Handbrake - Part 2 - Installing a Linear Particle Accelerator

The normal handbrake set-up on the AK Cobra is a cable-operated system, utilising an XJS handbrake lever in the cockpit, operating a lever mounted above the differential unit that in turn pulls on the handbrake cables connected to each rear hub.

The original AK handbrake set-up, whereby the cable simply pulled directly on the actuator lever, did appear to have a reputation for not being very efficient (based on a read of several internet forums).  AK has addressed this and modified the set-up with the cable operating the lever via a pulley set-up to provide twice the pulling power.  Improved, but still a bit touch and go come IVA / MOT test time.

AK Handbrake Modification (from AK Build Manual)

I decided to make a couple of further modifications to the system myself to improve the handbrake performance.

The first modification involves the XJS handbrake lever.  I obtained the lever from Simply Performance at the same time as my donor axles.  The photos below show the lever before and after modification...

XJS Handbrake Lever before initial modification...

...and after modification!

The second modification involved the purchase of an electronic handbrake kit from Hollin Applications Ltd.  This kit was developed for the Motability market in the UK but seems to have gained popularity with many Cobra builders over recent years. The kit includes a linear actuator, an electronic controller and a simple switch.  The controller enables the pull / push force on the actuator to be adjusted up to a maximum of 800N or 80kg in old money.  It also meets the IVA requirement of preventing the handbrake from being released unless the ignition is switched on (it does also have the problem that the handbrake can't be released if the battery goes flat - but we will cross that bridge later).  The switch is a bit basic and will do for initial testing, but it will be replaced with something to match the other interior switchgear (when I decide what that will be...)

Linear Actuator

A bracket of some description is needed to mount the actuator to the rear chassis cross-member.  Since I made the decision to go with the Hollins kit, AK has actually started using them in their factory builds and has started selling an electronic handbrake kit including a mounting bracket.  However, I felt the price they were asking for the bracket alone was a bit steep and as I enjoy spending valuable time that I haven't got, making unnecessary bits for this build, I decided to make my own...

Fortunately, I got a bit of a headstart via Steve Sutton's build blog which referenced a solution by another builder Michael de Kok, who had included the details of the bracket he had fabricated for his own Cobra electronic handbrake install.  So, giving credit where it is due, I have borrowed the same design.

I completely forgot to take any photos of the fabrication process, so thankfully you can all just see the final bracket before and after powder coating!

Final bracket before coating (don't be too harsh on my welding)...

...and after powder coating

I fitted the handbrake actuator to the bracket using a long M6 bolt with a couple of spacers that I machined from some offcut of steel bar.

The actuator is installed into the bracket.

I then drilled and tapped some holes in the rear cross-member and fixed the bracket/actuator to the cross-member with some M8x1.25 bolts and spring washers.

The handbrake actuator & bracket are fixed to the rear cross-member.

I also needed to replace the operating lever from the item that AK supplied.  I fabricated a new lever from a 5mm thick steel plate with a small section of steel channel welded on the end.  The channel end needed to be reworked with some light grinder action to prevent the lever from fouling on the chassis at full throw.

New handbrake operating lever

I trial-assembled all the bits and wired up the control board temporarily to test out the operation.  Thankfully it all seemed to work OK with the actuator shutting down at extension once the load from the handbrake cables started coming on; the control box is preset from Hollins at 50kN load.

The final assembly involved powder-coating the operating lever, making up a couple of nylon spacer washers and bolting it all back together with copious amounts of copper grease.

Final handbrake assembly

Rear Axle Reassembly - Part 11 - Finally completed

Once my new half shaft spacers had arrived I could get on and (hopefully) complete the rear axle assembly.

Upon removing the spacers from the packaging, I was disappointed to find that they were both made from steel, and not some more exotic metal, as the price I paid for them might have suggested.

Could a golden spacer lie within...No!

I installed both spacers (4mm on offside / 7mm on nearside) and a single rear camber shim on each side initially.  It actually turned out that I needed just the single 4mm spacer on the offside and the 7mm spacer plus two shims on the nearside to get a camber setting of 0.3 degrees negative on both sides.

Spacer in place on differential output flange

Oh look - those shims do fit after all...

0.3 degrees negative on that side...

...and 0.3 degrees negative on the other side.  Job done!

With that done, I could remove all the 7/16" nuts from the half shafts for the last time and replace them with 7/16" Nylocs.  These were torqued up to 90Nm / 66lbf ft.

The next job was to remove the original drive nuts from the hub end of the half shafts and replace them with new items.  The Jaguar service manual recommends that the splined end of the half shaft within the rear hub is covered in thread lock over 30-50% of the radial area.  I used Loctite 270 and covered the rear part of the splined section before reassembly.  As well as a new drive nut I also replaced the conical washer with a new item.  

Today's thread lock is Loctite 270...

...applied over the rear of the splined section

New conical washer and drive nut (note the red insert)

The drive nuts need to be tightened up to a whopping 225lbf ft / 305Nm of torque.  I tightened them up initially using my air spanner.  I then used a large pry bar against the wheel studs and braced against the floor to stop the hub from rotating and dug out the largest of the torque wrenches from my tool arsenal.

Top tip - push the wrench down rather than trying to pull it up or side on otherwise you may end up pulling the chassis off the axle stands.  Also, try and position yourself away from the pry bar.  Mine ended up bending like a banana and if it were to break free from the wheel studs, it will cause serious damage!

Drive nut installed and tightened to ridiculous torque level!

The last step was to install the rear shock absorbers.  These are fitted in place with 7/16" x 4.5" bolts, M12 washers and 7/16" Nylocs in the top mounts and 7/16" x 2.5" bolts, M12 washers and 7/16" Nylocs in the bottom mounts.  AK only appear to supply a single M12 washer per bolt so I splashed out and added an extra washer to have one under the bolt head and one under the nut on all mounts.

Shiney new shock absorber - fitted so adjuster knob is at the bottom and facing inboard.

Mounting bolts - these were given a liberal smear of copper grease before installation

Rear Shock Absorber installed

The final step was to torque down the shock absorber mounting bolts to 38Nm (28 lbf ft) for the upper mounts and 64Nm (47lbf ft) for the lower mounts.  And that is the rear axle finally completed!

Rear Axle Reassembly - Part 10 - Shafts and Shims Shocker

 Finally, I am at the last stage of getting the rear axle/suspension back together and be warned this stage is a right PITA.

The first job on the list was to set the rear camber.  This requires setting the top most point of each of the rear hubs to be 150mm below the top of the rear chassis rail, checking the vertical angle of the face of the rear hubs and adjusting (by inserting shims between the differential output flange and the inboard half shaft flange) until the camber of the rear hub is between 0 and 0.5 degrees negative camber.

There now follows a moment of monumental stupidity which I am amazed I am prepared to admit to on such a globally viewed forum.

There are a couple of options for shimming out the half shafts on a Jaguar rear axle.

• Spacers of a specific thickness.  Jaguar used spacers of between 3.5 and 7.5mm thickness with Part Number CBC4806xx, where xx is the spacer thickness (e.g. 35 for the 3.5mm spacer).  Although these are only made out of steel, at the price they cost, you would think they were made out of gold!
• Rear camber shims with Part Number C16621#.  These are 0.020" (approx 0.5mm) thick and cost less than £1 each

I went with the second and cheaper option and ordered 16 shims from SNG Barratt hoping that would be a sufficient number (giving me up to 4mm of shim on each side).

16 Rear Camber Shims for less than £20...

I jacked up the first rear hub until it was 150mm below the top of the chassis rail.  I did this by clamping a spirit level to the top of the chassis rail and setting an adjustable set square on top, with the ruler set to give a depth of 150mm below the bottom of the spirit level.  The hub was then jacked up until it just touched the bottom of the ruler.

Setting height of hub to correct level

I then checked the vertical angle of the hub using a digital spirit level set vertically across the edges of the centre spigot on the hub.  The first reading was 89.25 degrees (i.e 0.75 degrees of negative camber), slightly too high, so some shimming was required.

I found an article on one of the online Jaguar forums that suggested that each 0.5mm shim would adjust the camber angle by around 0.25 degrees. So theoretically I only needed to add one shim.  In reality, I needed to add a few more as, without any shims in place, there is a small flange on the back of the inboard half shaft that bears onto the differential output shaft flange, such that at the point where the bolts pass through there is a gap between the two of around 3.5 to 4mm.  Until that gap is filled, the rear camber shims won't actually have any effect at all.

So I undid the nuts on the inboard half-shaft, which is a bit of a pain as you have to get it in exactly the right spot to get a 7/16" socket in through the U-joints and then you have to turn the differential by hand to line up each nut for removal (and of course repeat the process when you put the nuts back on).

With the half-shaft eased away from the differential flange bolts I could slide on a couple of shims, tighten it all back up and recheck the camber.  Except I couldn't because the hole pattern in my shims did not match the bolt pattern on my differential output flange; two of the holes matched up, but two were way out.

Cue much swearing...

In order not to waste the whole afternoon, I rummaged around in my box of leftover donor parts and found the two original (thick) half shaft spacers.  So I decided to install those just to try and get an idea of what thickness of shimming I was going to need.  After a frustrating and knuckle scraping afternoon of removing and reinstalling the half-shafts on both sides (several times), I had concluded that I was going to need around 4-4.5mm of shims on the offside and 7-7.5mm of shims on the nearside.

Later that afternoon I logged onto the SNG Barratt website to check out spacer options again.  This time I entered the VIN number for my donor vehicle and surprisingly the rear camber shims that I had already bought, did not come up as an option.  The only options were for the fixed-thickness spacers made of gold.  Clearly, I thought, the rear camber shims are for a different year model which has a different bolt pattern.

Annoyingly the spacers were also all on Special Order from SNG.  However, I found them in stock at Jaguar and Landrover Classic Parts.  I decided to order a 4mm and a 7mm spacer and then if necessary I could cut up the rear camber shims in such a way as to make one spacer out of two (or more) if additional thickness was needed.  BTW these two spacers cost over £100...

While I was waiting for the new spacers to arrive, I decided one evening to try and work out the best way to section up my original shims to try and make up a single shim from bits of others.  

It was then that my moment of stupidity hit me right between the eyes...

Why would they change the bolt pattern...

...Oh wait - they didn't...Doh!

Still...on the plus side, with needing nearly 12mm in total of shimming, I didn't have enough rear camber shims in any case plus its probably better to have a solid spacer rather than a large number of the thinner shims, particularly on the side needing nearly 8mm of shim (which would be 16 of the rear camber shims).

So maybe it has all worked out for the best!

Differential - Part 5 - We need to torque!

 There were a couple of small jobs that I needed to do to complete the installation of the rear differential.

The first was to cut down the 7/16UNF bolts securing the tie bars to the differential and the chassis.  The threaded length of these bolts is much greater than actually required and the protruding length looks a bit odd (to me anyway).

The second was to actually torque up all the various differential mounting bolts.  I didn't do this at the time of the original installation as, quite simply, I couldn't find the details for the necessary torque settings.

An offensive amount of bolt sticky-outedness...

I reckoned about 10mm off the end of the tie bar bolts should suffice.  Before cutting I wound a 7/16UNF die onto the bolt a) so that I could make sure the threads were intact after cutting and b) it made a handy brace to help support the bolts in the vice while cutting!

Die used to help keep bolt in place while cutting

I cut down the bolts with a hacksaw and then reinstalled them into the tie bar mounts, with a further liberal application of copper grease, adding a 7/16 washer on each end and 7/16UNF Nyloc nuts.  The final result was far more pleasing to my eye!

Much better - no unnecessary protrusion!

Now to finish tighten up all the differential mounting bolts.  You would have thought it would have been a relatively simple task to find all the necessary torque specifications, but oddly enough it took me a fair bit of searching before I was sure I had the right values.  This is complicated slightly by the fact that the AK mounting arrangement for the differential is of course not quite the same as the original Jaguar arrangement but my research was also hampered by the various Jaguar service manuals not calling any of the parts/bolt descriptions by anything remotely helpful!

I finally stumbled across a version of the Jaguar XJ40 Workshop Manual on the Jaguar UK forum.  This has a very handy series of diagrams at the front which show the various assemblies throughout the car and the necessary torque settings.  I almost missed this as I initially scrolled straight to the Final Drive Chapter (where of course everything was not called what I expected it to be).  Fortunately, I spotted this section as I was trying to refind the index!

The necessary specifications are as follows:

I was then able to finally tighten all the differential mounting bolts to the required specification and mark them as tightened with my favourite shade of blue nail varnish.

All torqued up and ready to go!

Rear Axle Reassembly - Part 9 - Hubs On....Finally!

Finally, the day has come when, having messed around for so long, I am hoping to get the rear hubs onto the car at last.  I had already purchased some of the new parts required for this momentous day from SNG Barratt many moons ago, as per the table below:

The first operation of the day was to secure the brake shoe mounting blocks to the backing plates using some M6x10 screws with spring washers.  I added a dobble of Loctite to these for good measure.

Brake shoe mounting block...mounted!

My new spacer tubes were inserted to place, the backing plate placed over the hub, and secured using new fixings all around.  Each plate needs two M10 screws and two M6 screws; the M10s come with thread lock compound already applied to the threads, I added some extra to the M6 screws.  These were tightened evenly using TPS45 and TPS25 bits until the backing plate was snug against the hub carrier.

Lower M10 Mounting Bolts with factory applied thread lock

I then spent some considerable time grappling with the installation of the handbrake shoes and springs (Handbrake Part 1) before it was time to reinstall the hubs.

These were given a liberal application of grease before being pushed firmly into place.  The hubs were then turned over and the ABS ring tapped onto the back of the hub using a large piece of timber as a suitable drift and a large hammer to provide the force!

Hub greased prior to insertion...

...ABS ring tapped firmly back into place...

...and one completed hub ready to go onto the car!

Finally, it was time to get the hubs on the car!

First step - install the hubs onto the lower wishbones.  This required the use of two new spacers per hub, which were installed on the face of each of the fulcrum bearings with a good smear of copper grease to hold them in place during installation.  I just ordered four new 3.955mm spacers (the same size as my donor spacers) since (according to the AK gospel of Jon Freeman) the shimming / preload of the lower fulcrum bearings is not important so long as the wishbone bracket is pulled tight against the hub.  As it was, the new spacers were just about the right thickness, and just needed a gentle tap with a soft mallet to ease the lower part of the hub into the wishbone bracket.  I gave all the contact surfaces a light smear of copper grease prior to installation.

The lower fulcrum bolt was given a very liberal application of copper grease, tapped gently through the lower wishbone mount, and secured with an M14 Nyloc and washer - just snugged into place for the moment.

The driveshafts were then installed onto the differential and held in place with plain 7/16 inch nuts.  I installed the driveshafts without any shims/spacers between then and the differential flange; the camber will be checked and the required shim thickness worked out next.

The drive shafts were then installed into the hub, which required a bit of manipulation to get the relative angles correct to allow the shaft to slide into the hub, before securing with the original cone washer and drive shaft nut.  The cone washer, drive nut, and differential flange nuts will all be replaced with new items once the camber has been set and final shims installed.

Hub and spacers tapped into lower wishbone mount

The last time I can say it - a heavily greased shaft!

Differential flange set up with no spacers/shims

Hub installed - it feels like a major milestone!

The final finishing touch was to make some plates to cover the hole for the ABS sensor in the top of the hub carriers.  Most people seem to leave these open but that just offends my sense of perfection!  

I made up a greasy finger paper template, stuck this to a piece of 2mm sheet steel, and cut/filed this down to the required profile.  The fixing hole locations were marked out and drilled with a 6mm drill.  The plates were of course treated to some candy red powder coating (as with all the other bits that won't be seen on the final car...).  I also cut out a couple of gaskets from rubber sheet, to match the outline of the plates, and then these were fixed in place with some stainless steel M6 button head screws with spring washers.

Greasy finger paper template

Powder-coated plates and rubber gaskets

Cover plate fixed in place

A very productive day - time for a well-earned beer me thinks!

Rear Axle Reassembly - Part 8 - Tubeway Army

 With my rubber gaskets sorted, it was time to get the brake back plates bolted onto the hub carriers. 

Although as I was mocking up the parts for reassembly, I noticed that the brake back plates are not particularly stiff where the handbrake cable passes through them.  The AK handbrake has come in for a bit of stick on many forums for its rather marginal performance.  My thought was that if the back plate flexes from the applied tension in the handbrake cable then this could be a factor in reducing the efficiency of the system.

The original Jaguar setup had a small spigot tube bolted to the back of the backing plate, through which the handbrake cable passed, and then a plastic clip between this tube and the hub carrier to hold the handbrake cable in place.  It is conceivable that this arrangement could offer some sort of limited bracing between the hub and the back plate (although that's possibly wishful thinking).  In any case, this option was not available to me as my original spigot tubes are now a fine lacework of rust and replacements are not available.

A small spot of tin worm...

My solution was to make a couple of spacer tubes to sit between the hub carrier and the backing plate that would serve to brace the backing plate and reduce any flex during application of the handbrake and also protect the exposed part of the handbrake cable from the elements.

This was an opportunity to press my "new" lathe into action.  This is a story in itself, but the short version is I foolishly put a bid on an old Myford ML7 lathe on the well-known auction site thinking that I would be outbid...and ended up winning the bid.  To be fair, it was in pretty good condition and came with lots of tooling, so it was a very reasonable (if unexpected) purchase.

I made some measurements and knocked up a quick CAD sketch of my intended solution, being a tube with a flange at each end to bear onto the hub carrier at one end and the handbrake mounting block at the other, with a small stub at each end to locate tube in position and a hole large enough to allow the clevis on the end of the handbrake cable to pass through.

Original Design Sketch

The spacers were machined from 25mm aluminium bar stock, faced and turned to size, a 12mm hole drilled down the middle, and finished off with a boring bar (twist drill bits do not produce a true circular hole).  I made the stubs at each end slightly longer than my original sketch (to facilitate machining) and I also machined a groove in the hub carrier end to allow the use of an O-ring to fully seal the tube to the hub carrier.

Aluminium bar after initial facing and turning - with tail support

Machined down for stub at one end

Location of flanges marked out

Spacer waisted out between flanges and larger stub formed

Drilling 12mm dia hole after 6mm pilot 

Completed Spacer Tube

Spacer in place between hub carrier and back plate

And to finish off this completely over-engineered component that will probably never be seen by human eyes again, I powder-coated it in the obligatory metallic red that I have chosen for all such parts on the car!

Further unnecessary bling!

Now I think the hubs can finally be fully reassembled.