Dodgy battery (or not?)

[Sav]

One good thing is it speaks volumes for the little steady voltage five volt output, regardless of input, gizmo I use to run my satnav on lucas 'six' volts variable (and probably highly variable in this case  ).

Guess I'd better drown my sorrows this evening! Have a good New Year all!

Sav (Chris)

[fido]

I don't understand why the A7 needs a different battery to the A10. The 2 models were originally identical in terms of electrical equipment.

[Sav]

I don't understand why the A7 needs a different battery to the A10. The 2 models were originally identical in terms of electrical equipment.

Battery cages are different on the two bikes but may well not be original after fifty years, The A10SR has the full width, height and depth cage for the B38 battery and the A7SS has the full width, height but only half depth cage for the B39 sliimmer battery. The A7SS also still has the old mechanical regulator

Sav

[trevinoz]

Sav,
          How many miles have you done since the dynamo overhaul?
That bearing certainly doesn't look like a 3 1/2 year old item!
Have you done a lot of wet weather riding? The bearing appears to be rusty and seems to be skewed in the housing or is that a lighting trick?
From experience, I would say that the armature has been "poling", due to the collapsed bearing, creating a lot of heat and probably causing the solder on the commutator to throw.
With a bit of luck the armature won't be burnt out but will need to be resoldered. Ensure that all wire ends are clean and not burnt and maybe you will be OK.
Make sure that the comm end bearing is a good fit in the housing and check the armature shaft for straightness, quite often they have a slight bend which can be rectified.

Trev.

[trevinoz]

Another couple of points, you should have an "O" ring sealing the perimeter of the metal cap and a rubber grommet to seal the wire entry.

Trev.

[Sav]

Thanks Trev,

The A10SR has been a labour of love!!

It got off to a bad start when a ratchet strap failed on the way home from purchase and the front end got dragged along the road.

The bike was bought having been rebuilt, but it was a kitchen rebuild and fell apart immediately. My mechanical experience at the time was negligible so I had new ends and shells fitted but they turned out to be some of the sub standard 'Italian' ones that were about four years ago and did not even survive a gentle running in.

So I gave the engine to the experts at SRM and said do the lot and fix it! £3.8k, roller bearing conversion and a complete rebuild of engine and electricals later the engine has been brilliant. The only minor problems were the dynamo brushes initially and later a crappy set of points SRM installed where the main spring was too tight so that the mounting pole came loose. After 'discussions' about lack of info on a known possible failure of these points they refunded the cost of the points.

Thus everything is as rebuilt. the grommet is on place but I am not aware of a O ring for the cap edge. The bike has done 9k in all weathers since the rebuild, many long runs and rallies including hundreds of miles all over the Pyrennees, Manx GP's and Colombres rallies in Spain. It pulls like a train and sounds gorgeous as there is nothing up the silencers.

The dynamo bearing looks bone dry as far as lubrication is concerned and I must admit the cover has not been off in three years, though I would not have seen much with the covering bearing plate (or are they sealed?). The bearing shells have thus given way

So I'll give the dynamo to the experts and try to make sure it is done properly as that's the bike I use and rely upon.

Sav.

[beezermacc]

I have repaired a few armatures the way Trevinoz suggests, particularly when replacement armatures have been unavailable. I'm not taking issue with Trev's advice - this is a perfectly good repair for those who like a challenge and don't have to guarantee the longevity of the armature. The armature in Sav's bike has had quite a battering so I would be reluctant to refit this. I've come across quite few dynamos which have been completely wrecked due to the commutator segments coming loose from the armature, bashing against the brushes, smashing the brush holders and bearing carrier, and snapping the dynamo chain! (Ouch!). The vibration and the battering the commutator has suffered may have weakened the bond between the commutator segments and the armature. Fortunately new armatures are readily available and the ones supplied by the UK manufacturer are of a very high quality and capable of driving a 12v. system. I agree with Trevinoz, the bearing has a somewhat 'antique' appearance! Most restorers have been using sealed bearings for a number of years so I'm surprised Sav's isn't of that type. Happy New Year!

[Sav]

Looking at the SRM bill it would appear that the bearing was not changed. The mag rewind and rebuild cost £230 plus vat. The dynamo just has check and rebuild £35 (plus brushes and nickel plating). It would thus appear that nothing else was changed. That surprises me with the great lengths to which they went to replace everything in sight on the mechanical side and make sure everything else was absolutely A1.

Sav

[beezermacc]

The mag rewind and rebuild cost £230 plus vat.

... which included gold plating of course! Maybe the owner was starting to run out of cash. As can be seen, false economy not to have things done properly!

[Sav]

The mag rewind and rebuild cost £230 plus vat.

... which included gold plating of course! Maybe the owner was starting to run out of cash. As can be seen, false economy not to have things done properly!

Certainly seems a false economy when I paid £3.8k plus delivery and collection for the rest of the rebuild! The rest of the rebuild has been absolutely first rate, but they had the dynamo back immediately as it was not charging due to sticky brushes. Thus they got to look at that bit of kit twice.

Sav

[beezermacc]

Hi Sav, OOps! Sorry, I forgot you had the SRM job done; I was thinking that it had been done by the previous owner for a (senile!) moment. All the magnetos and dynamos going through my workshop get new armatures unless they have been exchanged recently and the reason for rebuild is apparent elsewhere. A friend of mine has two BSA's with SRM engines and they both run faultlessly. You can sometimes tell when the commutator is about to burst as the segments start to twist very slightly so they are not guite parallel to the central axis of the armature. This is a sure sign that the bond between the commutator and the armature is failing.

[trevinoz]

Sav,
          The "O" ring sits in a recess in the end plate below the brush plate, if you have the correct end plate.
Trev.

[Sav]

Cheers Trev,

All dismantled and ready to go in the post tomorrow.

I can see the groove under where the cap slides on but no O ring in there.

Sav.

[Sav]

Thanks to beezermacc for giving my dynamo and DVR2 the once over.

Took the opportunity to do a Hawker belt conversion at the same time.

Put it all back together again and tried the electrics out in stages and could find absolutely nothing. Bikes had a run now with everything connected and appears to be workmg perfectly.

Looks now like I was dealing with two completely unrelated faults and the dynamo bearing going at the most awkward time as I know it was charging when the battery fault first appeared.

Good quality Yuasha battery in situ now.

Thanks to all for suggestions given.

Chris.