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Mr. Linsky

'NEW JERSEY PUBLIC SERVICE # D900'

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Pictured below in several poses is fleet # D900 – an experimental 1950 GM Model TDH 4509 (ser# 0699) and delivered to Public Service Coordinated Transport of New Jersey in May of that year.

This bus was not your father’s Oldsmobile (so to speak!). The D900 (dubbed by GM as a ‘Reverse All-Service Bus) was a collaboration between engineers and designers at both the factory and PSNJ to fabricate a vehicle which would actually be two independently powered buses within one body.

You can throw your ideas of ‘Hybrid’ or Diesel Electric (of any type) right out the window because when this coach plied a non-electrified route, it operated as a pure 'Transit Diesel Hydraulic' having nothing to do with its second source of motive power.

However, when called upon for duty as a trolley bus (in this case to service the abandoned Newark subway system), the power poles were raised to meet the overhead grid and, simply put, a switch was toggled to shut down the Diesel and begin electric motive operation.

The secret of success in the development of the ‘RASB’ was the common drive rear axle which, in this case, sported two independent ‘drive’ bowls (one for electric and the other for Diesel).

The left hand bowl housed a conventional differential assembly while the right hand bowl (experimental) housed a double reduction 90-degree drive without differential and was connected to a large electric motor.

A sliding clutch was used as a means of transferring operation from one bowl to the other.

GM’s cost to PSNJ for its engineering, development and delivery of the D900 prototype was $55,000 but would be reduced to just over $25,000 per unit for an expected delivery of 72 production models;

Some ‘raw facts’ on the D900;

Seating; 43, Overall length; 35’8”, Width; 96”, Height 132”, Weight; 21,740lb, Diesel engine; 6V-71, Transmission; Hydraulic, Electric Motor; GE 1204B1.

Modifications; (as per New Jersey law and PSNJ specification);

Reinforced overhead and side steel panels adjacent to rear door and emergency door instead of aluminum, Wood passenger doors instead of steel, Rubber insulated stanchions, Rear bumper extended to clear overhead pole retrievers.

Because of both political and logistical problems, the D900 never actually saw revenue service as a trolley and was eventually stripped of its electric propulsion equipment and did serve for a number of years as a standard TDH 4509 from PSNJ’s Greenville Garage in Jersey City.

The complete story of the D900 may be found in the September/October 1992 Motor Coach Age.

Photos courtesy of the Motor Bus Society.

Mr. Linsky – Green Bus Lines, Inc., Jamaica, NY

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...it operated as a pure 'Transit Diesel Hydraulic' having nothing to do with its second source of motive power.

Diesel-hydraulic, or diesel-mechanical? I can't recall ever hearing any buses being built with a hydraulic drivetrain.

That sliding clutch must have been a lot of fun to work on. It sounds like an engineers wet dream.

Dan

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Diesel-hydraulic, or diesel-mechanical? I can't recall ever hearing any buses being built with a hydraulic drivetrain.

That sliding clutch must have been a lot of fun to work on. It sounds like an engineers wet dream.

Dan

Dan,

GM classified their transit buses in the fifties either as TDH (Transit Diesel Hydraulic meaning that the transmission was automatic and in fact was a new VH configuration from 1948 forward) or TDM (Transit Diesel Mechanical meaning that the transmission was standard shift usually with four on the floor and always built by Spicer).

The differential 'bowls' merely transmitted whatever power they would receive from the mode of transmission to the rear wheels.

Suburbans were designated as either SDH or SDM as well.

Mr. 'L'

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Dan,

GM classified their transit buses in the fifties either as TDH (Transit Diesel Hydraulic meaning that the transmission was automatic and in fact was a new VH configuration from 1948 forward) or TDM (Transit Diesel Mechanical meaning that the transmission was standard shift usually with four on the floor and always built by Spicer).

The differential 'bowls' merely transmitted whatever power they would receive from the mode of transmission to the rear wheels.

Suburbans were designated as either SDH or SDM as well.

Mr. 'L'

Actually, the H stood for "Hydrostatic" - their term for an automatic transmission (it has to do with the fluid used in the torque converter).

But nonetheless, they were standard automatic transmissions it appears, which is what I was curious about. Thanks.

Dan

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The world's first dual mode bus, perhaps?

Robert,

Funny that your signature mentions that passengers should be mindful of the platform gap when getting off the train.

That was an ongoing problem with the Jamaica Station of the Long Island Railroad in Queens, New York (in airline terms, Jamaica was and still is considered to be a 'hub' for the railroad with hundreds of trains passing through on a daily basis).

There is a certain section of each of the six or so platforms that curve and the gap at that point can be as much as six inches wide - I know because I once stepped into that 'abyss' with one leg going right down between the car and the concrete - very embarrassing!

I haven't used the station in years and I have to believe that some remedial steps (not a pun) have been taken to eliminate the hazard.

I think the problem originally arose because the facility was built in the very early part of the twentieth century when railroad passenger cars may have been much shorter.

BTW; The Long Island, which had its beginnings in 1834, is the largest commuter railroad in the U.S.

Regards.

Mr. 'L'

LIRRMUEARLY-2.jpg

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Man, 

I really like that unique variant of GMs “old look“ series. I think that this is the first time I’ve seen one of the oldest  hybird electric bus examples that I have ever come across I wish somebody from jersey could have preserved this bus. 

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