No subject

at the surface) has a radius of about 6m, and then the transporter 
wheel has a 1m clearance to this base - but what happens 
to the pad foundation underground??  Is the radius of the foundation 
bigger - in this case a moving transporter could exert a torque on the 
foundation. Will this cause movements  or even put a significant
load on the foundation, influencing its cost and construction?


5) Cost of Conduit Crossing points

Again it was  suggested that the number of road/conduit 
crossing points be minimised because of the need to reinforce 
them. Again it would be nice to have costs on these to decide 
how important it is to minimise these - another question for
our civil engineers.


6) Guiding into pads

At our meeting methods of guiding the transporter to the
pad in the compact confiburation were discussed - using
mm radars (out of the question!!) and laser systems.
A consequence is that there would only be one (at most two
ways) to approach each pad.

At the configuration group telecon meeting
a suggestion was made about whether we have considered   
a railway system for getting antennas into the compact  
array. In addition to guidance rail track could help bear the
weight of the antenna. I guess having two systems (trucks for
the larger  arrays and a railway for close in) is just too
expensive??  Maybe though one could have in the central 
array  a central (non-load bearing)
'guide rail' for the  trucks, maybe a mechanical solution
to guidance would be useful in addition to laser
systems.


7) Time for reconfiguration

 This does not seem to a critical issue in deciding the 
transporter concept except in terms of the overall 
transporter speed. The baseline loaded speed for the mining truck 
of 20km/hr is OK. Going below 15km/hr has implications for the rate
of reconfiguration possible to the largest arrays.

 I have been studying the timeline document Max left with me
on the scheme for reconfiguration using 2 transporters
which then gives a total of  4 moves per work day (i.e.
2 moves/antenna/day). This scheme  assumes 1 hour transporter 
driving  time (or 20km if the desired loaded speed or 20km/hr is 
achieved). This rate is probably OK for intermediate configuration
but a rate double this might be desirable in the most compact 
arrays. The estimate 2ant/tran/day  seems like a pessimistic assessment 
to some in the configuration group - we need to discuss
it - I  give more details of Max's  scheme in a subsequent 
email.


8) Memo/Project Book entry  on Transporter concept

I think the Auto-CAD drawings of antennas/transporters
that Max left me could 
usefully included in a one or two page ALMA memo - it 
would be very useful for the whole project to see them (and
of course I'll show them at ALMA week). The antenna 
people need to know what must be left free of obstructions.

The same drawings  should also be
in the project book - we have to decide if transporter stuff
goes in the Antenna or Configuration chapters- probably 
Antenna?? since the present limited information on transporter
spec is there.
 

9) Pad Mask Geometry 

I've been pursuing a road-mask first approach to the compact 
array as suggested by the configuration CDR comments.
Given the drawings Max left me I've been  working on the 
exact implications for the antenna mask for array optimisation. 
The mask shows where antennas centres can and cannot be placed,
the exact shape of the mask, particularly at corners
where radial and azimuth access routes meet is tricky but I think 
I now understand  it  and will send out a document in a few days. I 
estimate in fact for two roads crossing at right angles the 
radius of curvature added at the corner is about 3m-4m
or so, which I think is less than what Leonia Kogan assumed.  
This information  is  being incorporated into my MATLAB 
configuration design tool.


10) Compact array Design Progress


I the last two weeks I have been playing with different geometries
of road net for the compact array, and creating software doing shadowing
calculations and  to allow the sharing of pads  between round and N-S
elongated  arrays. I hope to post some things on the web by the end of
this  week. The idea is to get to a starting geometry which will
finally optimised by the uv and beam optimisation tools we
have.

In terms of road geometry, I have found that one can use 
one azimuthal road rather than two in the Kogan design and having 
radial access roads not 180 apart improves the beam. The beam 
improves further if one uses a triangular geometry rather than
a circular one for the compact array. This also allows
road nets with access to all antennas without driving over pads
and shorter transporter travel distances within the compact 
array.


      John