• Routing Slots In Mdf Lumber
• How To Router Slots In Mdf
• Routing Slots In Mdf Wood

TRACK CONSTRUCTION Part One

I started the jig with 1/4″ thick MDF. Cutting a strip just a hair larger than 1/4″ wide. After some light sanding, I fit it into a test slot I made earlier with the spiral router bit I was going to use to cut the dados. The MDF should be fairly snug, yet be able to slide in the dado without any wiggle side to side. A melamine-coated MDF table will provide the smooth, sturdy surface you need. An aluminum or resin base plate is a must-have for any budget. Good to have features for a great-value router table. A resin router table is a step up from MDF for stability and strength. Choose a split router. Fix the sections to the frame The sections will be fixed to the first layer of MDF (see the Frame submenu) while routing with temporary Tox screws, late they will be replaced with Hex socket screws through the track with Tee nuts mounted underneath the frames MDF. That will keep the sections in.

by Chris Frost

Updated April 2009

Right then, you’ve got this great track design,designed with the help of (or in spite of) the track designweb pages. How do you go about building it? If you’ve got the fundstrack builders like Steve Ogilvie in Canada or theLars Harrysson in Sweden willdo the job for you. If not the only option is to build it yourself.

I’m assuming that your club has enough practical skill tohandle the power tools safely and do a reasonable carpentry job. I would hope itgoes without saying, if you don’t know how to do a job safely DON’T DOIT!

I’m setting out to describe how many good tracks have beenbuilt. No doubt there are many other ways of building tracks - so if you knowanother way of producing a good track then good luck to you (and why not writeinto Slot Car Racing News and describe how you did it). I’m also trying todescribe the advantages and pitfalls of various techniques - but I’m sure Icannot have thought of everything.

There are two types of board most suitable for the surface ofslot car tracks ; MDF (medium density fibre board) and chipboard. Chipboard isthe traditional material, it produces an adequately smooth surface, and is thecheaper option. MDF has been used in a number of recently built tracks, itproduces a smoother surface and a smoother slot, it is better structurally. MDFis a little heavier, but perhaps thinner sheet can be used. The minimumthickness for the track surface is 12mm (1/2 inch), although if you are usingchipboard, a greater thickness is an advantage.

The 'standard size' for board is 2.4m by 1.2m (8ft. by 4 ft.) sheets. Smaller sheets are available, but are almost always muchworse value for money. Joints between sheets make extra work and tend to causebumps so smaller sheets are not a good idea. Its worth shopping around for board- the first do-it-yourself superstore you come across may well be expensive,particularly compared with the prices paid by someone 'in the trade'.

The board that forms the track surface will sag under its ownweight unless some support is provided. The traditional way of doing this was toput wooden battens underneath - a piece running lengthways each side and crosspieces every 40-60 cm. (16in - 2ft,) some tracks used 25x50 mm (2x1 inch)timber, but this was a bit too flexible, and 75mm (3in) depth was moresatisfactory. Timber tends to expand and contract with temperature and humiditychanges at roughly the same rate as the surface boards, so there is limitedwarping problems. More recently MDF surfaced tracks have been built using stripsof MDF on edge in place of the timber. This has the advantage that the track isall of one material so it shouldn't warp. Its likely to work out cheaper becausethere are usually plenty of bits of MDF that are too narrow for track surface,but are usable in the supports. I don't recommend using chipboard in this way,it isn't very satisfactory in this sort of structural application. Incidentallyone disadvantage of MDF strips compared with timber is that wood screws onlywork well into the thickness of MDF, it tends to de laminate if screws are putin edgeways so the screw fixings are a bit weak (although nothing like as weakas screws edgeways into chipboard). The professionals used pinned and gluedconstruction on MDF with extra reinforcing blocks (see diagram A). You can use ametal frame under the surface , but you have to allow for different expansionrates to avoid warping.

The above construction is great for straights, but obviouslyneeds a bit of adaptation for corners. One approach is to carry supports on instraight lines (see right hand part of diagram B) The other is to buildstructural curved edges to the track - these will double as crash barriers. Youare not going to be able to bend a 12mm strip of MDF round a tight radius - thesecret of this is to use 3 thicknesses of 4mm MDF glued together (see diagramB). If this is done properly the finished job will look just like a curved pieceof 12mm thick strip. (To get a good finish use slightly wider 4mm strips and cutit down to the finished width when the glue has dried.)

Unless you plan to run your track on the floor, (Some HOevents are run with the track on the floor) the track needs to be supported at asuitable height. There are various conventions on what is the correct height - 8lane tracks tend to be at about knee height rather than the normal British clubtrack just below waist height.

What do you use to support the track?

One answer is to use anything which is cheap, available andreasonably rigid. For a permanent tracks I’ve seen tables, cupboards, workbenches, oil drums (clean and empty!) in use. These all worked and the clubs gotthem for little or no money because they were in the right place when theoriginal owners were scrapping them. A fair bit of adjustment with packing isusually needed to get the levels right, but as long as the track isn’t goingto be moved then this is a job that only needs doing once.

Some clubs have bolted up a 'Dexion' frame - thisis likely to be a costly option unless you can reuse some Dexion being put in askip. If you don’t manage to recycle somebody else's surplus then what do youdo?

Many clubs have built a timber frame. An adequate timberframe does not need particularly high quality craftsmanship although there aresome well built ones around. (Save the realskill for the track surface!)

Some clubs have used welded steel frames - this is only anoption for clubs with a welder and a supply of cheap steel. Users of metalframes should beware of the differing rates of expansion of steel and wood.Unless the surface is able to move relative to the frame, warping and cracks arelikely.

What about tracks that are not set up permanently? Perhapsthere are tables available in the room where the track is used - if so the trackwon’t need its own legs. If the track does need its own legs then they need tobe easy to fit, remove and store.

A good design of track leg is the type used on Steve Ogilvie’stracks. I don’t think I’m giving away too many trade secrets here as lots oftracks are built around similar lines. Diagram C shows how these legs work. Eachleg is made from a pair of triangular pieces of 12mm (half inch) plywood. Thetwo pieces are bolted together with a single bolt - 10 mm is about the rightsize. The top piece is then bolted to the track - 3 bolts of say 6mm diameterwill do this job nicely. A slot in one piece of plywood allows the complete legto be adjusted in both height and angle (to adjust for slight banking). Thismeans that once the track is set up the level and gradients can be adjustedeasily. These legs allow the track to expand and contract along its length, sothere is little risk of distortion with temperature and humidity changes.Clubroom floors are rarely either level or flat so some adjustment in the legsis necessary even if the track is perfectly built. It the track is in a fixedlocation there is something to be said for using a wood screw or two to lock thetwo halves of each leg together. For transportable tracks this may not be such agood idea, as the next floor its put up on will have the bumps in differentplaces from the last one.

A 4 lane track under construction showing the adjustableplywood legs

The track surface will be made up of several sheets of board.These need to be joined together so that the top surface align. Its as well toaim for a perfect fit, but obviously some tolerance is needed. Diagram D showsthe sorts of imperfection in the joints that can occur. (The diagram exaggeratesthe size of the imperfections for clarity.) The following sizes are what areally good track should have. Steps in the track upset the cars more than gaps.The slightest step up at the joint must be avoided. If you cannot achieveperfect level, then a slight step down ( say 0.1mm .004inch) won’t be aproblem. Obviously a step up in one direction is a step down in the opposite direction, so if you plan to race on the track in the reverse direction stepsneed to be avoided. Gaps between sections look worse than steps, but are less of a problemto the car. Ideally there should be no gap between the sections. However the carwon’t notice gaps the thickness of a couple of sheets of paper. The other typeof imperfection is a change in gradient. As the articles on track designexplained, cars don’t like convex changes in gradient, so avoid them. A slightconcave change will do no harm (providing that it doesn’t result in a convextransition somewhere else) I know one track where there was a concave transitionfrom horizontal to about 1 in 25 gradient at a track joint, This was too suddenfor this sort of transition and it caused the cars to ground and jump about atthe joint. Eventually they decided to make a smooth transition so there was noinstant change of gradient - this was a popular improvement with visitors andhome members alike!

Its likely that joints will get worse with time, so veryaccurate joints when the track is built should mean it’ll be a lot longerbefore any serious maintenance is needed!

Are there some tracks around that are not this good? Yesthere certainly are! Some seem to work OK and some attract complaints. Cars arenot sensitive to imperfect track joints if they are

(a) traveling slowly or

Routing Slots In Mdf Lumber

(b) heavy

(c) on straights

(d) have loads of ground clearance

How To Router Slots In Mdf

(e) are 1/24

(f) are not F1s

(g) are low powered

(h) are not being driven on the limit.

So if you are cruising round with a 1/24 retro-slot car youwon’t be inconvenienced much by bad track joints on slow straights (nor willyou benefit much from excellent track joints!)

So how do you go about constructing these joints? It alldepends on how often the track is going to be assembled and taken apart. If thetrack is going to be built in the club room and is never going to be taken apartthe sheets can be screwed to a continuous supporting structure with overlappingpieces of sheet. Then fill the joint and sand it smooth before painting.

If the track is going to be taken apart and set up for a fewdays at a time, then it needs to be constructed so it’ll go togethercorrectly. Typically a well built large transportable track (For example theBSCRA Nationals track) can be put up in a few hours and taken down in a hour. Aportable track - one that is going to be put up and taken down every club nightneeds to be up and running in 10 or 15 minutes.

If the track is going to be built in the club room and willnever come apart then simple joints such as shown in diagram E will work well.Even if the track will never be moved, you will need access to maintain thetrack under the bridge - so design in a removable section.

Perhaps the simplest way of joining sections for a portabletrack is to build in a batten (or strip of MDF) under the joint; get thesurfaces level; clamp the battens together, drill holes for two dowels and twobolts. (See diagram F) The dowels should be a tight fit - lots of tracks usedowels about 12mm or 1/2 inch diameter. The bolts should be a loose fit, 8mm or5/16 inch are typical sizes for this job. I’ve seen a lot of tracks withdowels for location - You might think it would be an easy way of providingperfect location. Most of the dowelled joints I’ve seen don’t work very well- the usually start to jam so need to be filed down - so they don’t locatevery well. Indeed there’s more than one portable track where all but one ofthe troublesome dowels were dispensed with. They relied on the people assemblingthe track to get the correct height correct across the width of the tracksurface and then tighten the loose fitting bolts. By resting a hand across thejoint to feel when its flat, some people can its set up each joint accurately ina few seconds.

A tongue and groove construction such as diagram G works wellon transportable track. The professionally built tracks such as Steve Ogilviehave a double tongue and groove arrangement along similar lines. The tongue andgroove arrangement produces a simple strong joint. The bolts should be a loosefit in the holes - they are there to clamp the two sections together - boltsshould not to locate them. As all this is made of MDF it will all move togetherif there is a change in humidity or temperature.

Chris Frost

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Routing Slots In Mdf Wood

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