Passing light

Hey guys, one of the "passing lights" or driving lights or whatever they are called was out on my Ultra. It had 35 W lamps in it, which for some reason seem rather rare around here. I had no trouble finding 55 watt lamps so I got a couple figuring brighter is better........ Put just the one in first to see how much difference there was. Noticed that light felt warm to the touch in just a small amount of time. Didn't think 20 watts would make that much difference but am wondering now if it will be a problem. Don't want to be blowing fuses or something all the time. Should I order some 35 watt instead? I noticed some of the newer ones from H-D are 55 watt. What say you?

It's Volts x Amps = Watts. Or in this situation you can use Watts / Volts = Amps. That doesn't take Resistance into account, but it's close enough. Assuming 12.8 - 13.2 Volts (engine running), going from 35W to 55W bulbs would change the Amp draw from around 2.7 to around 4.2 (per bulb) & an additional 3 Amps or so (total) shouldn't be a problem for your charging system.

The higher wattage bulbs will be hotter though & the additional current will make the wires a bit warmer too, but that shouldn't be an issue. Only time I've seen where it has been is when switching to a 100W headlight bulb on bikes (like Sportsters) that have a lot of wiring in the headlight bucket - it gets "toasty" in there.

did Art just say? :gah:

Big jake, what part of Iowa are in? There is a really hot heritage that I have my eye on down there?

If you have a clamp on ammeter you can see what it is drawing for amps and compare to the manual specs. No hard math involved. The only problem I could see is the heat generated inside the lens, maybe a melting issue?

Your right Chuck. That's something I remember from my electronic days. (first thing you learn, then all the other laws/formulas you never use).
Thanks for the input guys. I was looking through the books and saw that there were several 55W replacement lamps available, so figured it would be OK. It was the heat that got me wondering. I rode it tonight for a bit with one 35, and one 55 bulb, and after awhile, the 35W was pretty much the same temp (to the touch atleast) as the 55.
Guess I'll give it a go.

I'm in extreme NW Iowa. Just damn near South Dakota.

:roflmao: :roflmao: :roflmao: "Watt's Law", derived from Ohm's Law & I remember it only because I need to use it periodically.

Like when I was the manufacturing engineer in a small factory, the 1st problem they gave me was figuring out why 3-phase electric motors were burning out fairly often. Simple - voltmeter showed 198 Volts @ each motor, but the nameplates were all 240 - with not enough voltage, the motors were pulling too many amps & overheating - the total wattage remains the same, but amperage is what does the work & more amps = more heat.

The city had supplied the transformers outside & they were set for 208 Volts, but 2 men in a bucket truck can change the taps to 240 in about an hour & 1/2. I got into an argument with the city engineer about that 'cause he said I'd have to re-wire the whole building - no, you knucklehead, when voltage goes up, amperage goes down & I could actually use smaller wire - the wire gauge is fine, just change the taps on the transformers. He finally relented, they changed the taps & we never had another motor burn out again.

Yep Art, was at work today, doing a metric conversion when the math suddenly woke me up. Watts, not Ohms. Very similar indeed, but yet completely different. Thanks for setting it straight.:gah:

and E=mc2:roflmao:

Easy now, pretty soon somebody will be doing quadratic formulas on us, then we'll all be confused !!

Nope - pie are round