Continuous Hay Press

Presses existed; Dederick claims a continuous baling press — fed and compressed without stopping to unload. Note that word; it is the advance.

Loosely fill a box with dry grass or straw. Record its volume and mass, and compute its density. It will be tiny — hay is mostly air.

Make a stiff open-topped box and a plunger that slides down inside it. This is the baling chamber.

Push the plunger down hard and hold. Measure the compressed volume. Same mass, far less space — density has jumped. Record it.

Read the force on the plunger with the spring scale as you compress. It rises steeply the more you squeeze — the last bit of air is the hardest to remove.

Drive the plunger with a long lever pivoted near the plunger end. A small pull at the far end becomes a large push on the hay. Measure both forces.

Divide the push on the hay by the pull on the lever. That ratio is your mechanical advantage — how the machine turns a horse's modest force into baling tonnes.

While it is squeezed, pass twine around the charge and tie it. Release — and it stays compressed. The tie holds the bale; the press only has to make it, not keep it.

Leave the first tied bale in the box and press a new charge against it. The finished bale IS the back wall — this is the trick that makes the press continuous, no door to open.

Each new pressing shoves the chain of bales along and out the far end. Feed keeps going in, bales keep coming out — a production line, not a batch.

Stack the loose hay and the bales in the same footprint. Far more hay fits as bales — the reason a barn or a railcar can hold a season's feed.

Take equal volumes of bale and loose hay and weigh them. The ratio is the compression the press achieved — and the factor by which shipping got cheaper.

The patent. US 170,999, "Improvement in baling-presses", granted 14 December 1875 to P. K. Dederick of Albany, New York. Dederick is generally credited with the continuous hay press from the early 1870s, and the design principle is still used.

The invention is a change of cycle, not just a stronger press. Early presses were batch machines: fill a box, ram the charge, open a door, drag out the bale, start again — slow, and much of the time spent not pressing. Dederick's continuous press keeps a chain of bales in the chamber so that each new plunger stroke compresses fresh hay against the resistance of the bale already made (step 9), and simply pushes the whole train along and out the end (step 10). There is no unloading step, so the machine runs steadily as fast as hay is fed. That is the same insight as any continuous process: never stop the line to unload.

Why compression is worth so much force. Hay is perhaps nine-tenths air, and steps 2 and 4 show a bale can be a small fraction of the loose volume. But the last air is the hardest to remove — the force climbs steeply (step 5) — which is why the press needs the lever or toggle that multiplies a horse's pull into tonnes (steps 6 and 7). And crucially, the press does not have to hold the compression: the twine tie does that (step 8), so the machine only makes the bale and moves on. Dense, tied bales are why hay could be stored through winter, loaded onto wagons and railcars, and shipped from where grass grows to where animals are kept (steps 11 and 12).

Where it leads. The stationary continuous hay press is the direct ancestor of the field baler — the machine towed behind a tractor that picks up a windrow, compresses it, ties it and drops finished bales across the field, and of the big round balers that replaced it. Every one of them is doing what you did here: crush the air out, tie it off, and push the bale out the back so the next one can form. It is the packaging step of agriculture, and packaging is what lets a harvest travel.