M7 question

[N340SG]

A while back in this forum I quoted a passage from a book from the manufacturer that the M-7 top speed is limited by the propulsion system computers to 100 mph. Yes, that 100 mph max would be assuming that the ATC was cut out. Otherwise, 80 mph is tops, as you guys know.

The ability to do over 80 mph in certain places between Metropolitan Avenue and Harold some years ago was due to an anomoly, that being a higher MAS current than should have been in the rails that enabled the Engineer to effectively attain an electric cutout of the ATC. That situation has been rectified. You're not crazy. Trains did occasionally go above 80 at that time, in that area. I was in a few of them.

The MAS speed limit could conceivably be enforced by the modern computerized propulsion system (sort of like cruise control in your car), but is not on LIRR equipment.
On all our equipment, the current speed limit is enforced by cutting off propulsion power and putting on the brakes when in an overspeed condition.
Brakes can be released and tractive effort reapplied as soon as the overspeed condition is cleared.

Tom

[jtr1962]

Thanks Tom, that answers my questions and also tells me I wasn't seeing things. So basically then when you go over 80 the traction motors shut down and the brakes come on, presumably correcting the overspeed condition right away. Good to know the train doesn't go into emergency or need to come to a complete stop before everything can be reset. The passengers would be fuming I'm sure.

More questions, mostly on the physics. Anyone ever time the acceleration of these, with time from a dead stop to 80 mph (or better yet 100 mph) in 10 mph increments? I'm curious in case someone ever makes an M7 for MS Train Simulator so I can get the physics right. Also, any idea of how the dynamic brake tractive effort curve looks over the speed range, and also maximum service/emergency braking deceleration? I tried to find this data, perhaps from when the cars were tested, but was unable to. Actually, that sort of data isn't that easy to find for any train, at least on the Internet.

[Long Island 7285]

I have budd M1s and M3s for MSTS, i can fwd you the info in the .eng file to check it out to see if its right maby i will just post it.

also during test trials does the LIRR disable ASC and allow 100mph max to test the full potentical of all the M7s before being released into the useable fleet?

[jtr1962]

Long Island 7285:

I sent you a PM about the MSTS files since it's a bit off-topic for this thread. As to your other question, I believe ASC is disabled during trials but others here probably know more about that than I do.

[RetiredLIRRConductor]

There used to be a cut-off loop on 2 of the mainline tracks between jay and harold. This was about 20 years ago. All the engineer had to do was hold the speed controll button down while going through the loop at jay, and as the train cleared it the asc would cut out until harold where it cut back in by itself. Needless to say, on many a train where "last train rules" were ineffect, there were some incidents of speeding to make up time. I personally was on an M-1 that was "pinned" on the old speedometer going 120 between forest hills and the win curve. This could also be done in the atlantic tunnel between dunton and east ny, and with that cement track bed down there, the m'1s used to fly!

[Nasadowsk]

Didn't the origional ASC implementatiuon on the M-1's allow 100 as the max? I know the pics in Budd's little blue book show it.

Oh yes, they also state that the car was in fact safe to 80 (or 100?) with a popped airbag. Though ride quality would 'be seriously degraded'

[Frank]

I have another question about the M7s:

Do they have disc brakes?

[Long Island 7285]

I beleive they do. Looks to me as if the braeak roaders or on the wheel its self.

[Form 19]

LIRR Condr

They eliminated that ASC CO loop about 17 yrs ago wasn't it? I remember that when you travelled west on Mainline 4 or east on Mainline 3 it was 261 with Manual Block Signal rules in effect.

Do you remember getting a "Clear-Block" on the color lights out of Penn? That was definately different and I thought it was neat how such a busy terminal could have signalling like that still in service.

[DutchRailnut]

M7's have Wheel disks or Cheek brakes and tread brakes.
The Disks intead of mounted on the Axle are screwed to the Wheel itself.

[Long Island 7285]

Dutch, Thanks

You discribed my observations.

[Frank]

M7's have Wheel disks or Cheek brakes and tread brakes.
The Disks intead of mounted on the Axle are screwed to the Wheel itself.

If the M7s have disc brakes, then why do alot of them have flat spots? Shouldn't having disc brakes reduce the wear on the wheels.

[DutchRailnut]

The flatspots are not created by brakes, but a result of a sliding wheel from braking.

[N340SG]

To all,

Me not being savvy on the LIRR PCs, what was said about cutout loops on eastbound mainline 3 and westbound mainline 4 back then makes perfect sense, as those moves would be "against the grain".

In addition to that fact, though, I am referring to the fact that one could exceed the speed limit in the "normal" westbound direction of traffic on mainline 1 and/or 3 (once again, I didn't pay much attention to the exact detail of which track(s) we were on...I now wish I had...it was probably the express track) with ATC properly cut in, and with an MAS code. The difference is that, as I recall it, the Engineer had to continually hold the acknowledge button down during the entire time he wanted to boogie. The MAS code was still present, and if he let go of the button, it would kick the ATC back in and nail him with an overspeed. The anomoly was simply that the code current in the rails was higher than it should have been, and enabled the Engineer to effectively get an electric cutout when he shouldn't have.
This is because in the older equipmet, the MAS current path to the amplifier is forced to detour through a 62,000 ohm resistor when the acknowledge button is held down, and an MAS code is present. The resistor is designed to lower the high energy current value to the "normal" current value range. With a normal current MAS code, holding the button down should cause the MAS code to "flip", no cutout should be attained. In this case, the resistor is lowering the "normal" MAS code amperage value to a value that's too low to use. If the current is high enough by design, as in a cutout loop, you get your electric cutout. The "malfunction" was quite simply that the "normal" MAS current in the rails at certain points was high enough to attain a cutout. (It is also possible that this worked in some cars, but not others, based on amplifier pickup setting, which is adjustable into an acceptable range of values, and track receiver height, which is also adjustable into an acceptable range of heights.)

In any event, Engineers had to "know" about this, and as it became "common knowledge", it was picked up upon by the authorities and rectified.

Tom

[N340SG]

Didn't the origional ASC implementatiuon on the M-1's allow 100 as the max? I know the pics in Budd's little blue book show it.

Phil,

The oldest books do seem to indicate that the M-1 was ready to do 100.
There are several references in the book to 100 mph settings.
The older ADUs also had 100 mph labeled on them, with a green aspect lens, instead of yellow. (The zero aspect was a red light bulb.)
Even though MAS was ultimately enforced at 80mph, the aspect still was labeled as 100. All the ADUs were replaced many years later, with the correct labels on them.
I can't say for sure, but I don't think the cars were ever actually allowed to do 100 as policy on the LIRR.

As point of interest, the dusty old books also indicate that the codes were supposed to be sequenced in descending numerical order, I.E. 420 being MAS.
180 and 420 were flip-flopped. I don't know why. It is all before my time. I suppose maybe 180 was or became a standard for MAS, and the LIRR went along with the crowd?
This chart, scanned from the dusty old GE book, shows the original intended code sequence and speeds.

original M1 atc code chart 38k jpeg

Tom