Creation

In 1943, Richard T James, a naval mechanical engineer, observed a spring "stepping" downward after being knocked off a shelf, then coming to rest in a vertical position.^[4][5] James's wife Betty later recalled, "He came home and said, 'I think if I got the right property of steel and the right tension, I could make it walk.'"^[6] James experimented with different types of steel wire over the next year, and finally found a spring that would "walk". Betty was skeptical, but changed her mind when the toy was fine-tuned and neighborhood children expressed an excited interest in it.^[5]

Richard and Betty formed James Industries and began manufacturing slinkys in Clifton Heights, Pennsylvania, selling them for $1 each.^[5] They were 2+1⁄2 inches (64 mm) tall, and included 98 coils of high-grade blue-black Swedish steel.^[7] They initially had difficulty selling Slinky to toy stores, but in November 1945, were granted permission to set up an inclined plane in the toy section of Gimbels Department Store in Philadelphia to demonstrate it. It was an instant hit; the first 400 units were sold in 90 minutes.^[5][7] In 1946, Slinky was introduced at the American Toy Fair.

Subsequent developments

In 1960, after his wife filed for divorce, Richard James left the company and he became an evangelical missionary in Bolivia with Wycliffe Bible Translators.^[8] Betty James moved the company to Hollidaysburg, Pennsylvania in 1964 and the company grew under her direction.^[5] She attributed the toy's success to its "simplicity".^[9] The company was sold to Poof Products, Inc. in 1998.^[5][10] Slinky continued production in Hollidaysburg.^[5]

Betty James died of congestive heart failure in November 2008, at age 90, after serving as James Industries' president from 1960 to 1998.^[10]

In July 2012, Poof-Slinky, Inc. was acquired by the private equity firm Propel Equity Partners.^[11] In 2014, Propel Equity Partners consolidated Poof-Slinky® and several other toy brands into Alex Brands™.^[12]

In July 2020, the Slinky brand was sold to Just Play.^[13]

Period of oscillation

The oscillation of a vertically suspended Slinky has the periodic duration^[14]

${\displaystyle T={\sqrt {\frac {32L}{g}}}\,,}$

where ${\textstyle L}$ is the length of the Slinky in the gravitational field of the Earth and ${\textstyle g}$ the acceleration due to gravity ${\textstyle g=9.81\,\mathrm {m/s} ^{2}}$. Please note, that the expression for ${\textstyle T}$ is independent of the spring constant ${\textstyle k}$ and the mass ${\textstyle m}$ of the Slinky. For a spring pendulum one would expect such a dependence. This is because the dependence on ${\textstyle k}$ and ${\textstyle m}$ is hidden in the length ${\textstyle L(k,m)}$:

${\displaystyle L(k,m)={\frac {mg}{2k}}={\frac {W}{2k}}\,,}$

this allows one to write:

${\displaystyle T=4{\sqrt {\frac {m}{k}}}\,.}$

This expressions differs from the ordinary spring pendulum

${\displaystyle T_{\mbox{spring pendulum}}=2\pi {\sqrt {\frac {m}{k}}}\,,}$

because for the spring pendulum one assumes a massless spring with a mass ${\textstyle m}$ attached at the bottom.

Equilibrium

In the state of equilibrium of a Slinky, all net force is cancelled throughout the entire Slinky. This results in a stationary Slinky with zero velocity. As the positions of each part of the Slinky is governed by the Slinky's mass, the force of gravity and the spring constant, various other properties of the Slinky may be induced. The length of an idealized Slinky extended under its own weight, assuming the fully compressed length is negligible, is

${\displaystyle L={\frac {W}{2k}},}$

where L is the length of the Slinky, W is the weight of the Slinky, and k is the spring constant of the Slinky.

Due to the effect of gravity, the Slinky appears bunched up towards the bottom end, as governed by the equation

${\displaystyle p(n)=L(n-1)^{2}.}$

Where n is a dimensionless variable, 0 ≤ n ≤ 1, with n = 0 corresponding to the top of the Slinky and n = 1 being the bottom. Each intermediate value of n corresponds to the proportion of the Slinky's mass above that point n, and p(n) gives the position that n is above the bottom of the Slinky.

This quadratic equation means that rather than the center of mass being at the middle of the Slinky, it lies one quarter of the length above the bottom end,

${\displaystyle p\left({\frac {1}{2}}\right)=L\left({\frac {1}{2}}-1\right)^{2}={\frac {L}{4}}.}$

Phenomena

Jingle

The jingle for the Slinky television commercial was created in Columbia, South Carolina in 1962 with Johnny McCullough and Homer Fesperman writing the music and Charles Weagly penning the lyrics. It became the longest-running jingle in advertising history.^[5]

The jingle has itself been parodied and referenced in popular culture. It is seen in the "Log" commercial on The Ren & Stimpy Show and sung by actor Jim Carrey in Ace Ventura: When Nature Calls. It is also referenced in the movie Lords of Dogtown, where it is sung in full by Emile Hirsch, and is sung by Eddie Murphy as part of the final routine in the stand-up comedy film Eddie Murphy Raw. It was also parodied in an ad for the Isuzu Amigo used as a promo for the vehicle's return in late March 1998, nearly two months before the ad was pulled due to criticism from the company that made the Slinky.^[19]

Slinky Dog

Early in the history of James Industries, Helen Herrick Malsed of Washington state sent the company a letter and drawings for developing Slinky pull-toys. The company liked her ideas, and Slinky Dog and Slinky Train were added to the company's product line. Slinky Dog, a small plastic dog whose front and rear ends were joined by a metal Slinky, debuted in 1952. Malsed received royalties of $60,000 to $70,000 annually for 17 years on her patent for the Slinky pull-toy idea, but never visited the plant.^[20]

In 1995, the Slinky Dog (voiced by Jim Varney and Blake Clark) was redesigned for all of Pixar's Toy Story movies. James Industries had discontinued their Slinky Dog a few years previously. Betty James approved of the new Slinky Dog, telling the press, "The earlier Slinky Dog wasn't nearly as cute as this one."^[21]

Plastic Slinky

Rainbow colored plastic Slinky toy

Plastic Slinkys are also available. They can be made in different colors. Many of them are made with the colors of the rainbow in rainbow order. They were marketed in the 1970s as a safer alternative to metal Slinkys as they did not present a hazard when inserted into electrical sockets. The plastic spring toy, known as the Plastic Slinky was invented by Donald James Reum Sr. of Master Mark Plastics in Albany, Minnesota. Reum came up with the idea as he was playing with different techniques to produce a spiral hose for watering plants. However, as it came off the assembly line, according to his children, it looked more like a "Slinky." He worked at it until it came out perfectly and then went to Betty James with his prototype. Reum manufactured the Plastic Slinky for Betty James for several years. Eventually Betty James decided to manufacture the product exclusively through James manufacturing, effectively ending the production of the toy by the small Minnesota company. Reum's patent number, 4120929 was filed on December 28, 1976, and issued by the US Patent Office on October 17, 1978.^[22]