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Whats up with the new renovated bart trains?why do all the new or renovated trains make this weird humming noise now? like when it accelerates and decelerates it sounds like electricity or something making weird humming noise? it sucks and its so annoying! i wonder how t/o's can go on hearing it all day! |
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I believe that sound is only
I believe that sound is only heard on C-type cars. The majority of the renovated cars are C-type cars, meaning that they are capable of being both the lead car but can be within the train as well. Because they can lead the train, I believe that the sound is of the motors that are active regardless of whether it is a lead car or not.
All BART cars have a sound
All BART cars have a sound that comes from the propulsion system. The type of sound depends on the car type. All cars have an active propulsion system regardless of location in the train; the lead car is not a locomotive that pulls unpowered cars.
C-cars have a DC propulsion system which uses power electronics called a chopper to control the motor current. The single frequency hum at 218 Hz comes mostly from the motor smoothing reactor which is just a large coil wound on a laminated steel core.
C-cars are numbered 301-450 for C1 and 2501-2580 for C2. Although interiors are being refurbished on some C-cars, the undercar equipment is not being replaced.
The rehabbed A/B fleet uses an AC propulsion system. The traction motors are three phase AC induction motors that are controlled by a variable voltage, variable frequency electronic inverter. The hum is a variable frequency that comes from the traction motors and depends on the speed of the car.
Rehabbed A/B cars, called A2/B2, are numbered 1501-1776, 18XX, 19XX for B2 cars and 11XX-12XX for A2 cars. The reason for XX as the last two digits in some of the numbering series is that those series are not complete. Cars in the 18XX/19XX series were formerly A cars that have been converted to B2 cars leaving holes in the 11XX/12XX A2 series. There are also some numbers missing from the 1501-1776 series for cars lost by accident or fire.
As far as the propulsion system noise is concerned, this is not unique to BART. Virtually all electric rail cars with power electronic control systems, AC inverter or DC chopper, will make these noises. To attempt to muffle the noise to an inaudible level within the cars would add considerable weight and expense to the vehicles.
Question for you: exactly
Question for you: exactly how many of the original A-cars were converted to B2s? And do the first batch of B2s (i.e. 1501-1776) follow the original number assigned to it as a B-car?
If my memory isn't shot (I've
If my memory isn't shot (I've been gone from BART for over two years), there are 53 A2 cars.
There would have been 175 original A cars but two were destroyed during testing in a manual operation head on collison at Coliseum before the system even opened in the early '70s and one A car was lost in the transbay tube fire in '79. So 119 A cars were ultimately converted to B or B2 cars.
The 1800 series cars began the conversion process from A to B in the early '80s and became 800 series cars at that time. No effort was made to reflect the original A car number in the 800 series; numbers were assigned sequentially as the process was completed. The conversion program was conducted at the Hayward Shop. Close to 40 were done in the years prior to the A/B rehab program which began in 1998. The rest of the 1800 and 1900 cars were converted during the rehab program.
Cars that remained as A2 cars had new cabs installed. The ATC (automatic train control equipment) was retained rather than being replaced with new since it had been replaced with a newer generation in the 80's. The ATC from the converted cars was installed in the C2 cars which were originally delivered without ATC in anticipation of the conversion of A cars to B2s freeing up the needed ATC equipment.
The 1501-1776 just had a 1 added to the original number.
I know it gets complicated for those who just see BART cars as all being the same.
Thank you thank you! More
Thank you thank you! More mysteries have been answered =)
Those A2s and their new cabs...would they also be the only ones with the semi-high pitched alert tone followed by the prerecorded voice telling you that the doors are closing?
Yes, that's the door alert
Yes, that's the door alert you get when an A2 is the lead car.
yeah, I know the sound you
yeah, I know the sound you are referring to. I was on a newly renovated car out of PBP this morning and while it was accelerating from Walnut Creek, I noticed it made a very loud humming noise all the way to Lafayette.
ive noticed the trains with
ive noticed the trains with carpet make the same noise also but u cant hear it as much. possibly the carpet muffles the sound compared to the new floors?
It sounds reasonable that the
It sounds reasonable that the cars with the new floor covering have a louder sound. It's the C-cars that are having the carpet replaced with the non-carpet floor covering and it seems to be those cars that are being reported with the higher noise level.