Early EMU Traction Motor Noise

[Bringback309s]

Just watching the old VECTIS units (the original standard stock) on the IOW brought back a memory from when I was a boy traveling on the GE. The VECTIS units, and something I used to travel on, would make a series of knocking / clunking noises under acceleration, I would guess some sort of gearing. I can't remember the 302's, 307's and so on making this noise as I travelled on those for many years, I only remember it because I would have been very young, and whatever it was used to upset me! What is that noise, and what units would have had these motors? I'm thinking 306's are likely, possibly 305s?

 

[dubscottie]

Just watching the old VECTIS units (the original standard stock) on the IOW brought back a memory from when I was a boy traveling on the GE. The VECTIS units, and something I used to travel on, would make a series of knocking / clunking noises under acceleration, I would guess some sort of gearing. I can't remember the 302's, 307's and so on making this noise as I travelled on those for many years, I only remember it because I would have been very young, and whatever it was used to upset me! What is that noise, and what units would have had these motors? I'm thinking 306's are likely, possibly 305s?

Is this the noise? (opening part)

 

[AM9]

Is this the noise? (opening part)

Very interesting video but that animation at the beginning shows an ac traction system. The 1938 tube stock on the IoW line is DC powered and would have a resistor chain that was progressively switched out by contactors to increase the current through the motors. The original voltage supplied to them was ISTR 630VDC. The clicks would be the sound of the contact breakers closing and the louder knocks/bangs would be them opening where faster action was needed to prevent a sustained arc.

 

[superjohn]

Camshaft control? Class 313 units had a very distinct sequence of clicks and perceptible jerks when accelerating which were caused by the camshaft switching through the power settings. Later PEP units had thyristor control with smoother acceleration and no clicks.

Regarding the video, although it is an AC overhead EMU I imagine everything involved with the traction electronics was transformed DC back in 1966.

 

[AM9]

Camshaft control? Class 313 units had a very distinct sequence of clicks and perceptible jerks when accelerating which were caused by the camshaft switching through the power settings. Later PEP units had thyristor control with smoother acceleration and no clicks.

Regarding the video, although it is an AC overhead EMU I imagine everything involved with the traction electronics was transformed DC back in 1966.

The OP is talking about the ex-LU standard tube stock (also known as the 1923 tube stock) that was fitted with conventional contactors. They also had series parallel changeover arrangements which produced a very loud 'clack' accompanied with a jerk forward.
The first Tube trains with camshaft control were the 1959/1962 tube stock, - even the following tube stock: the 1938 series, still had contactors, (examples of these are about to be replaced on the IoW line) with ex D78 trains.

 

[hexagon789]

Camshaft control? Class 313 units had a very distinct sequence of clicks and perceptible jerks when accelerating which were caused by the camshaft switching through the power settings. Later PEP units had thyristor control with smoother acceleration and no clicks.

Regarding the video, although it is an AC overhead EMU I imagine everything involved with the traction electronics was transformed DC back in 1966.

The 1950s/60s AC overhead units did indeed have DC motors but they used tap changers for power control.

 

[AM9]

Camshaft control? Class 313 units had a very distinct sequence of clicks and perceptible jerks when accelerating which were caused by the camshaft switching through the power settings. Later PEP units had thyristor control with smoother acceleration and no clicks.

Regarding the video, although it is an AC overhead EMU I imagine everything involved with the traction electronics was transformed DC back in 1966.

Most ac electrics in the '60s had multi-tapped transformers, which were less likely to produce damaging arcs when switching the secondary outputs. The exceptions were the converted 1500VDC classes i.e. the GEML 306 & 307s, and the ex LMS AM1s used on the Lancaster Morecambe and Heysham branch. The GE sets had rectifiers immediately after the transformers and the existing resistor banks were retained operating with 1500V as they would have in their DC days. The Lancaster units were converted from 3rd rail stock so used their resistor banks (presumably at c. 600VDC.

 

[Bringback309s]

Thanks for all of the replies, AM9 it sounds like you might be right about the converted 306's / 307s - the noise I remember wasn't quite like the one in the video, it was more like something "thrashing away", hard to describe! But I think we're on the right lines

 

[AM9]

Thanks for all of the replies, AM9 it sounds like you might be right about the converted 306's / 307s - the noise I remember wasn't quite like the one in the video, it was more like something "thrashing away", hard to describe! But I think we're on the right lines

 

[AM9]

The serial to parallel changeover on the 306s was often a bit edgy, especially as the next overhaul drew nearer. To avoid having to completely break the heavy current draw during acceleration, motors at the earthy end of the serial chain were shorted to ground before their positive terminals were connected to the supply. This often caused them to trip if the changeover was a bit hesitant causing repeated retries. The ensuing clack, clack, clack, and simultaneous jerks at about 20mph were a regular occurrence in their heyday.

 

[AM9]

Thanks for all of the replies, AM9 it sounds like you might be right about the converted 306's / 307s - the noise I remember wasn't quite like the one in the video, it was more like something "thrashing away", hard to describe! But I think we're on the right lines

The transformer tap changing was more of a softer kerchunk kerchunk sound, accompanied by a step up in the 100Hz transformer buzz level which faded before the next step. That was very noticeable in the quiet compartments of the MBKs on the 309s.