ORIGINAL: ThumbSkull
Nope. Speed is not thrust. Thrust is how many pounds of force trying to move the airframe forward.
Change the diameter and leave the RPM the same you change the thrust.
Change the pitch and keep the RPM the same and the possible speed changes.
Pitch is the number of inches of forward travel per revolution.
An 8 inch pitch will try to move 8'' per revolution.
A 6 inch pitch prop will try to move 6'' per revolution.
So you see, there is much difference in speed potential between an 8'' and a 6'' spinning the same RPM.
When you increase the diameter, the thrust goes up if the RPM and pitch stays the same.
I know speed and thrust are different. In my mind, it would make sense that: if you increase the amount of thrust (which is the amount of force to move forward) you would incidentally increase the speed potential. If a given engine can spin a 6" pitch prop at say 14,000rpm and an 8" pitch prop at 12,000rpm (hypothetical example) It doesnt sound like there would be much of an increase in speed, but if this same engine could spin that same 8" prop at 14,000rpm wouldn't the speed potential be higher?