Circuit diagrams

[ian Howell]

Bore da: -

Ensconced in Wales now!

Bob: - Do you take The Automobile? In the October issue on page 80 there is a picture of a 1929 6.5 litre Bentley registration number PG 5766. One more to add to the collection!

No more progress on the electrics though! I wonder if there might a 'short' circuit from a lead-in wire to the body of the dynamo?

That could easily have happened if a wire with fragile insulation was knocked. I am at present guessing that the two wires are: 1 from the field winding and 1 from the armature. The other ends of both would be connected to the body of the dynamo.

We shall see . . .

[robert lintott]

Ian, yes I do, and I did . Rather exotic company we keep! bore da Bob

[ian Howell]

Bob, Tony, George, Keith et al: -

Keith said "Well I cannot make head nor tail of that diagram! The ignition switch needs a lot of explanation and the wires into the dynamo are ambiguous as to where they go. Give me a clue....."

Well, I'VE CRACKED IT! (I think).

Like Keith I could not make head or tail of the diagram so I set to and re-drew it on the PC using colours to help me trace the conductors. So far so good, but I still could not work out the logic of the charging circuit or the meaning - let alone purpose - of the two dashed line conductors from 'F' and 'D+'.

So I took the panel out of the dashboard - BRAVELY disconnecting all the wires - and went over the panel with an ohmmeter (continuity tester). This has clarified the function of the dashed lines - they are switches that operate together with those for ignition and for lights. The sequencing is interesting and clever, but this will be clearer when I have completed my drawing.

BUT - and here is the 'cracked it' bit - I also discovered that a solid brass strip connecting the 'D+' terminal to an intermediate connection on the switch moulding had a hairline crack in it. I had EXACTLY this problem 49 years ago with my Bradford, when a similar crack stopped the regulator working during a night run from the South Coast to Liverpool.

I will try to get a decent photograph of the problem, but I bet I am not the first to find this type of problem in a vintage switch panel?

As with the Bradford regulator, I will solder a copper link across the crack and then I am sure (hope?) that the charging problem will be resolved. I have still to sort out the dynamo connections but that surely cannot be difficult?!

When I have completed the circuit diagram I will put it in the gallery for the 'benefit' of any other benighted souls who may appreciate a clearer version than that provided by contemporary sources.

Next task is to put the switch panel back in the dashboard and re-connect all the wires (and of course the speedometer cable and oil pressure guage feed pipe).

Then we shall see if all is well.

Watch this space . . .

[ian Howell]

Yup! Cracked it!

Well, I had to make a complete new brass link as the original had ANOTHER crack in it when I took the switch panel apart.

Tonight I put it all back together, set up a voltmeter on the dynamo 'POS' terminal (and 'earth' of course) and fired her up.

NOWT! Well very little anyway, but then I recalled my college days and the need to energise a new dynamo. Well OK it's not new but it seemed to have forgotten that it is a dynamo, so when I put a positive feed to the field coil - RESULT!

Only about 6 amps charge in the 'Summer' position though. Perhaps this will be better at road speeds.

Looking at the dynamo there doesn't seem to be any way of moving the 'field' brush to give a different output. All the brush boxes are rivetted to the dynamo end cover. Does this possibly mean it is an older type dynamo? Only TWO wires out to the terminal block remember.

[Tony Fearn]

Looking at the dynamo there doesn't seem to be any way of moving the 'field' brush to give a different output. All the brush boxes are rivetted to the dynamo end cover. Does this possibly mean it is an older type dynamo? Only TWO wires out to the terminal block remember.

Ian, I've just been over to the garage to take a few pics of a three brush dynamo with two wires coming out of the hole at the top. The screw on the backplate, and the bit it attaches to on the inside have been coated with white tippex. When the screw is loosened, there's a little quadrant machined out of the plate on the inside which allows a degree of rotation. Moving the plate, which carries the thin third brush, alters the charge rate as previously discussed.

Dynamo for Ian H.JPG

Dynamo for Ian H1.JPG

Dynamo for Ian H2.JPG

Tony.

[ian Howell]

Tony: -

Many thanks for the photos. I may not get to that problem for a while following 'engine trials' this afternoon!

I put the car up on axle stands all round, anti freeze in the rad and started up - Still charging OK!, BUT . . .

With the wheels going round I thought I might as well 'nip up' the back brakes to bed-in the brake linings that I made AGES ago. So well and good, but sitting in the car I noticed that the speedo was not registering. (Brand new speedo from Beaulieu a couple of years back).

I had made up the speedo cable from an ex-Javelin item I had laying about, with a new inner core (I have a limited stock from when I worked for a firm that made flexible drives and such) and fittings to suit the speedo and the Humphrey Sandburg unit.

What I hadn't allowed for was the depth of the fitting at the freewheel end, and the core therefore runs away from the speedo drive fitting. Not really a problem, I just need to make new - correct - fittings for both ends and cut and solder a replacement inner core, so it's lathe time again and I think the dynamo can wait a bit. After all, it works now!

[ian Howell]

Speedo cable now sorted, but the dynamo . . ?

Tony's photos are great but there is a problem - there is NO screw in my dynamo there, just a hole. By feeling around with bits of wire etc. I can feel a screw thread inside so I may yet be able to recover the situation.

HOWEVER (have you noticed, there is always a BUT or a HOWEVER), a rummage through my sizeable box of screws has not turned up anything that fits!

It seems to be too small for a 1/4" BSF or a 0BA, not the right thread for a 1BA (I have a full set of BA taps - no screws of course) and 2BA just rattles through.

My plan now seems to be to remove the dynamo and 'bench' it, but that appears to mean removing the timing cover to get to the dynamo sprocket. That means removing the inlet/water manifold, that may mean removing the radiator and that means removing the bonnet.

There may be a solution. There is a brass plug in the timing cover where you can check the chain tension. Does anyone know if it is possible, after moving the dynamo to give maximum slack in the chain, to poke something through that hole to slip the chain off the dynamo sprocket whilst carefully backing the dynamo out, and - more importantly - slip it back on again without all the above hassle? Obviously the timing would need to be reset, but that is not really a problem.

Alternatively, I plan to try to remove the distributor, ignition coil, cut-out, dynamo fixing bolts/studs, and then rotating the dynamo in-situ to give access - and possibly enlightenment - to the third brush box and adjusting quadrant. I am assuming that the thread I can feel IS the third brush locking device but I suppost that could also be missing.

AH! A sudden thought. Is the thread possibly LEFT-HANDED? (Why for Pete's sake?).

[robert lintott]

Ian, out of curiosity I started up my 1930 Austin 16 yesterday . It has an ignition switch with Summer and Winter positions .I think the 3rd brush is not adjustable . At an rpm which I would think is a good road speed---ca 40 mph-- it registered 7 amps on the Summer setting and 12 amps on the Winter setting . Your 6 amps might well be OK for the Summer reading . The Austin is a 12volt system , I use a single battery rather than the original two 6 volts ( and was told off by the purists for doing so!) which is quite old so a new battery might produce a higher charge. All told with the simple and limited electrical loads of those days your 6 amps may well be OK. ? If not perhaps use the winter setting all the time ? Good luck Bob

[ian Howell]

Robert et al: -

All 'On hold' until I get back from Wales early next year.

There DOES appear to be a third brush, it can be adjusted by easing a screw on the dynamo end plate and then sliding the third brush a limited amount along a circular quadrant track (then retightening the clamp screw of course).

It is rather annoying after 8 years of repairing the car, to have these niggling problems just when it isready for 'trial runs'.

[ian Howell]

TA RAAA!

On return from our first visit to Wales this year (we are now back there again!), I managed to get the dynamo off without removing the timing cover. On the bench I found that the second fixing screw and captive nut were missing and that the third brush was in a pretty poor state and was only j-u-s-t touching the commutator when it felt like it. The main brushes were OK.

I found an exact match for the screw in my 'odds and ends' box and made a replacement captive nut to the pattern of the other one. Refitted both adjuster screws and the third brush carrier is now secure but moveable when/if required.

So far, so good. Now about spare brushes.

Well of course I hadn't got spares so I set about thinking. No spare dynamos of any sort in the spares bins, BUT my son did have a scrap alternator. Hmmm . . . .

There are TWO brushes in an alternator and these two were exactly the right thickness, but only half the width. 1/2 x 2 = 1 Jackpot!

Well nearly. There is a sort of 'bulge' in the brush holder which stops a full-width brush being fitted (I now understand your 'thin' brush' Tony). The field brush is sort of stepped, with the edge making contact with the commutator being only about 3mm wide. Still, half an hour or so of v-e-r-y careful filing and test fitting produced a brush that fits.

Re-assemble the dynamo and refit. Well of course the timing chain had slipped on the sprockets but I managed to finangle it back to give the correct valve timing and then refitted the dynamo. V E R Y tricky operation and I lost the timing chain again a couple of times, but eventually - success!

Now all that was needed was to retime the distributor. This time I took the trouble to get the HT lead sockets in a nice position relative to their respective cylinders.

Final check of Advance and Retard control, spark ocurring at TDC, drop of petrol in the carb, give it a go. JUBILATION!

All charging functions now fully operational but I think I may need to fine tune the third brush position as the charge is a bit excessive at 8 amps.

Still, I am very pleased to have overcome what MAY be a final obstacle.

As ever - we shall see!

PS. Would anyone care to check my (current) version of the circuit diagram before I publish it to the cogniscenti?

[Keith Clements]

Ian,
Just publish and we will add our comments. You can always upload an updated version if the original proves to be wrong!

[Tony Fearn]

TA RAAA! JUBILATION! All charging functions now fully operational but I think I may need to fine tune the third brush position as the charge is a bit excessive at 8 amps.

....RAAA - BOOM-D'Y-AY

Nice one Ian. It's all down to the detail, and perhaps an 8 amp charge in Summer position is a bit excessive. Don't boil the battery! I've tended to set the Winter charge to just show one or two amps when side and head lights are switched on.

There have been dynamo brush sets in the past on eBay, and perhaps other sources also have them ready made.

eg:- http://www.ebay.co.uk/itm/238038-LUCAS- ... 484c2c1b00

Tony.

[ian Howell]

Thanks for the encouragement one and all. I have seen the brush sets on eBay and elsewhere but these are generally for the C45 series of dynamos and mine is simply C4. They may well be the same, but at those prices I am not prepared to speculate. It works as it is and that will do until I can be sure.

So where am I now? Well there is a slight rubbing from the rear brake drums which I think is due to the segments I had to weld into the back plates to replace rusted out metal, so a bit of fettling should sort that out.

There is the small matter of the rear offside wing, which needs at least a cosmetic coat of paint before MoT, and the offside top rear quarter panel has a distinct 'bulge' which needs to be addressed. This was the first panel I ever 'bashed' and I was prepared for others to be similar, but my skill (luck?) has improved and now that panel irritates me.

All the offside nipples need greasing and I want to replace the rubber support pads on the radiator AGAIN. They were replaced as one of the first tasks about 8 years ago and now . . . Any vacancies for painters on the Forth Bridge?!

All the above is of course without any work on the fabric body. I have made a temporary roof cover with a cotton sheet liberally painted with an oil-based undercoat and then gloss paint. It seems to be more or less watertight and doesn't look too frightening. I plan to cover it properly with a suitable fabric (advised by Michael K-O) but not until at least after the MoT.

I have sort of made a start on the interior upholstery, but that is going to involve yet another new (to me) skill set. I may depart from my endeavours to maintain originality here - at least as far as the front seats, which are in tatters. are concerned. The back seat is sort of acceptable but I have acquired enough REAL LEATHER of the right colour to at least do both the front seats. As the original Rexine is apparently unobtainable (it seems it involved nitrocellulose, which is not considered a good idea these days), I cannot in any event revert to original materials, so why not leather? At least THAT was available in 1930.

So there I am. Or rather I will be when we get back from Wales. Funny thing, the news is full of reports of apalling weather everywhere including Wales, but here in Llandovery, on the main A40, there is none! Not a bit. 10 or 12 miles up the road in any direction - disaster - but here?

Evening all.

[AlanBartlett]

Keep up the good work Ian. I'm finding this topic quite useful, Ive yet to investigate, but am now experiences similar charging non charging situations. I believe its maybe the brush adjustment as I havent really had much to do with them since before I started on the engine. 5 years ago. So reading up on this will hopefully point me in the few right directions. Im glad to hear your almost up to mot stage and are finding ways to get it mobile and weather proof and road/mot tested before you start on all the prettier bits. Have you any pictures I remember seeing it at wakefield. Its great to see other people tackling the same things your on. Its what makes the club helpful.

[ian Howell]

Alan: -

Sorry I missed you at Wakefield. I did nearly catch you on the dinner night but you had loads of company and time just slipped by. Great 'DO' though, wasn't it?

And of course, congratulations on your win at the Classic Car show. It's just a shame that it has taken me so long to get started on my 'repairs', (I bought the car in 1966 as a retirement project, but I had to take late retirement from my self-employment so I have only been able to make inroads in the last four or five years).

The electrics are really quite simple - apart that is from the charging circuits, and even they are becoming clearer as work progresses. Moving the third brush even a short distance seems to make a big difference to the charging rates. GO GENTLY!

Vitally important though is the need to remember that every circuit also passes through the metalwork of the car back to the battery negative.

As well as a good 'negative' connection from the battery to the chassis, a good 'earth' connection on the oval Lucas panels is VITAL with the wooden (insulating) dashboard.

Rusty joints between for example, the front wings and the chassis, will cause problems with the front lights. Similarly, dodgy 'earth' (chassis) returns from the back lights can cause some interesting problems, for example side lights going dim when the stop light operates.

Basingstoke looms and I have yet to get to the MoT and it looks as if March will be spent in Wales. Tempus Fugit!

I have still got to make a few adjustments to my version of the circuit diagram in light of my experiences and then I will be pleased to send you a copy "without prejudice", meaning if it's wrong - shame!

Keith: - I have drawn the diagram with 'Paintbrush' and the document is about 50Mb!
Could I save it in another format that would make it manageable, without losing the colour codes?