Press Release: Official Cause of SP 4449 / SP&S 700 Holiday Express Derailment

This post is part of a series:
• Holiday Express Derailment
• Press Release: Official Cause of SP 4449 / SP&S 700 Holiday Express Derailment

by Aaron Hockley

This has been out for a few days but I know some folks haven’t seen it because I’m still seeing misinformation being spread…

DERAILMENT CAUSE DETERMINATION
OREGON PACIFIC RAILROAD COMPANY
East Portland Division
Milepost 1.78; December 10, 2005

On Saturday, December 10,2005 at approximately 12:15 p.m. two steam locomotives which were a part of the Holiday Express excursion train derailed in Oaks Bottom adjacent to the Springwater Trail. Cause of the minor low speed derailment was determined to be a broken raiL Both locomotives were quickly rerailed, track repairs made and operations resumed the following afternoon. Other than minor damage to the track, no injuries or other property damage occurred.

A technical explanation follows:

The two locomotives operating in push mode with six occupied passenger cars left the OMSI East Portland station at approximately 12:00 noon. They continued to operate southward negotiating several curves and sections of tangent track where they encountered a right hand I degree 50 minute curve identified as “EPIC Curve Four” at approximately twelve miles per hour where the speed limit is fifteen.

EPIC Curve Four begins at milepost 1.68, has a total length of 2320 feet and is superelevated with a total of one inch superelevation in the body of the curve and a spiraled north approach with runoff of 383 feet ending at milepost 1.75. The north portion of 1930 feet is laid with second hand 90 lb RA (section 9020) rail with flaIl-toe 4-hole joint bars, 91/2 x 10 single shoulder tie plates on 7 x 9 x 9 Ibot ties on nominally 22-inch centers with fbur spikes per tie; the remainder is laid with second-hand 100 lb RE (section 10025) rail with similar fastenings and ties. Tie condition is good to excellent throughout the curve and was recently ballasted and surfaced with a Jackson Model 6700S Tamper with computer liner. The point of derailment occurred at a joint in the low (inside or right-hand) rail at milepost 1.78 which is approximately 116 feet into the constant 1-inch elevated body of the curve. The six passenger cars, tender and trailing truck on SP 700 negotiated the curve without incident. The rear set of driving wheels on SP&S 700 derailed rolling the low rail outward. The SP 4449’s tender, trailing truck and drive wheels then flowed along the web of the overturned rail. Many of the wheels on the high (outside or left-hand) rail did not derail.

Investigation by Oregon Pacific management and others determined that at the point of derailment the following conditions were present which contributed to the cause of the derailment:

(1)The outside joint bar was cracked between the two northerly bolt holes and remained undetected during weekly inspections while the inside joint bar was in good condition and all four 15/16 x 5 /2 inch bolts with AREA washers were present and correctly tensioned.
(2) The south rail was drilled to correctly fit the joint bars; however, the north rail had been drilled with a slightly different bolt spacing and had been torch cut around the inner drilled hole to facilitate assembly.

Oregon Pacific Railroad’s conclusion is that the north rail was fractured as a result of the torch bolt hole and the non-continuous (cracked) outer Joint bar overstressed the one effective track bolt in the far north hole which exceeded its elastic limit and broke
allowing the rails at the joint to move outward and roll over causing the derailment.

This entry was posted on Sunday, December 18th, 2005 at 9:34 am and is filed under general info. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.