Over time the constant movement of traffic over the track causes gaps to form in the ballast structure known as 'voids'. Often, from the trackside, sleepers can be clearly see bouncing up and down as the wheels pass over them. Excessive movement is dangerous, of course, so the voids need to be filled to give a firm base for each sleeper. This has been done in the past directly by manual labour but today is done by the tamping machine
The tamping machine works by vibrating the ballast and forcing it under the sleeper. These combined actions cause the ballast to form a close matrix which can support the track effectively.
The original Matisa Standard Tamper was totally mechanical with screws providing the in and out movement of the tools and a cam mechanism providing the vibration. Over time some of these these functions were provided by hydraulics.
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This is a standard tamper in Australia. As I remember them, Standard Tampers were more enclosed but maybe this model was made specially for the warmer climate. The man at the controls was actually a fitter at the Adelaide depot. I met him there. He is seated in the travelling position at the rear of the machine, where he could see to drive in both directions. |
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The operator is now seated in the working position where there was an excellent view during tamping. The tamping arms, actuating screws, eccentric bearings for vibration and the flywheels can be seen |
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This is a view of the Standard Tamper from the operating position.Note the very comfortable seat ! The operating levers can be seen at each side. |
"The Matisa
Light tamper BL-09 M"
After the Standard tamper there were a succession
of heavy tamping machines employing a variety of methods of tamping, but all
adhering to the basics of pressure and vibration to move the ballast. And
these machines were made in a variety of wheel gauges and modified where required
for local conditions.
It became apparent that there was a need for a smaller and cheaper machine for small jobs. And so the Light Tamper was born.
We made a considerable number in our Chertsey, UK, factory from about 1956 Starting with our parent company's drawings (metric units and French text) we had to convert to Imperial measurement and source components in the UK as far as possible. Steel and other specifications had to be carefully looked into, but we got there in the end.
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The Light Tamper was intended for working in small sites, such as marshalling yards, although it could also be used anywhere where speed of operation was not the prime consideration. It started as two separate tamping heads on a trolley that was pushed by two operators, but was later used with a motorised trolley. |
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The machine was powered by two diesel or petrol engines, one for each tamping head, but one was also used to provide traction.
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Detail
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| The Light Tamper could be used on secondary track and off-tracked when necessary. |  |
"The
JackPak"
We did
a lot of designing and manufacture at the Chertsey, UK, factory, including
the 'JackPak'. This was a tamping machine designed for high lifting, such
as in laying or relaying track.
The tamping heads were based on the proven Light Tamper heads and it would run in either direction at about 20MPH. Hydraulic power controlled by electronics was used throughout.
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I do believe that's me, over 40 years ago, testing the JackPak on our works track. That track took a hammering! |
| This view clearly shows the sleepers being lifted clear of the ballast while the vibrating tools force the ballast up under the sleeper being processed. The machine was capable of much higher lifts than shown. |  |
Levelling of the track was taken care of by the large oil-damped pendulum at the front of the machine, and a telescope could be used on the targets at the front of the machine to ensure a constant height.
Later tamping machines combined lifting, levelling and aligning functions to enable track to be set geometrically correct before tamping. Of course it still needed human intelligence to programme the machine.
"The
Matisa BNR-60 circa 1960"
These machines moved and stopped at each sleeper to be processed which involved a lot of energy as the machine is first accelerated, then braked. Nevertheless they could tamp sleepers at up to 15 a minute although this slowed to 11 sleepers a minute when levelling and llining were also employed.
Today some machines carry their tamping heads on a constantly moving carriage which cuts out the acceleration and braking. By using two sets of tamping heads on the carriage two sleepers at a time can be processed.
Speed in tamping is important because it allows more track to be processed between trains.
"Stoneblowers"
This is a new concept by a USA company, Harsco Corporation. Nozzles are inserted
into the ballast on either side of a sleeper, the sleeper is lifted slightly
and air is blasted horizontally to blow ballast under the sleeper. It's claimed
to be 3 to 5 time more effective than conventional Tamping. A number of these
machines are in service on British railways and so far 6,500 miles of track
have been processed.
Learn more from the Harsco website . Products and Services > Click on
Stoneblower
Click to download video (190 KB; needs Windows Media-player or similar)
I think it's true to say that the jury is still out on the efficiency of Stoneblower but it's an interesting concept capable of development.
