Log Carriage

Part of Mill Construction

The log carriage is the moving platform that feeds timber through a sawmill blade at a controlled rate and angle.

Why This Matters

Before the log carriage, cutting planks from logs required a pit saw — two men working a large two-handled saw, one above the log and one below in a pit, cutting stroke by stroke through heavy timber. The labor required was enormous, and the results were inconsistent. A single plank might take an hour to cut by hand. A log carriage feeding timber into a water-powered saw could produce the same plank in minutes.

For a rebuilding community, this multiplication of productive capacity is transformative. A working sawmill with a proper log carriage can supply enough lumber for construction projects that would otherwise be impossible — roof beams, floor boards, door frames, furniture, boats, and the structural members needed for workshops and mills themselves. The carriage is what converts raw timber into usable dimensional lumber at scale.

The carriage also enables precision that hand sawing cannot match. By setting the log at a specific position and advancing it at a controlled rate, you produce planks of consistent thickness — critical when building anything that requires fitted joints, tight floors, or load-bearing structures. Consistency in lumber means consistency in construction, which means stronger and safer buildings.

Basic Carriage Design

The log carriage consists of three elements: the track, the sled, and the dogs (clamps that hold the log).

The track runs parallel to the saw blade and must be perfectly straight. Traditional tracks used squared timber beams set into the ground or mounted on a timber frame. The track surface should be smooth — either planed wood, or iron strap nailed to the top surface. Two parallel tracks spaced about 1.2 to 1.5 meters apart give the carriage stability. The length of the track determines the maximum log length you can process; 4 to 6 meters is practical for most operations.

The sled rides on the track. It needs four points of contact — one wheel or runner at each corner — so that it doesn’t rock or tip as the log is fed through the blade. Traditional carriages used wooden rollers or iron-tired wheels running in grooves cut into the track. The sled frame itself should be heavy enough to resist vibration but light enough to move freely. Squared hardwood timbers mortised together work well.

The dogs are the clamps that grip the log. The simplest design is a spike-tipped iron bar that can be driven into the log’s end grain or side, then locked in position. You need at least two dogs — one at each end of the log — to prevent rotation during cutting. Dogs must be adjustable so you can position the log at different heights, controlling the thickness of each cut.

Building the Track

Begin by laying out two parallel lines on level ground, spaced to match your carriage width. Drive stakes at intervals of about 1 meter along each line. Cut sleepers (crosswise support timbers) and set them level — use a water level or plumb level to check this carefully. Any twist in the track translates directly into wavy cuts.

Lay the track beams on the sleepers and fasten them down with spikes or bolts. Check the upper surface of each beam with a straight-edge — a long, carefully planed board works if you don’t have a metal straightedge. Any high spots must be planed down; low spots can be shimmed with thin wood strips.

If you have iron available, nail iron strap (about 3mm thick, 50mm wide) along the top running surface of each track. This dramatically extends the life of the track and reduces friction. Without iron, harden the wood surface by charring it lightly and then planing smooth, or by applying hot linseed oil.

The track must extend past the saw blade by at least the length of the longest log you plan to cut on the infeed side, and far enough on the outfeed side to fully clear the blade before the carriage stops.

Log Dogs and Clamping

The iron log dog is a simple but critical piece of hardware. The basic form is an L-shaped or T-shaped iron bar with a sharpened spike on one end. The spike is driven into the log; the bar locks into a slot or hole in the carriage frame, holding the log at a set height.

For a working sawmill, you need dogs at two or three points along the carriage. Each dog should be adjustable in height — either by having multiple holes in the carriage frame at different heights, or by using a wedge mechanism that locks the dog at any position. The height of the dog determines the thickness of the cut plank: lower the dog to take a thicker cut, raise it to take a thinner one.

After each pass through the saw, you raise or reposition the dogs to set up the next cut. This is called “dogging” the log. Experienced sawyers can redog a log and have it ready for the next pass in under a minute.

Setting consistent thickness

Cut a series of witness marks on the end of the log before you begin. Mark the cuts you intend to make at 25mm intervals (or whatever standard thickness you’re using). This lets you set the dogs accurately for each successive pass without measuring each time.

Feed Rate and Control

The carriage must move at a controlled rate. Too fast, and the saw blade binds or breaks; too slow, and you waste time without gaining quality. The correct feed rate depends on the saw’s speed, the wood species, and the thickness of the cut.

For a water-powered up-and-down saw, the carriage advances a small amount on each downstroke — typically 3 to 8mm per stroke. This advance is controlled by a ratchet mechanism. The simplest version is a wooden or iron pawl that engages teeth cut into a rack mounted along the track. Each time the saw frame rises (the return stroke), a cam or lever advances the pawl by one tooth. The tooth spacing determines the feed rate.

To change the feed rate, you either use a different rack with wider or narrower teeth, or you add a mechanism to skip teeth. Experienced sawyers learn to feel the correct rate by the sound of the saw — a steady rhythmic cut with no binding.

Maintenance

The carriage track is the highest-wear component. Inspect the running surface after every working day. Look for:

• Grooves worn by wheels or runners — fill with wedged wood strips and plane flush, or replace the affected section of track
• Loosened sleepers — re-spike or re-bolt immediately; a shifting sleeper causes the carriage to rock and produces wavy cuts
• Iron strap lifting at edges — re-nail before the edge catches a wheel and causes a crash

The dog spikes dull with use and may bend if they strike knots. Keep a spare set of sharpened dogs. Resharpen dull spikes on an anvil and whetstone.

The ratchet pawl and rack wear fastest. Cut replacement racks from hardwood (oak, ash, or hornbeam) in advance so you can swap them out without shutting down operations for long.

Handling Large Logs

Logs too heavy to lift manually need mechanical assistance to load onto the carriage. Traditional solutions include:

• Skids and rollers — lay poles from the ground up to the carriage height and roll the log up them
• A cant hook or peavey — a long handle with a pivoting hook used to roll and position logs
• A block and tackle rigged to an overhead beam — allows one person to lift logs that would otherwise require four

Once on the carriage, the first cut is usually made to create a flat face on the log (called “slabbing” the log). This flat face then rests on the carriage, stabilizing the log for all subsequent cuts. The first slab (the curved outer piece) is often split for firewood or used as rustic lumber for non-structural applications.