I expect that Mal is correct about a cant being part of the design of the present-day sleepers.
When rails were totally in cased in concrete, the perway team had a supply of thin wooded wedges cut with the required taper and these were placed on each concrete supporting block to give the rails the necessary tilt. I suspect that the greater the area of contact between rail and wheel, the better the adhesion, but somebody who studied physics can verify or debunk that.
The purpose of the web of the rail is to give it vertical rigidity so that that it does not droop between sleepers. Compared with trains, tram axle loads are much less but nevertheless it’s amazing just what constant use by trams will do to rails and especially special work.
When excavating a road for tram track installation, rail that is a couple of centimetres lower would make a negligible difference to construction costs. Melbourne has never relied on an existing road surface as a base for a permanent tram track.
Regards,
On 12 Jan 2019, at 6:07 am, Malcolm Rowe mal.rowe@...> wrote:
I assume that the ‘pad sleepers’ have the appropriate cant as delivered.
The rails are not continuously supported by concrete - the point of the technique is to have them supported by the sleepers - and that support is via springy pads to allow some give and less rigidity. You can see the pads in my pic at:
https://tdu.to/i/46901
The top finish is bitumen - so the flangeway / checkrail is needed for the traditional reason on street tramways - keeping the roadway from filling the flangeway.
Mal Rowe
From:tramsdownunder@... on behalf of Dudley Horscroft transitconsult@...>
Sent: Saturday, January 12, 2019 2:16 am
To:tramsdownunder@...
Subject: Re: [TramsDownUnder] Tramway rail profile - old and new
Thanks for these photos, Mal. Tis belatedly raises two questions for me.
1. How does Melbourne cant the rails? Are the duo-block sleepers as now used formed with 1:20 slants under the foot of the rail?
If not, how? Or does Melbourne now use rails upright and hope that the rails and tyres will somehow wear properly to give the cant
effect?
2. Give that, even when the duo-block sleepers are used, there is solid concrete under the rails between sleepers, so that the
rails are resting on a continuous level surface, and there is no intermittent support and lack of support, is it really necessary to
put the rail head and outer edge of the groove up so high? Why not just get rid of the web and lower the height of the rail by
perhaps 30 to 50 mm? This means 30 to 50 mm less digging and less need - supposing there was any need anyway - to dig out and
replace utilities.
Regards
Dudley Horscroft
----- Original Message -----
From: "Mal Rowe" mal.rowe@...>
To: "TramsDownUnder" tramsdownunder@...>
Sent: Thursday, October 11, 2018 1:29 PM
Subject: [TramsDownUnder] Tramway rail profile - old and new
> During a couple of track renewal exercises in Melbourne I have managed
> to collect some cut-off pieces of rail small enough to carry home.
>
> The attached pic shows a couple of these pieces - the left hand side
> piece is brand new RI57a as used now in almost all situations in Melbourne.
>
> Right side piece is from the early 1960s rail removed in Pascoe Vale Rd
> last week.
>
> It would have been standard 102lb per yard rail as shown at:
> https://tdu.to/i/52284
>
> It is well worn - roughly at the condemning line in the drawing.
>
> The rail head would have originally been higher than the flangeway.
>
> Note also the wear at the bottom of the groove - trams have been running
> on their flanges at this point in the track and started to wear away the
> bottom of the groove.
>
> Mal Rowe - still a trackwork voyeur
>
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