Often when a fellow borrows a truck from someone who had driven it countless years or miles, and the one borrowing it values the friendship of the owner and wants to treat his property with a gentle hand, he will ask, “Where’s the sweet spot?”
When a vehicle comes from its maker, it will have some form of operator’s manual that spells out the acceptable operating parameters for that vehicle. Included are the type and amount of motor oil, coolant, fuel and other things it needs to operate correctly. Somewhere it will also suggest how fast the engine should turn and how low a speed it should be lugged before selecting a lower gear to put the engine at a higher speed.
Somewhere in print, possibly on the data plate, usually found on a door pillar of the cab, will be the amount of weight the vehicle is rated to haul.
My 1959 VW Beetle did not have a tachometer. Instead, around the speedometer there were red lines. About the 15 mph mark there was a single red line. About 25, there were two red lines and somewhere above that there were three red lines.
At the first red line, it was time to shift the manual transmission out of first gear and into second. The two red lines were the “red line” for second gear, meaning to keep it in that gear going any faster would harm the engine. There was no red line for the top speed, but at 72 mph the engine was turning as fast as it would go – and unless you were on flat ground without a headwind, or going downhill, it would never reach that speed.
Vehicles with a tachometer, which tells the engine’s revolutions per minute (rpm), will generally have an upper area that is graduated in red lines. To force the engine faster than the start of the red line area is not only flirting with causing the engine to self-destruct, but seriously dating that outcome.
Identical vehicles will have the same written instructions as to the operating range of the vehicles. Within that operating range, there will be an engine speed that is most efficient for that individual vehicle. Variables after leaving the factory will affect this most efficient operating speed.
Things like the weight of equipment generally aboard, add-ons that decrease or increase wind resistance as it moves up the road, all add to the identical from the factory rigs not having the same sweet spot for optimal economy. A conscientious driver, as in the person paying for the fuel, will soon figure out the correct speed to drive said vehicle for the best balance of speed and fuel mileage.
This is why the borrowing individual referred to earlier will ask about the sweet spot.
At the beginning of the double-nickel (55 mph) speed limit, which was an attempt to reduce overall fuel usage, there was an issue. Most vehicles, including heavy trucks, were geared for operating efficiency usually considering the then-70-mph nationwide speed limit. Many of the trucks, when slowed to the mandated 55 mph, would require downshifting to a lower gear to avoid catastrophic damage to the engine because it was so slow it was lugging.
The guys actually paying for the fuel found that these trucks, geared for higher speeds, were much more fuel-efficient at 62 mph than at 55. As the 55-mph speed limit stretched on from being a momentary fad, the truck makers started gearing the newer trucks to be most efficient at the mandated 55 mph.
It isn’t just highway vehicles. It was standard practice while baling hay with the two- and three-tie balers to have (especially inexperienced) operators be directed which gear to operate the tractor in and at what speed to keep the engine turning. This sweet spot for baling hay gave the most uniform bales for that grower’s stand of hay.
Probably a more critical sweet spot to identify has to do with interpersonal relationships. The supervisor needs enough weight behind his or her directives so that those working for said supervisor do what it is that they are supposed to be doing. Too much weight behind directives, and those on the ground will continue following explicit directives even when they can plainly see that those directives are sinking the ship. Worse is when an employee, child or spouse is so terrified of the wrath of the supervisor that they will never let on that an upset was simply the result of someone making a mistake. A competent supervisor will welcome having an employee pointing out a better way. They will also value an employee who will state that the employee’s human error caused an upset.
This simple sweet spot, of being approachable, no matter what, beats all possible scenarios where the wrath of a supervisor, husband or wife rules out someone clarifying an upset as a simple error that better training or clearer communication could have prevented.
