Hi James,
Because I made the conversion some years back, and I was having to make my own mind up on how to do it, I never really thought beyond using the Bosch regulator that came with the dynamo(in the Beetle it is bolted on top). This combination has worked well enough for me not to bother to make any changes, although I have thought about it now and then. This is largely because it can still give a charge to the battery even when delivering 15 to 18 amps to the lights and ignition! It is a 6V system.
The solid state regulators you and John Newell suggest are probably the best way to go and you may prefer a 12V conversion as described by Malcolm Watts in the Cornwall Tech pages - see www.austin7.org.
I would be interested to learn how you subsequently make out with the solid state regulator, meanwhile email me if you want some more details.

Ron

Location: Thornbury

Gentlemen, let me clear up a few of your doubts and questions.

There is no longer any need to increase the output of your cars standard dynamo nor is there any need to fit a higher output (Bosch) type dynamo. Fitting a higher output dynamo brings with it problems that might not at first be clear especially to those not in the know so to speak. On Sevens fitted with a C35 three brush Lucas dynamo wiring was designed to cope with currents of 11a. This is the max safe output of the C35 in 6v three brush form and gives 66w to play with assuming the unit is in good condition.

In the past, in a quest to fit brighter headlamp bulbs and gain brighter stop/tail lamps, people have modified the standard dynamo to give 12v by fitting a 12v cut out or diode in place of the cut out. Some have earthed the third brush and connected a two brush regulator in the effort to get a higher and better controlled output. To get 12v from a std 6v armature you have to spin it nearly twice as fast. Not ideal for a low revving Seven. Others have modified the Bosch Beetle dynamo (capable of outputting 28a if connected to a suitable 6v regulator). The 6v Bosch mechanical regulator as with any mechanical regulator had no means of limiting its field current so if demand is there the regulator will allow the dynamo to output 28a. The Sevens ammeter and wiring is designed for 11a. Need I say more. The only crude way to add any protection is to fit a fuse in the regulators output.

For those that prefer 12v over 6v, the only proper way to get it whilst keeping things looking original is to have the original dynamo properly converted to a 12v machine and at the same time, a two brush machine. This if properly done will give a very efficient 12v dynamo that looks exactly the same as it did in 6v form. Two brush gives much more controlled charging over the three brush or fixed rate system. This is essential for our cars batteries especially modern sealed types which don't like a high charge rate.

My conversions are very popular and come in 2 outputs. 8a which gives 96w. Plenty for any standard Seven. I also do an 11a version giving 132w for cars that require a little more (usually for Seven Specials and other modified cars using the Seven engine). Connected to a modern efficient electronic regulator, the two work together in perfect harmony. The regulators that I supply are field current limited and fuse protected. They are also internally protected against outside influences. The 8a regulator will only allow the dynamo to output 8a and the 11a regulator of course, 11a thus protecting both the dynamo and regulator. I also do the same two brush conversion but keeping to 6v with an 11a electronic regulator. Both these conversions allow the dynamo to run as efficiently as possible.

I sell a range of 6 & 12v LED bulbs, light boards and flasher units suitable for all vintage and classic cars. These items lower the demand on a cars charging system. Up until last month they were available for side, stop, tail, dash and indicator lamps but in October I introduced after many months of work, a range of LED head lamp bulbs, not only to give brighter, whiter lights but also to seriously reduce the load on our cars systems. My own 12/4 Windsor is now completely LED. Total load on the system when it was all filament bulbs was 8.5a. With LEDs that figure has dropped to just.................1.6a. Yes, 1.6a.

My LED headlamp bulbs are available in 12v 36w and 12v 50w ratings. The 36w variety use 0.5a each. The 50w use 0.75a each.
As from Wednesday 4th December (next Wednesday) I will have in stock the 6v variant available in 36w form. Both 6 & 12v are suitable for cars with fixed or dipping reflectors. Available in BA15s and BA15d caps.

I am currently working on my prototype dipping LED bulb which if all goes well will be available in earl January, maybe sooner (Christmas gets in the way of development/production!). These will be available in 6 & 12v form as 36/50w with BA15d, BPF, APF, Bosch BA21d and Marchal BA21d fittings. At 6v they use 1a dipped and 1.5a raised. In 12v form, 0.5a dipped and 0.75a raised.

So, you too can have pure white lights to the front of your car and bright red lights to the rear WITHOUT draining your battery even on the longest of night time runs. A 6v Seven with an electric wiper can have an everything on load as low as 6.5a or a lights/engine on load as low as 4.1a. A Seven converted to 12v can have an all on load as low as 4.6a or a lights/engine on load of just 2.6a.

The over all benefits are:

Brighter, whiter headlamps
Minimal current consumption
Your dynamo never runs warm so is always running efficiently (more heat = less efficiency)
Increased MPG as the dynamos load is minimal so the load on the engine is also minimal (the more the load, the harder the dynamo is to turn)
Peace of mind even on the longest of night runs with lights and wipers on

Not a lot more I can say but that I'll post on here as soon as the 6v bulbs are in stock.

I welcome enquiries and questions via this forum or through the contact page on my site.
You can also contact me at info@dynamoregulatorconversions.com

See us next at The Autojumble Midlands at the Ricoh Centre Coventry on January 5th 2014.

Peter

Location: Lincolnshire

Thanks Peter & Ron for your words of wisdom.

My original driver for going down this path was:
My original Lucas dynamo is in a bad way
I have a 6V Beetle dynamo that's in good condition

Ron has kindly provided excellent further details on the conversion, and I'm beginning to think that it may be a little beyond my current engineering skills.
Further, the fact that 6V LED headlamps are soon to be available (they weren't 6 months ago) leads me back to looking at understanding the issues with my Lucas Dynamo and trying to fix it.

Thanks again all - Ron - I'm sorry for bottling out! It just seems a little too advanced for my first lathe project in 25 years.

All the best,

James

Location: Hove

James, I refer you to my reply to an earlier thread "Dynalite conversion"

I converted my RP to 12 volts over 2 years ago, as I needed better lighting when driving to & from work,about 16 miles each way.A VAST IMPROVEMENT. Better starting,acceleration under load,charge rate,can use LED bulbs and other accessories such as GPS CD's etc.
The conversion was easy.The existing 6 volt dynamo, modified to two brush operation, will easily produce the 12 volts required and the voltage control is by a electronic unit under the dash out of sight.A change of bulbs,coil,battery and you're done.Not a difficult job,control unit purchased from Dave Lindsley & cost in 2010 was £106.& includes instructions on dynamo mods again very easy.A lot cheaper than fitting non standard looking parts.The only visual difference is the dynamo brush cover which I changed for some fine wire mesh to aid cooling.PM me if you want more info.Peter.

Location: Piddle valley, Dorchester.

Location: Shropshire

Ian, I am now testing what I hope will be the final production bulb. We had problems with the initial design but I believe we have now got the bulb that will go into production. I am testing it at the moment. Initial results are very good with more testing over the coming weekend. I'm hoping to have it available in January 2015 with BA15d, BA20d, BPF, APF and BA21d caps.

Watch this space as they so or more so, watch the homepage of my website for updates.

Peter

Location: Bomber county

Without trawling through all the old posts I seem to recall that the VW dynamos rotated in reverse direction and that, brushes being offset relative to the poles, some adjustment of brush position is necessary/desirable. Perhaps someone expert can comment.

Any theories on how VW unit achieves such a high output would be of interest. Are they of magnetically superior or bulkier steel? More ampere turns on the fields? As Seven ones often operate at or above solder melting temp, VW can hardly run hotter!

In tinkering with old Brit cars I have often connected an 11v-17v range analogue voltmeter and been surprised at the effectiveness of electromechanical regulators. What is it about the VW regulator which causes it to charge relentlessly? I gather high dyn residual magnetism can have this effect at high revs but VW dyn on a Seven is not high revving.

Decades ago I had loan of an oscilloscope and with em regulators was surprised at the total absence of charging regulator pulses at the battery terminals. But it was long ago and I may have done something wrong. I suppose few now have access to such cars, but has anyone else checked? What is seen with a traditional rectified 50 cycle charger? The battery internal resistance is very low but the charge current pulses must be considerable, far in excess of the average indicated by the ammeter.

The LED solution is very desirable. All generated power has to be transmitted through those long suffering skew gears. Modern oils are marvelous but not perfect.

Bob Culver

Location: Auckland