Brake Lines - Part 2

Having come up with a suitably OTT method of fixing the brake lines.  The next stage was to plan the routing for the front brake pipes and the clutch pipe.

The brake lines will be formed from 3/16" dia pipe while the general consensus is that the clutch pipe is formed from 1/4" dia pipe.

I wanted to keep the pipe runs as neat as possible with both pipes running parallel.  I also wanted to plan out where to place my bespoke pipe clips.  There is no guidance on the fixing of brake and fuel lines within the IVA manual.  The only reference to a distance between fixings is for electrical cables/wires, which according to Clause 8 of the General Construction section of the IVA manual, "must be...secured at intervals of at least every 300mm...".  The general view amongst the kit car community is that this is applied to the fixing of brake and fuel lines as well.

Having done all that I basically followed the AK suggested routing (as have most other AK builders), although as I appear to have too much time on my hands, I modelled the pipe routing and clip positions in CAD.  One slight change I did make, however, was to adjust the suggested position of the 3-way brake union on the offside chassis rail to give a slightly longer pipe length to the connection with the offside flexible brake hose; most other builders have commented that this short length of pipe is a pain to bend given the proximity of the brake fittings to the required bend and I figured that allowing a longer length of pipe might facilitate the forming of the necessary bends.

Pipe routing - clips at less than 300mm centres and adjusted position of the 3-way union

The plan is to run the brake and clutch pipes to some bulkhead connectors which will be held in place with a bracket mounted on the top of the offside chassis rail.  The clutch pipe will also terminate with a bulkhead connector, secured by a bracket, on the nearside chassis rail, for the flexible hose to the clutch slave cylinder to be connected to.

I acquired all the necessary brake fittings from Automec.  The bulkhead fittings are M10x1.0mm fittings (HU106) with brass locknuts (LNB2) and M10 female fittings (HU2A) for the 3/16" brake pipes and 7/16"x20 fittings (HU141) and 7/16" female fittings (HU4A) for the 1/4" clutch pipe.

Bizarrely at the time I bought the fittings Automec did not supply a brass locknut for the 7/16" bulkhead fitting - they do now, part LNB4 for anyone interested.  I spent many nights on the internet trying to get hold of brass 7/16" locknuts to no avail; eventually, I tracked down some steel jam-nuts on eBay but might upgrade to the brass lock-nuts for aesthetics at some point!

Bulkhead connectors - 7/16"x20 for clutch at the top and M10x1.0mm for brakes at the bottom

The basic configuration of the proposed bracket to secure the bulkhead fittings was "borrowed" from Stuart Holden's AK build blog.  I modelled the initial bracket in Fusion 360, which has a cunning function allowing you to generate a flat pattern for a sheet metal design, which takes into account the radius of all bends etc.  I also went a bit overboard (a recurring theme) and modelled the brake fittings.  This turned out to be just as well, as I could see from the CAD model that, with my original dimensions, there would be no room to secure the three female unions on the mid-part of the bracket.  A slight adjustment to the dimensions and the problem was solved!

CAD model of brake/clutch pipe bracket

Drawing of sheet metal flat pattern

I cut out the drawing of the flat pattern and stuck it onto a piece of 2mm sheet steel.  I used an angle grinder with a cutting disk to cut the steel close to the pattern and then used a combination of bench grinder, grinding disk, belt sander and various metal files to get to the final shape.

I centre punched the location of all the holes and drilled out the 5mm dia holes for the mounting bolts and 5mm pilot holes for the fixings.  I then bent the three tabs to 90 degrees using a vice mounted metal brake (another homemade creation!).  The fixing holes were then opened up with a stepped hole drill; 10mm for the brake fixings and 11mm for the clutch fixing.

First cut-out with the angle grinder...

...following by a variety of sanding/grinding/filing implements to get to final shape

Mounting/Pilot holes drilled and fold lines scored

Ready for bending using my DIY metal brake

Tabs bent up and fixing holes drilled out to size

The finished article - looks just like the CAD model!

I treated the finished bracket to some candy red powder coat before marking up the fixing position on the chassis rail, drilling and tapping for some M5 bolts and securing in place with some stainless steel Allen-head M5x8 bolts.

Bracket after powder coating...

Mounting hole locations marked up on chassis prior to drilling and tapping

Bracket secured in place with M5x8 bolts...

...and complete with bulkhead fittings.

Now it's time to start running some brake lines!

Brake Lines Part 1

The routing of the brake lines is relatively straightforward.  The AK Build Manual shows the positioning of the pipe runs quite clearly and most other builders have had no problems with this layout and with fixing the pipes using P-clips or the plastic push-in type clips.

So clearly this is the way to go and it should all be simple, yes?

Well...

Clearly, for me, that would all be too simple...and I lay the blame squarely at the doors of the guys from Bad Obsession Motorsport (BOM).  I have been following their Project Binky build on YouTube for some time; there are several episodes charting their build of a Rally-spec Mini based on shoehorning the running gear from a Toyota Celica GT4 into the confines of the Mini.  These guys are evil geniuses when it comes to bespoke bracketry (of which their project required many) and when they imposed a "no P-clip" policy on the build and fabricated their own brake/fuel line clips, I started to get thinking.

The AK chassis is a thing of beauty.

 OK, maybe I'm getting carried away. but the chassis rails are all box section and fully sealed.  So why would I want to drill loads of holes into the chassis providing potential entry points for water and the risk of the dreaded metal rot?  I could inject Waxoyl into the box sections to mitigate this but surely it would be better to avoid the holes in the first place.

The BOM solution consisted of a steel plate, a couple of rivnuts and some 12mm thick nylon sheet; the resulting component can secure multiple pipes replacing several P-clips.  A CAD model of the basic concept is shown below.

Over-Engineered P-Clip Replacement Concept...

The steel plate, with the rivnuts welded in place, is welded to the chassis, the two halves of the nylon clamp are then placed over the rivnuts, bolted down and voila!  One pipe clamp with no drilling into the chassis rails.

After much mulling over this solution, I realised that I was probably being a bit anal about this.  On close inspection, there are already several holes drilled in the AK chassis for the body mounting bolts amongst other things.  I will also probably be unable to avoid drilling some holes for mounting the 3-way brake unions and eventually for mounting the fuel pump and filter.  Additionally welding the mounting tabs onto the chassis will involve removing some of the powder coat and having to try and recoat the patches, plus some welding into some tight spots between the chassis rails; which to be honest, sounds like a lot of faff (even for me).

(And actually by the time I have posted this I will have drilled a load of holes in the rear of the chassis for the fuel tank mounting...)

So maybe the answer is to bolt the clips to the chassis after all; in which case why not just use P-clips?  However, I still think the bespoke solution is quite neat and does have the advantage that I can use a single clip to hold multiple lines (including potentially the fuel lines) so that does reduce the number of holes that I will need to drill.

So with a slight modification, Version 2 of the P-Clip replacement concept was produced in CAD.

Version 2 - spot the difference!

The next step was to make a prototype based on the CAD concept.  The mounting plate was cut from a spare piece of 2mm sheet steel.  I drilled two 7mm diameter holes which were countersunk to accommodate two M5 rivnuts and allow the rivnuts to sit flush with the back of the plate.  A 5mm hole was drilled for the mounting bolt.

The clip body was made from two pieces 12mm thick Nylon-6 sheet cut 12mm wide.  The bottom piece had two 7mm diameter holes drilled to sit over the rivnuts and a 10mm counterbore 5mm deep to accommodate the head of the mounting bolt.  The top piece was drilled with two 5mm diameter holes with a 10mm counterbore 5mm deep to allow the heads of the fixing bolts to sit below the surface of the clip.

The final step was to hold the two pieces of the clip together and drill a 3/16 diameter hole and a 1/4 diameter hole (for brake and clutch pipe respectively) along the join line between the two halves.

All the components for the brake pipe clip...

M5 Rivnuts in place on mounting plate - large counterbore in bottom half of clip is for cap-head bolt

Bottom half of clip in place on mounting plate

Top half of clip in place - secured with M5 x 16 Cap-head bolts

Completed assembly - holes for 3/16 brake pipe and 1/4 clutch pipe

Rearview with M5 x 6 Cap-head bolt in place for securing to chassis

I'm pretty pleased with the prototype so now I just need to knock out a few more in various configurations depending on fixing location and pipes that need to be secured.

To be honest this is completely unnecessary and massively OTT compared to the perfectly adequate and usual methods of fixing brake pipes.  But it's another little way of putting my own stamp on this build.