Identify the Dynamo and Terminals

poor1

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This picture shows an end on view of the dynamo fitted to a Comet looking from from the nearside. The two terminals have been modified to take 6mm threaded bolts. Neither terminal is marked but there appears to be an 'F' scratched on the left hand side of the terminals and 'D' scratched on the right hand side of the terminals.
Two questions:
1. Is this a Lucas or a Miller Dynamo?
2. Can someone identify the terminals for me?

IMG_0757.jpg
 
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greg brillus

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It looks like a Lucas generator..........terminals, F = field and D = dynamo..........Field terminal controls the output, and dynamo is the output. The field one is the one to flash to your battery if you are trying to wake the genny up.........Just swipe the wire across it and it should spark........do this 3 or 4 times and it should work fine. If not then it may be something else like a dirty commutator or the regulator could be faulty.........Good luck with it.
 

poor1

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Any confirmation that this is a Lucas dynamo please and if so which terminal is which because they are not marked.

Many thanks greg brillus
 

Pete Appleton

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I think that whoever did the terminal modification scratched F(ield) and D(ynamo) to identify the terminals.
If you want to make sure you will need to undo that clamp screw in the photo and slide the cover out of the way. The D terminal will be the one that is connected to a brush. It will also give you a chance to see the condition inside the commutator end of the dynamo and give you an idea of whether you are flogging a dead horse.
 

highbury731

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In my experience, it is the D terminal which you flash to. Flashing the F terminal will not do anything useful.
Paul
 

poor1

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That is all very helpful and I am very grateful. I'm now pretty certain it's a Lucas dynamo, although there are no markings to confirm. Someone has previously scratched the F&D on the end cover (twice) and the left one is the 'F' which coincides with 'vibrac'. Unfortunately I was not able to see much by peering into the end of the dynamo after sliding retaining band out of the way with it being mounted on the bike to positively confirm that 'D' is the one connected to a brush.
The dynamo is coupled to a Lucas regulator (type 5169 stamped on the cover) so now that I know its a Lucas dynamo I can use any appropriate Lucas wiring diagram to ensure that the connections are correct
This was all working prior to my rewiring it over a protracted period of time so the dynamo should be ok.
All the electrics are working as they should and showing a negative discharge on the ammeter without the engine running.. My current position is that the engine started at the first kick after having the cylinder head overhauled and the all the electrics are working and showing a discharge at rest but on starting the engine it is not yet showing a positive charge on the ammeter. It would be nice to know whether the dynamo is generating some voltage and I presume that a multi meter across one of the F or D terminal and earth should indicate that there is.. Can anyone confirm that my thinking is correct on this please and which way to connect the multimeter..
 

oexing

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Simple test: Start engine, switch on headlight, rev the engine at half speed and the headlamp must get brighter at higher revs if dynamo is allright. If no change visible no charge.

Vic
 

poor1

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Simple test: Start engine, switch on headlight, rev the engine at half speed and the headlamp must get brighter at higher revs if dynamo is allright. If no change visible no charge.

Vic
Thanks. That assumes that the wiring is correct. What I would like to do initially is to prove that the dynamo is generating some direct current voltage. Then I could confidently find the problem. The polarity of the battery is another unknown factor but I then should be able to flash the dynamo to suit the battery polarity.
 

Chris Launders

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A quick test is to join F and D then couple a 12v headlamp bulb between these and earth, and run the bike, it should light brightly.
But rather than go to a lengthy description about trying and testing a Lucas dynamo and how to get them working correctly have a look at a site called "matchlessclueless". This will tell you everything you need to know and what to do. https://www.google.co.uk/url?sa=t&r...lueless.com/&usg=AOvVaw2XPxrTjMABthi2k-q33l5D
 
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