TRACK CONSTRUCTION Part

• Slot Car Track Wiring
• Slot Car Track Wiring Machine Machine Repair
• Basic Slot Car Track Wiring
• Slot Car Track Wiring Machine Machine For Sale
• Slot Car Track Wiring Machine Machine Troubleshooting
• Slot Car Track Wiring Machine Machine Gun

Slot Car Track Wiring

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Pageupdated January 2009, minor additions March 2012, January 2015, resistancetable updated September 2015 and January 2018

Part 5 of this series of articles says what shouldbe connected to where - and gives a simple guide to how to wire it. This pagegives the reasons for the recommended wiring and explains how differentthicknesses of wire and ways of connecting it make a difference.

Thereis a separate article explaining how to find andrepair track wiring faults.

TheResistance of Copper Wire

What do you wire a slot track with? - well OK withwire obviously but what type. The important factor is the cross sectional areaof copper, which dictates the resistance. (The current ratings given in wiretables are not relevant) Yes it does need insulation, but any insulated wire will do (it onlyneeds to withstand about 14 volts). There are special cables available (atconsiderable expense) which are intended for Hi-Fi loudspeakers - these may dosomething for the nuances of musical reproduction, and will certainly dosomething for your HI-Fi retailers profits. Yes there are small changes inresistance depending on the wire (the resistance of copper does change a littlewith impurities; fully annealed copper has nearly 4% less resistance than fullyhard). High quality speaker cable can be well over double the the cost of anequivalent thickness mains cable, but its resistance is only very slightly lower- if you are going to spend twice as much, spend it on twice as much mains cableand halve the resistance - what really counts is how much copper you getfor your money! Normally the cheapest suitable wireavailable is mains cable. Each core is usually a single strand of copper, so itssuitable for fixed wiring (for your controller you need flex - where each careis made of many strands of thin wire).

This advice is correct for the prices of cable inthe UK, I don't know what prices are charged for cable in other countries.However, wiring up mains power in buildings is bound to be a much larger marketfor cable than more specialist uses in any part of the world, so I assume thatcable for wiring building would be the cheapest source of cable with reasonablylarge cross sectional area in most if not all countries.

Shorter wiring has less resistance - half the length hashalf the resistance. Double the cross sectional area has half the resistance -so paralleling up two core of a cable will half the resistance. The table aboveshows the approximate resistance of various conductors used in track andcontroller wiring. (The resistance of nominally similar copper wire does varydue to various factors, but this is a detail that is unimportant to trackwiring.)

(If you want an equation, ohms law tells us the voltage drop = resistance x current and resistances add up as shown below)

What does this mean on a realtrack?

The best way to answer this is to work out the figures fora typical track. The example I’ve used is a 30m / 100 ft. lap length track -the exact figures will vary with different lap lengths, but the principles arealways the same. The resistance varies round the lap length. The graphs show howthe resistance between the car and the track power supply vary as you driveround the track. A greater the length of track between the car and the powerfeeds, gives more the resistance and hence the less power. As the graphs show,the highest resistance is mid way between the power feeds, but the resistancechanges very little for some way either side of the halfway point . The reasonfor this is that as the car goes round the track the resistance from theprevious feed isgoing down -these two just about cancel out round about the half way point.

There is also some resistance in thewiring between the battery, the controller sockets, and the point where power isfeed to the track. This is why the graphs don't drop to zero resistance at thepower feed point. (The graphs assume 0.05 ohms between the power supply and thetape / braid where the power is feed in. Again this is typical of a good clubtrack)

The Graph 1 shows a comparisonbetween tape and braid. It clearly shows that the resistance of braid is muchlower than tape. In this example a 10 amp. load half way round the lap would seeabout 1.5 volts less than the battery voltage on the braid track. The same 10amp. load would see about 4.6 volts less than the battery voltage on the tapetrack.

Given a reasonable battery, thebraid track op to about 30m / 100 ft lap length shouldmeet BSCRA recommended power levels with the power feed in at one point.

The tape track certainly does notmeet BSCRA recommended power levels with the power feed in at only one point -indeed it doesn’t even meet the BSCRA minimum level. A Group 12 powered carwould be noticeable down on power, a hotter motor even more so. However, a 1amp. load would only cause a drop of 0.46 volts, so extra feeds make much less differenceto low powered cars such as Falcons (and the extra feeds make even less differenceto Scalextric,Ninco etc. cars) .

The answer to this lack of poweron a tape track is to add extra power feeds. The resistance for tracks ofdifferent lap lengths will be in proportion to their lap lengths - for exampledouble the lap length, double the resistance; half the lap length, half theresistance. The graph for a single feed will always be the same shape with thehighest resistance half way round the lap length.

Graph 2 shows the improvementthat can be achieve with an extra feed or 2 on the tape track. (I’ve assumedthe extra feeds are 3 metres of 2.5sq.mm cable fed from the main power feed. Ona real track extra feeds would probably be all different lengths, but thisexample gives a reasonable idea of what's going on in most tracks). The exampleshows that a couple of extra feeds will reduce the highest resistance to alittle over 0.2 ohms - a voltage drop into a 10amp load to a little over 2 volts- a big improvement on the 4.6 volts with only a single feed, but still not asgood as braid.

Graph 3 shows the improvementobtained on the taped track with 4 or 5 feeds (the main feed and 3 or 4 extrafeeds). I’ve shown braid on the same graph It can be seen to that tape with 5feeds gives broadly similar levels of power to braid with a single feed.

Feeding power to both ends of alength of tape reduces the resistance substantially. Graph 4 shows what happensto the resistance with a single tape break. the rise in resistance would be muchworse with one break on each side.

What does this mean to my cars?

OK, so how much does all this matter - is theeffect of all these tiny bits of resistance going to mess up your racing? Thereare tracks that most racers consider 'good power' and there are othertracks where the power attracts complaints. BSCRA rules do recommend powerlevels (10 amps at 12 volts) and set a minimum (4 amps at 12 volts). I’vemeasured the power on many tracks. The tracks with a reputation for 'goodpower' meet BSCRA recommendations (at least most of the way round). Thetracks people complain about are usually well short of BSCRA recommended levelsand some are below the minimum. BSCRA rules do not specify track resistance, butif you start with a battery or power supply at 13.8 volts ohms law tells us that to get at least10 amps at 12 volts the resistance must be under 0.18 ohms (and for the minimumpower level the resistance must be under 0.45 ohms. ) This 0.18 ohms includesthe resistance of the battery itself, so perhaps its advisable to aim for a bitless resistance in the track wiring.

Slot Car Track Wiring Machine Machine Repair

Using the above figures, with 'goodpower' a 26g strap motor accelerating from low speed will only see about10.2 volts -and a Group 12 accelerating from low speed will see about 12 volts.At the minimum level a 26g strap motor accelerating from low speed will only seeabout 7.2 volts -and a Group 12 accelerating from low speed will see about 10volts.

The same principles apply to plastic track, but the main problem with thistype of track is often continuity at the joints due to the connectionsdeteriorating. The rails of plastic track do have resistance (for exampleScalextric Classic track rails have a resistance of about 0.039ohms/meter) but this is less of a problem with the very much lower currentmotors that are usually used on this sort of track.

Basic Slot Car Track Wiring

Chris Frost

Slot Car Track Wiring Machine Machine For Sale

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Slot Car Track Wiring Machine Machine Gun

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