FS Triphase Electric Locos

[Brian Harrap]

It's been bothering me for some time so I thought, if I ask some one might know the answer. I have noticed some Italian triphase locos have what looks to me like a toilet seat over or about the flycranks of the rod drive - see pic. Can anyone tell me what they are and what they contain? 

 

Stay well and thank you.

 

Brian

[Nearholmer]

My guess is that they are guards/covers over the ends of the traction motors, where, I think, the motor shaft is connected to a yoke-type connecting rod, which in turn drives the axles.

 

They may simply be guards, rather than covers of enclosures, to reduce the risk that anyone or anything on the platform will get caught in all those bits of metal whirling about.

 

Here are a couple of pictures of the ‘mincing machine’ without covers, which I think confirm my guess.

 

 

 

 

Edited April 4, 2020 by Nearholmer

[Brian Harrap]

Thank you Nearholmer but I think there's more to it than that. Some of the 'covers' I've seen on locos in museums (why didn't I look closer) are quite substantial affaires - more than just a guard. Also some classes have only one crank 'covered'. I'm sure there is something or some workings inside.

 

Regards, Brian

[Nearholmer]

Hmmmm ........ peering very closely at photos taken at angles, I see what you mean.
 

Some of the ‘guards’ have depth, and look quite substantially constructed.

 

I’m beginning to wonder if they contain ‘search coils’ that electrically detect the movement of the fly-cranks, or a pancake-shaped alternator, to provide a tacho/speedometer function or act as part of a semi-closed-loop control system to change the resistor settings in response to track speed.

 

It will take a while to reread the text to see if that mentions them, and I will look in another book which contains better drawings and might even contain circuit drawings, to see if that contains clues.

 

 

Edited April 5, 2020 by Nearholmer

[EddieB]

Here's a photo I was trying to upload last evening (when RMweb had a wobble), taken of the preserved example at TM Speyer, which shows the depth of these structures.  Like Kevin, I thought they were simple covers, similar to the skirting arrangements adopted in other countries (and including a favourite of mine, the SNCF 2D2 5538 series).

 

I trying to think if and where I may have a drawing of these locos.

 

 

Edit: I note that the locomotive illustrations in Kevin’s response are of the later E470 series, when the question refers to the E431 series (the photo at Savigliano is from Wikipedia, my photo being of the other preserved example).  In these locos the drive mechanism was in an ‘A’ configuration from a central motor with two diagonal “arms” driving a horizontal “beam” (which can be seen in the Savigliano photo, but appears missing from the Speyer one).

Edited April 5, 2020 by EddieB

[Brian Harrap]

Thank you  both for your interest and support. I quite like the tacho/speedo etc idea but why would they need four of them as the motors are mechanically linked. I am also intrigued by the books you may both have on the subject  - something i haven't  gone into before and now I find it fascinating.

Brian.

[Nearholmer]

You’re probably right about the tacho-generator, and in fact in that second picture that I posted, I think you can see a very small one on the RHS ..... ideal for a speedo.

First book for this topic is as below, but I’ve also got a number of contemporary textbooks, which contain circuit drawings for a selection of locos. There were several different methods used to control three-phase traction motors before power electronics, so they tend to focus on that matter, rather than going into the different classes.

 

 

 

[Allegheny1600]

Hi Brian,

I got rather keen on these fascinating machines a while ago, if you can use Google Translate, you might find this interesting: http://www.stagniweb.it/trifase4.htm

Ciao,

John.

[EddieB]

Looking up the FS class 623 for another thread, I'd forgotten that Paul Kalla-Bishop's book "Italian State Steam Locomotives" also includes brief coverage of tri-phase locomotives and railcars.  Reference to other classes that had similar drive mechanisms and "toilet set lids" gives what I think is the answer.

 

The originator of this "system" was the E330 class 1-C-1E of 1914.  Like the later E431 class 1-D-1E of 1922, they had two body-mounted traction motors.  To quote PMK-B:

 

"The motor rotors were coupled to a downward pointing triangular plate, the apex of the plate enclosing the crank pin of the centre driving wheel.  The plate could move up and down on the crank pin to allow for springing movement, and coupling rods to the other two driving axles were connected to plate wings on either side of the crank pin".

 

The rotating outer angles of that triangular plate fit behind the "toilet seat lids" 

 

My photo of E330.008 as preserved at Milano (the b&w version gives marginally more shadow detail) gives a suggestion of this arrangement (unfortunately the cramped conditions did not allow a more side-on view).  There are perhaps better illustrations available on the web.

 

 

The E550 (1918) and E551 (1921) 0-E-0E also had a similar arrangement, but with one outer angle of the triangular plate behind the cover, the other "naked".  Here's another cramped shot at Milano - E550.030 as preserved there.

 

 

[Nearholmer]

Hmmmm ......... isn’t Mr Kalla-Bishop (whose son I worked with for a few years) giving a rather clumsy description of the fly-crank and yoke arrangement?

 

And if, as I suggested in my first post the ‘toilet seats’ are guards for the cranks, why guard only some of them? 

[Brian Harrap]

Thank you all for you input on this matter. I particularly appreciate the link you sent John, a very well detailed account which will take me a while to digest, but at least I now know whats in those boxes  and what it does. I had raked over the 'junk' at Piedmont but had missed the disassembled motors.

Interesting shots at Milan Eddie which compliment some of my own - I also spotted a large electric loco there, a DC machine with 3rd rail collector shoes which was new to me. Wonder if I'll start modelling Italian now. BTW the toilet seats on the Rivarossi 431 I have aren't reproduced anywhere deep enough.

Thank you all again for you help and interest in this subject.

Brian 

[Nearholmer]

Here’s another picture to pore over. Not the class in question, but the best one I can find showing a ‘toilet seat’, and I’m still not sure what it’s for!

 

One thing this has caused me to do is read-up on the way the automatic control of the liquid rheostats on these locos worked, and  it involved two pumps, one to circulate the liquid to keep it cool and evenly mixed, and a compressor to provide pressurisation, which was used to alter the liquid level around the electrodes. All of which makes me wonder whether one of the pumps was driven mechanically from the crank that is covered by the ‘toilet seat’, rather than being driven by a small electric motor, but that seems a tad unlikely.

 

 

[Nearholmer]

p338 et seq of this book are all about 3-phase locos, and one of the descriptions refers to an "induction regulator" being used as part of the automatic control circuit (https://en.wikipedia.org/wiki/Induction_regulator) .

 

Now, I have to confess that I've never come across an induction regulator, but it might fit with my earlier speculation:

 

"I’m beginning to wonder if they contain ‘search coils’ that electrically detect the movement of the fly-cranks, or a pancake-shaped alternator, to provide a tacho/speedometer function or act as part of a semi-closed-loop control system to change the resistor settings in response to track speed."   Wrong! See below.

 

I shall continue to delve, because, as might be evident, the control of these locos intrigues me.

 

Exciting news    .......... p209 of the same book contains a photo of the motor of such a loco "naked", and it can be seen that there is an extension of the shaft, beyond the fly-crank and the drive-pin for the yoke, to support  what look like four slip-rings (TP&N I guess), which would sit in the centre of the "toilet-seat".

 

I conclude from this that the "toilet seat" contains not coils, but brush-gear.

 

Now, I need to work out what it does! The thing that intrigues me is that the slip-rings can't be connected to the rotor (unless the Italians had some magic cable), and I can't see why they might be needed.

 

Unless ...... the rotor is connected to the slip-rings by cables that run in channels formed in the fly-crank and the yoke-drive pin .......... just about conceivable ....... in which case the slip-rings make perfect sense as part of the motor speed-control circuit.

 

Edited April 7, 2020 by Nearholmer

[Brian Harrap]

40 minutes ago, Nearholmer said:

p338 et seq of this book are all about 3-phase locos, and one of the descriptions refers to an "induction regulator" being used as part of the automatic control circuit (https://en.wikipedia.org/wiki/Induction_regulator) .

 

Now, I have to confess that I've never come across an induction regulator, but it might fit with my earlier speculation:

 

"I’m beginning to wonder if they contain ‘search coils’ that electrically detect the movement of the fly-cranks, or a pancake-shaped alternator, to provide a tacho/speedometer function or act as part of a semi-closed-loop control system to change the resistor settings in response to track speed."   Wrong! See below.

 

I shall continue to delve, because, as might be evident, the control of these locos intrigues me.

 

Exciting news    .......... p209 of the same book contains a photo of the motor of such a loco "naked", and it can be seen that there is an extension of the shaft, beyond the fly-crank and the drive-pin for the yoke, to support four slip-rings (TP&N I guess), which would sit in the centre of the "toilet-seat".

 

I conclude from this that the "toilet seat" contains now coils, but brush-gear.

 

Now, I need to work out what it does!

Do check out Allegheny 1600 post above with link www.stagniweb.it/trifase4.htm. Fascinating

Brian

[Nearholmer]

We've got it ......... the toilet-seat contains brush-gear to connect to slip-rings, which are in turn connected to the rotor of the motor.

 

For the seven-ring "Milch" connection referred to in the write-up that Allegheny links to, there will be three rings on one end, four on the other, and the circuit diagram for connection to external resistor banks will be as here (Dover, "Electric Traction", 1919 Edition.).

 

The thick bars in the diagram are electrodes, which begin barely-immersed in electrolyte, which offers high resistance. As the electrolyte level is increased, more and more of the electrode is in contact with it, and the resistance fall to near-zero, at which point (not shown in diagram), a shorting switch operates, taking the resistors out of circuit entirely.

 

The slip-rings can also be used to connect the rotor of the first motor to the stator of the second, to achieve cascade connection, or for pole-switching, so any* of the methods of speed-control available before power electronics.

 

The fly-crank and drive-pin must indeed contain channels for the cables to connect to the rotor-winding ....... clever chaps these Hungarians!

 

 

*I'd have to think a bit longer to see if they work with full Kando-convertor control.

 

 

 

 

 

 

Edited April 7, 2020 by Nearholmer

[Nearholmer]

For completeness, here is the rotor connection schematic, also from Dover.

 

 

 

 

The slip-rings must be place "far outboard", instead of close-up to the stator, on the main shaft, rather than a complicated extension of it, to maximise the size of the main stator and rotor windings within the width of the locomotive, without having to resort to sitting the motor higher-up, raising the centre of gravity and increasing the length of connecting rods (some early-ish electric locos had hugely long connecting rods).

 

Thank you Brian for setting this puzzle ..... it has been a good way of having a mental break from the dreaded.

 

 

 

 

 

 

Edited April 7, 2020 by Nearholmer

[Brian Harrap]

I was with you all the way up to 'simply'.

Really I have enjoyed this discussion, thanks.

Brian.