Oh no, I don't think you should step up the ratio. You want a reduction. The foot should have adequate reduction already so direct drive to the driven shaft should be in the ballpark, but if you want to get seriously into the engineering aspects you can calculate the ideal total ratio for a given prop, based on the optimum power/speed curve of the motor. Electric motors hate to be driven under load at insufficient speed. They tend to overheat, for the main thing. Of course you don't want to overspeed the motor, either. Usually there is a constant published for the motor, and multiplying it by your system voltage will give you the ideal speed to run the motor at full power. For a displacement hull, if the motor is sufficiently powerful, full power setting should be about hull speed with a clean hull and prop. So if you know what prop RPM will give you that speed, you can calculate the desired reduction ratio, keeping in mind the ratio you already have in the foot of the outboard.
I am not using an outboard. I simply replaced my old Atomic 4 with electric. My reduction gearbox is fully enclosed and made by Baldor. They only make whole number ratios, such as 2:1, 3:1, 4:1, etc. Mine is a 2:1 unit. Thrust bearing is integrated into the gearbox. This unit is fairly compact but It it probably not what you want for an outboard.
You do need a tachometer of some sort to figure out where you are at on motor RPM.
Adjusting prop size and pitch to match the load (hul) and motor properly is probably going to be much simpler than diddling with the gears.
| Reply via web post | • | Reply to sender | • | Reply to group | • | Start a New Topic | • | Messages in this topic (24) |
No comments:
Post a Comment