Identifying The Location Of A Helmet Crack

Big Red here with a question from "Max Rockatansky"...

So, TAKE FIVE!

Max asks,

“Big Red, I noticed numbers with degree marks next to cracks on some of the helmet picks in your previous blog. Was this how the Army located helmet cracks?”

Superb observation Max!

When the Engineers at Watertown Arsenal were tasked to resolve the production breakage and post production service cracking issues of the M-1 helmet, Abe Hurlich and his team began their investigations in earnest. Their goal was to gather data and interpret their findings in a way that would assist both the helmet fabricators as well as the helmet steel producers in improving the quality of steel and fabrication methods. In order to understand the data gathered they developed measurement systems to record findings and make the results relevant to the helmet process. One of these measurement tools was a simple diagram drawn on a piece of plywood.

The first step in determining the reasons behind service cracking was to document the locations of the cracks. The outline of a helmet was traced out on a piece of plywood and looking top down the center of the visor was assigned as zero degrees. Rotating clockwise around the helmet every five-degree step was then marked off back to zero. A helmet was then placed on top of the diagram allowing every crack to be mapped within the 5-degree steps.

Finished helmets had their rims removed in order to identify the potential of hidden cracks that might grow over time. As the observations of various cracked helmets were recorded it was noted that many of these helmets had irregular trimmed edges with small notches “assumed” to be the result of chipped trimming dies.

The location of these notches were determined to be confined, almost exclusively, to the helmets visor area as well as the tendency for cracking to originate at the location of a notch.

As data was gathered from various helmet lots with cracks in the same location from the same fabricator, the lot and lift numbers, recorded from the inside visor of the helmets, were used to determine the flow of the helmets through the fabricators plant which led to trimming dies with a nick in a location that corresponded to notches left on the rim of the cracked helmets that had been trimmed by the offending die.

These findings led to improvements in die maintenance as well as the development of an edge annealing process used to relax the stress found in the visor area which ultimately reduced the frequency of cracks forming in this area to a level Ordnance deemed acceptable.

Big Red Says!

FIVE'S OVER  -  MOVE OUT!