Antique Tractor Dyno Testing

Dynamometer testing antique tractors July 2023.  Its fun being able to see the old tractors lug down and work while standing still.  And its nice to get a horsepower value to compare to what the tractor left the factory with.
John Deere 70 D
Allis-Chalmers D14
John Deere 60
Massey Ferguson TO-35
John Deere AR
John Deere 430
John Deere G
John Deere R
We are testing at 4900 feet above sea level.  I list the HP corrected for altitude using the approximation that for each 1000 feet in altitude you see a 3% decrease in HP.  So at 4900, we estimate to see a 14.9% loss.