Blomberg trucks

[Flint Hills Tex]

I've been a rail fan since I was a kid, but I just don't know what Blomberg Trucks are. How do they differ from other trucks? Why did so many RRs insist on rebuilt Blombergs on otherwise new power?

[silicon212]

The 'Blomberg' is the old venerable GP Swinghanger truck that you see under 4-axle EMD locomotives such as the old Covered Wagons (F series), GP7, GP40-2, etc.

They provide a very good ride quality, much more so than other competing trucks.

[YoHo1975]

Here, I'll illustrate

This GP38-2 is sporting Bloomberg M trucks. Note the shock absorber

 

This Santa Fe F3 is sporting Bloomberg B style trucks. Note no Shock absorber and bigger leaf springs

 

 

And Finally, this Frisco E8 is sporting Bloomberg A1A trucks

I gotta go now, when I get back, I'll post pictures of the alternatives.

 

[SSW9389]

And Blomberg trucks were the patented invention of Martin P. Blomberg who started working for EMC in 1935. See http://en.wikipedia.org/wiki/Martin_P_Blomberg for a brief biography.

[tdmidget]

That is NOT a "shock absorber". Take a look at Koni's ads in trains. It is a spring damper. Shock is absorbed by springs. This device stops the spring from continuing to vibrate like a guitar string. The larger leaf springs don't need it because the internal friction of the leaves tends to make them self damping.

[oltmannd]

That is NOT a "shock absorber". Take a look at Koni's ads in trains. It is a spring damper. Shock is absorbed by springs. This device stops the spring from continuing to vibrate like a guitar string. The larger leaf springs don't need it because the internal friction of the leaves tends to make them self damping.

I think you are playing a semantics game......

Those devices on our automobiles that are actually viscous "spring dampers"... we all know them as "shock absorbers."

And, since we feel the need to nit-pick, you need to tell the whole story of why the the Blomberg M truck has "shock absorbers."

The original Blomber truck had stiff, coil spring primaries and soft, leaf spring secondaries.  The "M" version, has soft, coil spring primaries and stiff rubber secondaries.

Since more of the vertical motion takes place in the primaries in on the M truck, and coil springs have lousy internal damping, the primaries need external damping.  On the original Blomberg, most of the vertical motion occurs over the secondaries and leaf springs have decent internal friction damping (the leaves rub against each other). 

Rubber pads have superb internal damping.

[WSOR 3801]

And just to confuse the matter, here is a GP60 with leaf springs and the dampening struts.

http://www.rrpicturearchives.net/showPicture.aspx?id=83948

The Blomberg-Ms with the rubber springs ride pretty poorly, vibrate the cab a lot, etc.  It looks like for the 60 Series they went back to the leaf springs, and added a horizontal dampening strut as well, only on the engineer's side. 

[Flint Hills Tex]

I still don't get why RRs would want rebuilt trucks as opposed to new ones on an otherwise new locomotive. I read that many RRs even ordered GE U-Boats with rebuilt Blombergs. Weren't they first generation diesel technology? So why re-use them on second generation locos?

[ArtOfRuin]

When many railroads retired their first-generation units (i.e. F-units, early Geeps, etc.) they didn't just scrap all of them; the RRs would trade some of them them in for new units. Often, to keep costs down, the new loco builder (in this case GE) would reuse whatever they could from the traded in unit on the new loco. In this case, GE would salvage the Blomberg trucks from, say, an F-unit to put onto a new U18B. EMD did the same thing: some of their second-generation Geeps like the GP30 and GP35 used AAR type-B trucks from traded in ALCo RS-units. It could also be railroad-preference, as well.

[J. Edgar]

I still don't get why RRs would want rebuilt trucks as opposed to new ones on an otherwise new locomotive. I read that many RRs even ordered GE U-Boats with rebuilt Blombergs. Weren't they first generation diesel technology? So why re-use them on second generation locos?

it was more a cost thing ....the Ann Arbor RR in Michigan traded in ALCo FA's on new GP-35's and got a discount for re-using the ALCo trucks....realy replacing the traction motors and maybe springs and brake parts trucks will last forever

[YoHo1975]

Also, the AAR style trucks road pourly compared to bloombergs.

 

Railroads such as Western Pacific wanted to keep a lower parts inventory and maintain ride quality which is why they did it that way. 

[MILW205]

I still don't get why RRs would want rebuilt trucks as opposed to new ones on an otherwise new locomotive. I read that many RRs even ordered GE U-Boats with rebuilt Blombergs. Weren't they first generation diesel technology? So why re-use them on second generation locos?

it was more a cost thing ....the Ann Arbor RR in Michigan traded in ALCo FA's on new GP-35's and got a discount for re-using the ALCo trucks....realy replacing the traction motors and maybe springs and brake parts trucks will last forever

Exactly, recycling high-wear items would not really make sense, but as J. Edgar said, trucks are basically indestructable and as such are easy to re-use.  Soo GP30's also used AAR Type B trucks re-used from Alco FA's: 

http://www.railpictures.net/viewphoto.php?id=180828&nseq=7

 

[oltmannd]

I still don't get why RRs would want rebuilt trucks as opposed to new ones on an otherwise new locomotive. I read that many RRs even ordered GE U-Boats with rebuilt Blombergs. Weren't they first generation diesel technology? So why re-use them on second generation locos?

For ride quality, you want soft bolster to loco frame (secondary) suspension and stiff axle to truck frame (primary) suspension.

For traction, you want it the other way around.

Early four axle locomotives didn't have high traction demand since the HP was relatively low, so the Blomberg and AAR type B (and FM's variant) trucks filled the bill.

The AAR type B truck had the advantage of being equalized - it would try keep the weight on each wheel equal even over track irregularities.  But, it also had the disadvantage of having the brake shoes tucked up between the drop equalizer bars.  Both were a swing hanger design and used coil primaries and leaf secondaries.

As the HP crept up and the RR's desire for a truck with fewer moving parts to wear out increased, the builders responded.  The GE FB and EMD Blomberg M both offered better traction and fewer and/or easier to maintain parts.

But, both rode poorly.

EMD responded by offering chevron style rubber secondaries (Amtrak) leaf springs in place of the rubber.   But, they retained the soft primary, stiff secondary suspension, so still required the snubber over the primary suspension.

EMD even offered eliptical springs that would fit in the place of the rubber pads for the Blomberg M truck - retaining the short swing hanger of the M truck.

Trade in trucks were often re-used under new locomotives because the truck frame castings are big, expensive items and RR were trying to shave a few bucks off the price. 

SCL stanadardized on the Blomberg design.  Why exactly I don't know, but I'd guess it was for the ride quality, ease of maintenance and because they were trading in 1st gen EMDs and had the truck frames available for new GEs.

[daveklepper]

I would also imagine that the Blomberg trucks wer easy to maintain.

[trainfan1221]

I believe the Blomberg M style debuted with the dash 2 line.  I know I always noticed it on GP38-2 models.  One thing I didn't see anybody mention is that this truck and subsequent variations don't have outer brake shoes whereas the older ones did.

[YoHo1975]

Not all Bloomberg Bs have the same number of shoes either.