Background and overview
Between 1997 and 1998, West Japan Railway Company (JR West) modified selected two-car formations originally comprising class Moha103-2500 powered end cars. These units were reconfigured into new two-car sets by incorporating class Moha102 intermediate powered cars, which were newly constructed with cab ends. The modified sets were reclassified as the 103-3500 series.
The 103-3500 series was introduced in 1998 to coincide with the electrification of the Bantan line between Himeji and Teramae. The conversion aimed to provide suitable rolling stock for local services on the newly electrified section, utilizing refurbished components from existing 103 series vehicles.
Car body
The 103-3500 series feature narrow-profile steel carbodies measuring 19,500 mm in length and 2,800 mm in width. To reduce overall weight, the structure incorporates lightweight shaped steel members and pressed beams. Cold-rolled steel plates are used for the body sides, while hot-rolled steel plates are applied to the roof panels to optimize cost performance. The rain gutter is integrated into the body skin, resulting in a cleaner exterior profile.
To form two-car sets, class Moha102 intermediate motor cars were converted into powered end cars by constructing new cab-end structures at the rear of the carbody. These modified vehicles were reclassified as class Kumoha102-3500.
The cab end adopts a gabled, non-gangway configuration with a slanted, large-format windscreen. Exterior lighting consists of two centrally mounted sealed-beam headlights positioned above the windscreen and two taillights located below. A destination rollsign is installed above the driver's-side windscreen, while an operation number indicator-featuring a rotary disc mechanism-is mounted above the assistant driver's position.
Each car is equipped with four double-leaf automatic sliding doors, each measuring 1,300 mm in width. The door assemblies include provisions for future installation of passenger-operated door buttons. Between the doors, existing double-hung windows were replaced with aluminum-framed side windows featuring a two-part configuration: an upward-sliding upper sash and a large fixed lower pane. End windows were converted to fixed-pane units. All windows are fitted with heat-absorbing glass. Station broadcast speakers are mounted below the side windows.
Door operation is controlled by TK4D units installed beneath the bench seats. Climate control is provided by a roof-mounted AU75B air-conditioning unit rated at 42,000 kcal/h. Roof ventilators were removed, and polyurethane resin-based roofing materials were adopted. Additionally, class Kumoha103-3500 cars feature a destination rollsign mounted on each side near the rear end.
The exterior livery of the 103-3500 series consists of wine red with dark gray accents applied to the upper portions of the doors and the wall behind the cab.
Bogies
The bogies are designated as type DT33, equipped with wheels measuring 910 mm in diameter and a wheelbase of 2,300 mm. This configuration employs coil springs as bolster suspension elements and adopts a pedestal-type journal box arrangement.
Power transmission is handled via a parallel cardan drive system incorporating a hollow shaft. The gear ratio is set at 6.53, enabling high acceleration performance.
The braking system utilizes single-truck brake rigging with a single-action brake cylinder.
Traction unit and ancillary equipments
The 103-3500 series EMU is equipped with eight MT55A series-wound brushed DC traction motors, each rated at 110?kW. These motors are controlled via the WCS20 motor-driven camshaft control system and the MR51 forced-draught traction resistor, both of which are installed on class Kumoha103-3500 vehicles. This system employs armature-resistance control to regulate acceleration and power output.
Class Kumoha102-3550 vehicles are fitted with a motor-generator unit (MH135-DM92)
rated at 160 kVA, along with a motor-driven air compressor (MH113-C2000M),
both mounted beneath the floor. These units supply electrical power for
onboard systems and compressed air for braking and door operation.
Current collection is performed via a PS16 lozenge-type pantograph mounted on the roof of class Kumoha103 vehicles.
The braking system consists of an electromagnetic straight air brake, supplemented by rheostatic braking. This configuration ensures effective deceleration while minimizing mechanical wear.
Accommodation
The passenger saloon of the 103-3500 series EMU features a fully longitudinal seating layout, optimized for high-capacity commuter service and smooth passenger flow during boarding and alighting. Each bench is fitted with end partition panels to delineate individual seating spaces. The ceiling was flattened to align with the air-conditioning ductwork, and conventional electric fans were replaced with cross-flow air blowers. The cab-end partition windows were enlarged to the maximum possible size. Fluorescent lighting fixtures were equipped with protective lamp covers, and passenger hand straps were installed throughout the vehicle. Traditional overhead luggage racks were replaced with pipe-frame structures featuring decorative end caps. Floor inspection covers for the traction motors were sealed with metal plates.
Externally, the cars are identical to the existing 103-0 series, but modified for conductor-less operation with the installation of a ticket machine (which issues boarding station tickets), a fare display, and a fare box.
Modifications
Door Operation Button Installation
The door control buttons were installed at an unspecified date prior to 2004; the exact year of modification is unknown.
Toilet Retrofitting
Class Kumoha102-3500 cars were retrofitted with Western-style toilets between
2005 and 2007. The facilities utilize chemical disposal tanks and are located
at the rear end of the carbody.
Additional Pantograph Installation
In 2014, JR West retrofitted Kumoha102-3503 and -3509 with an additional backup pantograph mounted at the front end of each vehicle.
Operations
The 103-3500 series entered revenue service with the opening of the electrified section of the Bantan Line between Himeji and Teramae in 1998. As of today, they continue to operate on local services along the Bantan Line. |
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