The BSA A7-A10 Forum

Technical (topic titles must be descriptive) => Lucas, Ignition, Charging, Electrical => Topic started by: Beezageezauk on 03.11. 2009 15:31

Title: Self Repairing Lucas Dynamos??
Post by: Beezageezauk on 03.11. 2009 15:31
Ok, so I bought this here non-runner of an A10 that had been stood for 5 years and needed an incentive to get her up and running. *roll*  "I know", says I, "I'll use it for the 2009 BSA International Rally in Southern Netherlands. *sarcastic*

Well, it seemed mechanically sound but had a fair coating of rust on most of the chrome work, so I set to and gave it a good scour with one of those "Brillo Pad" pan scourer thingies and it fair glistened.*smile* After silver painting the rear wheel rim the whole thing looked reasonably tidy so I had a go at getting her up and running. *whistle*

Right, drain the old fuel, clean out the carb, check the contact points and plug!!  Here kick...two...three...four kicks and away she goes... *yeah* hey, what a sweet sounding motor this is! *lol*

Oh! hang aint charging *doh*  *sad* and electrics is my weakest point.  Still, it was light nights so maybe I won't need my lights.  With a fully charged battery it passed it's MOT test of roadworthyness and was made fully road legal. *smile*

At this stage, as time was running out, I decided that it was more important to rig up some sort of carrying equipment and check out the electrics later (if time permits).  Well, I had an old pair of saddle bags stuffed in the shed somewhere and these were dug out, repaired, and eventually fitted with the help of Heath Robinson and his bag of tricks. *roll*

Time was rolling on so I checked the leads from the dynamo.  I remembered that I had to join the two together, start up the engine and check the power output with a multimeter...nothing. *doh*  Out with the books to double check that I have done the right test and sure enough...nothing. *dunno*

Ok, I should only need a horn and stop light so the 6v 12ah battery from my GB31 was fully charged and fitted to the A10.  That should give me more than enough power for my 10 day trip. wink2

Off we go, a nice ride to the overnight ferry and away through the Netherlands the following morning.  I was about 250 road miles (400km) from home and trundling down the motorway when I suddenly noticed that the ammeter was showing a charge. :o  No, it can't be...oh yes it is!! *smile* and the damned thing has been charging ever since.  In excess of 1000miles later and it's still going strong. *smile* *smile*

Now then, hands up all of you who knew that Joe Lucas made a self repairable dynamo. *whistle*  I certainly didn't!!  But maybe someone can suggest why it started to work again??  I'm always willing to learn.

Throughout the whole trip the bike never let me down and apart from a bit of preventative maintenance I never had to open up the tool kit.  So does it pay to take the chance on an unknown machine??  Normally I would say a definite NO but in this case I'm glad I did. *wave*   

Title: Re: Self Repairing Lucas Dynamos??
Post by: groily on 03.11. 2009 17:26
What a great story. You'd think you'd have to pay extra for the self-repairer . . .
Maybe the brushes eventually cut through the muck of ages on the commutator, or you went over a pothole and the cut-out sprang to life, or, or . .
But if it ain't broke . . .
And it doesn't look at all bad for a brillo-pad bike!

Title: Re: Self Repairing Lucas Dynamos??
Post by: alanp on 03.11. 2009 19:36
Funny that, just 2 weeks ago a friend bought a '50s AJS which had been standing around for ever and that didn't charge either. This friend being very knowledgeable, as some are, told me he was going to ride it for a few days and was confident it would come back on charge..which it did! As to why, I don't know for sure but he said that the dynamo brushes would have corroded a little onto the commutator and running it rubbed the corrosion off. Sorry, no minor miracle to email the pope about!
However, it is nice to hear a dynamo coming back to life...standard procedure is for it to die when it's dark, raining and you're far from home...
Title: Re: Self Repairing Lucas Dynamos??
Post by: LJ. on 03.11. 2009 22:00
Reading the story... and a very fine story it is too.... I was thinking... 'It needs flashing' so possibly with the long ride it may have magnetised itself and charging kicked in? In a sort of 'flashing' way??  *dunno*
Title: Re: Self Repairing Lucas Dynamos??
Post by: Beezageezauk on 04.11. 2009 09:49
Hi LJ,

Thanks for your thoughts but I've never been into "Flashing".  Sorry to lower the tone but I enjoy a giggle!! *lol*

Here is another pic taken as I was setting off on that particular jaunt.

Title: Re: Self Repairing Lucas Dynamos??
Post by: Triton Thrasher on 04.11. 2009 10:29
It is quite common for the dynamo to forget its polarity and fail to self-excite.  Also quite common for a few fairly fast miles to sort the problem.

An instant fix (until the next time) is to apply battery live voltage to dynamo F, while revving over 2000rpm.
Title: Re: Self Repairing Lucas Dynamos??
Post by: Beezageezauk on 04.11. 2009 10:33
Thanks for the tip TT.  I've never been able to understand electrics but I sort of get by!!