Last weekend was entirely dedicated to repairing the combine. We (my housemate, Natalie, fellow equipment co-op member, Tristan, and I) started early Saturday morning with a pancake breakfast made from local grains. Yeah yeah, surprise, surprise. Then, we inspected the combine from the top, down and made a to-do list for the weekend and for what we could postpone for post-harvest.

To-Do List

Replace fluids, belts, filters. While these are reasonable upgrades for a used machine, the combine obviously hadn’t been maintained because it had original filters and belts. For a 1984 machine, those originals should’ve been long gone. The alternator also made a discomforting clicking noise. Also, everything needed to be cleaned.

The critical questions:

  1. Are the header adjustments leaking hydraulic fluid?
  2. Where are the marks for aligning gears when replacing the timing belt?
  3. Why doesn’t the machine thresh?

I know, that last one is a double-take. Why buy a combine that doesn’t thresh? Then it’s not combining anything, it’s just cutting! The person I bought it from said that he wasn’t getting full threshes. Was it the concave? No, we could tell it closes. Was it the cylinder speed? The adjustment mechanism wasn’t moving, so that was something to investigate. We felt confident that we could fix it. This weekend would test our self-assurance.

  1. Are the header adjustments leaking hydraulic fluid? Thanks to Natalie, the housing, gears, hydraulic compartment, conveyer belt, and the whole machine received a deep cleaning. This way we could see if hydraulic fluid was leaking, which, if it was, would be bad for many reasons including getting on the grains going up the conveyer belt. It turns out the bolts needed tightening and all was fine.

2. Where are the marks for aligning gears when replacing the timing belt? The timing belt is essential for ensuring the engine receives fuel at the right time. If you own a car, you know that if the timing belt goes then your whole engine is ruined. The timing belt was ripping, so we decided to proactively replace it. Once the belt is off, all the gears affected by the timing belt need to be realigned. Typically marks on a stationary part of the engine and the rotating part indicate what the starting position is. We could not find the alignment for one part. In fact, we didn’t find it until Sunday! It was in an non-intuitive place, behind a gear!

From the outside. It’s behind the top, left pulley
Upon closer inspection behind that top, right pulley (top left in previous photo)

3. Why doesn’t the machine thresh? This is the essential question. I’m going to cut through the drama I endured and tell you that someone had readjusted the shiv that enables cylinder speed adjustment. (Cylinder speed determines how fast, and therefore how much energy, grain heads are propelled against a fixed part to shatter the head and release the grains. This is how you get clean grain, rather than a bunch of spikey grain heads.) The shiv is the junction between one plane of motion and another so you can crank something around vertically that moves something else that’s horizontal. The shiv was cross-threaded such that the axel inside has been stripped and the metal worn away. This means two problems: can’t turn the adjustment and the axel is wobbly.

The difficulty with adjusting the cross-threaded shiv was unlocking them. Imagine closing a jar and you find that it’s crooked. It’s usually hard to undo. Imagine that but with more threads and fragile parts. Specifically, soft bronze.

Cross threaded and crooked shiv
Gap between inside and outside

We decided to put the steel part in a vice and try to twist off the bronze. The bronze was obviously eaten away and battered, so we wanted to be sensitive and not crush its soft threads. I thought of putting a thick towel between it and oil can grips. It turned out that one of the oil can grips had teeth that perfectly matched the threading!!!


We managed to get the gears apart and holy moly did I feel fabulous! So much so that I had a fashion photo shoot with the bronze gear.


What a relief and accomplishment! After all that, Natalie and I drove to Dillon Beach and sat in the sand. There are few things more satisfying to me than problem solving, but decompressing at a beautiful Pacific coast beach is up there. Using her observant, field scientist skills, Natalie noticed dolphins by the shore! We watched them peek their dorsal fins between waves as the sun set.