Lamp Bracket – Part 1

Building the Lamp Bracket Model

Open your titleblock and change to the appropriate layers as needed.

Begin the Lamp Bracket by drawing the outline.  

Change the Workspace to 3D Modeling (bottom right toggle button).

image006.jpg

Select the Front top right corner to rotate the object as shown below.

Before you can extrude these 6 objects (3 arcs and 3 lines) into a solid object, you need to change them into one polyline.

  • Select the MODIFY pull-down menu then POLYLINE (or type in PEDIT) then select one of the 6 objects.
  • The command line will state, “Object selected is not a polyline”
  • Hit enter to respond Y (yes) to the question “Do you want to turn it into one?”
  • Then type in “J” (no quotation marks) to JOIN the objects into one polyline.
image012.gif

Select the EXTRUDE  command and then select the polyline you just created.

 

Type in the height, as per the drawing and hit enter to give taper angle of 0 degrees. 

Next you will draw the large cylinder.

  • Switch from the Home tab to the Solids tab  
 CYLINDER

CYLINDER

 CENTER

CENTER

  • From the Primitive panel select the CYLINDER command and then with the CENTER  Osnap on select the lower center point of the extruded base.
  • Then select the edge of the arc or enter the radius of the cylinder.
  • Lastly enter the height of the cylinder.

To see this object more clearly you will next shade it.

  • Switch to the Home tab and under the VIEW panel change from the 2D Wireframe to Shaded mode.
 2D Wireframe Mode

2D Wireframe Mode

  • Try each of these out to see what they do, then return to the 2D Wireframe mode .

This object is made up of 2 solid objects (the extruded polyline and the cylinder).

To make this into one object we need to UNION them together. 

 UNION 

UNION 

  • While in Home panel under the Solid Editing tab or in Solid panel under the Boolean tab select the Union  command and then select both of the solid objects to make them one.

Now continue drawing in the rest of the cylinders by drawing the circles, extruding them and moving to the proper locations.

  • The inner green and cyan cylinders are the size of the holes and will be subtracted (see next step) out to create the holes.
  • The dark blue cylinder is the size of the counter bore which is first create at the bottom then moved up to its final position and subtracted out.
 SUBTRACT

SUBTRACT

This time instead of using UNION use the SUBTRACT command

  • To use SUBTRACT first select the object to subtract FROM (the main shape), then select the object to subtract (the cylinders).
  • For the countersunk holes just draw the cylinders for the holes and subtract them from the object; the next steps will explain how to chamfer the holes.

Under the Solid Editing panel select the Chamfer Edge icon.

  • Enter “d” to select Distance.  Then enter “5” for Distance1 and Distance2. 
    • The hole diameter is 10, the countersink diameter is 20 and countersinks are at 45o therefore it is 5 over and 5 down for the countersink.
  • Select the top of each hole to be chamfered. Then right click to accept.

To create the wedge is a little tricky.  

  • In the Solids tab under the Primitives panel select the Wedge icon.
  • Then using the Quadrant Osnap select the midpoint of the cylinder as shown below.
  • Then select “L” to select Length and input the base length of the wedge.
  • Next input the width of the wedge.
  • Lastly input the height of the wedge.
  • This creates a wedge but it is off to one side and needs to be center --- see next step.
 TOP VIEW

TOP VIEW

On the VIEW toolbar select the TOP VIEW icon to orient the drawing looking from the top.

Move the wedge from the center to the edge to center it.

  • Notice there is a gap between the wedge and the cylinder, the next step will correct this.
 BOX

BOX

To fill the gap you will create a BOX  from the SOLIDS toolbar.

  • Create box from one corner of the wedge and then specify the box size as @-3,10 (the –3 will give it thickness to fill the space and the 10 is the same thickness as the wedge). 
  • Then specify the height of 40 (this is the same height of the wedge).

Select the UNIONcommand and then select the base, wedge and box objects to make them all one.

Calculating the Weight of the Lamp Bracket

Important information may be extracted from the solid model to be used for design and analysis purposes.  This information in the form of calculations is illustrated below and is obtained when using the “Massprop” command (Mass Properties).  

Calculate the Weight of the Lamp Bracket (see below)

  • If the Lamp Bracket was built in Iron = _______
  • If the Lamp Bracket was built in Aluminum = _______

Type your answers on to your drawing in layout view (Paper Space) then print out and submit for marking

image078.jpg

Print out in SE Isometric View

 

The mass is given for a material with a density of 1.0 (water).  To calculate the weight of the object in grams you multiply the volume of the object x the density (in g/cu cm)

Density of :      Iron = 7.86 g/cu cm    Aluminum = 2.7 g/cu cm

  • Your object is in millimeters therefore to calculate the weight of the object you must change the density to g/cu mm
  • 1000 g/cu cm = 1 g/cu mm
  • Therefore:  Weight = Volume x Density ¸ 1000   

(Where the object is in millimeters, Weight is in grams, and Density is in g/cu cm)

Your Mass Properties should be the same as the following:

---------------- SOLIDS----------------

Mass: 246110.3468

Volume:246110.3468

Bounding box:X: 94.3421--244.3421

 Y: 82.1106--212.1106

 Z: 0.0000--55.0000

Centroid:X: 172.7922

Y: 147.1106

Z: 13.9582

Moments of inertia: X: 5606224524.1522

Y: 7875529732.1747

Z: 13304985824.5779

Products of inertia:XY: 6256018960.5105

YZ: 505361114.3200

ZX: 522865972.5803

Radii of gyration: X: 150.9282

 Y: 178.8854

 Z: 232.5103

Principal moments and X-Y-Z directions about centroid:

 I: 219893919.0385 along [0.9855 0.0000 -0.1697]

J: 479426479.3216 along [0.0000 1.0000 0.0000]

K: 642802916.0872 along [0.1697 0.0000 0.9855]