On 3/4/24 13:56, 'Richard Youl' via TramsDownUnder wrote:
> Bob,

>

> The Gold Coast trams weight 60.4 tonnes have 4 bogies, only 3 powered. So your 64 tonne estimate is basically correct.

>

> An 8 tonne axle load is not particularly heavy, especially when shared over nearly 40 metres, but nevertheless massive steel and concrete reinforcing is under the road tracks but the 7km to Helensvale station is ordinary open ballast.

>

>

The weight isn't evenly distributed - the motor modules with traction converters on the roof are heaver than the trailer bogie/module. (Hence why the Melbourne D2s have a tendency to skid their middle bogie). But the killer isn't just the axle load, those leading modules, when they enter a curve, the ENTIRE weight of that leading module has to swing all together due to the 'fixed trucks'. This puts a lot of load on the flanges of the leading wheel set as it's trying to make the entire first module with it's many tonnes of body and equipment turn into the curve all at once.

But building trams with swivelling bogies and lower axel loads (i.e. more wheels) is more expensive, so they buy the cheaper vehicle for cheaper upfront costs and pay later in increased track wear later.