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EDIT: I have had a change of heart and updated the project name.  I'll think of something later.  I want this project to be an escape, not a reminder.

 

Well, anyway, here it is.  This is the first of my isolation projects and possibly a long-enough one to keep me busy for the first few months (especially as I'm still working full time and still have to spend time with my family).

I first bought this rig back in the mid-00s.  I would have been a very expensive treat to myself back then, not just the huge kit but the 4 channel radio also, and I remember being a little disappointed in its general clumsiness once assembled.  After some adjustments here and there I eventually converted it to Clod axles and ran a 14.4V setup using a HPI speedo and modified GT-550 motors.  It got aftermarket shocks and extended bottom links, and, after forever breaking plastic rod-ends over the most insignificant bumps, got consigned to the loft to stagnate.  At some point the Clod axles were scavenged for the Full Metal Jacket project and the rest was thrown in a plastic tub for storage and forgotten about.

At the end of 2019 I felt my love of Monster Trucks returning, and 2020 began with me watching Triggerkings videos on Youtube.  I knew I couldn't afford to build a full-spec race rig (and nobody races MTs here in the UK anyway), but I could at least do a good tribute.  Plans were hatched.

Actually, I bought myself an Axial SMT10 Raw Builder's Kit from the store front at Wheelspin Models on 13th March.  I thought it would be a good project to throw together while the world was in the grip of the CORVID-19 slowdown.  Back then (barely over a week ago) it really did feel like no more than a slowdown.  How things change!  Well, anyway, by the 16th things were looking different, and I went online to buy a body for my SMT10.  That's when I noticed the stock SMT10 actually has a really long wheelbase.  I usually make my own custom links to shorten a wheelbase, but I can't do that if I want to keep the shocks on the links, as standard, and as most of the racers use.  I found a short wheelbase conversion kit online but it's in the US and not cheap.  I decided it was just a bit out of my budget considering the slowdown in the economy and the uncertainty of the remainder of 2020, so the poor SMT10 was shelved.  (OK, I could build it stock with my chosen body and shorten it later, but I won't know where to cut the body post holes until I've got the shorter links fitted.)

So - little diversion aside - a 1993 JConcepts F250 Crew Cab body was ordered for the TXT-1.  As the chassis replicates monster truck designs of the mid-90s era, I figured that was a good shout.  (The SMT10, with its full cage, will get a mid-00s body).  The F250 was partly chosen for its 12.5" wheelbase, partly for its vintage and partly because it was UK-stocked at the time - although I had to hunt around for one.  Super-fast delivery - it was ordered on Monday and on my floor on Tuesday.

With the body in hand, it was time to open up the box of bits and see what I needed to get it all back together again.

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I dug through my spares boxes and found most of what I need to rebuild the truck in stock trim.  I'm missing one of those square spacers that is bizarrely needed to space the transmission upper mount away from the frame.  I don't know why the transmission mounts weren't just made the right width top and bottom.  Maybe something else was supposed to go in there?  No bother, I cut a new one from some aluminium bracket that already had a 3mm hole in it.  I'll tidy it up for the final build later.

Without much of a better idea, I decided to start with a full strip down.

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The frames and plastic parts got a dunking in some warm soapy water before the frame started to take shape again.

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Ooh, subscribed.

I've got a very similar box with a Clod project in it. I've been collecting parts for it on and off for the last 7 or 8 years, and you've just reminded me about it. I was going to build a Clod based monster using an HPI Wheelie King chassis i have. I think now might be the right time to dig it out and have a look.

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At this point I had intended to remount the axles on the stock links, but at some point in the past I had switched to a custom top-mounted servo bracket and I had chopped up the ridiculously-large standard axle mount / servo mount / diff guard assembly.  I suppose I had wanted to raise the truck by moving the bottom mounts to the top of the axle?  I don't know why I thought that was a good idea.  Anyway, I had chopped up the standard axle mounts to do that.  I might have used what was left to rebuild a near-stock truck but at some point during a teardown some of the parts were lost.  Normally I'd notice something like that lying around, so I have no idea where they went.  I guess once I'd switched to Clod axles I must have lost interest in the TXT affair.

I figured I can make some new axle mounts from alu square bar, but I didn't have any, so I placed an order on ebay (arrived today!) and set to stripping down the axles instead.  A good job I did, as I had previously locked the diffs with epoxy resin and have since learned that locked diffs doth not a fun monster truck make.

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It took a couple of evenings to prize apart the diffs and scrape off all the epoxy.  I had to clamp some of the gears in pliers to get the worst off, which has marked them.  These diffs may not be the smoothest any more, but they turn.  I've added some rounds of blu-tac to limit slip.  Quite a lot of blu-tac, in fact, as this is a torquey truck with heavy wheels.

Use in wet conditions followed by being dumped up in the loft haven't done the hardware any good.  All machine screws will be replaced with stainless hex bolts.  Unfortunately I don't have any stainless self tappers in stock but I'll probably go around and replace them later.

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Axles reassembled.  I will probably refit my top mounted servo for now but I'll have to come up with a better solution for hte long term, as there is a visible split in the right-most screw hole on both axles.  My flat plate design puts too much twisting force into that screw.  I can 3D print something that will fit neatly over the top for a straighter load, but I don't have any tough resin to print with so it will be a semi-functional prototype only (in that I expect it will break in use).  That said my Clod servo mounts are holding up well enough on the Mod Clod - one has cracked but possibly due to being a bit too small.  So maybe it will be OK if designed with thick enough material.

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That's all for now - I didn't have any workshop time at the weekend due to chasing a toddler around, but my company is asking us to take half our annual paid leave allowance before the end of June to help with the crisis.  (Actually they're just trying to avoid everyone rush-booking their full allowance in the final part of the year when the economy restarts and the company should be looking to regain its strength).  I plan to spread my leave out so I lower my chances of being off work during a period of enforced lockdown.

I do have some workshop time tonight and now that my live gig in May is officially cancelled, I'm not in such a rush to finish my new show.  I'll maybe spend an hour or two looking at axle mounts.  If I have enough angle bracket I'll make a jig to hold the chassis and axles and build the links around.

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I'm looking forward to seeing this Crew Cab shell.

Hope you and your family are staying safe 

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Dude much need for pictures!

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FYI I did a similar rebuild a couple years back. You can order basically all the parts from your Tamiya disbributor as Tamiya Japan still produces them in small batches. The only thing that wasn't available were the hop-ups (which are LHS item only, not distributors). Although I did not order the chassis or rods but I ended up ordering all new plastic part trees, new ball nuts/studs. Basically I ended up with a new TXT-1 

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Just a quick update - I had hoped to get more done on this project but I've been a bit under the weather recently, so my evenings have largely been spent on the sofa catching up on TV.  I'm hoping to have a day to myself on Sunday to get a bit more done and catch up with a few outstanding photos :)

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UPDATES!

6 days split between working from home and childcare finally gave way to my first day of lockdown freedom - the chance to go into the workshop at 7am and not emerge until bedtime.  It's strange to think I didn't get a bit more done to be honest, I was on the case for a good few hours, but I had a lot of trouble drilling holes centrally and ended up throwing away 6 bottom brackets before I made 4 I was happy with.

So - as I mentioned above, my stock TXT axle mounts / servo mounts / diff guards were cut up long ago and the parts lost, so I needed to make something new.  For the bottom mounts, I used some 10x10 ally square bar.

Here are the best 4, two rough-cut, two part-finished.  I bolt them together like this so I can file them as one to the same profile.  That's where the bulk of my day went.

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Clamp them together in the vice and file away!

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fin

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For the top mounts, I used the same bar stock but made the sections longer.  This is only a prototype so I only made 2 of them.  I got through so much 10x10 bar that at this rate I'll have to order some more before May :o 

Here they are, rough-cut and not filed yet.  My plan here is to put some 3mm ally plate across the bars and mount the servo on them for a BTA steering setup.  It looks like it should just about clear everything critical.  Would be much easier with a low-profile servo but I'm not so sure a lo-pro servo will handle the weigth.

I haven't trimmed these axles for greater steering clearance like I have done with the clod.  I might come back to that later depending on how the first drive goes.  I might have to rethink the steering link for greater throw.

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Next trick was to make a chassis jig.  In the past I've just thrown my chassis together by eye but always end up with something being off.  I figured this time I'd use some scrap wood I had lying around and do it properly.  Wheelbase is 12.5"

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I want to keep the bottom links almost horizontal like a racing truck.  Suspension travel will be reduced but this isn't going to be a crawler.  Articulation isn't everything.

Anyway, after adding my triangulation piece to keep the jig true, I realised these scraps of wood were just the right height to give a near-horizontal bottom link.

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And here it be - chassis resting nicely in its jig

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With all that woodworking done, I had just enough time left to cut two links.  Here they are.

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Looking back at htese photos now, I realise I may have made a slight miscalculation in that I lined the centre of the chassis up with the cross pieces, but I didn't actually take care to mount them centrally.  So at the moment the front links (to the right) are probably slightly longer than the rear links will be.  I'm not sure if this is going to be an issue and if a rig should have uneven links, I'm not sure if it's better they are longer at the front than the back.  I guess longer rear links means less inclination to wheelie but longer front links might mean less inclination to lift a wheel.  Anyway, it's not a big deal, but those links are about as tight as they'll turn so I probably can't make them shorter without taking them apart.  Alternatively I cut the rears the same as the front and accept the final rig will have a slightly longer wheelbase than planned.  Actually the body is listed as 12.5" but measures a little longer than that.

More to come - I have a free night tonight but it's already 8pm, it's absolutely freezing in the workshop, lockdown life is taking its toll and I might just bury myself in Elder Scrolls Online for a couple of hours...

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Quick update - I got an hour in the workshop on Tuesday night to look at the upper links.  Here I have a bit of a problem with my new geometry - the standard upper link mounting point is now too low on the chassis and the angle would be all wrong.  I figured I could use the holes used for the cross brace but these are too close to get a vertical rod-end on - there isn't enough angle in the RC4WD rod ends I'm using.  So to mount them horizontally, I've replaced the cross brace with a piece of alu bar.

Right now it's only held in place with some dowel - I'll need to tap threads in the bar.  A new M3 tap arrived yesterday so I'll do that tonight and fit it up properly.

Downsides with this geometry:

  • The bar may work loose in operation
  • Travel on the RC4WD rods is limited
  • Transmission will need to be inverted
  • Potentially not enough triangulation to reduce lateral axle movement

I'll probably test-fit properly tonight and see how it feels.  This rig is going to have pretty minimal suspension movement anyway as there's only about an inch of clearance between the top of the axle and the chassis, so it might be OK, but I want it to be sturdy and the alu bar feels like it will be an annoying point.  I'll probably have to torque it up so tight I strip the threads...

Another alternative is to change the mounts on the axle.  They still need to be central or there won't be enough triangulation (unless I went unorthodox and had wide mounts on the axle and narrow mounts in the chassis...)  I might see if I can get hold of any angled rod ends, but delivery may be a problem in the current climate and this project is taking loads of space so I'd rather finish it than shelve it.

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Let's see how things look tonight...

 

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Those are the sort of thing I need, but I need them in M4 and with longer plastic bodies so I can get more thread in them.  I regularly bend even M4 allthread rods on my Mod Clod, I wouldn't like to run M3 rods, although a little plastic boss like that would probably strip out before even an M3 link bent.  Thanks for the suggestion tho :)

I think some kits do have M4 links with bent rod ends but off-hand I don't know what kits they are or what spares to order.

Anyway- made a bit more progress last night.  I tapped the threads in my crossbar and fitted the top links.  There's a surprising amount of travel and the links don't bind.  I also added some shock links to get a feel for the whole assembly when sprung, although I will have to make longer links for the finished product as these set in what should be the droop position when fully laden.

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I kept the top links shorter at the front to add a bit of caster angle

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full compression, no shock links - the axle mounts touch the cantelivers

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Full droop - the top links run out of articulation due to being horizontally mounted.  Allowing this much droop might cause the top link rod ends to pop off the balls, or might cause the cross brace to come loose.  I can control maximum droop by adjusting the shock links once the spring tension is set.

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articulation

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I thought I'd got some photos with the shock links fitted but obviously I haven't.  I'll be back in the workshop tonight so I'll get some more.

I also had an hour on the rig this morning - I fitted the rear axle mounts and bottom links and was part-way through tapping the rear cross brace when I decided to stop for breakfast and work.

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Bit more work tonight.  Both axles fitted, shock links attached and wheels fitted just to see how it looks.  Transmission reinstalled upside-down.  TBH the stance looks pretty aggressive, I really like the look of it.  TXT body thrown on just to get an idea of how the finished truck might look.  Currently there is no droop at all - more weight yet to be added to the chassis.  Once I have some droop I will lengthen the shock links to set the ride height.

There are some issues - current transmission position means the propshafts will be of uneven length, but also means the rear prop will probably foul on the upper cross brace.  I might be able to shift the transmission forwards a little later, or I might have to rethink my cross brace design.  I'm not 100% happy with the top links.

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Yes, those original silvercans are actually rusty.  I guess this one was driven on the beach before it was put away as lots of other screws are rusty too.

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I like my truck bodies mounted low, but I don't like to lose too much detail around the arches.  I'll have to see how well the JConcepts body fits.  Stock body on lowest setting looks cool but fouls the arches on compression and lock.

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Despite the low stance, the horizontal lower links, and the complete lack of droop, it will still articulate enough to get a 330ml can under a wheel.  That's pretty good, IMO.  More articulation to come when I have some static droop dialled in, although it probably won't need it all for the duty it will get.

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Fascinated by this @Mad Ax. I G ave no idea about the original kit or linkage suspension, but i am loving your work. The motors seem pretty low and exposed down there. Are you going to build a guard, or figure out a solution to flip it back up? 

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@ThunderDragonCy it might be a good idea if I lift the transmission just a little to get a bit more clearance.  The finished product will have some form of brushless motor and I'll probably make a guard as well.

The downside is that lifting the transmission will bring the propshafts even closer to the cross braces.  I think my current solution is going to have to be abandoned.  If I redrill new holes further towards the middle I should get a better angle on the links.  I was trying to avoid redrilling the chassis but at this point it seems inevitable.

I was also looking at previous solutions and noting how people often mount the lower links on the top of the axle instead of the bottom.  It would maintain the horizontal link geometry while bringing the top links closer to the original mounting points.  However it will raise the CoG and IMO takes it way from the low-slung racing truck that I'm going for.

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OK - updates!  I had the entire of Sunday in the workshop again, so I decided I'd crack on and get this chassis together.  First thing was to sort out the top links, which I wasn't happy about.  I removed the transmission and utilised the upper transmission mount holes for some longer top links.

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Transmission propped in place to prove it still fits

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Should now be plenty of clearance for prop shafts

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