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<DIV><FONT face=Arial size=2>It appears to me that a large emphasis for
the</FONT></DIV>
<DIV><FONT face=Arial size=2>transporter design has been to avoid
driving</FONT></DIV>
<DIV><FONT face=Arial size=2>over the pads. This leads to a very
challenging</FONT></DIV>
<DIV><FONT face=Arial size=2>design problem.</FONT><FONT face=Arial
size=2> It looks like the pistons</FONT></DIV>
<DIV><FONT face=Arial size=2>in the design concept I saw will have
forces</FONT></DIV>
<DIV><FONT face=Arial size=2>in excess of one million pounds when
lifting</FONT></DIV>
<DIV><FONT face=Arial size=2>the antenna off the pad or out of the
back</FONT></DIV>
<DIV><FONT face=Arial size=2>of the transporter. Lateral stability also
</FONT></DIV>
<DIV><FONT face=Arial size=2>looks problematic at the peak of the
lifting</FONT></DIV>
<DIV><FONT face=Arial size=2>stroke. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Large numbers of ganged wheels</FONT></DIV>
<DIV><FONT face=Arial size=2>work well for distributing loads on flat
paved</FONT></DIV>
<DIV><FONT face=Arial size=2>roads, but it is difficult to build a
suspension</FONT></DIV>
<DIV><FONT face=Arial size=2>system that does a good job of distributing
</FONT></DIV>
<DIV><FONT face=Arial size=2>the load on kinds of</FONT><FONT face=Arial
size=2> roads ALMA is likely</FONT></DIV>
<DIV><FONT face=Arial size=2>to have. A lot of construction and
maintenance</FONT></DIV>
<DIV><FONT face=Arial size=2>costs can be saved if the transporter
can</FONT></DIV>
<DIV><FONT face=Arial size=2>use less than perfect roads, if only
at</FONT></DIV>
<DIV><FONT face=Arial size=2>slow speeds.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I thought driving over the pads was
explicitly</FONT></DIV>
<DIV><FONT face=Arial size=2>part of the pad design specifications.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>A cantilevered lifting vehicle will
actually</FONT></DIV>
<DIV><FONT face=Arial size=2>exert about four times more local
ground force </FONT></DIV>
<DIV><FONT face=Arial size=2>than a </FONT><FONT face=Arial size=2>vehicle that
surrounds the antenna</FONT></DIV>
<DIV><FONT face=Arial size=2>and drives over the pad. It is the
local</FONT></DIV>
<DIV><FONT face=Arial size=2>ground pressure that dictates the number
and</FONT></DIV>
<DIV><FONT face=Arial size=2>size of the tires and the road
bed </FONT><FONT face=Arial size=2>design near the </FONT></DIV>
<DIV><FONT face=Arial size=2>pads. </FONT><FONT face=Arial size=2>All
existing reconfigurable arrays </FONT></DIV>
<DIV><FONT face=Arial size=2>I am aware of </FONT><FONT face=Arial size=2>have
transporters that drive</FONT></DIV>
<DIV><FONT face=Arial size=2>over, or at least straddle, the
pads. This</FONT></DIV>
<DIV><FONT face=Arial size=2>has not caused any problems that I am </FONT></DIV>
<DIV><FONT face=Arial size=2>aware of.</FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>********************************************<BR>|
David
Woody
<BR>| Assistant Director of Instrumentation <BR>| Owens Valley Radio
Observatory <BR>|
Caltech
<BR>| P.O. Box 968, Big Pine, CA 93513 <BR>| phone
760-938-2075ext111
<BR>| <A
href="mailto:dwoody@ovro.caltech.edu">dwoody@ovro.caltech.edu</A>
<BR>********************************************</FONT></DIV></BODY></HTML>