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Rubber coated wire


agg221

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A bit random this, but since the forum is a mine of information I wondered whether anyone may have ideas on a source.

 

When the Kelvin is running on petrol it uses a magneto to generate a spark. Once it is switched over to diesel the magneto is earthed out to protect it. There is a small brass stud on the top which the earth connects to. Mine currently has a piece of ordinary PVC coated earth wire to do this but I am making the correct part, courtesy of some dimensioned photographs of an original one. The wire should be a piece of flexible black rubber coated cable (NOT PVC coated). It is a lot easier to use a multi-strand, single core wire with a reasonable thickness of wire up it, rather than a spark plug HT lead with a single wire, as it needs the thickness to be connected to a screw terminal at one end and soldered to a ring tab at the other. It wants to be around 4-5mm OD on the insulation. I can find suitable wire, such as BS6195 4A in 4mm or 4C in 1.5-2.5mm which also has tinned strands which would help, and a couple of other options, but I can't find anyone that sells less than 100m, and I only need a couple of metres so it seems rather wasteful to throw over 95m of pristine wire in a skip.

 

Any ideas?


Alec

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The magneto stopping terminal is  a brass pin sticking up from a short piece of hex brass  bar with a female thread.  The OE magneto stopping lead has a wire spring clip at the loose end which pushes over the pin on the stopping terminal. The fixed end goes to the magneto- where depends on the magneto.

 There is a picture of the clip in the parts list, and I have a stopping terminal (but no clip),in the spares box if you you need a drawing.

 

What I would like to know is where on the engine the stopping terminal was originally  fitted.

 

N

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1 hour ago, philjw said:

This looks promising for an enquiry. It's the right type of material and the 1mm2 (or larger) could be the right diameter, depending on the thickness of the insulation. They don't actually list black on the website, or give the OD of the cable including insulation, but I can drop them a line.

 

1 hour ago, OldGoldy said:

 

Thanks - I'd found this one previously. Annoyingly, if they either had the 1mm in type 4C or the 2.5mm in type 4A it would be perfect but this particular one is a little on the thin side. It may yet be the best option.

 

55 minutes ago, Quattrodave said:

You can by HT (high tension) leads by the meter, ebay probably good for that.  You can defiantly buy the ends on ebay..

 

The problem with HT lead is that the copper core is very thin compared with the insulation. That makes it difficult to connect the ends, hence the use of what would, at the time, have been an LT lead.

 

27 minutes ago, BEngo said:

The magneto stopping terminal is  a brass pin sticking up from a short piece of hex brass  bar with a female thread.  The OE magneto stopping lead has a wire spring clip at the loose end which pushes over the pin on the stopping terminal. The fixed end goes to the magneto- where depends on the magneto.

 There is a picture of the clip in the parts list, and I have a stopping terminal (but no clip),in the spares box if you you need a drawing.

 

What I would like to know is where on the engine the stopping terminal was originally  fitted.

 

N

I have the stopping terminal still in place on my J2. Your description of the clip is similar but slightly different from Tom Cauldwell's original which I am copying. I have made the brass bit, will make the Ebonite bit on Tuesday and I have the necessary 2BA screw and the eye terminal. If I can find a suitable piece of wire it can be put in place next Saturday and I can take a photo to show where the stopping terminal is fitted.

 

Alec

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On 14/11/2021 at 18:18, BEngo said:

A photo would be very helpful.  Thank you.

 

N

Will do.

 

In the meantime, if you have access to your stopping terminal it would be very handy to know how long the central pin is so I can bore my clip to the appropriate depth.

 

Alec

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Interesting. Very neat. The parts list clip is just a lyre shaped piece of bent wire, presumably brass or bronze..  The version you have looks much more durable.  What did you make the black bit of the body from? 

 

N

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1 minute ago, BEngo said:

Interesting. Very neat. The parts list clip is just a lyre shaped piece of bent wire, presumably brass or bronze..  The version you have looks much more durable.  What did you make the black bit of the body from? 

 

N

The body is Ebonite, following the instructions of Dick Goble, who described the design from memory. Tom Cauldwell sent me some photos of an original one and between the two there was enough to go on. The big advantage of Ebonite is that it is electrically insulating, so you can put it down while starting on petrol without risking earthing out the magneto. I can imagine that this will be particularly useful for hand starting (when I get that sorted out).

 

Alec

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I may amuse myself by making one whilst I wait for the crankshaft to come back from being  ground  and reinstalled.  It appears to have got stuck iqn a queue behind the engine from a Rolls Royce Phantom  and the bottom end of a National, among other things.

I daresay black Delrin will be an OK substitute for ebonite.

N

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On 14/11/2021 at 18:18, BEngo said:

A photo would be very helpful.  Thank you.

 

N

As promised, photos showing where the stopping terminal goes. Hopefully these show what you need.

 

Alec

 

 

 

image1 (7).jpeg

 

image0 (12).jpg

Edited by agg221
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12 minutes ago, BEngo said:

Splendid, thank you.  I never thought it would be up there, heaven knows why not.

N

You're welcome.

 

One observation - the photographs were taken before a visit by Dick Goble, who pointed out that the earthing wire should run the other side of the exhaust, down nearer the spark plug wire, to avoid direct contact between the wire and the exhaust manifold to minimise heating. This has since been changed. The other end of the wire is a simple crimp on ring terminal. I did look at the solder-on brass HT lead terminals but they only seem to be available to suit the 7mm OD HT lead and this is 5mm.

 

Alec

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