Iam wanting to host some races on my AFX track, but dont want to spend the money just yet. I have a 4-Lane banked oval. Use crash and burn style of racing. Iam wanting to use 4 Power Terminals with each lane with its own Wall Wart. And use the stock controllers. Is the doable to host a race? Ill mainly race T-Jets and Magnatraction cars. But occasionally run Mag cars (Wizzard, BSRT, etc.)

Or i found these power supplys at Radioshack:
1. 13.5V, 3amp
2. 13.5V, 15amp
3. 13.5V, 25amp

Would option #1 be better? Could it run 4 Mag cars also?

What is your opinoins? I dont wanna spend a load of cash yet. Iam saving for college this fall and also the bill i have with my dad for building my Street/Strip Firebird.

Thanks
Blake

we run four power terminal tracks and four wall warts on our fourlane.so yeah its possible.i think the only problemwould be you might have to disable on lane on each terminal track...not sure if thats what my buddy did or not,but if 1 contoller ends up running two lanes,then you gotta problem!

Right now i have 4-Lanes with 2 Power Terminals. And i believe on the Power Terminals there are 2 spots to hook up the controllers. One for each lane, so that wont be a problem. Know ive been thinking how iam gonna have the inside lanes controllers ran? I may have to wire them underneath the track?

You need two more terminal tracks. I would disable the connections to one lane on each so there's no risk of an electrical screw up. Stagger each terminal track to spread out the drivers.. Just make sure you end up with two inside lanes and two outside lanes..

mag cars require more amperage i believe as the motors work harder to fight the magnetic drag created.i don't think 13.5 will give you the speed you want,but it depends on what you want.

Forund this last nite...go down a bit, it'll show a graph on which cars' amp. requierment.


http://www.hoslotcarracing.com/index.html

That table is a bit misleading because the current is dependent on both the properties of the car and the properties of the power supply. The maximum current a car can draw is approximately:

max current = max applied voltage / min winding resistance

This ignores the resistance in the entire circuit, including the controller, contact resistance at the controller hookup interface, bulk wiring resistance from the drivers station to the rails, bulk resistance of the rails themselves, contact resistance at the rail/shoe interface, contact resistance in the car's electrical system, bulk resistance of the brushes, and contact resistance at the commutator/wiring tab interface (solder tabs or crimp tabs).

This all assumes the power supply is capable of maintaining the max voltage under all current demands. Unregulated wall warts do not.

Most stock magnet cars have arms in the 6.0 ohm range. If you have an 18 VDC regulated power supply the max current draw would be 18/6 which is 3 amps. But if you hook up an ammeter to the circuit you will read more like 0.3 to 0.5 amps, a fraction of what you calculated. Where did the extra current go?

The current didn't go anywhere. As soon as the motor starts turning it is no longer just a motor, it's also a generator (or dynamo to you old timers). As a generator it puts out a voltage that opposes the voltage coming from your controller. So the earlier formula becomes:

max current = (applied voltage - generated voltage) / winding resistance

Ideally, with a fixed load on the motor the current would drop to near zero when the motor is spinning. The only current in the circuit is what is needed to generate torque to handle the load and overcome electrical and mechanical losses in the motor. It becomes a self speed-regulated system. If greater voltage is applied to the motor, the motor speeds up so that it generates more voltage, but the current will stay about the same as long as the amount of torque required to handle the load does not change. If the increased speed puts a greater load on the motor the current will rise accordingly, but the speed of the motor will always be predominantly determined by the applied voltage. That's a very key point...

So what happened when you slapped some super sucker fluxmaster 2000 traction magnets in your box stock Tyco and suddenly it's pulling 2 amps from your power supply at the same speed? Well, the applied voltage is still the same, and the motor speed is still the same because it's tracking the applied voltage, so something had to happen to allow you to pull those those rail benders down the track on the belly of your Tyco. That something is torque, and to generate lots of torque you need to provide lots of current. That's why those heavy magnet cars need more current.

A little sidenote: you now know that the rotational speed of the motor is a function of the applied voltage because the motor must speed up or slow down to generate its own voltage (known as Counter EMF in technical books) to offset the applied voltage. But what determines the actual speed that the motor runs at for a given voltage? Well, the predominant factor here is the number of windings on the armature poles. The more windings, the more generated voltage for a given speed. So a given motor with a lot of windings will not have to spin as fast as the same motor with fewer windings. The inverse is also true, and more applicable to what we care about as racers, the fewer windings the faster the motor must spin to generate the voltage needed to offset the applied voltage. This is why removing windings from a stock motor, dewinding, will cause the motor to run faster at a given voltage. The reduction in resistance is not the important factor, it's the reduction in the number of windings that makes the real difference. With fewer windings the motor must spin faster at any given voltage to generate the required counter EMF. The reduction in resistance is, however, a pretty good indication that the motor has been dewound. Plus, dewinding has its dangers because there is a physical trade off between the number of windings and the size of the wire used. Motors that are designed to carry a lot of windings will usually have a thinner wire with less current carrying capacity. Removing too many windings may speed up the motor but exceed the current rating of the windings. Welcome to Poofville. Generally speaking, as you reduce the number of windings you'll need to increase the size of the wire used for the windings.

All this talk of torque and current makes a key assumption. The assumption is that the power supply can actually deliver all of the current that the car needs. If the car asks for more current but the power supply can't deliver: too bad car, it won't get more than the power supply can put out. So what happens when you have more than one car asking for more current than what the power supply car deliver? Well, they both get less than they asked for, with the car asking for more getting a bit more than the other one. But neither is totally happy. What's worse, if both cars are asking for more than the power supply can deliver, and suddenly one of the cars goes away, well... the power supply will give all of what it has to give to the one remaining car. This causes a sudden surge in the remaining car, followed by an unscheduled and impromptu wall integrity test. Thwack! Welcome to Surgeville.

So how do you know how much current a power supply can deliver? It's all in the specs, but how those specs are presented can be different. Sometimes the maximum power supply voltage and current will be stated explicitly, like is done with those Radio Shack battery replacers. Other times, especially with wall wart type power supplies, you will be given the maximum voltage and the maximum power. Power, not current. No big deal, you just have to do a little math. The power is simply the product of the voltage times the current, so to get the maximum current that the power supply can put out you simply divide the power by the voltage. Case in point, the standard Tomy wall wart: voltage = 22 VDC, power = 7 VA. Doing the math tells you that at full rated voltage the maximum the wart can put out is around 0.3 amps. So.... if you go back to the first formula and note that your Tyco is asking for 3.0 amps for that fraction of a second that the car is starting up from a dead stop, what is the max current draw that you will see when running with a Tomy wall wart? Easy answer, around 0.3 amps because that's all the wart can put out. In reality, because the Tomy wall warts are unregulated you will see a bit more current, however, the price you pay for getting a little more current is a drop in the voltage! The thing that cannot change is the power rating. That "7 VA" number is hard and fast. If you buy a power supply and the max voltage and max current are not explicitly stated, take a look at the VA rating and that will tell you what's really going on.

The maximum current a car can draw is approximately:

max current = max applied voltage / min winding resistance

This ignores the resistance in the entire circuit, including the controller, contact resistance at the controller hookup interface, bulk wiring resistance from the drivers station to the rails, bulk resistance of the rails themselves, contact resistance at the rail/shoe interface, contact resistance in the car's electrical system, bulk resistance of the brushes, and contact resistance at the commutator/wiring tab interface (solder tabs or crimp tabs).

Just an FYI. I measured the resistance of a car by placing the probes on the rails. This would take into account the resistance of the windings, the brushes, pickups, etc. On a "stock" car (~6 ohm arm), I measured around 10 ohms, which would result in a max current of 1.8 amps at 18 volts (ignoring the resistance of the wiring and controller). So if you have a Tyco drawing 2 amps on 18 volts, you have either a hot arm or silver electrics, both of which will increase the current demand of a car.

Also, as a bit of a simplification of the above AFXToo's very complete description, you can just assume that a dc motor will draw max current at zero speed, and minimum current at max speed. So, your wost case current demand will be when you turn on power. A car that draws 2 amps at startup will likely draw no more than 0.5 amps average during a race.