In the Shop
As a farm machinery mechanic and writer, Dan brings a hands-on approach that only a pro can muster. Along with his In the Shop blog, Dan writes a column by the same name as well as the Shop Series for Farm Journal magazine. Always providing practical information, he is a master at tackling technical topics and making them easy for all of our readers to understand. He and his wife, Becky, live near Bouton, Iowa.
"I need more power, Scotty...!"
Sep 09, 2013
Sometimes engineers and mechanics feel like the beleagered Scotty on the old TV show "Star Trek." No matter how well we get the machines running, somebody is always calling and telling us they, "need more power!"
Sometimes we can tweak something or find a malfunctioning component to give customers more power. But in many cases, when we check out the circumstances, the customer may be partly responsible for the perception of inadequate power.
Let's use a 400-horsepower combine as an example. In your mind, right now, make an estimate of how many horsepower it takes to thresh, separate, clean, and elevate grain into the grain tank. Hold onto that horsepower estimate for a minute.
Engineers have told me that an 8-row cornhead in 200-bushel corn at 20 percent moisture can pull as much as 125 horsepower. More, if it's a chopping head. They also tell me that the straw chopper on an 8-row combine in "average" corn can pull more than 100 horsepower.
Most combines have some sort of aftermarket grain tank extension. You can check my math, but when you fill an extended grain tank till grain is stacked high enought to impress the neighbors and threaten low-flying aircraft---you're adding weight to the combine equivalent to setting a 200-hp front-wheel assist tractor with duals in that grain tank. So, can we figure an extra 50 horsepower is required to power a combine more than half full of grain through the field...?
Then we'll pull an extra 25-hp when we engage the unloading auger, and at night when we've got all those lights turned on the 200-amp alternator pulls a few extra horse, and the air conditioner takes a few horse, and if we've got a corn reel or other extra hydraulic motor running on the combine it's going to pull a few horse. All of a sudden we've used up close to 300 out of the available 400 horsepower. Leaving 100 horsepower to do the actual threshing, separating and elevating of the grain.
How does that 100 available horsepower compare to your estimate of how many horsepower it takes to operate the combine's separator when it's hogging through high moisture corn or green stem soybeans?
My point is, no matter how many horsepower engineers put into combines, and no matter how many horsepower mechanics are able to squeeze out of the those machines, there are never enough for the way we use them. So the next time your combine lugs down and slow-shaft speed warnings start buzzing as engine rpms fall below optimum levels, pull back on the hydro lever, and let the poor machine catch its breath. And then think about how fast you're pushing the corn head, how tough and green are the stalks the straw chopper is gnawing on, and how high is the extension you added to the grain tank.
If your combine was a starship, there would be a frustrated First Engineer like Scotty down in the engine room shouting, "But Captain, I'm giving her all she's got!"