I have to admit I made a mistake:
Unless you prove the propellers of Whitehead increased their thrust at least 2.37 times at 70 mile/hour as compared to the static thrust your accusations are baseless.
See:
http://www.pprune.org/aviation-histo...ml#post8499180
It is not increased as I wrote but "
decreased their thrust at least 2.37 times at 70 mile/hour".
508pounds * 70miles/hour / 40HP = 237% (if the propellers keep their static trust at 70 mph).
If at 70 mph the thrust decreases from 508 pounds to 214 pounds then the efficiency of the propellers would have been around 100%. As max. efficiencies attained in 1901-1902 were ~ 50% then that static 508 pounds thrust would have had to go down to about 107 pounds at 70 mph.
107pounds * 70miles/hour / 40HP = 50%
Only if the thrust had dropped 4.75 times (508 pounds / 107 pounds) the plane would have attained 70 mph with 50% efficient propellers, available that time.
It appears the propellers of Gustav Whitehead were terrible unoptimized for flight speeds giving high trust at low speeds, where they were not used (the plane accelerated with the propellers unpowered and the engine coupled only to the wheels), and quite poor thrust in flight. It is not impossible. It is plausible.