Thanks for the link, had not seen that presentation.
You are right that this truck does not use a steering linkage but it is considered self-steering none the less. Here they use a swingarm-type design with a special design bushing at the pivot that allows some longitudinal travel for steering. With this arrangement, under high tractive effort, there is longitudinal translation of the end axles on tangent track but the axle will steer itself in curves. What we found during testing, where we instrumented the axle traction rods as force transducers, was that if we constrained the steering beams to not allow axle steering, the forces in the traction rods during coasting conditions were nearly equal and opposite. The taper on the wheels is trying to steer the axle into a radial position with the outer traction rod in the curve being in tension and the inner in compression. As tractive effort increases, the tractive force adds to the steering forces in the traction rods such that the inner rod may see a very low force and the outer one very high force. With a pedestal truck, no motion is allowed so the pedestals have greatly different forces acting on them in curves which is not apparent.
Back to the EDI design; so with the relatively soft longitudinal bushings, the axle can steer itself within the limits of travel allowed by the bush
The paper has some diagrams that might help explain to other readers the considerations in the designs being discussed here.
UGL have not applied this design in Australia yet, all the locomotives (including the C44aci, the competitor to the GT46C-ACe) using a familiar GE export design.
UGL have supplied many trucks for GE export locomotives all over the world, and they must be regarded as successful if not reflecting recent ideas.
Interesting paper Peter. The basic design of the UGL bogie is really no different than the latest EDI and EMD GFC bogie where all have adopted axle guidance via fixed traction rods and soft primary, stiff secondary vertical suspensions. The authors dismiss the radial steering bogies using linkages which serves their purpose but the real world improvement in wheel wear and lateral rail force is well documented in technical papers by EMD and AAR. While it is true that the steering of the axles declines with higher tractive effort, the flange force also declines so flange wear is improved. It’s worth noting that locomotives don’t spend the majority of their operational time at the limits of adhesion where the friction is saturated. As the paper states, it is true that customers that previously bought GE’s Steerable Truck on their locos have gone back to the standard “roller blade” trucks, however, EMD’s customers continue to purchase HTCR radial trucks even with a cheaper non-steering version available.
Neatly in the middle between the HTCR and UGL trucks was the Adtranz/Bombardier “FLEXX”, as mounted on the Blue Tiger locomotive; this as I recall it was a kind of antithesis of soft primary/stiff secondary (with nested harmonic-breaking primary springing, very long secondary springs, and a traction strut as low physically in the locomotive as possible). There was at one time an interesting technical paper (as I recall, for one of the conferences) that went into design detail, including as I recall the line of development from the Henschel Flexi-Float bogie design, and someone astute may still be able to pull this out of the Wayback Machine.
I can still remember when the Fabreeka-style chevron springs were supposed to be the future of controlled primary suspension…
The long travel secondary springs provide a great vertical ride and low bogie yaw stiffness, but in a 3-axle truck, the short travel primary springs would not work in North America where staggered joints are prevalent, they just can’t equalize well enough. Our design criteria for any bogie was to negotiate a 39’ staggered rail joint profile with a 3" inverted sine profile. After center axle spring pocket cracking on SD Flexicoil trucks, on Rock Island I believe, the criteria was raised to 4" for switcher applications. Stiff primary just won’t make it.
We used to refer to our associate Henschel’s Flexi-Float bogie as having a wagon tongue. For higher speeds, the rubber chevron springs do a great job of locating the axle and give high axle lateral stiffness necessary for stability. Our only EMD experience was on the AEM-7 and GM10B ASEA designed trucks. They’d never work here in a 3-axle truck due their short travel, about 1.25". We did try to use them on the HT-B truck but they had a lot of set and drift issues there.
What is the specific history (and experience) of the use of ‘chevron springing’ on the GP40X HT-B and then laterally on the “Blomberg-P” trucks?
Also – what’s your opinion of the design approach and details in the Alco Hi-Ad trucks, including what might have been done to address their issues with harmonic rock on that kind of severe cross-level profile?
I’m not familiar with “Blomberg-P” designation but assume that is a railfan name for the GP Inclined Rubber suspension truck. That truck was fitted to some Amtrak F40PH’s and some of the GP40X’s on the Southern IIRC. This was the first attempt to improve the vertical ride of the GP Single Shoe truck introduced with the Dash 2 series. That truck substituted the long used elliptic springs with a pair of rubber compression pads which were shorter than the elliptics, about 5" versus 9" and those allowed the use of a shorter swinghanger, opening up sufficient clearance under the spring plank to the rail to run a slack adjuster connecting the brake levers on each axles 1 and 2. The original design suspension with leaf springs by Mr. Blomberg had 4" of secondary static deflection and 3.25" of primary static deflection. The rubber spring on the new in 1972 compression rubber suspension had only a little more than 1" of static deflection, bringing the total to about 5.25". This absolutely ruined the good vertical ride of the truck, which RR’s started complaining about almost immediately. Effort was made to try to change the damping of the new vertical primary dampers that were added to replace the lost damping in the elliptics to improve the ride but it didn’t really help. So a design change to the compression rubber was developed. It used a pair of rubber compression/shear pads placed in a chevron arrangement on each side of an new design spring plank. The deflection in the secondary increased to a bit over 2" so the ride was better but not great. This used the same bolster and the long swinghangers but required a new spring plank (the compression rubber used the original bolster and spring plank with some modifications). There were failures of the steel shims embedded in the rubber springs fixed by some mods to the plates and shimming was required as the rubber took a set. At the time, really throughout Dash 2 production, most of the GP orders wer
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.
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.
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
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?
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.
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.
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 .
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.
When you say better, what are you referring to, ride, tractive effort, etc.
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 .
