Re: 40 class bogies

Allan Brown (ajbrown@ozemail.com.au)
Wed, 08 Oct 1997 21:04:57 +1000

John McCallum wrote:
>
> Chris Stratton <stratton.chris.cp@bhp.com.au> wrote in article
> <01bcd3a1$69bcaf60$80441286@ws79.stnlswol.bhp.com.au>...
> > Allan Brown <ajbrown@ozemail.com.au> wrote in article
> > <343B04B5.17D3@ozemail.com.au>...
> > > It is written that the NSWGR 40 class diesel electrics were a
> derivative
> > > of the American RSD4/5 units, but suitably altered for local
> conditions.
> > > Considering that the RSD4/5s had asymmetric bogies with all axles
> > > driving, what prompted the change resulting in the 40 class having
> > > equdistant A-1-A bogies? Why wasn't a Bo-Bo arrangement used?
> > >
> > > Allan Brown
>
> I seem to remember posting an item on this subject but don't remember
> seeing it, so here goes again in case it didn't get through.
> The NSWGR 40 class were based not on the RSD series, but the RSC series,
> which were A1A-A1A wheel arrangement.
>
> > One advantage of the A1A-A1A over the Bo-Bo is the lower axle loading as
> > there is six axles instead of four. I don't know if that is the reason it
> > was used but it caused problems later with wheelslip caused by the
> driving
> > wheels wearing faster than the non-driving wheels. This then allowed one
> > driving axle to lift the wheels off the rails as the centre wheels were
> > larger which created a see-saw effect pivoting on the centre axle. That
> is
> > the reason the centre axle was removed from the units that went to Robe
> > River, as the higher axle loading on four axles was no problem.
> > Regards,
>
> I cannot agree with Chris about uneven wear on the driven wheels causing
> the "seesaw" effect. The bogies had equalising beams which ensured that all
> wheels carried the same proportion of weight reagrdless of track
> irregularity. The most likely reason the Robe River 40 class had the centre
> axles removed would have been to increase the axle load of the driving
> wheels. Considering the much larger loads which the locos would have
> required to shunt, the extra weight on drivers would have been necessary
> for efficient operation.
>
> John McCallum.

Thanks, John, for enlightening me on something I should have known. The
facts are in the recently published Green Diesels.

Cheers,
Allan