Locomotive Descriptions and Phases - EMD SD70M-2, SD70ACe

CN #8843, a Phase 2e1 SD70M-2 seen in 2014.

The SD70M-2 and SD70ACe were a redesign of the EMD SD70 series aimed at meeting new emissions standards that took effect in 2005. While they shared many mechanical components with the previous SD70M and SD70MAC models, they received a substantially altered carbody and underframe that borrowed some features previously used in the SD80MAC and SD90MAC series. The air reservoirs and associated piping were all moved to the engineer's side while the traction motor cables were moved to the conductor's side, as on contemporary GE units. The dynamic brakes were moved from the front to the rear of the hood, and a wider radiator section was located behind a lowered and tapered central hood. The underframe was several inches taller than on earlier SD70 models and resulted in a shorter cab being adopted from the late-model SD90MAC. The radial-steering HTCR trucks used on previous SD70 models were updated (denoted "HTCR-4") and a simpler HTSC truck was introduced that lacked radial steering and rode on a shorter wheelbase.

Unlike the SD70M and SD70MAC (which rode on different underframes) the SD70M-2 and SD70ACe were nearly identical. The main differences were the substantially thicker and more numerous DC traction motor cables, smaller traction motors and absence of inverter cabinet vents on the SD70M-2. Visual changes over the production run were numerous but relatively minor, and as the SD70ACe outsold the SD70M-2 by a wide margin, the latter had fewer variations.

Phases

These phases are of my own making. As there was no single major change during SD70ACe production after 2005, Phase 1 denotes pre-production units. These phases do not include EMD's new Tier-4 version of the SD70ACe.

Phase	1a	1b	2a1	2a2	2b1	2b2	2c	2d1	2d2	2e1	2e2	2e3	2f
Dates	2003-04 - 2003-05	2004-04 - 2004-09	2005-10 - 2006-04	2005-01 - 2006-04	2006-02 - 2006-04	2006-05 - 2006-06	2006-05 - 2006-10	2007-02 - 2007-07	2007-08 - 2007-10	2007-10 - 2008-09	2008-05 - 2008-08	2008-09 - 2010-03	2010-10 - 2016
Jacking pads	open	flat plate (SD70ACe only)		flat plate (both models)						curved plate
Panels above d.b. intakes	3 rows of vertical louvers	3 columns of horizontal louvers	short doors		medium-height doors				shorter columns of louvers
Cab sub-base panels	hinged	bolted
Inverter cabinets	surface-mounted grills	flush grills						no grabirons on panel edges, no slot at top right corner
Rear sand fill step	No		Yes		No
Rear hood end grabirons	engineer's side		conductor's side
Phase	1a	1b	2a1	2a2	2b1	2b2	2c	2d1	2d2	2e1	2e2	2e3	2f
Rearmost conductor's side hood door	bolted on all sides		hinged with 4 bolts						hinged with 2 latches
Frame and side sill	open sill under cab		continuous sill, slightly narrower under cab				(1)	narrower section extended toward fuel tank, removable sill section under inverter cabinets, shorter vertical extension behind front steps, 2 additional vertical ribs on underframe (above & behind fuel tank)
Air reservoirs	strap supports		end support brackets
Dynamic brake intakes	open at bottom corners		notched bottom corners
Rear hood end bottom panels	2 latches				1 latch
Engineer's side handrail					6th stanchion from rear moved forward
Conductor's side underframe cable shroud	yes					no
Phase	1a	1b	2a1	2a2	2b1	2b2	2c	2d1	2d2	2e1	2e2	2e3	2f
Conductor's side handrail	straight (SD70ACe) or zig-zag (SD70M-2) vertical section behind inverter cabinet						zig-zag vertical section behind inverter cabinets, stanchions moved rearward
Side sill handrail stanchion supports	vertical						angled sides
Panel behind inverter cabinet	solid (SD70ACe) or square grill intake (SD70M-2)							small (SD70ACe) or large (SD70M-2) louvered section					rectangular grilled intake (SD70ACe)
Fuel system	narrow cutoff switch housing, separate gauge							wider combined gauge and cutoff switch housing					Revised fuel sensor (near bell)
Air piping								revised piping ahead of reservoirs			revised piping behind reservoirs
Small front hood panel on conductor's side	2 bolted panels								1 bolted panel, 8 bolts		1 larger bolted panel, 10 bolts
Phase	1a	1b	2a1	2a2	2b1	2b2	2c	2d1	2d2	2e1	2e2	2e3	2f
Traction motor cable shroud (SD70M-2)			yes							no
Hand brake	5-spoke or 8-spoke stamped wheel									3-spoke welded wheel, new housing		wider notch above wheel
Isolated cab seam											notch around door latch
Angled braces behind end plates	no											yes
Sand hose supports	narrow												wide
Phase	1a	1b	2a1	2a2	2b1	2b2	2c	2d1	2d2	2e1	2e2	2e3	2f

Notes

Frame and side sill, Phase 2c: Same as Phase 2b2 except narrower sill section extended rearward, farther than on later phases and without removable section.

Other details

SD70ACe units exist in all phases.
All SD70M-2 units are Phase 2a, 2e or 2f. EMDX SD70M-2 demonstrators are early Phase 2a units with some Phase 1 spotting features (air reservoir straps and no notches in dynamic brake intake).
As a DC unit, the SD70M-2 does not have inverters but retains the inverter cabinet housing found on the SD70ACe.
Trucks (HTSC or HTCR-4) vary across all phases, and sometimes vary within a single order.
Rear sand fills are either on top of the hood or in notches on the hood ends.

Dimensions

I came across a low-resolution SD70ACe general arrangement diagram online illustrating many of the frame and hood dimensions. I used these dimensions in both the 1:36 and 1:18 renditions of the SD70ACe and SD70M-2. The drawing below lists all the dimensions I used from the general arrangement diagram.

Notes:

Some dimensions have been rounded off to the nearest 0.25" (since that's the finest increment in the 1:18 drawings).
The underframe and coupler height were listed as 73.0" and 34.5" in the general arrangement diagram, based on a 43" wheel diameter. However, since I drew my 1:18 rendition of the HTCR truck with 42" wheels, those dimensions in my drawing are 72.5" and 34.0" respectively.
The specified location of the seam at the front of the hood did not line up with photos (it was off by 1.75") so I based that dimension on photos. The two altered dimensions (as used in my drawing) are listed in red.
The drawing shows an SD70ACe with HTCR trucks. The inner axle spacing is 4" shorter on the HTSC truck, leaving a 4" larger gap between the truck frame and fuel tank.
The truck centers are measured from the pivot pin, which is 15.75" outside the middle axle of each truck.