Re: trams riding on flanges

[Peter Homann <peter.homann@prr.org.au>]

The differential example still doesn't explain the frog on points on Swan St
where it is clear that head wear is zero (ie rust present) on the running
rail.  And that is on the straight leg of the points.  Wanna see it?  Walk
about 15m from Punt Rd back towards the Tennis Centre on the outbound track.

Cheers.
"Rod [comtrain]" wrote:

> What you are describing is the way Railway Engineers got around not being
> able to build a differential into the wheel sets.
> Question Why does any car need a Diff. ?
> Because when you turn a corner, the outside wheel has to go a longer
> distance than the inside wheel.
> Without a diff the outside wheel would need to turn much faster than the
> fixed axle would allow, and you would hear a lot of screeching as the rubber
> tyre burnt itself out on the road.
> Now the penny drops! Your tram makes a lot of noise going around sharp
> corners........because like the car without a diff....etc etc.
> Railway Engineers taper a wheel from the outside edge  gradually increasing
> the diameter until it becomes the flange. As it approaches the flange, the
> diameter increases at a much faster rate.The back to back measurement of the
> wheelset, is actually slightly shorter than the gauge of the track.
> The rails are stepped slightly with a base plate, so that the head of the
> rail is a closer match to these tapered wheels.
> When a railway bogie enters a curve, the wheel that will travel the
> furtherest will start to push its flange closer to the head of the rail, and
> the diameter of the wheel touching the rail head increases to wards its
> maximum. The flange should not actually touch the head of the rail.
> The other wheel is now being pulled away from the head of the rail, and of
> course the opposite happens, the diameter of the wheel touching the rail
> gets smaller..
> ....Voila...a differential !!
> This is how the Railway works, and I guess my observations of tram track
> lead me to believe the same would apply to your tram.
> Cheers
> Rod [comtrain]
>
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> "Chris" <csinn@netlink.com.au> wrote in message
> 39DC793C.2121@netlink.com.au">news:39DC793C.2121@netlink.com.au...
> > I was wondering if the practice of Melbourne trams bearing the full
> > weight of the tram on it flanges as it goes across crossings and points
> > is safe?
> >
> > It seams to me, as I drive my trams along (I work for Swanston trams),
> > say St Kilda Rd that all the crossings have been built up so that the
> > tread of the wheel does not touch the track. In fact if you look at the
> > rails at certain places they are in fact rusty, despite being heavily
> > used.
> >
> > I can only guess this is being done to avoid wear on the rails. But I
> > was wondering if the trams them selves were designed so that the flange
> > can bear the full weight of the tram or is this a cheap way of getting
> > around the fact that the rail components should be strong enough to
> > sustain heavy traffic with out wearing out so quickly.
> >
> > CNS

--
Peter Homann
Steam Fireman, Pichi Richi Railway
Administrator: http://www.prr.org.au