Micro hop plucker/stripper

Monday, September 17th, 2018

The need

You may have noticed that I am a bit obsessed with hops. Currently, I am running three small yards for our experimental hop breeding program. Hops are wonderful to grow, but can be a real pain to pick. Hand picking takes about 1 hour per plant – meanwhile, picking machines cost hundreds-of-thousands of dollars and can typically be as big as a warehouse. There are a few “smaller” machines on the market, but the size and cost is still prohibitive for the hobby grower.

The build

Picking fingers

The core of any hop harvesting machine is the picking fingers. These metal loops are used to grab on to the hops cones and pop them off. They need to be strong, flexible, strongly attached, and have to correct angle. I practiced making some of my own – but, due to time constrains, opted to purchase some from Sea to Sky hop solutions.

These are replacement fingers for the Wolf 140/170 picking machine. 56 fingers was enough to cover 4 picking bars about 30″ long.

Spindle

To hold the fingers, I simply created a spindal with 4 bars created from cheap 2×2 lumber. These are spaced around the metal shaft with 8″ plywood circles and a few more 2x2s. Super simple and cheap, but more than strong enough for a picker this size.

Just be sure to chamfer the edges of the 2x2s to mount the picking fingers … before you put the spindle together.

Box

The spindle is mounted inside a 30×36″ box using inexpensive pillow bearings. The box needs to be ridged and heavy enough to keep from moving when you pull the heavy hop bines through.

The box is also important as it keeps your hop cones from flying across the yard when they are plucked. Originally my box was open, but I quickly added a hinged lid with neoprene “car wash style” flaps. This looks a bit funny, but effectively keeps most of the cones contained.

Power

For power, I used a simple 1750rpm, 120v motor. This needs to be slowed down significantly for the spindle to run safely. A 15″ pulley slows the speed down to a reasonable 175rpm (about 3 rotations per second).

As a basic safety measure, I hooked the motor up to a cheap dead-man switch. This way it only runs when your foot is on the pedal.

Sorting

The machine only strips the hops. Sorting done separately, but isn’t difficult. We simply poured the hop/leaf mixture in front of a box fan – this blow away about 80% of the leaves.

Success?

The hop stripper reduced the harvest time for the Barber hop yard to 10% of last years effort – half a day and the whole yard was down, stripped, sorted, and ready to dry.

Pros

  • Stripping the cones works extremely well (much better than expected)
  • Very stable – no need for extra weight
  • Safer than expected. Does not grab fingers. Dead-man switch stops it quickly.

Cons

  • Sorting cones from leaves needs to be improved
  • It will sometimes grab tangled bines (especially near the ends)
  • Small, but still bigger than I wish (pain to store the 364 days its not in use)

Ideas for the next version (Mark II)?

  • Do we even need the heavy box?
  • Idea: a simple spindle and guards mounted above the bed of a pickup truck
  • Would be ultra stable and portable

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