Jan 202014

It was frustrating to have gone through the process of re-plating/re-chroming all the individual components and to have rebuilt the handbrake, only to find that the ratchet had been butchered to fit an incorrect cable. Rather dispirited, I decided to keep the rebuilt handbrake as is and reuse the offending cable.

I’d hoped that it would be possible to rig up an alternative method of mounting the handbrake switch. However I wasn’t able to come up with a solution that I was happy with. Plus I’d found a number of forum postings of issues setting up the handbrake mechanism even with the correct, unmolested parts.

Old & New Clevises Correct cable is shorter

The existing cable was either incorrect for the car or a poor reproduction part. Both of its clevises were far too long, resulting in an inner cable length that was over 1/2″ too long.

I’m fairly sure that a previous owner/garage had relocated the cable abutment on the ratchet about 1″ rearward as a bodge to compensate for the oversized clevis.

The knock-on effect is the distance between the outer cable abutment on the ratchet and that at the handbrake compensator mechanism on the IRS has been reduced by the same amount. Squeezing the outer cable into this shorter distance effectively reduces the overall inner cable length by 1″ – so a net shortening of approx. 1/2″.

The handbrake compensator offers some adjustment to cater for stretching of the cable over time. Even so, 1/2″ would almost certainly put it at the limit of its adjustability. I’d probably be on a losing wicket trying to get it to work correctly. It was better to bite the bullet now rather than later. So a correct cable was obtained from the Jaguar Enthusiast Club, who now offered them via their online shop.

RM & J Smith were able to supply new ratchets which came as a relief, so it wasn’t necessary to buy a complete new handbrake. The only obvious difference is the pivot bolt spacers are welded to the replacement ratchets.

The fitting of the new ratchet was a simple task but the completion of the handbrake was foiled yet again. The bore of the outer cable abutment was 1/32″ smaller than the 3/8″ cable diameter. It has a slot machined into its circumference and is designed to allow a slight expansion, so I didn’t think anything was amiss.

The bolt securing the switch bracket then clamps the abutment onto the outer cable.

The only way I could get the outer cable into the hole was by continually twisting and pushing it. It didn’t feel right the more I progressed. Considerable effort had been needed just to get the cable half way home. So I decided to remove it and have a re-think. It might be possible to re-drill the bore although I was concerned the slot might cause problems.

I needn’t have worried. As soon as the cable was twisted in the reverse direction, disaster struck …. one half of the abutment fitting snapped clean off.

Aaaaargh and much cursing of repro parts!! Another case of what I now refer to as the Restoration March …. 1 step forward, several back!!

Looking at the fracture, it appears that the whole ratchet is hardened during the manufacturing process, presumably to provide the necessary hardness in the ratchet teeth. The downside, as I found out, is it makes the part brittle and prone to stress fractures. Not ideal for clamping parts which need a degree of ductility, such as the cable abutment.

RM & J Smith have been an excellent source of difficult to find parts and, to their credit, were very good, offering to send out a replacement immediately free of charge. They had identified the problem with the size of the hole and returned the ratchets to their manufacturer to be corrected. I had received one that slipped through the net. The following day the replacement arrived and it fits perfectly.

Getting the warning light switch properly set up proved to be much trickier than I’d anticipated and quite frustrating. The switch is activated by a ‘S’ shaped spring striker. When the handbrake is fully released the protrusion at the base of the lever presses against the striker, which in turn depresses the switch.

The main problem was mounting everything far enough forward so there was sufficient pressure on the striker to operate the switch.

Both the switch and striker are mounted to the bracket by two locking half nuts. So there is very little fore and aft adjustment that can be made. Mounting the switch progressively nearer to the striker starts to pre-engage the switches’ plunger, making the switching more hairpin-like until ultimately it’s permanently on.

I finally got it set up and working on the bench although I still wasn’t 100% happy. The switch had to be angled slightly and the warning light would be on as soon as the lever was moved off the end tooth of the ratchet. The plan was to mount the pre-built handbrake and switch but much to my dismay, I’d completely missed that fact that the cable has to be fed forward into the cabin through a guide bracket in the transmission tunnel.

All the set up was then lost, as the handbrake switch needed to be removed to free the cable. In situ, it wasn’t possible to reproduce as good a set up as before because the floor pan was stopping the angling of the switch. I found the best fit to mount the ‘S’ shaped striker horizontally.

I’m tempted to add some packing washers between the striker and bracket to allow the switch to be moved forward slightly. I think I’m going to leave the fitting the central console until after its first MOT so I’ll still have access to the handbrake.

Jan 162014

There’s been a dramatic drop off in progress with the restoration in the last month or so. Partly due to the horrible winter weather, resulting in an apathy to venture out into a cold, dark garage!

In the meantime, attention has turned to sorting out bits and pieces that could be worked on indoors, although it gives an excuse for the gratuitous inclusion of some photos of the main reason for the lack of headway … a diving trip in warmer climes!

Progress is delayed due to a spot of diving …. with some immature 6m Whale Sharks

Back to the plot …..

Several years ago I’d come across an owner’s restoration of a ’63 OTS where they had redesigned the looms to their own specification, incorporating relays for the headlight circuits. The addition of relays made good sense, as they remove the main current bearing wires from behind the dash area, but I wasn’t convinced about having bespoke wiring looms made.

Deviating too far from the original wiring looms would mean that, if I subsequently encountered electrical problems, I’d be on my own as it would be hard seeking accurate advice from fellow owners. There was also the fear of overlooking a critical wire when the looms were made up or getting the length of one of the wires slightly wrong. It would be an expensive mistake to fix!

So the idea of adding relays was shelved and a new set of standard looms purchased. Fortunately this proved to be the right course of action. At the time, I hadn’t spotted the wiring diagrams I was using weren’t correct for my car. They didn’t have the changes in circuitry covering the introduction of the ballast resistor into the ignition circuit.

Rather timely, as I was starting to look at the lighting and bonnet electrics, an excellent write up of a headlamp relay modification was covered on the E-Type forum. The installation is very discreet with the relays being mounted out of sight behind the LHS ‘sugar scoop’. The only visible sign of the modification is the main power feed, taken from the alternator B+ terminal.

The downside of tucking the modifications within the bonnet is that it will be much trickier to maintain if something fails. The headlight bowls and possibly the indicators would need to be removed to gain access.

I had some spare repro 6RA relays so all I needed to purchase were some suitable coloured & rated wires and two in-line fuses. I also decided to install Halogen headlights at the same time.

The circuit diagram shows the planned wiring modifications, with the additional components labelled in red.

There are two spare terminals in the 8-pin bonnet plug, which were originally for the bonnet mounted horns found in the earlier cars and, I believe, the provision for optional extra spot/driving lights.

One of these spare terminals was used for the single high load wire running from the alternator B+ terminal to the 10-way connector in the bonnet. (It’s much easier to take a supply from the B+ post rather than travelling all the way back to the battery.)

I managed to feed the wire into the PVC sleeving to the bonnet plug so the only visible sign of the installation in the engine bay is a single sheathed wire running from the alternator to the bottom left of the picture frame, which has been cable tied to the existing loom.

From the bonnet connector, this feed splits in two to provide the 12v supplies to the dipped and the main beam relays. The relays have a double spaded terminal for the switched output, so the wires to the left and right hand lamps were connected directly to the relay.

Wire and fuse ratings
The Halogen dual filament bulbs are rated as 55W/65W at 12v so the dipped and main beams for each bulb will draw around 5.5 amps and 6.5 amps respectively (assuming a charging battery voltage of 14.3V).

Normally only one set of the filaments are on at any one time. However the worst case is when the main beam is ‘flashed’ while the dipped beams are on. Even though this should only be for short periods of time, I thought it prudent to assume the maximum current required for both headlamps would be 24 amps (2 dipped @ 5.5A each and 2 main beam @ 6.5A each).

Therefore 44/0.30 cable, rated at 25 amps, has been used for the supply from the alternator rather than the 28/0.30 cable suggested in the forum write up. Inline fuses have been used for the connections to the two relays. Their wiring is rated at 30 amps which is more than enough, although they have both been fitted with 15 amp fuses as the expected loads are 11 amps dipped and 13 amps main beam.

Using two fuses should ensure that a blown fuse won’t result in the complete loss of lighting!

The original wiring for the dipped beam (Blue/Red) and main beam (Blue/White) will now just be used to switch the relays. The coil resistance for the 6RA relays was measured at approximately 83 ohms so the switching wires will now only need to carry around 0.17 amps. Therefore the dash mounted fuses 1 & 2 have also been replaced, by 0.25 amp fuses.

As the whole bonnet area had been coated in copious amounts of Waxoyl, I also fitted some PVC sheathing to the bonnet loom in an attempt to keep it clean. I just need to tidy up the cabling when the headlamps are fitted.