Unibody Mk4 Spitfire 6

[BiTurbo228]

So I've been playing around with various different options for the handbrake cable and come up with a least-worst option.

Modified a 19mm deep socket so I could compress the belleville washers to swap the Peugeot pivots about:

One of those times when I was very glad to have bought an absolute monster of a vice as it only just fit between the jaws!

I tried swapping over the pivot arms side-to-side, but they get too close to the flexi union:

Initially I thought welding on the old pivot arms like this might work:

Before my brain finally caught up and realised that this would be pivoting the wrong way...

So I tried an underslung option which might work ok...

...before deciding on this arrangement:

The reason I prefer this one is that Markus mentioned having to keep the cable tensioned tight enough to make the brakes drag to get the handbrake to work at all. By setting the arm back at a shallow angle the effective lever arm is very short for the initial bit of travel, helping take up slack in the cable quickly. The effective lever arm increases as you apply the handbrake, helping the last few clicks of the handbrake to put more force on the cylinder.

The downside to this setup is I'll have to mount the caliper upside-down to get the cable orientation right, but I figure you use the handbrake more often than you bleed the brakes, so the compromise is in the right direction.

So with that decided I set about copying the shape onto the other side. Bent up another piece of 7mm plate and drilled some holes to align it up:

Bit of work with a flap disc and we end up with this

Next step is to weld it up, though I figure I should test it on the car first...

[BiTurbo228]

Weldy weldy

Goes on something like this:

Will need a bit of the caliper tickling with a hacksaw to let it move through its full sweep, but it's only the superfluous Peugeot cable mounting lug that needs to go.

[BiTurbo228]

Well it's been yonks since I've done anything on the Spitfire, but flitting between my place and my folk's place for childcare has afforded the opportunity to give it a bit of attention.

I'd picked up a Sure-Trac Subaru R160 quite some time ago, but they all come in too high of a ratio for my needs, so the plan was to swap the LSD centre into a 3.54 open diff:

Normally this is really quite a straight forward job as Subaru's manufacturing tolerances are usually good enough that you can just keep the shims and bearings together and swap things over. However, I noticed that some of the welds on the LSD core had cracked:

Apparently this is quite a common thing. So I pulled the bearing off that end (wrecking it in the process as it was super tight), and vee'd out the welds ready for repair. At this point I read a little more about how the LSD is constructed, and I don't actually think any of that is necessary. The end cap is screwed into the centre tube and the welds are just there to stop it coming undone. There's limited force on the welds as the threaded portion takes the majority of the load from the pawls inside, and the cracks probably occurred due to differential cooling rather than application of force while driving.

Oh well, too late now.

So I pinched a bearing off the open diff core, actually took some time to set up the backlash properly, and now have a diff that is very nearly in spec (0.21mm backlash where the spec is 0.1-0.2mm).

I've ordered some more shims to just sneak it over the line.

Next up is making up the hybrid Rover 100/Subaru driveshafts to connect to the uprights I've had machined for MGF bearings. Then the car should be rolling again (though I'll need a different prop again).

[Escadrille Ecosse]

Always something else on the go! So nice to see a bit of progress.

Similarly frustrated on the lack of progress with mine. Latest for me is a combination of injury and the relentlessly pish weather.

[Nick Jones]

16 minutes ago, Escadrille Ecosse said:

Similarly frustrated on the lack of progress with mine. Latest for me is a combination of injury and the relentlessly pish weather.

Can relate! 

[Escadrille Ecosse]

Just now, Nick Jones said:

Can relate! 

It's bollocks isn't it. My Dad always used to say that age didn't come alone. I am increasingly seeing his point.

I hope your back is improving

[BiTurbo228]

Yeah I count myself lucky that mine's not injury-related! I'm only early 30s, but I've already put my back out once or twice already (lifting and twisting...stupid boy). It's no fun at all, and always takes at least twice as long to heal as you expect (plus the rest of the time it takes to build back the strength you've lost during the healing process).

Pish weather I can relate to especially at the moment! Most of my time recently has been taken building a driveway so I can build a garage and actually work under cover and not lying on the wet ground outside. Just maintaining the old crocks that are currently running is tricky from a puddle.

I shouldn't complain mind! It's not everyone that gets the opportunity to build a garage, let alone have one already (that's full) and building another.

[Nick Jones]

D

8 hours ago, BiTurbo228 said:

Next up is making up the hybrid Rover 100/Subaru driveshafts

Have you got the inner CVs and do they fit the Rover shafts? There are some that do ….. the trick is finding them….

[BiTurbo228]

I have a set of inner CVs that should fit the LSD, but I've not yet tried them on the Rover shafts 

[Nick Jones]

Good luck with that. I’m told that the ones that are 75mm OD are the ones. I can tell you that 73mm ones are not….

[BiTurbo228]

13 minutes ago, Nick Jones said:

Good luck with that. I’m told that the ones that are 75mm OD are the ones. I can tell you that 73mm ones are not….

Useful stuff. Will pop out with a set of verniers tonight! Wish me luck 

[BiTurbo228]

Well aren't I a jammy sod! Pair of 75mm OD driveshafts on the first go!

If it helps these were ones badged for the Sure Trac diff. Won't work with the viscous version, but it's my understanding that the splines are the same as the open ones (not checked it personally though).

[BiTurbo228]

Inching forwards on the rear suspension. Popped some polybushes in the rear housing (had to get some new ones as I sold the last set with my old diff).

I'd also read that, if you're driving them really hard (e.g. as a club racer), the conversion plate spring mount can tweak side to side slightly. I doubt I'll ever get anything like that amount of g-force in my car, but adding some gussets felt like a good safety precaution:

I also took the opportunity to get some more shims and actually tweak the backlash down into spec. Didn't measure it this time, but as it was at 0.21 and the top of the spec is 0.2, just bumping it 0.05mm in one direction should be fine.

Just waiting on the right thread nyloc nuts and it can go in the car!

[Nick Jones]

Yeah, was considering doing something similar. More because the Vitesse is a weightier beast, especially 4 up (rare!) and/or with a boot full of luggage!

Does the spring sit flat on the bracket or is it wide enough to catch on the  arch?

[Escadrille Ecosse]

Nearly there with that. Looking made at the makers style.

But I do hope you are going to clean up the diff casing before putting it in. 

[BiTurbo228]

19 hours ago, Nick Jones said:

Yeah, was considering doing something similar. More because the Vitesse is a weightier beast, especially 4 up (rare!) and/or with a boot full of luggage!

Does the spring sit flat on the bracket or is it wide enough to catch on the  arch?

That's a good question. I haven't tested it on a spring yet. I suppose if it doesn't sit nicely you could cut a C into it and bend the edges down to reweld in more of an arch...

17 hours ago, Escadrille Ecosse said:

Nearly there with that. Looking made at the makers style.

But I do hope you are going to clean up the diff casing before putting it in. 

Haha I am definitely guilty of leaving diffs and axles and things unpainted and just rusty. I'll see what I can do, though part of the reason I've picked this up again is there's a risk of me losing the storage where it lives at somepoint soon. Getting it on its wheels and mobile would definitely help in relocating all of my junk (as would finishing my garage build so there's a place for all the junk to go!).

Oh, also, something that might help if someone's using the same cast rear plate. On mine the clearance between the mounting lugs and the two closest rear cover bolts was a bit tight. You can get a spanner in to tighten it, but only with the flats and not brilliantly. This might vary between castings, but I thought a socket head bolt would be better.

Unfortunately, the thread is a weird M10x1.25 fine pitch (seems to be a Japanese trend, like using 12mm and 14mm bolt heads instead of 13mm). You can get this readily enough in stainless, but I really don't like stainless for bolts. Turns out that a lot of Japanese bikes use this thread for various casing bolts so I managed to pick up some in BZP. You need ones that are 30mm long.

[Nick Jones]

Lots more manufacturers using metric fine these days. In some “unusual” sizes too. VAG now use M7 and M9 in occasional weird places. Often with some wacky splined head on it requiring a new tool (or whole set because can’t find singly).  Usually discovered on a Saturday evening. Bastards.

I like metric fine. “Normal” metric from M10 up is pig thread. Ok for farming and building but not engineering! I despise multiple head variations on the same vehicle though.

[BiTurbo228]

1 hour ago, Nick Jones said:

Lots more manufacturers using metric fine these days. In some “unusual” sizes too. VAG now use M7 and M9 in occasional weird places. Often with some wacky splined head on it requiring a new tool (or whole set because can’t find singly).  Usually discovered on a Saturday evening. Bastards.

There's a special circle of hell reserved for these people. Weird heads is one thing, but odd-numbered bolt diameters is just psychotic.

Definitely makes me grateful that the newest car I've ever owned is a 2002 

1 hour ago, Nick Jones said:

I like metric fine. “Normal” metric from M10 up is pig thread. Ok for farming and building but not engineering! I despise multiple head variations on the same vehicle though.

There's metric fine and then there's metric FINE. Regular fine thread is 1.5. This is some weird extra fine 1.25mm thread designed mainly to irritate people who think they have a decent stock of bolts  the Jag rear subframe is the same and uses some of these, interspersed with proper bolts.

Agreed that M10 and up coarse threads are good for building pigsties and not much else. They're 1.75 I think...

Oh, and I dislike multiple head varieties as well, though I've somehow managed to end up with a brace of cars where that's unavoidable. The XJ40 is almost entirely metric except the driveshaft flange bolts and the rear propshaft flange which are Imperial (the driveshafts by original design, the prop because I've used an XJS flange). The SD1 is entirely metric apart from the engine which is Imperial. The Spitfire is entirely Imperial except the diff and driveshafts which will be metric (and maybe the engine as well if I go for the Rover 2600).

At least they're mostly hex heads or allen keys, not these newfangled torx or even-newer-more-fangled male torx (which the M57 in the Jag is guilty of using, as well as 11mm bolt heads on the inlet manifold).

Edited April 30 by BiTurbo228