Could M-8 style 3rd rail shoe enable conversion?

[MattW]

Before I get to the heart of my question, can I please ask that the railroaders and others "in the know" NOT jump all over me for this? This is a hypothetical question, born of pure curiosity about the technical merits ONLY! I'm not seriously suggesting MNRR do this, or saying that they are doing this, or anything at all like that.
Could a third-rail shoe like employed on the M8s enable Metro North to technically convert their system to under-running (LIRR-style) third rail? I have learned recently from reading this forum that the M8 doesn't have dual shoes like I used to think, rather it's a design of shoe that can work with both systems. If hypothetically speaking, every MNRR train had this type of shoe, would it be possible to implement a "phased" reconfiguring of the third rail such that the entire system still has both styles in use? Say one weekend they convert 5 miles to the LIRR style, then the next weekend, they convert 5 more, etc.
Again, this question is around the technical merits only, I know it will probably never happen for numerous reasons, and I guess the same question could be asked of the LIRR, could they be the ones that convert using the same style shoes, but since the MNRR M8s are the only ones using this design so far, and in the minority as far as third-rail type, I'm asking here.

[Backshophoss]

LIRR is Overunning 3rd rail shoe,MNR(ex-NYC) is Underunning 3rd rail shoe.
Both the M-7's and M-8's share the same shoe mount assembly.
The "kicker" is Amtrak's P-32dm's need space to let the shoes fold out into position before entering NY Penn,
MNR's P-32dm's are fixed position for underunning 3rd rail.
The FL-9's had a moveable shoe when 1st built with a shoe that would work with both styles of 3rd rail,but was a
maintance "pain in the neck" that PC did away with when the FL-9's were re-assigned to Harmon for commuter service,
and converted to fixed underunning shoe.

[lirr42]

I don't believe the M7's share the double-sided third rail shoes that their M8 counterparts have, Mr. Backshophoss (at least I know the LIRR's third rail shoes are for over-running third rail only).

But, if going forward all new equipment purchases were to be delivered with the M8-style dual third rail shoe, there would be no need to swap out any third rail. The M8 or M9 could just use whatever is currently there, and flip between the two systems painlessly. There's no real need to bother with ripping out what's currently there. It's just easier to make whatever the next generation of equipment will be (be it M9's or DC locos with multi-level cars) work easily on both systems.

[lirr42]

I found two photos Mr. Railnut has posted on here from time to time when questions like these arise. They show the old style third rail shoe, and the new style third rail shoe (currently on some M8's)

And in this photo you can see the LIRR's M7 third rail shoe.

[F-line to Dudley via Park]

OK...here's another hypothetical asked as a technical what-if only (i.e. don't "f**mer" me, bro). . .


Say in some future scenario electrification of the Empire Connection were desired for Hudson Line thru-running. Let's assume for a sec that sending P32's down to Penn off the Hudson Line proves such a smashing success that there's motivation to get the regular MU fleet down there instead of bogarting too many push-pull duals and coaches away from branchline duty.

Is there a way to 'flip' on-the-fly between under-running to over-running third rail with an M7, if MNRR were to install its own power collection on the 9 miles between Spuyten Duyvil and the wye track where the LIRR third rail ends? Or is that just not possible with any known shoe design? Because I suppose if it can't and you absolutely had to have MU's down the Connection hell or high water the only alternative would be using overhead on the Connection and M8's as the gap-filler between third rail types.

[Backshophoss]

Revive the original moveable shoe mount design that EMD used with the FL-9's,update it as needed(NO air lines) and
make it a easy retrofit "kit" for all P-32 dm's. May not be possible for LIRR's DM-30's however.

[Clean Cab]

OK...here's another hypothetical asked as a technical what-if only (i.e. don't "f**mer" me, bro). . .


Say in some future scenario electrification of the Empire Connection were desired for Hudson Line thru-running. Let's assume for a sec that sending P32's down to Penn off the Hudson Line proves such a smashing success that there's motivation to get the regular MU fleet down there instead of bogarting too many push-pull duals and coaches away from branchline duty.

Is there a way to 'flip' on-the-fly between under-running to over-running third rail with an M7, if MNRR were to install its own power collection on the 9 miles between Spuyten Duyvil and the wye track where the LIRR third rail ends? Or is that just not possible with any known shoe design? Because I suppose if it can't and you absolutely had to have MU's down the Connection hell or high water the only alternative would be using overhead on the Connection and M8's as the gap-filler between third rail types.

The M8 3rd rail shoe is capable of using either under running and over running 3rd rail without any action by the engineer. The shoe itself has a set of springs in the mechanism that keep a double sided shoe at a neutral center position. It automatically adjust to either style of 3rd rail in encounters. The original plans did call for an air powered device to raise/lower the shoe that the engineer would control by using a switch in the cab, but that proved to be a maintainance nightmare. A German engineering firm called Schunk was contracted to address the problem and developed the center sprung mechanism using special double sided shoes, and it has worked well so far in tests, but I am unaware of them being used in any real world test between the two different styles of 3rd rail because the M8s have only operated on MN territory so far.

[DutchRailnut]

before these shoes were installed on M-8, two pair of MNCR M7a's and two pair of LIRR M-7's ran on their home roads for testing.

[Clean Cab]

I had heard of plans to use them on both M7's and LIRR 3rd rail, but have they been used in an actual transition from one style of 3rd rail to the other?

[F-line to Dudley via Park]

I had heard of plans to use them on both M7's and LIRR 3rd rail, but have they been used in an actual transition from one style of 3rd rail to the other?

Yeah, that was my technical question in the earlier post. I know overhead to either type of third rail is proven to work, even on the same trip. But can any known shoe design go bang-bang from one type of 3rd rail to another at a single phase break? In the purely hypothetical scenario that would ever be needed.

[Clean Cab]

I guess we'll find out when MN starts testing M8's to Penn Station via the Hellgate Branch. Don't hold your breath for that to happen anytime soon though.

[Ridgefielder]

I guess we'll find out when MN starts testing M8's to Penn Station via the Hellgate Branch. Don't hold your breath for that to happen anytime soon though.

Actually we won't-- unless MN is planning to rip out the catenary on the Hell Gate and replace it with NY Central-style 3rd rail.

[lirr42]

I would think an overrunning/under running third rail transition would go fine. You just put a couple feet of open space in between where one ends and the other one begins (i.e. don't have under running third rail on the left side and overrunning third rail on the right side of the train for a mile)

So the trains traveling on the under running third rail with its shoe flexed in the downward position, it reaches the end of the third rail, the shoe comes of the third rail, springs back to the neutral position, and about 200 feet later, the overrunning third rail begins, the shoe flexes up, regains power, and then it's off on its merry way.

200 feet of open space would ensure that all eight contact shoes on a married pair were not touching both third rails at any one time (just in case there's a phase break issue or something like that). It would be just like going over a wide grade-level crossing. The rest of the other cars will push/pull the dead pair over the gap and everything would go swimmingly.

[Backshophoss]

The Question then becomes how long a gap is needed to allow Amtrak's P-32 shoe to get into position from folded up.
At speed to boot(60mph),otherwise NO empire connection access for MNR Hudson Line trains.

[lirr42]

I don't think Hudson Line trains would be using eletric trains to get into NYP. I don think electrifying the Empire Connection with either type of third rail is even on the table at this point.