Do You Engage at WOT?
Oct 01, 2013
There are two schools of thought on the proper way to engage a combine's separator and header. Some folks say it doesn't matter if the combine is at wide open throttle (WOT), or at low idle--just put the thottle to full speed and shove the lever ahead or flip the switch: "That's why they put rubber drive belts on them."
Other combine operators are conscientious about always idling back the engine before engaging the separator and header. Their theory is that gentle is better when it comes to machinery.
Older combines that use a lever to engage the separator are one reason engineers switched to using electric or hydraulic clutches to engage separators. The guys who gently eased the levers ahead risked slipping the belts, building heat into the belts and pulleys, and eventually damaging those drive components. Testing proved it was better to idle the engine back, then slam the lever ahead so the belt(s) engaged as quickly as possible to minimize slippage.
So the engineers went to electric or hydraulic clutches to engage combine components. The on/off nature of those clutches ensure components engage quickly to minimize belt slippage. Some owner's manuals actually say, or imply, it's permissible to flip the engagement button or switch with the engine at full throttle. And a lot of combine across the country are operated that way, year after year.
So, it's permissible to engage separators and headers at WOT. That doesn't mean it's optimal. I could go through a lot of calculations regarding mass and momentum and the physics of the situation, but the bottom line is that it's easier on components if they're engaged at low engine rpms.