|This Old Wheel
Strakes, cones and other wooden wheel technologies in the 17th Century.
by: Rick Orli
(c) 2000 richard j. orli
First Published in The Moderne Aviso, April 2001
|Wheels are a ubiquitous technological
artifact, and worth attention since 17th C. wheels differ in several details
from those made in last hundred and fifty years.# The following paragraphs outline the
technology, with most details based on George Sturts outstanding contemporary
account of his trade in the late nineteenth century - "The Wheelwrights
Figure 1. Parts of the Strake Wheel, 1650 Style to the left, with strake bands, and 1700 Style to the right.
Figure 2. Wheel to Axle orientation, and Dish#, illustrated in a limber.
The Axle angles down, and the angle of the cone at the end of the axle is the same, and the dish is also the same angle... such that the spoke bearing the direct load is perpendicular to the ground. This produces the distictive 'flare out' look of vechicles with dished wheels.
Wheel technology was revolutionized in the 1830's when the strake method of shoeing a wheel was replaced by the hoop tyre method. The blacksmith using the new way makes a one piece tyre with a single welded join in the form of a hoop, exactly measured so that it is just smaller than the wheel. He heats the tyre until reddish hot, which causes it to expand, and hammers it onto the wheel. The cooling tyre shrinks, creating an extremely tight fit binding the several parts of the wheel together. The new method is clearly superior, allowing a lightly constructed tyre wheel to match the strength of a strake wheel with a 20- 40% weight savings. Also, the shrinking force of the tyre is such that the construction can be less tight (and less labor intensive), so as to allow the wheel to set into place without warping the spokes. Even what might have been a flaw, such as a cracked hub, is closed up by the tyres force. However, it was also a new and exacting technology, one which, at the least, required a means to evenly heat a large metal tyre and quickly and accurately handle it while red hot. Even as the technology became well established, only specialized factory wheelwrights could make big tyred wheels - smaller shops with unspecialized equipment could only mount tyres under 50 inches or so in diameter. For this reason, Sturts shop continued to build big straked wheels for freight wagons and dung carts to the 1880s, and repair them long afterward. *
Sturt built strake wheels much as they were built in the late 17th C, but again there were two other technological changes. The late 17th C marked the gradual elimination of the strake band, replaced with more and heavier nails. The first all-metal axles and cones (the end of the axle on which the wheel rode) appeared. The early 19th C saw the increasing until ubiquitous use of manufactured metal skeins (or "boxes," the metal work driven into the wheel which was to ride on the axle) and cones.
Several differences between tyre and strake wheels stand out. Strake wheels of the same size had one less felloe, and more massive construction. Since the tyre could be counted upon to draw its wheel tightly together, the tyre-less strake wheels had to be built stronger, and "dish" had to be built into the wheel when it was being morticed. Instead of round spoke holes in the felloes, into which the spokes would be firmly driven as the tyre cooled and contracted, the strake wheel builder had to cut out tight and exact square mortices and tongues, which would be driven together by sledges. In contrast, as mentioned above, the wheel for a tyre had to be constructed loosely, with an open joint so as to allow the wheel to settle as the tyre shrunk -- if the joints were too tight, the spokes themselves would bend or break under the pressure.
The wheelwright had to use powerful blows with the sledge to drive the spoke into the stock with the perfectly tight fit demanded of a straked wheel. Sturt describes the process:
The wheelwright trimmed the battered end of the spoke into a square end to match the square hole cut for it in the felloe. After hammering the felloe into place, a wooden or steel wedge driven into a precut notch at the end of the spoke locked it into place.
To shoe the wheels with strakes, the smith first cut each strake from an iron bar with cold chisel, and bent it. He then hot-punched the strake for the nails, tapering down, and drilled corresponding holes into the felloes. From the late 17th C, the strake was attached entirely through a set of large nails. The nails were cut square and made to taper down to fit the pinched hole, so that as its head wore down it would not lose its grip. Strucks shop randomly placed nails near the end of each strake, to evenly spread the strain on the felloe wood, and especially to prevent two nails along the same line of grain. Five nails for each strake end was common for 42 to 50 inch wheels.
The wheelwright shoed the wheel mounted vertically, bottom in a pool of water. He tapped the felloes again to ensure they were in place, and clamped them together using a device called a Samson. The smith lay the red-hot strake in place across the felloe joint (on the sole) and "held it down while the wheelwright banged in a nail. Forthwith the other man, at the other end, striking down the iron all along to fit the rim, got in his nail; flames and choking wood smoke leapt up; the men, burning their fingers and wrists, dipped their hands hastily into the pail of water, and smote in their other nails (...) with deft sledge work." The men rotated the wheel down to quench the strake in the water, which boiled with the dissipating heat. The strake drew each pair of felloes together as it cooled and shrank.
Prior to the 1700s, the strakes were attached with the same technique, but for heavy vehicles were reinforced with iron strake bands that wrapped around the felloe and strake. The bands might be applied to the joints of the strakes, the joints of the felloes, or both. In the first case, perhaps, the band was also intended to protect the felloe sole at the 1/4 inch gap not covered by the strakes. Gradually, the strake band became a mere supplementary reinforcement, and then was dispensed with altogether. However, its use lingered longer with heavy wheels, such as for cannon and frieght wagons.
Note the strake bands (reinforcing bands) on the 'figure 3' wheel are used for both the strake and fellow joints, and are of two types. At the strake joint they are simple bands more narrow on the inside; at the wood felloe joint they are 'Y'-shaped (allowing a nail for each felloe). Only strake bands of the narrow strake-joint type are shown on the 'figure 2' carriage illustration. The parts (right) from a six pdr. 17th C. Polish Carriage, thought lost in the Vistula during the Battle of Warsaw, 1656 (detail from R. Brzezinski, Polish Armies 1569-1696, Osprey, 1987) seem to be of the Spanish foot artillery carriage type. The strake bands are exactly as illustrated in Fig. 3 above, and one can clearly see the two types at the felloe and strake joints.
George Sturt also observed that a lathe-turned hub required a large and complicated industrial lathe, driven by water, steam, or animal power. Many hubs made by small shops prior to 1800 were simply neatly turned out with a broadaxe. Indeed, Struts own lathe, built by his grandfather around 1800, was constructed in part from a wheel that had a hand-shaped hub.
So the next time you watch a Three Musketeers or Napoleonic era movie and a carriage pulls up with thin and graceful wheels, and the footman applies the brake to the smooth rim of its hoop-tyre, your illusions can be shattered by achronistic incongruity.**
Figure 5. Wheel Parts, the Axle, etc.
n. Dowel Pins
b. Streak nails
c. Nave Hoops
d. Nave box
g. Rivits for Dowledges
h. Nave hoop stubs
k. Box Pins
The other cannon parts show some items from the 18th C. kit. Also shown, are two specilized implements used only for proofing the gun, and examining it - the Searcher, and Searcher/Retriever.
Figure 6. This illustration from dell'Aqua (1500s) shows the metalwork (H) for a reinforced wood-axle (F), for a cannon carriage. Part (I) seems to shod the rest of the axle end (e.g., the Cone). What I do not understand about this drawing is the lack of a downward tilt to the axle ends.
# Hoop tyres represent a lost ancient technology. The great chariot peoples of 1000-600 BC knew this advanced technology. (See S. Piggot)
##Dish is a measure of wheel concavity. By limiting the range of movement side-to-side, Dish helped prevent the wheel from disintegrating from the side-to-side wobble inevitable in a horse-drawn vehicle on poor roads.
*The hoop-tyre technology was well established in the United States at the start of the Civil War, but was not yet universally used for new wheels. While probably all new factory-made wheels were tyred, many thousands of vehicles used straked wheels - especially older ones and those built or maintained in the back country.
**Not to imply that straked wheels for ultra-light carriages could not be thin and graceful as well, as a straked wheel gig on display at the Smithsonian Institutions American History Museum attests (image to right).
The Wheelwrights Shop. George Sturt, Canto/Cambridge University Press, London 1923.
Straking, An Experiment to Recapture the Technology of Straking a Wheel. Ron Vineyard, Colonial Williamsburg, 1990, in Wheelmaking - Wooden Wheel Design and Construction. Don Peloubet, ed., Carriage Museum of America, Astragal Press, Mendham New Jersey. 1996.
Wagon, Chariot and Carriage. Stuart Piggot, Thames and Hudson Ltd., 1992.