The Randolph, Minnesota wreck was on Christmas Day 1946. The wreck occurred at 4:40 AM when the three unit northbound demonstrator running A-B-A struck a Chicago Great Western southbound 2-10-4 head-on. The lead unit 291A2 suffered a broken underframe behind the cab. Three crewmen riding in the lead diesel were injured and evacuated for medical treatment. The trailing B unit remained upright. The trailing A unit derailed and ended up on its side. Some 20 freight cars derailed.
The above is a summary of a front page newspaper article from the Minneapolis Tribune. The Star and the Tribune were seperate papers back in the 1940s.
The automatic transition kit I developed for convering the FT’s had automatic back-transition, and so did the F3s and F2s whose circuits I studied before designing my circuit. So did the GP7s and F7s and any E7s being built at the time I was at LaGrange.
I would not doubt in any way that the E8s delivered to the PRR had backward transition, and that the removal of the four acjustable resistors and four relays was simply a penny-pinching move on the PRR during overhaul or maintenance. Can other engineers report on this with E7s, E8s, and E9s on other railroads? Lack of backward transition makes absolutely no sense to me from the standpoint of locomotive design. A high-speed train comes suddenly upon a grade and the engineer wants to hit that grade with full throttle to maintain what speed he can. So now, without backward transition, he has to return the trottle to idle, then reapply power after, if all worked well, the power-off-idle situation has returned the connections to series, and then hopefully maintain some speed, half track speed or less in sereies connection, up the mountain.
But I can underatand the PRR maintenance poeple’s thinking. With automstic backward transition, the main contactors open underfull load as the speed up the grade drops below 18 mph. This wears out contactors, although this is exactly the kind of test I performed on them at EMD. So the maintenance people thought they could prolong the life of the contactors by eliminating automatic backward transition and forcing the engnineer to shut-off and reapply power. What they did not consider is that the automatic power-off restoration to series connection might fail to work, and thus flashover. Or without backward transition, if the engineer, used to running F7s and GP7s with backward transition, did not shut off and reapply, the high currrent in parallel into DC motors will cause a flashover as speed drops.
Further thoughts: I can imagine that on some railroads reducing contactor wear is more iimportant than always maintaing speed. This might be particularly true for N&W and C&O havy coal trains. So engnineers are instructed to behave as if there is no automatic backward transmission, and, as speed starts falling when entering a grade, shut off and reapply power. But they would not remove the backward transition, but keep it to prevent motor flashhover just in case.
I doubt very much if EMD ever offered removal of backward transition as an option. But maybe somebody will prove me wrong?
And manual backward transition is available on all locomotives with automatic transition. Simply shut off power and reapply and keep the speed below 18mph or whatever.
I don’t see why my comments would not apply to Alco, GE, and FM, power as well, as all of these could be made to mu with EMD power and with each other. I don’t know about Baldwin or Lima.
And we are talking about DC-motor locomotives. Regardless of AC or DC generator. AC-motor locomotives are entirely different and do not have transition.
After thinking some more and exploring my memory, I find additional comments are in order.
18 mph is just one figure, obviously dependent on type of motor and the gear ratio. EMD power gear ratios were optional, with top rated speed up to and including 100mph for E7s and I would guess also E8s.
Two ways to implement automatic trqnsition, read off the speed recorder, with downward transition just lightly under the speed of upward transition, to avoid hunting. This requres separate circuits for upward and downward transition. I think this is what used and what was in general use at EMD 1952. I cannot be sure, because this was two-months shy of 68 years ago. The other is by measuring the ratio of the voltage acrosss the armature brushes as compared with across the in-series field coil, the latter a reasnably accurate measure of he current through the motor, and effect transition uward or downward depending on throttle setting, motor characteristics, etc. for most economical and efficient performance. I don’t think EMD had arrived at that point in 1952, but they may have before switching to AC motors. With current measuremene, downward transition would not be a separable circuit from upward transition.
My assuming PRR’s maintenance and overhaul people were stupid enough to remove downward transition was probably a mistake. Granted, EMD would not have sold a locomotive without downward transition. But PRR’s mistake was putting 100mph E8s into freight service without regearing. Recall that 90mph GG1s saw both freight and passenger service, but 100mph saw only passenger service except for very rare and controlled circumstances. The downward transition point for the E8 was probably not suitable for extended low-speed operation, with motor-heating from maximum current for extended periods. So it seemed like there was no automatic backward transition, because it did not occur soon enough
Just as every EMD unit has an order number and a serial number, each diesel engine block installed in a unit has a number. These block numbers are recorded in the EMD Product Data, presumably for maintenance purposes.
EMD began manufacturing 16-567B blocks in 1945. The F2 demonstrators were completed in May of that year and released for test on July 31, 1945. There would have been a 16-567B installed in each of the four #291 demonstrators, plus another block or two for test purposes. Continued 16-567B production may have occurred later in 1945 up to the point where a strike shut down EMD in November. There is a bit of information that backs this up.
At the very end of FT production there were orders completed for 12 Great Northern and 12 Rock Island units. No other F units, that we know of, were produced until July 1946.
Now about those pesky block numbers. When EMD started F2 production, presumably in July 1946, there were nine maybe ten block numbers that point to a 1945 manufacture date. Three are within the number range of the Rock Island 16-567A blocks installed in FTs and six are just after. One block of a July 1946 produced F2A is not known at this time because a mid-1948 production 16-567B was installed at a later date. There were 43 F2As built with a July 1946 production date. In numerical sequence from oldest 16-567B block installed in nine F2As is: Rock Island 39, Rock Island 49, Burlington 152A, New York Central 1604, Alabama Great Southern (Southern) 6700, Burlington 150A, Atlantic & East Coast 401, Rock Island 38, and Rock Island 46. The July 1946 F2A with the unknown block installed is Atlantic & East Coast 400 which shows as a block built in the Summer of 1948, which would obviously be a transplant. The remaining F2A production for July 1946 have 16-567Bs that fall within numbers that mirror other 1946 engine production. You can draw your own conclusions if these block numbers mean anything.
Considering that the the motors on the E’s were physically smaller than the motors on the F’s, not regearing was a double whammy. Regearing would have improved matters, but still wouldn’t have made it the equivalent of an F.
The E units had about 50% more HP than the F units, but they still had the same number of motors/powered axles (4). Why did both types use the same motors?
I stand corrected… My understanding had been that the trucks on the E’s had 36" wheels versus the 40" wheels on the F’s, GP’s and SD’s and thus needed a smalller traction motor. Now something like a GE-750 traction motor…
Any idea when EMD started using Kapton insulation on theor motors?
The same motor for all power reduced development, manufacturing, inventory, and railroad maintenanc costs, and was an EMD rademark from the E6-FT-era on. The motor was designed with the current capacity for drag-freight service, assuming low-medium-speed gearing, and the insulation for voltages in all operations, again with the right gearing chosen for the application. The same basic design was improved over the years with better insulation, more advanced metalurgy steels for pole pieces, better carbon compound fpr brushes, etc. The basic motor design lasted right up to AC motors.
Possibly, the same is true of their AC motors, today. (No brushes, of course)
Before the FT and E-5 and E-6. I believe EMC-EMD used GE and Westinghouse motors. Also, I believe the latest DC EMD motor couild be used as a direct replacement for the first DC EMD motor.