Dynamometer, affordable

[Eric Elliott]

Hello,
The local aircraft rebuilder thinks a used aircraft propeller could be 
an excellent power waster. He said:
Perfectly good propellers, propeller shafts, crankshafts and other 
parts are discarded due to age, hours of use or minor cosmetic damages. 
Propellers can be fixed pitch (load a function of RPM and flow 
restriction) or variable pitch. Pitch controls can be electric, 
mechanical, hydraulic or combination of mech. input ring and internal 
hydraulics. Props range from 25 to 1500 HP at limits of 1500 to 3100 
RPM. The RPM limit is due to efficiency loss as tip velocity exceeds 
speed of sound. Beyond the speed of sound the prop might break or just 
be a power (dynamometer) waster. 
Clubs are like propellers, but intended for engine testing on ground. 
Clubs can be inexpensively made for custom purposes.
An engine case and out of hours crankshaft could supply pitch controls 
and mounting for a variable pitch prop.
A fixed pitch prop on a pallet size mount with a manual transmission, 
thrust bearing and prop guard/thrust diffuser could be shipped from 
user to user. Gear ratios could help match loads to needs. The diffuser 
could keep it from “leaving”. Headline: Leafblower From Hell deafens 2, 
cleans 3 yards!
A prop on a rear axle could be cheap and avoid the 3100 RPM limit via 
hypoid gear ratio. The differential could be locked for <$5, via 
addition of 2 spider gears. A thrust bearing might not be needed as 
ring gear axial thrust might exceed prop thrust.
Some calculation of (effect of) thrust to be generated would be in 
order. Also consider tendency of prop to "process" people.

Eric Elliott