Train Motors

[q8]

Q8 coupling up.
I wonder if when the new SSL trains come they will have some really modern innovations. For instance monomotor bogies I.E. one transverse motor driving both axles through hyphoid gears. Or plug type passenger doors and possibly, just possibly, articulation. Perhaps they could be fitted with super accurate speedo's of the laser type. If a laser mouse for a computer can detect miniscule movement think of the accuracy of a speedo using the same technology modified. After all the train firms are always looking to cut costs perhaps those ideas can help them do that.

Q8 uncoupling

[DrJimi]

A few thoughts provoked by yours...
A monomotor bogie implies, of course, that the new motor could supply the same torque (tractive effort) as the two motors it replaces (assuming it has to provide the same performance for the same weight moved). It would likely be an AC motor - so does such a motor exist that can provide the oomph, be small enough to fit, and efficient enough not to get too hot?
Can a small enough hypoid gearset be built so provide the needed gear ratio? Let's assume for sake of discussion the wheel size is as for D Stock, as is the requried gear ratio (although that would depend on the balance speed for the new AC motor needed, noted above).
You don't need a laser for an accurate speedo. The refurb D Stocks already have GPS, which can provide more than enough accuracy - when it can see the birds. For 'dead' areas (tunnels?) why couldn't an accurate-enough wheel or transmission driven speedo be built? Or maybe an electronic speedo that 'counts' motor pulses (AC motor driven by chopper-type circuit and inverter) and knowing gear ratio and wheel size can calc the speed?

/Jimi (who loves pondering mechanical stuff)

[igelkotten]

Having done quite a bit of work as a test train driver with the development of the C20 car, which is the granddaddy of the Movia platform which Bombardier will base it's new SSL train on, I can perhaps throw some light on the innovations or lack thereof in the coming new SSL units.

First of all, monomotor bogies are in use in Metro/underground applications here and there around the world -France and Japan being two of the places it is used. From what I understand, it is now generally considered to offer a better degree of control, cheaper,when using a one motor per axle and IGBT controlled AC traction motors. Modern asynchronous motors are also compact enough that part of the advantage of monomotor bogies are negated that way, too.

The traction package will most certainly be a variant of the ICON-MACS system with MITRAC control software & firmware, originally developed for use on the C20 cars, with a distant ancestor to MITRAC fitted to the 92 TS for fault diagnosis and status monitoring purposes.

In other words, completely electronic, with IGBT units switching the traction current to precisely controlled AC pulses to power the traction motors.

Other units in Britain using variants of this family of control packages are the Electrostars -cl 357, 375 and whatever they are called.

Driver control is completely fly-by-wire -when you move the controller handle forward, you are essentially telling the vehicle control unit that "I want to accelerate this much", and then the control unit calculates and decides how this is going to be implemented in practice.

The FICAS technology of building very thin, vaccum-formed carbodies in sandwiched composite materials,that at the same time acts as loadbearing units, more or less presupposes the use of slide-plug doors for various practical reasons.

There will probably be very little, if any, of the traditional ribs-and spars in the construction of the carbody. It will, rather, be a series of flat panel modules glued (yes, glued!) together to form the carbody. This will then be fitted to an underbody solebar frame, with a moulded composite front end bolted on if a driver's cab is required, or a gangway if it is to be an end or middle unit.

Articulation is, I think, something you can take for granted. The question is how big the smallest units will be, whether two or three or four cars will make up a full length train.

The interior might very well end up modular -there is at least a lot of fluff about that being tossed around by Bombardier at the moment. That is, due to the constructin of the FICAS carbody, the interior furniture will mostly be fastened and hung from a series of hardpoints along the interior, hardpoints which can be placed more or less as the customer wishes, making it possible to, for example, remove a group of seats in summer in order to create a bike space.

Speedos based on laser or radar reflection are in use here and there already, but they have their own set of problems. Your bog-standard axle-mounted tachogenerator becomes inaccurate when you encounter a lot of wheelslip. Laser or radar -based sensors can get problems with reflections from surfaces other than the trackbed -pools of water, for example- leading to a lot of inaccuracies in the readings.

The option that seems to be most commonly used today is to get a speed reference from several axles at once and compare them electronically to each other.

Indeed, as Dr. Jimi hints at, an automatic part of modern semi-conductor based traction control systems is that they count each and every wheel revolution and compare to the other powered axles, since they have to ensure that all axles of the train are travelling at the same speed. A common fault message in our C20 cars is "wheel diameter fault detected" -most often caused by a small wheelslip, and usually rectified by just coasting for a few seconds.


/Igelkotten

[q8]

Thank you gentlemen for the replies. I found them absolutely fascinating although a bit hi-tech for an old fart like me. As for the speedo issue could not the laser be reflected off of the running rail? After all it's there all the time.

Speaking of running rails I have to go into hospital rather a lot with angina and they now use beds made of a black plastic sort of stuff. The last time I was in a chap in there was telling me that this stuff was strong enough to make railway lines out of. Was he pulling my plonker or was that a genuine statement