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Latest Update 01/10/2020: Now wearing JConcepts F250 body

OK, this is a bit of a random project.  It began life way back in the mists of time as something completely different, but I'll skip the convoluted history and go right for the current status.

I'm having a real thing for monster trucks right now, and I figured when I'd finished my TXT project I'd build a smaller, more garden-friendly monster from a TLT/Axial-based crawler that I put together a year ago from parts I had lying around.  I put together a series of Showroom entries about it last year, which you can read here, if you want some more detailed history of these parts:

https://www.tamiyaclub.com/showroom_model.asp?cid=133649&id=15729

 

I bought a JConcepts 1984 F250 body and some alu section that I could use to hack together a rough-and-ready truck out of these parts.  But before that, I figured I should test-fit the monster truck wheels to make sure they would work with the axles and links.  Here they are - HPI wheels and Ho Bao Monster tyres.  These have a history too - they have been in my wheels box for over a decade.  The tyres have gone white and powdery but are still soft and grippy.  I needed to use Junfac axle wideners so they would clear the links and shocks.

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With that done, I figured I should take it out for a test-drive as-is, before I took it apart.

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It drove reasonably well, although the Novak Fifty-Five crawler motor and Hobbywing crawler ESC weren't ideal for monster driving.  The wheelbase is too short and the CoG too high for crawling on my test mountain, and the tyres aren't right either, so I decided to throw in something with more speed.  I found a Yokomo 21 double motor in my motor box.  Coupled with a Probe WP speedo, it ran really well.  Plenty fast enough for my garden, lifts a wheel on acceleration but remains controllable, and jumps and bounces over bumps like a proper oldskool monster truck.  I think the crawler shocks have no oil in them (I always struggled to get those shocks working right) but it's surprisingly controllable.  Actually, it's an absolute riot to drive.

I threw on the Beetle body and had a proper play.

Unfortunately it does have some flaws.  The turning circle is appalling - the front axle is clocked and the screws interfere with the steering.  So a front axle rebuild was on the cards.

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Also the diffs were locked as I'd originally intended this one for crawling.  Open diff should help with the turning circle, so I decided to pull the axles apart.  Also the front propshaft - a modified SCX10 item - was binding really badly and kept pulling off, so I replaced it with a shortened Cross RC one.

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I'm glad I decided to open the axle as I found another issue that was going to raise its head at some point.

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Yet more araldited diffs - this seemed like a good idea at the time...  This is from the front diff and wasn't too bad, but I had a spare bevel set in my parts box so I tossed these to one side and replaced with new.

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The rear diff was more of an issue.  First a rounded hex screw.  A Dremel with a cut-off wheel is a real bonus here.

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Even with the screws removed the diff still wouldn't come apart.  Excessive araldite, I think.  This called for heavy equipment.

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Toasted Araldite.  Mmm.  I'm not sure if burning Araldite fumes are toxic and if that explains why I have a spinning head and raging nausea this morning.

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I managed to gouge out the internals and clean up the case but the gears are too dirty to reuse.  I took the cleaner set from the front diff and left them in 99.9% IPA overnight, which might help dissolve the residue.  I'll check later today if I have time.  Failing that, Jadlam Racing, a local-ish Tamiya dealer, had a new set of gears on the 'bay for £5.85 posted, so those should be with me at the end of the week.  Would be nice to make this one run again soon though, as it was such good fun.

So there you have it - more work to come as I build a proper battery box and fix up a few little issues to turn this into potentially my new favourite lockdown runner :)

(I also think I need to find some Clod axles to go under that '84 Ford body I bought...) 

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New diff internals arrived this weeks so I managed to get the truck back together for a blast around the garden on Weds.  I didn't get any action shots (because) can't shoot and drive at the same time) but I did get a few pics of my pit helper assisting with tightening up the ever-slackening propshaft grubs.

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Don't lie, that's the pit chief. You are the assistant :P

Sweet custom ride BTW.

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I popped out on a quick bash with a mate last Friday, and realised I hadn't taken this rig anywhere since I rebuilt it back in Feb.  2 minutes into the drive, I remembered why.  I literally can't drive it more than 2 minutes without something falling off.  It's got to be one of the most frustrating cars I own, because when it runs, it's brilliant.

The main problem is the propshafts.  The rear is from an SCX10 and the front is a cheap alloy affair.  The rear in particular is a bit sticky, and on extension it likes to pull off the transmission.  The problem is that the transmission outdrives don't have holes through them, so they rely on a grub screw to lock them in place.  Modern transmissions have holes through the outdrives to accept a threaded pin.  Oddly, this rig has an AX10 transmission, but it must be an earlier one as I'm sure all later Axial drivetrains have pin holes.

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Fortunately I have in my workshop a rather old drill press, which makes jobs like this a little easier.

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Now I can fit a threaded pin

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With that sorted, I turned my attention to the body.  Now there's nothing entirely wrong with the beetle body, but I wanted the roof rack for my Cherokee and it looks a bit empty without it.  Also earlier this year (oddly enough while trying to decide on a body for the SCX10) I dug out a vintage Blackfoot body and, well, cut it in half.

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This should be a perfect donor for a nice classic truck.

I considered gluing it back together, but I figured it would never look right.  Besides, the wheelbase on the bouncer chassis is too long for a stock Blackfoot, and I didn't want to shorten it any more as it already spends most of its time on its rear wheels.

I'm not really that skilled at ABS fabrication, and I was worried I would never do this justice, but sometimes you just have to get on and do things, right?

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Using square section adds rigidity and gives a platform for adding sheet material later.

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You can probably just about see here that the body has shifted a little on the supports and is very slightly bowed.  The more stuff I glue on, the worse it looks.  I may have to unpick the bottom strap and flatten it out again.

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Well anyway - wheelbase is right and proportions are perfect.

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Added a bit more sheet material

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The whole assemblage now feels quite tough.  There's a bit of flex but not as much as I expected.

Given how tight it is where I've added the new material, it's unlikely that I'll ever get in there to finish it nicely.  With that in mind, I'm considering ways of making it look like it's supposed to be split in two.  A monster truck of this era would technically have its motor in the front - the Blackfoot body is a 7th gen F150 which was phased out in '86, but the first mid-engine monsters didn't appear until the early 90s.  However, a set of pipes or something else coming out from the cap behind the cab would hide the mess that I otherwise have to fabricate around.  My other option is to try to 3D print a tidy-looking cover that replicates the side of an F150 body.

In other news - the shocks are not performing evenly.  It feels like one shock has oil in and the others don't.  These shocks were originally on my Budget Bruiser, and I drilled the pistons to reduce damping, but they were never that good to begin with.  I've just ordered some cheap alloy units on recommendation from another member - if they don't do the trick I'll have to get some more CVAs and try to actually make this thing handle.

More to follow next time I have some spare workshop hours :)

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@Mad Ax I love how yoy just cut and shut these bodies to make them work rather than buying new. So good. Would a roll bar help disguise the cut lines maybe? I have 2 black cva short shock bodies and v parts in my spares if you want them to build some dampers. 

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@ThunderDragonCy cutting up the bodies is the easy bit, sticking them back together again is where I struggle!  I put these posts up here to convince me to actually get on and finish them.  Well, that's the hope, anyway.

I'll never achieve the greatness that some of the fabricators here do because I lack the skills and the patience, but every experience is a lesson and maybe one day I'll do something truly fab.

I have considered a roll bar but I'd have to fabricate something as I'd want one that extends further down the bed, the Tamiya roll bars are too short (longitudinally).  However the top of the bed should be easier to get a good finish on - I'll add a 0.5mm sheet over the white styrene, then finish it with a sanding mouse to get it level.  A combination of roll bar and decals should hide the worst of it.

Thanks for the offer of shock parts - I'll drop you a line if my China shocks don't work out.

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I think you need to remind yourself you’re an award winning builder!

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4 hours ago, Badcrumble said:

I think you need to remind yourself you’re an award winning builder!

I just spent 3 mins wondering a) what award I'd won and 2) how you knew about it and I didn't, before I spotted my car stand in the photos. Yes, that was for my Mad Max truck, one of the first custom body hacks I did. 

https://www.tamiyaclub.com/showroom_model.asp?cid=100463&id=15729

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I'd say this and your Mad Max, are absolutely creative... And you're definitely a BUILDER!! 💯👍👍

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OK - bit of a change of direction on this one (again).  I wasn't really enjoying all the body hacking, and got about as far as I know how to go.  Plus there's a huge amount of paint removal needs doing before it can be painted and I just don't have the time for all that dipping and rubbing to get the paint off.

I just happened to notice that the wheelbase matches the JConcepts F150 body on FiftyFifty, so I grabbed the body and plonked it over the chassis, and it looks awesome.  So I went online and ordered another JConcepts body.

Actually I had hoped to get one of the early F150 bodies from JConcepts, but there was no stock anywhere, so I managed to find one identical to the FiftyFifty body.

Anyhoo - my first plan was to remove those terrible scaler shocks and fit some proper coilovers.  I got some ZD Racing dampers from Banggood (recommended by another member here) and they are about as good as you can expect for a super-cheap shock.  Big bore, very stiff springs (admittedly not as stiff as those scaler springs), a little bit grindy and "filled" with a tiny splatter of oil.  I refilled them with soft Axial oil from my ancient SCX10 build, and tried to fit them to the existing chassis.

Unfortunately they wouldn't go on my existing setup - they are very wide, so they catch on the wheels, and the angle was all wrong to the current mounting point on the chassis.

As I had always intended this to be an old-skool monster truck, I figured it needed proper old-skool suspension - high-rise vertical shocks behind the wheels.  So this weekend I got up bright and early, cleared a space on the workbench and started fabricating a chassis extension.

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I started with a sheet of 2mm aluminium.  I've got sheets in 1, 2, and 3mm varieties in stock (I try to keep stocked up since lockdown as there's always something I can think about building) and 2mm felt about right for this.  There is the risk it will bend, but it also doesn't weigh much and is easy to cut (my cheapo aluminium jigsaw blade will go through two sheets of 2mm at once).

I removed the Axial chassis plate from one side of the rig, marked the holes where I wanted my extension to sit on the bracket, and drilled the sheet.  Here it is bolted up against the chassis.

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I wanted to give various options for shock mounting as I wouldn't know what would work best until I start running.  Plus I didn't want each shock mounting option to come with an associated change of ride height.  The solution was to position the truck with the axle in what would be the fully-extended position, stick a scribe through the shock top, and mark the radius it makes on the sheet.

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I then marked out some mounting holes at 10mm spaces and drilled them in the drill press.  Then I marked up another sheet of 2mm allu with 2 of the chassis plate holes, drilled, bolted to the existing sheet, and used that as a template to drill the rest of the holes.  This is how I can be sure that both plates will be identical.

Here it is mid-drill.

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With both plates drilled, I can now flip one of the plates and re-bolt them together, then use the existing holes as templates to drill the new holes for the other end.  This is how I can be sure my plates will by symmetrical front-to-rear.

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Next I scribed the cut-line at one end of the plate.  I used the shock tops to make sure there would be some twizzel room for the shocks when fitted.

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Cuts were made with a mix of jigsaw, hacksaw and junior hacksaw, and tidied up with a file to get a rough shape at one end of one sheet.

Making identical and symmetrical chassis plates is the same process as for getting the holes right.  Bolt the two together, mark the cut line, remove, cut, re-bolt and file into the final shape.

Then to make the symmetrical other end, unbolt, flip the plates, re-bolt, re-mark both plates, remove, and cut both plates.  Then bolt back together and use a file to smooth the new cuts up to the existing plates, which have the correct final shape.

Here we are mid-cut:

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Here we have two plates, one cut and filed, one not.  A file makes both plates identical.

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thus:

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Drawing around the filed plate onto an uncut plate

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et voila:

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Finally, one long cut with a jigsaw through both plates (while bolted together) gives us a neat cut across the top.  I left a fair bit of space at the top as I may need to add reinforcing here.

A file across the top make a nice flat surface.

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2mm alu plate isn't exactly heavy, but it's mounted high up on the chassis and I didn't want to upset the weight distribution too much.  So I used a hole cutter (actually for wood, but it will cut alu plate if turned slowly enough) to cut some relief in the middle of the plate, where it doesn't need so much strength.

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Both plates removed and the edges given a final filing to remove any burrs and sharp edges

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And mounted:

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Alu tube and M3 rod forms a cross brace

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More than enough articulation for an oldskool monster

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Ready for a test drive

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FiftyFifty lid plonked in place for a rough idea of how it might look

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So - how did the test-drive go?

Reasonably well, I suppose.  For some reason it felt a fair bit slower than it has on previous runs - the reason this truck has got so much attention is because it's always been such fun to drive.  It just seemed to feel a bit sluggish last night.  The pack was only partially charged, so maybe that had an impact, and my grass has got quite long, which probably slowed it down also.  Otherwise, it was fun.  However there are some issues:

  • Shocks feel too stiff - I have moved them to the most inclined position but when dropped, the truck bounces on the tyres, not the springs.  This is a drawback of buying cheap shocks, I might end up fitting Tamiya CVAs instead
  • Geometry is not good - the front axle rolls badly under compression - the connection point on the servo mount is too far back; not sure what the solution is
  • Wheelbase is too long - to compound the above issue, I'll need to shorten the lower links a bit.  This has probably come about because I have lowered the ride height a little to make the lower links closer to horizontal

And there are other jobs still to do:

  • Make body mounts
  • Cut and mount body
  • Mask and paint body
  • Come up with a name, design and print graphics
  • Make a battery tray
  • Reassemble and race

Further lockdowns notwithstanding, I hope to take this rig to Robin Hood Raceway for a Tamiya Junkies meet in just under a week's time, so my evenings this week will no doubt be filled with (at the very least) making some body mounts and painting the body

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OK - so another sort-of-update here - I have a secondary role at work as a mental health champion (that's a sort of first aider for mental health problems) and for a company-wide production on good mental health, we have been asked to make a video of our "happy place" - which could be just a quick video of "this is my kitchen, it's where I bake my cakes" or a quick introduction followed by some footage of the actual baking process, which the producers will munge together into a sped-up montage ("ooh, we need a montage!").

My first instinct was to film myself in my studio, working on some bangin choons, because everybody knows bangin electronic music is way cooler than playing with toy cars, but the company have decided to throw this on us last-minute and they want the footage in by this Thursday :o 

Given that I want this truck to be half-finished and at least bodied and driveable before Saturday for the Tamiya Junkies meet (assuming we don't have another knee-jerk reaction to the 'rona), it made sense that I film the final stages of making the body mounts, painting the body, and applying decals.

So I was up at 6am today (admittedly it took me an hour to clear the workbench, set up the camera and lights and work out my introductory speech) and did an hour's filming before I had to stop for the 8am start (I'm currently writing this update while waiting for a 30-min test-run to complete).

The downside to this is that I don't have time to take still pics while I'm working as there's a lot to get through before the Thursday cut-off.  At this rate I think I will be painting the body during "coffee breaks" tomorrow morning...

The upside is that I'll have loads of footage to make my own montage, and if I don't get buried under the serious hard work involved, it might kick-start me into making more videos.

More updates this week ! 

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So - been a bit of a crazy week, burning some mornings and lunchbreaks and evenings to get this rig ready, but finally the videos were sent off to my workplace today.  I think I went way overboard (they asked for a quick intro and a few seconds of you doing something, I sent over 6Gb of unedited video), but the project leader was really pleased (and very surprised, I didn't tell her what I was doing, only that I was close to finishing a project and would be happy to video it for them).

Anyhoo - that means I didn't have time to take any still pictures or do any updates here, so here's a belated update:

To add some rigidity to the 2mm alu, and to provide a flat surface to mount my body posts on, I used some aluminium angle.  I had some offcuts from a jig I made a while back which were just long enough.

They are bolted to the chassis plates with 6 machine screws each.  Body posts I think are spares from a CC01 parts sprue.  I'm running low on body posts of all varieties but especially these surface-mount ones.

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