Mark IV No. 01 - "Kathleen"

[Adrian Harris]

Been slowly working on the outer panels. Have almost all the parts primed/painted now:

I have also drilled out the holes above the sponsons to 4mm, so that I can use the same M3 inserts as on the sponsons themselves, for the line of hex head bolts which runs along here

Definitely the sketchiest bit of drilling I have done on my pillar drill so far, as I didn't want to strip the whole thing down again just for these holes.

I've also drilled out the missing hole in the track angle towards the rear of the tank.

This evening I've sprayed up the upper track run pieces, and will do the lower ones tomorrow. That should be everything done on these sides.

Hope to get on with the inner frames and the basic hull pieces and cab at the weekend.

Adrian.

[Adrian Harris]

Back on Page 1 I decided, in a moment of madness , to reduce the height of the front of the cab.

This has the knock-on effect of leaving the cab sides the wrong shape. I've already modified one side so decided to tackle the other side today.

There are several steps, which I've outlined below.

Step 1: Use a Dremel cutting disk to cut a slot from the front until about 2mm from the back. Eye and ear protection is a must

Step 2: Using the same cutting disk, remove material from the side plate to create a shallow wedge shape, so that when the two sections are pressed together, the part matches the shape of the cab. Ear protection is even more of a must when vibrating the end of a free sheet of steel

Step 3: Using silver solder and a butane torch, solder the top flap back onto the side, keeping the parts in alignment with a sacrificial crocodile clip. Although I've been soldering electronic equipment for near enough 30 years, I'm nowhere near as good a silver solderer as I ought to be

Step 4: Clean off the excess solder - there was quite a bit - and the flux, using a flat sanding disk and a wire brush, both in a hand held electric drill:

Step 5: Fill in the old rivet holes and any gaps in the solder with JB Weld and leave to solidify for a few days:

Step 6 onward will be to sand back the JB Weld to a flat finish, recreate the lost rivet holes, prime and fit to the cab itself.

Adrian.

[Adrian Harris]

Have people detailed the cab and rear plate before assembling the hull, or afterwards ?

The former looks sensible, as I'd like to leave as little blood inside the hull as possible

Adrian.

[Steve Stuart]

I detailed as much before final assembly, and held off as much as possible before then to allow for things to be taken apart for things that were discovered that needed doing!
Steve

[Chris Hall]

Adrian -

A lot of the Mark IV can be done as sub-assemblies, with it all coming together at the end. I see them as:

• inner frames / floor / inner track runs (extra armour, and light mounts, on inner front horns if you choose)

• front cab (all sides)

• rear bulkhead, with fuel tank, extra armour (if you do it) and shielding over the radiator louvres (again, if you do it)

• outer frames

• rear roof / spud box

• roof with top housing and exhaust manifold

Then you can bolt everything together, and fit the rollers / drive cogs. That really just leaves the tracks, and then fitting the sponsons (which are also individual sub-assemblies).

Make sense ?

Chris

[Adrian Harris]

Thanks Steve.

I've just sent off a quote request for getting the redesigned rear vent angles and front horn armour plates to be cut. I hadn't realised how much you'd changed the vent parts, so have made up plans for new side angles, top cover and side cover. I doubt they will fit perfectly first time around but I find it easier to work with the metal than to print it out on paper.

Next is to get the rear armour converted from your plan to CAD.

Then I'll need to see how you extended the unditching beam rails. Will you be bringing Bloodstone next time out ?

Adrian.

[Adrian Harris]

Thanks Chris.

I currently have the outer frames made up with the track runs and all the plates etc but I doubt it matters to which side they fit.

At the moment I'm trying to bash the cab into shape, as I found it wasn't quite the right angle in the middle, which was annoying as I'd already added and painted the middle cross plate

Cab sides still need to five rivet holes reinstating but the cut-and-shut part is all done and they seem to match the main cab parts OK.

Still tweaking the female sponson armour and may have to get parts cut again. I thought they were fitted together by bevelling the edges of the various plates but all the pictures I can find seem to show them with just the square edges butted together.

I went to Ashford yesterday after the Friends visit to the Weald Foundation and measured up the lower parts of the female sponsons, so now I need to draw up CAD drawings for them, but I think I may leave all that until after Amiens 100, other wise I'll never get her finished

Adrian.

[Adrian Harris]

My kit of parts for the rear louvres turned up today from the laser cutters:

Once the sides and top were bent into shape I was able to make up the whole part:

There are some tweaks to be made - one of which was that there were supposed to be slits in the angled pieces to assist with getting the folds in the right places but the cutters seem to have ignored these

The hole spacings for the louvres and the mounting holes are spot on but the holes in the side shield, which stops the tracks dumping muck into the louvres, are too high, so it doesn't sit under the top cover. Also, the whole thing sits a little high, so you can see the bottom of the aperture. With the bends in slightly the wrong place, the mounting holes on either side don't quite line up with the rear plate, but if I can get them to add the slits, I should be able to get the bends in the right places.

So, a couple of mods to the drawings and it should be good to go.

Many thanks to Steve Stuart for the nod towards Knupfer. It would be impossible to get the look right without oversized nuts and bolts.

Adrian.

[Robert E Morey]

Looking great Adrian.
There are enough screw and rivets to drive one crazy! No such thing as a quick build on this one! Great work.
Bob

[Adrian Harris]

Thanks Bob. Certainly a labour of love this one.

I've just laid out the track chains to make a start putting the track plates on and my word they're messy.

Might need to buy a boiler suit for this part of the build !!

Adrian.

[Adrian Harris]

I've made a start on the tracks and wonder about how careful I need to be with alignment, as there's quite a bit of free movement due to the relative sizes of the M3 screws and the holes in the track links.

I'm fitting the four outer screws per link finger tight, then manipulating it to find its preferred location, then tightening down the screws fully.

I'm checking with a set square every five links, and so far it seems to be sitting square, so I'll carry on with this method.

The steel bar which links the two gears is a tightish fit in the gears themselves but quite loose in the spacer and I'm surprised how much movement this allows the gears relative to each other, but I suppose this is to cope with just the wiggle room I'm finding in the links.

Adrian.

[Daniel Scholefield]

From my experience it isn't too important, it never even occurred to me to do that and my tracks fitted together with no issue. Alignment 'by eye' seemed to work.

[Chris Hall]

Daniel+1.

You'll probably also find that, over time, you lose the odd bolt. There's no suspension on our Mark IV's, so they do shake around a bit ! It's never been a problem just to pop another one in.

One less thing to worry about !

[Adrian Harris]

Thanks guys - back on it again tonight

> You'll probably also find that, over time, you lose the odd bolt

I'll be having words with Loctite if that happens as every bolt on this thing has been dabbed with it.

Adrian.

[Adrian Harris]

One track run done, bar the three at each end.

As I suspected, although the chain links line up at one end, there is between 2mm and 3mm difference in the position of the ends of the links at the other end. I can only hope that the strain of pulling the tank around will even things up. That's assuming they aren't too banana'd to get onto the tank

Adrian.