Auto voltage control box/regulator unit

[Tony Hillyard]

Greetings everyone,

I am new to this site so please excuse what might be a dumb question.

I have a 1932 Sleeve valve Panhard fitted with a dynastart. The charge is almost nil. I am due to check the dynamo side of things this week but I have a feeling the voltage control box/regulator might well be the problem.

I have some experience with normal 12v regulators (usually with at least three connections). The one on the Panhard has just two connectors. Inside I see no sign of the normal coil cut-out set up.

Any ideas where I might find a replacement part with just two connections and with the conventional coil cut-out arrangement.

Any help or advice would be gratefully received.

 

[PEG]

Hi dude,this sounds more interesting,than the usual requests...

Your regulator sounds like it may be voltage only,but without more details,or pictures,it would be only a guess.

What type of dynamo is fitted? Its' size and type,may determine what replacement can be used. It has to be remembered,that these systems were "agricultural" in the extreme,compared to modern devices.

 

[Tony Hillyard]

Thanks for your response PEG. She has a 12v Paris-Rhone Dynostart. The output, Im sorry I have no idea. Agricultural is just the word. No wonder Panhard went out os business.
I will try and upload a couple of photographs - the Dynostart and what I imagine is the voltage control.

 

[PEG]

Hi,this set-up looks similar to Dynastart i played with on an ancient boat engine. Some of the vintage narrowboats had them,but most were modded out,even if the engine was retained,due to their liking for torturing batteries...either flattening or boiling!

They are very expensive lumps,now,and are obviously wanted to be retained,as part of original equipment.

Test and repairing is usually via two routes. Expensive high-end specialist rebuilders,or dedicated enthusiasts. The latter being found through owners clubs,and the like.

From memory,and it was a while ago,there are a few basic measurements,regarding continuity and coil winding resistance,then all other readings are done running,through the rev range.

Has that stone-age regulator got one set of contacts? If so,they should have a discernible gap,and continuity across when closed,the operation being checked against battery voltage,when running.

Without any listed values,for coil measurements,i suppose a good strip and clean,then a test of start function would give you an idea,and something to do on a slow afternoon :vanish:

 

[Tony Hillyard]

Morning PEG,

Thanks for that. I have rebuilt Dynostarts before with some success. My pal has another earlier Panhard which I managed to get running/charging OK. What really baffles me is that "stone age" voltage regulator. I like the description, by the way. Panhard seemed to have two types of wiring schemes. On this 1932 car the Dynostart has just one heavy cable from the Dynostart to the starter switch. On the other style of wiring they have one large cable and two small ones. As you can see in my photo this Dynostart has had the two small terminals bridged!

I have managed to get a copy of the wiring diagrams but I can't work out how that voltage regulator works. I have seen another Panhard of the same period, but that one had a conventional voltage regulator.

I know Panhard had a reputation for "off the wall design" but this has me beat!

 

[PEG]

Hi,have you an idea where the "regulator" pictured,is wired in? Also,if you could post a picture of the model year appropriate wiring diagram,this may give an indication of a modification.

The problem with the older stuff (and i have worked on hot-bulb and steam engines) is that for the first part of its life,it was new,and nobody dared to mod it.

Then,much later on,when it was rare and valuable,nobody dared to mod it....but for the vast section in between,every mechanical hero born,probably had a play!

Much depends on just how original you intend to keep it,whilst keeping things reliably functional. :tongue3:

 

[Lucien Nunes]

Sorry, did not see this earlier. The device pictured is a semiconductor diode, obviously not original (probably 60s or 70s) that is probably used as a blocking diode in place of the cutout relay that is normally incorporated in the dynamo control box. If this is the case, it will be between the output terminal and the battery, and will have no relationship to the charge rate.

Alternatively, it might be a zener diode used to reduce the field current to a fixed low-charge rate, in which case it will be connected in the field circuit instead of the output, and the unit will still require a cutout relay. As per PEG's post, indications of the connections would be helpful.

 

[Tony Hillyard]

Sorry, did not see this earlier. The device pictured is a semiconductor diode, obviously not original (probably 60s or 70s) that is probably used as a blocking diode in place of the cutout relay that is normally incorporated in the dynamo control box. If this is the case, it will be between the output terminal and the battery, and will have no relationship to the charge rate.

Alternatively, it might be a zener diode used to reduce the field current to a fixed low-charge rate, in which case it will be connected in the field circuit instead of the output, and the unit will still require a cutout relay. As per PEG's post, indications of the connections would be helpful.

Good Morning,

Very many thanks for your replies. I will try and upload a wiring diagram of the Panhard. I'm sorry it is in french but I will translate where necessary.

As mentioned, this car has just one cable from the dynostart to the wiring loom. The large cable from the dynostart seems to run direct to what was originally a normal style of voltage regulator. I'm also a bit baffled how the dynamo puts it's charge back into the battery. But then perhaps I'm a bit thick.

Here in France it is very difficult to get any useful technical information, particularly about prewar Panhards. My French friends tell me it is a cultural thing, everyone likes to keep their knowledge to themselves. You can ask the Panhard club for copies of specific articles but that is all. There is no central book with all the tips or information. I have received most of my Panhard info from a German friend.

So any help or suggestions would be gratefully received.

If this is too small please let me know.

 

[Lucien Nunes]

OK, I'm not familiar with this setup but here's what I can infer from your pics along with an explanation of why I think it is like it is:

Traditional starter motors (before permanent-magnet types) were series-wound motors, as these give the best torque characteristics. Most dynamos were shunt-wound, as this gives easy control of voltage using an external voltage regulator that interrupts the shunt field circuit. Some earlier dynamos used a 'third brush' to power the shunt field, exploiting an obscure characteristic of the dynamo to make it crudely self-regulating without an external regulator.

The conventional 'modern' dynastart incorporates both a series field for starting (terminal 30) and a shunt field for generating (terminal DF) to get reasonable performance of both functions from one machine. When the starter button is pressed, current flows from the battery through the series field to the armature, making a series motor. Once the engine is running, the voltage generated by the armature energises the shunt field and closes the cutout relay, delivering output back to the battery without the series field in circuit. The cutout relay is necessary to disconnect it from the battery when the engine is not driving it fast enough to generate; as soon as its voltage falls below that of the battery it will motor instead and try to drive the engine.

A shunt-wound dynamo will run as a motor when its armature is connected to the battery, just not as 'torquey' a motor is if it had the benefit of the series field. Thus, it is possible for a dynastart to have just shunt field and armature leads, as I think the units you mention in other Panhards have. They would run as a shunt motor or shunt generator according to speed, motoring when the engine is stopped and generating when running fast enough to overcome the battery voltage. Either a vibratory regulator or a manually controlled resistance could be inserted in the shunt field circuit to limit / adjust the charge rate.

The control box depicted in the circuit diagram appears to contain a normal cutout relay. When the engine is stopped, this is open and the dynastart is disconnected from the battery. Pressing the starter button bypasses it to run the dynastart as a motor. Once the button is released, it is again disconnected until it builds up enough voltage as a generator to energise the cutout, which closes and connects it to the battery. The photo of your 'control box' shows a 1960s semiconductor diode instead. This can fulfil the function of the cutout, by preventing the battery discharging into the dynastart when the engine is stopped or running too slow to generate a voltage in excess of the battery voltage. Once it rises by a few tenths of a volt above battery, charging current can flow through the diode. I presume the original electromechanical cutout relay failed and this was the alternative solution used, which should work OK.

Now we come to the question of regulation. The brass link across the two small terminals of your machine suggests that its shunt field runs at full strength all the time, there being no regulator or adjustable resistance in circuit. This would tend to cause it to overcharge or become overloaded at high engine speeds, if it were just a normal dynamo with its output connected directly to the battery. Perhaps it is partially self-regulating - a clear picture of the brushes that shows their relative positions and connections would be very helpful in clarifying this. An alternative is that the output, when connected to the battery via the cutout rather than via the starter switch, has a resistance inserted to limit the charge current even at high generated voltage. Tracing the wiring would clarify this point.

You have a charging problem. To troubleshoot it, first we need to prove beyond doubt what the intended means of regulation was. Having no other information here, to help you further I would need some questions answered by tracing wiring and taking readings with a multimeter. My first would be:

Is the diode (shown in the second pic) connected directly in parallel with the starter button, without any charge-rate limiting resistance in series?

Does the dynastart have the same number of brushes as field poles, spaced at equal angles around the commutator?

If you remove the link across its small terminals, can you confirm the resistance from each of them to the case, the output terminal and the brush-holders (you will need to slip something under each brush to isolate them from the commutator for this test).

How much effort is needed to refit the machine to the engine and run it up for tests?

 

[Lucien Nunes]

After further consideration, there might also be a series winding in the machine that remains in circuit both when motoring and generating. Since its magnetic polarity depends on armature current direction which depends on torque direction, if it assists the shunt field while motoring it must oppose it while generating. Therefore it could serve as a cumulative compound motor for extra low-speed torque while starting, but a differential generator where the output voltage droops rapidly with increasing load current.

This characteristic is not normally useful in a generator, hence the use of a separate series field in the later dynastarts that is cut out of circuit when generating. However it might serve as a basic means of current limiting (although not voltage limiting) in this car if there is no other system of regulation. The trick in the design would have been in choosing the correct relative strengths of the two fields at typical system voltages and loads, to give a suitable charge rate under average conditions. It would approximate to a constant current and would not adapt according to load, so one could not really describe it as a method of regulation in the modern sense.

 

[Tony Hillyard]

After further consideration, there might also be a series winding in the machine that remains in circuit both when motoring and generating. Since its magnetic polarity depends on armature current direction which depends on torque direction, if it assists the shunt field while motoring it must oppose it while generating. Therefore it could serve as a cumulative compound motor for extra low-speed torque while starting, but a differential generator where the output voltage droops rapidly with increasing load current.

This characteristic is not normally useful in a generator, hence the use of a separate series field in the later dynastarts that is cut out of circuit when generating. However it might serve as a basic means of current limiting (although not voltage limiting) in this car if there is no other system of regulation. The trick in the design would have been in choosing the correct relative strengths of the two fields at typical system voltages and loads, to give a suitable charge rate under average conditions. It would approximate to a constant current and would not adapt according to load, so one could not really describe it as a method of regulation in the modern sense.

Thank you very much for taking so much trouble Lucien. Even I am starting to understand. In August I am due to have another look at my friend's Panhard, I will double check my readings and perhaps come back to you. I am starting to understand why Panhard went out of business. There seems to be a quirk in French culture, they seem to have an obsession in making everything overly complicated. The rest of mankind tries to simplify things, the French complicate. Very odd.