In this episode of Your Questions Answered, the focus is on the belt drive system of a Cummins 6.7 engine conversion. The discussion covers bypass oil filtration, crankcase breather hoses, raw water pumps, managing large bus alternators, and solutions for squeaky belts. The depth of detail provides valuable insights into custom engine build challenges and solutions.
Bypass Filtration and Oil Management
Questions about installing a bypass oil filtration system to control soot and oil contamination were addressed. The currently installed Amsoil bypass filtration does not keep the oil as clean as hoped, though the oil remains sufficiently clean for now. Interest in centrifugal filtration systems exists, but no final decision has been made. On the coolant side, there are no current filtration systems installed, but this might be considered in the future.
Crankcase Breather Hose Options
The crankcase breather hose routing is still undecided. The main concern is preventing oil vapor from entering the turbo inlet, although this may be the eventual destination with the addition of a large air-oil separator. Atmospheric venting out of the stack is another possible option under consideration.
Custom Parts Durability and Documentation
Custom heavy brackets and components are designed to be robust and not typical wear parts, especially with smooth inline six-cylinder engines. Belt and pulley specifications are carefully documented, including keeping belt sleeves and pulley samples in charts and logs, to assist future owners or repairs. This thorough documentation ensures continuity and ease of maintenance.
Raw Water Pumps and Bearing Reliability
The raw water pumps, adapted from Detroit engines, are driven off the camshaft and designed for torque loads. They feature double rows of large ball bearings, making them well-suited for the belt-driven setup without concern for side loading. This design has performed well over time without failures, indicating high-quality construction.
Large Bus Alternators Integration
Large bus-type alternators (24V/48V) are used on the main generator set with wig speed regulators and integrate with Victron battery management systems. These alternators can be controlled to turn on/off at certain charge levels and follow charge commands, although there are currently some CAN data limitations being addressed.
Belt Tension and Squeaking Solutions
The custom belt drive system uses stretch belts, which are ideally installed once and left on. Repeated removal may overstretch the belt, causing squealing on startup. Applying pressure on the belt during startup often stops the screeching. A new belt is planned to see if it resolves the issue. Potential solutions like weighted or spring-loaded tensioners were considered but are currently low priority.
Electric Water Cooling Loop Considerations
Fabricating an electrically driven water cooling loop with large AC motor pumps was considered. Benefits include reliability and eliminating impeller maintenance. However, dependency on continuous AC power and inverter reliability is a drawback. Magnet-driven pumps without shaft seals could be an elegant solution, but the traditional mechanical impeller pumps remain favored for their simplicity and reliability.
Maintenance and Repair at Sea
For repairs during extended trips, a welder powered by the lithium bank is always aboard. Metal stock is carried to patch or fabricate temporary fixes until permanent repairs can be made on land. This preparedness ensures the vessel remains operational despite custom-made parts.
Bracket Modifications and Belt Tension Improvements
Modifying the belt bracket by cutting and clamping to increase tension is considered. The proximity of mounting bolts to the belt limits how much the bracket can be adjusted. Replacing bolts with flathead countersunk bolts is a planned method to gain additional belt tension. This approach should add about a half inch of tension, sufficient to reduce belt slip and squeal.
Bearing Lubrication in Raw Water Pumps
Sealing and lubrication of raw water pump bearings is critical. While the pumps are believed to have sealed bearings, confirmation is pending after disassembly. Despite uncertainty, the pumps have performed well without bearing failure, demonstrating robust design and construction.
| Topic | Key Points |
|---|---|
| Bypass Oil Filtration | Installed Amsoil system; not perfect but functional; future improvements possible |
| Crankcase Breather Routing | Options include turbo inlet with separator or atmospheric venting |
| Raw Water Pumps | Camshaft-driven, heavy-duty bearings, no side loading concerns |
| Belt Drive Tension | Stretch belts used; new belt planned; tension increased by bracket modifications |
| Electrical Accessories | Large bus alternators integrated with BMS; electric water pump considered but not implemented |
| Maintenance at Sea | Welder and metal stock on board for repairs |