[alma-config] Transporter issues

Tue May 15 13:49:50 EDT 2001

In memo 320, I included a brief discussion of accessing inner antennas in
the compact configuration.  At the time, no explicit consideration 
of the pad size was was given as Peter Napier and I looked at mainly
the dimentions of the transporter.  Given the strong scientific
reason to pack the antennas as closely as possible, it would make
sense to design the transporter and pads to accomodate this primary
goal.  Then, the the primary consideration again becomes the
minimun antenna separation given by 1.3D.  Certainly accessing
antennas in the inner pads is a major challenge, and I had incorporated
several "gates" in my compact configuration design.  I had also
considered some temporary pads as accessing some of the inner pad
antennas may be best done by moving one or more outer ring antennas.
Given the challenges of operating at high altitudes, having a detailed
access plan to every single one of the pads (with X's and O's as 
in calling a football play) will be an extremely good idea.

					-- Min

-----------

Min S. Yun				e-mail: myun at astro.umass.edu
Assistant Professor			phone:  (413) 545-2215
Astronomy Department			FAX:    (413) 545-4223
University of Massachusetts             http://www.astro.umass.edu/~myun
Amherst, MA 01003

On Tue, 15 May 2001, Al Wootten wrote:

> This email was in my box when I returned, and did not propagate to the list.
> 
> Al
> 
> Date: Fri, 11 May 2001 12:05:15 +0200
> From: Maximilian Kraus <mkraus at eso.org>
> Organization: European Southern Observatory
> X-Mailer: Mozilla 4.75 [en] (WinNT; U)
> X-Accept-Language: en
> MIME-Version: 1.0
> To: Leonia Kogan <lkogan at zia.aoc.NRAO.EDU>
> CC: torben.andersen at astro.lu.se, alma-config at zia.aoc.NRAO.EDU,
>         pnapier at zia.aoc.NRAO.EDU
> Subject: Re: move antennas starting from
> References: <200105101809.MAA19842 at bonito.aoc.nrao.edu>
> Content-Type: text/plain; charset=us-ascii
> Content-Transfer-Encoding: 7bit
> 
> Hallo Leonia,
> 
> I cannot definitely say, if 15 m bewteen antenna pads is enough for passing through,
> because I have no drawings of the US antenna foundations.
> The transporter transporter concept I'm working on has a vehicle width of 7.3 m, and
> we should specify a width limit at 7.5 or 8m.
> The foundation of the EU antenna has a diameter of 6m(t.b.c.) , leaving a gap of 9m
> between 15m spaced pads, that's o.k.
> The US antenna foundation has a diameter of 11m(t.b.c.) leaving a gap of 4m which is
> too small. But this dimension just is taken from an assembly drawing and is not
> confirmed.
> 
> If we allow to drive over pads there is no limitation, and your proposed sequence is
> o.k., in fact antenna removal can start from almost anywhere.
> 
> The R150_NOROAD.6 configuration provides enough removal pathes with a minimum
> distance between antenna pads of ca 18m. Critical, but possible  are antennas 24 and
> 25.
> 18m minimum gap would require a max pad diameter of 9m, assuming a vehicle width of
> 7.5m and 1.5 m safety margin.
> Consequent removing from inside out is not possible. e.g. 33 needs to go between 57
> and 58.
> 
> I'm working also on an alternative transporting concept using adapted cranes and low
> loaders. That concept has a width < 4m, but has some drawbacks (cost, more time
> needed etc).
> 
> Is there a specific operational or scientific advantage of the concept 'eating
> antennas from inside'?
> How/when to address the problem of access to a broken antenna? If we don't have good
> access (e.g. removing/exchange  possible within one work-shift) we have to adapt the
> maintenance philosophy accordingly. Presently we prepare for easy and quick
> transport of antennas to OSF, to reduce the work at high altitude.
> 
> max
> 
> Leonia Kogan wrote:
> 
> > Hi Max,
> >
> > Thank you very much for your response.
> >
> > I'd like to clarify my idea of eating the configuration from inside.
> > First of all I want to lay aside the problem of repair of antennas.
> > I have excluded the requirement o to have an access to any antenna at any time.
> > Let me discuss this requrement later.
> >
> > Now lets consider the R150_NOROAD.6 configuration specifically.
> > I do not consider the two circles as roads. I consider only one road (30m width)
> > leading from the right to the inner antennas 1, 6.
> >
> > I see the following sequence of the antenna transporting:
> >
> > 1. Got to antenna 1. I think(?) there is a good access to the antenna 1.
> >    take it and remove it.
> > 2. Do the same job with antenna 6
> >
> >    Now we have pads 1 and 6 without antennas and the spase between the
> >    centers of the pads 1 and 6 >=15m
> >    Here is the crucial point: Is this space enough to pass transporter
> >    with antenna. I thought it is enough. If not the following does not work.
> >
> > 3. Pass through the gate between the pads 1-6 to the center and pick up
> >    the antenna 3. Return back with the antenna 3 passing through the gate
> >    between the pads 1-6.
> >
> > 4. Repeat the item3. with antenna 4, 2, 5
> >
> >    Now have the six inside pads without antennas. The distance between
> >    the pads is >=15m. Again if this space is enough to pass
> >    transporter with antenna, we can get the access to the antennas of
> >    the second circle passing between the epty pads of the inner circle.
> >
> > 5. Having finished the second circle we have epty pads of the second
> >    circle and can start removing of antennas of the third circle.
> >    (again if the space 15m between the empty pads is  enough to pass
> >    transporter with antenna)
> >
> > An so on.
> >
> >    So the crisial point is:
> >
> >    Is the space 15m between the empty pads enough to pass
> >    transporter with antenna?
> >
> > Thank you
> >
> > Leonia
> >
> 