Re: (TGR) L and M class Garratts

["Derick Wuen" <cullend@webone.com.au>]

Keith Norgrove wrote in message <3950bedd.8619901@news.worldonline.co.uk>...
>On Tue, 20 Jun 2000 21:06:15 GMT, steam@1earth.net wrote:
>
>
>
>>The M class was cutting edge technology for its day, unfortinately its
>>use of radial axles was its downfall.
>
>Could you please substatiate/explain that, I have not seen any
>reference to radial axle problems in this discussion or elsewhere.
>>
>I thought the problem was the usual political expediency, easier to
>blame the loco, since there were only two of them, than the staff and
>management that allowed overspeeding. If there had been a good size
>fleet they would have had to learn how to manage them.
>
>
>Make friends in the hobby.
>Keith
>Visit <http://home.freeuk.net/grovenor/
>Garratt photos for the big steam lovers.

I think Terry has a point.

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.