Altamont Press Discussion Board :: Discussion :: Re: Golden Gate Transit gets new diesel hybrids from Gillig

Re: Golden Gate Transit gets new diesel hybrids from Gillig

Author: Matt Farnsworth

Date: 06-24-2019 - 08:37

I drive for Pullman Transit (Pullman WA). Our new bus purchases since 2013 have been Gillig Hybrids.

Some of the frills have changed, and I can tell the radiator tank arrangement has changed from 2014 - 2017 but the basic layout of them has remained the same. Very similar to a diesel locomotive, with the addition of batteries. There is a Cummins ISB diesel engine. It is not connected to the wheels in any way. It only powers a generator. This generator provides electricity to the batteries which are located in the large hump on the rear of the roof. These batteries then power a traction motor that is connected to the rear differential. No transmission other than reduction gearing in the motor itself. I know these have a maximum speed of 60-65 MPH, above that the traction motor spins too fast and is at risk of damage.

One thing that is very interesting about these is the diesel engine speed is totally independent of the vehicle speed. When first started up the engine idles for a minute, then reves up very high to get the batteries fully charged then drops back to idle. When driving the engine stays at idle for a few minutes then slowly reves up.

Braking is primarily accomplished through regenerative braking. The traction motor is turned into a generator, the diesel engine drops to idle and the traction motor is used to charge the batteries. This regen braking is VERY powerful, only a very light touch is needed on the brake pedal. It works down to about 2-3 MPH, at which point it cuts out and braking is then accomplished only by the air drum brakes. The air brakes continue to work at any vehicle speed, but rarely are needed. There is a switch on the dash to turn off the regen braking, sometimes this is needed in slick snowy conditions as the regen braking can cause the wheels to lock up and slide in the snow and ice.

Pullman has a lot of steep hills similar to Seattle and San Francisco. Because of the electric traction and regen braking these hybrids do wonderfully on our hilly routes.

Matt Farnsworth
Pullman Washington

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Subject	Written By	Date/Time (PST)
Golden Gate Transit gets new diesel hybrids from Gillig	synonymouse	06-23-2019 - 19:23
Re: Golden Gate Transit gets new diesel hybrids from Gillig	FUD	06-23-2019 - 22:44
Re: Golden Gate Transit gets new diesel hybrids from Gillig	Matt Farnsworth	06-24-2019 - 08:37
Re: Golden Gate Transit gets new diesel hybrids from Gillig	JOHN	06-24-2019 - 08:42
Re: Golden Gate Transit gets new diesel hybrids from Gillig	Matt Farnsworth	06-24-2019 - 08:53
Re: Golden Gate Transit gets new diesel hybrids from Gillig	synonymouse	06-24-2019 - 11:02
Re: Golden Gate Transit gets new diesel hybrids from Gillig	FUD	06-24-2019 - 13:42

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Matt Farnsworth Wrote:
-------------------------------------------------------
> I drive for Pullman Transit (Pullman WA).  Our new
> bus purchases since 2013 have been Gillig
> Hybrids.
> 
> Some of the frills have changed, and I can tell
> the radiator tank arrangement has changed from
> 2014 - 2017 but the basic layout of them has
> remained the same.  Very similar to a diesel
> locomotive, with the addition of batteries.  There
> is a Cummins ISB diesel engine.  It is not
> connected to the wheels in any way.  It only
> powers a generator.  This generator provides
> electricity to the batteries which are located in
> the large hump on the rear of the roof.  These
> batteries then power a traction motor that is
> connected to the rear differential.  No
> transmission other than reduction gearing in the
> motor itself.  I know these have a maximum speed
> of 60-65 MPH, above that the traction motor spins
> too fast and is at risk of damage.
> 
> One thing that is very interesting about these is
> the diesel engine speed is totally independent of
> the vehicle speed.  When first started up the
> engine idles for a minute, then reves up very high
> to get the batteries fully charged then drops back
> to idle.  When driving the engine stays at idle
> for a few minutes then slowly reves up.  
> 
> Braking is primarily accomplished through
> regenerative braking.  The traction motor is
> turned into a generator, the diesel engine drops
> to idle and the traction motor is used to charge
> the batteries.  This regen braking is VERY
> powerful, only a very light touch is needed on the
> brake pedal.  It works down to about 2-3 MPH, at
> which point it cuts out and braking is then
> accomplished only by the air drum brakes.  The air
> brakes continue to work at any vehicle speed, but
> rarely are needed.  There is a switch on the dash
> to turn off the regen braking, sometimes this is
> needed in slick snowy conditions as the regen
> braking can cause the wheels to lock up and slide
> in the snow and ice.
> 
> Pullman has a lot of steep hills similar to
> Seattle and San Francisco.  Because of the
> electric traction and regen braking these hybrids
> do wonderfully on our hilly routes.
> 
> Matt Farnsworth
> Pullman Washington

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