INTRODUCTION

n the early 1970's, the 600 Class were beginning to suffer many failures due to overage equipment and it was decided to rebuild them with new engines, transmissions and control systems to make them compatible with the later 620 and 900 Classes. In May 1972, the NSWGR ordered 22 14-litre Cummins diesel engines and Twin Disc hydraulic transmissions to upgrade the entire class of ten sets. At this time many of the 620 Class units had been in intensive service for some time and were also plagued with mechanical failures. At times, two power cars operated back-to-back with only one engine working in each or the sets were loco hauled to maintain services. As a result, some of these new engines and transmissions were diverted to re-engine five members of the 620 Class, resulting in only five of the ten original 600 Class sets being rebuilt.

The units converted were 601/701, 605/705, 608/708, 609/709 and 610/710. The converted units were reclassified as the 660 and 760 Classes and renumbered by adding 60 to the original numbers - 601 becoming 661 and 701 becoming 761, 610 becoming 670, etc. The original 600 Class vehicle codes of FPH and CT were retained for the converted units.

CONSTRUCTION

The rebuilding process involved strengthening the underframe and the fitting of side mounted radiators in a similar fashion to the 620 and 900 Classes. The electrical and control systems were modified make them compatible with the 620 and 900 Class arrangements. Two inclined 300 hp 6 cylinder turbocharged Cummins NTA-855-R2 diesels coupled to Twin Disc DFFR 10034 torque converter transmissions were fitted. 620 Class style driving controls replaced the original controls. At this time, cast 2PG and 2TG bogies were also fitted to replace of the original fabricated 2PC and 2TB bogie types. These converted units were to be pooled with the 620 Class for suburban and outer interurban working and passenger seating for 24 Second Class was provided in the former 600 Class luggage area and a smaller luggage compartment was provided at the No.1 End adjacent to the driver's cab and vestibule with a capacity of 2 tons. During the reconstruction the original 600 Class door and window arrangements were not changed except for the removal of one window and one row of seating in the No.2 End of the power car to accommodate the larger radiator installation. This window arrangement made them easily identifiable from their 620 Class sisters.

Later, these vehicles were fitted the up rated 335 hp 6 cylinder turbocharged Cummins NTA-855-R4 "Big Cam" engines and Voith T211r hydraulic transmissions deployed in the later 620 and 900 Class upgrades.

The trailer cars received new electrical control systems and the 620 Class driver's controls, however, the existing 700 Class window arrangement and seating configuration remained unchanged.

VEHICLE CONFIGURATIONS

COLOUR SCHEMES

The class entered service wearing the passenger car colour scheme of Tuscan Red with buff lining. Deep Indian Red with Buff lining was replaced the Tuscan Red in the late 1970's and this was followed by the State Rail corporate "Candy" scheme in 1982.

SOLAR POWER

FPH 661 has been fitted with a solar powered electric motor for use at the Byron Bay Resort in northern NSW. The vehicle was rebuilt at State Mine Railway workshops in Lithgow and retains a single diesel engine for emergency use. 661 and its companion trailer NTC 726 were transported by road to Byron Bay in October 2017. It is expected that they will commence operations on a three kilometre route between the resort and Byron Bay township in November 2017.

REFERENCES

• "Rail Motors and XPTs" by David Cooke (Australian Railway Historical Society - 1984)
• 660 Class Rail Car record cards (courtesy of Stephen Preston)
• Drawings by Bruce Agland.