Alternators in a Dynamo body

[DTW]

What experience do members have using these units? Last year on our annual tour of France a Dynalite regulator failed and over charged, burning out the electronic ignition module. This year it just stopped charging. I have fitted an alternator as on our summer tours we run a cool box(6A), electric fan (Kenlowe 4/5A) and electronic ignition (4A). If we need to run wipers and lights as well it all becomes a bit marginal for the old dynamo. I have been told the regulators in these units are sensitive to high temperatures. I wonder if, as the Kenlowe is fitted in front of the rad, there is a lack of cooling air around the area of the dynamo/alternator mount. I have no problem with engine cooling!
The breakdowns weren't too much of a problem as I carry the dynamo and regulator in the boot.
DW

[Lorimer]

Hi DTW,

I have a 1960 SP 250. The generator is now possibly getting tired in that it only charges at about 1500 rpm and above. So I've begun to investigate Dynalites. Holden carries a good stock (https://www.holden.co.uk/displayProduct ... =Dynalites). The unit for the SP 250 is the C40. It's not cheap at £335. It could be worth a call to Holden's Julian who is Holden's expert in this area.

Lorimer

[Josef Eckert]

Lorimer,
Please be careful. I can only recommend to have your original generator repaired.
I am an electronic engineer and retired, but still working "just for fun" two days a week for the biggest spare parts supplier for mainly british classic cars here in Germany. One of my tasks is to check all customer complains as regards electric and eletronic components.
There are severe problems with those alternators in "generators bodies" supplied by two producers. We have outage rates which are unbelieveable high.
An orginal C40 long Dynamo in goodcondition with a correct adjusted original RP 310 regulator is fully capable of taking all the load of switchhed on lights, electrical fan (also not needed when your engine and radiator is in good condition), etc. No need to do any modification.
I can only recommend repair the failing components properly and not solve problems with components causing even more problems.

Josef

[Ian Slade]

Charging at 1500rpm is about right for the dynamo, not worn or tired, the car was designed to rev at 6000rpm, the dynamo is geared not to overspeed at that rpm, consequentially with modern congestion on our roads and speed limits the chances of charging the battery are getting few and far between. Most SP's will not be taken above 4500 rpm these days so change the dynamo pulley wheel to charge at 500rpm, that's the cheapest option and probably the most reliable.

[Fossil]

Co-incidentally I've just had to attend to the "Dynamator" that I fitted to my Century last year. This is the rather cheaper Chinese imitation dynamo alternator. To fit it I had to use a B type fan belt since the A type is too narrow to work with Century crank and water pump pulleys, but even the B belt had to be really tight to work without slipping on the crank pulley with a high load.

Anyway with only a few hundred miles done the Dynamator produced developed a dreadful noise following a short motorway exercise taking the car up to 70 mph very briefly in June. I took the noise to be due to bearing trouble in the nearly new but inexpensive device. However upon removing it a couple of days ago it emerged that the aluminium B belt pulley I had bought from Holden had distorted so that it wobbled on the alternator spindle; consequently the Woodruff key had also been damaged and loosened, and the alternator fan loosened; it was the fan rattling on the spindle which was the source of the noise, and the bearing appeared perfectly fine.

What to do? I contemplated replacing the dynamo and original control box to return everything to standard with the standard Conquest fan belt, but my Scottish nature was unhappy to retire an undamaged Dynamator, and searching the dark corners of the garage turned up a steel B type belt pulley from an old V8 saloon 11 AC alternator, which clearly I should have used first and saved the cost of the aluminium one. It is however a larger diameter than the standard alternator pulley although smaller than the dynamo pulley. So with a fresh Woodruff key and alternator fan, the steel pulley was fitted using a touch of bearing lock fluid to keep everything tight. I had to leave the dynamo bracket bolts loose to refit the B fan belt over the larger steel alternator pulley, but it all went back together okay once everything was sorted and is now back in operation successfully, although not road tested to 70mph yet. Interestingly with the slightly larger alternator pulley the ammeter is now showing a variation in charging rate as it did with the dynamo, although to a lesser extent. I did however fit an extra 27 amp cable between the alternator output and the starter solenoid when I wired it all up originally to avoid overloading the original dynamo to control box cable, the RB106 box being replaced with a modified item functioning as a junction box, for the sake of "originality".

Apologies for all the foregoing verbiage; the message of my experience is that aluminium pulleys sold for Dynalite or similar devices may have drawbacks. I'm unable to explain the distortion of the B belt pulley that I used, purchased from Holden, other than to say that I had to keep the fan belt very tight to stop it slipping on the crankshaft pulley during the winter, for example when blipping the throttle with headlights and other loads on - the problem seemed to be more troublesome in cold weather, perhaps not surprisingly.

As to why fit an alternator when a dynamo should be quite adequate for the task? My answer is that it keeps the battery in a better state of charge which keeps the clock working. Over several years it has appeared that the clock stops because the battery voltage is too low, and works continouously when the battery is well charged - that is following the reconditioning of the clock first.

Cheers

Geoff

[Petelang]

This seems to support what I had believed all along, that an Alternator within a Dynamo body is not a good idea. Being a former Joseph Lucas Apprentice, we were told how higher output generators create considerable amounts of heat and therefore Alternators were fitted with significantly more efficient fans and had far more ventilation slots in order to dissipate this heat.
If you place a stator generating at least double the Dynamo capacity within a narrow fully closed tube it hasn't got long to live.
The principle of a dynamo is that the Armature, which is spinning in the air vortex created by the front fan, produces the power and consequently the air cools it.
On an Alternator, the stator develops the power and is the static winding, whereas the rotating rotor is merely the field source taking less heat. Hence the stator is heat sinked by the (generally) aluminium casting front and rear brackets, coupled with very big vent holes front and back and a whopping effective fan behind a small pulley.
My dad always used to tell me, you can't get a quart out of a pint pot and I guess that sums it up.
If you need more power, fit an alternator. Alternatively, reduce your consumption by led lighting and tune your regulator to 14.5 volts and eliminate any volt drop on the wiring (you may need bigger cross sectional cables from Dynamo to take maximum power without volt drop.
However, one oft made mistake, to fit a bigger battery, is not a solution since it will require more amps to replenish it, unless you keep it on a smart charger when not in use.
Peter

[Vortex O'Plinth]

If the rest of your electrical system is original then there's really no justification for replacing the dynamo with an alternator. The main reason for a switch is the fitment of an electric cooling fan in place of the original. A change to R&P steering renders this essential, but I know some cars have them to improve the sometimes marginal engine fan cooling. Even with the extra current demand imposed by the fan it's worth considering the duty cycle your car is likely to experience.

A dynamo is isolated from the battery at tickover by the control box, so there's no charging if your car spends a lot of time in traffic jams. With an electric fan running, your headlights and windscreen wipers on the combined current demand could equal or exceed the dynamo output, so there's nothing left to recharge the battery - but how often is this likely to occur? My car is not a daily driver; it doesn't go out in the rain (except by accident) and it's very rarely used at night. A replacement three row aluminium radiator ensures that the fan very rarely cuts in. I've retained my dynamo and combined it with an original pattern 88Ah@20Hr battery. In the garage it's trickle charged by a CTEK charger - which since it's a 'C' spec car, I can can connect to the inspection lamp socket.

If your circumstances mean the car is used regularly in stop/start traffic when it may be hot and wet and at night then the alternator is probably a good idea. The supply current can be up to three times that of the dynamo and it's available at much lower engine speeds. As Peter points out, a conversion to led lighting will significantly reduce current demand, and might be more reliable than a Dynator.

[Phillmore]

Surely the problem is (and this is where I risk offending the more PC members of the forum) that the item in question was made in China?

[Josef Eckert]

One product is assembled in the UK using components from asia (i.e. South Korea).

[Fossil]

Oh dear, the point I was trying to make in my admittedly overlong earlier post was that, although I thought that the problem I've just dealt with was due to failure of my Chinese made "Dynamator", it turned out not to be; the fault was actually in the aluminium pulley purchased from the Holden website's Dynalite accessories section, and nothing to do with overheating: the Dynamator has been left in place with a better (steel) pulley.

Since the original post concerned failure of a Dynalite alternator in warm weather I thought it was relevant to those who might be considering buying one; aluminium pulleys may not be a good idea and Dynalites are after all very expensive while Dynamators are less so, therefore the latter may therefore be preferable to the former on cost grounds alone.

I have no idea where Dynalites are actually made.

Finally although my earlier post referred to a Dynamator fitted to my Century, my SPs both have conventional alternators (17AC), which would perhaps be a better choice if the car is going to be used for touring in warm/hot countries (no criticism intended).

Cheers

Geoff