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Radial Truck Development at EMD

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Posted by M636C on Friday, April 17, 2020 9:38 PM

SD60MAC9500
 

Bogie_Engineer It's funny you mentioned the truck used on the AEM-7 and GM10B.. The GM10B has always been a very interesting locomotive. 10,000HP on a Bo-Bo-Bo setup. Anything of interest from the type of truck used on it? Why the choice of a Bo-Bo-Bo layout?

 

I think the GM10B used an existing design from ASEA. I have an ASEA brochure which outlined a locomotive for the Kiruna-Narvik iron ore haul which was a Bo-Bo-Bo version of the Rc4, thus about 10 000 hp. This was not built, but six Rm class were built, basically low geared Rc4s, which gave the same power in three units rather than two.

The Rms didn't live up to expectation and were transferred to the main system for freight work.

Later six axle AC locomotives using the FLEXX truck mentioned earlier were obtained to replace the existing units which were triple sets of rod coupled 1'D+D+D'1 class Dm.

Scaled down versions of the Bo'Bo'Bo' were built for 3'6" gauge in Queensland for coal traffic, but these were only 2900kW due to the small narrow gauge motors.

Peter

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Posted by bogie_engineer on Saturday, April 18, 2020 11:02 AM

I was the noise engineer at the time the GM10B was designed so I did do noise testing on it but that was my only part of that project. The trucks and all the electrical gear including traction motors was an ASEA design. After the build and testing of the GM6C, which used modified HT-C trucks to accommodate the E88 motors with roller suspension bearings, EMD decided to do the GM10B for which the higher power required much bigger than the standard EMD motors. The ASEA motors used on the GM10B, and similar motors on the AEM-7 required 51" wheels so a whole new truck design was required. If EMD had designed the trucks, it no doubt in my mind would have been two 3-axle trucks but ASEA had the 2-axle truck design for their big motors so it was built in a B-B-B arrangement.

Dave

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Posted by bogie_engineer on Saturday, April 18, 2020 11:30 AM

Duplicate post

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Posted by M636C on Monday, April 20, 2020 9:00 AM

bogie_engineer

I was the noise engineer at the time the GM10B was designed so I did do noise testing on it but that was my only part of that project. The trucks and all the electrical gear including traction motors was an ASEA design. After the build and testing of the GM6C, which used modified HT-C trucks to accommodate the E88 motors with roller suspension bearings, EMD decided to do the GM10B for which the higher power required much bigger than the standard EMD motors. The ASEA motors used on the GM10B, and similar motors on the AEM-7 required 51" wheels so a whole new truck design was required. If EMD had designed the trucks, it no doubt in my mind would have been two 3-axle trucks but ASEA had the 2-axle truck design for their big motors so it was built in a B-B-B arrangement.

Dave

 

Dave,

From the photographs it appears that the GM10B had the "inverted swing hanger" arrangement on the secondary coil springs where the secondary springs were  attached to spring plank attached to the locomotive frame below axle level by swing arms. This allowed the centre truck to move sideays more easily on curves.

The Queensland Clyde ASEA Walkers freight locomotives had this arrangement.

My recollection is that the passenger locomotives (30 of the 80 were built with bogie frame supported motors and a higher top speed for passenger and intermodal trains) had a more complex double swing hanger system. I remember looking at the drawings of the centre truck arrangement of the passenger units in the Clyde offices at Eagle Farm and the three of us were just amazed at the complexity compared to the EMD designs we were all used to. 

Sadly, all the passenger units were either converted to freight operation (20) or scrapped (the remaining ten). The electrification remains but for most of its length it suplies only two tilting electric multiple unit trains making three trips in each direction. All freight is now diesel.

The remaining Clyde ASEA Walkers locomotives are largely still in service on coal trains.

Peter

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Posted by RMEX on Monday, April 20, 2020 7:39 PM

Dear David,

Were you at all involved in the SAR 11E class e-lok bogie proposal? B-B + B-B proposed by EMD but the SAR decided to keep using the six-axle bogie having the traction-link bars and the ASEA traction motors?

Kind Regards,

BW Ring

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Posted by bogie_engineer on Tuesday, April 21, 2020 12:07 PM

M636C

 

Dave,

From the photographs it appears that the GM10B had the "inverted swing hanger" arrangement on the secondary coil springs where the secondary springs were  attached to spring plank attached to the locomotive frame below axle level by swing arms. This allowed the centre truck to move sideays more easily on curves.

Peter

 

I haven't heard the "inverted swing hanger" description used before but as far as I know, the outboard trucks were similar in design to the AEM-7 trucks in which the bolster runs below the truck frame and has a pivot at the center connecting to the center of the truck frame so that the truck rotates about the bolster. The bolster has the coil springs on its ends that go up to the underframe supporting the loco. The bolster is also connected by an inclined, rubber bushed traction rod connecting to the underframe on each end which allows for lateral movement between the truck-bolster assembly to the underframe while it transfers the tractive force.
 
The unique part, to me at least, are 4 pendulum links that connect the boster to the truck frame that carry the vertical weightof the carbody in tension. These rods have semi-spherical pads on each end that allow the truck frame to rotate relative to the bolster for curving. This action creates a gravitational restoring force that centers the truck and helps with hunting stability.
 
The GM10B center truck was a similar design but had no rotational freedom between the bolster and truck frame. A really long traction rod was used to reduce its angularity when the truck moved laterally, I think there was about +/-10 inches of lateral travel. The end trucks had about +/-2 inches lateral freedom.
 
Dave
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Posted by bogie_engineer on Tuesday, April 21, 2020 12:15 PM

RMEX

Dear David,

Were you at all involved in the SAR 11E class e-lok bogie proposal? B-B + B-B proposed by EMD but the SAR decided to keep using the six-axle bogie having the traction-link bars and the ASEA traction motors?

Kind Regards,

BW Ring

 

I joined the truck design just as that project was nearing completion but so I wasn't involved in the HT-BB 4-axle articulated truck that was proposed by EMD as the alternative to the GSI 3-axle truck the RR much preferred. I was in charge of the test program on the HT-BB on the BN SDP45 6599 that we ran on BN's Stampede Pass in Sept 1984 so I know the design well. 

EMD did not have a truck that would accept the ASEA traction motors; the HT-BB was proposed because 8 EMD-size motors were needed for the 42" gauge to meet the tractive requirement. But Dr. Scheffel was not a fan of the HT-BB design and insisted on the GSI truck.

Dave

BDA
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Posted by BDA on Tuesday, June 16, 2020 7:11 AM

Hi Dave , Im interested to hear about the HTSC2 trucks under SD70ACes . I got to run on these and if anything they seemed to work better than HTCR2s under 90 MACs .

Cheers .

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Posted by bogie_engineer on Tuesday, June 16, 2020 3:10 PM

The only reason EMD developed the HTSC-2 truck was to offer a non-steering truck as basic equipment at a reduced cost. Since the SD70 series debut, EMD did not have a NA size locomotive truck that wasn't radial steering which put EMD at a cost disadvantage against GE whose standard truck was the Hi-Ad and their steerable truck came in as an option, which due to it's cost and reliability, RR's did not end up buying in big numbers and those that did like CSX eventually gave up on it too. Both the AC and D90 DC traction motors would not fit in the previously standard HT-C trucks as well as the tendency of the HT-C bolster to tip on the center bearing under high adhesion made it not an option; not to mention by the time of the SD70ACe, the HTCR manufacturing cost was less than the HT-C due to it's complex frame casting and the extra cost of the bolster. When the SD70ACe program was conceived, it's primary design target was to reduce manufacturing cost, starting with changing inverter suppliers from Siemens to Mitsubishi. The HTSC-2 non-steering truck was essentially an HTCR truck without steering beams and primary yaw dampers; it uses the same bearing housings, primary and secondary springs, and vertical and secondary yaw dampers as the HTCR. Most customers did recognize the advantages of the HTCR trucks and continued to specify them. I do know that CSX was very upset that the first and only order of SD70ACe's they bought, the 20 prototypes, did not have HTCR trucks.

BDA

Hi Dave , Im interested to hear about the HTSC2 trucks under SD70ACes . I got to run on these and if anything they seemed to work better than HTCR2s under 90 MACs .

 

When you say better, what are you referring to, ride, tractive effort, etc.

Dave

BDA
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Posted by BDA on Wednesday, June 17, 2020 5:47 AM

Rode and seemed to track a bit better .

90s sort of rocked through corners and made a few strange noises . The 90s here are Phase 2s converted to 710 2 strokes , not sure what sort of mileage they would have done at UP with the H engine in them .  

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Posted by bogie_engineer on Wednesday, June 17, 2020 11:25 AM

The Phase 2 90MAC's were a bit different than other EMD locos with their integral fuel tanks that created a "diving board" effect which impacted the ride sensation. From a truck standpoint the vertical and lateral ride should be very similar since the suspension components are all the same but ride encompasses everything from the seat to the rails so it's not surprising they feel different.

Dave 

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Posted by Overmod on Wednesday, June 17, 2020 6:15 PM

This thread could run for years and I would still be avid to read (and learn from) new posts.

bogie_engineer
The Phase 2 90MAC's were a bit different than other EMD locos with their integral fuel tanks that created a "diving board" effect which impacted the ride sensation.

Did this contribute to the frame cracking that put many of these units out of service... and were fixes to the 'effect' incorporated in the rebuilding (which seems to date to be reasonably successful)?

I'd be interested in the full official story of 'earthquake mode' (which I understood in the '90s to be in part a desire for 'more rapid loading than GE' combined with modal rather than gradual proportional engagement of traction control).  Since this was apparently characterized as observable on SD80MACs, was the 'diving board' excitation observed in other long-frame contemporary EMDs and not just the integral-tank variant?

It seems at least possible that earthquake-mode modulation within the period of vibration of the frame would easily contribute to some of the more exotic modes of isolated-cab motion.  I can easily see why vibration analysis, even in multiphysics modeling, might not predict this.

Is there an analogue to higher polar moment of inertia for the end axles of HTCR trucks, due to the lever system or any individual yaw-excursion damping of the axles, compared to the simpler dynamics where all three axles are 'normally' constrained in the less expensive version?  

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Posted by bogie_engineer on Wednesday, June 17, 2020 8:38 PM

Earthquake mode as I understood (I wasn't involved with trucks at that point) was a dynamic response to the frequency of inverter changing TE that corresponded to the bounce frequency of the wheelset on the motor nose link at about 6 Hz. Re-tuning the control system took care of the worst of it although at the adhesion limit it still happens.

The underframe cracking on 90MAC's was due to the very rigid mounting of the ends of the 6,000 gallon fuel tank to the underframe wherein the buff/drag load was carried into the fuel tank. Prior to the 80/90MAC, the fuel tank was held on long bolts passing thru holes in the heavy bottom plate of the UF to a heavy angle welded to the endplate of the fuel tank. With the longer, heavier tank on the 80/90MAC's and the desire of the manufacturing and service groups to have external fasteners holding the fuel tank to avoid having to remove and engine if the bolts needed replacing, the fuel tank had the angle welded about 6" lower on the end of the tank and a second angle with gussets between each bolt was welded to the bottom plate which resulted in a much stiffer connection. The first failures occurred as cracks in the fuel tank and they were campaigned to be opened up and significantly stiffened internally. This fixed the tank cracking but the stiffer tank led to the fatigue cracks in the underframe. IIRC, the bottom plate on the 80/90 is only 1" thick compared to the 70's and prior which ranged from 1.5-3.0 inches. The underframe is deeper on the 80/90MAC's which is why it worked with a thinner bottom plate but given the long length of those units the deflection at the center under 1M lbs. buff load is about 4" compared to the ends. The fix for the underframe cracking involved, of course, gouging out the cracks and welding them up, and then softening the mounting of the tank using bolts with spacers and spherical washers at one end and letting that end slide on the mounting so the tank didn't carry so much of the buff load.

Dave

BDA
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Posted by BDA on Friday, June 19, 2020 6:25 AM

I had a close look under the 90s here and the fuel tanks appeared to be seam welded for their entire length to the under frame . They have gusset plates and in some places box sections welded towards the tanks ends to the frame .

For some reason they'd occassionally get this reasonably violent cyclic thudding which I equate to earthquake mode . It felt like a really rapid loading and unloading of traction power and everything in the isolated cab would jump and dance all over the place . I had thought these issues were because of the early Siemens control systems and inverter antics .

70ACes don't seem to have any of these issues but they would be have the benefit of further development and improved electronics . 

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