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Mad Ax

Big 6 - Custom 6x6 Element Enduro Scale Builder's Kit

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Next trick was to make a battery tray.  Two trays are included with the kit - one for regular-size hardcase LiPos and one for shorties - but I'll have to use a small 3S softie in this chassis, as there isn't much space left, plus I wanted to give myself some surfaces to mount light switches on later.  This turned out to take up most of the rest of the afternoon, but I'll keep the text brief and let the photos do the talking.

Aluminium L-section mounts to stock holes

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2mm FR4 sheet is light and strong

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finished article has mounting points for the motor wires.  It looks a little uneven, but that is deliberate as the battery packs aren't entirely square

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This is pretty much where I was at by close of play on Sunday.  It was raining way too hard for me to take it out for a quick test-run, but it worked OK on the bench.

The project is coming along nicely now, still loads of work to do on the trayback plus all the little odds and ends, probably the most important step now is getting the body mounted so I can start calling it a runner and taking it out for some test drives.

I need to make a decision on the shocks.  The stock Element shocks are beautiful (especially the bronze ones from the Kit 2 box) but I don't like that they don't match.  They're sold in 4s, so I'd have to buy a set of 4 and have two spare to get a matching truck, and that's expensive.  I'll see if there's a cheaper alternative out there that still looks cool, as the rears in particular will be visible.

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I was planning on having a long day in the workshop on Sunday, but the weather was nice, so I jumped on the motorcycle and went to the coast instead.  The first place I stopped off at was a bit grottier than I expected, and there was nothing there, so I went over to an old favourite place which is really popular with bikers, so popular in fact that my bike got blocked in while I was eating my seaside fish & chips.

But that was OK, I got some winter sun (actually it was T-shirt weather despite the wind), enjoyed my lunch and managed to get home just before 3pm - plenty of time to do a few little things on the 6x6 project.

First thing I did was added the sides to the trayback.

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It's a pretty big tray now.

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Kinda looks more like a commercial truck with the body on.  Not sure about it...

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I wasn't sure how to mount the roll hoop, either.  I'd had some ideas, but having a hoop inside a trayback didn't look right.  Maybe a solid square roll bar, but not a bendy hoop.

So I figured I'd park the trayback for now (maybe I'll use it as an optional bed, or save it for something else) and mount the cage direct to the chassis.

I cut this bar of aluminium and drilled it to accept the cage hoop.

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I'll have to tidy up the end of the chassis rails but that's kind of how it might look

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I don't have the right flux for brazing brass to aluminium, but I figured if I could get some solder on the brass it would lock the cage in place and stop it from coming out.  It's not tidy (I'm still learning how to braze) but it works.

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I had trouble getting the heat in and managed to melt the aluminium, but it's fine, I can tidy that up later

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Test-fitted

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Test-fit looks good, so I cleaned up those rough ends on the mounting bar and screwed it down.

I'll make some brass plates to bolt the other ends onto the chassis rails, but the hard part will be getting them in place while I solder them on.  I'll work that out later.

Since the hoop doesn't need to fit inside the tray, I've got scope for adding some diagonals in too.  Should look cool and give me somewhere to mount a spare tyre.

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accidentally posted in wrong thread - now moved to correct location

Edited by Mad Ax
wrong thread

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accidentally posted in wrong thread - now moved to correct location

Edited by Mad Ax
wrong thread

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I had a full day in the workshop last Sunday, although I don't seem to have that much to show for it.  It was the first of the colder days (although some sun in the morning made it T-shirt-worthy, for a while) and also I'm getting to the 80/20 cutoff on this project now, where a lot of work doesn't seem to go very far.  With that said, here's the handful of photos I took during last weekend's work:

First, some 1mm brass plate arrived during the week so I could make the mounting brackets for the roll bar.  After working hard for several weeks on the trayback, I've realised I don't like it (I'll probably resurrect it on the crawler I'll make with the leftover Element parts - fingers crossed to see what Father Christmas brings!) - which makes it much easier to make mounts for the roll bar.

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This flux came in a very small sample pack from CuP Alloys at a Bristol Model Expo.  I managed to mix it up way too runny last time out, which is why it didn't work so well, but I'm still practicing with brazing.  This week's results were definitely better, but still not perfect.

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On the right side, I kept the screw in to ensure everything was in the right place, but somehow, despite not having flux on the stainless steel screw, I managed to solder it in anyway.  I'm kinda surprised how well it stuck, and I had to cut the screw out later.

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It didn't take long to clean it up, although I had to file away some solder to get the screw to sit flat.  Next time I need to be more precise about how I make my cage, so I've got more spare end to braze to.

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Cage bolted into place.  I didn't need all that extra length on the 10mm alu bar, so I cut that down as well, and took some length off the chassis extensions.

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I wanted to make a rear bumper to house some tail lights and towing loops, but I didn't want anything too big.  I procrastinated about this for a while before I settled on some angle section.

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The 5mm holes will eventually have some red LEDs inside.  I'll probably 3D print a boss to hold them in.  Ultimately a rear winch would be a nice accessory, but there isn't really space for a fairlead between the LEDs, so I'll probably use a scale type winch mounted on top.

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It's really taking shape now.  I've ordered some more brass rod to make some cross braces, and I'll probably bolt the spare wheel on like so.  The main thing now is painting and mounting the body.  I've experimented with a few different options but I think I'll go with hook-and-loop under the sills, as there's plenty of space to attach it on the chassis, and the body sides are already starting to flare a little.

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I've also ordered a heavy duty driveshaft this week, fingers crossed it will take the punishment from the transmission to the transfer case, as that seems to be the weak point in this rig.

I might get a couple of hours later today or tomorrow, but I'm not sure what I can do before I throw the paint on, and I don't know when I'll get the masking and painting done now we're well into the cold and wet months - I could turn on the halogen lamps for a while tomorrow afternoon, if it isn't too humid, and I get the masking done tonight.

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One of the expensive parts of building any crawler is wheels and tyres.  And when you have a 6x6, you've got 50% more wheels and tyres to buy.  Fortunately, just as I was about to kick this project off, a used set of 7 wheels and tyres came up for collection at a local crawler event, for the price I'd normally pay for just one pair of Proline tyres.  The tyres are a Chinese copy of the popular Proline Hyrax tyre, and although the compound is probably not as good as Proline, and the sidewall detail is a bit less scale, I can't really fault the look of the treads.

The wheels are those ubiquitous alloy beadlocks that come with a bolted-on centrecap.  I have a very similar set on my SCX10 Cherokee.  They're a bit of a pain, as the centre cap has 8 M2 screws holding it in place, and the recess is narrow enough that only a plain M4 nut will fit on the axle - a flanged nut or locknut won't fit.  This is seriously annoying, because the nuts are forever coming loose on the Cherokee, and I have to carry around a 1.5mm hex driver to take all 8 screws out before I can tighten them up again.

However, these cheap wheels didn't come with a centrecap, just some M2 screws that kinda look like wheel bolts.  Except there isn't really enough detail in there for my liking, so I figured I'd have a go at 3D printing my own centre caps with faux locking hubs.

This is version 1.  This was grown direct off the foot, so the back is perfectly flat where it bolts up to the wheel.  The recess in the back can accommodate a flanged locknut, and 8.5mm of axle thread.  One of the really great things about resin printing (and believe me, it has plenty of drawbacks) is the detail you can get in these smaller parts.  In this case however, I lost a little too much detail for my liking - but it still looks great, for a prototype.

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The main issues with this prototype were:

  • screw hole too small, required drilling out (will always be an issue when printing off the bed, as the holes will close up too much)
  • screw cap recess to small, it ground out easy enough when screwing in a knurled cap screw but will be widened in later versions for a neater finish
  • overall diameter slightly too large, it didn't perfectly fit in the wheel
  • centre bore closed a little meaning they were a bit tight over a flanged nut

Main bonus points were:

  • PCD was spot on, screws went straight in to the wheels
  • visible dimensions look spot on when fitted - seems a bit big when on its own but they're soon lost among the big wheels and tyres

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I printed off a V2 prototype with an optional smaller rear cap where you wouldn't normally have a locker, and the fit issue was mostly corrected.

Later that day I was watching Dirthead Dave's video of Day 1 of Ultimate Adventure 2022, and I got a good close-up of some locking front hubs.  I realised mine were a little off, so I started a whole new design, using my initial dimensions as a template to build a better design using sketches and user-defined parameters, which makes it super-easy to tweak a design later without having to redo loads of stuff.  I went with a full locking switch design on the front, and a rear inspired by some rear hubs I saw on a Ford on a Google image search.

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On 11/25/2022 at 12:24 PM, Mad Ax said:

One of the expensive parts of building any crawler is wheels and tyres.  And when you have a 6x6, you've got 50% more wheels and tyres to buy.  Fortunately, just as I was about to kick this project off, a used set of 7 wheels and tyres came up for collection at a local crawler event, for the price I'd normally pay for just one pair of Proline tyres.  The tyres are a Chinese copy of the popular Proline Hyrax tyre, and although the compound is probably not as good as Proline, and the sidewall detail is a bit less scale, I can't really fault the look of the treads.

Interested to hear how you get on with these tyres, because despite your recommendation of the GMade ones I went for these, on the basis that they were so cheap that I wouldn't have lost much should they prove not much good, plus a bit of an upgrade path is no bad thing. And I did see a decent review somewhere. 

Watching this build of yours with interest. The concept puts a smile on my face and your ingenuity and workmanship are inspiring. 

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I didn't get a lot of workshop time this weekend, as I had to be at a mate's 40th birthday party in Bristol for midday.  Since I'm terrible at getting motivated if there's something on the calendar that I need to switch off and be present for, and also because I'd skipped my usual Friday evening walk because my wife was out at a market, I decided to head out to the countryside in the morning to get in a few miles of fresh air.

I didn't get back the workshop until after 3pm, so I decided I'd focus on some smaller, simpler jobs instead of getting stuck into something that could take the rest of the day.

One thing that needed doing - one of those simple, 10 minute jobs that is really complicated and takes hours - was wiring up the lights on the 6x6.  I won't be installing full functional lights on this rig (although the cab supports it), instead I just want simple headlights out front and tail lights on the back.

I opted to hook the lights up to the programmer port on the ESC.  Mainly this is because I'd already installed the radio and all the wires in the waterproof receiver box and didn't want the hassle of opening it all over again, also because it felt neater this way.

I usually begin by hooking up all the LEDs to a breadboard, to make sure I've got my resistor values right before I start soldering things.  In this instance I couldn't find my breadboard, which prompted 5 minutes of me wandering around the workshop saying "Where's me breadboard?  Eh?  Eh?  Have you seen it, sir?  Have you seen it, madam?  I've seen you wrapping presents when it's nobody's birthday!" before I eventually found it on the workbench.

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I then totally got into a Thing, and did pretty much the entire soldering and braiding job without picking up the camera, before I took this somewhat awkward pic of the braided wires being cable tied along with the motor wires.

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The whole thing was slightly awkward, as cables run off in various directions and somehow or other I managed to make them just a little bit too short.

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Switch installed on the battery tray, for convenience

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LED lights make the tail lamps.  I'll 3d print a boss to install them in so they don't poke through so far.

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Next up, I decided to install the new 50-70mm propshaft I got from RCBitz.  It's listed as an RC4WD part, but comes in JD Models packaging.  It wasn't cheap - £55 - but is listed as being strong and scale.

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The part looks nicely-made and seems sturdy and attractive (although the latter attribute is less of an issue on this build).  The studded rings around either end are detachable - I think they're made like this for appearance only, but the unions are probably weaker without them installed.  Underneath the rings, however, the threads in the unions were neither entirely happy-looking, nor drilled square, so I couldn't easily get a threaded grub all the way through.  That's a bit of a step backwards, ideally a propshaft has a pin going all the way through to stop it popping off or spinning on the input / output shafts.

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One I put my old shaft next to my new one, I realised there was going to be a problem.  This is with the new shaft fully compressed, and the old shaft without the cup installed.

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With the new shaft fully extended to its maximum length of 70mm, the splines are literally only just engaged.  So, a "50 - 70mm" range isn't really valid - I'd say 60mm is the max to get any strength, and 65 the maximum allowable extension before it's at risk of popping out.  Turns out my shaft needs to be around 71-72mm, so this expensive little item is simply not going to work at all.

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Which was a shame, as that's a lot of money to spend on a propshaft.  I've ordered a cheaper, longer Punisher shaft which hopefully will be about right, be shortenable if it's too long, have sufficient angle in the UJs and be strong enough to transmit the load for all 6 axles.  If not, the project might well be stalled once more while I find a suitable shaft.  Fingers crossed it gets here in time for the weekend - parcels are taking a while to get here now as we enter the Christmas rush with all the postal strikes going on.

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Success!

My new RC4WD Punisher shaft arrived this week.  It's a bit chunkier than the basic UJs that I ordered many moons ago from China, although whether or not it's chunky enough to handle all the torque remains to be seen.  Build quality seems OK and it's nicely finished.

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The boss was a tight fit over the transfer case input shaft, which isn't too bad a thing as it will reduce slop, but made it awkward to get on.  More awkward still was the fact that the RC4WD boss has a really long collar, which won't fit on the transfer case or the axial transmission.

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I started by screwing the shaft to a screwdriver and turning it by hand in the grinder (a lathe would be so useful about now!)

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but it was hard to keep it turning smoothly, so I clamped it to an old drift pin and put it in the drill chuck.  Unfortunately the pin was both bent and too small to properly centralise the propshaft on, so my adjustments came out a little uneven, but this was way quicker than filing it down by hand.

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With the transmission side complete, I decided to run the motor to make sure the UJ would turn smoothly with the necessary angle on it.  It was running fine with my fingertips keeping the shaft on the right angle, until I accidentally gave it too much power, the shaft span out and locked up against the chassis, almost snipping my servo wires in the process.

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Fortunately no damage done to wires, chassis, transmission or shaft, so onwards, and with more care this time.

Both ends modified, fully connected up to the transmission and transfer case.  Ready for a test drive!

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I strapped in a 3S softy and went out for a test on my 1:10 scale mountain.  All my previous tests had ended in breakage of the propshaft, but before that point I had been sceptical that the truck was any good.  It seemed woefully short of both traction and torque and mostly just got itself tied in knots or hopelessly stuck.  I was wondering if the cheap tyres just weren't up to the job.

However, with the new prop installed, the results were totally different. I built up the confidence to give it plenty of stick, and it hopped up the initial climb with very little difficulty.  This catches all my other crawlers out, as it's only really possible in one direction but the lay of the stones makes it hard to get the angle without getting a wheel stuck or getting hung up on something.  The 6x6 got there right away.  The incredible steering angle on the front axle was a huge help, as was the overdrive from the transfer case.  The extra wheelbase and weight over the front stopped it from wanting to flip over backwards, which affects the CFX-W quite badly, and it had a lot of sideways stability too - the BOM often wants to roll over once it's up on the ridge, but this rig stayed flat and true all the way through and never once threatened to turn itself over.  The counter-rotating drive to the middle and rear axle helps prevent the truck from wanting to twist over like 4x4 rigs (even the BOM, with its TTS system).

If the underlying axles have a flaw, is that they're quite wide, so the pumpkins get hung up easily.  I think my other rigs have a narrower track, so there's a little more clearance, but this one really struggled.  However my 1:10 scale mountain is mostly made from broken concrete, which is very grabby, unlike the smooth stone more commonly found in popular crawling spots.

The slipper started slipping in places, so it probably needs another quarter turn, but it's interesting that the slipper broke free before the tyres did.

The only other thing I'm struggling with is the servo, which sometimes stalls.  The ESC is set to give 7.4V to the servo, but sometimes I would try to steer out of full lock and it would stop responding.  After a second or two it would swing back to centre again, like it had temporarily gone to sleep.  I wonder if my older 2200mAh battery (on a storage charge) isn't able to keep up with demand, and is browning out the radio when I'm trying to steer in a tight spot.  I don't usually have trouble with high-torque servos on 7.4V on these FlySky radios.  I think I'll have to see how it goes once I've given the pack a full charge and taken it out for a proper run on more typical terrain.

Generally, though, I'm hugely impressed with the performance.  Faith is restored!

 

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After the test drive, I turned my attention back to the roll cage.  It looked kinda cool with those two sloping bars but I wanted to add a spare wheel carrier, and figured I'd double it up with some cross-bracing for both scale appearance and rigidity.

The hardest part of brazing, as far as I can tell, is actually holding the parts in place during the process.  The little helping hands I use for electrical soldering aren't really strong enough, and required an awful lot of delicate fiddling to get in just the right place, only for them to shift once the flame is applied.  Plus it doesn't take much for a crocodile clip to glow cherry red in the flame from a MAPP torch, which is going to kill them eventually.  I'm not really sure what else I can use for this.

Anyway, I started with a diagonal bar to begin my bracing.

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Then I made another diagonal bar, chopped in the middle, so it is fitted in two parts.

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Then I cut a 1mm brass plate for the wheel to bolt to

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fin

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It's been a wee bit chilly here over the past few days - less than 5 degrees C in the workshop - but with a pair of 500W halogen bulbs keeping the energy suppliers in business I can heat my paint bench to around 15 degrees, which combined with a hairdryer to preheat the body and a tub of scaling water to warm the paint tins, is enough to get a lexan body painted.  The bonus with it being so cold is the humidity drops too (although there's a risk of it rising as the paint bench warms up).

I made a slight error when I pulled the black paint down off the shelf to give a final black coat on the inside (I hate seeing multi-coloured insides through the windows) - I grabbed the TS black by mistake!  But the coverage was good despite the cold, it hasn't reacted with the underyling PS coats, and it was fine when I peeled the masks off.  Hopefully it won't be an issue as it continues to cure and it won't be too fragile when running.

This is my favourite part of finishing a car - peeling the overspray film and window masks off!

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This is the last time it will look so clean and fresh:

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I still need to tidy the trim up at the back.  I'll need to work out what I'm going to close the rear panel with - probably some chequerplate, although I don't think I have any plastic scale plate.

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It's seriously hard to get a) a good mask seal and 2) good paint coverage in these lips.  Same happened with the Alfa body I painted over a decade ago, and the BMW E30 body, too.  But I doubt this will really show once it's all together.  I could put a bit of black plastic trim tape along the leading edge.

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The Carisma body comes with a really detailed grille panel, although assembly either requires hot glue or a soldering iron to melt the parts together.  Against my better judgement, I spent 30 minutes in the workshop late last night getting these parts joined before fitting.

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The end result is worth it, though.  So much better than a flat decal (JConcepts) or a complex moulding that you have to painstakingly mask and paint (Proline).

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I took the body up to the workshop before bed last night and grabbed a few photos

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Getting the body painted has opened up the last few key steps in the project.  The  most important being the fitting of the body.  Currently it looks like it's sitting too high, so it's probably resting on something that wasn't there when I fitted it before.  There's not a huge amount of vertical wiggle-room as it will look silly if the roll bar is too low, so I need to address that.  I may need to take more out of the arches too, to make space for those big tyres to move around.

The body also has a tendency to splay out behind the front arches, so my fitting plan will involve securing those in place.  Probably I'll just use hook-and-loop on the door sills, with some internal structure to ensure the body can only be located in one place.

Also yesterday I booked my ticked for the SST Pay-and-Play day at the quarry on 30th December - this is a fun event run by the Southern Scale Trail crew, with full access to all the areas in the quarry and woodland, but with no actual courses being laid out.  This should be a fantastic shakedown run for the 6x6, if I can get these last few jobs done before the big day.

There's not really much to do now.  Off the top of my head:

  • build the body mounts
  • build a dashboard top to double as a protector panel between the body and the spur gear
  • design, print and fit the mounting boss for the rear lights
  • design, print and fit the decals
  • acquire, cut and paint a plate to cover the hole in the back of the body
  • probably a few other jobs that I'll forget about until I stick a battery in it at the quarry on 30th December...
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OK - mammoth update time!  I spent almost all of last Sunday in the workshop, despite it being below zero when I got in there at 9:30am.

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First thing I noticed was a nick in the paint from the exposed spur gear.  This must have happened while the truck was being moved around the workshop during the week.  It may be that accidentally backing the paint with TS black has made it a little weaker.

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So - proposed solution #1 - back it with some silage tape.  This is like duct tape, but wide, black and tough.  It adds a nice bit of weight to the body, damps the crashing sounds when it rolls, and stops it getting scratched from behind.

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With the body nicely protected, I'd be able to throw it on and off the truck multiple times without worrying about scratching it.

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