• Are PA trucks the same as on the DL109

  • Discussion of products from the American Locomotive Company. A web site with current Alco 251 information can be found here: Fairbanks-Morse/Alco 251.
Discussion of products from the American Locomotive Company. A web site with current Alco 251 information can be found here: Fairbanks-Morse/Alco 251.

Moderator: Alcoman

  by trainman6555
I wonder if when the PA was made, the same long wheelbase trucks were utilised as on the DL109. I also wonder who made the trucks as they were apparently found on some FM locos too e.g CPA24-5, Erie builts. This would surely make maintenance easier if all these trucks were interchangable. I am sure I will be corrected!
  by Allen Hazen
Interchangeable? Are you suggesting the railroads should STANDARDIZE? ... It might have been a good idea, but the corporate/industry culture of the time didn't go that way.

The A1A trucks used on the Dl-109 and the PA (and also those on Baldwin's 2000 hp passenger locomotives) are very similar in design, but not quite identical: the PA's truck has 2" longer wheelbase than the Dl-109's. (I have read that this is connected with Alco-GE's decision to offer 42" wheels as an option on the PA instead of the usual 40".)

The rear trucks on 5-axle FM trucks and the cast-frame trucks used under Erie-builts are similar (similar enough that Doyle McCormack is using trucks from scrapped Erie-builts in restoring a PA), but slightly different: the top of the truck frame is a flat horizontal instead of the slightly inclined angle of the PA and Dl-109 frames. I have no idea why.

I'm not sure who made these trucks: truck frames are large castings that the locomotive builders bought from outside suppliers. Commonwealth Steel Castings was one supplier, but I don't know if it provided the castings for some or all of these locomotives.

(Note that even identical-looking trucks may not be exactly the same. Apparently -- this from Preston Cook's articles in "Railfan & Railroad" -- later models of EMD E-units were heavier than the earlier, and had somewhat beefed up truck frames to cope.)
  by Super Seis
This subject has been beaten to dust !!!

The trucks used under the FM passenger (actually dual-service) units built by GE are a completely different casting than those found under either pre or postwar Alco 2000 hp passenger units.

Reason ? The FM's used a GE 746 motor, whose design was borrowed from an earlier order of GN electrics. This motor was MUCH larger than the 726 (later 752) used on the Alcos. Recall that GE designed and built a fabricated truck for these FM units that would fit the 746 motor.

The truck used ujnder the B-end of the FM C-liner was yet another design, as the WEMCO traction motors were (once again) a different size than either the
726 or 746.

Yes, GSC poured all three varieties of casting.

The PA's used a 42" wheel (larger contact patch), for the DL-109 was slippery with 40's-despite its greater weight.

  by trainman6555
I appreciate the information, Thanks for your time.

Heres how the question arose:
I have a True Line Trains HO scale model of a CPA24-5 and my pal said the rear truck was the same as his Alco PA. I emailed True Line to ask, and recieved the reply that they had used the DL109 truck on the model.
I suppose from your replies, commercially it made sense to utilise a similar truck than manufacturing the correct truck.
Yours from England,
  by Allen Hazen
Super Seis--
The subject has been beaten, but I'm not sure we've heard the end of it yet! There was a long string (I hope still in this forum's archive) on "PA-1 Traction Motor Question". Note that at least some early PA-1 were apparently built with the big 746 motor, and that Doykle McCormack hopes to operate his PA-1 on Erie-built trucks with (I would assume) 752 motors(*): so even if the motors are not the same size, it is apparently possible to adapt the trucks to use either. (It may involve modifications to the bolster: I don't know.) ... Thanks for the confirmation that GSC did castings for all three truck variants!
(*) For that matter, Canadian National's C16-5 had hind trucks which, at least visually, seem to be like those on the Erie-builts, but with 752 motors.

From a modeling point of view, the two inches difference in wheelbase between a Dl-109's trucks and the others is hardly going to be visible in HO scale. The difference in shape of the truck frame between the post-WW II Alco and FM units is visible (look up the relevant railroad's locomotives on George Elwood's "Fallen Flags" rail picture site
but subtle: only the most fanatical rivet-counters will notice!