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The Parking Meter: A Coin That Unlocks a Clock
By the 1930s city streets were lined with cars parked all day, and shops lost the customers who could not stop. A parking meter rations the kerb: a coin buys a set time, and a signal shows anyone passing when it has run out.
Carl C. Magee of Oklahoma City, assignor to the Dual Parking Meter Company, filed US 2,118,318, *Coin Controlled Parking Meter*, on 13 May 1935; it was granted 24 May 1938. Inside a lockable head on a post, a coin completes the winding mechanism; turning the handle winds a spring; an escapement-governed train runs it down; a signal shows while the time lasts and vanishes when it has elapsed. The last coin shows in a window, and the coins fall into a sealed container so the collections can be checked. Oklahoma City installed Magee's meters in July 1935.
This rung designs the gear train and the spring for a one-hour meter and builds a coin-interlocked timer from a wind-up motor.
中級者
About 5 hours
手順
1
1
Gear ratio and spring energy
Gear ratio and spring energy
Jupyter ノートブックを読み込み中…
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2
One parking, as the patent describes it
One parking, as the patent describes it
Blocklyワークスペース
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3
What keeps the time
What keeps the time
The meter's clockwork is governed by an escapement. The embedded blueprint shows how an escapement releases a gear train one tooth at a time.
4
4
Build a coin-interlocked timer
Build a coin-interlocked timer
Take a wind-up motor mechanism and fit a pointer to its slowest output shaft; mark the run-down time of a full wind on a card dial behind it.
Make the winding key the interlock, as Magee's coin was. 3D-print a crank that drives the winding shaft through a sliding coupling: two halves with a slot between them exactly as wide as the coin. Without a coin the outer half turns freely; drop a coin into the slot and it locks the halves together, so the crank winds the spring. Put a ramp below so that when the crank has turned half a revolution the coin falls out of the slot into a box.
Try it without a coin: the crank spins, nothing winds. With a coin: one wind, the pointer runs down across its dial. Time a full run and compare with the card.
このステップの材料:
ぜんまい仕掛けのモーター機構1 個
銅貨3 個
合板1 個
小ねじ6 個
堅木のダボ1 個必要な工具:
FDM 3D プリンター
PETGフィラメント
コードレスドリル
ドリルビットセット
デジタルノギス 6インチ
ストップウォッチ5
5
A meter that takes the coin but gives no time
A meter that takes the coin but gives no time
Coin-operated timer faults.
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6
History and honest limits
History and honest limits
**Carl C. Magee** of Oklahoma City filed **US 2,118,318** on 13 May 1935, assigned to the Dual Parking Meter Company; granted 24 May 1938. Oklahoma City installed 150 of his meters along 14 blocks downtown in July 1935, charging five cents an hour; within a few years they spread to cities across the United States and abroad.
**Honest limits.** The notebook's beat rate, train losses and spring figures are illustrative, not Magee's. The printed interlock accepts anything the size of the coin — real meters gauge a coin's diameter, thickness and sometimes its metal.
材料
5- ぜんまい仕掛けのモーター機構10%コミッション1 個プレースホルダー
- 3 個プレースホルダー
- 1 個プレースホルダー
- 6 個プレースホルダー
- 1 個プレースホルダー
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