But it's not Ohm's law. The resistance (or impedance) increases as the filament heats up. The resistance of a 12V bulb measured with a multimeter will be much lower than with 12V across it.

Good morning Jon. This is a modification that I have attempted but not entirely successfully. I understand that legislation requires a 21watt indicator bulb which applying the necessary maths: P (watts) = I (amps) x V (volts) would give a current consumption of 3.5 amps at 6 volts which given the Austin's dynamo output is a little high. The problem that I found was sourcing a 21watt amber capless bulb to fit into the Seven Workshops reflector so what I ended up doing was to buy a larger bulb and bulb holder and fit that.
My preferred solution is to use reflectors with built in sidelights and to use the Lucas LD 109 sidelight as the indicator using LEDs sourced from 'Classic Dynamo and Regulator Conversions' although this modification in itself is not straight forward.
Regards
Stuart

Location: Staffordshire, the creative county

Location: Nr Penzance

Good afternoon Jon. Further to my earlier post I understand that the reflectors will be available again from the Seven Workshop in the late spring/early summer.
Regards
Stuart

Location: Staffordshire: the creative county.

good to know. That means others wlll come up to the same issues as we are pondering!

My visual prompt is that with the 65, I want to respect the simplicity of an absence of wing mounted side lights, and not clutter it up with those podded indicator things. Thus I'd wondered whether the side lights could BE a duplicate of dipped lights, in theory, to clump everything into the single unit.

Stuart - how did you fashion the fitment of larger bulbholder into the pilot - just with some heat silicone around the outer of the reflector unit?

Hello Jon. The capless bulbs that I bought fitted the '7 Workshop' sidelight bulb holder although the 'bulb' was much larger. However I have unsuccessfully tried to find an alternative supplier as the motor-cycle spares company that I used have ceased trading.
Regards
Stuart

Location: Staffordshire, the creative county

presuming that you are using 12V (?) these seem a good idea for keeping the amber smudge out of the headlight when not wanted... but I suppose the wiring for the pushfit holder need uprating.

http://www.hids-direct.co.uk/xtec-585-wy21w-chrome-amber-indicator-capless-wedge-bulbs/?gclid=CPagiqqGicwCFQPgGwodb8QDEA

As you say, I need to go LED, or 12V, to solve the problem.

I would expect that an indicator fitted inside a headlight reflector would be completely invisible when the headlight is on. I find them difficult see on modern vehicles when they are fitted close to the headlight unit.

Location: Melrose, Scottish Borders