These are photo files of some of the strips used for the F Open Large Coaching Knobs. You can make your own scales. Eventually we standardized on an outer diameter of 50 mm for all knobs.
Before the Worlds, we were really tearing our hair out because of the variety of different Riflescopes used and also people were changing Riflescopes right up to the actual event. Some were 5 minutes, others 6, 10 and 15 (or was it 14 ?) . I have seen almost everything. Also the inner hole in the knobs had to be tailored to each scope. And tube diameters changed needing different index devices - thanks especially to March ! . For the next Worlds, most had settled on NF Comps which helped. There really was no other option to making strips which glued on and making a larger inner hole with various spaced bushings. Some larger knobs actually needed an individually made knob. All were carved out from solid Aluminium which is a lot of tedious work. No CNC machines were available.
These strips MUST be exactly the right length to meet well around the circumference. This involves careful file manipulation and some trial and error when printing them.
Another consideration was that ALL should be very similar pattern to help the coach and all quickly readable by a plotter 8 feet away. Black on white was deemed best after a LOT of trials. This was achieved by removing ALL extraneous marking like direction arrows and fine graduations and using thick chunky lettering and lines. Some initially were worried that it would be easy to make reading mistakes having only full and half minute marks. This was not the case. Because of the larger diameter and the fact that settings move in definite increments the reading was unmistakable.
We placed a LOT of emphasis on distinguishing Left from Right and tried many schemes. The pattern finally chosen is not quite as nice to read for Right settings than Left settings but emphasis on R and L was considered far more important. than anything else. Misreading by 1/8 is not usually a disaster but mixing up L and R is a disaster. One misread like that would let down the entire team !
The files are large because they are bitmaps. Better if you want to manipulate the dimensions. Simple 'Paint' which comes with Windows will work on them.
Print off on some high quality photo paper. Laser printers back then were rare and Ink Jet was used and is OK. The strips are cut, a hole punched in the centre of the 0 mark.
Contact Cement was sprayed on the knob held on a pencil and the back of the strips. The paper was applied and trimmed at one end so it matched up leaving a minimum gap at a blank spot near the back of the knob. Finally, after drying, a few applications of Photo Lacquer was sprayed on. I have knobs over 10 years old done like this that are still quite usable.
One point some ignore is where numbers should be placed. It is a world standard in all instruments that numbers are placed at the dividing line between minutes and not be plonked midway. People who are used to reading digital scales seem to be forgetting this. Just because there may be a larger blank space elsewhere does not mean that is ideal for the position of numbers.
I seem to have lost the files for 10 minute strips but attached below is one for the 6 minute NF Benchrest Scope. You can duplicate this and print a sheet containing many strips.
Also attached is a picture of an early experimental Knob using this strip.
I will attempt to write a more detailed article on the development of the large FO Coaching Knob. This will involve searching ancient computer backups.
Peter Smith.