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We Have Ignition

Back in 2006, on the 14th of September to be precise, we officially sacked the Heritage Lottery Fund and took the crazy, brave, momentous decision to go it alone. They had dithered around for four years wanting to be a part of our project but forever trying to dilute it down so K7 would never live again. They were bureaucrats under the spell of museologists so the bureaucratic side said if we wanted their money we weren't allowed to touch the boat so as to keep the museolgists happy and if we did, the museologists would get their nether garments in disarray and all bets would be off. So we didn't touch the boat. We made the case that if something obvious was fizzing away before our very eyes we ought to intervene but that was about as far as we got so many of K7's innermost workings were still a mystery to us at that time. But once we had a free hand much was revealed and so when we found these curious little corroded cans buried in the hull we weren't long in working out that they must be the things that made the sparks to light the fire.

This is the right hand igniter still in situ, It's mounted in the side of the hull towards the back of the engine compressor and you can see how the mass of dissimilar metals has rotted holes all over the place. There's another identical unit on the opposite side.

We knew nothing about these but Clever Barry did. He explained how they are like the ignition coil in your car of old with points. A primary winding is energised to create a magnetic field in a secondary winding then the points open and the field collapses causing a big fat spark to leap out of the secondary coil to set fire to the fine kerosene mist flying about inside the engine. The points are then immediately re-energised and the cycle repeats to create a continuous spark and a gentle fizzing sound from both the igniter and the plug in the engine itself.

We opened them up and tipped out the insides.

See the adjuster nut at the top? That's for setting up the points gap.

We put a meter across the coils under Barry's direction and soon found that all the coils were knackered so we took them down to Barry who did likewise then calmly took a sharp chisel from a drawer and carved the old coils to bits. I wrote in the diary at the time that it looked like he'd scalped a ginger kid all over the floor but I couldn't write that nowadays as it's probably 'gingerist' or something. Having scalped away, Barry then lifted a rig down from a shelf with winding handles and clickety counters and announced he would make new coils. When I asked him how he knew how to do that he blamed it on a misspent youth. The mind boggles!

One thing he did say, however, was that he couldn't see how the cans themselves could be salvaged as they were full of holes. But that was the easy bit for me.

It involved some seriously fiddly welding.

The rot was cut out then the cans were pieced back together with tiny patches of 1mm steel.

It took a while and we didn't want the cans sanitised so the idea was only to remove the very worst of the rot.

But eventually we had two good cans.

Barry said they had been nickel plated originally and as it happened we had a convenient metal plating shop just around the corner so we asked nicely and soon both the cans, some other bits and bobs of recovered hardware and a few new parts Barry had made up, were plated and looking new whilst looking lived in.

Barry was delighted with them and wasted no time in reinstalling the newly made gubbins inside so we had functioning igniters again.

Gorgeous or what? He even salvaged the original, red outer sheathing from the wires and built new fittings for them. Now we could light the fire but that was a way off yet.

One argument we encountered many times, and another was why persist with this air start idea when you could convert to electric, was why not just put a pair of modern cracker boxes in there and be done with it?

The answer to both questions is firstly we wanted to fully understand the original systems rather than leave that knowledge to go extinct and secondly, we want the boat to have all the correct sounds as per 1967. Cracker boxes make fat, juicy sparks using capacitor discharge. Huge bolts of energy that keep the igniter plugs clean and make short work of lighting the fire but they also do what it says on the tin. Crack! Crack! Crack!

We use them on the test rig so you may have heard them there but on the boat we want the authentic fizzing sound that you can't actually hear unless you put your head to the side of the hull. But you would most definitely hear cracker boxes and that would be wrong.

So on we soldiered through all our boat building and engine testing until we found ourselves on the water in Bute in 2018.

Now we were off the test rig and using our rebuilt igniters. Our testing went very well as it had back at BBP HQ. We did a static engine run by the side of the loch then high speed taxi tests with both Stew and Ted at the controls. That all went very well too. Next we were going to try our first fast run and see if the old machine would get up and plane or if we would be plagued with Campbell-esque problems.

It was heart in the mouth time. We towed Ted out onto the loch on a beautiful calm late afternoon, double checked everything, positioned our safety and rescue boats then gave Ted the OK to start.

Air whooshed through the starter and the Orpheus spooled up but within seconds we knew it wasn't going to light then clouds of atomised fuel jetted out of the back of the engine and Ted released the starter. The engine whined to a standstill and we swarmed around the boat. It simply hadn't lit and we could detect no signs of life from the igniters. Damn and bugger!

We recovered to the boat shed and out came the screwdrivers. The engine cover was supposed to be fixed down with quarter turn spring fasteners but we didn't have time to do that before Bute and the engine cover didn't fit either, another job we hadn't got to yet; so we'd fired a load of Rivnuts into the holes in the hull and dogged the engine cover down with screws. It looked right from the outside but it made removing and refitting the engine cover a long and arduous task. And it had another gotcha because we hadn't been able to get a full complement of either 1/4 BSF or M6 screws, both of which looked correct, so it was a mix of both. Then add that you can start and M6 screw in s 1/4BSF thread and vice versa but you don't find out you've got it wrong until you're a few threads in, then add that we gave anyone with two hands a screwdriver that evening because we wanted to fix this and get back on the water before we lost the daylight.

It was fun to say the least. The diagnosis was a blown fuse and as both igniters run off the same fuse it had taken them both down. It would start on only one but we had nothing. The igniters fizzed at once with a new fuse and as our high speed taxi run quite deep in the water had resulted in massive water ingress it was put down to this so a good squirt with WD40 and the vexing comedy of 1/4BSF vs M6 was resumed in the opposite direction until we finally got waterborne again as dusk was falling.

This time the engine started to a cheer from the crowd and resulted in one of the most iconic pictures yet taken of K7. I have no idea who took it so whoever you are, the credit is duly yours.

Hot starts are bad. Flames coming from the jetpipe are bad. Higher than correct temperatures are very bad but it pleased the crowds and it does look impressive. From there the run went without a hitch until the canopy flew off at 120mph but that's another story.

That particular run was featured on the BBC One Show with our old mate Andy Kershaw.

But from then on the fuse problem recurred. It became routine to listen to the sides of the hull to make sure we had igniters before giving our pilots the green light. We'd done, and continued to do, everything we could think of to keep water out of the wiring but the fuse kept failing. Because of how the engine ingests air to cool the jetpipe it slurps spray under the covers through every opening so after each run it looked like someone had been under the engine cover with a pressure washer and that's not an exaggeration so we just assumed that our water ingress prevention measures still weren't adequate. We dried with towels, blew out with compressed air, sprayed with penetrating oil and wrapped endless wires in self-amalgamating tape but we couldn't get ahead of it.

It wasn't a showstopper but it was one more thing to think about and frustrating that all our efforts seemingly came to nought.

But then we got back to base, got everything dry as a bone and still we had fuse blowing trouble and then the igniter failed totally. We hadn't considered that it might be one unit causing the problem but the day we could get no life out of either of them and popped fuses the instant we hit the switch we tested them individually and discovered it was the right hand side one. It went back to Barry who declared the primary winding completely melted and blamed himself for perhaps including a tiny morsel of contamination in the winding that had caused a short circuit and gradual decay of his work until it failed totally. He made a new one and that seemed to fix things then we stripped K7 and packed all the bits and bobs away. We were locked down and beset with lawyer nonsense for a while after that but in mid 2022 we began putting things back together ahead of going to Elvington and guess what. Our igniters worked, and then they didn't and the primary coil melted into black goo once again. This was no piece of contamination in the winding, it was something we weren't understanding.

Barry took it on yet again and in discussion with Checkie, and by making up a new coil and testing it, they agreed between them that the fuse rating was too high so if the points stuck shut the resulting current passing through would soon cook the coils inside. That was remedied and the rebuilt igniter returned to the boat and was fitted with a lower rated fuse. We soon discovered that it would still blow the fuse but now it wouldn't destroy itself. We were beginning to close in on the problem. Sometimes the fuse would just blow and sometimes the igniter would start then stop again and the fuse would go then. Sometimes it would start and run interminably until we switched it off then on again and get one of its two other conditions but then it stopped and wouldn't restart and the fuse went in an instant. We took it apart and found the points welded together. The merest of touches caused them to spring open and off it went but that was definitely the cuplrit and why was only one igniter doing it. Once it got going the points were seen to be sparking and Barry considered the possibility that it might be the condenser put there to quench the sparks but it could be adjusted until there were no sparks at all yet it still ran.

We set it up on the boat so as to give it its proper power supply and left it fizzing away.

Notice the continuous spark. It would do this for ages then suddenly stop. Or just not start, but by now we understood that what had been happening all along was not water in the wiring or bits in the windings, it was unreliable points. But why just on the one igniter?

That seems to be down to the original repairs. As well as rewinding the coils, Barry replaced the points but no original parts were available so the replacements were made from donor magnetos or whatever could be found and Barry concluded in the end that whatever had been used on that particular igniter was different to what's on the other one and wasn't up to the job. He wanted to put platinum points in there and we'll certainly look at that in due course but, as I write, he has made up a new set of points from an aircraft part that's made of a much better alloy and not the 'rubbish Lucas mischief' that has been plaguing us all this time. He's confident that we now have the problem cracked so we'll soon find out.

But in the course of our recent recommissioning another gremlin crept in and this one was an even bigger puzzle on the face of it though much shorter lived.

To all appearances, the fuse for our LP boost pumps would mysteriously blow when no one was around, no one was using the pumps or anything else and no power was applied to anything. This was a real head-scratcher.

We'd switch the pumps on only to find them dead and an inspection would reveal a blown fuse, which, when replaced, would cure the problem and no amount of switching on and off would replicate the failure. When had the fuse blown then? We'd not run the pumps for days yet we'd come back to find it burned out. It was baffling.

Checkie and Jon experimented, we all looked at wiring schematics and no one could come up with a scenario that explained what was occurring. We discussed fitting test instrumentation to watch the fuse and wait for it to fail so we could investigate what was happening at the very moment but maybe it was simpler than that.

We went back to the pump design and wondered.

Kerosene is a hopeless lubricant so everything that relies on it for that purpose runs an incredibly thin film and close tolerances. The boost pumps are lubricated with kerosene and they're also submerged in the fuel tanks with their electrical parts in a sealed chamber. It would be bad if the kerosene was able to get up and into the chamber so there is a carbon/carbon seal on the shaft and its faces are pushed together with a spring.

This is the assembled pump.

The black cylinder and mesh screen part goes up inside the fuel tank with the motor in the black part. The green flange bolts up into a receiving flange in the tank. The impeller is inside the mesh screen and the big pipe fitting is where the fuel comes out. It's only a baby as these pumps go and moves a measly 200 gallons per hour. The one in our test rig is from a Lightning and moves 1000gph.

So we began asking questions.

Assuming that the fuse wasn't being popped by the ghost of Leo at three o'clock in the morning while we were all abed and it was a physical impossibility that any current was flowing then or any other time when we weren't there, when was it failing?

We concluded that perhaps if it failed without any sign that the pumps even tried it would create the impression that the fuse was already blown when in fact it actually happened the instant the switch was thrown. Next question - why then, would everything suddenly come back to life once a new fuse was fitted?

What if the pumps stuck a little if left standing but there was some imperceptible movement when the switch was flicked? Just a tiny shock to the moving parts. Not a quick enough reaction to save the fuse but enough to ensure that next time, with a new fuse, it all got going?

We only had this problem when the boat had been stood for a few days. Once working, the pumps could be switched on and off as often as you like. But leave them off for a few days and it looked to all intents and purposes that while we'd been away the fuse had mysteriously failed.

We considered the actual design of the pump and looked at its internals.

If you start at the impeller then look immediately below it on the motor shaft there's a sort of inverted mushroom shape and between that and the pump body is a thin black line. That's the carbon face seal to keep kero out of the motor chamber.

Here it is again. You can see the face seal has quite a footprint. The faces are pushed together by a spring and when it's running there's a film of kero between those faces but only a few molecules thick. Suppose, if left for a few days with a spring squeezing away at it, the film just oozed out and the faces stuck together. As soon as they moved all would be well but if the fuse went as they did they might have moved enough to work on the second attempt but not the first.

But why hadn't Campbell been afflicted with this? It might be argued that perhaps he had but it wasn't worth reporting but the answer is much simpler. K7 never had any fuses. We added those so the wiring might have warmed up for a moment but there was nothing to blow. Our wiring is a reverse-engineered perfect recreation of the original - except with fuses. Then the second pump was a bodge, a very late addition to try and solve a fuelling problem. They were on the wrong track and, though it did solve the problem for them, it wasn't because it was an extra pump but because the swirl pot allowed the bubbles to settle out of the fuel. They simply joined it into the wiring that fed the other pump so all the power to start two pumps from a dead stop has to come down one wire.

The final question, though. Why didn't we have this when we went to Bute? And that's an easy one too. During our lengthy and frustrating efforts to set up the engine in the hull with the throttle linkage woes and the reluctance of the engine to idle at the correct %RPM we decided at some point that maybe the LP boost pressure was having a hand in things and disconnected the swirl pot pump as a precaution. Our test rig only ran a single pump and we wondered if we had somehow set up the engine so it was happiest this way. Now we had a condition where if the seals caused stiction on starting the pump it might not be enough to blow the fuse. Later in the trip we reconnected the second pump and found it made no difference but why didn't the fuse go that time? Because the first pump was being used every day and wasn't going to stick. we postulated that you need both pumps standing unused for a few days before this happens.

So when we went to try the pumps on Friday to use some battery power to test the charging setup nothing happened. Absolutely nothing. right, gremlin, you're coming to Daddy, we decided, and left it all alone overnight to stick again. On Saturday we fitted a new fuse and threw the switch.

It was a slightly unrealistic test in that the fuse rating was a bit lower than the ones we have been running but the point was to prove that it would blow without any sign from the pumps that they had even tried and that certainly happened.

And the answer? Checkie is sending some slow-blow fuses. These will let some extra ergs and ohms down the pipe to hopefully kick the pumps over then let them settle down to a happy life. We will report in due course.


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Rhys Nolan
Rhys Nolan
Feb 12, 2023

So much attention to detail, I am seriously in awe.

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