Does anyone have a SAR broad gauge roadbed/ballast profile they can share?

I'd always felt that the 3/16" cork roadbed I used in my last layout (HO scale) looked a little high compared to prototype photos and am thinking of buying cork rolls for the new layout and so wanted to see if any scale references were available?

At the very least, I'm guessing a much higher angle of repose for the ballast (than the standard 45 deg) is appropriate, eg something closer to 60?

SAR  would have had numerous ballast profiles from top notch mainlines to run down and on the ground lines. So really depending on what you are modelling there could be great variation. Nearly all branchlines were built on the cheap and some were also built as pioneer type lines with little or no ballast at all.

7. Ballast

7.1. Functions of Ballast

Ballast is crushed stone, generally between sizes of 10 mm and 70 mm. It should be cubic in shape andnot flakey. Ballast should be hard enough not to crush but not so hard that it does not interlock. It must not dissolve or soften when wet.

(a) Ballast for toad distribution

Ballast is packed tight under sleepers adjacent to and under each rail. The deeper the ballast, the better the loading is distributed to the formation.

(b)Ballast to hold position

Ballast also needs to be packed tightly between sleepers and at sleeper ends to hold sleepers firmly in place. The vibration of passing traffic will gradually shake the ballast into a tight condition.

Tight ballast is necessary to prevent track buckles and to stop rail creep.

(c) Ballast for drainage

Ballast should be kept clean, particularly outside the sleeper ends, to ensure that water drains freely from the track. Any growth of vegetation in the ballast will lead to clogging of the drainage.

7.2. Ballast Cross Section

On track where no electric track circuit exists ballast is to be smoothed off level with the tops of sleepers and out to the edge of the ballast shoulder. On tracks where there are electric track circuits, ballast should be kept 25 mm below each rail so that electrical cause a gradual run-down of batteries, or a sudden signal failure. Such failures are particularly likely to occur after a medium rainfall following a dry period.

While this is a 'safe' failure, it is particularly inconvenient and disruptive to rail traffic. However, sufficient ballast in the cribs is essential for protection against track buckling, which is an 'unsafe' failure.

Ideally, ballast should be kept below rails by 25 mm, but up to and even above sleeper level from a point 150 mm outside the foot of the rail.

Ballast should slope away from the shoulder at a slope of 1 in 2. If it is profiled by a regulator at a steeper slope, it may fall away with traffic vibration, and reduce the shoulder width to an unsafe condition.

Ballast depth below underside of sleeper varies and is generally beyond the authority of the trackman to decide. The amount of lift will be directed by the Roadmaster.



Edit: Source is AN Track Maintenance Guide 1988.

But that's just the ballast. The ballast is laid over a foundation which evens out the landscape and allows for cesses (drains), so that the ballast can work. Needless to say, the foundation varied considerably, too, with place and time.

What is a toad?

*ribbit*

I suspect a typo for "load".

But that's just the ballast. The ballast is laid over a foundation which evens out the landscape and allows for cesses (drains), so that the ballast can work. Needless to say, the foundation varied considerably, too, with place and time.

Correct - very variable. I have ssen extensive references of NG being constructed with a slope of 1.5:1 (33 degrees), but the size of it always varies. I have one drawing which shows 11 different variations on the same line. I have also seen references to BG/SG being 2:1 (27 degrees).

Today most Ballast is regulated by machines that raise and lower the Super, space the sleepers at the correct distance and 'lay' the Curve or Straight in the correct position according to the survey markers.
For uniformity, I cant see these settings of ballast under the rail varying whether it is Electrified, Track Circuited or not as thats not really of interest to the work gang.
During my years of watching these Gangs and machines at work was their over whelming dedication to finding any cables, wires, Bonds running at, beside or under the track and doing their utmost to rip, tear and destroy them, much to the annoyance of the Signals Branch.

One Sigs electrician during a major  upgrade claimed that Per Way had increased its rate of damage to the signals cables quite markedly now the locations were being marked in Hi Vis spray paint which now gave them a much clearer target to hit.

Much obliged Simont. As Allan noted, that's the ballast and not the full roadbed profile, but I now have a lot more information than I did before.

I'm wondering where the 'shoulder' starts in that table. Even on jointed rail on wooden sleeper, does the specified shoulder of 150mm / 6" (presumably from the end of the sleepers) seem very optimistic to anyone else? From steam era pictures of the main south line in the hills the ballast slope often appears to start right at the edge of the sleepers, although that may be due to a poor or degraded subroadbed, rather than the intention.

I have steam era NYC profile to compare, and that calls for an 8" shoulder which is clearly visible in period photos.

Even on jointed rail on wooden sleeper, does the specified shoulder of 150mm / 6" (presumably from the end of the sleepers) seem very optimistic to anyone else? From steam era pictures of the main south line in the hills the ballast slope often appears to start right at the edge of the sleepers, although that may be due to a poor or degraded subroadbed, rather than the intention.

The shoulder starts at the end of the sleeper.
There is a lot of photographic evidence to support the idea that shoulder profiles were much smaller in the steam era.
Even today with mountains of ballast compared to the steam era it is not unusual to find locations with a less than design shoulder profile.
On NSW pioneer branch lines with 'earth' ballast, the 'design' ballast profile peaked in the middle of the four foot at near top of rail height and sloped down under the rail to the end of the sleeper, the end of the sleeper was almost completely clear of the ballast. In maintenance practice the peak in the 4' was not maintained. Such lines were usually ballasted with loco ashes at a later time.

Most modellers especially steam/diesel transition era make the mistake of making their roadbed too high, IMO.
When I modelled HO NSW branch lines, I used a tyre inner tube cut into strips as an resilient layer between board and underside of sleepers, then used resilient (vile smelling while wet) carpet glue and water mix to bond the ballast (loco sand with a little black powder paint in it). Made for quiet running and a low ballast profile.