On Apr 20, 2013, at 5:56 PM, Baldur Gislason <baldur@foo.is> wrote:
On the latest post about listening for deto, I figured I’d chime in.
10 years ago I started listening for detonation on car engines using a pair of Peltor ear muffs that I drilled and epoxied hose
barbs into. Both sides are teed together and connected to a piece of copper pipe at the engine by an 8mm rubber fuel hose.
Later, when presented with the necessity of listening for detonation on both my turbocharged snowmobile and a turbocharged
single seater formula off road buggy we built, both applications that require a helmet, a modified approach was required.
For field testing with a helmet on I use the setup pictured here: http://www.foo.is/gallery/misc/IMG_7000
It is a pair of ham radio ear pieces that have a tube connection between the earpiece and the speaker. I picked those up on ebay for about $10 each.
In my application, they’re clipped onto a piece of plastic (POM) shaft that I center drilled and machined the ends on the lathe
to let the earpieces clip on. The plastic shaft attaches to the helmet by electrical tape and is connected to a copper pipe
at the engine by a length of rubber fuel hose. It works if anything, better than the ear muffs.
Baldur Gislason