Digital compass / dividers?

[CPDDET]

Anyone using this tool to make measurements on ships plans?

[Ed Ku20]

Dave, I have dividers, but they are not digital.  I have not found the need to use them very often.  I have an Incra 6" precision ruler that I use all the time.

[Peanut6]

I use the dividers from my antique Kern Swiss drafting set and compasses from my manual drafting days.  I have numerous scales I use for measuring and rely heavily on my digital calipers.  I also have an antique L.B. Starrett Co. set of mechanical calipers but I keep them in the box.  I would like to get may hands on a good set of proportional dividers though.  The cost of quality new proportional dividers is beyond my budget but I've seen antiques on ebay that are considerably less expensive.  I would rather have those anyway.   

[Bob Cleek]

On 5/11/2022 at 8:39 AM, Peanut6 said:

I would like to get my hands on a good set of proportional dividers though.  The cost of quality new proportional dividers is beyond my budget but I've seen antiques on ebay that are considerably less expensive.  I would rather have those anyway. 

There's a set of finestkind Keuffel and Esser Paragon Universal (decimally scaled) proportional dividers on eBay right now for a "buy it now" price of 76.00 including shipping, which is about what a "user" pair usually go for. I've not seen them for much less than that and I watch eBay fairly closely because I collect old manual drafting instruments. Keuffel Esser K&E #440 Divider 10" with instructions READ | eBay

 

These are 10" long with rack and pinion Vernier adjustment, scaled in decimal equivalents so any scale can be accurately set without guesswork. You can get smaller rack and pinion adjustable proportional dividers for less, but they are not decimally scaled with Vernier adjustment and the distance they can pick up is limited by their reduced size. Look for the top end manufacturers. As a manual draftsman, you know who they are. The junk is not worth bothering with. 

 

Treat yourself! You'll be glad you did. I can't imagine building models without one, but everybody's mileage varies, I suppose. ''

 

 

(This is not a picture of the ones offered on eBay now, but is identical. See photos of set for sale on the eBay link.)

 

Edited May 15, 2022 by Bob Cleek

[Peanut6]

Bob, sounds like you grabbed the Brass Ring with your set, good for you.  eBay will be the route I take to acquire my set but I need to wait until the shipyard coffer is suitably filled.  From some of the deals I've seen for this type of equipment, I've come to believe most of the sellers fall into any one or combination of the following:  don't know what it is, don't know how to use or have a use for it, don't know the quality of the item compared to what is available new.      

[bridgman]

Does anyone have a source for instructions for the proper use of proportional dividers? Google search returns

use for  art work proportions and not much else. Have pair of old Weems navigation dividers from Air Force

navigation brother identical to those shown in Bob Cleek's photo. Has markins use on maps different scales 

and straight proportions. No instructions otherwise.

Thanks,

Bridgman Bob

 

 

[mtaylor]

Bob,

I Googled "Weems navigation dividers instructions " and got a pile of hits for "how to use them".... https://www.google.com/search?q=Weems+navigation+dividers+instructions&rlz=1C1ZCEB_enUS832US832&ei=JGKBYrvSEKTPkPIPhqSNkAY&ved=0ahUKEwi79Jfeq-L3AhWkJ0QIHQZSA2IQ4dUDCA4&uact=5&oq=Weems+navigation+dividers+instructions&gs_lcp=Cgdnd3Mtd2l6EAMyBQghEKABOgcIABBHELADOgUIIRCrAkoECEEYAEoECEYYAFCeRFj6b2Dtc2gBcAF4AIABiwGIAeoLkgEEMC4xM5gBAKABAcgBCMABAQ&sclient=gws-wiz

 

I'm not sure which ones are for your set.

[Bob Cleek]

7 hours ago, bridgman said:

Does anyone have a source for instructions for the proper use of proportional dividers? Google search returns

use for  art work proportions and not much else. Have pair of old Weems navigation dividers from Air Force

navigation brother identical to those shown in Bob Cleek's photo. Has markins use on maps different scales 

and straight proportions. No instructions otherwise.

Thanks,

Bridgman Bob

Here you go. These are the instructions for the preferred 'universal " decimally scaled Keuffel and Esser 10" proportional dividers. (Also sold by other firms such as Bowen, Post, and Dietzgen.) These dividers are scaled from 10 to 110. By setting the axis at the point on the scale corresponding to the three-place decimal equivalent of the proportion one wishes the dividers to yield the relative proportional distances will be found at the points. They are set by turning the knob which operates a rack and pinion adjustment mechanism which has a Vernier scale for the third digit of the three place scale settings. If you don't have a decimally scaled "universal" set of proportional dividers, you won't be able to set any fraction you want on your dividers using the scale etched on the instrument. The smaller proportional dividers have different scaling, usually showing "lines," and "circles" scales by proportion, such as 1:2, 1:3, 1:4, and so on. For anything else, you have to set them by guess and by golly, manually, by adjusting the axis to yield a measured distance at the points by trial and error using a scale. Less expensive proportional dividers will not have rack and pinion adjustment. They will just have a slip adjustment, which is very difficult to adjust for fine settings. Don't buy cheap brass Asian "decorator" knock-offs. They are next to useless. Measuring instruments are definitely a "you get what you pay for" kind of thing.

 

This instruction sheet is all I have handy on my hard drive at the moment. (It can be enlarged to be readable by holding down your control button and turning the wheel on your mouse.) The newer K&E Paragon models come in a case which has a metal plate on the bottom with the table of settings on it. The older models have a folding card with the same information which fits inside the case. In the last years of production, the "Mark 1" line replaced the former top of the line "Paragon" models and they cut corners on the cases and just provided the below printed instruction sheet. The table of settings give you the decimal equivalents for various ratios, as well as the formula for converting any fraction to its decimal equivalent. It also give the settings for miscellaneous ratios such as the diameter of a circle to the side of a square of equal area, the volume of a sphere to the volume of a circumscribed cube, and for navigation and cartographic work, the setting for feet to meters, yards to meters, and miles to kilometers. There are also settings for dividing a line into a set number of equal parts, and dividing the circumference of a circle into a given number of parts which may be useful in modeling capstans and ships' wheels, I suppose.

 

The Weems and Plath navigational proportional dividers are scaled for use in navigation for performing speed, time, and distance calculations on navigational charts. There are lots of these on the used market and are still produced by Weems and Plath. (There was a huge "dump" of Russian-made military surplus navigational proportional dividers onto the internet market following the fall of the Soviet Union.) These dividers operate exactly the same as all other proportional dividers mechanically, but are scaled with settings specific to navigation. They aren't as useful for model scaling purposes are "universal" or general purpose "lines and circles" proportional dividers which are scaled to to a myriad of functions such as converting scale measurements, determining the area of a circle, dividing distances, and on and on depending upon the settings chosen.

 

Most navigational proportional dividers will also have a scale on one leg, usually numbered from one to ten, which can be used for setting for conversions of measured distances. As the navigationally scaled dividers function the same as all proportional dividers, they can always be manually set for any spatial conversion by moving the axis until the desired ration of distances between points is achieved. For example, to double the size of a line measured, or reduce it by half, set the axis to where the points on one end are one inch apart and the points on the other side are one half an inch apart.

Edited May 16, 2022 by Bob Cleek

[bridgman]

Thank you Mark and Bob for your replies. I had these dividers for many years, but never able to sort out 

their full capabilities other than simple proportions. Even found instructions for the same model to 

perform speed time navigational calculations though I'm long beyond needing that function. Bob, if convenient,

could you forward a clearer copy of those instructions as the table on the bottom half is difficult to make out.

Thanks again

Bob

[Bob Cleek]

3 hours ago, bridgman said:

Bob, if convenient,

could you forward a clearer copy of those instructions as the table on the bottom half is difficult to make out.

Unfortunately, the photo I posted is all I have. If you enlarge the photo on your screen by holding down the "control" key and turning the wheel on your mouse, the picture can be enlarged sufficiently to read the fine print of the decimal equivalents. (You may have to open the picture separately on your screen to enlarge it sufficiently.)

Edited May 16, 2022 by Bob Cleek