• Odd truck trivia questions

  • Discussion of General Electric locomotive technology. Current official information can be found here: www.getransportation.com.
Discussion of General Electric locomotive technology. Current official information can be found here: www.getransportation.com.

Moderators: AMTK84, MEC407

  by Allen Hazen
Something (something stupid and trivial) that I've long been curious about... The old Kalmbach Publishing "Diesel Spotter's Guide Update" has a photo (on page 5) of a switcher (off-brand, built by a locomotive company we try not to mention on this forum!) with two dissimilar trucks: one a conventional switcher truck, one a "Flexicoil." (The owning railroad had switchers with both kinds of trucks, and maintenace mix-or-matched.) Leading to the question of whether similar things ever happened with four-axle GE U or Dash-7 series locomotives.

Three different types of trucks were used with these units: the drop equalizer design used on Alcos from the 1940s on, often called "Type B" though this designation has no official status, GE's FB-2 truck introduced in the early 1970s, and the Blomberg truck (from trade-ins built by the unmentionable...). (The Alco "Hi-Ad," as on the majority of C-430, COULD have been used, and I regret that the New York Central's mechanical department never, in a spirit of experimentation, tried a truck exchange between a U30B and a C430, but apparently they never did.) Several railroads owned units with more than one type of truck, so maintenance forces COULD have been tempted....

We know the three types of truck are interchangeable, in the sense that a locomotive built with one type can be retrofitted with one of the others with no major modification of the underframe: GE, after getting a maintenance contract with Santa Fe in the ???late 1980s??? or ???1990s??? replaced the drop equalizer trucks the Santa Fe's B23-7 were built with (on at least soe units) with FB-2 (which are apparently easier to maintain. And when Conrail, desperate for locomotives early in its existence, bought the four U36B built but never delivered to Autotrain, GE, at CR's request, replaced the Blomberg trucks they originally sported with drop-equalizer trucks for uniformity with the rest of CR's 4-axle GE fleet. BUT...

QUESTION 1: is there any reason in principle (see question 3 below for a possibility) why one of these locomotives couldn't have operated with one sort of truck at one end and a different one at the other?

QUESTION 2: is there any photographic evidence that any of these locomotive ever were so re-trucked?

On a related matter... That other locomotive builder's GP-35 usually had Blomberg trucks, but some were built with drop equalizer trucks from Alco trade-ins. Apparently (going by the dimensions in drawings in a couple of 1990 issues of "Mainline Modeler") they were a half inch taller (14' 5" rail-head to roof versus 14' 4.5") with Blombergs than with drop equalizer trucks.

QUESTION 3: assuming this reflects a difference in the height of the truck center plate from the rail, is it enough to make it impossible to operate the locomotive safely with one of each kind of truck? Or could it be compensated for by putting some sort of liner in the "bowl" of the drop equalizer truck?

QUESTION 4: were GE units, like the U30B and U23B built for the Western Pacific and large numbers Seaboard Coast Line units, eqipped with Blombergs similarly a half inch taller than those with "standard" trucks? Or, when the Blomberg trucks were modified to accommodate GE's heftier traction motors, wasthe modified truck bolster that half inch lower?

(Well, I warned you that they were stupid trivia questions!)
  by JayBee
The Type B truck and the Blomberg truck were not easily interchangeable. Soo Line deeply regretted buying one of their GP35s with that type of truck and all of their GP30s also. This is one reason why they didn't last much longer than the U30Cs. The GE traction motors were strong, but the Type B trucks were not as good as the Blombergs, and the GE traction motors were oddball parts in the Soo's parts inventory, especially once the older Geeps began receiving D77B traction motors as replacements, eliminating all the older types and allowing serious reductions in inventory. The Soo Line looked twice at rebuilding the GP30s and especially the GP35, but in the end the cost of modifying the underframe outweighed the benefits and the locomotives were retired sooner than they might have been. Note that BN's GP39M rebuild program used a few cores built with Type B trucks but only once the ready supply of those built with the Blomberg trucks was exhausted.

I am not sure how easy it was to swap between the Type B and the FB-2 truck.
  by Allen Hazen
Thanks for that information! Soo Line and GE seem to have agreed, then, that the "Type B" was to be avoided when possible: cf. GE's decision about the Santa Fe B23-7 under their maintenance contract. Conrail's decision to have their four U36B retrucked with "Type B" trucks was only justified by their desire not to have to worry about eight modified Blombergs in their vast fleet!

I don't know HOW easy it was to switch between "Type B" and FB-2, only that it was occasionally done. (There may even have been a locomotive that, in its career, had all three types of truck: one of GE's U30B/U33B/U36B test set (units 301-304) was used to test FB-2 trucs before they were introduced on a production basis, and if this unit was one of the pair subsequently sold to Western Pacific, it would have got modified Blombergs as part of its final rebuilding!)
  by EDM5970
Its been some time since I did these measurements, but the centerplate on the drop equalizer Alco/GE is around 22 inches in diameter; I remember the Blomberg as being about 18 inches. Height may not play as big a factor as the centerplate diameter here. I never got a definative answer on this, but to squeeze a GE 752 motor into a Blomberg truck would have to require a special bolster, as the GE motor is a few inches larger fore and aft than the other guy's motors. Also a lot heavier, more copper-
  by Allen Hazen
Yes, I remember our previous discussion of this! My guess is that a half-inch difference in the height of the centre plate above the railhead is too trivial to worry about, but that if someone really CARED... since they were getting a new truck bolster cast ANYWAY to allow the use of the bigger and more robust traction motors, they could probably design it to be that much lower as well.
Somewhere there are probably drawings. At Erie (where GE has a standard policy of not making dimensioned drawings available, even for historical purposes), or -- if they weren't thrown out when they retired their four-axle GE units -- wherever CSX's motive power department's headquarters are.

But you're right. The "peg" on the locomotive underframe that fits into the truck centerplate has to match the centerplate diameter, so switching between modified Blombergs and the drop equalizer trucks seems problematic. ... I wonder just how much work GE had to do on the ex-Auto Train U36B before delivering them to Conrail!
  by Allen Hazen
Sorry, that was obscure. The new bolster you have to instal to modify a Blomberg truck for use with GE 752 traction motors would, it seems reasonable to suppose, be narrower than the original. Which -- I ***ASSUMED*** (always dangerous!) would make it hard to incorporate in it a centerplate of a larger diameter than the original EMD contemplate. But maybe not: maybe the top of the bolster is wide enough, but the sides are concave to accommodate the motor mountings?
  by Allen Hazen
The truck bolster moves side-to-side: you don't want the traction motor to be attached to the BOLSTER, but to the truck frame. So, modifying a Blomberg truck from an EMD trade-in would involve modifications to the frame: I hope that can be done by machining it, since otherwise the "modification" would be to cast a whole new truck frame, which has got to be the most expensive part (other, of course, than the traction motors!) of the whole assembly.

Thanks to the wonder of Google, I found a drawing of the Blomberg truck:
http://i69.photobucket.com/albums/i46/C ... alljpg.jpg

In some ways this is even more puzzling: the width of the truck bolster is constrained by the "slot" it fits into in the truck frame, and it doesn't look as if it could accommodate a wider bolster with the larger-diameter centerplate standard for GE (& Alco) locomotives.
  by EDM5970
The centerplate in the drawing of the Blomberg is about the width of the bolster; the Alco/GE centerplate overhangs on either side. With regard to attaching the motor to the bolster, it really isn't rigidly attached. The motor rides on the axle at the outboard end, which keeps the gears in alignment, on what I believe may still be friction support bearings*. (Disclaimer- I haven't really studied anything much newer than a GP-9...which is where, in my humble opinion, the guys from La Grange should have quit...). The motor has springs between it and the bolster, allowing for some motion. I suspect (won't use the 'A' word-) that the bolster used with Blombergs and 752s has those springs recessed into it .

*If the bulders are using rollers or needle bearings in their traction motor support bearings I'd like to hear about it. Maybe in the "new" AC units? (Only been around, what, 20 years or so?) But there are still lots of friction bearing locos around; those friction bearings just aren't all that visible.
  by Allen Hazen
Thanks again.
Re: "that the bolster used with Blombergs and 752s has those springs recessed into it ."
---Seems likely: it's what I was trying to get at, clumsily, when I talked (two back) about the "sides of the bolster are concave to accommodate the motor mountings."

I think the string we discussed this sort of thing on years back was on the EMD forum. A number of people made useful contributions: one was a mention that GE-- starting way back in the U25B era-- had adapter fittings for the centre pins on its locomotive frames, so the unit could ride on trucks with different diameter center plates without replacing major underbody features.
  by bogieman
The EMD bolster was not modified to fit the bigger GE motor. The transoms are hollow and about 5 inches wide. To fit the GE motor, the nose support area of the transom is cut out and a new cast piece is welded in that recesses the nose pack into the transom.

  by Allen Hazen
THANK YOU!!!! I have known for something like 40 years that the ex-EMD trucks on, e.g., SCL GE locomotives were somehow modified to accommodate the GE traction motors, but yours is the first description I have ever seen of exactly what the modifications were!
((Terminology: I take it that "transom" is the part of the cast truck frame that goes from one side-frame to the other, and that "bolster" is the part that the centre plate is on: the transom is thus fixed with respect to the side frames (it's part of a single piece of cast steel with them) whereas the bolster can move side-to-side w.r.t. the side frames. The drawing of a Blomberg truck I linked to (2 posts back) shows... would you call it a split transom or a pair of transoms?... with the bolster fitting in the middle. Is this the right way to understand the terminology?))
  by bogieman
You are correct. The bolster is the structural member between the secondary springs and the centerbearing. Hence, trucks like the GE Hi-Ad and EMD HTCR series are called "bolsterless" since the secondary springs connect directly to the underframe. The transoms are the transverse structural members of the truck frame. On the EMD GP truck (Blomberg) the bolster has wearplates welded to each side that interface to wearplates welded to the inboard sides of the center transoms to transmit the tractive and braking effort while allowing lateral and vertical vertical motion with enough free clearance to allow for some pitching of the truck frame.

  by Allen Hazen
One of Railroad.net's other forums is devoted to… the locomotive builder that employed Martin Blomberg. Michael Eby has posted there (with a link to his own site) to announce that he has compiled an illustrated account of the variants of "Blomberg" two-axle truck types. (At least four companies provided truck castings, and designs changed-- not much, but perceptibly-- over time.) If you are interested in such things, I recommend it: the string on the EMD forum has the title "EMD truck casting variations."

Anyway… I asked if he had noticed any visible (from trackside) changes to the Blomberg trucks that were re-applied to GE units. He gave a very clear and helpful reply: since he hasn't objected, I am copying his reply to my question here. (But go to the other forum for further discussion, and the link to his on-line article.)


I've looked up photos of Blomberg-equipped GE units over the years trying to find the differences, but the changes to accommodate GE traction motors are largely invisible from the outside (it would take a brightly exposed direct side view to see the changes). I'd estimate the traction motor cases extend about 2 inches farther from the axle centerlines on GE traction motors than on EMD ones, plus an additional inch or so for a slightly less compact motor suspension on the GE motors - these are estimates based on photos.

Another discussion here mentioned that only the inner transoms on the Blomberg truck frames required modification to fit the GE motors - and based on what I can see in the EMD truck diagrams, that would make sense. The bolster is nearly a foot away from the edges of the original motors and would still have lots of room left over with GE motors.

Visible differences on the GE-equipped Blombergs that I can see include the re-routed brake piping, running under (rather than over) the brake cylinders, presumably for clearance. When the clasp brakes were changed to single-shoe brakes, the brake beams were attached to the safety strap in a similar manner to modified EMD units. Most appear to have received new sand hose brackets welded onto the bottom tie bars, as well as new GE-style wheel bearings. The GE underframe would require motor air ducts that matched the truck's 9' wheelbase, which would be the same as the FB-2 truck but different from the Type B truck.
--Michael Eby
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