Metro-North finishes 3rd track - Commentary

Problem with slip/slide systems is unless they can determine ground speed they don't act if all wheels on a car slide.
Tthey only see different speed on single car, so if their all stopped or all spinning at same rate the slip/slide does nothing.
A Genesis use to have a Doppler radar to see ground speed vs rim speed but due to problems in snow they were disconnected.

I wonder if it'd be possible to use some sort of accelerometer and such to guesstimate the train speed from the known speed before braking and changes in acceleration beyond there, and try to relate that to wheel speed? I know the current crop of solid state ones are pretty good, but I don't know if they're THAT good yet...

Dutch,

I have to get the cobwebs out of my head, but I'm sure either the M-1 or the M-3, or both, have synchronous slip/spin circuitry. The circuit is based on a rate-of -change sampling. I.E. if all the wheels are turning at 60 MPH, then, say, one half second later, all the wheels are turning at 0 MPH, something is definitely amiss. The car is, without question, in a slide.

The M-7 has all sorts of fancy spin/slide circuitry, and even anticipation of a wheel slide about to occur. If I can find the info, I'll post some of it. (Don't want copyright / intellectual property suit.) Don't know what went wrong with those 10 M-7s. But the flat spots were real klunkers. It would appear that the wheel slip system didn't work at all on those cars. Time for the computer programmers to look over the software.

Tom

ASEA had a patent back in the 70's on a wheelslip control for locomoives that worked on rate of change. I think it monitored TM current, too. I believe they eventually expanded it to deal with torsional windup in the axles, even, and I think by the time BBD sucked them in, they were getting pretty crafty in that realm.

Today, given how dirt cheap a DSP, or even full up 32/64 bit microprocessor (even a high end chip like a PowerPC or 68060 is around 100 bucks in lots of 1000) is, it's easy and fun to do all sorts of calculations in software to take everything into account. I wouldn't be surprised at all if the M-7s take into account such things as torsional windup, brake shoe friction changes w.r.t temperature, car weight, weight shifts, etc. Lots of possibilities, and heck, even with a sampling rate on the order of 1000 a second, any decently powerful micro is gonna be sitting around twidlling it's thumbs 90% of the time anyway.

Brake Assurance (Emergency Brake application holdoff) in the LIRR M-1 is also a rate-of-change sampler. I don't know if MNRR M-1a has the same 386 card. They may have decelerometers.