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3. Stability test → fill the cup with water, then repeat the previous tests → omitted due to timing
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Prototyping Results
| Design Style | Scaling Down Tests | Climbing Tests | Design Issues |
|---|
| Triple Bogie | - Stable throughout 1.1
- Rear rocker consistently has some air time, worse the steeper the drop
- Would likely be more successful if the CoM was closer to the back half of the drivetrain
- Flipped over at high speeds down 1.2's drop
| | - Optimal 4-bar linkage position: top pins are spread apart while the lower pins are close together (i.e. upside down trapezoid)
- Lower pins need to be close together to allow front wheels to lift up heights
- Upper pins need to be spaced out to prevent locking at the lower pins (due to them interfering with each other)
- Want to find the optimal distance between upper pins such that we eliminate the over-centre linkage
- Locking → if the chassis tips too far forward, weight is balanced on just the front bogies and rear stays suspended
- Able to drive out of this position?
- Rocker attempts to twist if the load is uneven between the pair of wheels
- Rocker joint is generally weak
- Flipping → At too high of speeds, will flip over one of the 4-bar linkage pins
|
| Double Bogie | - Frequently locks up if not driving carefully
- Most successful when it goes slowly down an obstacle, reducing the chances of the chassis weight toppling forwards and locking the bogies
- Most successful when it scales down angled one way/one wheel at a time climbs down
| | - Locking → if the middle wheel becomes slightly suspended, uneven/non-centred weight distribution from the chassis (i.e. from being tipped forwards) will pull the front and rear wheels towards the centre of the drivetrain. This then pulls the middle wheel into a locked position, completely suspended in the air
- Difficult to get out of this position
- Uneven weight distribution occurs from too high of speeds → would want to operate this style of drive at a slow speed while climbing obstacles
|
| - Very stable throughout 1.1 and 1.2 → no issues
- For 1.3, it doesn't look like it would reliably make the drop even if the wheels were powered → Bogie lift/extension is the most limited out of all of the designs since it's a smaller bogie arm
- Could only compensate by making the overall rocker-bogie system taller
| | - Constrained to the depth/height of obstacle since the front bogie is limited in height
- Flipping → Bogie may flip over bogie pivot point if the wheel gets stuck on the obstacleis jammed
|