Early Industrial Navigation (1830–1850)Marine Engineering & Hydraulics

Lincoln Expansible Buoyant Chambers

US 6,469

Variable Displacement Chambers Operated by Shafts, Ropes, and Pulleys

Inventor(s)Abraham Lincoln

Grant Date1849-05-22

Filing Date1849-03-10

LocationSpringfield, Illinois

Lincoln's 1849 specification claims a vessel-side buoyancy apparatus: expansible air chambers, sliding spars fixed to their bottoms, and a main shaft with ropes and pulleys. Turning the shaft lowers and expands the chambers to displace water; reverse rotation contracts them for protection.

USPTO PDF

Engineering Analysis & Physical Principles

How It Works: Step-by-Step Mechanical & Physical Breakdown

Lincoln proposed adding controllable displacement rather than unloading a grounded vessel. His patent puts a collapsible air chamber at each side of a vessel. A shaft-and-rope mechanism drives the chambers downward; trapped air makes them displace more water, so the vessel rises relative to a bar or shoal.

The Core Breakthrough Mechanism

The apparatus uses a chamber with rigid top g and bottom h and flexible waterproof sides. Vertical spars D pass through the chamber and attach to its bottom. Endless ropes f running from main shaft C over sheaves pull the lower structure down. Check ropes e retain the upper side, so the chamber opens and admits air through openings m. Reversing C draws the assembly back into a compact protected position.

Interactive Real-Time Physical Simulation

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Pneumatic Expandable Buoyancy & Riverbed Shoal Navigation

Buoyant Lift Force

313kN[1]

Draft Reduction

1.75ft[L]

Shoal Keel Clearance

0.25ft[L]

Displaced Air Volume

31.9m³[1]

Air Bellows Inflation75 %

Steamboat Weight380 T

Riverbed Shoal Water Depth3.5 ft

Interval ghosts

Clearance0.3 ft · [-1, 4]

Detailed Component Architecture

1Expansible buoyant chamber A

A rigid-topped and rigid-bottomed chamber with flexible waterproof sides and ends.

The specification names plank or metal for top g and bottom h, with india-rubber cloth or another waterproof fabric for the flexible enclosure. Its lift follows Archimedes' principle: each added submerged volume displaces water and supplies buoyant force $F_B = \rho g V$ .

19th-C. Term: india-rubber clothModern: waterproof elastomeric chamber fabric

2Sliding spars D and main shaft C

Vertical spars attach to chamber bottoms and are driven from a longitudinal main shaft.

The spars D move freely through openings in the chamber tops but are fastened to the bottoms. Endless ropes f, wound around C and routed over sheaves, translate shaft rotation into controlled vertical motion of the bottoms.

19th-C. Term: shafts or sparsModern: vertical guide rods and a rotary actuator shaft

3Check ropes e and air openings m

Retaining ropes set immersion while openings exchange air during expansion and contraction.

Check ropes e hold the upper sides when the lower sides are forced down, opening the chamber. Their length governs immersion depth. Openings m admit and emit air, so the mechanism does not require a separate pressure vessel or pump.

19th-C. Term: check ropesModern: travel-limiting tension members

Interactive Mathematical Physics & Rigorous Mechanics

Governing Equations & Colorized Principles

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Archimedes' principle

materials

Mathematical Governing Law

{\htmlClass{eq-term eq-term-var_0_f_b eq-term-emerald}{\htmlData{var=var_0_f_b}{\textcolor{#059669}{F_B}}}} = {\htmlClass{eq-term eq-term-var_1_rho_water_ eq-term-sapphire}{\htmlData{var=var_1_rho_water_}{\textcolor{#2563eb}{\rho_{water}}}}} {\htmlClass{eq-term eq-term-var_2_g eq-term-amber}{\htmlData{var=var_2_g}{\textcolor{#d97706}{g}}}} {\htmlClass{eq-term eq-term-var_3_v_displaced_ eq-term-crimson}{\htmlData{var=var_3_v_displaced_}{\textcolor{#dc2626}{V_{displaced}}}}}

Terms:

Plain English DecoderHover or tap any highlighted phrase

In the physical operation of this mechanism, is determined by the action of scaled by and constrained by . Expanding the side chambers increases the water volume displaced by the vessel-and-chamber system. At equilibrium, the buoyant force balances the vessel's weight, so extra displaced volume raises the hull and reduces draft.

F_B

Mechanical Force Vector

Net dynamic vector force acting upon the mechanism

Newtons (N)[M L T^-2]

Governs mechanical force vector within archimedes' principle: Expanding the side chambers increases the water volume displaced by the vessel-and-chamber system. At equilibrium, the buoyant force balances the vessel's weight, so extra displace...

Physical Principle & Engineering Insight

Expanding the side chambers increases the water volume displaced by the vessel-and-chamber system. At equilibrium, the buoyant force balances the vessel's weight, so extra displaced volume raises the hull and reduces draft.

Rotary-to-linear rope drive

materials

Mathematical Governing Law

{\htmlClass{eq-term eq-term-var_0_s eq-term-emerald}{\htmlData{var=var_0_s}{\textcolor{#059669}{s}}}} = {\htmlClass{eq-term eq-term-var_1_r eq-term-sapphire}{\htmlData{var=var_1_r}{\textcolor{#2563eb}{r}}}}{\htmlClass{eq-term eq-term-var_2_theta eq-term-amber}{\htmlData{var=var_2_theta}{\textcolor{#d97706}{\theta}}}}

Terms:

Plain English DecoderHover or tap any highlighted phrase

In the physical operation of this mechanism, is determined by the action of scaled by . For a rope wrapped around shaft C, a shaft rotation

\theta

moves rope length s in proportion to drum radius r. The sheaves redirect that motion down the sides of the vessel to the sliding spars.

s

Surface Area / Planform Area

Total geometric contact, lifting, or radiative surface area

Square meters (m²)[L^2]

Governs surface area within rotary-to-linear rope drive: For a rope wrapped around shaft C, a shaft rotation $\theta$ moves rope length s in proportion to drum radius r. The sheaves redirect that motion down the sides of the vessel to th...

Physical Principle & Engineering Insight

For a rope wrapped around shaft C, a shaft rotation $\theta$ moves rope length s in proportion to drum radius r. The sheaves redirect that motion down the sides of the vessel to the sliding spars.

Interactive Schematic Sheet (Fig. 1)

Source drawing sheet, PDF page 1: side elevation of a vessel with buoyant chambers combined therewith and expanded.

1.00x

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Why It Still Matters

The document is a precise early statement of adjustable displacement: it identifies the chamber, its guides, the rope transmission, air exchange, and a reversible stowed state. The claim is narrower than the general idea of floating a vessel because it requires that particular working combination.

Legal Claims Decoder (1 Numbered Claims)

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Claim #1Independent Master Claim

1/1

Verbatim Historical Legal Text

“What I claim as my invention and desire to secure by letters patent, is the combination of expansible buoyant chambers placed at the sides of a vessel, with the main shaft or shafts C, by means of the sliding spars or shafts D, which pass down through the buoyant chambers and are made fast to their bottoms, and the series of ropes and pullies, or their equivalents, in such a manner that by turning the main shaft or shafts in one direction, the buoyant chambers will be forced downwards into the water and at the same time expanded and filled with air for buoying up the vessel by the displacement of water; and by turning the shaft in an opposite direction, the buoyant chambers will be contracted into a small space and secured against injury.”

Plain English Engineering Translation

Claim 1 covers the combination, not buoyancy in the abstract: expansible chambers at vessel sides; main shaft C; sliding spars D fixed to the chamber bottoms; and ropes and pulleys or equivalents. Rotation in one direction must drive the chambers down, expand them, and fill them with air to buoy the vessel by water displacement; reverse rotation must contract and protect them.

Key Protected Innovations:

expansible side chambersmain shaft Csliding spars Dreversible rope-and-pulley actuation

Historical Legal Impact:

The sole printed claim expressly combines the structural parts with both operating directions. The specification's statements that details may vary do not turn the claim into ownership of every buoyancy aid.

The Historical Bottleneck

The specification names a direct operating problem: reduce a vessel's draught sufficiently to pass bars or shallow water without discharging cargo.

Why Prior Art Failed

•The source identifies cargo discharge as the avoided response to a bar or shallow water.
•The source also distinguishes a compact protected state from an expanded working state, making a permanently protruding float unsuitable for the stated arrangement.

The Breakthrough Insight

“Instead of altering cargo mass, the apparatus changes displaced volume with side-mounted chambers and a reversible mechanical drive.”

After the Grant

The grant is dated May 22, 1849. The facsimile does not state whether the proposed apparatus was built or adopted.

Civilizational Impact

The source provides a fully specified nineteenth-century mechanism for adjustable vessel displacement, including its geometry, force transmission, stowage, and air exchange. This record makes no further historical-impact claim without a separate cited source.

Further Context

The execution on PDF page 3 reads A. LINCOLN, with Z. C. ROBBINS and H. H. SYLVESTER as witnesses.