Surf Rover - Design & Analysis

Project Description:

In collaboration with Coastal Engineering staff, civil, mechanical, and electrical engineering students, an underwater data collection rover was to be designed, refined, and constructed. This rover was to be able to drive into the surf zone along the sea bed to collect data during inclement weather events to better inform erosion control and other ocean engineering projects.

The surf rover was designed to be powered by an enclosed marine diesel engine, hydraulic pumps, and hydraulically driven tracks. This design necessitated the use of a large vertical snorkel (intake and exhaust) as well as a cooling system that can work in both air and water. My teammates and myself were tasked with designing the snorkel assembly, evaluating and assembling cooling setups, and making engine repairs.

Snorkel Design

As previously mentioned, a snorkel was to extend vertically (25 ft) from the engine enclosure. This design was to prevent excess back pressure and moisture condensation in both the intake and exhaust sections as either would be problematic for the enclosed diesel engine.

To inform this design my team and I calculated back pressure and created a thermal resistance circuit to evaluate performance at different sizes and different materials. After verifying these design calculations, my team was also involved in informing the physical design of the snorkel. That is, how the snorkel mates with the engine enclosure and attaches to the engine.[

Cooling Setup

Evaluation

The surf rover was to operate in both air (driving off the trailer, onto the beach, and into the surf zone) as well as in water (in the actual surf zone. As such, it was necessary for the engine to be cooled in both environments. The solution devised for this problem was intra-structural cooling; intra-structural cooling was hypothesized to leverage the extended surface area of the legs and remove the need of radiators underwater. In this case, the leg forward leg pairs were to cycle coolant (in parallel) from the engine and back.

The initial decision to utilize intra-structural cooling was not informed by thermal or fluid analysis. Main concerns were the sufficiency of the engine’s existing cooling pump (+ fresh water intake pump), and actual cooling performance. Major and minor losses experienced by coolant flow were calculated and a coolant pump test was devised. Additionally, heat transfer calculations were performed in both air and water setups (below). Informed by these calculations, suggestions were made about design changes, testing procedures, and physical construction.

Assembly

In order to properly implement intra-structural cooling, the current fresh water cooling system had to be retrofitted. This system (above) was investigated and the necessary retrofit steps (and BOM) were outlined. These decisions further informed the design of the engine enclosure,

Maintenance and Investigation

Before being able to bench test the engine, repairs (above) had to be made to the throttle governor. The engine was also previously equipped with an arduino and relay assembly to prime the glow plugs, start up, run the engine, and collect data (coolant temps, oil pressure, etc). Little documentation was available on this code, and it had to be reviewed and commented.