[alma-config]Transporter and Road Interface message from M. Kraus

[awootten at nrao.edu]

ALMA Project

Interface between 
the ALMA antenna transporter 
and 
Roads for antenna transport on the ALMA site

M.Kraus 	13-Dec-01


The following data and requirements have been assumed for the concept
studies and 
draft specification of the ALMA Antenna transporter, furthermore some 
characteristics of the transporter relevant for the road construction
are given.


Basic assumptions

Due to the high loads, large required road width and length of the road
network it is 
assumed that road pavement is not feasible, mainly for cost reasons.
Road constructions and vehicles used in neighbouring Chilean open pit
mines shall be 
copied and adopted to the needs of the ALMA. 
In this way the project can profit from the experiences and
infrastructure available in 
the area and a well-tested and robust transport system can be expected.

Longitudinal Road gradient (Slope)

A maximum road slope of 10% is preferable for the design of the
transporter and for 
operational safety. If absolutely required by the terrain a maximum road
slope of 12% 
shall not be exceeded  The slope in curves shall be smaller.
Hills or depressions shall have a radius > 50 m
When approaching an antenna station the last 50 m of access road shall
be straight 
and have a slope of maximum 2% .

Lateral slope
Due to the high center of mass a lateral road slope of 3% shall not be
exceeded. 

Road profile
The road profile shall be compatible with the following: The transporter
shall have a 
ground clearance of 250mm for 2m track width, or 500 mm for 5 m track
width.

The usable road width shall be 9m or more for straight road sections and
more in 
curves. At a height of 1 m above road level a free width of 12 m shall
be provided, 
and at 3m above ground the free width shall be 16 m  or more.

Driving speed
A driving speed up to 20 km/h loaded, and 50km/h unloaded is the goal,
to achieve 
the required antenna transport rates. The road shall be smooth enough to
avoid 
excessive oscillations of the antenna on the transporter.
Driving over a 100mm step across the road has been assumed as limit for
preliminary 
dynamic calculations and may serve as an upper limit for the required
road 
smoothness.

Curves

A minimum curve radius of 30 m shall be considered. The side slope in
the curves 
shall not be higher than on straight roads.

Vehicle characteristics

Several transporter concepts have been developed.
The Fork-lift type transporter is based on a mining dump truck chassis
with a 
maximum weight (GVW) of ca 400 to using tyres of size 40R57 or similar.
Other concepts use standard heavy duty towing trucks (8x8, GVW ca 50 to)
and 
multi-axle trailers or semi-trailers with an axle load of up to 30 to
and tyres 285/70 R 
19,5.