Blomberg truck question

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Blomberg truck question

Postby D.Carleton » Wed Nov 27, 2013 9:14 pm

In 1972 EMD modified the Blomberg truck for the Dash 2 line by, among other things, replacing the leaf springs with rubber pads. Most if not all Amtrak F40s were delivered with this truck. By the mid-1980s GP units were again leaving LaGrange on trucks with leaf springs and this would continue until the end of GP production. Did the rubber pads not live up to the expectations of their designers? How did the railroads' mechanical departments view the pads instead of the leafs?
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Re: Blomberg truck question

Postby Engineer Spike » Wed Dec 04, 2013 11:49 pm

I'll bet the rubber was cheaper. It might have had more rigidity than leaf springs. I think the leaf springs ride better. We have both GP38-2 and 40-2s with rubber. the 40s ridge rough, likely because they are heavier.

Maybe they eventually decided that the rigidity of the rubber had a negligible benefit. I'm sure that the harsher ride fell on deaf ears. The later side frames had a additional casting for the shock absorber which connects to the side will. Apparently this is to prevent truck hunting, or at least minimize it. Maybe Preston Cook will chime in as to why it suddenly was needed on the 60 series.
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Re: Blomberg truck question

Postby Allen Hazen » Thu Dec 05, 2013 12:53 am

I believe I have read elsewhere that the version of the truck with rubber pads has a rougher ride than the "once and future king" with the elliptical springs. The use of rubber pads (actually sandwiches of metal plates and "elastomeric" pads, which may not be actual rubber) is a characteristic of the GE FB-2 truck, which I think I have read also gave a rougher ride to the locomotive crew than the Blomberg.
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Re: Blomberg truck question

Postby bogieman » Mon Dec 09, 2013 9:04 pm

In 1972, when the -2 series locos were introduced, most of the North American RR's were changing to high friction composition shoes from cast iron. The change from elliptic springs to the rubber compression pad was made to facilitate the brake rigging with composition shoes, which needed only one shoe per wheel. To operate the shoes on one side of the truck with a single brake cylinder, a slack adjuster that ran underneath the spring plank was connected between the live and dead levers. To keep the slack adjuster high enough above the rail, the swing hangers were shortened and the spring plank raised which did not allow enough height to use the original elliptic spring. The rubber compression spring was substituted to take it's place but it only had limited static deflection (compression under load), much less than the elliptics, which negatively affected the vertical ride quality. Eventually, the elliptic spring technology progressed to where a shorter height elliptic spring could be manufactured to carry the load and restore much of the lost static deflection. This was introduced around 1984, IIRC. So the old elliptic spring, which typically had 9 leaves per half, was replaced by the low profile elliptic spring, which has typically only 3 much thicker leaves.

It's common to see single shoe brakes on the swinghanger truck where a rebuilder or the RR has simply retained the two brake cylinders on each side and added a very short slack adjuster between the live lever and a bracket welded to the safety strap that is there to support the loco if a swinghanger breaks. However, while this allows retention of the original leaf springs and swinghanger, it puts a load on the safety strap it was never designed to carry.

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Re: Blomberg truck question

Postby Engineer Spike » Mon Dec 16, 2013 10:31 am

Thanks Dave. Santa Fe kept 2 brake cylinders, and attached the slack adjusters to the safety strap. I hired out on the BN side just after the merger. Our GP39V,M,&E, as well as the GP40s upgraded to-2 all had clasp brake rigging. With Santa Fe management in charge, that modification was soon made to these classes. They moved the headlights to the nose at the same time.

I always noticed that the safety straps were bent inward, due to the forces that they were not designed for, as you mentioned.

When did the shock come along which is between the truck frame, and the locomotive side sill? 60 Series, right? What did they really gain with this? One would think that it was OK as is, since the design was almost 50 years old when the 60s came out.

Alan, this damn FB2 trucks are the worst I have ridden on. I'll bet a switcher truck is better. They were especially bad on the Santa Fe 500 series B40-8W. It looks like they may have a shorter wheelbase than a Blomberg. Blomberg takes lateral forces better due to the outward slope of the spring plank swing hangers. The FB 2 doesn't absorb that kind of side force. Take a crossover with the FB2 and you get thrown to one side, then the other. I don't see how Amtrak crews do it in the wide cab -8 at high speed.
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Re: Blomberg truck question

Postby Engineer Spike » Wed Aug 26, 2015 8:05 am

I'm a big B&M fan, and noticed a truck discrepancy in the 311, which is a GP40-2. It looks like it gained an older truck, with actual leaf springs, yet the brake rigging was converted to single shoe, single brake cylinder.

Apparently they must have had to use the shorter hangers, and modify the spring nest to one with a shorter height. It still begs the question as to why they did it. Was it for ride quality, or just to convert a old set of trucks, in order to be spares for the GP38-2, and 40-2 fleets.
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Re: Blomberg truck question

Postby D.Carleton » Sun Feb 07, 2016 1:14 am

Sorry I lost track of this thread. Thank you, Dave, for that enlightenment. In the intervening years I did have a chance to examine all three flavors of Blomberg truck in one engine facility and noted the differences.

Next question: NS is rebuilding their remaining GP50s into GP33ECOs with all the bells and whistles. Except for the first one the remaining have lost the rubber pad trucks and now sport the elliptic springs. Were the trucks rebuilt with metal springs or did the trucks come from somewhere else? Adding to the mix, the home made road slugs mated to the GP33ECOs ride on the trucks with the rubber compression pads.
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Re: Blomberg truck question

Postby bogieman » Fri Feb 19, 2016 12:16 am

It's relatively simple to replace the rubber compression springs with the low profile elliptic springs, EMD has mod instructions detailing how to do it.
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Re: Blomberg truck question

Postby Train Detainer » Sat Feb 20, 2016 1:05 pm

I'm sure that the harsher ride fell on deaf ears.


Not really. Rough riding locos are a source of back injuries. If you've ever been on one that seriously 'bottomed out' or constantly jarred you with a hard/fast spring on rough track you know what I mean. Changing out springs during a thorough class rebuild is much cheaper than even a single personal injury/disability lawsuit. Also have to keep in mind that the spring reduces impacts in both directions, so a better riding loco is also somewhat easier on track.

Adding to the mix, the home made road slugs mated to the GP33ECOs ride on the trucks with the rubber compression pads.


This seems to confirm - cabs of slugs usually are stenciled 'Do Not Occupy', entirely for safety reasons.
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Re: Blomberg truck question

Postby Engineer Spike » Fri Feb 26, 2016 2:56 pm

I never thought about FELA cases. At work we have CP GP38 and GP20eco classes with leaf springs, and clasp brakes. Our 7300 class GP38-2s have rubber springs, exceptone which still has single shoe brakes, but leaf springs. That one is also odd because the truck was cast by General Steel Castings, instead of LFM/Rockwell, or Dofosco. My point is that they ride better than our ex B&M GP40-2s. I would be surprised if EMD didn't have various spring sets, which are used based on the locomotive weight. This would avoid the unit riding too rough if a light unit is on heavy springs, or a heavy unit bottoming out with light springs.
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Re: Blomberg truck question

Postby bogieman » Tue Mar 01, 2016 10:56 pm

Engineer Spike wrote: I would be surprised if EMD didn't have various spring sets, which are used based on the locomotive weight. This would avoid the unit riding too rough if a light unit is on heavy springs, or a heavy unit bottoming out with light springs.

For the GP swinghanger truck, EMD has four sets of primary coil springs and three sets of elliptic springs to cover a locomotive weight range of 200,000 to 300,000 lbs. fully loaded.

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Re: Blomberg truck question

Postby Engineer Spike » Sat Mar 05, 2016 8:49 pm

With the various springs available, it is surprising that the GP40-2s ride so harshly. They are all like this, so it's not a case of the shop using the wrong springs.
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Re: Blomberg truck question

Postby bogieman » Sun Mar 06, 2016 10:52 pm

There's a lot of potential reasons for a rough riding locomotive - the first question to ask is it the vertical ride or lateral ride that's rough? For the swing hanger truck, the springs don't have a major effect on the lateral ride which is controlled by the swing hangers and the lateral free clearance between the bolster and truck frame and at the journal boxes to the pedestals and, if Hyatt bearings, the internal clearance axle end to thrust block. If vertical ride is rough and the trucks still have the rubber compression pads between bolster and spring plank, that's the most likely issue. You can check the vertical clearance between the sides of the bolster and spring plank side plates adjacent to the springs, if they show a lot of contact, that will indicate a lot of hard bottoming that's not good. If these are single shoe trucks with the diagonal primary shock absorbers, chances are high those shocks are worn out as they didn't not hold up well in service, although you have to remove one end and stroke the damper to tell if it's failed.
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Re: Blomberg truck question

Postby Engineer Spike » Tue Mar 08, 2016 5:30 pm

This is vertical ride, and they are single shoe, with rubber pads instead of leaf springs.
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