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+--- Thread: Dynamo Field Resistor (/showthread.php?tid=2499)
RE: Dynamo Field Resistor - David Stepney - 11-03-2019
Before the field brush decided to shed its wire ( after I had washed it on Sunday and started it to put it to bed!), the dynamo charged at an indicated 10 amps, which was just enough to support the sidelamps and dipped beam ( I am on single dipping headlamps), so I think I shall leave the third brush alone. If I make up a long enough resistor coil, I can presumably find the optimum position on it to give me a suitably reduced charging rate and then trim it to length.
RE: Dynamo Field Resistor - Reckless Rat - 11-03-2019
David, 10amps is pushing it a bit. The harder the dynamo has to work the hotter it gets and asking too much from it can melt the commutator. Personally I would back it off, even if there is a discharge when you've got everything on. Try resetting the 3rd brush to tone down full output. With a fully charged 80Ah battery you could run lights on for 10 hours (theoretically) without anything going back in, so a slight discharge is OK. Changing to LEDs will further reduce the demand on the dynamo and allow you to back it off even further.
For your resistance wire it will be a matter of trial and error to find the length that reduces the summer setting to about 1amp, running. Once you've got the right length you can coil it up and just let it sit between the D & F connectors on the dyno.
You could remove the dust cover for a bit of extra cooling too.
RE: Dynamo Field Resistor - David Stepney - 11-03-2019
Hmmm. LEDs. I wonder if that would also give me better headlamps? the standard 36 watt bulbs are dimmer than the proverbial Toc H lamp.
I didn't know one could get them in 6 volt. If one can, where from?
RE: Dynamo Field Resistor - Stuart Giles - 11-03-2019
(11-03-2019, 10:04 PM)David Stepney Wrote: Hmmm. LEDs. I wonder if that would also give me better headlamps? the standard 36 watt bulbs are dimmer than the proverbial Toc H lamp.
I didn't know one could get them in 6 volt. If one can, where from?
This bloke does LED bulbs in 6 and 12V-usual disclaimer.
http://www.norbsa02.freeuk.com/
RE: Dynamo Field Resistor - David Stepney - 11-03-2019
Thank you Stuart. Looks to be quite reasonably priced too.
RE: Dynamo Field Resistor - Bob Culver - 11-03-2019
The original lamps were only 18w. If the system voltage is dragged down by very heavy load, larger wattage lamps often acheive no more light.
RE: Dynamo Field Resistor - Dave Mann - 12-03-2019
DSCF7123.JPG (Size: 215.5 KB / Downloads: 181)
I thought they were 15W Bob
RE: Dynamo Field Resistor - Bill Dixon - 12-03-2019
David,
As RR says 10amps is a bit high adjust 3rd brush to 7or8amps.High power aluminum clad resistors can be found on ebay a value of 4R7 should be about right these are rated at 50watt.These can be bolted onto the bulk head to reduce the heat of the resistor,this is better than trying to wind your own resistor. Hope this helps.
RE: Dynamo Field Resistor - David Stepney - 12-03-2019
I have a double filament 36w/36w bulb in the nearside headlamp and a single filament 36w bulb in the offside. They are grim enough. i can't imagine what the lights would be like on less than half the power!
Thank you Bill, I shall have a look!
RE: Dynamo Field Resistor - Dave Mann - 12-03-2019
Blimey I run 25/25w quartz halogen and find they are like searchlights, so much so that I get some moderns flashing me if they get knocked out of alignment.