Dynamic braking is caused by the current flowing in the windings of the motor's armature when the motor is short-circuited while the car is coasting and the motor is functioning as a generator. The current induces a magnetic field around the armature windings that interacts with the field of the permanent magnets to develop a torque that makes the armature want to spin in a direction opposite to the direction it is being rotated by the gear train of the coasting car.
Some PM controllers - not all - contain a small fixed resistor in the braking circuit that reduces the amount of current that flows in the armature windings under braking. The lower current reduces the braking effect slightly, making the car smoother to control. You can determine whether your controller contains a resistor in the braking circuit by checking its number against PM's
chart.
This resistor is not sufficient to eliminate the braking effect, but there are a number of factors that effect the strength of the braking effect and whether or not you notice it. Rather than make a long post, these factors are explained in this
Dynamic Braking Tutorial. The tutorial explains braking very simply but I will be adding some sections that talk about developed torque and go more deeply into motor characteristics that effect braking soon.
James, it would have been good if you could have tested the brakes on the lane you were using at the club track while you were there - by borrowing somebody's car and controller or trying a different lane.
There are a couple of ways to test your controllers to see if the braking circuit is working. The easiest way, if you have an ohmmeter is to simply hook the leads of the meter up to the track common (ring) and brake (tip) conductors on the Scaley sport controller connector while the controller's trigger is not being depressed. If the controller does not have a fixed resistor you should get zero or very small resistance across these two conductors. My PM 2044 reads about 40 ohms. The reading on my controller is the same regardless of whether I connect the meter's red lead to tip or sleeve.
As long as the meter reading is zero or small your brakes are working - the reason you are not noticing them is either the car, the configuration of the layout, or the layout's wiring. If the meter reads open, then your controller definitely has a problem in its braking circuit.
A second - and more toilsome - way to test the controllers is to test them against each other. Scaley sport uses a connector that connects both the power, track comon and brake wires from the controller so you can't just disconnect the brake wire to turn brakes off and then reconnect it to turn brakes on without building a driver's station that allows individual connection of the three controller wires. Fergy has put a schematic for a simple driver's station that you can wire together in an hour or so
here.. It includes a switch to turn brakes on and off, the easiest way to tell if brakes are working and how well a given car's brakes work.
If you don't feel like building a driver's station to allow disconnecting the brakes, you can build a long straight - just take a powerbase and enough straight track pieces to build a straight that is at least 10 feet long, prefereably longer if you can. Your cars will run on this straight even though it does not form a closed course.
Then take several cars and test how well they stop with either controller on the same lane. The braking effect can very greatly between cars. If you have a car that you know has good brakes that would be the best one to test with. If you don't know which cars have good brakes test a bunch. The braking effect is easier to notice with non-magnet cars, since they don't have the drag of the traction magnet adding to braking. Some cars - like the Momogram Corvette GS and Carerra cars - are known for poor brakes.
If there is a noticeable difference in how quickly the cars stop on the long straight between controllers then you have a reason to suspect a controller has a problem with brakes.
Sorry for the long post, hope this helps.
Paul
Circuit TrustChrist