Cowling

Having completed the production of the timber top and bottom plates for your Sustainable Tea-Light Lantern we will now change materials and make the Cowling for your project. 

A cowl or cowling refers to a cover and was first mentioned around 1300 AD as to a hood that monks wore. Cowls can be seen  today as a cover for aircraft engines, outboard motors, most motor vehicles and on top of chimneys. Each cowling is designed to assist with airflow, weather protection and stopping objects from harming the motor. Airflow over an engine helps with cooling while a cowling on a chimney assists the efficient burning of the fire.

Your teacher will give your a rectangle of galvanised sheet metal that you will work upon to create a cowling for your Sustainable Tea-Light Lantern project for this term. Check that your material is 80mm wide and 150mm long.

Steps of Production - Marking out (part 1)

Step 1 -  Using the Permanent Marker with a “chisel point tip” draw a line the width of the tip (thick blue line) around the perimeter of your material.

Step 2 -  Align the 10mm mark of your rule with the lower right hand edge of your material and scribe line along the end of your rule (red line)

Step 3 -  Repeat Step 2 at the Upper Right Hand corner at also the Upper left and lower left corners (shown as red lines)

Step 4 -  Align the 10mm mark of your rule with the lower left hand edge of your material and scribe line along the end of your rule (green line)

Step 5 -  Repeat Step 4 at the Upper Left Hand corner at also the Upper right and lower right corners (shown as green lines)

Step 6 -  Locate the tip of your centre-punch on the intersection of the red and green lines (at the lower left hand corner and hit the “head “ of the centre-punch firmly with your warrington hammer to form a indent.( black dot )

Step 7 -  Repeat Step 6 at the Upper Left Hand corner at also the Upper right and lower right corners (shown as black dots)

Step 8 -  Set the distance between the two points of your spring dividers to 10mm

Step 9 -  Place one point of the spring dividers into the indent at the upper left corner and scribe an arc (black arc) from the end of the green line to the end of the red line

Step 10 - Repeat Step 9 at the Upper right Hand corner at also the lower right and lower left corners (shown as black arcs)

Steps of Production - Marking out (part 1) cont

Step 11 -  Align the 40mm mark of your rule with the lower left hand edge of your material and scribe line along the end of your rule (blue line)

Step 12 -  Repeat Step 11 at the right hand edge of your material (blue line)

Step 13 -  Scribe a line by joining the two lines you scribed at Steps 11 and 12 (shown as grey line)

Step 14 -  Align the 45mm mark of your rule with the right  hand edge of your material and scribe line along the end of your rule (orange line)

Step 15 -  Repeat Step 14 at the Left Hand end of your material (orange line)

Step 16 -  Locate the tip of your centre-punch on the intersection of the grey and orange lines (at the left hand end) and hit the “head “ of the   centre-punch firmly with your warrington hammer to form a indent.( red dot )

Step 17 -  Repeat Step 16 at the right hand end at the intersection of the grey and orange lines  (shown as red dot)

Step 18 -  Align the 20mm mark of your rule with the lower right hand corner of your material and scribe line along the end of your rule (blue line)

Step 19 -  Repeat Step 18 at the Upper right Hand corner at also the lower left and upper left corners (shown as blue lines)

Steps of Production - Cutting and Drilling (part 2)

This section of producing your cowling involves you trimming the corners of your workpiece, drilling holes and then removing all the sharp edges.

To achieve this progress in your production you will need some additional tools and equipment:

Step 20 -  Using the straight aviation snips (yellow handle) cut along the four arcs you scribed at Steps 9 and 10 (black arcs)

Step 21 -  Holding your metal workpiece firmly with the multi grips proceed to drill six (6) Dia 4 holes using the Drill press and ensuring that you align the 4mm drill correctly with the indents made by the centre punch at Steps 6, 7 and 16 (black dots and red dots)

Step 22 -  Use the Deburring tool to remove the sharp points on the underside of the six holes you drill at Step 21

Step 23 -  Use your hand file to file smooth any rough edges at the four corners made by the aviation snips at Step 20

Step 24 -  Using a clean rag and some cleaning solvent( ask your teacher ) and wipe clean your workpiece of the permanent marker and any oils

Your metal workpiece should now have four smooth rounded corners, six holes drilled and deburred and with no marking pen outline and looks like this image 

Step 25 -  Position your workpiece into the jaws of the Engineers Vice with the marks made at Steps 18 & 19  (blue lines), facing towards yourself, and aligned with the top of the vice jaws and tighten the vice to securely hold your workpiece.

Step 26 -  Place the palm of your hand on your workpiece and then push your palm forward so that the top of your workpiece moves away from yourself until it is flat against the vice. (You may want to gently use your tinsman mallet to achieve a sharp and neat bend) 

Step 27 -  Take your workpiece out of the vice and place the other end into the jaws of the Engineers Vice with the marks made at 

Steps 18 & 19  (blue lines), facing towards yourself, and aligned with the top of the vice jaws and tighten the vice to securely hold your workpiece. 

Step 28 -  Repeat Step 26

Step 29 -  Position your workpiece centrally over the 50mm mandrel and slowly push each end of your workpiece down towards the workbench so that you wrap your workpiece around the mandrel to form a tunnel shape.(You may want to gently use your tinsman mallet to achieve a neat and smooth  round bend for your cowling) 

Step 30 - To provide a protective finish to your cowling read and follow the instructions in the document, look at the section on finishing