sorry to pick your brains again my Triumph TRW Mk 3 has twin point/twin coils which hang just above the side valve head about 2" they seem very close and must get a lot of heat from the head does this cause problems thanks roger
Doesn't seem to matter Roger, I have coil ignition bikes where the coil is also mounted near the hottest part of the engine as standard, and my Willy's Jeep and Morris commercial actually have their coils mounted to the engine block and head. Ron
Oh yes it does, the resistance in a coil drops with temperature thus as it gets hot the resistane increased and it gets hotter! Modern coils are always bolted to a heat sink, Japanese bikes have a couple of bolts through the iron core to the frame, cars have them bolted to the inner wing, the coolest place under the bonnet. Your original coils are OK as long as there is some air getting around them but the older they get the hotter they get until one day they fail. And of course the better cooled they are the smaller they can be as seen on many mordern bikes.
Richard
Well I can't really comment about modern coils Richard.....Only the way that Triumph, BSA, Willys Overland and Morris Commercials made their millions of vehicles. Ron
It may be a case of relocating the coils to get the best operating conditions in the light of current thinking.....Another recent thread discusses the necessity of retro fitting fuses for example...
I moved the coils from under the tank of my Triumph T120R and relocated them to the toolbox...I also swapped the original twin coil set up for a more modern 'double ended' single coil....Ian
Just to clarify a few points, generally speaking ignition coils of yore were large and less efficent and therefore produce heat which needed dispursing, they were othen filled with oil to help this. Then they became a bit smaller (and cheaper) in a aluminium container, although more efficent and cooler running they required some external cooling from air flow, even under bonnet temperatures were still cooler then their core temp. Modern coils are much smaller (and cheaper still) and are more efficent things but they require a heat sink so are bolted to something cool, a body panel or bike frame. All these applications are fine when new but as electrical components age they become less efficent as they decay and resistance increases resulting in great heat production to the point they become unreliable. If this wasn't the case magnetos and dynamos would go on for ever. So, to go back to your original point, if you have an old vehicle with its original coil in place and it runs fine I'm pleased for you but there were many more whose coils have been replaced or they simply don't exist anymore. If you fit an NOS coil and it works I'm also pleased but many will have decayed to the point of unservicablity. If you fit a modern oil ensure it has a good heat sink, so bolting coils to the bottom of a nice cool petrol tank even in the rain isn't such a bad idea.
Richard
