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20,000 Volts: 1942

20,000 Volts: 1942

July 1942. Melrose Park, Illinois. "Production of aircraft engines. Buick plant. Foreman F.I. Bowman shows Marietta Morgan how to operate this bomb-test machine used to test reconditioned spark plugs. A young Negro girl, Marietta had been a clerk in a meat market. Her lack of industrial experience, however, has been no handicap for her present war job in a large Midwest airplane plant. She's rapidly becoming a skilled and efficient machine operator." Medium format safety negative by Ann Rosener for the Office of War Information. View full size.


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Under pressure

Machines like this exist because a spark plug can fire just fine in free air, but fail to fire in compressed air. You can also check for air leakage around the body of the spark plug. This machine would have probably used air pressures around 6 to 8 times atmospheric, or about 90 to 120 psig.

Spark plugs can still be tested in machines like this, although the plugs are cheap enough now that they usually just get replaced. I wonder why an aircraft engine factory was using used plugs, though? Maybe the engines were built with a set of plugs, broken in, and then got a new set. During break-in, the piston rings wouldn't seal as well, so the plugs would tend to get fouled with oil - cleaning and testing them would let them be used to break in another engine.

"Bomb" here means "container that can hold pressure", a somewhat obscure usage of the word. Sometimes older people will refer to an aerosol can as a "spray bomb".

Very cool!

I love the sciency/industry pictures here, and this one's a peach. Thanks.

Re: So easy a Negro girl can do it!

Regarding the comment on the description being insulting to the black girl pictured, I actually didn't gather this at all. Save for use of the then-contemporary term "negro," I didn't feel the description was disparaging the young lady with regard to her race at all.

The description reads, "her lack of industrial experience has been no handicap for her present war job in a large Midwest airplane plant."

Remember, her prior job was as a meat market clerk, so one would naturally wonder if the transition was an easy one.

["Negro" is "disparaging"? - Dave]

The plant is still there

But it's no longer owned by Buick; it now makes truck engines for International Harvester. I live about a half mile away and my home along with many others in my subdivision were built for wartime workers at this facility.

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20,000 Volts

The machine is called a "Hi-Pot" for high potential. Its purpose is to expose a component under test with a very high voltage and very low current to determine at what level the tested component will break down and begin to conduct electricity.

At that time, they used a step-up transformer to achieve high voltage, and a mercury vapor rectifier tube to convert it to DC.

These are still in common use today, with solid state rectification.

Never, ever

... would I allow bomb testing at my home.

Thank you for posting this

Like the Anon Tipster of the "Birth of Opportunity" post, my great-aunt and great uncles also found opportunity during WWII. Both of my grandfathers served in segregated units during WWII (my maternal grandfather served in New Guinea). Opportunities in shipyards and migration away from the South led to college and graduate school educations, and the achievement of personal goals. I learned much from these older family members while growing up (I'm an African-American woman who was born in 1968). They were hard-working, patriotic people who believed deeply in education, civic engagement, and solid family values. The young lady in the photo and the people in the screen grab from the Library of Congress would have been their contemporaries. So often I log in to Shorpy and see images of people who feel familiar to me. They aren't always Black, but they tend to be the rural folk & working class strivers I knew and loved. Thank you, Dave.

"Young Negro Girl"

It's typical of the era that they chose a girl with a very White appearance.

[That might be a mistaken assumption. - Dave]

Bomb tester?

Yeah, ummmmm, do you have any other jobs available?

So easy a Negro girl can do it!

Amazing how we used to talk and think we were making perfect sense.

I think the guy ...

Is one of the Pep Boys. Which one, I'm not sure.

Little known side-effect

20,000V does create an electric field that prompts excessive axillary discharge, referred to in common parlance as "pit stains".

The Birth of Opportunity

World War II was a crisis that also generated unprecedented opportunities across America. For individuals like Ms. Morgan, it was more than access to jobs. It was a means for accumulating the base of wealth needed for household formation. My grandparents bought their first home in Sewickley, Pennsylvania, in 1941, a purchase made possible by Grandpa's job with Standard Steel Spring Company, where he made armor plate, and Grandma's job with the American Bridge company, where she welded the hulls of LST ships. Prior to the war, their opportunities were limited to domestic work which paid them only enough to live on the premises of their employer. By the end of the war, they had furnished a home in which they would raise their daughters, send them to college, and ... well, you get the idea.

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