METRA to Purchase SD70MACs for commuter service.

Krieglok posted:
Hot Water posted:
Dominic Mazoch posted:

And how fast will these locomotives have to go in commuter service?  My guess is they will need to go much faster than passenger trains on the Alaska.

I would think that they should be capable of at least 75 MPH.

They will likely be geared for passenger service rather than freight, giving them a higher top speed. The gearing for passenger locomotives reduces the overall tractive effort for heavy loads but increases the acceleration rate from a standstill as well as giving the higher top speed...

I wish NJT would consider these engines in the future!

Tom

For what it's worth, the BN/BNSF SD70MAC units were already "geared" for 70MPH with the overspeed set for about 72 in the speed-control system. Unlike a DC traction motor, with its copper commutator bars that are subject to damage from high centrifugal forces, the AC three phase induction tractor motor rotor is not seriously affected by centrifugal forces.

Dieselbob posted:

How fast do Metra trains actually run? 

I believe it depends on the line, i.e. UP or BNSF for example, but they have lots of 79 MPH speed limit areas.

The couple that I have rode didn't really ever get up that much speed, but we were not going very far out of downtown.

I'm pretty sure that the express trains that METRA runs on the BNSF line we live on, operate over 70 MPH.

 

Hot Water posted:
Dieselbob posted:

How fast do Metra trains actually run? 

I believe it depends on the line, i.e. UP or BNSF for example, but they have lots of 79 MPH speed limit areas.

The couple that I have rode didn't really ever get up that much speed, but we were not going very far out of downtown.

I'm pretty sure that the express trains that METRA runs on the BNSF line we live on, operate over 70 MPH.

 

I'd have to clock one but the BNSF line express trains I've seen appear to be doing close to the 79mph limit at times, along with some west cost bound Amtrak trains. But La Grange/Brookfield have a lot of buildings around the tracks, making it harder to judge speed without measuring. Not like BNSF doesn't run intermodal trains at a good clip through the area.

When the SD70MACs were produced what was their top speed? I though I remember an article from the early 90's in Trains magazine saying they topped out around 70 mph, but I'm probably way off.

Santa Fe, All the Way

Lou1985 posted:
Hot Water posted:
Dieselbob posted:

How fast do Metra trains actually run? 

I believe it depends on the line, i.e. UP or BNSF for example, but they have lots of 79 MPH speed limit areas.

The couple that I have rode didn't really ever get up that much speed, but we were not going very far out of downtown.

I'm pretty sure that the express trains that METRA runs on the BNSF line we live on, operate over 70 MPH.

 

I'd have to clock one but the BNSF line express trains I've seen appear to be doing close to the 79mph limit at times, along with some west cost bound Amtrak trains. But La Grange/Brookfield have a lot of buildings around the tracks, making it harder to judge speed without measuring. Not like BNSF doesn't run intermodal trains at a good clip through the area.

I am currently trying to find out what the maximum speeds are for METRA trains on the BNSF and UP lines.

When the SD70MACs were produced what was their top speed?

The BN had the speedometer overspeed trips set for about 72 MPH. Naturally the maximum speed was never reached on loaded or empty coal/hopper trains. If and when they were ever assigned to intermodal trains (very rarely), the could run 70 MPH.

I though I remember an article from the early 90's in Trains magazine saying they topped out around 70 mph, but I'm probably way off.

No, you are correct.

 

Hot Water posted:
Lou1985 posted:
Hot Water posted:
Dieselbob posted:

How fast do Metra trains actually run? 

I believe it depends on the line, i.e. UP or BNSF for example, but they have lots of 79 MPH speed limit areas.

The couple that I have rode didn't really ever get up that much speed, but we were not going very far out of downtown.

I'm pretty sure that the express trains that METRA runs on the BNSF line we live on, operate over 70 MPH.

 

I'd have to clock one but the BNSF line express trains I've seen appear to be doing close to the 79mph limit at times, along with some west cost bound Amtrak trains. But La Grange/Brookfield have a lot of buildings around the tracks, making it harder to judge speed without measuring. Not like BNSF doesn't run intermodal trains at a good clip through the area.

I am currently trying to find out what the maximum speeds are for METRA trains on the BNSF and UP lines.

When the SD70MACs were produced what was their top speed?

The BN had the speedometer overspeed trips set for about 72 MPH. Naturally the maximum speed was never reached on loaded or empty coal/hopper trains. If and when they were ever assigned to intermodal trains (very rarely), the could run 70 MPH.

I though I remember an article from the early 90's in Trains magazine saying they topped out around 70 mph, but I'm probably way off.

No, you are correct.

 

Huh. I remembered something accurately for once.

If you find the max speed on BNSF/UP let us know. Otherwise next time I'm in downtown La Grange I'll try clocking an express train.

Santa Fe, All the Way

Hot Water posted:
Lou1985 posted:

Otherwise next time I'm in downtown La Grange I'll try clocking an express train.

Without a pretty accurate radar gun, how would you plan on doing THAT?

 

 

The old fashioned way. Time it takes to travel a set distance. Although a radar gun or laser timers would be much more accurate.

Santa Fe, All the Way

OK, latest information from METRA:

1) On BNSF and UP lines, the speedometer overspeed is set at 72 MPH, as both railroad's maximum speed for METRA is 70 MPH.

2) The Milwaukee Road and Rock Island lines, the overspeed is set at 82 MPH, as the max speed for METRA is 79 MPH.

Hot Water posted:
The GN Man posted:

Interesting thread, especially Jack's notes above...

My understanding of the Alaska RR SD70MACs in passenger service (4300-series) is that internal switching disconnects the rear traction inverter from the rear truck traction motors and this inverter then provides 480V 3-phase HEP to the train. This locomotive then has just its forward truck powered, so ARR usually has a second unit in the consist to provide adequate traction for the train. When the unit is in freight service, or another HEP source is available, then all six axles are powered.

I am wondering if the METRA SD70MACs will be the same, or if they found a way to squeeze in an additional inverter for the HEP while keeping all traction motors operative?  

According to what I've read elsewhere, this "new", i.e. completely re-manufactured units, will have 6 inverters: 4 for traction (there would thus be only 4 AC traction motors), and 2 for HEP. 

Soooo,  maybe they are becoming like the current C4 variants (either A1A or B1)?

And METRA stipulated in the article they will meet Tier III requirements.

rdunniii posted:
Hot Water posted:
The GN Man posted:

Interesting thread, especially Jack's notes above...

My understanding of the Alaska RR SD70MACs in passenger service (4300-series) is that internal switching disconnects the rear traction inverter from the rear truck traction motors and this inverter then provides 480V 3-phase HEP to the train. This locomotive then has just its forward truck powered, so ARR usually has a second unit in the consist to provide adequate traction for the train. When the unit is in freight service, or another HEP source is available, then all six axles are powered.

I am wondering if the METRA SD70MACs will be the same, or if they found a way to squeeze in an additional inverter for the HEP while keeping all traction motors operative?  

According to what I've read elsewhere, this "new", i.e. completely re-manufactured units, will have 6 inverters: 4 for traction (there would thus be only 4 AC traction motors), and 2 for HEP. 

Soooo,  maybe they are becoming like the current C4 variants (either A1A or B1)?

And METRA stipulated in the article they will meet Tier III requirements.

Since the trucks are 3 axle, the traction motors will be mounted on the first 2 axles within each truck, providing an AAR powered wheel arrangement of A-A-1  1-A-A. Remember that E Units were A-1-A  A-1-A, with the unpowered "idler" in the center position. With the HTC-R "Radial" truck, the "idler" will be on the end, or inboard position.

Krieglok posted:
Hot Water posted:
Dominic Mazoch posted:

And how fast will these locomotives have to go in commuter service?  My guess is they will need to go much faster than passenger trains on the Alaska.

I would think that they should be capable of at least 75 MPH.

They will likely be geared for passenger service rather than freight, giving them a higher top speed. The gearing for passenger locomotives reduces the overall tractive effort for heavy loads but increases the acceleration rate from a standstill as well as giving the higher top speed...

I wish NJT would consider these engines in the future!

Tom

For commuter service?  Passenger gearing?  The SD70MAC's have been routinely operating on BNSF at 70 MPH on coal trains and other freight trains on former ATSF territory.  Does METRA operate commuter trains faster than 70 MPH?  And, if so, do the longer, heavier, commuter trains actually have enough time to get up to 75 or 79 MPH between stops and can METRA trains achieve and maintain a speed in excess of 70 MPH for long enough to make any real difference in the schedules?  70 MPH=51 seconds/mile.  75 MPH=48 seconds/mile.  79 MPH= 45 seconds/mile*.  So, as opposed to using a 70 MPH gearing, to shave a minute of running time between stops at 75 MPH, the train has to operate at 75 MPH for 20 miles.  To shave a minute of running time between stops at 79 MPH, the train has to operate at 79 MPH for 11.3 miles.  While speeds above 70 MPH are certainly beneficial to the schedules of most inter-city passenger trains, the shorter distances between stops in commuter service eat up much of the higher speed advantage with the reduced amount of time available to maintain higher speeds.  Also, if a train has to reduce for curves or - worse - to proceed through crossovers (as when weaving through traffic or running around a slower, non-express train), the higher speed advantage is reduced or eliminated.

I'm not saying that there would be any significant additional cost in the rebuilding process (none at all if new ring and pinion gears are specified as part of rebuilding).  I am only questioning whether passenger gear ratios are useful for METRA service, because their purpose is to allow running time to be reduced by maintaining higher speed.

*  These speed/time equations are slightly rounded to avoid using fractions of seconds.  The equations, as presented, are the accepted standard for measuring speed between mile posts.

Tom

 

Superintendent, High Plains Division (O Gauge) 

The Panhandle & Santa Fe Railway Co.

Lone Star Hi-Railers

Santa Fe, All the Way

To re-emphasize what Tom just posted above, the BN/BNSF SD70MAC units, having AC three phase induction traction motors, are NOT affected by higher RPM rotor speeds (they do NOT have the copper bar commutator as DC motors have). More than one SD70MAC unit was fully tested at the AAR Test Center, out in Colorado, and was also operated on the "Fast Track" at speeds up to 100 MPH. Nothing flew apart!

Dominic Mazoch posted:

Advantage of the A-A-1 traction motor arrangement for the AC truck vs A-1-A for the E units?

Completely different truck designs. The old/original Blomberg A-1-A truck (yes, the same Mr. Blomberg that later designed the famous 2 axle truck with 40" diameter wheels for the FT units) had only 36" diameter wheels. The HTC-R "Radial" truck is far superior, and due to its "steerable" design reduces flange contact/wear on curves, not to mention far superior adhesion for high traction situations.

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