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Weak Miller bicycle dynamo on 1940 Raleigh
#1
[attachment=1930][attachment=1929][attachment=1928][attachment=1927][attachment=1926][attachment=1931]
Hello riders

Here are some attachments.I have recently restored this Raleigh 1940.
This bicycle generator ia a miller 6V,3.24W lighting. I have to spin too hard to start bulb glowing. If bulb inside is 3W what else can cause this dynamo to get weaker. The wire that runs from wheel to light is new multi stranded copper wire.
Hello old bikers!!! Can this kind of dynamo be stripped down for a service. Any tips on dismantling this one.......Please help!!
Cyclostyle in style
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#2
What a nice looking bike.

Possibly bad contacts; To check if poor contacts is the cause, use a spare bulb and 2 wires, one from the contact at the bottom and one from the bracket of the dynamo, if bulb glows brighter when you spin the wheel, this is the likely cause.

There is a pointed screw on the back of the dynamo attachment bracket which is intended to drive through the paint and make good contact with the metal of the frame, make sure this is done, also make sure you have clean metal to metal contact at both the light brackets, as for instance, the contact on the bottom of the dynamo looks as though it could be cleaner, vaseline can be applied at contact points.

These dynamo bottles can still be obtained here in the UK, but they are now made in India
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#3
(02-18-2011, 01:04 PM)trevgbb Wrote:  What a nice looking bike.

Possibly bad contacts; To check if poor contacts is the cause, use a spare bulb and 2 wires, one from the contact at the bottom and one from the bracket of the dynamo, if bulb glows brighter when you spin the wheel, this is the likely cause.

There is a pointed screw on the back of the dynamo attachment bracket which is intended to drive through the paint and make good contact with the metal of the frame, make sure this is done, also make sure you have clean metal to metal contact at both the light brackets, as for instance, the contact on the bottom of the dynamo looks as though it could be cleaner, vaseline can be applied at contact points.

These dynamo bottles can still be obtained here in the UK, but they are now made in India
trevgbb
I did all the checks & could have no improvement in lighting. Any website where I can check out technical data or will show how to tear it apart for service?
Cyclostyle in style
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#4
Nice Restoration.

10-4 to what trevgbb said. Not sure if its negative body or positive body connections. Some vintage English vehicles used the body as the + , reverse from current practice of the body being -.

You could run a continuity test from the dynamo body connection at the bike to the headlight connection to see if you get full power.If you did the light test at the connections and there was no improvement that continuity test is superfluous. Do clean the bottom connection till shiny and use die electric silicone grease (not Vaseline) , a favorite of owners of old British vehicles. Esp. with Lucas the prince of darkness electrics.:-))

IMO the magnets are demagnetized or loose and a new dynamo it the most effective option. Cannot quite tell from photos, but it looks like the bottom has a notch in it for a hook wrench. So it may unscrew. You may be able to replace the guts from a new one.

lots on UK ebay.

http://cgi.ebay.co.uk/MILLER-VINTAGE-BICYCLE-DYNAMO-AND-FIXING-BRACKET-/180623268462
Never Give Up!!!
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#5
Given what you have done, I also agree that most likely the magnets are demagnetized. If so, you have some choices:
* re-magnetize the existing magnets - great for historical accuracy.
* change to a modern magnet materials. In the '70s and '80's magnet materials took a quantum leap forward. If you elect to go this route, I suggest Barium Ferrite or Strontium Ferrite Magnets. Here is one source; I have never done any business with them: http://www.magnetsales.com/Ferrite/FERRI.htm

I would NOT use neodymium magnets in your dynamo. They will cause problems because of their very high magnetic strength.
Nigel
  Reply
#6
Make shure you have a 6 volt bulb in there and not a 12 volt bulb.
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