Darryl.Richman's picture

The 50th entrant was added to the Cannonball roster today. Looks like there will only be the two BMWs, my '28 R52 and Jack Wells' '29 R11 (#23 ridden by Norm Nelson).

It has been pointed out that about 50% of the entrants are riding Harleys, with a majority of them on JD models. The JD was introduced in 1921 and was built through 1929. It was a development from the J model, introduced in 1915, and in the 2010 Cannonball, the 1915 Harley J models won most of the perfect scores.

The JD sidevalve engine displaces 1200cc/74 cu.in. (nominal) and has battery/coil ignition. It has a bore of 3 7/16" (about 87mm) and stroke of 4" (102mm) with a compression ratio of 3.8:1, delivering about 22hp @ 3200rpm. The combustion chamber, as with all of the sidevalves of the era, has an interesting shape due to it's "inlet over exhaust" construction. The iron cylinders were cast with integral heads.

The JD included a 3 speed hand shift transmission and a rear brake; a front brake was added in 1928. Dry weight was just over 400 lbs., and the gas tank holds 4¾ gallons. Electric lights were standard on the later models, like many of the entrants.

Although BMW has long had a reputation of being under stressed and conservative in their design, when you compare the Harley JD engine to BMW's offerings, you can see that BMW was produced a more tightly wound machine. The JD engine produces 18⅓ hp/liter, but the R52's 500ccs makes 24 hp/liter. This same ratio holds for BMW's bigger 750cc offerings in the R62 and R11 models (like Norm will be riding). Let's hope that the BMW design is conservative enough to make it nearly 4,000 miles across the US!


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