add check for choosing drill bit

[challenge-bot] / curriculum / challenge-bot.scm

diff --git a/curriculum/challenge-bot.scm b/curriculum/challenge-bot.scm
index cfba91061c5eba5b384142c5e48173480116e204..72de0cff48333284c86fa70aa1880daedf92f4c5 100644 (file)
--- a/curriculum/challenge-bot.scm
+++ b/curriculum/challenge-bot.scm
@@ -5,8 +5,10 @@
  :title [challenge-bot]
  (chapter
   :title [mechanical]
+  (p [let's build your robot!])
   (section
    :title [arduino to deck]
+   (p [let's attach the arduino to the deck.])
    (subsection
     :title [required materials]
     (p [you will need the things in this picture.
@@ -20,27 +22,41 @@
               (item [alan wrench])
               (item [wood block])
               (item [arduino])
-              (item [#6-32x3/8\", four of them]))]))
+              (item [#6-32x3/8\", four of them])
+              (item [robot deck, the white thing with a grid of holes1]))]))
    (subsection
     :title [first hole]
     (subsubsection
      :title [choosing drill bit]
-     (p [choosing the right drill bit depends on what job you are doing.
-                  right now, we are making holes for screws to hold the
-                  arduino to the deck.
-                  this means the hole needs to be big enough for the
-                  screw body to fit through.
-                  we want the screw to stay put once it's in place.
-                  we also want the drill bit to be smaller than the
-                  diameter of the thread.
-                  the screw was chosen so that the hole on the arduino
-                  was bigger than the body and smaller than the thread.
-                  we will choose the biggest drill bit that fits through
-                  the hole on the arduino.])
+     (p [the arduino comes with holes in it already, so we will make
+             some choices around those holes.
+             choosing the right drill bit depends on what job you are
+             doing.
+             right now, we are making holes for screws to hold the
+             arduino to the deck.
+             there are two constraints between the hole and screw.
+             each hole needs to be big enough for the screw body to fit
+             through it.
+             the holes also need to be smaller than the screw's thread.
+             since there are holes on the arduino already, the screw was
+             chosen to match it.
+             the screw was chosen so that the hole on the arduino was
+             bigger than the screw body and smaller than its thread.
+             we will choose the biggest drill bit that fits through the
+             hole on the arduino, then use that to drill holes in the
+             deck.])
      (p [here's a cross section of a screw in the deck]
         (figure :legend "screw cross section"
                 (image :file
-                       "arduino-to-deck/screw-cross-section.png"))))
+                       "arduino-to-deck/screw-cross-section.png")))
+     (p [check
+         ,(itemize
+           (item
+            [what would happen if the drill bit were larger than the
+                  screw thread?])
+           (item
+            [what would happen if the drill bit were smaller than the
+                  screw body?]))]))
     (subsubsection
      :title [inserting drill bit]
      (p (figure :legend "arduino to deck / insert bit"