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Scratchbuilding pt.11: Brass Frameworks

Our Laplander build has already used brass where styrene just wouldn't have been tough enough (the mirror holders), but for the next part, simple cutting and bending won't suffice - we need to actually join parts together. Brass has a great advantage over steel in this regard - you don't need a welding set and the skill to use it, you can simply solder bits together. In this instalment, our worked example of a brass framework will be a roof rack for the Laplander, but the techniques are useful for other scale bits too - ladders, handrails, antenna arrays on ships, etc.

 

Thoughts on Rack Size & Shape ...

Having looked at a lot of pictures of Laplander C202s, I have to say there really isn't much in the way of standardisation to what we could more widely refer to as "roof furniture". I stopped counting at 210 different vehicles, but within that:

  • 150 had no roof furniture at all;
  • 3 had external roll cages (compromising little more than vertical poles shaped to fit the contours of the front & back at each corner, and longitudinal tubes of the same diameter along the roof);
  • 8 had a popup camper roof;
  • 2 had a roll out awning down one side;
  • 19 had (just) some sort of roof lamp - amber beacons seemed to be very popular, as were driving lights arranged in threes;
  • 3 just had ladders.

Expanding on ladders, they were most often associated with roof racks (otherwise, what's the point?), and were of varying designs:

  • narrow, full height (bumper to gutter) down either side at the back (seen most often);
  • much wider (& rendering the tail door unusable);
  • narrow & only from waist to gutter (with rounded risers)
  • as above but with 90 degree angles.

Of the 26 vehicles I saw with roof racks, the most common variety started on the roof just behind the cab doors, with 3 triangular gutter mounts per side. They also had 5 lateral bars, heavy side bars topped with lighter bar on top & 5 uprights (all square), and a distinctive feature at the front - a single round tube crossways at the front, halfway between the top & bottom side rails.

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This I suppose is the most "standard" rack arrangement then, but there are an awful lot of other variations out there. They run from varying number of lateral roof bars (two to six), all sorts of racks, all sorts of boxes from the useful to the dangerously high amount of weigh up top (via the tasteless), and a wide variety of ladders - some of dubious utility - and one that looked like it had been stolen from a swimming pool.

The permutations are too tedious to mention, but let's just say that whatever design is used on a scale version, it can't really be "wrong". And on that basis, I'll be building a slightly more utilitarian and practical version.

 

Buying

Brass (and a lot of other metals) are still mostly sold in imperial sizes. I picked 3/32" (2.38mm) rod as a good compromise between visual size, strength and weight, 1/8" (3.18mm) tube as it has the right internal diameter to use for joints without too much trouble, and 1/4" x 0.016" (6.35mm x 0.4mm) strip as it's thin enough to chop into suitable lengths & drill easily. All come in nominal 1' / 12" lengths (305mm), other lengths are available but they're harder to come by and more expensive.
For instance, I would have like to use 1m lengths of 3/32" rod to reduce the number of joints needed, and also given the option of making a full length rack. However this would have added at least 50% to the cost and it just didn't seem worth it. This will be a 3/4 length rack, but 240mm x 160mm is still pretty large & will take a lot of scale accessories to fill it.


You will need:

  • 11x 3/32" x 12" round Brass rod (e.g. 3 packs Albion Alloys BR5);
  • 1x 1/8" x 12" round brass tube (e.g. 1 pack Albion Alloys BT3) ;
  • 2x 1/4" x 0.016" x 12" brass strip (e.g. 1 pack Albion Alloys ABS1);
  • 6mm punch (or similar) to use as a former;
  • Vice, hacksaw, files including square & round needle files;
  • 8x M2x 6mm cap head screws (or similar) + 12 washers & 6 nuts;
  • Centre punch, 1.5mm, 2mm, 2.5mm drill bits & drill;
  • Masking tape of various sizes;
  • Acetone, Isopropyl Alcohol or similar for degreasing;
  • Soldering iron (25W or 40W) & solder;
  • Scrap bit of wood to act as temporary jig;

 

And for the optional parts:

  • 1mm, 1.5mm and/or 2mm nylon braided cord, heatshrink tube;
  • Paperclips, 1.5mm shock cord;
  • 1.5mm or 2mm styrene sheet, cutting implements & glue, cloth, 2 part resin.

 

Note on Solder & Soldering Irons

My preferred solder is a high quality (like RS) 60/40 Tin/Lead mix with multicore flux. For applications such as this I like to twizzle several strands together with a battery drill to reduce the contact time.

My current general purpose soldering iron is a cheap, 15 year old, unbranded one rated at 25W which performs far better and has lasted far longer than it has any right to - though it's possibly a little underpowered for this sort of work. The reducing availability of replacement bevel tips for it is becoming a problem though, so sooner or later it'll need replacing ... the Weller SP40N looks to be quite a promising candidate.

 

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Top & Bottom Rails

Take four lengths of the 3/32" rod (checking all are the same length), file off any irregularities at the ends, mark points 30mm from each end with tape & pen (image 3), then make a 90 degree bend at each marked point, making sure both ends are in the same plane horizontally (image 4). I suggest making the bends around a small diameter former (like a 6mm punch) as the brass can snap if bent too sharply (or repeatedly).

Cut eight 100mm lengths of 3/32" rod & clean up the ends.

Cut eight 10mm lengths of the 1/8" tube & smooth out the ends, making sure the pieces will fit over the rod ends (image 5).

Degrease the areas to be soldered & fit all the bits together to make two frames (image 7). Depending on how well the joints fit (or not) you might need to "stake" them, i.e. use a centre punch to put dings in them to hold them together so they don't move out of position (image 6).

Heat up the soldering iron & apply a bit of solder to the tip to aid heat transfer, pick a joint & heat near one end from underneath it while up pushing solder into the gap until it looks full. Repeat for the other end - this time you might see a bit of "bubbling" in the solder as the last of the air is expelled from the joints. Repeat for the other joints.

Once cool, file/sand off any excess solder + flux (image 8).

 

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Crossmembers

I think 6 additional cross members is the right balance between giving enough support to loads & not doing too much soldering. I measured the gap between the ends of the frames at 248mm, that divided by 7 is 35.43mm - so I marked a series of 8 lines that far apart on a bit of scrap plywood (image 9). I taped one of the frames down, then sorted out the cross braces.

These were cut 3mm wider than the gap - so 163mm in my case - then the ends filed straight. I used a square needle file (aka warding file when they have handles on, or diamond file if you prefer) to cut a V in one end, then smoothed it off with a round file (image 10). To make sure the notch in the other end was in the same plane I stood the first end on a scrap bit of rod while I got the second notch started (image 11). Tape each of the bits to your "jig" after cleaning (image 12).

Solder each joint by "tinning" the end of the soldering iron with a bit of solder, apply the tip to the underside of the frame right next to the joint & fill with solder - you might find you have to start on the frame & drag it across once the solder starts flowing. You should see when the joint is complete. If you look on the underside you might see a blob of excess solder, if so, reheat the area a touch to get some of the solder onto the tip of the iron, then flick that off (onto a wet rag or sacrificial bit of wood, etc).

You can clean up the flux at this point, but the frame should stay on the "jig" for now.

 

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Joining the Top & Bottom

Cut six 22mm lengths of 3/32" rod & notch each end as before (Image 14; + see image 17 for positions). It can be quite fiddly to get it to all stay together until its soldered up, I used tape on each joint, plus tape at strategic points and an extra block of wood to keep it all square (image 14). Removing the tape from one joint at a time, I was able to solder all four outer uprights and the top end of both inner uprights before stripping all the tape off & removing the rack from the jig to do the two underside joints.

 

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So far, each soldered joint has been far enough apart to avoid remelting previous work, however I would still recommend cooling the area around each joint after soldering (use an old wet flannel or similar) to avoid burns while manoeuvring the rack.

We also need to put reinforcing joins on the side, and have a way of fixing the rack down - this is where the 1/4" strip comes in. Bend one end of a strip over a spare bit of 3/32" rod (image 15), then cut back to a half round shape (image 16) - it might look a bit wasteful but the results are far better this way. Cut the strip down so the overall length is 44mm (including the half round). Centre punch a point 5mm up from the flat end & drill a 2.5mm hole there. Test fit to the rack, & put a slight outward bend in the strip where it meets the lower rail. Repeat for the other five mount points.

Theoretically all the parts will be the same, but I marked them L1, 2, 3 and R1, 2, 3 as I made them, just in case, before taping them on across the lower rail for soldering. Join the half round ends first, then to the lower rail. Clean up and excess solder & flux as before (image 17).

 

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Gutter Mounts & Test Fit

Roof racks before the early 1980s used to rely on clamping to the distinct gutters found on vehicle of the era. I suggest bolting through the roof to hold the rack on, but there's no reason not to fake clamps of some sort.

Having first center punched the upright on the front right corner of the rack for later orientation, I carefully tweaked the angles of the strip uprights so the rack sat centrally on the roof.

I marked the mounting tabs centrally, 5mm up from the bottom, punched & drilled 2.5mm holes.

The clamps are more strips of 1/4" brass, made & fitted one at time. Each was carefully folded to fit around the 2mm square strip gutter, and cut and drilled to match the mounting tab (image 18). Fitting involved drilling a 1.5mm hole through the side of the roof & fixing everything together with an M2x 6mm cap head screw & M2 washer (image 19). Repeat for the other 5.

An extra washer & nut will be fitted on the inside once painting is complete.

 

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Scale Ropes

Braided nylon cord is a fairly decent scale substitute for polypropylene ropes. Previously I've cut the middle out of the side of a large cardboard box, strung braided white 2mm cord across it & spray painted it, but there's been something of an explosion in the number of colours available so that's no longer really necessary. I think slightly dull/dirty shades of yellow & blue work best.

It's also available in a number of diameters - 4mm (good for simulating tow ropes, thought they can look like you've just used a length of shoelace), 2mm and 1.5mm (suitable for the scale lashing down of larger objects) and 1mm (so a scale 10mm) - these three sizes are sometimes also known as "rattail", "mousetail" and "bugtail", which might help when searching for them.

Lengths of the smaller diameters can just be chopped & the end quickly melted to stop it unravelling, but larger diameters can look better capped with a small bit of heatshrink.

Loops (quite adequate for tying down) can be made with a dab of superglue and a larger bore bit of heatshrink, but for towing (especially if any shocks are likely to be involved) it's probably better to stitch the ends together before gluing and heatshrinking.

 

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DIY Bungee Cords

First you need some suitable nylon covered elastic - search for shock cord. This is available in a wide range of colours and diameters, but I'd suggest a muted colour and a small diameter such as 1.5mm would look most scale.

You'll also need some standard paper clips (which can be plain or coloured, but do need to be metal), some wire cutters, and something to form the hooks around - I'd suggest a 2mm drill bit (mounting it blunt end up in a bench vice will help enormously) and a left over bit of 3/32 rod.

Straighten a paperclip out - it doesn't need to be perfect. Put a 90 degree bend in, 20mm or so from one end, poke that end into the vice & wind the paperclip round the drill bit 4 or 5 times (image 22).
Use the 3/32" rod to bend one end into a hook (image 23), then trim both ends back (image 24).

Cut a length of shock cord & tie a knot close to one end, cutting off any excess (image 24). Poke the other end through the hook end of the metal end before closing the bottom turn up by about half. Pull the cord until the knot stops against the partially closed loop (image 25).

Make another hook/end as above, but slide it on to the other end of the shock cord before tying the knot & closing up the last loop on the metal part. Trim the shock cord & pull through as above.

Repeat the process with varying lengths of shock cord (anywhere between 8 and 14cm) until you have enough bungees (image 26).

 

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Fake Load

If we look at the items made in instalments 3, 4, and 5 in this series, I don't think the surfboard really suits the look so I'm going to leave that out, but even if we use all the other things (plus the spare jerrycan made in part 10), only half the rack is covered.

We could add a couple extra spare wheels, but there's already one on the back. We could make some more bits using the plans we've already got, or make some new ones, but there is an alternative - a fake load, with the details obscured by a tarpaulin. I've seen this done very effectively with card & tissue paper sealed with PVA, but I'm going to do it with something a bit more robust - styrene sheet, cloth and a 2-part resin.

Start with a piece of styrene 155mm x 120mm, 1.5mm or 2mm thick. Look through your styrene offcuts & scraps for bits to make rough boxes, trays, drums & so on from (image 27). Remember that only the bits that will be seen at the surface or outside the edges of the tarpaulin have to be finely finished. I probably went overboard in terms of build quality. Stick these to the baseplate (image 28).

 

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Cut a rectangular piece of cloth large enough to mostly cover the load (about 2cm bigger in each dimension that the basepate). I used 100% cotton Bakers' drill as it looks like scale canvas.

Wearing gloves & working on a sheet of plastic (it could be a high quality rubble sack, a punched pocket, etc), mix up a small amount* of 2-part resin. I used Pacer Z-Poxy Finishing Resin as although it has some flaws (smell, long cure time) it naturally flows out to a very thin level.

* Note: this will depend on the absorbency of your cloth, but I'd estimate no more than 20 to 30ml would be needed.

Spread the cloth flat on the plastic sheet & wet the cloth all over with the resin. Arrange your tarpaulin artfully over the load (start in the middle & work outwards). The time you have to do this will depend on the resin you use - I had a least an hour before the resin started to turn sticky & the cloth would stay where I put it (image 29). This is a bit unusual though, most resins will start to cure in a few minutes, especially at room temperature.

Leave to set overnight, then peel of the plastic from underneath & clean up the edges. The fake load will get primed & painted later, and can then be bungeed or roped on the rack as a whole (image 30).

 

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Next Time

In the next instalment we'll cover painting & final assembly of the Laplander as a whole - but at the time I'm writing this (mid- February with a dusting of snow on the ground) that seems quite a long way away.

 ________________________

Written by TB member Jonny Retro