Reduced power is just the same thing as running a "choke" on your controller - except you reduce it rather more. Its simply a resistor in the power line to each lane which absorbs power and slows the car down. The resistors do produce heat (the "absorbed" electrical  power  is turned into heat.

The diagram above shows how to wire it into a track. One resistor per lane is connected at some convenient point between the battery + terminal and the controller full power band. 

 If you wire it into the track, and assuming you don't want reduced power all the time (which is possible on an exhibition track), you need some way of restoring full power. The wiring shown in brown on the diagram provides full power, an on/off switch (one pole per lane) to short out each resistor will provide full power in the on position, and reduced power in the off position. For reasons that are explained elsewhere on this site the brown wiring needs to be as short as possible, and as thick as the main track wiring.

The fuses are for short circuit protection. The full power fuse is described in the track wiring article. The fuse for low power is there to prevent damage to the resistor. If a driver keeps their controller hard down when there is a dead short, all the track power will be warming up the resistor (With a 1 ohm resistor that's 13 to 14 amps on a normal track power supply). Now that is not enough to blow the full power fuse (they should be rated at 15 amps), but it is enough to make the resistor very hot (around 150 watts). To avoid having an unnecessarily big an expensive resistor, and also to reduce the risk of  damage to incorrectly wired controllers, a fuse for low power should  be fitted - 5 amp fuse wire works fine in conjunction with a 1 ohm resistor.

As an alternative to wiring  reduced power into the track, you could do it as a plug in box. The wiring is shown in the diagram above. There is no need for any switches - just unplug it if you want full power. This is also a wiring diagram for a choke box - although resistors in the 0.05 to 0.15 ohm range would be appropriate to a choke.

An example of a club that uses this reduced power formula for some of its club racing is  Bournemouth.  They use 1 ohm 50 watt alloy cased resistors.  (These aren't available from Maplin any more, four 3.9 ohm 10watt resistors in parallel will do the same job, and that'll cost under £2 a lane)  Two pole on/off switches are used - so each switch does 2 lanes (16A DTST rocker switches - about £1.50 from car accessory shops or Maplin).  You need to duck under the track to switch from full to reduced power - but that's not a problem - racing is on the same power all evening.  There's no need to worry about lack of power when its in full power mode - as was demonstrated at our recent BOC nobody will realise you've got a low power option when they are running on full power.  Ipswich and Netley are other clubs with a built in low power option.

Why  1 ohm?  That's what suited the cars we were using  best.  It was easy to try different resistances - an old Parma controller was connected into the power line, this was set on part power with sticky tape, then the car was driven with a normal controller. The old controller was taped in several positions till we found what we wanted - when we measured it - it was about 1 ohm.  The right resistance for other types of car depends on how quick the motor was in the first place, and how much you want to slow it down - just repeat the test described above to find the right value for you.

A higher resistance  would probably be appropriate for public/ exhibition use. Lower  To give some idea, if 1 ohm track resistance is suitable for slowing down the sort of cars you run on a 4 ohm controller, then about  4 ohms should be suitable for slowing down the sort of cars you run on a 15 ohm controller.

Yes this is certainly an option, and  it can produce much the same effect.  Which is better depends on what's available and what you want to achieve - here are some things to think about.

 If slower motors are available and cheaper then the slower motors have obvious advantages. If you cannot get a reliable motor of the appropriate power then reducing the track power has the obvious advantage.  If you want to make use of a large stock of existing motors that are a bit too powerful, then reducing the track power is attractive. The table shows the main differences between the two approaches. 

 Generally motors designed to produce low power are no more reliable than high powered ones, where as motors running on reduced power will be much more reliable. This is particularly a problem with some motors intended for home set type applications where they will not be working hard much of the time .... put them in a better chassis on a club track where they are being called on to produce their maximum power most of the time and reliability can be poor.  

C can style motors that are designed to handle more power can be expected to be very reliable when using an extra mild wind. C can motors are not generally available with anything thinner than 30g winds which many people would say is far too powerful for novice drivers with 1/32 production - and is certainly a lot quicker than the "low power" we are considering here.

Links to other Track building articles

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