Side-Stand Mechanism with Spring Return and Sensor Mount

The problem

Riding off with the side stand down can cause a fall, so many two-wheelers cut motor power when the stand is down, using a stand position sensor. The stand must hold firmly in both positions, support the parked scooter at a stable lean and carry the sensor reliably. It is a compact project combining mechanism, spring and sensor packaging.

Objectives

• Define parked lean angle, stand length and the two stable positions.
• Design a stand, pivot bracket and over-centre extension spring.
• Use a Motion study to check the spring holds the stand in both positions.
• Package a sensor bracket and check stand and bracket strength.

What you need

Key concepts

Over-centre spring

A spring whose line of action crosses the pivot as the stand moves. On one side it pulls the stand up, on the other it holds it down.

Parked lean angle

The angle the scooter leans when parked; too upright and it falls over, too far and it is hard to lift.

Stand position sensor

A switch or magnetic sensor that tells the controller whether the stand is down, used as an interlock to prevent riding off.

Holding torque

Spring force times its perpendicular distance from the pivot; it must exceed small disturbances such as vibration in both positions.

Step-by-step guide

1. 1

   Set requirements

   Define an example scooter: kerb mass 100 kg, centre of gravity height from a CAD estimate, ground clearance at the stand pivot and a target parked lean angle of about 8 to 12 degrees, a common range. Define the up position tucked within the body line and the down position resting on the ground. Choose a sensor type and note its switching distance and mounting needs.

   Checkpoint: A requirements table with mass, CG, lean target, positions and sensor details.

2. 2

   Calculate geometry

   In Excel, compute the stand length and pivot position that give the target lean angle when the foot is on the ground, using the wheel contact points and the pivot location. Compute the load on the stand from the parked scooter's weight and lean geometry. These numbers fix the stand length and the parked load case. Check the result on a 2 per cent slope in both directions to see whether the scooter stays stable or rolls off the stand.

   Checkpoint: A stand length and pivot location giving the target lean, and a calculated stand load.

3. 3

   Model the stand and bracket

   Model the stand leg as a bent tube or forged bar profile using a sweep, with a foot pad at the end. Model a pivot bracket that bolts to the frame, with bores for the pivot bolt and stops for the up and down positions. Choose steel from the material library. Add spring anchor points on the leg and the bracket.

   Checkpoint: Parts rebuild and the leg rotates around a defined pivot axis.

4. 4

   Lay out the spring

   Place the spring anchors so that the line between them crosses the pivot as the stand rotates from up to down. Check the spring length at up, crossover and down positions with sketch dimensions. Choose an example extension spring with a rate and free length so it is always in tension. Record the spring force at each position. Keep the spring stress within the maker's limits at its longest stretch, which is usually at the crossover point.

   Checkpoint: Spring line crossing the pivot between the two positions, with tension in both.

5. 5

   Assemble with stops

   Mate the bracket to a frame plate, add a concentric mate for the pivot and Angle Limit mates or contact stops for the up and down positions. Check by dragging that the stand moves between stops. Add the sensor and its bracket with a target or magnet on the stand so it is within switching distance in the down position only.

   Checkpoint: The stand moves between stops, and the sensor target sits within switching distance only when down.

6. 6

   Run the Motion study

   In a Motion Analysis study, add a linear spring between anchors with the chosen rate and free length, turn on gravity, and drive the stand with a rotary motor from up to down. Plot spring force and motor torque against angle. The torque changes sign at the crossover point, showing two stable positions. Without Motion Analysis, compute holding torque by hand at several angles.

   Checkpoint: A torque curve that changes sign at crossover, with holding torque in both positions above an example minimum.

7. 7

   Check foot operation force

   From the torque curve, compute the force the rider's foot must apply at the stand's foot tab to move it past crossover. Compare with a comfortable foot force target. Adjust anchor positions or spring rate to balance holding torque against ease of use. Re-run the study after changes. Repeat for retracting the stand, which is usually done by the foot or by the rider rocking the scooter upright. Check the sensor target stays clear of the switch face throughout, so it is not struck.

   Checkpoint: Foot force below the target while holding torque stays above its minimum.

8. 8

   Check strength

   In a static study, fix the bracket bolt holes and apply the parked load at the foot, in the direction from the lean geometry. Use a pin connector or bolt connector at the pivot. Add an extra case for a person pushing down on the parked scooter, using a stated factor. Check factor of safety and deflection. Refine the mesh at the pivot bore and the leg bend, and confirm that stress changes by less than about 5 per cent.

   Checkpoint: Factor of safety above an example 2 and foot deflection small enough not to change lean angle noticeably.

9. 9

   Check clearances and sensor protection

   In the up position, check ground clearance and lean clearance during cornering using a lean-angle envelope. Make sure the sensor and its cable are shielded from stones and water, and that the bracket cannot be bent by a kick. Run Interference Detection in both positions. Route the sensor cable along the frame with clips and a drip loop, and give the connector an IP rating suitable for spray, to be confirmed against IS/IEC 60529. Check that a mud build-up on the foot cannot stop the stand reaching either stop.

   Checkpoint: No interference in either position, and the sensor is shielded within the frame or a guard.

10. 10

    Drawings and report

    Make drawings of the stand leg, pivot bracket and sensor bracket with pivot bore tolerances and bend data. Write up geometry, spring layout, motion results, foot force, strength check and sensor packaging. Recommend a test of sensor switching over many stand cycles and a parked stability check on a slope. Give the spring part number or full specification, and the sensor's switching gap with its tolerance.

    Checkpoint: Drawings and a report with torque curves, strength results and a test plan.

Testing & validation

• Lean angle in CAD matches the hand calculation.
• Motion study torque curve shows two stable positions.
• Foot force and holding torque meet targets.
• Strength check factor of safety above the target.

Expected results

A side stand and bracket with an over-centre spring, motion-derived holding torque and foot force curves, strength checks and a protected sensor mount ready for an interlock.

Take it further

• Design a centre stand and compare lift effort.
• Run a fatigue study for repeated stand use.
• Add an auto-retract mechanism linked to throttle or motion.
• Test the sensor switching distance on a printed prototype.

Viva and review questions

Learn it at DIYguru

These DIYguru courses and programmes teach what this project needs.