BDTS vs DTBS (class 304 question)

[F2Andy]

According to Wiki, the class 304 EMU pre-1980 formation was BDTS+MBS+TC+DTBS. What is the difference between BDTS and DTBS? I understand the letters to mean brake-driving-trailer-second, but I guess in one of them one letter means something else, and I should be able to tell from the order?

[Dagworth]

Battery Driving Trailer Second - Motor Brake Second - Trailer Composite - Driving Trailer Brake Second

 

Andi

[F2Andy]

Thanks, I had not realised they had batteries. I guess they could not run on them for long - or more likely not at all? Were the batteries just for lighting/heating if the power went?

 

Would the batteries be under the floor? Looks like the BDTS has some boxes down there that are not under the DTBS.

[Dagworth]

The batteries are for the control circuits, lights etc. when the unit is not connected to 25kv (either pan down or in a neutral section). They also need to be able to run the compressors sufficient to raise enough air to lift the pan. The batteries cannot actually move the unit, it needs 25kv for that.

 

And yes, the batteries would be under the floor. 

 

Are you building a 304? I have a pair under construction myself for Ravensclyffe.

 

Andi

Edited January 31, 2021 by Dagworth
Extra comments

[F2Andy]

I am indeed building one - I will probably start a thread on it at some point. It is in N gauge, 3d printed cabs, on suburban coaches. Not the sort of thing I have done before, so we will see how it goes.