"Why are Ballast Cleaners needed?"
When a track has been laid for some time, the regular passage of traffic will have eroded the corners of the ballast, and the detritus thus formed will have clogged the ballast, spoiling the drainage and possibly causing the track to become water-logged. In addition, soil from the substratum would have forced its way upwards through the ballast, adding to track deterioration.
Track in this state needs constant attention to keep it within acceptable safety limits and this becomes uneconomic.
One way to remedy this is to dismantle the track and rebuild from scratch, but this is very costly, particularly in these days of continuous welded track and heavy reinforced sleepers. So that's where the Ballast Cleaner comes in. It cuts the ballast from under the track, and processes it before replacing some under the track and rejecting the rest.
"The Matisa Ballast Cleaner 10 CB 5 Circa 1960"
|Working speeds||240 - 300 metres/hour|
|Output||240 - 300 cubic metres/hour|
|Travelling speed||50 km/hour|
|Depth of excavation||240 - 500 mm|
"Using the Ballast Cleaner"
Use of the ballast cleaner could not be undertaken lightly; it had to be planned carefully to ensure minimum disruption to traffic . Work was usually restricted to the hours 11pm Saturday to 6am Sunday.
The first job was to excavate ballast manually from under a couple of adjoining sleepers and slide the cutting bar under the track ready loaded with a length of excavating chain. The cutting bar was essentially a heavy cast steel L-shaped section. The chain faced forward, exposing it to the ballast to be excavated.
Cast steel troughs, with chain already in position were then lowered by hoists from their running positions, bolted to the ends of the cutting bar and the chain connected. It then formed a continuous chain from the turret at the top of the machine, down one trough, across the cutting bar and up the other trough back to the turret.
The chain was composed of heavy cast steel links, each holding two renewable manganese steel pins. In use, as the ballast cleaner moved forwards slowly and the turret moved the chain in the troughs and cutter bar, the pins broke up the compacted ballast and it was moved by the chain along the cutter bar to the side trough where it was elevated to the top of the machine. At the top it was deposited into a hopper for processing.
The chain links were ingeniously designed to form a cutter in the cutting bar and become an elevating chain in the troughs.
"Functions of the machine"
Above is a diagram of the machine. At the rear of the machine was the cab which housed the power unit, hydraulics, electrics etc. and just in front of the cab, high up, can be seen the turret that provided the power to turn the chain. Initially the turrets were powered by electric motor, but were changing to hydraulic motors as more powerful hydaulic motors became available.
There was a difference of opinion as to which was best. The electric turret was harder and could exert more instantaneous force; the hydraulic turret was softer and kinder to job and machine. It did mean that some foreign objects under the track might be bashed out with the electric drive, but would need to be removed manually if the softer drive stalled. I'm talking old bed frames and the like here.
When the excavated spoil reached the turret it dropped into a hopper and from there on to a conveyor belt. At this stage the spoil could be fast-tracked to the distributing conveyor to be deposited in trucks or as a windrow alongside the track.
More usually, it was carried up and deposited on to a vibrating screen. The detritus was dumped as described, but the screened ballast would be put back on the track behind the cutting bar.Later, fresh ballast would be added and a tamping machine would firm up the track.
There were several options available for distribution :-
Screen the excavated material and return to the track all the good ballast immediately behind the excavating mechanism
Screen and return as above all the good ballast, either spread evenly over the formation, or under each rail string or in a windrow.
After screening, return the standard sized ballast directly to the track behind the excavating chain and distribute the smaller ballast over this layer.
Discharge the spoil from the front of the machine in order to free the track behind the ballast cleaner for re-ballasting and tamping operations.
- Excavate all the material in the ballast bed without screening
Attempts have been made to make smaller ballast cleaners, but as the track is unusable while the work is going on, the greater the output the better, certainly for main line track, and this means large machines.
I saw a small ballast cleaner in New Zealand, but I don't recollect much about it now. I believe it worked from the cess side only and the spoil was removed entirely from under the track for separate processing.
Has anyone seen anything like this?