Tuesday, February 1, 2011

Key engineering advance #4: Overhead valves & four-valve heads

Board track racers hit 100+ wearing leather helmets and wool jerseys. In crashes, they were sometimes killed by splinters.
Hedstrom wasn’t finished incorporating some very creative innovations into Indians. (I mean, Indian 'motocycles'. He wasn't another white guy introducing innovations like reservations, alcohol, and smallpox-tainted blankets to the actual Indian people.) 

Board track racing was very popular and an important way for Indian to promote sales. In order to make a more powerful motor, Hedstrom knew he needed to incorporate overhead valves. The problem was they were more prone to breakage, causing catastrophic engine damage. As early as 1911 he solved this problem by using four valves per cylinder instead of two, thus making each valve lighter and easier to open and close. The result was a motor capable of propelling the flimsy board track racers of the day, which were unencumbered by brakes of any kind, to nearly 120 miles an hour!

1 comment:

  1. Hello, and sorry for the unsolicited approach - can't reach you via your website etc

    I'm researching the prototype MV Grand Prix racers for my Italian bike fanzine, benzina (and will gladly send you a copy), and wonder if you can help. There's a little info on the sixes (notably John Surtees magazine test from 1982) but I'm struggling with the Boxer. I found a cached webpage by yourself that implied Team Obsolete have what was left of the bike, but would love to learn more

    Best wishes

    Greg (also occasional contributor to Classic Bike and fan of your writing)

    www.teambenzina.co.uk

    ReplyDelete