Armortek

An idea of the complexity of the Cent bins (and how useful an accurate 3D model is in understanding it) came from this eDrawing section of Allan Bower's CAD drawings:



Sometimes, it's possible to design in a feature which is either difficult or impossible to produce. A case in point here was the join between the top plate and the rear of the base. A join of 80 deg is OK if you can get to the inside but is virtually impossible to solder from the outside. The capillary action of the solder is prevented and the solder just drips through. I should have realised. Off with the lids, remake with a flange.

Lids, re-made with the hinge support plate in place and the lip for the lid formed with small flange and a strip soldered on to represent the 180 bend of the original, which would have been tricky to get right. On the left, the front inner skin:



Base near completion, just some tidying up to do:








Just another five to go. Still, it's been satisfying to make.

Regards

Stephen

The forward bins have this box inside:



It also appears in the Illustrated Parts List:



Paul Scott explained that it protects the cable routing to the front convoy lights and the fire suppression system external handle. On the hull side, there is a hole for the fire cable and an armoured boss for the convoy light electrics, matched by corresponding access on the rear of the bin:







The enclosure is complicated (no surprise there) with a removable access plate and sloping top. I hadn't noticed it until I was ready to put the top plates on but as it's very visible when the bins are open, I decided it needed including.

First I drew up a card template. I use a selection of tools to cut brass. The Proxxon bandsaw for thicker pieces, bar and section, the shear brake for straight cuts and either a pair of aviation snips or a grinding disc in a Proxxon motor tool:



Bending a flange with steel bar and a repousse hammer:



Enclosure assembled and installed:





The bins are a long haul.....



Regards

Stephen

Ciao Stephen!
Your pursuit of detail is impressive ... ... and your work make me feel exquisitely inappropriate!
Your welding is a show well done!

Ciao, Iacopo, always good to hear from you.

The hull bin lids have pressed reinforcing channels and a way has to be found to replicate them. I always prefer where possible to use the same method as the original. In this case, the channels are not a full half circle deep, so a strip of half round brass would look wrong:



The front bins have another small dome to provide clearance for the convoy light fitting underneath:





I decided to trial a press die. First stage, anneal the plate locally:



Next create the die and the female pattern:



For the reinforcing channels, I'll use a press brake to get even pressure along the length but in this case a strategically placed G clamp worked:



Result:



Hope this is useful. Regards.

Stephen

Seems a while since the last update. The bins are a long haul, partly because with this sort of complicated brasswork, if you make a slight error early on, maybe a slightly inaccurate fold, it comes back to haunt you later on in spades. You know when you get to the tired, gung ho stage and start making errors. Time to reach for a beer.

Added the external fire extinguisher handles, beautifully provided for in the kit but just needing a bit of rounding. The housing is rectangular despite appearing to be square in photos:





All the bases done at last:







Now for the lids, which are even more over-engineered.

There are a lot of narrow flanges on these parts which are too narrow for a brake press to work. My approach to folding by hand uses some flat nosed pliers, a repousse hammer, a piece of steel as a die and a small chisel hammer. There is no particular magic in this. It's easy to introduce unwanted bends and the answer is lots of clamping and taking it in small stages:









The lids have seven folds apiece, in both directions, as they also form an inner skin. I reckoned on this being a fold too far and split the skins into two parts, inner and outer:





All the bits done, at last, less pressing the reinforcing channels in the lids:



The lids consist of a round 50 parts (80 when you add the hinges, catches and clasps). I did say they were over-engineered....

Stephen

Stephen,

Outstanding build quality, these bin are models all on there own. The attention to the detail on your bins to how they where made on the original bins is model building at its very best. Incredible work, very inspiring.

Regards

David

Next challenge is to form the reinforcing ribs on the bin lids, which aren't semi-circular in section:









Time to test the die pressing technique used on the base of the front bins above. First step is to make a die, consisting of a punch made from 5mm brass round section soldered in a slightly oversize channel and a die block with the two channels in the correct spacing:



The brass then needs annealing by heating and plunging in water (in this respect brass behaves differently from steel which needs slow cooling):



The brass lid is then clamped to the die block, the punch aligned and then pressure applied using more G clamps:



Finally, to make sure the punch is fully home, a couple of firm taps with a brass mallet:



The results:





Hope this is of interest.

Stephen

great stuff, i like it, small informative how to do posts, thanks for taking the effort, regards simon.

Very interesting and informative, as always

I have to admit I'm storing all this up for when I need to make the strengthening ribs in the front mudguards of my Sherman squadron

Have you considered zinc sheet in place of brass Tim seems to work wonders with it and it would 'damage' to a dull silver rather than the gold of scratched brass.

The main disadvantage seems to be that it isn't available in as thin sheets as brass.

Adrian.

Thanks Simon, Adrian, hope it's useful. Adrian, I've looked at zinc as you say. Getting the right thickness is pretty critical to these assemblies and die pressing in particular. I'm using 0.3mm for most sheet parts and specifically where pressing is involved and 0.7mm for structural stuff. I haven't found that in zinc yet.

Now that the lids have the reinforcing channels, time for assembly. First the outer end plates and their inner double skins:



Then the front inner skin. This has two flange seams. This is where the resistance soldering comes into its own. At the top, where you can pinch the two joining faces together, the callipers are best. They hold the work true, allowing the flux to be added and the silver solder to be drawn into the joint by capillary action. For the bottom flange, the probe works best, allowing some pressure to be applied to keep the seam in the correct place:





Inner strengthening hat channels and clasp catches added:





Centre long bins complete less the hinges:







Regards

Stephen

I've found zinc down to 0.8mm on ebay but no thinner - I guess it gets a bit too floppy after that. I've not tried any actual online metal suppliers though.

Those boxes of yours are absolute masterpieces

And the callipers look ideal for that kind of jointing.

Adrian.

Ciao Stephen.
Now I do not know what to say when I see your work is marvelous!
It seems to be in the laboratory of a goldsmith: congratulations!

you must be pleased with the result, they look superb, and a very visual position on the tank, well worth the effort, regards simon.

Hi Stephen
Just keeps getting better and better simply stunning.

Derek

Hi Stephen,

Simply amazing work on those bins - you´re an inspiration to us all.

Regards Per