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

Body Preparation - Part 2 - Pedal to the Metal

AK recommends fitting the pedal box to the body before installing the body on the chassis.  Most builder's blogs also suggest that installing the brake servo and master cylinder is a much easier job if done with the body off the car.  So that was my next job!

I obtained my brake servo unit, from a Rover 200, via that renowned internet auction site.  When I was looking for this, there seemed to be none available in the UK and I ended up having mine shipped from Lithuania!

My unit arrived looking in not too bad a condition.  Importantly it also came with the grommet and the spigot for attaching the engine vacuum line.  I gave it a quick scuff-up with a scotchbrite pad, masked up the bolt threads and bellows and applied a couple of coats of primer, followed by some matt black spray paint.

The servo unit was given some gentle abrasion...

...followed by a couple of coats of primer...

...and some black spray paint

Looking almost as good as new!

The master cylinder from a Rover 25 or Rover 200 is also needed.  However, as I had opted for the big brake upgrade kit I needed to also upgrade the master cylinder.  

This got a bit confusing for a while as I really struggled to find the right part.  AK suggested that the required bore of the master cylinder was 22.7mm as opposed to the standard Rover 25/200 component, which has a 22.2mm bore. This meant that I needed to search for a master cylinder from a Rover 220 Turbo model, which according to Jon at AK is easily identifiable as the brake pipe outlets on the master cylinder point to the outside of the car as opposed to pointing toward the engine bay.

I completely failed to find any Rover master cylinders with a bore of anything other than 22.2mm and the majority seemed to have the outlets facing the engine.  In the end, I bought a brand new unit from TRW, which had the outlets on the correct side, but still had a bore of 22.2mm; so fingers crossed it works!

New master cylinder unit - bore 22.2mm

The master cylinder was bolted to the servo unit using some M8 Nyloc bolts, remembering to install the rubber O-ring between the master cylinder and the servo.

Servo and master cylinder

In hindsight, it might have been easier to install the servo into the engine bay and then bolt the master cylinder on.  There is not a lot of space between the pedal box firewall and the inner wheel arch.  It required a lot of careful jiggling around, taking care not to scratch the stainless steel engine bay cladding before I managed to get the servo and master cylinder in place.

In place - and it's not coming out again!

I'm running a 'Drive by Wire' (DBW) throttle set-up so I needed to drop the GM DBW throttle pedal (which includes the position sensor and electrical connector) off with AK so they could modify their normal pedal box and install the new pedal.

Modified Pedal Box with DWB Throttle Pedal

I had hoped that I could use the studs from the brake servo to 'hang' the pedal box off while installing it to make life a bit easier.  Unfortunately, the weight of the box and its centre of gravity conspired against me.  So installation of the pedal box is definitely a two-person job.

The pedal box is secured to the firewall with M8 bolts.  I bought some stainless steel Allen-head bolts, which as they will be visible in the engine bay, I treated to a bit of an extra polish to match the shiny engine bay cladding.

Shiny!

With me standing in the engine bay, trying to hold the pedal box against the firewall with my fingers through the hole for the clutch master cylinder and holding an Allen key into each of the bolts, and with my son lying in the driver's footwell with a socket and extension bar, we did manage to get the pedal box installed into place and secure the brake servo in place.  It is impossible to get a socket onto the upper bolts, so we had to resort to a spanner for those.  

While my son was trapped in the footwell I also took the opportunity to install the clutch master cylinder.  I bought a Girling unit with a 0.75" bore from Car Builder Solutions.  Again this was installed using 2No. shiny 8mm Allen-head bolts. 

Another "easy" job completed...

...and as seen from the inside!

And with that done, I am one step closer to getting the body on! 

Steering Part 2 - Power (Steering) Struggles

So my power steering issues still need to be fully resolved...

With my pump issues sorted (See Engine & Gearbox Installation - Part 6) all I needed was to connect up the pump reservoir and hoses and all would be good.

Haha...

Having bought the billet ancillaries bracket from Kyle at LSX Performance I knew that I wouldn't be able to use the standard LS Power Steering reservoir which, as I understand it, slots into the standard Chevy ancillary bracketry.  Kyle did supply me with an alloy tank to suit the kit he had provided, but in the end, I decided there were a couple of issues with it.  

Firstly, the low-pressure spigot on the tank was far too small for the AK-supplied hose and I was worried that I would not be able to get a tight enough seal with a jubilee clip (the AK hose is also braided which restricts the ability of the hose to crush down small enough).

The second issue was that with my shiny header tank and washer tank, the alloy version just didn't really meet my required "bling" standards.

It's good - but not good enough...

This led me to design my own version of the reservoir which utilised some AN-style fittings that would match the size of the low-pressure hose and the inlet port on my power steering pump.

CAD Design for new reservoir...

...using -AN weld-on fittings

I rang around a couple of companies to get a quote for making up my design in polished stainless steel.  I ended up going to XCS Designs, perhaps better known for their own Cobra kits, who are just up the road from me.  Scott, their Workshop Manager, gave me a pretty reasonable quote on the basis that I provided the AN fittings and a weld-on filler neck (which I obtained from that well-known auction site).

My only real issue with that decision was that XCS was going through a particularly busy period (which is good for them) and I had to wait several weeks before my reservoir was ready.  But I think it was well worth the wait!

New shiny reservoir!

Once I had picked up the tank and was ready to install it, I realised that sometimes it pays to just take a little more time planning and thinking things through fully...

The first issue was that on my original tank, the output spigot at the rear was installed right at the bottom of the tank.  In my new design, with the weld-on -10AN fitting, it now sat slightly higher up on the rear of the tank.  This meant that the collar of the AN fitting just clashed with the billet ancillary bracket and prevented the tank from sitting flush against the bracket...

Original tank outlet - at very bottom of the tank...

With weld-on AN fitting, the outlet sits higher on the rear of the tank...

...resulting in the collar of the weld-on fitting clashing with the ancillary bracket

The second issue was that, despite measuring several times, the holes on the new tank did not quite align with the bolt holes on the ancillary bracket.  Comparing the hole positions with the original tank showed them to be quite a way off.  Again, a stark reminder to plan properly and keep checking everything several times and then check again...

The second issue was actually relatively easy to resolve simply by drilling out the mounting holes on the new tank from 10mm to 12mm diameter with a hole drill.  This gave enough wriggle room to get the bolts through the mounting tabs and into the holes on the ancillary bracket.  The added bonus was that by allowing the position of the tank to shift slightly, also solved the first issue above, and the tank now could sit flush against the ancillary bracket.

However, the third issue then identified itself.  I bought a 90-degree -10AN fitting to attach to the rear of the tank and then connect to the -10AN fitting on the inlet of the power steering pump.  However I had failed to consider the dimensions of the -10AN fitting on the back of the tank, and with this installed, there was insufficient space between the front and rear of the ancillary bracket to allow the tank to sit flush as intended.

AN fitting hard against the bracket preventing the tank from sitting flush

This was not a major deal (although it was annoying) as I was able to turn up a couple of 12mm thick spacers from some 20mm diameter aluminium bar with a 10mm diameter hole drilled through the middle.  I also had to buy a couple of slightly longer 10mm diameter bolts to account for the additional thickness of the spacers.

Finally, I could get the tank mounted and the -10AN fitting and braided line routed down towards the pump inlet fitting.

Spacers provide clearance for the rear -10AN fitting

Tank in place and in need of a polish!

I used a 150 degree -10AN fitting to connect the hose to the steering pump inlet.  I originally bought a 180-degree fitting, but the -10 braided hose is not very flexible and I couldn't get the hose to align with the fitting.

150 degree -10AN fitting to align with hose orientation

I needed to angle the hose ends to align with the fitting orientations

Bottom fitting installed

The final fitting of the hose was a bit of a wrestling match.  The short -10 hose had zero flexibility and the only way I could get both ends onto the fittings was to take the reservoir off again, fit the hose to the reservoir and then try and connect the bottom fitting.  Once the hose was secured at both ends, I needed three hands to try and wiggle the reservoir back into place and get the fixing bolts and spacers installed.  It was a great relief when everything was finally in place and all bolts and fittings tightened!

The final connection to the reservoir was the low-pressure line return line from the steering rack.  This is another braided line supplied by AK.  It is installed to the steering rack with a banjo fitting and then routed up to the reservoir.  I used a 60-degree -8AN fitting to connect the hose to the reservoir.

Low-pressure return line from Steering Rack completed

Now all I need to do is get a new high-pressure hose made up with a -6AN fitting on the pump end and this job will finally be done!!!

Body Preparation - Part 1

A few small jobs need to be tackled before the body can be fitted onto the chassis, so I decided to get on with those while finishing off the rolling chassis.

The first thing I dealt with was the gaps between the rear inner wheel arches and the body.  These are not fully bonded/sealed and as supplied provide a fantastic path for water thrown up from the rear wheels to find its way straight into the boot.

Gaps around the rear off-side wheel arch...

...and even bigger gaps on the near-side rear arch

At first, I thought that AK Sportscars had forgotten to fully fibreglass the arches in before sending my body to me and I intended to bond in a couple of layers of glass-fibre mat to cover the gaps.  However, I discovered after watching Russ Howell's video series on building an AK Cobra that this is not recommended by AK as this leads to a stress concentration and can cause the paint on top of the wheel arches to crack.  The recommended solution is using "Tiger Seal" (a polyurethane sealant) to fill these gaps.

The gap on the near-side arch was too big to try and fill so I used a cardboard template to cover the gap from the boot side of the arch and give some backing for the sealant to stick to.  I did two sealant applications; the second was to fill any bits that I had missed the first time and give a thicker bead just to be on the safe side.  I also ran a thin bead around the front wheel arches.  Although any water thrown up would only pass into the engine bay and not the passenger compartment, I still felt it was a prudent step to take.

No tigers were harmed in the making of this sealant...

Cardboard template on boot side of near-side arch

First pass sealant application

After the second pass of sealant

I then gave the wheel arches a couple of coats of fibreglass primer which I bought from Black Country Paints.  I applied this with a brush (several brushes actually).  I also gave the inside of the nose cone and the tops of the front wheel arches inside the engine bay a couple of coats of primer as well.

Front wheel arch after the first coat of primer...

...and after the second coat.

Inside nose cone after first coat of primer

Then armed with several aerosol cans (I think I went through about 12 cans in total) from Halfords, I gave all the primed areas 3-4 coats of gloss black paint.

...Inside nose cone...

...Inside Engine Bay...

...and Rear Wheel Arches.

It's quite surprising what a simple lick of paint can make to the difference of the look of the body.  Starting to look more like a real car now!!

Couple of Minor Jobs - Part 2

I have finished off a load of small jobs that are not really worthy of a post all of their own.

The first was to add an earth strap between the engine and the chassis.  Just to be on the safe side I bought a 50mm2 earth cable (which should cope with 345 Amps), with a 10mm lug on each end from PCS Cables.  This was bolted into a convenient hole in the engine block at the nearside front.  I drilled and tapped a hole in the top of the chassis rail and ground off a bit of the powder coat to ensure a good contact.

Engine Earth Strap 

I also put the final hose finisher on the crankcase breather hose.  The hose finisher that I originally bought is still hiding in the garage somewhere, probably hanging out with a 10mm socket, and laughing at me.

Breather hoses completed!

I have given the front of the radiator a couple of coats of Eastwood Radiator paint in satin black.  The bare aluminium finish was not quite in keeping with the "stealth" look that I have in mind for the finished car.  I should have done this before I installed the radiator onto the chassis, but I managed to mask up most of the front with newspaper and a couple of old blankets to protect everything from any over-spray.

Radiator masked up prior to painting...

...and after painting and masking removed

I have also added oil to the rear differential and the gearbox as it is far easier to do this while access is good rather than leaving (or forgetting) until the body is on.

I bought 2 litres of Castrol Transmax oil which is specially formulated for limited slip differentials and used a funnel and a length of clear PVC tube to fill the differential with oil.  I managed to get almost all of the 2 litres into the differential before the oil started leaking back out of the filler oil.

Differential oil

Funnel and PVC pipe filling arrangement

For the gearbox, I bought 3 litres of Motul Dexron III oil which is the recommended fluid for the Tremec T56 transmission.  I used the same funnel/pipe setup to fill the transmission and again managed to get almost all of the 3 litres in before the oil started weeping out of the filler hole.

Transmission fluid

Filler hole for T56 transmission

I also have finally got around to welding up the various threaded bungs I have added to the chassis for the fuel tank, gearbox and exhaust mounts.  I treated myself to a day welding lesson at The Machine Shop to try and get the hang of TIG welding. I'm still not "stacking dimes" but at least I managed to master the art of getting a bit more heat and penetration into the welds.  As the body will sit on most of the locations of these bungs, I ground them down flush to the chassis rails and then treated them to a couple of coats of POR15 rust preventative paint.

Powdercoat ground off around area to be welded

A dodgy stack of dimes...

...after grinding welds down...

...and after two coats of POR15