18th Century Cannon Wheels
Historic Camden Foundation Executive Director, Cary Briggs asked me if I wanted to make a cannon carriage for the events surrounding the military burial of the remains of 14 Revolutionary War soldiers unearthed at the site of the Battle of Camden. The Historic Camden Foundation was gifted a replica of a cannon (just the barrel) that George Washington awarded to the Chatham Artillery militia company of Savannah in 1791 after he had visited the city. And it is this cannon (complete with carriage and wheels) that will be used to carry the remains of the Fraser Highlander found at the battle site. It is customary for the British to place a platform over a cannon to carry the coffin of an officer, whereas in the US a caisson is used to perform this service. I have wanted to make wooden spoked wheels for quite a while and was very excited to have this opportunity.
A book initially published in 1752 on cannon carriages, wheels, limbers, caissons, and other military gear was provided for my use and it gave me the sizes of the various parts of the cannon carriage. It specified a 58” tall wheel for the 6-pound cannon we were to receive. The hub of these wheels was specified at 12” in diameter and 14” in length. The fellows were 4” deep and 2.5” thick. From these two sets of dimensions I could determine the length of the spokes.
The next challenge was the species of wood to use for the various parts. To make wheels that will survive in the elements for any length of time, very specific woods need to be used. During the 18th century when so much depended upon the reliability of wooden wheels, one did not use just any wood that happened to be at hand. The wood had to be tough, hard to break, and rot resistant. I chose Ash for the fellows, Hickory for the spokes and Sapele for the hub.
Hubs were glued up and roughly shaped into cylinders.
The next step was to turn them on a lathe to “true” and shape the outer portion of the hub.
The spoke mortises needed to be cut next. To get the proper size for the mortises, I cut the spokes to shape and created the tenon on one end.
This tenon was then the size of the mortise. I set up a jig on my drill press so that the drill bit was always cutting straight down toward dead center. My lather has an indexing wheel which allowed me to mark 12 parallel lines exactly equidistant from each other.
The drill bits (I first used a Forsner-type bit) hogged out most of the material. Then the corners needed to be squared and the sides flattened.
Once the mortises were cut and checked for fit, I remounted the hub on the lathe and began to cut out the center for the tapered axle. I drilled out as much as I dared to without endangering the edge of the finished taper. It was just a long process of cut a little and check the fit. Rinse and repeat.
I made a plug that was the proper size and taper of the axle. I coated the plug with chalk, put it in the opening, turned it just a bit, and the chalk left inside would indicate where I had to cut a bit more.
With the tapered inside cut I could then work on setting the hub bands. The bands need to be just a tiny bit smaller than the circumference of the hub. This measurement cannot be accurately obtained with a tape measure or string or the like. A wheelwright uses a tool called a “Traveler”. Here are two examples. Jack, one of the blacksmiths at Historic Camden, made the large one. I made the smaller one.
For the hub bands the smaller traveler is used. Starting at a mark on the hub and the traveler, a rotation is carefully begun, and a mark is placed on the traveler when it reaches the mark where I began. This measurement is then transferred to the band. The band needs to be bent in the approximate size circle. I tried rolling out the measurement on the flat stock and it ended up very short of what I needed. I still don’t understand why. Also, one must roll the traveler in the same direction each time or there will be a discrepancy. The exact measurement is then reduced on the steel band by 2 tenths of 1 percent which works out to about 1/16th of an inch.
With the bands cut to length, they are welded together and ground flat and checked for “circle” taking out as many flats and dips as possible. This is done with a hammer and anvil “horn” or mandrel. Next each band is individually heated to expand it so it will just slip into place on the hub. It is quickly cooled and it tightens up very solidly. I used the forge at Historic Camden and the help of the blacksmiths there to set the bands.
The fellows are Ash 2 ½” thick and 4” deep. I made a pattern by carefully tracing out a 58” circle on a 60” square of plywood, dividing it into 6 equal parts and tracing the resulting fellow to transfer onto another piece of plywood. I then traced 12 fellows on the Ash I had acquired in North Carolina. Using my bandsaw, I carefully cut to the line of each fellow.
The spokes are connected to the fellows with round tenons cut on the ends of the spokes. I had to drill holes at the correct intervals to fit the tenons with equal spacing. I had to make a jig to hold the fellow so that I would drill in line with the center of the wheel. The spokes are spaced two to a fellow and the joint of the fellows is midway between the spoke spacing.
The spokes are made of Hickory which is a very tough wood. They are set at an angle to the hub forming a “dish” shape. I used 4 degrees as the angle. The spokes also are tapered from the hub to the fellows. I first cut the tenons that would fit into the hub at 4 degrees. Then I made a jig to cut the taper of the length of the spoke being careful to cut the correct side of the 4-degree tenon.
I rounded the edges and then began to assemble. I put two spokes into a hub to show the “dish” of 4 degrees.
The next step was to cut the round tenons on the other end of the spokes. These tenons fit into the holes drilled into the fellows. The challenge is these tenons are at 90-degrees to the hub. That is, they cancel out the 4-degree angle.
Because the Hickory is so hard, I removed much of the excess material leaving a 1” square that would then be rounded. Using a very old tool much like a pencil sharpener, I rounded the square so the tenon cutter would begin cutting easily.
This is the tenon cutter mounted in my drill press.
To hold the spoke at the proper angle to cut the round tenon, I needed to make a jig for my drill press.
Before assembling the wheels I thought it would be easier to apply a coat of primer to all the parts disassembled, so I did. Then all the spokes are inserted into the hub and driven home.
Then the fellows are driven onto the spokes.
I used splines on the outer edge to keep the fellows lined up. The tires cover the splines so they are not seen.
Next task was to true the outside of the wheel, that is, make it round. I mounted the plug I had made to the faceplate of my 8’ diameter wood lathe and carefully adjusted it so it ran true. I then slipped on the wheel and wedged it in place.
Next, I mounted a router to my tool rest with a flat-bottomed core bit. After some adjusting, I was able to remove the high and low spots on the wheel.
Steel 3/8” thick and 2 ½” wide are the tires for these cannon wheels. I asked Midlands Tooling to bend these for me in a 58” diameter and leaving enough extra material to trim once I had the exact measurement.
Using the large traveler, we (Rick, one of the blacksmith from Historic Camden and I) measured three times to ensure accuracy. The same rule for bands on the hub applies to tires for wooden wheels; that is, to make them 2 tenths of 1 percent smaller than the circumference of the wood. At 58’ diameter it works out to about 5/16”. We carefully cut, welded, and ground the weld flat.
Trying to heat the steel to 900 degrees with LP gas was an exercise in futility and we soon gave up. Instead, we built a fire at Historic Camden and were able to achieve much more than 900 degrees.
I built an octagon holder for the wheels that I set up on horses. Once the tire was hot, we used holders that the blacksmith made to pick it up and drop it on the wheel. Water was immediately applied and I used clamps to pull and push the wheel into line with the steel.
Stacey Ferguson recorded us shrinking the second tire onto the wheel. She did some outstanding editing.
Here are the wheels on the axle. They are tilted outward and with this tilt the spokes on the bottom side aim straight down. After years of trial and error it seems that wheelwrights determined that this arrangement was the strongest and most durable for wheels. There would have been very little “gentle” terrain for a cannon as it was dragged from battle to battle. The wheels had to endure bouncing and sideways jostling all while supporting a very heavy hunk of metal.
Here is a picture of the wheels on the axle and the cannon carriage mounted on the axle. You can see the wheel dish a little better in this photo.
The next post will describe cutting the axle and building the carriage.