Santa Fe FT #100 was delivered in January 1941. The EMC FT demonstrator #103 dates to 1939.
I don’t think so, the picture I’ve seen of a W-1 electric emerging from the tunnel shows the pantograph close to lock down position.
A battery+electric locomotive could make electrfication a much more viable proposition as the wire could be dead in low clearance zones, which would eliminate the need to raise clearances in those areas. The 1991-92 SCRRA hearings on RR electrification in the LA basin suggested that half of the cost of electrification was from increasing clearances such as highway overpasses.
OTOH, building a few battery demonstrator locomotives would be cheaper than all but the smallest electrification projects.
Many freight cars in the UK only have single-pipe air brakes (some have twin-pipe), but passenger cars always have twin-pipe air brakes.
Older UK diesel locomotives don’t have dynamic braking (it’s normally called ‘rheostatic braking’ here), but the more recent GE-built ‘Class 70’ and Vossloh/Stadler built ‘Class 68’ locomotives do have it fitted.
Regenerative or rheostatic braking is very common on electric locomotives all over Europe (UK included) and has been for many years.
Modern electric MU passenger trains commonly have electronically controlled, fully ‘blended’ electric and friction braking, controlled from a single power/brake handle i.e. ‘coast’ in the centre position, move one direction for power, the other for braking.
The original BART cars from ca 1970 had blended regenerative/dynamic braking and friction braking. The regenartive/dynamics alludes to the braking controller pushing out current at 1kV (BART third rail voltage) with onboard resistors being cut in when the bus voltage went aove ~1100V due to nothing around to absorb power.
Been reading early editions of Railway Electrical Engineer and noted that work on regenerative braking started in the 1890’s.
Some years ago I was travelling on the underground tracks in Sydney, Australia on a 1980s “Tangara” train, which was noted for its modern styling. For example the upper deck windows curved into the roof much like Superliner lounge cars, not a feature expected on commuter trains.
I was riding just behind the cab and the window in the door was not covered by a blind as is usually the case. While I couldn’t see the driver, I had a view of the control panel, and in the tunnels I could see the ammeter, which consisted of illuminated LED segments in a circle, giving a display similar to a conventional analog gauge. The segments lit up green for power and red for regeneration. THis was a train with DC motors and Thyristor control.
As we approached a station, power would be cut off and regenerative brakes applied. The regeneration was maintained most of the way down the platform, with the disc brakes applied at a rekatively slow speed. The change was best seen on the ammeter sibnce there was no obvious jerk as the brakes changed from one mode to another.
Peter
Needless to say, the original BART cars were thyristor control with DC series motors - somewhere in my collection of papers there is a couple of handouts with the schematics of the propulsion electronics and a brochure on the Westinghouse traction motors. This was at a power systems seminar at UCB back when I was an undergrad in Cal’s EECS department.
If my memory isn’t too far gone, the motors were rated at 150 to 160 hp at 550 volts, and two motors were permannetly connected in series. What impressed me was that the thyristor control was sophisticated enough to operate the motors as series generators. Acceleration was 3mph/sec up to 30mph and the cars were initailly rated for an 80mph top speed which was cut back to 70mph to lessen wear and tear on the motors. In the early days of BART operations, the trains would get up to 80MPH for a few seconds when running the 1.1 miles between the Berkeley Ashby station and main Berkeley station - running time would be 1’35".
A couple of memories, the ~310Hz hum from the smoothing reactors coupled with whirring of the motor-alternator providng the AC power for the A/C and lights.
If I were to design a clean sheet propulsion system for BART (keeping the 1kV third rail potential), the system would use 1700V SiC FET modules for inverter per motor. The FET’s would allow for a high enough switching frequency to allow for small and relatively inexpensive filter.This would allow the use of ordinary wire for winding the motors.
I keep reading of this and to some point it is true and makes sense. However, in this day and age I think that many are putting too much emphasis on this heat thing when using the independent brake.
If things were as bad as many tend to report, how then did light engine movements get over the road without losing its tires? Think of all of those pusher engines backing down lite from Blue Ridge to Boaz! Reverse moves were restricted to 25 mph, so, the engine brakes will need to be used for a good distance (BTW, I have sound recordings of pushers going well over 25 mph downhill). Those tender brakes aren’t going to control the speed all by themselves. Pushers returning from Lofton to Roanoke on the Shenandoah line dealt with even steeper grades than the puny Blue Ridge. And, they had the advantage of being able to turn around on wye tracks in order to return engine first. Throwing a tire was not a problem. As I was told, those brake shoes were made to absorb the heat.
[quote user=“BigJim”]
Overmod
One of the principal reasons blended air and independent braking was restricted on large steam locomotives is that any significant amount of driver braking to slow the mass of the locomotive can result in the tires expanding enough to work off the center. Various kinds of clips, Gibson rings, etc. were used in an attempt to preclude the issue.The problem was that the light Amfleet equipment couldn’t supply “its share” of braking effort to help decelerate the 250±ton locomotive, which threw a somewhat disproportionate share of the high-speed braking on the (non-Decelostat-equipped) G’s driver brakes.
I keep reading of this and to some point it is true and makes sense. However, in this day and age I think that many are putting too much emphasis on this heat thing when using the independent brake.
If things were as bad as many tend to report, how then did light engine movements get over the road without losing its tires? Think of all of those pusher engines backing down lite from Blue Ridge to Boaz! Reverse moves were restricted to 25 mph, so, the engine brakes will need to be used for a good distance (BTW, I have sound recordings of pushers going well over 25 mph downhill). Those tender brakes aren’t going to control the speed all by themselves. Pushers returning from Lofton to Roanoke on the Shenandoah line dealt with even steeper grades than the puny Blue Ridge. And, they had the advantage of being able to turn around on wye tracks in order to return engine first. Throwing a tire was not a problem. As I was told, those brake shoes were mad
Balt,
All true.
The point that I was trying to make was that “a significant amount” is normal for light engine moves as that is the only way that they have to control speed downhill. A “significant amount” is not “abuse”. Abuse that would indeed lead to damage.
The problem is that those who don’t know read this and believe that the least little bit of heat is going to throw a tire. Worse, they repeat it until it becomes a myth.
When I said ‘significant amount’ what I actually meant was “enough braking effort to heat the tires severely” and this actually involves two things: the severity of the braking effort and the time it is applied. Where the problem develops is certainly not in sustained light-engine braking, even up to what looks like considerable speed; it is when you put the energy of braking into the tire enough to get it to expand ‘dangerously’ relative to the cooler center, but not enough energy to start warming the wheelrim. (In other words, beginning to approximate what the gas ring does when changing tires intentionally.) Service braking on light engines going down sustained grades is not likely to produce the effect, certainly not when supervised by intelligent N&W engine crews (this is a redundant phrase).
There is a bit of overlap between care to keep the tires tight and care to retain tread profile and extend tire life. ATSF 3751, for example, sometimes was moved with a set of spine flatcars in tow; this provided a relatively large number of braked wheels and shoes at comparatively low tare weight, so the independent could be sparingly used even if the engine had to be operated relatively fast to keep traffic on the line it was operating over fluid. I was more of the opinion that the practice was to preserve the tire diameter and profile and eliminate the potential for driver flatting (as notoriously produced on UP 844 during the early Dickens years) through reduced reliance on independent-brake actuation.
Big Jim is correct in that I was largely discussing the ability of the locomotive to brake its own weight, whether or not