question Ducellier 6 volt coil

[Pete Ashby]

I've just unpacked a 6 volt Ducellier coil and noticed the low tension terminals are marked Batt and Rup.....by default I can connect it the right way round as Batt is self explanatory. However I'm curious to know what RUP actually stands for I've tried looking up a French translation without any luck. I've come across + & - and SW & CB but never RUP any one know ?

 

Pete

[Adrian Barrell]

Rupteur. I typed contact breaker into Google translate!

[Pete Ashby]

Thank you Adrian,

 

mystery solved, my French /English school dictionary was challenged with regard to mechanical/electrical terms I tried things like earth or negative :rolleyes:

 

Pete

[Richard Farrant]

Hi Pete,

You now have to work out if it is a coil designed for negative or positive earth systems. There is a distinct difference.

[Pete Ashby]

Hi Pete,

You now have to work out if it is a coil designed for negative or positive earth systems. There is a distinct difference.

 

Ah yes indeed there is Richard, unhappy memories of burnt out replacement coils on BMC's back in the day :-( , I'm Ok with this one though checks out fine for - earth systems

 

Pete

[fv1609]

Pete but are you sure?

 

If you get it the wrong way round it will sort of work as you will get a spark either way round. But if you end up with a "positive spark" you will get poorer performance & more wear from the rotor arm.

 

If you have the wrong design of coil for the earth you are using & wire it up to get a "negative spark" you will have a reduced HT by about 600 volts. This is because the back EMF of about 300 volts from the primary as the points open adds to the HT. If it is the wrong design of coil despite arranging it to give a "negative spark" this 300 volts is of the opposite polarity to the HT so it subtracts 300 volts. So the net result is you are 600 volts of HT worse off using the wrong design of coil.

[Pete Ashby]

Yep sure thanks Clive, I use the analogue volt meter method between the plug and block and look for the direction of deflection, the other method with the lead pencil never works for me I just end up getting a belt and never manage to see the flare. I think for most applications on 12 volt systems the 10 to 15% loss of HT is not such a big deal but I fully agree with you on a 6 volt system you need every volt you can squeeze out of the coil on hot cranking.

 

Pete

[fv1609]

Yes very wise to keep away from the dreaded lead pencil :shake:

[Pete Ashby]

Yes very wise to keep away from the dreaded lead pencil :shake:

 

 

I think this method of looking for HT was invented by some sadist training officer :argh::argh::wow::wow::wow::wow::wow::wow: much safer with an old ministry Avo turned up to the highest range :-D

 

regards

 

pete