Re: (TGR) L and M class Garratts [now ASGs too]

["James Shugg" <james@shugg.freeserve.co.uk>]

Derick Wuen <cullend@webone.com.au> wrote
> In Australia most administrations frowned on pony truck locos in passenger
> or fast freight service. The theory is that a lighter axle loaded 4 wheel
> truck will out-perform a 2 wheel lead truck with a heavier axle load and
> greater tendency to climb the outer rail on curved rough (i.e. normal
> Australian) track. This goes for Bissel type trucks but particularly
radial
> trucks since a fatal prang with a "green doney" 2-4-0T at Sydenham NSW was
> blamed on the poor tracking qualities of the radial truck design, and the
> green donkeys were relegated to shunting.
>
> On this logic, a 4-x-2 + 2-x-4 Garratt "should" be less stable in the
> trailing engine department (irrespective of direction of travel) than a
> 4-x-4 + 4-x-4, especially if the "2" equipment is radial. I doubt that an
> argument could be sustained that the lead engine unit would smooth the
path
> for the trailing unit in any appreciable manner. The trailing engine unit
on
> the M probably behaved like a 2-4-4 as a vehicle.
>
> If the M was speeding through sharpish curves, then I think its a good bet
> that the leading truck on the rear unit would tend to derail first, or
snag
> imperfections in the track.

Very interesting - good to see a Tasssie thread!

Didn't the Australian Standard Garratt 4-8-2+2-8-4 have a reputation as
being prone to derail?  If so, has it been established that the wheel
arrangement was contributory, along the lines described above?  I seem to
recall that half their driving wheels were without flanges;  that to me
sounds like an accident waiting to happen at speed (like when one of the Emu
Bay locos lost her brakes coming down the hill in to Burnie in the early
1960s).  But I'm just speculating.

James