According to Tim, in his article here... http://www.landships.freeservers.com/Davidson-Cadillac_trigsby.htm ...Davidson built a number of separate and distinct types of machine. The first was based on a Duryea tricar, the second type was based on a Duryea quadricycle, as can be seen in the first five photos in his article.
However, the sixth photo shows a pair of four-wheeled machines, marked No 1 and No 2 (the latter as in the Illinois exhibit), which do not bear much resemblance to either of the Davidson-Duryea vehicles in the first five photos, being of a rather more substantial appearance and having equal-size wheels.
Is this a third type of machine? Or is the lightweight four-wheeler in images four and five in Tim's article merely the tricar with a fourth wheel added (pace Centurion), and the Illinois machine (as seen also in image six of Tim's article) the second type of vehicle? Whichever, the Illinois machine clearly is not the tricar with a fourth wheel added.
Hi the description actually says "three-thirty six inch wheels: one in the front and two in the rear".... this doesnt conform to any of the vechiles mentioned so far.. note the size is quite specific.. also the date used is 1898 not 1902 which would be correct according to Tim Rigsby's article for the later model...... I would suggest that Illinois Uni are somewhat confused about this vehicle... I would also suggest that it is built from components from the first cars there being no suggestion that a new car/s was purchased.... so "no2" stands a good chance of bieng the first purpose built Armoured Car, whereas the previous Tricar, Quadricar designs were commercial cars with a gun added..... Also it may not be a steam car!....
check this link for the only surviving?(not counting Illinois) Duryea
There may also be some confusion about Duryea Automobiles the cars used in the experiments may have been the sole product of Charles Duryea rather then the original cars produced by the Duryea brothers......
Having looked a little longer at the photos it became clear that the wheels on No2 have a different spoke arrangement to the earlier armed cars, the spokes splay outwards from the rim to a wider hub probarbly resulting in wheels capable of taking heavier side loading, the front suspension leaf springs also run fore and aft rather than across the front.....