From: "Jerry G" To: "Jerry Glickstein" Subject: Fw: Rigging Cord Measurer Plus First Draft! Date: Thursday, August 03, 2006 10:04 AM RIGGING CORD MEASURER PLUS So, I have supplied you, (the reader ) with a Bill Of Materials, and working drawings, ( in case anyone would like to make one of their own). And now it is time to give you (the reader) a little history on why I developed and built this unit. In trying to determine the exact sizes of rigging cord, I found that there was a great variance in the actual diameters of the line/cord supplied by manufacturers and kit sellers..... It seemed to me that there was no standard. One of the more popular methods of determining the size is by wrapping the line/cord around a dowel that has been premarked in linear dimensions, such as 1/4" intervals or 1". After wrapping the line/cord around the dowel carefully so as not to distort it, or stretch it, one then counts the number of turns and then divides the length by the number of turns to arrive at the diameter. For example; A line/cord is wrapped for a length of 1/4" and has ten turns. so, 1/4" = .250". .250" divided by 10 = .025". To me, that was not a real solution due to the possibility of inaccurate length measurements, varying tension when wrapping, etc. And that led to the design , development and fabrication of "The Rigging Cord Measurer" There are a couple of places where I tried to nullify the action of the anvil (spindle travel )of the Drop Dial Indicator to "crush" the line/cord when measuring it. First, I removed the internal extension spring that was used to cause the spindle shaft to return to the rest position. Secondly, I made a new larger platen/anvil point to distribute the weight of the spindle shaft when it is used to measure the line/cord. That is self defeating, to a point (pun intended :) because the larger platen adds a small amount of weight. To really measure a line/cord accurately requires either an optical comparator that projects a magnified image of the cord upon a screen where you can compare it to a known standard or scale, or a Toolmaker's microscope where you can measure the cord with the optics, a known standard or scale, without any physical contact. However, I think that is beyond the scope ( pun intended again :) of the normal hobbyist/ship modeler. The only thing left is to calibrate the "Rigging Cord Measurer" by comparative measurement against "known" diameters as supplied by manufacturers and kit sellers..... Much like "zeroing in" a rifle with adjustable sights..... There was an unexpected bonus with this tool. Since it can measure any height from .000" to 1.000" by .001"'s ( one thousandth of an inch), it can be used in lieu of a micrometer with out the possible errors introduced by the operators "feel", which is a prime requisite of using/reading a micrometer. Now, before I describe how I built it, I would like to say that the heart of the unit is the base block which is a commercial item used for set ups on the "Moore Jig Boring" machines. It is 1.0000" by 2.0000" by 3.0000" that is held to size and flatness and parallelism within .0002" ( two ten thousandths of an inch). Equally in importance is the Drop Dial Indicator, which is mounted with the angle brackets to "read" the base block. It has a one inch stroke with a dial that reads in .001"'s (one thousandth of an inch) per division. The baseplate is drilled, using the coordinates found on the drawing. Two of the holes are for the 6- 32 Flat head screws that hold the gusset to the baseplate. Four of the holes are for the 1/4"-20 Button Head Screws that hold the base block to the baseplate. Next, the upright is drilled. It has a total of twelve holes. Six are for the 6-32 Flat Head Screws that secure the gussets. Two are for the 1/4"-20 Button Head Screws that hold the spacer block in place. Four are for the 10-32 Button Head Screws that hold the brackets to the upright. Then, the gussets are drilled and tapped for the 6-32 Flat Head Screws. There are four holes in each gusset. Now come the aluminum brackets. Drill two holes (each )for the # 10 Button Head Screws that hold the brackets to the upright. Drill one hole ( each ) for the Indicator Mounting Screw. The rest is assembly. Now, since I discovered the "bonus" (height measurements) , I am changing the name of the unit to; "Rigging Cord Measurer Plus" !