Another "what motor" thread.
I have an Anteo tug, 3 foot, about 10kg. I bought it secondhand, after a bit of fettling it's working nicely, but is underpowered. Most of the time I'm using full throttle, and it's just about reaching a nice cruising speed - eventually. Previous owner told me that he found it a bit sluggish too.
It's currently fitted with a torpedo 800 motor and a 2:1 O-ring pulley reduction. I need to stick with the pulleys, as the propshaft is very low in the hull, with bulkheads that would get in the way of a direct drive motor. Running on two 8-cell NiMH packs in parallel, turning a 50mm 5 blade brass prop.
Motor spec suggests that the shaft will be turning at around 2000rpm on full throttle - which I guess explains why it's a bit slow. Raboesch prop is rated up to 7000rpm.
I'm guessing that if I fitted a motor that turned twice as fast, the tug would in theory go twice as fast. Drive losses probably mean a bit less than that at full speed, but twice the power when manoeuvring, and maybe 50% more top speed, would be about right I think?
That means I would want the propshaft turning at 4000rpm, so the motor turning at 8000rpm. I'd switch to using a pair of 3s LiPos in parallel, so a motor around 680kv would be suitable - right?
What physical size motor should I be looking at, and have I got my kv calcs right?