The Loco Story :

Diesel Hydro-Mechanical Locomotives built by Chittaranjan Locomotive Works, first in 1971.

Later the dual cab versions was built in Parel Loco Workshop first in 2008.

First ZDM3 class locomotive was introduced in Kalka-Shimla section of Northern Railway.

Basically a Bo-Bo design with two 2-axled bogies of 9.25t axle load with two stage suspensions. The axle bogies are of roller bearing type.

Fit for operating in 2ft 6in (762 mm) narrow-gauge sections of Indian railways with permissible axle load upto 11t.

The design incorporates necessary provisions to accomodate pony trucks at either end thus to modify the same to 1Bo-Bo1 design to reduce the axle load to 7.0t for other NG sections.

Fitted with Suri Hydro-Mechanical transmission consisting of a Trilok converter coupling to cover the road speed range from zero to 70% of max. speed & a hydro-mechanical coupling to function thereafter. Transmission to the axle drivers by means of cardan shafts.

The locos built from Parel are fitted with Voith turbo-reversible transmission having one converter for each direction of travel.

The underframe is built up of fabricated I section & plates in accordance with the conventional practice.

The cab, engine hood & radiator housing are made in different parts to facilitate removal for attention to various equipements.

Loco is fitted with compressed air brakes & vacuum brakes for the trailing stock.

For later versions (Parel make) dynamic braking by emptying the filled converter and filling opposite direction converter.

Technicalities :

Engines --- Single Mak model 6M282A (K) turbocharged after cooled diesel engine.

Transmission --- Suri Hydro-Mechanical transmission. Kirloskar Pnematic make Voith turbo-reversible transmission.

Axle Load --- 9.25t tonnes

Power output --- 700 hp

Bogie type --- Bo-Bo roller bearing type

Max speed --- Varies between 25 kmph & 40 kmph.

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