Small Engine Gearbox Ratio

[ningus bingledong]

What would be the best ratios to use in my gearbox to squeeze the most speed out of a Small Engine for two Small Propellers and a Generator?

[XLjedi]

I'm working on a small boat with a pair of electric props meselfs... and asking the same question.

I'm looking for compromise on speed vs. range though. I need at least 5km on 7 batteries.

[Console]

The gearbox ratios will depend of the size, form and weight of the ships. I would say max is 1:2, arrows pointing to the engine.

[Aven]

While there is a best for your ship, it is almost impossible for anyone else to determine for you. Gearing a boat is largely trial and error and personal preference. There are too many variables to outright say you should be using x as your gear ratio. There is, however, a progression you can follow to help you figure it out.

1) Determine the purpose of the gearing. Are you gearing for speed, torque, fuel efficiency, or some combination of? Since I play with limited fuel, I personally shoot for a gearing that gives me something close to a 1:1 ratio of m/s of speed to fuel burn per km, i.e. a ship that can cruise at 25-30 m/s at a fuel usage of 25-30L per km traveled, with another gearing for higher speeds when needed.

2) Determine the baseline capabilities of your craft. Set your engine/s to a 100 RPS cap and see what your RPS caps at on full throttle at a 1:1 ratio. If it's less than 20, you are going to struggle to boost RPS with gearing and should consider adding more engines before proceeding. If your engines overheat, determine the maximum RPS you can run out without overheating and set that as your engine RPS cap if you can't be trusted to monitor engine temperature. This is also a good time to fix any stability issues with your hull design.

3) Setup feedback. After you have your engine and hull layouts finalized, load up your console with displays: engine RPS, output RPS, temperatures, fuel usage, torque. These numbers collectively will help you determine gearing.

4) Start testing gears. This process will go quicker if you have 2 or 3 gearboxes to cycle per test, however if your ship only has a single engine, it is unlikely that it will need access to a broad range of gears. Start with 1:1, throttle until you hit your desired cruising speed. If you can't hit it, you need more engines. If you can hit it, note your fuel usage, and move on to 6:5. Throttle up to your speed, note the fuel usage, move on to 3:2. Continue this process until your ship can no longer throttle to your desired speed. If you get to 3:1 and still have not maxed your throttle, start combining gears with 3:1. Once you know your maximum gearing, consider the performance and fuel usage of the tested gears and determine the gearing you want to use.

5) Enjoy your ship. At least until you decide it's too small, too slow, too weak, too unstable, too fuel inefficient, or needs more features like an automatic transmission, alternator, better cooling, or a broader range of gears available. Then you build a new boat and start the whole process over again.