[alma-config]Transporter concepts

[Al Wootten]

Hi Mel and David

Thanks for your comments on the transporter concept.  Remember that this
is one of several concepts; the realistic animation may have given the
concept more definiteness than it presently has.  I think that several of
your questions were answered in the presentation Max Kraus gave; I am
unaware of a detailed writeup of this concept at present but one will be
available very soon.  The Antenna IPT has put the presentations on the
web e.g.
(http://almaedm.tuc.nrao.edu/forums/alma/dispatch.cgi/almaprojmeetings/folde
rFrame/100351/0/def/0333).

As I understand the concept, it grew out of designs for mining trucks
commonly used in this part of Chile, to ensure availability of parts and
that the design was workable.  I believe that one of the designs allowed
minimal travel over the pads and that that is basis for the present concept.
A backup concept is based on mining dumptrucks; that concept is thought to
result in a heavier and more costly vehicle.   Driving
over the pads is indeed part of the specification for the pads.  However a
lighter vehicle which need not drive over the pads has its charms.
Specifications for the roads are part of the transporter design.

Max Kraus did present a detailed design for how the transporter would
be able to retrieve any antenna in the compact configuration.  The
compact configuration which he used differed only slightly from that which
Conway presented to the JAO; differences are being resolved.  As an
antenna is moved from the center to the outside of the compact array,
antennas on the periphery of the road are steered to point away from the
road and locked locally until the operation is over.  Clearance as presented
in the review is 1.2m on either side.  Guidance is achieved by GPS
measurements
according to my notes to 10cm (used commonly on farm equipment today) but
pathlines and TV monitoring would I presume also be used in the compact
array.
The transporter cabin will be oxygenated.

Kraus spent some time addressing transporter stability.  Each of the
eight front tires bears 18 tons weight and the two large rear ones 52 tons
(the latter cost $25K each!).  According to my notes, the design should
ensure stability in the event of hydraulic system failure.
A finite element analysis of the structure was performed; I suspect that
tire failure has been examined.  A protective structure is planned for
construction at Chajnantor near the AOS to secure the vehicle and its tires
from exposure.

Kraus also detailed crew size under several assumptions about
reconfiguration
and defined their actions in half hour segments during reconfiguration.

The planned schedule for this concept to become a real design is:
Study to industry 31 Jan 2003
            CDR July 2003
            Contract 2004.
            At OSF 31 Dec 2005
            Second 15 Sept next year.

Clear skies,
Al