I have a 50 w Miller Dynamo and points ignition. I recently replaced my standard 45w bulb with a 35/35w halogen headlight unit. Will a halogen bulb overload my Dynamo?
35w Halogen too much?
- Thread starter vintagetour
- Start date
Halogen Watts are no different to Tungsten Watts , it's the total wattage that is relevant. 35 Watt dip or high , + 5 Watt tail + 21 Watt brake light = 61 Watts . Then there is occasional horn use , but of no practical consequence . As long as you don't sit with the brake light on for long periods when the other lights are on it will be fine.
I am a little confused here. 61 Watts plus the Watts necessary for a points ignition to function, is more than the stated output of the 50 watt dynamo.
Depending on the battery reserve, riding too long at night with the lights on seem to look like a long walk home?
What am I missing here?
Ken Smith
(electrically challenged)
Indeed you are missing nothing. The British motorcycle electrical system of that period does sail that close to the wind and is why there is such paranoia about riding a standard , originally equipped Vincent at slow speed at night ! With the system in good condition the headlight and tail light load are no problem , the brake light is only used intermittently so will not normally cause a problem. Points ignition takes about 10 watts or so AVERAGE , and I think the coil ignition machines had a 60 watt Dynamo to cope with this extra load. These days of course no self respecting vehicle electrical designer would even contemplate installing a system running close to 100% capacity at night !!
I have come to accept the fact that my lighting is marginal at best. Any danger from the heat from a halogen bulb. Specs say 500 degree F (probably for a 12v)?
I have never known the heat from a halogen lamp to cause a problem , particularly with real metal reflectors and real glass lenses. One way to ensure that the most lumens possible are extracted from the light is to ensure good earthing from the headlamp unit to the frame. Don't rely on the metal to metal contact through the headstock , install an actual earth wire.
When people fit our 360 watt alternator kit to twins I recommend that they fit a 130/90 quartz halogen bulb. One has to ensure that the dip switch and wiring are up to it but there have never been any problems with either the reflectors, glass headlight covers etc. 35 watts is not going to cause trouble but note Tnecniv's comments about the earth. I would always suggest a decent new wire from the battery negative to the headlamp shell. 
Howdy Sir,
Couple of things. Whose point ignition/coil sizes, etc? Small m/c oriented ignitions are very forgiving, stock Indian ignitions will function down to 5.5V albeit on low compression motors which don't squelch the spark. How are you regulating that Miller, mechanically or electronically? 2 charge mechanical reg's can draw over 2amps as they age and the points begin to crust over which in turn contributes to more heat in the genie and less output. Disregarding the vagaries of an ammeter, with a healthy battery (8-10 amps), any fluctuation in brightness of your headlight corresponding to a given rpm change is an indication your running parasitic or at threshold.
Effective grounding already mentioned and automatically addressed if you have Coventry type harness which dedicates a headlight ground wire to the aft fixing point on the UFM which in turn takes the battery ground.
A healthy 6V Miller converted to an electronic regulator like a PODtronic with an LED tailight will easily run a 35W halogen in urban/city settings, though I'll readily admit up front to less burden on my setup by virtue of a BTH. It zeroes this load at only 35mph very overgeared on a 46 tooth and 19inch driven wheel.
Couple of things. Whose point ignition/coil sizes, etc? Small m/c oriented ignitions are very forgiving, stock Indian ignitions will function down to 5.5V albeit on low compression motors which don't squelch the spark. How are you regulating that Miller, mechanically or electronically? 2 charge mechanical reg's can draw over 2amps as they age and the points begin to crust over which in turn contributes to more heat in the genie and less output. Disregarding the vagaries of an ammeter, with a healthy battery (8-10 amps), any fluctuation in brightness of your headlight corresponding to a given rpm change is an indication your running parasitic or at threshold.
Effective grounding already mentioned and automatically addressed if you have Coventry type harness which dedicates a headlight ground wire to the aft fixing point on the UFM which in turn takes the battery ground.
A healthy 6V Miller converted to an electronic regulator like a PODtronic with an LED tailight will easily run a 35W halogen in urban/city settings, though I'll readily admit up front to less burden on my setup by virtue of a BTH. It zeroes this load at only 35mph very overgeared on a 46 tooth and 19inch driven wheel.
Interesting that Bruce Metcalf's headlamp got hot. Mine is a chromed 7" unit (yes I know!!) and it does not get hot when riding at night which is the only time I use a headlight. Perhaps those who live where it is obligatory or who choose to ride in daylight with their headlamp on and who live where the ambient temperature is in the 20s C not the 10s or less could let us have their experience. Perhaps we need to be aware that we are global users and conditions vary. Feedback chaps?