EMD Locomotives with Trade In Alco Trucks

The GP30's were built with a J1 relay and the Brake cylinder pressure was 45 pounds. The trucks from the Alco trade-ins had a larger brake cylinder and the leverage arrangement was more efficient than was the standard EMD Blomberg truck. This caused no problems with other EMD 4-whl trucks. HOWEVER, when the SD40's arrived they came with a J1.16 relay valve and they operated with 72 pounds of air to the brake cylinder. (Because the SD's had composition shoes, they needed higher brake cylinder pressure.) So when the 30's were operating as trailing units with SD40's, they were being supplied with 72 lbs. of air to the brake cylinder, the combined with the larger brake cylinders and the more efficient brake lever arrangement created flat spots that were beyond belief. They had to be modified to run with composition shoes and a J46 relay valve.

As for the old wheels coming back, depending on how EMD felt, options could be extremely expensive, if EMD did not want to do something. Another thing to remember, MEchanical departments did not always have the last word on what would and would not be purchased from EMD. (Every company has their 'beancounters.')

RdHseRat wrote: So when the 30's were operating as trailing units with SD40's, they were being supplied with 72 lbs. of air to the brake cylinder

Not to be abrupt here, but actually, no. The type relay valve on the leader has nothing to do with the cylinder pressure on trailing units. Application and release MU pipe carries the 45 pounds of pressure from the independent brake valve throughout the consist. This pressure acts as control pressure and does not actually go into any cylinders. Cylinder pressure on any particular trailing unit is determined by the relay valve on that unit. If it has a J1, that would be 45 psi max (or whatever the independent brake valve on the leader is adjusted to).

At the same time, it supplies the J1.6-16 relay with 45 lbs that is stepped up to 72 (or 160% due to the 160% diaphragm area)for only the cylinders on the unit that has that valve type in its system.

The pressure in the cylinders on any unit comes through the relay valve from #2 main reservoir -- thus making the cylinder pressure the same no matter what the piston travel (cylinder volume) may be.

LCJ

Sorry to tell you are very wrong! Was there and saw this problem first hand. The only solution was changing the J valves. WABCO understood the problem, to bad you don't!

Actually I beleive LCJ is right,

http://www.railway-technical.com/us-musp.html

We run all six axle power at 72psi in the brake cylinder, the four axle power any where from 27 to 33 pounds. When the six axle and four axle units are mu'ed together each units brake cylinders set up to what ever pressure the brake valve is set for. You can actually adjust it with your mainline switch key by turning the screw on the back of the brake valve, and adjusting the lead units pressure has no effect on the trailing units pressure. If this were not the case we would skid the hell out of all the four axle power. Not exactly sure, but I think the reason for the higher pressure on the six axle power is because they have one brake shoe per wheel, where as the 4 axle (EMD) have two.

LCJ is most definately right. I was lucky enough to have Larry as my air brake instructor, on Conrail, and the air brake room had several versions of locomotive and car A/B systems, with strategically placed air guages, to show/prove exactlly what he stated. The "trainlined" air pressure, in the application pipe is sent at the 45 pound pressure, throughout the consist. The independant operating control valves, or the J1, and the J1.6-16 valves are what determines the amount of pressure, supplied to brake cylinders, from a main reservoir air supply. (same way BP pressure is supplied to the trainline, through a "relay" valve, not the actual pressures being created in the controlling air system. Even today, we run mixed consists, with both HF composition, and cast iron shoes, on various locos, with no problems of sliding wheels. Those cast shoes will grab harder, at lower speeds, but the locos dont slide, or get flat-spotted, on their own, without help from the application of the automatic trainlined brakes, which will actually increase the pressure, on those locos, to about 62 pounds, if a suppression/application, is not applied. We dont slide/flatten the locos, when switching, running, etc., with full application of the independant often being suddenly, and fully applied, to a moving train. I have witnessed the wrong independant brake valve applied, to a switcher, from a road loco, with the result being hurled from the seat, and plastered against the windshield, and even then, the wheels didn't slide. Although the valves are adjustable (sometimes) from the seat, I believe the internal diaghrams are different, based on the intended operating pressure, of the valve in question. (LCJ ?) Not sure what valves you guys changed out, or why, but rest assured, LCJ has the right stuff, regarding loco A/B systems, as well as most other loco stuff, as well. I don't say this, lightly, I deferred many a question, over the years, to LCJ and the staff of CR Conway ETP. All of those guys were (are ?) members of the WABCO airbrake club. Regards

Also Somewhere, on some rail history FAQ, there ***ought*** to be a graph, or maybe just some sample prices, to show how locomotive prices have gone up over the decades!

It seems since the mid 60s the price of a new locomotive has been about $2 million (isn't that what a new one costs?). A new 1966 AC-DC C-C locomotive would cost just about $2 million (almost $300K then). But until then the price for a new unit started low and grew higher:
1952: AS616, RSD5, SD7: $1.3 million
1960: RSD12, SD24: $1.4 million
1964: C-628, SD35 (?), U28C: $1.5-6 million
1966: C-630, SD40, U30C: $1.7-9 million

Also of note, sometime in later production, the GSC switcher and road trucks used under Alco units (specifically confirmed RS-11, T-6) no longer featured the GSC logo cast onto them, rather, "ALCO TRUCK" was stamped on the center. However, their HiAd trucks did have the GSC logo. In Canada, the 'swing bolster' trucks were manufactured by DoFASCo.

Just adding a note here, primarily for Allen and anyone else on the forum who keeps track of specification numbers. If the normal EMD Sales Engineering specification number assignment scheme was applied to the GP30 units where an ALCO was traded in, then the combined sales specification and trade in amendment for these GP30's would be #8046-5.

As threatened, I remeasured the centerplates on both a Blomberg and a GSC swing bolster truck yesterday. The Blomberg was 18 inches in diameter, and the GSC was 22 inches. The GSC truck's centerplate overhung the bolster fore and aft by a few inches.

I also made another quick measurement, the distance between the centerline of the journalbox opening and the crossmember, up against the bolster, that would limit the size of the motor (sorry I don't have a better name here). I was alone and had to eyeball the centerline of the journalbox opening, but the EMD had about three inches less space. The GSC truck measured 41 inches to the EMD truck's 38. Those 752s ARE larger, no doubt about it.

Another interesting thing about trucks that hasn't come up in this thread is the Geeps (and RSs) on switcher trucks. The U.S Army and L&N (NC&StL?) had GP-7s on switcher trucks; I believe the some of the Army units wound up on the Alaska. And MILW traded in some GSC swing bolster trucks to either EMD or Alco for use on new units; the donor RS-2s wound up with old Alco switcher trucks, possibly even Blunts.

EDM5970--
Thanks for the measurement!
Switcher trucks ... bring up further questions! Alco offered the C415 on switcher trucks (only Hi-Ad and the ... "Commonwealth"? ... truck were actually used). And they built a T-6 with Hi-Ad trucks (switcher trucks standard). I don't know, however, if this involved changes to the center-pin etc on the locomotive body.
Another problematic case: Rock Island wanted to trade in the trucks on its FA-1 to GE for use on new U25B. but had just had the FA-1 re-engined with EMD engines so they were too "new" to trade in. They gave GE some old FT units and the "Commonwealth" trucks from the FA-1, and remounted the FA-1 on the Blombergs from the FT. Maybe THAT's why GE advertised an adapter/filler piece for centerplates? (cf. H.F. Malone's post of a while back)

Florida Gulf Coast RR Museum has two of the Army Geeps with switcher trucks. One of them is operable, and painted in "civilian" colors (L&N, I think?)

JR

http://www.frrm.org/gallery/

FYI a recent Trains article covered Ann Arbor railraod geep35's with Alco FA trade in trucks. It was an informative article, although I don't remember much.