A1A truck compatibility question

The A1A trucks used under the PA series weren't QUITE the same as those used under the Dl-100 series, but they were similar: the wheelbase of the PA truck was only two inches greater than that of the Dl-100 truck. And I think the 726 traction motor (used under the majority of Dl-100 units built) probably had the same dimensions as the 752, so probably the motors could be switched between the two types of truck. In principle, would it have been possible switch trucks between a PA and a Dl-10x? Or is there some unobvious difference which would have made them incompatible?

And-- assuming it was possible-- did any railroad (in particular, one which had sizeable fleets of both locomotive types and limited cash to pay for spares…) ever in fact switch trucks between the two types of locomotive in the course of maintenance?

(Cross posted to the Alco forum.)

Same basic dimensions + same or similar traction motors + same electrical connections = no problem at all.

The Virginian Railroad occasionally swapped trucks between their General Electric EL-C electrics and their Fairbanks-Morse H-24-66 diesel-electrics. The rules spelled out in the first sentence applied.

Was it ever done? Impossible to say. Maybe, maybe not.

0700 - 0759 Top speed 80 MPH.
0760 - 0786 Top speed 90 MPH.
I suspect the 0700 - 0759 were geared for lower top speed to improve their performance on freight trains which they were used on plenty in their earlier years. That would mean a no on a swap of trucks.
Noel Weaver

Noel--
Thanks! Do you happen to know the minimum continuous speed and/or continuous tractive effort of the two classes? 700-759 had 726 traction motors, whereas 760-786 had 752 motors: enough more robust that they may have had equivalent low speed performance despite the higher speed gearing!

Well, I tried looking up the stats on both - not so easy a job.

DL-109: 2,000 h.p., 337,000 lbs. in weight, 56,250 lbs. tractive effort, 2 M&S 539T 6-cyl. engines, 2 GE GT-557 generators, 4 GE 726 traction motors.

PA-1: 2,000 h.p., 306,000 lbs. in weight, 51,000 lbs. tractive effort, 1 Alco 244 16-cyl. engine, 1 GE (model?) generator, 4 GE 752 traction motors.

The DL-109 was both heavier and geared for slower speed, and would thus grab the rails a bit more for heavy service. The GE 752 traction motor was a beefier version of their 726 traction motor, but how much of a difference in torque it would provide is a good question. I don't have an answer for that one.

Apparently comparing the two, even though somewhat similar, is not easy. Lots of things have to be factored in: Wheel diameter, traction motor used, gearing ratio used, generator output, diesel engine rack settings, and probably one or two other things, too. And, to a limited degree, who is operating the throttle (yes, the human factor does come into play).

Bottom line? Well, the DL-109s did well for what they were built for, for the timeframe when they were used. Likewise, the PA-1s, when properly maintained, did well for what they were built for, for the timeframe when they were used. The DL-109s were specifically built for dual-service usage; the PA-1s were not.

Statkowski!
Wow! You are right, that sort of information ISN'T easy to find. Thank you very much!
For curiosity, could you tell me where you did find the figures? (Some New Haven Railroad document?) And, if your source has it, what speeds the quoted tractive efforts were at? and what the gear ratios for the traction motors were? (This is relevant to something I've been curious about for a long time: see the "PA-1Traction Motor Question" string at the Alco forum.)

I think it was Wikipedia, for what it's worth. I just entered "DL-109 specs" and "PA-1 specs" in my search engine and went with what I got (with a lot of copying to paper). There are several sources, when those entries pop up, and all one can do is compare what provides the data required. Something did pop up from I believe the Railroad.Net forum, but couldn't say exactly where on the forum it popped up.

I even tried looking up the data in my 1973 copy of The Second Diesel Spotter's Guide.

Statkowski--
O.k., publicly available sources! (Grin)
I've been very slow in figuring something out. The tractive effort numbers you quote have NOTHING to do with the traction motors or gear ratios: they are the (nominal) starting tractive effort, which was conventionally given as exactly 1/4 of the weight on drivers for first generation diesels. (So: tractive effort on starting from a dead stop, calculated -- optimistically, I suspect -- at 25% adhesion.)

The continuos tractive effort is the tractive effort the locomotive can give for more than a limited amount of time without over-heating the traction motors. For a PA-1 with 90m.p.h. gearing (62/21 gear ratio) I think that would be 30,500 pounds at 20m.p.h. Change the gear ratio to give a maximum speed of 80m.p.h. (the Pennsylvania Railroad did this to their PA-1 locomotives when they decided to make them dual service units) and it goes to 35,000 pounds at 17.5 m.p.h. Since the horsepower is the same (nominally: I'm not sure the 539T and 244 engines actually attained the same fraction of their nominal horsepower) but the 726 traction motor is less robust than the 752, I suspect that the continuous tractive effort and continuous speed for a New Haven Dl-109 would be somewhat less than 35,000 pounds at somewhat more than 17.5 m.p.h., but I don't know how much less or how much more. … At the end of their lives, the New Haven used its PA-1 on freights (after train-offs had reduced the number of passenger trains and the FL-9 had taken over some of the load): I suspect, but don't know for sure, that the better traction motors would have given the 90m.p.h. PA-1 close to the same low-speed performance as an 80m.p.h. Dl-109.
(And -- having used it as my "bible" on diesel locomotive matters for several years -- the 1973 "Second Diesel Spotter's Guide" is a bit disappointing when it comes to this sort of technical detail. (Grin!))

By the time the New Haven used PA-1 in freight service (and I do remember seeing them like that), they were happy to have any available engines for freight service. Once the ex-Virginian electrics came on the scene, that was it for the PA-1s.

Based on entries in Arranged Freight Service Symbol Book No. 14, dated Oct. 28, 1962, a PA-1's tonnage rating was approximately 80% of the tonnage rating for a GP9, RS-11 or H-16-44 (the new kids on the block). No tonnage ratings were shown for the uphill/downhill Maybrook Line, so I'd imagine they were kept to the less hilly but more curvy Shore Line.

Statkowski--
"Assigned Freight Services Symbol Book #14": That's a LOT more impressive than Wikipedia! And not something that I have any access to: thank you VERY MUCH!
Tonnage rating about 80% that of a GP-9, RS-11 or H16-44: that's a useful piece of information: I'll think about it and see if it suggests anything interesting. The RS-11 and H16-44 would have had GE 752 traction motors, but a later model (752E rather than 754A or 752B) with a higher rating than the 752 motors on a PA-1.
Had the Dl-109 been retired by the time AFSS Book 14 was issued, or do you have any tonnage ratings for a Dl-109?

Thanks again: sharing information is one of the things the Railroad.net Forums are for!

By 1962 the only DL-109 left on the property was PP716, which had no traction motors.

Here's some of the comparisons between PA-1s and GP9s/RS11s/H-16-44s:

Boston to Brayton Ave.: DERS-4/5/6 - 1700 tons; DER-3 - 1400 tons
Brayton Ave. to New Haven: DERS-4/5/6 - 2200 tons; DER-3 - 1800 tons
New Haven to Harlem River: DERS-4/5/6 - 2500 tons; DER-3 - 2000 tons

However, in the Sept. 27, 1953 Engine Assignment Book, which also includes tonnage ratings for selected routes, Class DER-1 (Alco DL-109), DER-3 (Alco PA-1), and DER-4 (FM CPA-24-5) all have the same tonnage ratings, which are, in some cases, considerably less than those shown for the Alco FA/FB-1s or Alco RS-3s in the westward Maybrook Line run.

Statkowski--
Thanks again!
No surprise that the FA/FB-1 and RS-3 have higher tonnage ratings than the Dl-109 and other passenger locomotives: they were geared for a top speed of 65m.p.h., meaning that, at any given speed, their traction motors would be rotating at the speed the passenger units' motors attained at a significantly higher speed. So they could safely get down and lug heavy freights at a speed which would have the passenger units' traction motors overheating. I think an FA-1's continuos speed was something under 15 m.p.h., and at that speed it could exert over 40,000 lbs tractive force. (I'll check tomorrow and post the exact figures… which I think are in some post to the "PA-1 traction motors" string on the Alco forum.) The 90m.p.h.-geared PA-1 couldn't safely operate (for more than a short time) under 20m.p.h. (I'm guessing that speeds would have dropped below this for the hilly run over the Lichfield hills from Danbury to Poughkeepsie A LOT), and its continuous tractive effort is only three quarters as much.

That the PA-1 and Dl-109 were given the same tonnage ratings confirms what I suspected: the PA-1's more robust traction motors compensated for its higher-speed gearing when it was put in freight service. … Do you know what top speed the New Haven's CPA-24-5 were geared for? They would have had Westinghouse motors, which had a good reputation, but since they were bought for the same passenger service as the PA-1, I'd guess they were also geared for something around 90m.p.h.

Authority: Time Table No. 8 effective July 26, 1959.

General Speed Restrictions (page 58)

DERS-1b class engines 0660-0671 series (Alco RS-1) - 60 m.p.h.
DER-1 class engines 0700-0758 series (Alco DL-109), DERS-2c class engines 517-561 series (Alco RS-3), DERS-3 class engines 590-599 series (FM H-16-44), DERS-4 class engines 1200-1229 series (EMD GP9), DERS-5 class engines 1400-1414 series (Alco RS-11), DERS-6 class engines 1600-1614 series (FM H-16-44) - 80 m.p.h.
DER-3 class engines 0760-0786 series (Alco PA-1), DER-4 class engines 790-799 series (FM CPA-24-5), EDER-5 class engines 2000-2059 series (EMD FL9), Daniel Webster; John Quincy Adams; R.D.C. (Budd) - 90 m.p.h.

Couple of points: traction motor "gearing" is a matter of changing the pinion gear on the motor. The same 752-series motor could be re-geared for different speeds (MEC did this on some E7s, I recall). The NH did not make the effort (labor and shop time costs) to do so with the PAs, but simply put them out there and used them.
But, changing gearing from passenger to freight is not too difficult.

Also, truck interchange-ability is dependent on center plate diameter and arrangement. For example, the common drop-equalizer two-axle GSC road truck (aka "AAR B") has been supplied with 18" and 21" dia center plates. There were adapter rings to use the large dia truck on a small dia body center plate.

Did the New Haven PAs really have 752 motors? I ask because I have a copy of Jack Swanberg's New Haven Power. It had a chapter about the 0500/500 classes of RS2 and 3. It said that the 2s had 65 mph gearing, while the 3s had 80 mph. The TE was about the same because the 3s had newer and better motors. This is why I ask if there is really a parallel, since the PA and RS 2 were both from the mid to late 1940s.