MJAX1

This routine will calculate detailed information about jack rafters on the main common-pitched side of a hip roof, given:

- Rafter On-Center layouts (12”, 16”, 19.2”, 24” are typical but any number can be entered)- Main Pitch- End Pitch- Span

Items calculated by this routine are:- Each Jack Rafter length, in FIS, starting from the longest to the shortest.- The difference Increment length, in FIS, from one Jack length to the next Jack length.- The Bevel of the compound cut at the top of the Jack rafter.

**NOTE: This routine assumes a ridge thickness of 1 1/2” There is another jack rafter routine specifically designed for more complex situations.

As with all of these routines, the user is “prompted” to enter the required numbers so that the calculation can be performed.

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Here is what the actual routine looks like when keyed into the calculator.

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The keystrokes to enter/store, in an HP scientific calculator, in RPN mode are below:

<< “CENTERS IN INCH” “” INPUT OBJ ‘C’ STO “MAIN PITCH” “” INPUT OBJ ‘H’ STO H 12 / ‘M’ STO“END PITCH” “” INPUT OBJ ‘G’ STO G 12 / ‘E’ STO“SPAN IN FIS” “” INPUT OBJ INSH 1.5 - 2 / ‘R’ STO

90 H G / ATAN - ‘B’ STO R M * E / ‘L’ STO R L / ATAN ‘V’ STO1.5 .75 V SIN / - V TAN * ‘F’ STOR M ATAN COS INV * ‘A’ STOA F SQ F M * SQ + √ + ‘D’ STOC L A / / ‘N’ STO

DO D FEET D N - ‘D’ STOUNTIL D 0 ≤END

N FEET ‘INC’ TAG{ A L N R M E C V D F } PURGEDEPTH ROLL DROP B NUM‘BEVELS’ TAG DEPTH 1 + ‘P’ STO2 ‘Q’ STODO Q ROLL Q 1 + ‘Q’ STOUNTIL Q P = =END{ H G B P Q } PURGE >>

**NOTE: Some of these equations use PURGE and others use CLEER. It’s a user preference option. Originally, I had used the PURGE option only until I realized that a CLEER subroutine would make for more efficient coding.

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WALLMAXX, INC COPYRIGHT © 2012 ALL RIGHTS RESERVED