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TRACK DESIGN by Chris FrostThis is an edited
version of 2 articles originally published in BSCRA’s "Slot Car Racing News"
magazine. Articles in this magazine cover all aspects of track design and
construction. So is this going to enable you
to design the track that will be everybody’s favourite track? No of course it's
not - ask five slot racers which is their favourite track, and they could easily
come up with six different answers. Ask them why they like or dislike particular
tracks and you'll also get a variety of answers. You can try and limit people's
answers to the design of the track, but the tracks they like best will also be
influenced by questions like are the club members friendly, are they well
organised, what's the clubroom like, how well is the track built and maintained,
is the power consistent and adequate, are the lap counts reliable and is there
convenient car parking. I am not attempting to coverall these issues , this is
an article about track layout design, other aspects of track construction will
be covered in a separate articles. Why not design it like a real Grand Prix track? In the early days of slot racing some people tried building replicas of full size racing circuits. Trying to produce a true scale model of a real circuit is impractical - for example a 1/32 model of the Silverstone Grand Prix circuit would have a lap length of 160m (525 ft.) and take up a space about 53m (175 ft.) by 33m (65 ft.), (add 33% to these for the 1/24 version). Also a 1/32 scale replica of typical full size Grand Prix 5th. gear corner would have a radius of about 4.5m (15 ft.) (scaling cornering speeds properly produces unexpected results, but I’m not going into all that here). Full size circuits have large areas of paddock, car parks etc. so the layout doesn't pack as much track length in a small space as the average slot car track. Thus the replicas of full size circuits have layout plans that look a bit like their full size counterparts but in fact are nearer the scale size of a kart track. Many of the features of slot track design (explained in the rest of this article) are not relevant to full size circuits, and many of the features of a full size circuit (gravel traps, paddock areas, car parks etc.) are not relevant to slot car tracks. In short there are lots of reasons why the two should be different, so its hardly surprising that slot racing replicas of full size circuits are now rare. (Even in HO scale a huge 199ft. Le Mans circuit set up annually in Derby for the 24 hour race is only about 29% of the 1/64scale lap length of the full size circuit). If you want to add a little realism to a slot track add some scenery and a pit lane in positions where they don’t get in the way, and won’t be damaged by crashing by slot cars. Home track advantage Some clubs aim to build a track that gives them a home track advantage. I am not going to debate if putting visitors from other clubs at a disadvantage is a good idea - I'll leave that to you! However all clubs should be trying to encourage newcomers to slot racing. Immensely complex designs that beginners cannot get round are not a good idea - If beginners are not to be discouraged they need to be able to get round without falling off several times a lap, (although they are bound to be slow and fall off several times a race). Tracks that are not too difficult to get round, but need a lot of knowledge to get round really quickly are certainly a reasonable option. Corners that open up or tighten or change camber are more tricky to learn than constant radius flat bends. Esses can be another source of home track advantage (they inevitably open out or tighten up on some if not all lanes). Tracks that are quite unlike other tracks (e.g. very long straights, (or conversely) the lack of any reasonably long straights, or with dramatic hills) will give a home track advantage, but will probably put the members at more of a disadvantage on other tracks because their cars (and perhaps their driving) will be set up to suit the "home" conditions and won't suit anybody else's track. I don’t intend to tell you what track layout you should have - that’s a matter for the club. A variety of track designs makes racing all the more interesting! What I will try and do is explain the various aspects of track design, the advantages and disadvantages of various features. The design of almost anything involves thinking about the various things you want the design to achieve, working out how to achieve them, recognising that some of them are in conflict, and coming with the best balance between the various conflicts. To put it another way, you are not likely to be able to design a track (or anything else) without some compromises. I do intend to explain what needs to be thought through to design a good track, and leave it to you to decide what's most important for your track. I am assuming that you have a club room. Much could be written about how clubs obtain their club rooms and how they pay for them .. but I’m not going to write it now! Tracks used for BSCRA Championship events must have at least 4 lanes and a lap length of at least 15m (50 ft.) although very few BSCRA clubs have tracks much under 25m lap length. What is the minimum practical length for club racing? The practical minimum is more question of lap time rather than lap length - if I can give an example the 16.2m GROPE track has a sports car lap time of around 3.2 sec. and is really too short, where as the 14m Scalextric club track John Reid used to run had a lap time of just under 6 sec. (with a MRRC F1) which was perfectly adequate. The space a track will occupy depends on the layout but to give some idea a 16m 4 lane track can fit in the area of a single garage, but of course you need room to walk round it so the minimum clubroom area is about twice that size. To start designing a track decide how many lanes you want. Four lanes are sufficient for most clubs, but If you have the space and members you could have 5,6 or even 8 lanes. 2 lanes are usually enough for a home track this will take up much less space than is needed for a club track. The next stage is to measure up the club room making a note of the positions of doors, pillars and any other fixed obstructions.. don't assume you know how big the room is, measure it! Up to this point I have asked what sort of track does your club want and how much space do you have - these are decisions the involve the whole club. The next stage is to design the layout - I would advise against trying to design by committee - one or more club members should go away think about it carefully, and draw one or more track designs. Track layouts to need to be drawn to scale (If you haven't got a drawing board then squared paper can be used) - designs that look good on the back of a fag packet usually have serious flaws when drawn up properly! Here are some ideas to help with the design. Lane Spacing A lane spacing of at least 100mm (4 in.) is recommended, a little more is desirable for 1/24 cars (8 lane tracks are often built at about 110mm - 4.3 in. lane spacing). Barrier
PositionBarrier
Position Modern tracks are designed so that the tail of the car does not touch the barrier in normal running. Years ago some clubs saved a couple of inches by placing the barriers closer to the slot, and long cars could be cornered with the tail rubbing on the barrier. These days that is likely to result in bodywork folded up in the rear tyres. Assuming you are going for a modern design, the gap between the slot and the barrier should really be a minimum of 100mm on straights and the inside of corners (If you really need to save some space you can go down to 75mm (3 in.) in places where the cars won’t be wiggling), and at least l50mm (6 in.) is recommended on the outside of corners and for at least the first 60cm (2 ft.) along the following straight. The important thing is not to bring the barriers closer to the slot too abruptly on the exit of corners (see diagram 1) - otherwise a car cornering with the tail out will come into contact with the barrier with a resounding crunch risking damage to his car (and to your hearing when the driver points out the advantages of more careful track design!)
The track width can be calculated by adding the lane spacing and the gaps between the outside slots and the barriers. So, for example, a 4 lane track would have straight about 400mm (16 in.) wide with 100mm lane centres and an 8 lane about 970mm (38 in.) wide with 110mm lane centres. An important point about these widths is that a 4 lane track is narrow enough for a marshal to reach over one track section to another (see diagram 2), this isn’t possible with 6 or 8 lanes - so several space - saving layout options can only be used with 4 lanes. Bridge
Bridge Nearly all British club tracks have one or more bridges, if done correctly (see diagram 3) an odd number of bridges will make all the lanes the same length. (A 4 lane track with constant 100mm lane spacing and no bridge will have an outside lane 1.9 m (6 ft. 2 in.) longer than the inside lane regardless of the layout) There are some disadvantages of bridges - its difficult to marshal cars under them (careful design can reduce the risk of cars falling off under the bridge - I’ll come to that later), and the gradients needed to achieve the differences in height can be a problem. Careful design can minimise these problems but another option is not to have a bridge. It is generally considered
desirable to have the potential lap times on each lane as equal as
possible. Another small disadvantage of tracks with no bridge is that they tend to promote uneven tyre wear. It should almost go without saying that cars handle best with identical size rear tyres. People who have done endurance races on tracks without bridges report uneven tyre wear. At least one team deliberately produced "pairs" of new tyres where the "outside" tyre was larger diameter, when both tyres had worn down to the point where they needed changing the "outside" tyre was the smaller of the two. (So for most of the time the tyres were much more similar in diameter than if they had started out with them the same size). For short races this effect probably isn’t noticeable. It also has to be said that some tracks do cause uneven tyre wear even though all the lanes are the same length - (maybe the outside tyre wears more in long fast corners - anybody got any good explanations of why?). If you are building a home track it may not be worth the trouble of building a bridge, and particularly with a 2 lane track a short cut can be built in to the outside lane to speed up the lap times. Corner Radius The inside corner radius should not be too tight - some people would say at least 15Omm (6 in.) others would say at least 230mm (9in.), and few club tracks have more than one bend as tight as this. In fact the inside bend radius on most corners Is over 30cm (12 in.) and tight Inside bend radii appear to contribute to making the inside lane a 'slow lane'. This 'slow lane' problem tends to be worse in layouts when one lane leading in has quite a sharp radius followed by a large radius where as there is much less change of radius in the other lanes (see diagram 4). This question of minimum bend radius also effects the minimum width a track can occupy, for example a 180 degree bend in a 4 lane track with recommended spacing must have a overall width of 1.15m (3 ft. 9 in). If you are really short of space you could pinch the lane centres and spin out areas slightly. If you need 2 such bends side by side (this Is likely If you are trying to build a track in a very restricted width club room) then obviously the space saved is doubled. A final thought on bends - it tends to make track more interesting if there are a variety of different corner radii and angles so don’t feel constrained - come up with something original! Hills and bankingHills and banking Straights The length of straights is an important feature of track layout. The shortest straight that can really be driven as a separate straight is about l.2m (4 ft.) ... perhaps a little longer if the bends at either end of it are of large radius ... perhaps somewhat less for home set cars. You can certainly build shorter straights than this but when a car is driven round them the corners at either end tend to merge into one continuous wiggle. It is normal to design tracks with a 'main straight' . . . a straight longer than the rest but there is no particular reason why you shouldn’t have the two long straights of similar length if it fits your layout. How long this can be depends on the space available .. many club tracks are in the range 6 to 9m (20-30 ft.) and 10 or 11m (33 - 36 ft.) is long enough for most tastes. It tends to make track more interesting if there are a variety of different lengths of straight. Cars tend to fall out on long straights unless the surface is very good. The 1987-1993 Nationals track had a 12.45m (41 ft. 10 in. ) main straight (and we had plenty of trouble with cars launching on it). On very fast parts of the track this launching problem is certainly made worse by the slightest hint of a convex transition (see the Hills and Banking section above)... this can be due to a joint between two sheets of board, by sag in the board between supports, or just bumps in the tapes. If the middle of a very long straight is a few cm. lower than the ends and the corners at either end tipped up slightly (see above) then the cars will be going over a very slight concave transition along the length of the straight which will help keep them in the slot. Great care will be needed to ensure that there is a smooth concave profile all the way along.. a badly constructed attempt at this design will cause far more cars to deslot. Marshalling Positions The marshals need easy access to the places cars are likely to fall off. They need to stationed where most cars come off - and those positions must not block the drivers view of the track. these days there is the option of a "TRACK" call if a car is in an unmarshallable position - I haven't come across many people who go to meetings to enjoy an interesting variety of track calls, so I think one can safely recommend that tracks should be designed to minimise the number of "TRACK" calls. Marshals can only reach over about 1.2 m (4 foot) of track, (obviously short drivers have rather less reach) so a 8 lane track is about the practical limit of track width. Leaning over 4 lanes to reach another 4 lane corner (see diagram 2) is practical, and a good space saving feature of many a club track. If a marshal has to reach too far they will probably have lean on the track surface, and they will take longer to marshal -either of which could have an impact on other cars! (I have no comment on alleged plans for 12 lane tracks marshalled by boy scouts) Diagram 7 shows the sort of places cars are most likely to end up after falling off. Cars don’t fall off until they start to go round a corner, perhaps the most common driving error is braking too late - and this leads to falling off just after the start of the corner. Another popular place to fall out is on the exit of the corner - (caused by putting on full power too early). Unless the corner tightens up, cars are less likely to fall off part way round, (once the driver has slowed the car enough to get it into the corner they tend not to boot it too hard till near the exit!) Once the car has come out it will carry on in a straight line until it either coasts to a stop or hits something. And where does the de-slotted car end up? If it falls off in a corner ... On club tracks it usually hit the barrier before coasting to a stop; on very fast corners, particularly on the inner lanes of 8 lane circuits the car will often coast to a stop before hitting the barrier. Cars that fall off on the exit to a corner it will continue along the following straight, and as likely as not it will end up in the path of another car. (It may end up in the wrong lane, in which case it is likely to exhibit the classic not braking enough for the next corner routine ... accompanied by some remarks from the driver!) The diagram shows a reasonable place for the marshal to stand - on a big bend a second marshal is a good idea. Are there exceptions to this pattern of falling off? Well if the corner is so fast that you can apply full power before the exit, then obviously you won’t be able to deslot on the exit by putting on too much power. The 180 degree corner before going under the bridge on UK Black Nationals Track must be one of the fastest corners we race on, and deslotting on the exit to that is rare, but not unknown. There are few places where nobody can contrive to fall off - particularly with a bent car! A big 8 lane corner like that with a few degrees of banking is not enough to stop the occasional car deslotting on the exit ... so if you are designing anything tighter or less banked it would certainly be wise to assume cars will fall off on the exit. What does all this tell you? It tells you where the marshal will be doing his thing - so the marshal needs to be easy access to these places. It also shows where the marshal will be most of the time so you can work out how not to block the drivers view; it also tells you where not to put a bridge (unless you want accidents under it!) Cars don’t generally come out of the slot on the straight, but once they have come out they will usually carry on down the straights for a long way before coming to rest. Bridges - where to put them Earlier on I asked do you want a bridge? ... well if the answer was yes where do you put it? A competitors driving error causing his car to fall off and loosing him a second or two is an integral part of slot racing. His error - he’s delayed - fair enough! However tracks should be designed to reduce the chances of one drivers mistake becoming everybody’s accident. (There are other outlets for people who enjoy lotteries!) Bridges block both the drivers and marshals view. Marshals tend to obstruct several lanes when retrieving cars from under the bridge. A good track design should make accidents under the bridge a very rare occurrence. (I say very rare - if you think its impossible to land up on any part of the track running area, somebody will prove you wrong! There are always examples of bad driving and evil handling cars to defeat the track designers best efforts). So where do you put a bridge?
(a) Don’t put corners under a bridge. (b) Don’t put bridges over straights immediately after corners. Diagram 7 illustrates the parts of a straight where cars tend to fall off - on medium speed corners 2 metres (6-7ft.) should be sufficient, on really fast corners try for rather more. Ideally the more space you can allow between the exit to a corner and going under a bridge the better - but see (c). (c) Try to avoid a bridge over
the braking point - (some drivers feel they need to see their car at the braking
point, others have no difficulty in braking the appropriate split second after
the car has gone under the bridge - but they certainly need to see the car
shortly before the braking point).Diagram 8 gives some options for bridge
layouts with some comments on how well they should work. The bottom layout is a
feature of the Haydon track. (The complete layout of this track is shown in the
Oct/Nov 1998 SCRN). This doughnut works well, indeed their previous 2 tracks
have successfully incorporated this sort of feature, and they have no doubt
learned how to do it properly. However, its not all that easy to get this sort
of feature right, particularly the camber / gradient of the road and visibility
- so approach with care! Driver Visibility A pair of 180 degree bends side by side is seen on many club tracks as it makes very good use of the space in many club rooms. Diagram 11 shows how reversing the direction of travel makes a big difference to the areas where marshals need access. The upper half of the diagram shows there is no visibility problem, (and space can be saved by reducing or even removing the gap in the middle). the lower half of the diagram shows that by reversing the direction of travel the marshals will be blocking the drivers view, and space is needed between the straights for marshal access. Good examples of how this works are North London and Bournemouth SRS. There are plenty of other configurations where the direction of travel is important, this is something that need thought when designing a track.
Diagram 12 shows how the barriers can block the drivers view of some parts of the track. The problems are usually worst on corners furthest away from the drivers, there is a better angle to see over the top of nearby barriers. Formula 1 cars are usually the lowest and therefore most likely type of car to be hidden . The options to provide the driver with a better view are:- a) Lower the barrier - Barriers do need to be 5 cm. (2 in.) or more high to do their job in places where there is any significant chance cars will hit them. 5 cm. is about twice the height of the top of a typical F1 car air box . b) Move the barrier further away from the slot - this can work well if it fits in with the rest of the track and does not produce an unmarshallable position. c) Have the track lower - 8 lane tracks tend to be at about knee height rather than the normal British club track just below waist height. This gives the driver a better angle to see over the barriers - particularly if he drivers are standing on the floor. d) Have the driver standing higher - Giving the driver a better angle to see over the barriers depends on the height of the drivers head above the track - so raising the drivers or lowering the track can have similar benefits although there are some limitations with the drivers stood on the floor. In extreme cases (For example some venues for the 6 lane Nationals tracks used prior to 1993) the drivers were stood on a stage at least a metre (over 3 ft.) higher than the track surface, and in need of a pit man to change over their cars during practice. However, normal club tracks have the driver standing no higher than the track surface and close enough so the can reach over and put their own cars on. Raising the drivers rostrum 0.5 m (20 in)or a bit more helps a lot with visibility, but obviously space is needed for sensible (safe!) steps and sufficient ceiling height is needed for taller drivers. e) Transparent barrier has solved many a visibility problem. The only thing wrong with them is that the transparent plastic is not usually as tolerant of cars smashing into it as a MDF or hardboard barrier. This is not usually a problem because its usually the inside barrier that blocks the view and the outside barrier where the banging and crashing occurs. f) The lower part of diagram 12 illustrates how putting the drivers at the right end of the rostrum can make a difference to visibility over the barriers. The driver at the top of the diagram cannot see lane number 4 (blue) properly because the barrier is blocking his view , but if this driver at the bottom of the diagram has an unobstructed view of lane number 4 (blue), so if you arrange the drivers in the appropriate way nobody has a visibility problem. In this example the drivers will be better placed to see past the marshal as well as the barrier (see diagram 10). Although most tracks have the outside lanes at either end of the rostrum, there’s is the occasional design where a potential visibility problem can be solved by putting the outside lanes towards the middle of the rostrum. A good example of this was the Super 8 track (used for the 1997 ISRA World Championships) where Steve Ogilvie avoided a visibility problem on some of the corners by moving the driving positions for 3 lanes to the opposite end of the rostrum. The drivers of the two outside lanes were next to each other, but apart from that the driver stood next to you was driving the next lane. Curiously several drivers thought the driving positions were jumbled at random even though there was just the single change from the "normal" order. A feature of having all the
drivers standing along a straight is that they can block one another’s view of
the track. This can be helped by moving the rostrum back a little way from the
track -everybody standing back by a foot (0.3m) can improve this substantially -
so try and allow some space for people to be able to stand back. It is tempting
to use every last bit of floor area, but this extra space can be quite a big
help in visibility. It helps if the middle lane drivers can get on the rostrum
after the outside lane drivers have arrived! (and some slot racers are not that
thin - remember Jim Huxley?) If clubroom space is really tight then space
rostrum space has to be compromised, but in most club rooms the extra few inches
of track length does not compensate for the need to shuffle the more generously
proportioned racers round the room in the right order. If the marshal is seated then drivers can see over the top of them, but the view of the space immediately behind the marshal will be obstructed. If you are relying on the drivers seeing over the top of the marshal, its advisable to draw it out to scale to make sure where the "blind spots" are (see diagram 14 - I haven’t put sizes in this diagram because the will depend on how high the track is from the ground, the height of the marshals chair, the height of the drivers rostrum etc.) And Race Control ? The race controller does need enough table space for the lap counters, space to work out the results and somewhere to sit down. Most track layouts allow some space for race control, either round the outside of the room, or perhaps in some spare space in the middle of the track layout. Ideally the race controller needs: (a) to see the start line (So he can see if all the cars are on the line for the start, and order a restart if a car fails to leave the line. To help resolve claims for missing / extra laps. To ensure nobody even thinks about adding extra laps!) (b) to see the drivers (So he can see who is missing when everybody else is ready and waiting to start. So he can observe driver conduct and tell the appropriate people to calm down.) (c) to see the marshalling positions (So he knows if the positions are all covered for the start of a race and can invite competitors to fill the empty spaces promptly. ) (d) to see the first corner (So he can order a restart if half the field fall off.) If the track has some sort of automatic timer, or even a computerised race control system, it can be useful for the race controller to get to a marshalling position once the race has started - and preferably get there before the cars arrive on their first lap. Obviously a full time race controller is preferable (and essential to "TRACK" calls), but on a badly attended club night an extra marshal can be very valuable. Its useful to raise the race control position 0.2 - 0.6 m (a foot or two) off the ground - a seated race controller can see past standing people much easier if he’s sitting a bit higher. It can be useful to have race control near the door so he can keep an eye on who is coming and going (and jog the memory of anybody who is leaving without paying their race fees). There is also something to be said for having the race control position out of the way from disturbance by the drivers. Its much easier to add up the results without continual interruptions! I remember the Loughborough club where the race controllers chair was also used as the step up to the drivers rostrum, the race controller was often inconvenienced by drivers stepping up on this chair (particularly if he was sitting on it at the time!) .. this does have a happy ending - eventually race control was moved to unused space in the middle of the layout. Obviously the ideal race control position is less important than getting many other aspects of the design right. A marshal can tell the race controller if cars have missed laps etc. ... as long as the marshal is responsible and unbiased. A little thought at the track design stage can save a lot of trouble later. Door and Windows Its a good idea to allow a reasonable amount of space round the clubroom door. I have seen clubs (which I will not name) where late arrivals at the club room opened the door and rammed a marshal in the back! Also vacating the premises at the end of a club night was worse than getting out of tube train in the rush hour. So try and allow at least twice as much room round the door as you allow round the rest of the track. Lighting needs a little thought. Most club racing takes place after dark, so are the lights in a reasonable place? Its always easier to install extra lights before the track is built. Also will it be possible to change light bulbs / tubes without damaging the track? This shouldn’t be a problem with most track designs, buts it’s worth thinking through just in case. If the clubroom has opening windows, can you get at them to open and close them each club night? Again this is unlikely to change the track design, but just in case.... (On the subject of windows - Does the sun shine across the track straight into the drivers eyes? If so some blinds, curtains or even posters taped to the windows can solve the problem. Can the public see the track through the windows? Is this a good idea? We want to publicise slot racing but we don’t want to attract vandals! In many locations, I think its better if people cannot see in. Opaque film on the glass will solve this problem.) Is the design
suitable? (a) Will it fit the club room? (b) Can the drivers see all the corners and most of the length of each straight. (Remember marshals, the race controller, spectators, pillars, barriers and the track itself could block the drivers view)? (c) Can the marshals easily reach all the places cars are likely to fall off? (d) Are the bridges arranged to minimise the chances of de-slotted cars ending up parked under them? (e) Is there space to get in the club room door and walk round the track? (f) Are all parts of the track accessible? (Cars can land anywhere - visits to the scenery will hopefully be rare but all parts of the track may need maintenance.) (g) Marshals should have easy access to marshalling positions. (If marshalling positions are difficult to get to or uncomfortable the inevitable lack of marshals delays racing) (h) Make sure the number of marshals required isn't too great compared with the likely turn out on a club night. (Its useful to be able to run with reduced marshals, so if possible one person should be able to cover 2 positions. slow marshalling is better than "sorry folks no racing tonight - there aren’t enough marshals".) (i) Is there a reasonable position for race control? (j) If you, are building a portable track think about where the joints are, the size of the pieces and how much space is needed for storage. Good thing you worked it out
when the track was still a paper design so its easy to move the corners and/or
drivers to provide a better solution. Once you’ve worked through that list,
sworn a few times about the number of changes to the designs etc. you should
have arrive at a much better design than your first attempt. Don’t worry about
not having the perfect answer to everything - like so much else in life if you
are looking for perfection you’ll go on for a long long time, and the design
will still not please everybody. Its a good idea to come up with a few
alternative layouts and ask other club members for their views. Hopefully this
will still be the sort of track the club originally agreed they wanted - but if
for example the club wanted a 6 lane track but the club room is only big enough
for 4 then its not too late for a rethink! Try and discuss it in an orderly way
- If for example not everybody agrees on how few marshals you are likely to have
on a bad night, its better to discuss that and come to a decision without
confusing the discussion with other features of the track design. After a bit
more thought, you should end up with a design most people like - and a good job
they do because they are all volunteering to help build it! Now you can plan the
construction... and when you are ready to start thinking about that go to the
series of articles describing how to build your track design.
Copyright © 1998 British Slot Car Racing Association All rights reserved No liability is accepted for this information or any use to which it may be put
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If your layout has one or more bridges you will need
changes in level of the track surface. At least 8 cm (3 1/4 in.) is needed
for marshals hands under bridges. This means hills, and these can be dangerous
to cars if not designed properly. The main problem is the transition from one
gradient to another (see diagram 5). If this is concave (in side view) the cars
will be forced down onto the track as they pass over. This is good at keeping
the cars in the slot but if the transition is too sharp the car tend
to ground and damage the track. This grounding is not generally a problem if the
transition is in the middle of a sheet of board, because the board will not bend
to too sharp a radius. If however the transition is convex the cars tend to fly
out of the slot. Even cars that appear quite slow in a straight line can be
prone to deslot over bumps in the track, and these convex transitions make these
problems far worse. 
