APL (35)

{∇⍵+⌈⎕DL.05⊣⎕←'|'↑⍨-21+⌈20×1○⍵×.1}1

Explanation:

• {...}1: call the function with 1 at the beginning
• 1○⍵×.1: close enough for government work to sin(⍵×π÷30). (1○ is sin).
• -21+⌈20: normalize to the range 1..40 and negate
• '|'↑⍨: take the last N characters from the string '|' (which results in a string of spaces with a | at the end
• ⎕←: display
• ⌈⎕DL.05: wait 50 ms and return 1. (⎕DL returns the amount of time it actually waited, which is going to be close to 0.05, rounding that value up gives 1).
• ∇⍵+: add that number (1) to ⍵ and run the function again.

APL (35)

(Yes, it does fit in 35 bytes, here's a 1-byte APL encoding)

{∇⍵+⌈⎕DL.05⊣⎕←'|'↑⍨-21+⌈20×1○⍵×.1}1

Explanation:

• {...}1: call the function with 1 at the beginning
• 1○⍵×.1: close enough for government work to sin(⍵×π÷30). (1○ is sin).
• -21+⌈20: normalize to the range 1..40 and negate
• '|'↑⍨: take the last N characters from the string '|' (which results in a string of spaces with a | at the end
• ⎕←: display
• ⌈⎕DL.05: wait 50 ms and return 1. (⎕DL returns the amount of time it actually waited, which is going to be close to 0.05, rounding that value up gives 1).
• ∇⍵+: add that number (1) to ⍵ and run the function again.