I recently did a drive efficiency analysis on the table for the 2805.6 1800 KV motor with 9x5 x 3 blade prop,
and it worked out that rpm was about 8,000, thrust was 78 % of expected, motor was 77% efficient, extra thrust due to blade friction was about 75 % effective,
and total drive efficiency over ideal was 55 %
I calculated friction at 0.01 Ca, 2 blades, but actual test prop was a 3 blade.
The motor used less amps and made more thrust on an 8 inch prop of unknown specs.
Computed flow velocity was 21 m/s (about 40 mph).
There doesn't seem to be much room to improve thrust efficiency by adding blades.
was 0.01 Ca a good measure of drag? - a propeller has relatively low profile drag, and higher surface drag.
Is my proportioning of loads and rpm estimate any good? how would errors affect the calculation results?
and it worked out that rpm was about 8,000, thrust was 78 % of expected, motor was 77% efficient, extra thrust due to blade friction was about 75 % effective,
and total drive efficiency over ideal was 55 %
I calculated friction at 0.01 Ca, 2 blades, but actual test prop was a 3 blade.
The motor used less amps and made more thrust on an 8 inch prop of unknown specs.
Computed flow velocity was 21 m/s (about 40 mph).
There doesn't seem to be much room to improve thrust efficiency by adding blades.
was 0.01 Ca a good measure of drag? - a propeller has relatively low profile drag, and higher surface drag.
Is my proportioning of loads and rpm estimate any good? how would errors affect the calculation results?