A pair of Lucas windtone 9H horns was fitted to the Series 2 E-Type, one emitting a high tone and the other the low tone. The excitation of the air column is achieved by vibrating an internal metal diaphragm, with the frequency of vibration and the shape of the horn snail or trumpet determining the note produced.
The switching frequencies are carefully chosen to produce a major third musical interval (spanning 4 semi-tones). Together they set up beat frequencies producing a tremolo affect and a perceptibly louder sound. In the case of the 9H, the low tone switches at 392Hz and the high tone around 494Hz, producing a G and B respectively.
Great in theory, however both my horns were stamped with an ‘H’ on inside of the trumpet indicating they both produce the high tone. Well, they would, if they both worked! One of them only produced a sound for a split second before falling silent. The only recommended external adjustment that can be made is the contact breaker gap via a small screw.
Rather optimistically I thought it would be just a matter of readjusting the gap to get it working again. Alas, there was something more seriously wrong inside so only the good one was repainted at this stage.
One of the problems with the horns is the two halves are press riveted together. I’ve not been able to find anyone who supplies these rivets so, even if a repair is possible, it won’t be an ‘invisible’ repair.
I’m thinking of using something like Chicago screws but first I need to get inside to find out how it works and if it’s possible to change the frequency. It’s a voyage of discovery from here as I’ve not found any information on the horn innards.
The rivets were drilled and then punched out – the rivet inside the trumpet is slightly shorter than the others so I’ll have to remember that when ordering fixings to hold it back together. The two halves can then be carefully separated as the diaphragm was sandwiched between two thin, wax impregnated gaskets which are quite fragile.
| Drilling out the rivets | Horn carefully split in two | Metal diaphragm removed |
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The diaphragm was then removed to reveal the inner workings. Attached to the centre of the diaphragm is a ferrous cylinder so that its movement can be controlled by the rapid switching on and off of an electromagnet.
When current is applied, the ferrous cylinder and therefore the diaphragm is drawn towards the electromagnet. As the diaphragm nears the end of its travel, a disc around the ferrous cylinder hits the base plate of the contact breaker, opening the points. The electromagnetic field then collapses and the diaphragm returns to its natural position and the process is repeated.
The resistance of the contact points was around 7 ohms so a light rubbing with 400 grit wet and dry soon got this down to 0.8. Although I wouldn’t have thought this would stop the horn operating. I think the problem is with an external screw fitting which the service manual suggests should not be touched.
I’m fairly sure it has been adjusted at some stage as it’s screwed tight against the ferrous attachment. Therefore stopping any possible movement in the diaphragm.
Of the two external adjustments, the small screw adjusts the contact points gaps. The service manual states that this does not adjust the tone and is only to take up wear in the points. The central screw adjustment, with locking nut, only limits the length of travel permitted by the diaphragm so if it did effect the tone it would only be marginal (ie for fine tuning). I doubt it would give anywhere near the variation to recalibrate it to the low-tone.
Hmmmm …. stumped. Going back to first principles, due to the lack of tone adjustment in the electric components. The tone must be controlled mechanically but the spring rate of the diaphragm is fixed. Therefore the only two things that I can see that would effect the output tone are the mass of the ferrous diaphragm attachment, which would naturally impact the switching frequency, and the shape of the trumpet.
Neither of these two can be changed (easily) with the parts I have in front of me! I’ve found a restorer of old horns, Taff The Horns, who might have a non-working low-tone horn to provide a donor for a transplant. Otherwise plan B is to purchase a repro horn from Holdens for about £40!
A whole post on horns without a reference to a sketch by the late Peter Cook!!
I was surprising how much force was needed to loosen the nut. It was necessary put on full lock and then use an extension tube over the socket wrench handle to get enough leverage. 
At which point the key needs to be turned in the ignition to withdraw the steering lock. This enables the female inner column to be removed.
A couple of attempts still didn’t reveal an area of compression in the rubber …. more head scratching. It was definitely not the engine as this was almost entirely encased in Dynaliner. 
However this time, when the bonnet was raised to investigate, it revealed a 4-5 inch scrape in the paint on the air intake duct. Gutted. 
I had wrongly assumed that once the mounting brackets had been fitted to the engine, the weight would naturally align their bolt holes with the engine mounts fixed to the frames. After a considerable struggle, not dissimilar to the fitting of the rear suspension, everything was lined up and the front engine mounts could be secured.
I thought it would be easier to fit the central engine stabiliser once the engine was in place, as it’s one thing less to keep an eye on when the engine is lifted. It’s was fiddly job as there’s very little room between the engine and the bulkhead to get your fingers in. I think I’d prefit it next time.
The heater valve was another part that was difficult to remove, as the bulkhead heater pipe had seized solid into the valve body. I didn’t want to apply heat in case it damaged any internal rubber seals and so I tried to break the joint by rotating the valve body. All this achieved was to deform the pipe, which eventually had to be cut to remove the valve.
The rivet was drilled out and then it was fairly easy to split the valve in two by rotating the end cap. This revealed the cause of the weeping – a sprung rubber diaphragm, that is used to control the passage of water, had become furred up. 
Even after extensive internet searches, I haven’t been able to find a supplier that just supplies the internal rubber diaphragm. Unfortunately the options are very limited. 
The lock barrels are of the wafer tumbler design where five sprung loaded wafers protrude at the top of the barrel. They align with corresponding slots in the handle’s push button and stop the barrel from being rotated inside the push button. 
A spring is fitted to the inner end of the lock barrel which ensures it always returns to the aligned position, allowing the key to be removed. 
The fixing screw ensures that the ears of the plunger are positioned in line with the end section of the lock barrel (when the button is not pressed). 
A sprung linkage is attached between the operating lever and the locking lever of the latch mechanism, mounted below on the rear face of the door. Therefore the latch lever will either be pulled (unlocking) or pushed (locking), depending on the direction of rotation of the key. 
Other immediate issues were one of the alloy lock housings had broken around one of its mounting holes and the inner washer, inserted before the large spring, was missing.
Both locks had become clarted up with dirt and grease over the years. One so much so that it was difficult to rotate the key. 
The window regulators and door latches had come back from the platers looking almost like new. The interior space within the door will be subject to a lot more moisture than most of the other areas of the car, so these were given a coating of Dinitrol hard wax. 
The first was so weakened that it bent when the glass was removed. Fortunately replacements are available but as usual they’re a long way off the quality of the originals.
The first trial was to place the rubber in the channel and then trying to insert the glass. As there wasn’t any lubrication, this mainly compressed the rubber into the channel. The rubber had more of a tendency to push the glass out of the channel than hold it in place. 
Quite early on the radiator had been sent off to Northampton Autorads to be ‘re-cored’. It was then stored for a number of years as progress with the restoration ground to a halt. Partly due to lack of time but also a lack of enthusiasm once it became clear how much work was involved in a full restoration.
The only way I could get the switch’s plunger anywhere near to the ‘finger’ protrusion was to mount the switch to the bracket and then use two locking nuts to position the spring at the end of the switch – as shown in the photo.
My handbrake had been hacked about at some time in the past. The bracket attachment has been cut off and welded further back. 
