No SCL locos were used for radial truck development. All HTCR development testing was done on EMD3; the only other radial truck testing done by EMD was done on Santa Fe GP50 #3810 on two axle radial trucks in 1984 and 1986. The first test program on a prototype of the HTCR truck was applied to EMD3 at TTC in Pueblo in 1987, and it was tested there and at Raton Pass on the Santa Fe. That was a temporary application done by fabricating an "adapter plate" that included the mounts for the rubber secondary springs and the traction post. It was designed to be easily applied and removed without disturbing the HTC centerbearing and was applied to the cab end only. The prototype truck was cast solid to avoid the expense of coring using a simple "low cost" pattern thus was significantly heavier, by about 6,000 lbs., compared to the production trucks. Only a single truck was built applied at the cab end.
Based on the success of the 1987 test, EMD3 was permanently modified at EMD in 1989-90 with two production prototype HTCR trucks. This required filling in the centerbearing so that the traction post could be welded securely. The bolster extensions with jacking pads were cut off and replaced with new pieces designed to support the secondary springs, which located the jacking pads closer to the center of the unit. The handbrake application was modified and the traction motors had to be re-cabled. The mod work took about 6 months to complete at EMD by the Experimental Test department in the main locomotive bay which was empty at the time since most production had been moved to London. The unit was shipped out of EMD on its HTCR trucks for Pueblo in mid-1990. Testing was conducted at TTC from Sept to the Thanksgiving holiday when the test consist, including an SD60 loaned to EMD by UP, was shipped to Reno for 3 weeks of testing on the Reno branch between Thanksgiving and Christmas in 1990. After returning to EMD for clean-up and some minor mods, the unit was released for demonstration testing on the UP for a month or so after which it joined the Oakway fleet on BN. It was traded to the Oakway fleet for SD60 #9041 which went to EMD to become the home for development testing of the EM2000 computer control system.
In 2001, when the Oakway fleet came off lease and was refinanced, EMD3 went back to Pueblo to have it's original HTCR trucks replaced with a new set of trucks. The original trucks were scrapped after inspection because they used an early version of rubber bushings which were no longer available. EMD3's original trucks were also shorter in wheelbase by 2" compared to the production HTCR trucks. The extra length was added to accommodate the D90 DC and 1TB2630 AC traction motors, which have longer center distance axle to armature than the D87B motors.
Dave
beaulieu wrote:bogie_engineer what was up with the B+B truck tested under a BN SDP45 in a similar time frame. There was speculation that also was a radial design truck.
BN SDP45 #6599 was modified at EMD with the HT-BB truck at the rear starting late fall 1983. Roy Roush, who has since passed away, was the driving force behind that program and he convinced the BN CMO, I think his name was Thompson, to loan the SDP45 for the conversion. The idea, before AC traction took was developed, was to increase the locomotive adhesion capability with more weight and axles. At the time, EMD was also looking at developing a D10 traction motor, which would have been significantly larger than the D87, for more TE on 6 axles.
There is a mis-conception in the railfan community that the HT-BB is a radial truck, rather it is just two short wheelbase two axle rigid trucks with a span bolster. It does reduce curving forces to levels lower than EMD's two axle swinghanger GP truck by laterally linking the two B sub-trucks much the way inter-bogie control, used in South Africa at the time, did. After the locomotive modifications were completed and the unit repainted, in August 1984 it was shipped to BN's Interbay shop in Seattle where the instrumented wheels were applied in the week after Labor day. BN had closed the line thru Stampede Pass sometime prior to this test, but re-opened it specifically for testing the HT-BB truck and closed it again when the test was over. In fact, a high-rail inspection found numerous trees that had fallen across the tracks that had be cleared befored the test could start. Testing lasted about 2 weeks, after which the 6599 was used in revenue service until an engine failure occured that the BN did not deem worthy of fixing (the CMO supporting the program had retired, as had Roy Roush by that time). The HT-BB truck was then cut off, I believe it was about mid-1986, and returned to EMD, where it was inspected for wear and distress, then scrapped.
By that time AC traction was under development and the D10 traction motor program stopped. What ultimately killed the HT-BB was the production cost of the locomotive with it's two extra traction motor-wheel-axle sets and the larger alternator required to have enough current capacity for 8 motors in parallel that did not exist at that time. There were also no customers demanding it. It was proposed for use in Brazil about every two years as a replacement for the rigid D trucks on the DDM45's, which eat wheels, but the cost to replace the existing trucks could never be justified.
Our community is FREE to join. To participate you must either login or register for an account.