A stop motion detects a process fault and commands the machine to stop. This page shows an electrical warp stop motion: a broken thread lets a metal drop wire fall onto a contact bar. The stop signal releases the drive and applies a brake. The timing calculator estimates travel under a stated braking assumption.
Stop Motion Interactive Calculator
Watch a broken warp thread release its drop wire, then follow clutch release and braking. Enter measured response times to estimate shaft travel.
Equation Used
- Entered delays occur in series.
- Brake time means engagement to zero speed.
- Uniform angular deceleration is assumed.
- No certified stop-performance or safety rating is calculated.
Stopping travel assumes constant speed during detection and release, followed by uniform deceleration during braking. Use measured machine delays.
Thread support, contact closure and machine stop
Each intact warp thread supports its drop wire. When the thread breaks, the wire falls and bridges insulated conductors in the contact-bar arrangement. The resulting signal operates the machine stop circuit.
The cutaway follows one failed thread among intact neighbours. A separate schematic shows the drive clutch opening and the machine shaft slowing under braking. Electrical connections are signal paths, not mechanical rods. Exact clutch and brake construction depends on the loom.
Applications
Warp stop motions detect broken threads during weaving. The drop wire and electrical contact bar shown here are one arrangement; detection and stopping hardware vary with the loom. The calculator is a timing estimate for a specified machine response, not a universal loom performance specification.
Stopping angle with uniform braking
For speed n rpm and detection, release and brake times ts, tl, tb in milliseconds, total time is T=ts+tl+tb. Running angular speed is 6n degrees/s. If speed falls linearly to zero during braking, travel is θ=6n(ts+tl+tb/2)/1000 degrees.
The constant-speed comparison θmax=6nT/1000 treats the entire interval as running speed. It is an upper comparison only if the speed never exceeds its initial value. The elapsed-time margin 60000/n−T compares total stop time with one initial revolution period; it is not a safe operating limit.
Example at 180 rpm
With 8 ms detection, 35 ms release and 120 ms braking, total response time is 163 ms. Uniform braking gives 111.24° of shaft travel, or 0.309 revolutions. The constant-speed comparison is 176.04°.
Changing brake time affects both total time and the triangular area under the braking speed curve. Real travel can be obtained by integrating a measured speed-time trace.
Use measured delays
The animation is an explanatory sequence, not an automatic reset procedure or a validated safety circuit. Thread detection, clutch release and actual braking must be evaluated on the relevant machine. A single revolution is only a timing reference; it does not establish an acceptable stop distance.
Questions
Why does the shaft keep moving after detection?
The release takes time, then the rotating mass must decelerate.
Why does the animation repeat?
It resets the demonstration so the sequence can be viewed again. A real machine requires its specified fault-clearance and restart procedure.
Are the default delays universal?
No. They are example inputs, not manufacturer specifications.
Technical references
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