Thursday, 24 June, 2004
Bicycle power generation
ARRL Field Day is this upcoming weekend from 1:00 PM Central time on Saturday until 1:00 PM Sunday. Ham radio operators all over the country will be out operating from temporary locations, setting up generators, putting up temporary antennas, and trying to contact as many people as they can over that 24 hour period. This is my first Field Day, so I'm not really "up" on all that goes on. It should be interesting.
My contribution to the local club's efforts are twofold. I brewed up a special batch of Field Day Bitter, a low-alcohol beer that should prove refreshing during the heat of the day. Provided we don't indulge too heavily. More importantly, I'll be serving as the power source for our "natural power" rig. The rules say that we get 100 bonus points (Field Day is a contest, by the way) for making a certain number of contacts on natural power. Natural power is defined as power from other than gasoline/diesel generators or commercial power sources. If you use a battery, the battery has to be charged by natural means. Most clubs will throw out a few solar panels to charge a small battery and make their contacts running low power (5 watts or less). We decided to hook a bicycle up to an alternator and a car battery so that we can run for an extended period at 100 watts. My friend and fellow ham Steve Cowell (KI5YG) did the engineering, and I (along with a little help from Debra and Tasha the poodle) pedaled enough power into the battery that we should be able to get our 100 point bonus.
I won't bore you with the math, but charging a 95 amp hour battery takes a lot of pedaling. 8 to 10 hours to get it fully charged. I'm beat.
If you're interested in how Steve hooked it all up, take a look at the alternator wiring close-up (big picture: 1600 x 1200). The light bulb is a dual filament brake light bulb that we used to limit the amount of current the alternator field draws. At full strength the alternator is very difficult to turn and it causes the belt to slip on the bicycle rim. If we do this again next year we'll find a more secure way to attach that belt. More details later.