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Rick Site Admin
Joined: 27 Apr 2005 Posts: 22477 Location: UK
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Posted: Mon Sep 10, 2012 7:03 pm Post subject: Dickey coil... |
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As I've referred to in the past, recent expeditions in the truck have usually ended in problems due to the engine cutting out. It seemed to be temp related. Condenser was swapped out, as were points, and many things fuel-related looked at.
Last time, I noticed that the coil (6v elecs) was very very warm, not quite hot but much warmer than I'd expected after 10 mins running in the drive, and a 1/4 mile trip down the road.
Over the weekend I took a closer look at the coil - a NOS 1940s/1950s item - with a view to replacing it with another NOS item from the states.
Unscrewing the HT connector, I noticed that only a tiny amount of copper core was poking through to make the contact (as in the photo below). Sliding off the connector revealed that when the cable insulation had been stripped back, half the core had been taken away with the strippers at the same time. As you can see, only a few strands of copper were getting close to the connector in the coil itself.
I removed the coil and had a peer inside. The lead connector screws in down a brass threaded section, enabling the end of the connector to bear on a flat metal circular connection in the coil. Instead of being flat, the coil connection's surface is all pitted with a raised pip in the centre, and pock-marks and pits all over the place, leaving it very rough when compared to the flat surface in the new coil.
My guess is that the HT lead was incorrectly stripped, leaving just a few strands of copper poking out of the screw-in connector. The connection was therefore pretty poor, leading to the spark having to jump from cable to coil, causing the coil to warm up and the contact surface (and probably the copper strands in the lead) to break down. It may also lead to the coil warming up far more than seems correct, ultimately causing it to pack up until it has cooled down again.
Does this theory sound feasible?
thanks, RJ _________________ Rick - Admin
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Bitumen Boy
Joined: 26 Jan 2012 Posts: 1740 Location: Above the snow line in old Monmouthshire
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Posted: Mon Sep 10, 2012 9:34 pm Post subject: |
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Sounds reasonable to me, and in any case it's an obvious fault to be corrected. I'd say a rocket is in order for whoever made up the leads - I'm guessing you're not running the ones that were on the truck when you bought it..? |
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47p2
Joined: 24 Nov 2007 Posts: 2009 Location: Glasgow
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Posted: Tue Sep 11, 2012 9:24 am Post subject: |
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There should be a small split brass washer on the end of the wire
The wire should be stripped back then fed through the washer and evenly spread around the washer. This ensures the wire does not come loose whilst driving, it also ensures a good contact is made between the two components
_________________ ROVER
One of Britain's Fine Cars |
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Rick Site Admin
Joined: 27 Apr 2005 Posts: 22477 Location: UK
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Rick Site Admin
Joined: 27 Apr 2005 Posts: 22477 Location: UK
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Bitumen Boy
Joined: 26 Jan 2012 Posts: 1740 Location: Above the snow line in old Monmouthshire
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Posted: Tue Sep 11, 2012 1:12 pm Post subject: |
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Rick wrote: | Bitumen Boy wrote: | Sounds reasonable to me, and in any case it's an obvious fault to be corrected. I'd say a rocket is in order for whoever made up the leads - I'm guessing you're not running the ones that were on the truck when you bought it..? |
This was put on by the people who restored the truck..
RJ |
Thought as much, somehow... hopefully no other surprises are in store for you courtesy of their quality workmanship
I'm sure the split washers are still available to buy if you haven't any to hand, might save you some time over making your own if the size is right. |
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ukdave2002
Joined: 23 Nov 2007 Posts: 4127 Location: South Cheshire
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Posted: Tue Sep 11, 2012 1:23 pm Post subject: |
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Hi Rick
A couple of points:
1) When the points open, the secondary voltage in the coil rises until the spark plug fires, the bigger the plug gap the more the voltage will have to rise. If there is an air-gap in the HT leads and this requires a voltage greater than than the plug voltage to "jump" the gap; the coil will be working a bit harder. Adding an air gap in the HT is an old trick that can help fire fouled plugs. The gap can be much bigger than a plug gap that's working under pressure (compression)
2) If this air gap is the root cause of the fault, I'd still keep an eye on the original coil, it could either have poor insulation or an intermittent dis, either way it may not be reliable if it has broken down with moderate heat.
3)The air gap also means the HT cable and coil connector will be eroding in the same way that plugs erode.
I have a bag of new split washers if you need one.
Dave |
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Rick Site Admin
Joined: 27 Apr 2005 Posts: 22477 Location: UK
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PAUL BEAUMONT
Joined: 27 Nov 2007 Posts: 1281 Location: Barnsley S. Yorks
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Posted: Tue Sep 18, 2012 1:15 pm Post subject: |
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Green Spark Plug supply the split washers! though postage is probably more thabn the part - mid you they are in Rick's part of the world!! |
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Rick Site Admin
Joined: 27 Apr 2005 Posts: 22477 Location: UK
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Bitumen Boy
Joined: 26 Jan 2012 Posts: 1740 Location: Above the snow line in old Monmouthshire
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Posted: Tue Sep 18, 2012 7:09 pm Post subject: |
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Rick wrote: | I had a look at the coil the other day, and it doesn't have sufficient space for the usual type of split washer (I found my stash btw), so whether these US coils had a different type, or none at all, I'm not entirely sure...
RJ |
Is the issue with the thickness or the diameter of the washer(s) you have? Perhaps US ones are just a different size - be too simple otherwise...
Unless, looking again at your first photo, the idea is that the copper cores are folded back on themselves around the outside of that screw connector, and the connection is made on the unthreaded section at the bottom, maybe fitting into a taper of some kind in the coil itself. I wonder if there are any US based forums that might be able to give you some pointers? |
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Penman
Joined: 23 Nov 2007 Posts: 4766 Location: Swindon, Wilts.
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Posted: Tue Sep 18, 2012 7:55 pm Post subject: |
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Hi
It does look as if BB has an answer there.
With the old UK type the threaded bit was a loose sleeve and the washer did trap the wires, but even if you had smaller washers there wouldn't be a good area under that metal tube to get a really good contact area.
Is it possible to get a picture of the internals of the coil terminal point?
perhaps mic-ing up the bottom of the external bit and the bottom of the receiving terminal could show if there is a difference.
One of these would help, but you might need a longer internal measurement side
_________________ Bristols should always come in pairs.
Any 2 from:-
Straight 6
V8 V10 |
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47Jag
Joined: 26 Jun 2008 Posts: 1480 Location: Bothwell, Scotland
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Posted: Tue Sep 18, 2012 9:01 pm Post subject: |
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Rick,
I just had another look at your original post and it occurs to me that on the Lucas washer idea, the wire is bent 90 degrees. On your veriion I reckon the wire should be bent back 180 degrees to just before the threads start and the centre part of the coil would push against this locking the cable. How loose is the cable in the screw fitting? Could it have worked it's way away from the coil centre? I thought you hadposted a pic. looking into the coil and as I recall it looked burned.
Art |
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NONORT
Joined: 26 Apr 2012 Posts: 55 Location: Southampton
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Posted: Tue Sep 18, 2012 10:55 pm Post subject: |
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Hi Rick, On the old Rolls that I work on the split washer is done away with and the the HT cable is cut to extend through the insulated fitting and then peeled back like a banana skin. You will notice the end of the fitting allows for this by being smaller than the core diameter of the thread. Hope this helps. |
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Peter_L
Joined: 10 Apr 2008 Posts: 2680 Location: New Brunswick. Canada.
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Posted: Thu Sep 20, 2012 3:14 pm Post subject: |
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I notice that there is an inside (female) taper at the end of the brass bit.
Assuming that it is there for a purpose and not just decoration, would it make sense that the coil would have a simliar (male) protrudance that would clamp the HT wires when the connector is screwed in.
Having the strands folded back would allow the copper strands to be clamped but I doubt that a secure connection could be made on the just the vertical sides as there is no applied pressure.
Could there have even been another piece to this puzzle, a brass insert with a male taper at one end and a flat surface at the other. When screwed into place the strands would remain stationary and not dragged around as the connector is screwed home tight.
That connector is a serious piece of engineering and I would have thought that the same amount of thought would have been applied to the electrical connection.
Rick: Is there a manufacturers name on the coil (s) and is either of them original equipment. |
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