Hiscox item 1605 shows a mechanical car brake with an adjustable bar linking the shoes. A small lever movement applies them, and wheel friction can help tighten the brake. Explore the arrangement and calculate ideal clearance take-up from entered gap and movement values.
Brake Clearance and Take-Up Calculator
Enter declared shoe gap, lever take-up, connecting-bar adjustment take-up and wheel radius. The worksheet reports ideal clearance closure only; it does not predict force, torque, stopping distance, heat or safe braking.
Equation Used
- The clearance calculation assumes lever take-up and bar-adjustment take-up add directly.
- Ideal contact occurs when effective take-up equals the declared initial shoe gap.
- Wheel radius determines the circumference result; the drawing uses a fixed illustrative wheel size.
- Link pivots, leverage, compliance, friction, self-energizing gain, shoe force, torque, heat, wheel/rail adhesion, stopping distance, redundancy, controls, structure and safety are excluded.
The entered take-up closes the example shoe clearance. Additional movement after contact is reported as ideal overtravel, without calculating deformation or force.
An adjustable bar links the two brake shoes
Hiscox item 1605 places an adjustable connecting bar between the brakes so a small movement of the brake lever brings the shoes into operation. When applied from the front platform, wheel motion and friction on the front shoe help tighten the brake, reducing operator effort.
The schematic shows the shoes, connecting bar and lever; leverage and friction forces are not calculated.
A historical car-brake linkage
Hiscox identifies the mechanism as a car brake operated from the front platform. The mechanism applies friction shoes through a mechanical linkage; the calculation is limited to its entered clearance and take-up values.
Clearance and take-up calculations
These identities indicate ideal contact state only. They do not calculate braking force.
Declared take-up example
For 8 mm initial gap, 5 mm lever take-up and 2 mm bar-adjustment take-up, effective take-up is 7 mm and 1 mm gap remains. A declared 300 mm wheel radius gives 1,885.0 mm circumference.
Contact state and braking force
Closing the gap establishes an ideal contact state. Braking force and stopping performance also depend on leverage, compliance, friction and the vehicle conditions. Overtravel alone cannot determine shoe force, and this calculator does not size a vehicle brake.
Novel car-brake questions
Is this an eddy-current brake?
No.
Does overtravel represent elastic shoe force?
No. It is the amount by which entered take-up exceeds the initial gap; deformation and force are not calculated.
Does the page size a safe vehicle brake?
No.
Novel car-brake reference
- Hiscox, Mechanical Movements, page 398, item 1605: primary public-domain figure and caption documenting the adjustable connecting bar and friction-assisted shoe action.
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