Shaft Reducer
What It Does
Shaft Reducer decreases the number of shafts your draft requires by merging shafts that behave identically. If two or more shafts are raised on exactly the same picks, the threads on those shafts can share a single shaft — each in its own heddle — reducing the total shaft count. The cloth structure stays exactly the same.
This is useful when a draft uses more shafts than your loom has, or when you want to find the most efficient shaft assignment for a pattern. For example, a 10-shaft draft where several shafts have identical raise patterns might reduce to 6 or fewer.
Opening Shaft Reducer
Ribbon: Tools tab > Shaft Reducer button (in the Optimize group)
The Shaft Reducer Dialog
Settings (Left Panel)
Current Shafts Shows how many shafts your draft currently uses. This is your starting point.
Unique Raise Patterns Shows how many distinct raise patterns exist across all your shafts. This is the absolute minimum number of shafts needed to produce the same cloth — you can't reduce below this number without changing the fabric. If this is already equal to your current shaft count, no exact reduction is possible.
Target Shafts The number of shafts you want to reduce to. Set this to match your loom. The default is set to the number of unique raise patterns (the maximum exact reduction).
Allow Multi-Treadle When checked, enables approximate reduction below the unique pattern count. This groups similar (but not identical) raise patterns onto the same shaft, which changes the cloth slightly. The result reports the number of cells affected and the error percentage so you can judge whether the approximation is acceptable.
When unchecked (default), only exact merges are performed — the cloth is preserved perfectly.
Preview (Right Panel)
Shows your original tie-up on the left and the reduced tie-up on the right, side by side. This updates after the reduction completes so you can compare before applying.
How to Use It
Go to Tools tab > Shaft Reducer
Review the Unique Raise Patterns count — this tells you the minimum achievable with exact reduction
Set your Target Shafts to the number your loom has
If the target is below the unique pattern count, check Allow Multi-Treadle for approximate reduction
Click Run Reduction
Review the result message and preview
Click Apply if you're happy with the result
Understanding the Results
After running a reduction, you'll see one of these outcomes:
Success (exact) — Shafts with identical raise patterns were merged. The message shows the reduction (e.g., "10 → 6 shafts"). The cloth is unchanged. Click Apply to use it.
Success (approximate) — With "Allow Multi-Treadle" checked, similar patterns were grouped together. The message includes the number of changed cells and error percentage (e.g., "approximate: 12 cells changed, 0.8% error"). Review the preview carefully before applying.
Cannot reduce further — Your draft already uses the minimum number of shafts for its unique raise patterns. Every shaft has a different behavior across the picks.
Cannot reduce without multi-treadle — The target is below the unique pattern count. Enable "Allow Multi-Treadle" to attempt approximate reduction.
Step-by-Step Example: Fitting a Draft to Your Loom
You have a draft that uses 12 shafts, but your loom only has 8:
Open Shaft Reducer from the Tools tab
You see "Current Shafts: 12" and "Unique Raise Patterns: 7"
Set Target Shafts to 8
Click Run Reduction
The result shows "Reduced 12 → 7 shafts, 10 treadles" — even fewer than your target
Check the preview to see the new tie-up
Click Apply
Your draft now uses 7 shafts. The threading is reassigned so that threads which had identical raise patterns now share the same shaft, each on its own heddle. The cloth is identical.
What Changes in Your Draft
When you apply a reduction:
Threading — Threads are reassigned to fewer shafts. Multiple threads that were on different shafts but had identical raise/lower behavior now share the same shaft number.
Tie-up — Rebuilt for the reduced shaft count. May have more or fewer treadle columns depending on how the patterns combine.
Treadling — Rebuilt to match the new tie-up. Converted to single-treadle mode.
Liftplan — If the original was a liftplan, it's converted to standard tie-up mode.
The cloth — Unchanged (exact reduction) or slightly modified (approximate reduction with multi-treadle).
Exact vs. Approximate Reduction
Exact reduction merges only shafts with perfectly identical raise patterns. The cloth is preserved cell-for-cell. This is the default and the safest option.
Approximate reduction (Allow Multi-Treadle) groups similar patterns together when exact reduction can't reach your target. It uses a greedy clustering algorithm that minimizes the total number of cloth cells that change. The error percentage tells you how much the cloth differs from the original:
0% — No changes (same as exact)
Under 1% — Very close approximation, differences may not be visible in the woven fabric
Over 5% — Noticeable changes to the pattern structure
Limitations
Minimum 2 shafts — A draft must have at least 2 shafts.
Exact reduction floor — Without approximate mode, you can't reduce below the number of unique raise patterns.
Approximate is lossy — When using "Allow Multi-Treadle" to go below the unique pattern count, the cloth will differ from the original. Always review the error percentage before applying.
Maximum 128 shafts/treadles — TempoWeave's array limits apply.
Tips
Undo works — Ctrl+Z (Cmd+Z on Mac) reverts the entire reduction in one step.
Check unique patterns first — The "Unique Raise Patterns" count tells you immediately whether reduction is possible and how far it can go without any cloth changes.
Pairs well with Simplify Draft — Simplify Draft's Straight Threading mode also reduces shafts, but it additionally reorganizes the threading into a repeating straight sequence. Shaft Reducer preserves the threading order more closely.
Pairs well with Treadle Reducer — After reducing shafts, the tie-up may have more treadles. Use Treadle Reducer to reduce treadle count with double-presses if needed.
Compare with Warp Spread — Shaft Reducer is conceptually the opposite of Warp Spread, which distributes threads across more shafts.
Quick Reference
Target Shafts
Unique pattern count
2–128
Allow Multi-Treadle
Off
On / Off
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