Wednesday, January 26, 2011

ROLLING OFFSETS



WHAT IS A ROLLING OFFSET?
Rolling offsets refer to the directional changes (both vertically and horizontally) that a pipe can make in a piping system.


HOW TO CALCULATE THE TRAVEL PIECE FOR ROLLING OFFSETS
1.      Determine the RISE of the pipes in question. The rise refers to how high vertically the piping system goes. To figure out the rise, take a look at the side view drawing.
a.       The height of the higher pipe from the finished floor to the center of the pipe is 47½ inches.
b.      The height of the lower pipe from the finished floor to the center of the pipe is 16⅞ inches
c.       Subtract the lower number from the higher number to get your RISE.
                 i.      47½ - 16⅞ = 30 ⅝ inches
2.      Next is to determine the ROLL. The roll refers to the horizontal distance between one end point and continuing until you reach the other end point. Let us now examine the plan (above) view drawing.
a.      The pipe farther away from the wall measures 50 inches.
b.      The pipe closer to the wall measures 32 ⅜ inches
c.       Subtract the lower number from the higher number to get your ROLL.
                 i.      50 - 32 ⅜ = 17  ⅝
             3.      Now to calculate for your travel piece, there are two methods:
a.      Square Root Method  - √(ROLL2 + RISE2)
                 i.  Insert your ROLL and RISE into the equation above and calculate using a calculator. This number is called your ADVANCE
1.      35.334561692485 ≈ 35 inches
                ii.      Now multiply your ADVANCE by the constant for 45 degree offsets (1.414)[i]
1.      35 ⅜× 1.414 = 50.02025 inches ≈ 50 inches
2.      Take off for 2 45s and now you have your travel piece. (Vic-45s take of 3 inches.)
a.      50 – 6 = 46 inches
b.      Steel Square Method
                 i.      Layout your ROLL and RISE on a square on the ground
                ii.      Diagonally measure between them
1.      35 ⅜ inches should be your answer
               iii.      Now multiply your ADVANCE by the constant for 45 degree offsets (1.414)
1.      35 × 1.414 = 50.02025 inches ≈ 50 inches
2.      Take off for 2 45s and now you have your travel piece. (Vic-45s take of 3 inches.)
a.      50 – 6 = 46 inches


*Practice Problems with answer sheets will Follow*

[i] If this was a rolling offset with 90s, the constant would be 1.

1 comment:

  1. sorry brother fitter but you ganna half to fire the torch back up and cut 2in off that travel pice 50-6=44 not 46!!! the rest of your math was dead on thoe

    ReplyDelete