DP Tool Club 14/CD_ASCQ_14_0694.iso/news/4544/mcad_int.txt

Text File | 1994-03-23 | 6KB | 130 lines

INTRODUCTION TO THE MECCAID LIBRARY

The Meccaid library has been created with an Isometric 0.25" grid as the
basic grid setting, using an imperial scale.

The drawings of the parts are based on a sample of genuine Meccano parts
taken from the author's collection. With so many part variants produced over
the years, there has had to be a compromise. For example, the larger strips,
(7.5", 9.5" and 12.5" strips) as well as having varying thicknesses, also
have ends that vary between half round and semi circular. In the Meccaid
library, therefore, parts have been given 'standard sizes' using the
following parameters.

Strips, angle & flat girders    .030"
Curved strips, flat plates      .030"
Braced girders                  .020"
Flexible plates                 .010"
Spur gears                      .060"
Large circular parts            .050"

They have also been set up so that overlapping parts will 'fuse' into each
other. If parts separation is required, then the part will have to be moved
by the appropriate amount.

When the library is installed, it will be seen that, in general, each part
is located in a separate file, the name of which will be the Meccano part
number, preceded by a five and a series of zeroes. Thus, for example,
file 50006A.TVL will contain the 1.5" strip and various nuts and bolts.
However, some parts fell naturally into a combination library and these
parts are identified with a file name ending in a 'Y' or 'Z'. An example is
the 1" pulley, with and without boss. These parts are contained in the one
file 50022Z.TVL. It will be found therefore, that parts requiring a boss,
such as pulleys, gears, etc. will have the part drawn without the boss, the
boss being contained within the library.

When the boss and part have been placed in the drawing, the two parts can be
selected and grouped together to create a single part.

In the interests of storage requirements, each library contains the minimum
number of projections, from which it should be possible to obtain any other
projection using the library 'rotate' facility, or (in the case of nuts and
bolts) by the 'Y' reflection after placing the part on the page.

If this is found to be inconvenient, and storage is not a problem, then
once the part has been rotated and reflected to its desired position, then
the part can be stored back into the library, using the READ SYMBOL FUNCTION
from the LIBRARY MENU. The library must, of course, be saved afterward!

Again, if a large amount of memory is available on your PC - greater than
4Mb - then it may be found more convenient to create a multiple part library.
As each library can contain up to 900 symbols, then it is quite feasible to
create multiple part libraries, although it must be remembered that on
loading the library, it will need to share the available RAM with that
required for the drawing.

When a part is selected in the library, the preview window will have a
small blue dot, usually located at the centre of the part. This represents
the anchor point of the part - the point that was selected when the part was
stored in the library. It also depicts the anchor point of the part when
placing it on the page. On selecting the part from the library, a red
rectangle will depict the area of the part and the crossover position of
the cursors will indicate the actual anchor point of the part. It is this
anchor point, and the isometric grid locking, that ensures that line up of
the parts is both easy and convenient.

A simple regular part, such as a strip, requires only the one basic
projection, although for convenience, the 'Y' reflection is also contained
within the library. However, the more angular parts require more than one
projection. Angle girders, for example, have eight projections. From these
eight, it is possible to obtain any of the twenty four possible projections
of the part in question.

The files on this Meccaid demonstration disk contain a suitable selection
of parts that enable simple models to be 'constructed'. The selection also
contains extracts from the main library of spur gears so that some
experimental gearboxes can be built. The gears included enable ratios of
1:1, 2:1 and 3:1 to be obtained at the standard Meccano spacing of 0.5".

The sample drawings and settings included on this disk are:

GIRDERS.MPG     Displays how the 24 required projections can be obtained
                from the 8 contained within a library.

TRUCK.MPG       A small 6-wheeled modern tractor unit. There are sufficient
                parts on this disk to enable it to be rebuilt.

STER_BOX.MPG    The main steering, clutch and brake mechanism from the
                Author's Midland Red S15 bus (Available as a Modelplan from
                M.W. Models of Henley-on-Thames). This demonstrates how the
                layer function of TSCAD can be put to good use in designing
                complicated mechanisms.

COLORS.MPG      A simple drawing that shows the advantages of the colour
                libraries, available in current French yellow, blue and
                silver; and in the Liverpool mid-50's colours of medium
                red and green.

On installation, the drawings will be placed into a subdirectory \MECCAID
of the TSCADRAW\DRAWING directory and the libraries will be placed in a
similar subdirectory in the TSCADRAW\LIBRARY directory.

The storage requirements for the contents of this disk are:

        36 Library files:       1.38Mb

        8 Drawing files:        745Kb

The complete MECCAID package (compressed onto 5 high desnity disks!) contains
hundreds of symbols for (almost) all of the parts available in the Meccano
construction  system, and a 36 page user guide. Additional colour libraries are
also available. See the file ORDERFRM.TXT for ordering information.


                The Meccaid library is (c) Roger Wallis - 1994