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Re: Incompetent FRA safety specialist on air brakes
Author: Dr Zarkoff
Date: 06-21-2014 - 01:28
>ABS antilock braking on an automobile that allows one to got right up to the limit of adhesion without wheels sliding.
WABCo's Decelostat system of the 1930s used a round inertial weight which was loosely connected to one end of an axle. Normally it would mirror the rotational rate of the axle. If the wheels on an axle slipped, it would continue to rotate at the higher rpm long enough to active a dump valve which released the pressure in the brake cylinders for that axle until it stopped sliding (or the rotational speed of the weight came down).
Budd's Rolokron used a small generator attached to the end of each axle. When the voltages from all the axles on a car got out of synch because some wheels were sliding, a set of differential relays would activate magnet valves to release the bake cylinders on the affected axles.
The modern version of decelostats uses inductive probes on one end of each axle which watch that set of gear teeth on the roller bearing cap. These produce tones which are monitored by solid state electronics. A tone which is significantly lower than the others indicates that the axle is slipping.
Needless to say none of these systems can be applied to a car with a body mounted brake cylinder and foundation brake rigging.
Although "ABS" really stands for "Acrylonitrile Butadiene Styrene" -that black plastic pipe you buy at Home Dumpster- automotive anti-lock brakes use similar electronic methods to detect differences in wheel rotational speeds.
The signals of both electro-pneumatic (1900) and ECP (1990) brakes travel at precisely the same speed: the speed of light. (There are too many G-D acronyms running around).
>Amfleets & Horizons seem to come on very hard and quickly;
26-C brake system.
>Superliners and Cal Cars have a little softer start on the braking.
Same 26-C brake system. The "softer start" is a result of the Superliners and CTDX bi-levels weighing more.
>With light rail, the old mostly-electromechanical Siemens cars stop Right Now in emergency, while the newer computerized cars seem to fade in and out a bit -
That's the slip-slide control at work.
>though the maximum braking rate on light rail is considerably higher than on standard rail probably due to the magnetic track brakes that help out.
Yes, it's the magnetic track brakes which make the difference. LRV ones are segmented so they follow the railhead better that the kind used on PCC streetcars (which aren't segmented).
WABCo's Decelostat system of the 1930s used a round inertial weight which was loosely connected to one end of an axle. Normally it would mirror the rotational rate of the axle. If the wheels on an axle slipped, it would continue to rotate at the higher rpm long enough to active a dump valve which released the pressure in the brake cylinders for that axle until it stopped sliding (or the rotational speed of the weight came down).
Budd's Rolokron used a small generator attached to the end of each axle. When the voltages from all the axles on a car got out of synch because some wheels were sliding, a set of differential relays would activate magnet valves to release the bake cylinders on the affected axles.
The modern version of decelostats uses inductive probes on one end of each axle which watch that set of gear teeth on the roller bearing cap. These produce tones which are monitored by solid state electronics. A tone which is significantly lower than the others indicates that the axle is slipping.
Needless to say none of these systems can be applied to a car with a body mounted brake cylinder and foundation brake rigging.
Although "ABS" really stands for "Acrylonitrile Butadiene Styrene" -that black plastic pipe you buy at Home Dumpster- automotive anti-lock brakes use similar electronic methods to detect differences in wheel rotational speeds.
The signals of both electro-pneumatic (1900) and ECP (1990) brakes travel at precisely the same speed: the speed of light. (There are too many G-D acronyms running around).
>Amfleets & Horizons seem to come on very hard and quickly;
26-C brake system.
>Superliners and Cal Cars have a little softer start on the braking.
Same 26-C brake system. The "softer start" is a result of the Superliners and CTDX bi-levels weighing more.
>With light rail, the old mostly-electromechanical Siemens cars stop Right Now in emergency, while the newer computerized cars seem to fade in and out a bit -
That's the slip-slide control at work.
>though the maximum braking rate on light rail is considerably higher than on standard rail probably due to the magnetic track brakes that help out.
Yes, it's the magnetic track brakes which make the difference. LRV ones are segmented so they follow the railhead better that the kind used on PCC streetcars (which aren't segmented).
