How about a little mystery this week? What we have here is yet another one of those photos that many have likely seen, but few know much about. It showcases a machine the like of which I have never come across, another one-off racer from the glorious days of the Motordrome. A speed-focused construction from the talented hands of Bill Ottoway, the man responsible for the Harley-Davidson racing program of the mid-teens, this oddball comes from his earlier days spent as the engineer for the Aurora Automatic Machine Company, makers of Thor motorcycles. This unique racer is a direct-drive v-twin, possibly based off their model O with a similarly forward tilting engine arrangement. A shortened frame is bowed out to allow room for the front cylinder, and a keen eye will also spot its longer-than average intake, rigid fork, and odd-shaped fuel tank that is bent down in the rear to allow the rider to have the lowest center of gravity. 
As for the rider, that is New Orleans native Arthur Mitchell who was known to race a number of brands but at the time was mostly riding for Merkel and M&M. However, I believe this photo was taken during races held the first weekend of August, 1911 at Chicago’s Riverview Stadium Motordrome and may offer a bit more information. The races held on August 4th, 5th, and 6th were a flurry of momentous occasions, featuring racing superstars like Charley Balke, Morty Graves, A.G. Chapplle, and Joe Wolters. Aside from this unique and mysterious Thor, Joe Wolters also unveiled a new 7hp Excelsior twin onboard which he dominated most of the heats that he entered. It must also be noted that there is also an extremely rare mention of a Harley-Davidson competing that weekend, raced by a Chicago man named Willie Walsh. Mitchell was racing for M&M and Merkel that summer, and though he took a handful of victories he was most consistently bested by his pal Peter Wenk, who was racing for Thor. Though it is pure speculation, I believe Mitchell is seen here posing atop the machine that gave him the most fight, Wenk’s Thor at the Riverview Stadium Motordrome in early August, 1911.