The Conical Coal Scuttle: One Sheet, No Bottom to Wear Through

"The object of this invention is to simplify and cheapen coal-hods or 'scuttles,' and at the same time render them more convenient for discharging the coal therefrom, more durable, and much easier repaired when injured by wear than coal-hods of ordinary construction". "This coal-hod is made mainly of a single piece of sheet metal, and resembles in its outline an inverted hollow cone, the apex of the cone being the bottom and center of the hod. The ordinary horizontal bottom is consequently dispensed with." A base, "a truncated cone, oval in form", is riveted on so it stands. "In the ordinary coal-hod the bottom is the first to fail and the most difficult to repair. When, from either wear or corrosion, my coal hod fails, the process of repairing is very simple. A single piece of sheet metal is coiled, fitted, and fastened in the hod, and the work is done."

Find the gravel's friction angle: pour a heap slowly onto a board, measure its height and the width of its base, and take the slope angle as arctan(2 x height / base). Or tilt a board with a few stones on it and read the protractor when they start to slide. Tape over the outlet of a kitchen funnel so it is a cone with no hole. Half-fill it with gravel and tip it slowly over a bucket, reading the angle on the protractor when the last stone leaves. Do the same with a straight-sided metal bucket. Compare both with the notebook's rule, tip = wall angle + friction angle, using your own friction angle.

**George Smith** of Williamsburg, New York, received US 124,093, dated 27 February 1872. **Honest limits.** The tipping rule treats the last piece as sliding on a single flat wall at its friction angle; real coal rolls, wedges and bridges. Smith's "slightly tilted" is about pouring from a full hod, where the coal runs off the top of the heap; the rule is for the last piece. The friction angle and volume in the notebook are examples. Your protractor readings are the measurement.