Author Topic: What revs does a 6Volt Dynamo light the bulb  (Read 254 times)

Offline barry2

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What revs does a 6Volt Dynamo light the bulb
« on: 12.06. 2019 09:38 »
Hi mates
Got my 6v dynamo on a test bench, D & F  joined it takes over 3500 revs  to light a 6 volt globe (speed  of the unit not engine ) seems a bit high to me, was working on bike normal , then stopped, that why it was tested what do think?
all the best
Barry
WA

Online groily

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Re: What revs does a 6Volt Dynamo light the bulb
« Reply #1 on: 12.06. 2019 14:58 »
That's a lot of revs BUT 6v filaments can take a bit of lighting up if hooked up directly, esp if using a h/lamp bulb of some power.
If you preheat the bulb off a battery and then hook it on when warm it will tell you a bit more. I would expect to see light coming on under 2000rpm and brightening with more revs until it could well blow - but  I would  get a meter across d & f to Earth first to see that you are getting a steady increase in volts, no load on, from around 1000rpm, building to maybe 20v with a burst of speed. Then hook loads on to see if it supports eg 45 watts and still is showing over 7v on the meter around the 2000 mark. 12v bulbs are easier for this, and less likely to blow due to lack of regulation while doing crude checks.
Better still, get a battery and working regulator hooked on and measure the voltage from A on reg, or across battery, with loads switched on. If the dynamo and reg are any good the system should show a steady 7+ a bit voltage at medium revs with all loads switched on. The system, on the bike, should be regulating steadily by about 2000 engine, maybe 2500 dynamo, with steady lights and steadyish battery voltage depending on vagaries of meter being used. You would also be able to observe the cutout working, especially if you DISconnect the battery while measuring voltage coming out of A.
Bill

Offline trevinoz

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Re: What revs does a 6Volt Dynamo light the bulb
« Reply #2 on: 12.06. 2019 23:02 »
Try it with a voltmeter. At around 2500 revs you should be getting 14V or more. Don't run it like this for too long.

Offline KiwiGF

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Re: What revs does a 6Volt Dynamo light the bulb
« Reply #3 on: 14.06. 2019 07:10 »
Hi mates
Got my 6v dynamo on a test bench, D & F  joined it takes over 3500 revs  to light a 6 volt globe (speed  of the unit not engine ) seems a bit high to me, was working on bike normal , then stopped, that why it was tested what do think?
all the best
Barry

Have you got an ohmmeter to measure resistance? If so the field resistance should be over 2 ohms, preferably nearer 3 ohms (from memory). Also check if the field coil is shorting to the body, that’s a common issue.
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Offline trevinoz

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Re: What revs does a 6Volt Dynamo light the bulb
« Reply #4 on: 15.06. 2019 00:19 »
The most common fault is in the armature.

Offline barry2

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Re: What revs does a 6Volt Dynamo light the bulb
« Reply #5 on: 18.06. 2019 00:16 »
Hi Mates
Got it working,, thanks for all the tips, It was the base plate of the regulator it had shaken loose from  the regulator frame ,, the two screws underneath had come loose ,,, were they ever rubber mounted? I think some of the car ones of the same period were

Barry
WA