BT-105 Engineering Graphics - Dec 2024 Question Paper

Under each question, How to answer lists the points an answer should cover, outlined by CampusPrep from the syllabus. Check the details against your textbook.

1. 7 Marks
   aThe distance between two stations is 100 km and on a road map it is shown by 30 cm. Draw a diagonal scale and indicate 46.8 km and 32.4 km on it.
   How to answer

   • Calculate Representative Fraction: $\text{R.F.} = \frac{30\text{ cm}}{100\text{ km}} = \frac{30}{100 \times 10^5} = \frac{3}{10^6}$
   • Assume maximum length to be measured (e.g., $50\text{ km}$ or $60\text{ km}$) and calculate length of scale (LOS)
   • Construct main scale and sub-divisions (units of 10 km, 1 km, and 0.1 km)
   • Construct diagonal scale grid for tenths of kilometers
   • Mark distances: 46.8 km and 32.4 km
2. 7 Marks
   bDraw an epicycloids, given that radii of generating and directing circle as $r = 20\text{ mm}$ and $R = 72\text{ mm}$ respectively. Also draw a normal and tangent at any point on the curve.
   How to answer

   • Calculate subtended angle: $\theta = \frac{r}{R} \times 360^\circ = \frac{20}{72} \times 360^\circ = 100^\circ$
   • Draw directing circle arc of radius $R = 72\text{ mm}$ subtending $100^\circ$
   • Divide the rolling circle ($r = 20\text{ mm}$) and center line arc into equal number of parts (e.g., 8 or 12)
   • Trace the locus of the generating point on the rim to form epicycloid
   • Construct normal and tangent at an arbitrary point on the epicycloid
3. 7 Marks
   aA thread is unwinds itself from a cylindrical drum of 60 mm in radius. Draw the locus of the free end of the thread for unwinding through an angle of $180^\circ$.
   How to answer

   • Recognize locus as the involute of a circle
   • Calculate circumference length for unwinding $180^\circ$: $L = \pi \times r = \pi \times 60 \approx 188.5\text{ mm}$
   • Draw semi-circle of radius $r = 60\text{ mm}$ and divide into equal divisions (e.g., 6 parts)
   • Draw tangents at each division point
   • Measure lengths corresponding to unwound arc lengths along each tangent to plot points
   • Join points smoothly to get the required locus
4. 7 Marks
   bDifferentiate between the first angles and third angles projection.
   How to answer

   • Define placement: Object lies between observer and plane (First angle) vs plane lies between observer and object (Third angle)
   • Planes nature: Opaque (First angle) vs Transparent (Third angle)
   • Relative view positions: Plan is below elevation in First angle; plan is above elevation in Third angle
   • Left/right view placements
   • Draw standard projection symbols for both methods
5. 7 Marks
   aA line AB 120 mm long is inclined at $45^\circ$ to HP and $30^\circ$ to the VP. It's midpoint P is in VP and 20 mm above HP. The end A is in the third quadrant and B is in the first quadrant. Draw the projections of the line AB.
   How to answer

   • Locate midpoint projections: $p'$ is 20 mm above $XY$, $p$ is on $XY$
   • Determine segment lengths from midpoint: $AP = PB = 60\text{ mm}$
   • Draw true inclinations $\theta = 45^\circ$ and $\phi = 30^\circ$ through midpoint with $B$ in 1st quadrant and $A$ in 3rd quadrant
   • Establish loci of endpoints $a', b'$ and $a, b$
   • Rotate and project to find the front view $a'b'$ and top view $ab$
6. 7 Marks
   bExplain layering concept with examples. How is it implemented in CAD software?
   How to answer

   • Definition of layers as transparent overlays used to organize drawing entities
   • Key properties controlled by layers: color, linetype, lineweight, visibility (on/off, freeze/thaw, lock/unlock)
   • Examples of standard CAD layers: Dimensions, Centerlines, Hidden lines, Text/Notes, Object lines
   • Implementation steps in CAD software (e.g., AutoCAD Layer Manager dialog, creating/modifying layers, assigning entities to layers)
7. 7 Marks
   aDraw the projections of a regular hexagon of 25 mm side having one of its sides in the H.P. and inclined at $60^\circ$ to the V.P. and its surface making an angle of $45^\circ$ with the H.P.
   How to answer

   • Stage 1: Assume hexagon resting completely on HP with one side perpendicular to VP; draw true shape in top view and line in front view on XY
   • Stage 2: Tilt the surface at $45^\circ$ to HP, maintaining resting edge on HP; project new top view
   • Stage 3: Rotate the resting side in top view to be inclined at $60^\circ$ to VP; project final front view
8. 7 Marks
   bDraw the projections of a rhombus having 100 mm and 40 mm long diagonals. The bigger diagonal is inclined at $30^\circ$ to H.P. with one of the end point in H.P. an the smaller diagonal is parallel to both the planes.
   How to answer

   • Stage 1: Place rhombus in HP with major diagonal parallel to VP and minor diagonal perpendicular to VP (or vice versa) to get true shape in TV and line on XY in FV
   • Stage 2: Tilt the bigger diagonal at $30^\circ$ to HP keeping one end in HP
   • Since the smaller diagonal remains parallel to both HP and VP, its front view and top view are parallel to XY line
   • Project the resulting top and front views
9. 14 Marks
   A right pentagonal prism 90 mm high with each side of the base 30 mm is resting on one of the base edges on the horizontal plane and inclined at $30^\circ$ to V.P. and the face containing that edge is inclined at $45^\circ$ to the H.P. Draw the projections of the pentagonal prism.
   How to answer

   • Stage 1: Simple position with axis perpendicular to HP and base on HP; draw pentagon in TV and rectangle in FV
   • Stage 2: Tilt the prism so that rectangular face containing the resting edge is inclined at $45^\circ$ to HP; project TV
   • Stage 3: Rotate the resting edge in TV to make an angle of $30^\circ$ with VP; project final FV
10. 14 Marks
    A right regular cylinder 50 mm diameter of base and 65 mm long lies on one of its generators, on the H.P. with its axis inclined at $30^\circ$ to the V.P., cuts the cylinder and bisects its axis. Draw the apparent and true sections of the solid.
    How to answer

    • Draw projections of the cylinder lying on a generator in HP with axis inclined at $30^\circ$ to VP
    • Establish section plane bisecting the axis
    • Determine the points where cutting plane intersects generators/base circles
    • Draw sectional top view/front view (apparent section)
    • Project true shape of section on an auxiliary plane parallel to the cutting plane
11. 7 Marks
    aA right cylinder of 30 mm diameter and 35mm height of axis, inclined at $30^\circ$ to H.P. and passes 18 mm from base along the axis. Draw the development of the truncated cylinder.
    How to answer

    • Draw elevation and plan of cylinder ($d = 30\text{ mm}$, $h = 35\text{ mm}$)
    • Draw cutting plane inclined at $30^\circ$ to HP, passing through axis at 18 mm from base
    • Divide circle into 12 equal parts and project generators to cutting plane in front view
    • Calculate stretch-out perimeter length: $L = \pi D = \pi \times 30 \approx 94.25\text{ mm}$
    • Transfer true lengths of each cut generator onto the developed rectangle and connect smoothly
12. 7 Marks
    bA square pyramid rests centrally over a cylindrical block. Draw the isometric projection of the arrangement. Consider the pyramid has a base with 25 mm side and 40 mm long axis whereas the cylindrical block has a base with 50 mm diameter and 20 mm thickness.
    How to answer

    • Construct isometric scale (or use isometric length factor $\approx 0.816$)
    • Draw isometric projection of the cylindrical slab ($D = 50\text{ mm}$, $t = 20\text{ mm}$) using four-center method for top and bottom ellipses
    • Locate center of top face of the cylinder
    • Construct isometric projection of square base of pyramid ($25 \times 25\text{ mm}$) centrally on the top face
    • Locate apex 40 mm vertically above the center along isometric axis and join apex to base corners
13. 14 Marks
    Write short notes on the following (any two) : i) Modify commands ii) Building Information Modeling (BIM) iii) Isometric and orthographic projection
    How to answer

    • Modify commands: Explain key CAD modify tools such as Move, Copy, Rotate, Scale, Trim, Extend, Fillet, Offset, and Mirror
    • BIM: Explain Building Information Modeling as a 3D model-based process for architecture, engineering, and construction planning/management
    • Isometric vs Orthographic: Compare 3D axonometric view with foreshortened axes vs multi-view 2D perpendicular projections (plan, elevation)