Spoked Wheels

Part of Roads and Transport

Building lightweight, strong spoked wheels — the dominant wheel design for three millennia.

Why This Matters

The spoked wheel is one of the most elegant engineering solutions in human history. By replacing the solid disc with a series of slender spokes under compression, wheel makers of the ancient Near East around 2000 BCE created a wheel that was 60-70% lighter than its solid predecessor while being equally strong for most loads. This reduction in unsprung weight meant animals could pull faster, farther, and with less fatigue. Spoked wheels enabled the fast war chariot, revolutionized transport, and remained the dominant wheel design for almost 4,000 years.

The key insight is structural: a solid wheel is strong because it has material everywhere. A spoked wheel is strong because it puts material exactly where the forces are. Spokes carry the load from the rim to the hub in compression and slight tension depending on their position in the wheel’s rotation. The iron tire holds the whole system in compression, keeping every joint tight.

Building spoked wheels requires more skill than solid wheels — a spoke shave, a lathe or equivalent, precise hole drilling, and understanding of the dished design. But the investment in skill pays back in faster vehicles, longer animal working life, and wheels that can reach much larger diameters without becoming impractically heavy.

Components of a Spoked Wheel

Every spoked wheel has five distinct components, each with specific requirements:

Component	Function	Traditional Material	Key Property
Hub	Center block containing axle hole and spoke mortises	Elm (interlocked grain resists splitting)	Must not split under spoke driving forces
Spokes	Transfer load from rim to hub	Oak, hickory, ash (straight grain)	Must resist both compression and bending
Felloes (rim segments)	Curved sections forming the outer ring	Steam-bent ash, or sawn oak	Must resist compression from iron tire
Iron tire	Band around outer rim	Wrought iron, mild steel	Holds wheel in compression, wear surface
Linchpin and washer	Retain wheel on axle	Iron	Withstands full wheel load

The Hub

The hub is the most complex component. It must be large enough to hold all the spokes without the wood between spoke mortises splitting, yet the axle hole must be small enough to keep the hub compact.

Hub dimensions (typical for a medium wagon wheel, 120 cm diameter):

• Hub length: 20-25 cm (longer hubs distribute spoke forces over more material)
• Hub maximum diameter: 15-18 cm
• Axle hole diameter: 5-7 cm (for a wooden fixed axle) or matched to iron axle diameter
• Number of spokes: 10-14 (fewer spokes for light wheels, more for heavy)

Turning the hub: Ideally turned on a lathe to ensure perfect roundness and concentricity of the axle hole. A pole lathe (see woodworking articles) is sufficient. Without a lathe, a hub can be shaped by hand using adze, drawknife, and spokeshave — but achieving the necessary accuracy requires patience.

Mortising for spokes: The spoke mortises in the hub should be cut at a slight outward angle — this creates the “dished” shape of the finished wheel. The angle is typically 3-6 degrees from perpendicular to the axle axis. All mortises must be at the same angle and precisely equally spaced around the hub circumference.

Spoke mortise shape: For round tenon spokes, drill the mortise slightly smaller than the spoke tenon diameter. The spoke will be driven in tightly, wedged by the wood’s resistance. This interference fit is what keeps spokes tight without glue.

The Spokes

Spokes must be straight-grained — any deviation of grain from spoke axis creates a weakness that will eventually fail. Split (riven) spokes are better than sawn spokes for this reason: splitting follows the grain, sawing crosses it.

Making spokes from riven blanks:

1. Select straight-grained billets of seasoned oak or hickory
2. Split with a froe along the grain into roughly square sections slightly larger than the finished spoke
3. Shave to the finished profile with a drawknife and spokeshave, working from a shaving horse
4. The finished spoke is tapered: the hub end (tenon) is cylindrical, slightly larger than the mortise; the rim end (also a tenon) is slightly smaller; the middle section is the largest diameter

Spoke dimensions (for 120 cm wheel, 12 spokes):

• Total length: approximately 50-55 cm (from hub shoulder to rim inner face)
• Middle diameter: 3.0-3.5 cm
• Hub tenon: 2.5 cm diameter, 4-5 cm long — this is the interference fit tenon
• Rim tenon: 2.0-2.5 cm diameter, 2-3 cm long — enters the felloe mortise

The taper is critical: The spoke is widest in the middle and narrowest at both ends. This distribution of material puts the most wood where bending stress is highest (at the middle) and reduces weight where it is less needed (at the ends).

The Felloes

Felloes are the curved sections that form the wheel rim. A typical wheel has 6-8 felloe sections, each curved to the wheel’s radius, with two spoke mortises cut into the inner face.

Making felloes — two methods:

Method 1: Sawn felloes

1. From a wide plank, mark the inner and outer curves of the felloe section
2. Saw to shape with a bowsaw
3. Cut the spoke mortises — holes drilled from the inner face at a slight angle to match the spoke-end angle

Sawn felloes can be made quickly but the grain may run across the wood at the weakest point (the tips of the felloe). Using quartersawn lumber (grain lines running across the thickness) reduces this problem.

Method 2: Steam-bent felloes

1. Steam a straight piece of ash in a steam chest (see woodworking articles) for 30-60 minutes per centimeter of thickness
2. Bend quickly to the wheel radius while hot, clamp to a form, and allow to cool
3. The bent piece retains the curve after cooling
4. Cut spoke mortises after bending

Steam-bent felloes have grain running continuously around the curve, making them stronger and less prone to splitting at the tips. This is the traditional wagon-wheel method.

Assembly: The Sequence Matters

The wheel assembly sequence is critical. Each step builds on the previous, and mistakes at any stage are very difficult to correct.

Step 1: Drive the Spokes into the Hub

1. Test-fit each spoke tenon in its mortise before driving. The tenon should require light hammer blows to seat — if it drops in freely, it is too small and will eventually loosen; if it will not start, it is too large and will split the hub.
2. Drive spokes into the hub alternating sides (1, opposite 7, then 2, opposite 8, etc.) to equalize driving stresses
3. Drive to full depth — the spoke shoulder should seat firmly against the hub face
4. After all spokes are driven, verify all are equally angled outward (the dishing angle)

Step 2: Fit the Felloes

1. Fit each felloe section onto two adjacent spoke tenons. The felloe must be brought onto both tenons simultaneously — it cannot be slid on sequentially.
2. Drive the felloe down with firm hammer blows, alternating sides of the felloe to seat it evenly
3. The felloe should seat firmly with no rocking
4. The outer face of adjacent felloes should align smoothly — bumps or gaps indicate a spoke is slightly off angle

Step 3: Check the Dishing

Before going further, check the dish (the cone-like transverse shape of the wheel).

Place the wheel flat on a floor. All felloe points should contact the floor. If the wheel rocks, one or more spokes are at a wrong angle. Check by measuring from the hub face (at the far side from the floor) to the floor — it should be uniform around the wheel. Typical dish depth: 2-4 cm for a 120 cm wheel (the hub projects 2-4 cm beyond the plane of the felloe outer face).

Step 4: True the Rim

The outer rim face must be round (not egg-shaped) for the iron tire to fit properly.

Mount the wheel on an axle between two supports (or on a lathe). Rotate slowly. Mark high points where the rim is too large. Reduce with a drawknife or rasp. Check frequently. The rim should be within 2-3 mm of round around the full circumference before tire fitting.

Step 5: Fit the Iron Tire

See Metal Tires for the detailed shrink-fitting process. The tire, when fitted and cooled, pulls all felloe sections tightly together and compresses the entire wheel structure into a rigid unit.

The Tire Tightens Everything

When you drive in spokes, they should feel snug but you should not see the wheel distorting. When you fit the felloes, they should seat fully but maybe not perfectly tightly. When the iron tire contracts and grips the rim, it pulls all gaps closed, tightens all loose joints, and puts the entire wheel under compression. Trust the process — the tire does the final tightening.

Maintenance and Repair

Loose spokes: A spoke that can be wiggled indicates a failed tenon fit. Tighten by driving a thin hardwood wedge into the mortise alongside the spoke tenon. If multiple spokes are loose, the wheel may need re-tiring — the iron tire has expanded slightly, releasing compression.

Spoke replacement: Remove the tire (heat and lever off). Remove the broken spoke by drilling out or splitting the old tenon. Cut and shape a new spoke, drive in, replace the felloe if damaged, and refit the tire.

Seasonal swelling and shrinking: Wood swells in damp conditions and shrinks in dry conditions. In very dry seasons, wheel joints can loosen. Keep wheels in moderate humidity when not in use, and grease the wood lightly to slow moisture loss.

Inspection: Before each long journey, tap each spoke with your knuckle. A firm, ringing tap indicates tight, healthy wood. A dull, hollow sound indicates decay or a loose joint requiring attention.