centre of gravity and wide rear tyres, and they lap marginally faster than the Sports/GTs. Saloon The Ninco Calibra and Alfa are virtually identical, with any differences between individual cars being down to different motors (normal production tolerances). The Saloons are slower than the Sports/GTs as they are taller (higher centre of gravity) and narrower, they have narrower rear tyres and more rearward-biased weight distribution (38/62). Typically the Saloons tip over more easily, so they are slower into and out of the corners and are more difficult to drive. All of the above cars have relatively low-powered motors, which makes them very driveable and controllable coming out of the corners, but they are slow down the long straights. Scalextric/Hornby cars have faster motors than the Ninco or SCX cars, so they are quicker down the straights and they are becoming more popular at DSCC. They demand more concentration to get the braking right due to their higher speed, and they are slower round the corners as their tyres are not as soft, but on balance I believe they are quicker than the Ninco & SCX cars. The popular models are the Porsche GT1 for Sports/GT, the Jordan for Formula One, and the Subaru Impreza for Saloon. Fly cars are banned from the 'box-standard' classes but they are eligible for the Modified class. DSCC runs a class for Modified cars, which tend to be Sports/GT cars with a different faster motor and soft slick rear tyres. The more powerful motor makes the cars more difficult to control out of the corners and under braking, but they are much faster down the long straights. They need lots of concentration to keep on the track and achieve a fast race time! All the Ninco, SCX and virtually all of the Scalextric/Hornby cars have the traditional 'in-line' motor configuration, where the motor is at right-angles to the rear axle. Some Fly cars have the motor in a 'sidewinder' configuration, so that the motor is sideways across the car parallel to the rear axle. Sidewinder cars have a tendency for the front to jump out under hard acceleration. This can be improved by adding some weight to the front of the car, but this will then worsen the acceleration and brakes. Overall, the 'in-line' configuration appears to be the best compromise on a wooden track. Finally, we also run a Historic class for 'box-standard' cars primarily from Ninco. These Historic cars are narrow, tall and have a high centre of gravity. Combined with very soft, grippy tyres, the cars tend to tip out of the slot very easily. This makes the Historic class the slowest of all - but the old Jaguars, Ferraris & Porsches do look good as they go round the track! 4. Controllers The choice of finger-operated or thumb-operated controller is really a matter of personal preference, with no performance advantage one way or the other. All controllers have brakes (which puts an electrical short across the motor to make it slow down more quickly, rather than just letting it coast). I run Parma Plus controllers that have a very smooth action and therefore a psychological (if not a real) advantage! The electrical resistance of the controller is very important as it affects the speed of the car through the corners and the acceleration coming out of the corners. A low resistance gives higher speed in the middle of the corner when applying the power again after braking, and it gives faster acceleration and more "punch" out of the corners. It feels more "instant" and like a switch. A higher resistance means that the car doesn't accelerate as quickly for the same throttle movement, so it is slightly slower mid-corner and under acceleration. Sometimes you can see a car blip-blip-blipping round a corner, the driver has to keep lifting off because the car picks up speed too quickly and would tip out before the exit of the corner. This typically happens with Saloon or Historic cars run with a 25W controller. Here, a higher controller resistance is needed to give more control, slow the car down mid-corner, and allow the driver to apply the power in one smooth action going round the corner. Another case is when a car jumps and judders when accelerating out of a corner - a higher controller resistance can give slightly less brutal acceleration, calm the car down and give faster lap times. I tend to run 25W for the better handling Sports/GT and Formula One cars, 35W for the more tricky Saloons, and 45W for the very tricky Historic cars! 5. Tools & Equipment To maintain and tune my cars I use the following tools & equipment: Small cross-head screwdriver Small scissors Thin oil (preferably a modeller's pin-point oil pen) Soldering iron, solder & flux Set-up block, see below Adhesives Vaseline Sandpaper Long-nose pliers Brush Modelling knife or scalpel Power supply >1A -- preferably with variable voltage The set-up block is basically a flat acrylic block with a slot cut into it, so that a car can sit on it with all wheels touching the surface and the guide in the slot. I bought mine from SCD (01274682120 £4.50). I have glued copper tape on each side of the slot to replicate the DSCC track when checking ground clearance and chassis flatness. I also connect my variable voltage power supply to the copper tapes via crocodile clips, and use the block for truing the rear tyres (see 6.9). Continue to Part 2