Go Inside the Design of a Backyard Workhorse


[ MOTOR WHIRRING ] Narrator: THE LAWNMOWER. HOW DOES THIS BACKYARD WORKHORSE CUT THROUGH THE THICKEST GRASS
ON ALL TERRAINS WITHOUT JAMMING? MORE THAN 350 COMPONENTS WORK TOGETHER. THE ENGINE TURNS THE BLADES
50 TIMES A SECOND TO PULVERIZE THE GRASS. IF IT SLOWS DOWN,
THE GRASS WON’T CUT CLEANLY, AND THE MOWER WILL CLOG UP. SO THERE’S A HIDDEN MECHANISM TO KEEP THE BLADE SPINNING
AT EXACTLY THE RIGHT SPEED. IT’S CALLED THE GOVERNOR, AND IT’S THE LAWNMOWER’S
CRUISE CONTROL. IT USES FLYWEIGHTS TO DETECT THE SPEED
OF THE BLADE. IF THE CRANKSHAFT SLOWS DOWN, THE FLYWEIGHTS DECELERATE, FALL INWARDS,
AND TRIGGER A LEVER… …TO OPEN THE THROTTLE
AND PUMP IN MORE FUEL. THIS BOOSTS THE ENGINE’S POWER AND SPINS THE BLADE BACK UP
TO THE PERFECT CUTTING SPEED OF 3,000 TIMES A MINUTE. NOW, IF A BLADE HITS A ROCK
AT OVER 200 MILES PER HOUR, IT CAN CARRY ON CUTTING
WITH HARDLY A SCRATCH. WITH SO MUCH METAL
CRAMMED UNDER ITS SKIN, YOU’D EXPECT THIS MACHINE
TO FEEL HEAVY. SO HOW DO MOWERS
MAKE PUSHING UPHILL EASY? THE SECRET
IS SELF-POWERED WHEELS. ONE ENGINE DRIVES BOTH THE BLADE
AND THE WHEELS. AS THE BLADE SPINS
AT 3,000 TIMES A MINUTE, A BELT CARRIES
THIS BREAKNECK SPEED TO THE GEARBOX, WHICH STEPS DOWN THE SPEED
SEVEN TIMES. A CABLE CONNECTED TO A LEVER
ON THE HANDLEBAR ALLOWS THE DRIVER
TO FINE-TUNE THE SPEED BY ADJUSTING THE BELT’S TENSION. THESE INNOVATIONS MAKE SURE
THIS FOUR-WHEEL DRIVE ALWAYS MOVES
AT THE PERFECT PACE.

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Reader Comments

  1. TheOtherBill

    I'm confused. Governors have been around since steam engine days, and self-propelled mowers since 1951. I don't see anything special about this.

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