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Mad Ax

Globe Liner: MFC switch box in fuel tank

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Ever been bothered by the fact that there's no sensible mounting point for the MFC switch box on a Globe Liner?  It always seemed that the fuel tank was the perfect place for this.  It's just about the right size and is otherwise wasted space.

So, with a spare lunchbreak, I went down the one-way path of hacking my Globe Liner fuel tank apart with a variety of tools and came up with the following method.

Here's the lower half of the tank.  The first thing I did was hack out the middle rib with a Dremel.  I used a sawtooth wheel to start with but found it a bit easy to start cutting the main body of the tank if I wasn't careful, so I switched to a grinding stone.  This eats through Tamiya plastic like it's made of cheese.  It makes a mess but leaves a nice tidy finish once you flake off the melty bits.

Next thing was to hack into the screw tubes - I figure the tank can be glued without any trouble, so the screw tubes aren't entirely necessary.  I kept half of them in place to secure the switch box and stop it moving around too much.

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After a bit of hackery - shown side-by-side with the top tank half for comparison

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Similar treatment given to bottom tank half.  Note also that I had to cut into the end ribs a little to make space for the switch box.  Just a few nicks works well.  I tried various tools for this - Dremel, coping saw, junior hacksaw, and settled on a needle file.  The plastic is soft enough that the file goes through easily, makes minimal mess and is easy to control.  Junior hacksaw was good for getting through bigger sections quicker but runs the risk of cutting into other bits.  Dremel was just too unwieldy and likely to do serious damage.

img15729_88201884435_3.jpg

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These side-on shots shows how the switch panel fits inside the tank, with the plastic fascia and PCB slotting into the notches cut out of the end ribs

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Finished making cuts to the tank innards.  These shots show how I was much neater on the top half - the bottom half was more experimental!

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The next mission was the one I was dreading the most - cutting into the tank where it would be visible from outside.  I considered using the Dremel with a sawtooth blade, as in theory it should cut a straight line like a circular saw in wood, but in practice it's easy to be imprecise and the blade will melt the plastic, giving a rough edge.  I knew I'd never get a hacksaw blade in there and my coping saw is way too aggressive for plastic.

First thing I had to do was mark the cut line.  Getting a straight edge on the verticals was easy - the mouldings for the straps are the perfect width.  Getting a horizontal cut line in a place where I couldn't get a ruler was tough.  In the end I came up with this:

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TBH I've recently found that that's what a lot of workshop time is about - being patient and finding a practical solution to a problem, rather than throwing a strop because I don't have the right tools or just rushing in with a badly-drawn squiggle and complaining later when I make a bad cut.

So, lines drawn, next plan was to actually make the cut.  I tried to use the tried-and-tested method that I use on styrene sheet - score with a craft knife until it cuts through.  Unfortunately, after several minutes of cutting and several blisters on the end of my fingers, I was nowhere near through the plastic.  I tried using some tough thread tied across the hacksaw to make a threadsaw, but that didn't work either.  I've cut panels off hardbodies before using this method but it didn't work on the fuel tank.

So the trusty junior hacksaw blade went back in and I made some very, very careful vertical cuts along the tank straps.  I'd already scored the area which I think helped to keep the blade true.  The hacksaw blade made a fairly clean cut all the way to the horizontal line, which I'd also already scored.

After repeating the vertical cut on the other side, it was just a case of very carefully folding the unwanted plastic against the score line until it came off.  I cut styrene sheet this way, as well as lexan bodies, so I was fairly sure it would work.  It gives a very smooth break which just needs a little tidying up with some abrasive paper over a square-edged block to make it perfect.  I haven't done that yet, so here's how it looks with the as-snapped-off edge:

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All in, I'm pretty pleased so far.  I think I'll secure the switch panel in place with sticky-back foam top and bottom.  The panel itself may not need any sticky if the foam holds it true.  The end caps will probably be enough to hold the tank together and I can always glue it if not.  I still need to drill the back to get the cables through.

I'm not sure if I'll dress the inside of the tank or not.  I was going to add a box out of styrene sheet to cover the gaps, but to be honest it looks good enough that it might not need it - I might just prep the inside with abrasive paper to remove the rough remains of the ribs then spray it with chrome paint.

Also I'm not sure if I need to make an outer cover.  I can either use some very thin styrene sheet to wrap around the tank and secure with clips, or maybe some very thin aluminium or stainless sheet and some hinges.  But it might look OK as is.  I'll take a view on that later.

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I made a false wall to mount the all the electrics on.  It fits neatly behind the cab interior but with all the wiring there's not a lot of space for the switch box and I find it awkward to get to.

I hunted around online for an alternative location that had already been done but couldn't find anything - hence this thread :)

 

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20 hours ago, Mad Ax said:img15729_88201884435_9.jpg

 

 

 

when i wanted to fill the gap on the chassis of the grand hauler with another fuel tank i used the spare ones that come in the mfc kits and i cut them to the size i req'd the hot glue gun them together filled the gaps with filler and painted them would this option have worked for you

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A little while since the last update - been busy tidiyng my working and getting everything ready for going to the Bristol Model Expo last weekend.  Of course that required getting the Globe Liner finished and ready to pull, so I had to get back to the fuel tanks.

First thing was to add a hole in the back for the wiring to go through.  I just used a circular file for this.

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Then I used a combination of Dremel grinding wheel and abrasive paper to completely smooth out the inside of the tank.  Well, I say completely, once you cut down into the supports there are little holes in the moulding for things like the fuel cap, but that doesn't matter - it won't be fully visible.  I just wanted to get rid of any obvious bits that would show.

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Then I threw on some cheap chrome paint that my wife bought for one of her projects.  There are much better chrome paints out there but this only needs to cover the inside of the tank where it might be visible.

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And finally, the fitted piece in situ:

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Given the amount of wiring hidden under the back of the cab, it's no surprise I wanted the switch box out of the way - it's still tricky to get the cab on without wires poking up into the windows.

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Ultimately - job jobbed.  I'm pretty pleased, really.  Turned out exactly as I'd hoped it would.  Initially I considered making a flap to cover the hole but a) I doubt it would lift properly with the steps attached and 2) I actually think it looks fine like that.  Not 100% authentic, but then neither are most of the other Tamiya rigs with external switch boxes.  It's a shame Tamiya don't make this as an option part because they probably could mould in a flap or door that would look much better.

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I had a chance to drive the rig a little at last weekend's Bristol Model Expo, and having an external switch is so much nicer.  I find the cab back quite fiddly to remove, especially when crouched awkwardly in the middle of a layout with loads of other expensive trucks whizzing past, and even more so with the pole trailer fitted (and that's a fiddle to remove in itself!).  Being able to creep across to the rig, flip a switch and drive off was great.

It's also nice when it's on the shelf.  The photo above is the shelf directly above my monitors in my studio, so it's really nice to be able to flip the lights on while I'm working and enjoy some ambient light.

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