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Dynamator refurbishment
Having tried and failed to get a consistently reliable 12v charging system to work with a two brush C35 and RB106 regulator I have always fancied the idea of a Dynamator. I have managed to do my A7 driving with no charging, setting off and getting all day on the 12v battery charge (e.g. the arduous Beamish Run) without issue, just that red light shining at you unblinkenly. YES; I do know about the Dynamator gear problems with the angst that has caused but that's easily avoided and I don’t recall anyone saying there had been similar widespread bearing or internal electrical problems so it seemed a good technical step forward. Stuart Giles had had a similar go at a defective Dynamator, posted here, with helpful photos (thank you), that had an open circuit rotor. Accuspark don’t make them anymore and after enquiring about them I get the impression after what happened and what was said that they want to distance themselves from the A7 variety. My opportunity came a couple of months back when a ‘spares or repair’ unit came up on that well known on-line auction site. Once secured, I immediately started a strip down to determine what was ailing it, hoping it would be something easily fixed. It was obvious someone had had it in bits before and not found the fault(s).
It comes apart in a similar way to a C35, go in from the distributor end removing the circlip and disc to slacken the drive gear nuts at both ends. Remove the distributor drive worm (not losing the tiny key) by drawing off the end housing. The regulator and brushgear can be removed from the opened end and the internal body terminals similarly from the ugly external block (take a photo of the connections on your phone and make a sketch of the wiring arrangement!). Remove the four body screws and unthread the rotor. Testing at this point revealed that the rotor winding was open circuit (was this the same Dynamator that Stuart had a go at?). Oh poo. The fault wasn’t visible so I was determined to press on and perhaps rewind the rotor. That necessitated removing the bearing and sliprings. A simple puller got both off though the bearing was very tight on the spindle. But despite a valiant attempt I could not get the rotor claws off the spindle, they were V tight. Having the coil now unsoldered from the slipring I noticed that one tail end wobbled about and with a bit of poking about with a pick I found the winding was broken just where it exited the coil towards the sliprings. Eureka!!! Happy days all round! Further probing released the first turn of the winding and I was able to pull it through and re-establish the winding testing out at 4 Ohms so there was fortunately only the one fault. The body coil and rectifier tested out OK with no more open circuits or earth faults. Reassembly is the reverse of the above. You can get the gear end bearing out by removing the three internal screws and sliding everything off the spindle.
My mission didn’t finish at this point. I didn’t like the four cross head screws retaining the body and replaced them with more aesthetic M5 hex heads. Similarly, the rubberised terminal block looks decidedly non-vintage and I thought the way the connections were made with a soft insulating spacer inside tempted a poor connection. I extended the two outgoing cables and grommeted the body adding a Lucas type ‘brushgear’ coverband and connecting box. The wiring loom also needed reconfiguring. Be careful with the RB106 wiring diagram on the Accuspark site. It implies that the D terminal of the Dynamator should be connected to the ‘power’ side of the electrical system whereas it should be connected through the ignition light loop and the heavy cable from the rectifier should go into the power system. I found by gutting my RB106 regulator that the cabling and terminals could remain as they were with a shorting loop between the F and A terminal making the right connections.
I write this hoping it will help someone else in the future, and encourage them to have a go. Other bits of info that may be helpful are that the gear end bearing is a 6202RS, the same as the C35 and the distributor end bearing is a 6201RS, both being sealed bearings. The rotor claw is tiny compared to most modern alternators at 69mm diameter. The only rotor that I could find on the informative Wood Auto site this size was a Denso for a Kuboto lawnmower! The brush assembly and sliprings look very similar to many advertised on that well known on-line auction site. As Stuart pointed out, the regulator could be replaced by another if you have a problem. BTW, the brushgear is very fiddly to get back into place, compressing the spring loaded brushes while aligning the two screws, wires and plastic spacers is difficult. I put in some slightly longer screws and filed them to a point to help them find the holes.
Mine sprang into life generating over 10 amps initially then settling down with a steady 14.6v. The red light is no longer my constant driving companion! I hope it continues to do so and this helps you too.
Thank you for sharing this, Dave, it will be very useful to many.

I have a 6v Dynamator fitted to the Pearl and a 12v one fitted to the Highland Coupe - both still work as they should and I was beginning to wonder if they were the only two still doing what they were supposed to.

What do you think caused the failure in the one you have?
The one I have on my Pearl has worked relatively well over the years, though it would often take a mile or two to spring into life each morning. More recently, whatever the system is for controlling the charge rate has 'failed' and the system now charges at 10 amps constantly. This reveled itself on the Eurotour, where I couldn;t do much about it. Consequently, it over charged the battery, which I was able to recover when I got home. I have decided now though to return to the standard system - particularly in light of the change to LED lighting that I have made..

It was an interestig experiment and, had it been really tested thoroughly before releasing to the public, I'm sure would have been an excellent upgrade. However, that has proved not to be ... 'After sales service', shall we call it, has been lacking..
Back in the early 1970s I tried a two brush C35 with a RB 106 regulator for a 12 volt conversion and soon realized that the regulator couldn't handle the field current so I converted the C35 back to 3 brush binned the regulator and fitted a 12 volt CF 3 cut out which I ran for 10 years with no problems. In the mid 1980s I took my boss's alternator in for repair in a 6 volt Seven, when I collected the repaired alternator the guy who'd spotted my Seven said what you need is one of these. It was a 12 volt alternator regulator which cost £4.50, over the next few days I worked out how to wire it up using an old 12 volt battery off our Cortina and the CF3 cut out fitted with a 33 ohm resistor and a two brush C35, It worked well so I went back and bought another regulator as a spare to go under my seat. In due course our other two RNs were equipped with the same set up. Over the following 30 years I had one regulator fail, which at £4.50 didn't break the bank, this caused a problem as the business closed when the owner died and it took me a while to source a replacement.
I must admit that i have occasionally thought about ways that I could improve the lighting on my own Seven, but have tended to be somewhat conservative in this, given that my car is so original. The dynamo gives 10 amps reliably which, with 24 watt headlamp bulbs just about balanced the current consumption with all the lights on. However, 24 watt bulbs are grim unless you have the road to oneself, so I upgraded to 36 watt bulbs, which have made the car much more pleasant to drive in the dark. Unfortunately, with the headlamps on, the ammeter now shows a net 4 amp discharge. Given that my car has plain glass headlamp lenses (?), I don't think that LEDs would look right somehow, so I have decided not to go down this route.

I go to Wrexham once or twice a week and, if I go in the seven, this often requires an hour or so's drive in the dark returning home during the winter. Since the headlamp bulb upgrade, I have had one or two instances where the battery was flat the following morning, so I have simply abandoned  my usual practice of switching to half charge after about ten minutes running and keeping the car on full charge all the time,  checking the battery every week and topping it up as required with distilled water to ensure that the plates are well submerged.  The battery itself is the same one that came with the car and was new at that time. It is now over four years old and shows no signs of giving up the ghost so I must be doing something right (unless I am just lucky).

I would imagine that such an approach would be part of the judicious management of the car in the days when our forebears were using these cars as everyday transport.
(18-03-2023, 07:08 PM)Speedex750 Wrote: Testing at this point revealed that the rotor winding was open circuit (was this the same Dynamator that Stuart had a go at?). Oh poo.

Well done for finding and fixing the faulty rotor. Happy to confirm that all the left over Dynamator bits from the repair that I did are still lingering in my workshop somewhere Smile 

It looks like the Dynamator I repaired using the rotor from a donated 'dead' unit has failed again, and I hope to have the unit back here in the workshop over the  next week or two. I will have a look to see if it's the rotor I replaced that has failed or whether it is some other fault this time. The other components are fairly generic so should be fixable if the regulator or such has let out the magic smoke.
Which makes it more amazing that the products from the late lamented Joseph Lucas used on the Austin Seven are often still working well some 90 plus years later. 

I am slowly getting through a massive two volume history by Harold Nockolds finishing in 1975

Joseph Lucas was done to death by people who didn't have a historical interest in the company - I found a story of the sad end of the company after it was sold to a con man in America (who was an Englishman as well).
Thank you for the responses to my overly long tome. My rotor winding had a break just as it exits the wound coil taking a loop round the nylon guide, fortunately it was the top turn rather than the first and I could unravel enough to remake the tail. It wasn't obvious why it had failed, it didn't look overheated or mechanical damage and I can only imagine the wire had a kink that had been pulled tight, hardening the copper. Surprising on such low mileage (the brushes still had machining marks) as presumably it was made in a production facility that will be turning out thousands of similar windings. I am wary of expecting it to recharge a flat battery, that seems a recipe for a disaster. Replenishing what the starter has taken out (not much with 12v starting!) and balancing the running load will be sufficient for me!

Anticipating a rotor rewind I consulted that font of all knowledge; YouTube. If you want to see some clever guys in South America and the Far East (?) rewinding rotors with very rudimentary facilities; look it up. We are very fortunate in the western world to have an endless supply chain with multi-choices for normal car spares, seemingly unlike some areas. Their ingenuity and making do approach is inspiring for those of us who prefer to be hands on where we can.

Anyone else had a Dynamator non-gear problem?

Thank you, Dave.
36 watt headlight bulbs is a bit on the big side David, I find 25 watt is plenty and I get the odd modern flashing me and you don't want to look at them. I did try LEDs but they just gave loads of light with no definite beam and took much less amps I gave up with them when they both blew leaving me invisible until I switched to sidelights.

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