Afternoon all!

I was very surprised this morning when, waiting for my train on the S4 line, it was not the usual double unit of class 423 EMUs which came in, but a pair of 420s, which haven't been on my line since summer - working only a couple of turns in the late evening and on Sunday mornings before their withdrawal. These were worked out of Darmstadt, which is usually served by the S3 line and which in turn was in the hands of 420s till June - the S3 and S4 lines having merged traction diagrams during the times I mentioned. However, I can only speculate why a pair of 420s was put on the S4 line – though failure of at least three 423s seems most likely, as the turn behind mine was worked with a single 423.

So, after my course I then headed down to Langen, which I felt was the best vantage point for taking a couple of photos under the weather and lighting conditions we have today .

Okay, I did keep you in suspense and did not mention yet I was particularly lucky in that the 420 on the northern end was indeed 420 425, one of the 7th batch sets transferred over from Stuttgart last year B) . So, here he is - 420 425 with 420 261 behind standing by to work the 6442 service up to Kronberg.

I then made it onto the train in time for my way home and took a couple of detail shots when I got there...

This would be a detail shot of the outer bogie under the cab of the "A" end car. As you can pick out from the inscriptions, it had its last revision completed on 16 July this year – as I mentioned before in another blog entry, it took a while to put these sets into service after they had been transferred over from Stuttgart. There also is a works plaque from Siemens who provided the electrical equipment for this set, while the grey plaque to the right of the inscriptions is an AEI tag. Note how there are cheek brake disks on the outside of all wheels when you compare this photo to the next one...

...while this here's the outer bogie on the "B" car of 420 261 – "B" cars on German EMUs being given consecutive numbers which have 500 added to the actual consecutive number of the set in question. 420 261 is the first 4th batch set, with all batches except the 7th and 8th having double-sided brake disks on only one wheel per wheelset. Note the vertical shock absorber serving to support the air suspension cushion, which in turn you can see between the bogie frame and the body, as well as the PZB train protection transceiver below the bogie frame.

Meanwhile, the intermediate cars on the class 420 sets are actually registered as a class themselves - 421, as you can see here. Of course, they cannot be operated independently of the end cars, which contain the cabs and quite a lot of the electrical equipment. In fact, the 420s have two independent traction packages – spreading across either two end cars and half of the intermediate cars. All wheelsets are powered. When they were introduced – the prototypes having appeared from 1969 onwards, with production beginning one year later and continuing right until 1997 – , they were highly advanced, having notchless, thyristor-based power controls, allowing for amazingly smooth operation. Likewise, air suspension had been anything but the rule on commuter stock of the time.

The prototypes and first six batches were fitted with pneumatic double sliding pocket doors, while the 7th and 8th batches received pneumatic double plug doors – which are about the easiest distinguishing feature from the outside.

While the first six batches were fitted with two pantographs initially, the 7th and 8th made do with only one – the earlier sets eventually having the second pan removed during revisions in most cases in later years. Next to the pan, which is a SBS 65 type, you can see the voltage sensing device – which is the big cylindrical item above the right door blade – with one of the two circuit breakers and associated cut-off switch being located next to it. The cable running to the right belongs to the busbar connecting the adjoining end car to the high tension circuit. The transformers are located in the end cars.

The other circuit breaker for the second traction package is located on the other side of the intermediate car.

There is a fixed close coupler bar between the cars, with dampening buffers on the outside.

The 7th and 8th batch 420s were refitted with LED-based destination displays in place of the rollsigns on the previous batches. Also, they have a "Railvox" passenger information system installed, which provides automated station announcements. However, the two Railvox devices per unit are not connected to each other, meaning the destination displays still need to be set manually on either end of the train.

Another major difference between the first six and the last two batches of this class – aside from the doors, pneumatic brake layout and passenger information system – is that the brake also comprises spring-loaded parking brakes, which may not be used in mixed formations with a 7th or 8th batch 420 and one from the earlier batches, as they cannot be released remotely from the older 420s.

And these are the two 420s facing each other. I think it's safe to say this class is among the most recognizable types of motive power which Deutsche Bundesbahn had built – the large, wrap-around windscreens, slightly pointed frontsides and uniquely shaped headlights providing a good amount of character which many more recent classes do lack.

And an overview of the technical specifications for this class...

Overall length per unit: 67,500 mm/221 ft

Overall width: 3,080 mm/10.1 ft

Service weight: 138 tonnes for first two batches, 129 for all others - the 1st and 2nd batch having had their end cars made of steel rather than aluminium.

Power output: 2,400 kW/3,264 hp

Top speed: 120 kph/75 mph

Passenger capacity: 194 seated (average), 400 (with standing passengers)

Total number built: 480

And here is a WAV file with a recording of the set's onboard sound – including a satisfying door slam . I picked a section of the ride where there were no conversations by other passengers as I do want to respect the privacy of others: Click.

Edit - fixed WAV link.