Now, if you were to bring up the space available between the flange and some parts of the bolster structure between the wheels, you might have a more cogent argument; in fact, without looking at a dimensioned drawing I’d easily accept the argument that this is a controlling dimension for diameter increase. But the situation, even with those funky short-wheelbase Flexicoil clones, have the wheels far further apart than ‘interference’ distance (as in most steam-locomotive rigid wheelbases)
[quote]
I suspect the traction motors are configured to occupy the space between the powered and unpowered axles on the truck.[/quotwithoute]
Remember that the motor is explicitly designed to fit between the gearcase and the back of the opposite wheel, and that there are strong reasons to keep the parts list as common as possible between different EMD units. It is not likely that a motor design accommodating 40" wheels on Fs would have its case, connections, nose-suspension arrangement etc. artificially widened when applied in passenger applications. I think I always assumed the 36" wheels had something to do with keeping drawbar height low to match passenger cars, as there’s a long history favoring larger wheels for high speed as well as extended wear.
The number of the ‘various gears’ being exactly two, and their width in the gearcase essentially standardized across the range of possible ratios. What there is to be ’
Yes, and I think the 40" wheels were retained on the ten FL9AC ‘starship’ rebuilds.
For standard service in this frame, yes. The Flexicoil was used because the original location for the third-rail shoes was on a long beam on the rear truck; the front truck on the 2 prototypes being like a standard swing-hanger B truck. That turned out to be a relatively crappy place for the third-rail shoe, so the front truck became a modified Flexicoil with a shoe beam installed.
There were North American locomotives with A-1-A Flexicoils, notable the GMD1, but to my knowledge those trucks were shorter wheelbase and had a smaller-diameter wheelset in the central position…
Going back, for a moment, to transition: I do recall seeing manual transition once in my B&M days, on the “gas-car” or doodlebug, proably re-engined with a diesel, running Manchester, NH - Portsmouth, ME, which I rode, standing next to the engineer much of the way, Nashua - Portsmouth. Forward transition required shutting off power, pushing a button or a switch, and reapplying power one step at a time but quickly. Downward transition, the one or two times I saw it, was simply shutting off power, waiting and then re-applying power one step at a time but more slowly. Did any reader actually operate FTs or other diesels with manual transmission, and was the operation simiar?
The FL9 used a Flexicoil truck of the same design developed for the SD7, modified to mount the shoe beams. The front truck was similar to the Flexible switcher truck.
The GMD1 used the export A-1-A truck I mentioned above which uses 40" driving wheels and 33" idler wheels. The idler axle springing is adjusted to provide the maximum axle load allowed on the driving axles with the remainder, as low as 10Klbs., on the idler axle depending on loco weight. This design has no brakes on the idler axle.
We also sold export locos with the GC truck, a lightweight flexicoil design in either A-1-A and C configurations. This truck was first used on the G16 for India, I believe, and also on the Milwaukee SDL39.
What OM is referring to are the swing hangers on each side of the idler wheelset, with the swing hangers placed closer to the center wheelset than the outer wheelsets. The presence of the swing hangers and the center axle clasp brakes put a limit on the diameter of the center wheels.
To my knowledge everything in the somewhat-convoluted series from DL-103 to DL-110 had 40" wheels. The New Haven used GE 726 traction motors and had a nominal “120mph” on these wheels with 25:58 gearing (I list this pinion-first for tooth ratio as I recall PRR did, as it makes a little more sense to me; just reverse it for normal convention).
The ATSF used 21:62 in their DL-107s (nominal 100mph) with 726s, and this combination apparently didn’t get over Raton successfully, leading apparently to much solder on the ties and exasperated comments about ‘street car motors’.
This problem was addressed nicely in the DL-304/305 by going to larger-frame GE746-A2 motors (and in the MK rebuilds full 752s) which I recall being told was the reason for the 42" wheels. Oddly these were still rated as “100mph” with the same nominal gear ratio as the DL-107s (21:62) with the larger wheels.
Now, if you were to bring up the space available between the flange and some parts of the bolster structure between the wheels, you might have a more cogent argument; in fact, without looking at a dimensioned drawing I’d easily accept the argument that this is a controlling dimension for diameter increase. But the situation, even with those funky short-wheelbase Flexicoil clones, have the wheels far further apart than ‘interference’ distance (as in most steam-locomotive rigid wheelbases)
Remember that the motor is explicitly designed to fit between the gearcase and the back of the opposite wheel, and that there are strong reasons to keep the parts list as common as possible between different EMD units. It is not likely that a motor design accommodating 40" wheels on Fs would have its case, connections, nose-suspension arrangement etc. artificially widened when applied in passenger applications. I think I always assumed the 36" wheels had something to do with keeping drawbar height low to match passenger cars, as there’s a long history favoring larger wheels for high speed as well as extended wear.
The number of the ‘various gears’ being exactly two, and their width in the gearcase essentially standardized across the range of possible ratios. What there is to be ‘tricky’ is the stuff I already described; the practical ratios being constrained on the one hand by stress in the pinion (Mr. Goding’s note on hoop stress being comparable to what Sam Vauclain noted as the reason 26" ws the shortest practical stroke on the PRR T1s) and on the other by needing an integral number of carefully-formed and adequately-rooted teeth on each of the gears in a mating set.
Note that increasing the gearcase length even by 2" (to accommodate a hypothetical radius change of that size in going from 36" to 40") would alm
Santa Fe’s DL107/108 set was built with GE 730 traction motors installed on 41" wheels with 56:25 gearing in May 1941. Those are the motors that failed on Raton. The units were remotored with GE 726 traction motors toward the end of WW2 and 40" wheels were installed.
This gets more and more interesting – point me at a good tech reference. I had the impression that the 730s were recommended for passenger service and 726s for freight, but the dieselshop reference only mentioned 726s for the DL-107 stats (on what could be presumed, on ATSF, to be decidedly fast passenger service), so I was suckered in. (Presumably this was the as-rebuilt configuration – are they also correct in their given gear ratio for the 40" wheels?)
Larry Brasher (Jr.) is not very positive in his recounting of that trip west. He describes the idle of those four motors as being so rough that the sides of the units were visibly flexing, and coffee was being sloshed in the buffet through the tightlock couplers. I wonder what other issues were observed in service.
Apparently, I was in error on the very last DC motors. What about AC motors today? Are there varieties or just one for EMD-Progress Rail? Should be possible to do the job with just one type.
EMD has used 3 different motor diameters and several core lengths. The first is the Siemens 1TB2630 which was used in the SD70MAC, designed to take up the space between a gearcase and the opposite wheel in a standard gauge application. Variations of this same diameter were the 1TB2626 as used in the F69PH-AC and the 1TB2624 used in the LIRR DE/DM30AC’s. This diameter was also used in the locos for India but I can’t recall the length. The first two digits denote the diameter and the second two the core length but it’s not any particular units like inches. These motors are designed for 42" minimum new wheels with 1.5" radial wear material (fully worn at 39").
The second size is a bigger diameter as used in the SD80 and 90MAC’s, that was also a Siemens designed motor designated 1TB2830 roughly 3" larger in diameter IIRC. This is the only application of this motor size, which requires at least 44" dia new wheels. The bigger motor motor was needed to meet the design requirement of 200Klbs. tractive effort.
With the split from Siemens to using Mitsubishi inverters starting with the SD70ACe, EMD designed in house a new series of AC motors with diameter between the two Siemens motors to have capacity for 200Klbs. TE with 6 motors. This family of motors is designated A29XX and requires 42" new wheels. It’s now used on all EMD/Progress Rail locos in widths to fit from meter to standard gauge, wider than standard u
The young writer of this paragraph was born in Georgia, but moved to Louisville, Kentucky while he was young. He grew up in Louisville and joined the Army while World War 2 was winding down. Returning to the States he moved to Texas where he was writing for a local newspaper when Al Kalmbach offered him an associate editor job at Trains Magazine. David P. Morgan began working for Trains in June 1948 when he was 21 years old. The Age of the F-3 was a sidebar to his April 1949 article “The Shift from Steam”. According to Morgan the F-3 was born in Oc