Element Trailcrawler - Nuts and Bolts Project

[Mad Ax 10785]

What do you do when there's only 2 Workshop Sundays left until Revival, your Revival cars aren't finished, you've already got a scaler chassis project on the workbench, and you're out of money for the month?  That's right - you start another scaler project!

To be fair, I have my reasons for doing this right now.  First, I had to get all my Element Enduro parts out of storage to get started on the Ford Raptor race truck (see other thread), so everything is easily accessible right now; second, if I get this to somewhere near finished it can go on a display shelf somewhere instead of going back in the box as a pile of parts to maybe come out again someday in the distant future; and finally, because I actually have no need for this truck at all, but my daughter likes the colour, so she's going to have it.  If she's going to start driving a full-size crawler rig in the woods and maybe join me on some proper events later in the year, I'd rather she has a proper capable crawler and not some cheap RTR that I'll have to tow over all the hardest obstacles.

And my reasons for that reason are also manifold: 1) when I was a kid I often had to settle for second best, and I often struggled to compete with inferior hardware, so I want my daughter to not be held back by stuff that isn't up to the job, and 2) having inferior hardware became a go-to excuse for not achieving stuff, and I want my daughter to know that the truck isn't letting her down, and if she keeps trying and keeps learning, she'll be able to do anything I can do with my trucks.

All of this assumes she ever actually drives it.  Sometimes I think she says she wants these things just to please me 

Anyway - what is this build all about?  Well, it's a nuts-and-bolts build of all the Enduro parts I've got left over after making a 6x6 and a Raptor race truck out of 2 Scale Builder's Kits and a Trailrunner RTR.

Let's get started with the chassis.  I believe this was the SBK2 chassis, because it has the SBK2-style shock towers.  It's been sitting in a box like this since the middle of last year.

This was supposed to be a nuts-and-bolts build, but already it's throwing curve-balls.  First ball is the servo mount.  The SBK2 servo mount was used in the 6x6, this is an SBK1-style mount.  Note the ribs next to the screw holes.

The SBK2 shock hoops don't have the panhard rod mount moulded into them, instead the panhard rod goes onto an adjustable part that mounts in the chassis rail.  Nuts are supposed to sit where those ribs are.  So, I had to cut and file them off.

SBK2 panhard rod mounting bracket.  Now fitted alongside the SBK1 servo mount.  This will come back to haunt us later.

I used custom links for the 6x6, so I had a full set of SBK2 cranked links left over.  The wheelbase is the same as the Trailrunner, which is convenient because I want to use the Trailrunner body.  Front axle now fitted.

[Mad Ax 10785]

I had a spare set of links for the rear end, but didn't have a spare set of cranked rod ends.  The only 4mm rod ends I had were RC4WD, which are a bit longer.  Fortunately, I also had a full set of links from the SKB1.  The SBK2 includes those lovely dark-coloured cranked links, but only for the 313mm wheelbase - the SBK1 comes with enough links to make 3 different wheelbases.  Among the selection was just the right length of rod to make a replacement upper link set using RC4WD rod ends.

Both axles fitted

Not bad for a lunchbreak's worth of work  

[Mad Ax 10785]

A quick sneak preview on luncbreak 2: shocks, wheels and tyres!

Naturally I want my daughter to have the best, so a cheap set of rubbish tyres won't do.  I went rooting around and found these Proline Class 1 tyres, which are a very capable tyre.  Pre-glued to some boring but fairly scale looking Fastrax wheels.

Shocks are some very old scale-looking but terrible-performing units.  Zero damping and way too hard of spring.  They're only on there to hold it up right now, I'll probably order some KYX shocks next time I'm doing an order.

Then I dropped on the Trailrunner body.  It's actually a fairly accurate replica of a Toyota 4Runner, and it's quite big - probably closer to 1:9 scale.  The Element axles are wide, but these wheels don't fill the arches, they're all tucked underneath like an Austin Metro.  We'll need to improve that later.

Wheelbase should be the same as the Trailrunner, which comes with the IFS kit, but on this angle the front axle looks just a little too far back.  Also the wheels rub on the steering arm, so will need spacers unless I swap them for something else.  The tyres are glued, though, and I'm not sure I can get the glue off.  These tyres weren't cheap, so I don't want to ruin them.

Loads more to follow on this including much more pics, but I have to go cook the dinner now  

[Mad Ax 10785]

OK, dinner has been cooked and plonked in front of the relevant individuals.  I'm back.

My original plans for this spare chassis were to turn it into a capable crawler all of my very own, but alas I don't need one.  However, I did go as far as buying many of the essential parts for it, such as a servo.  This one has a beastly 26Kg of torque at 6V.

Instructions say to mount the servo from above, with a 7mm spacer on the steering rod, but IMO that puts way too much twisting force on the servo horn.  There's enough space to mount the servo up from underneath.

Everything clears on full compression.

And I need only a small 6mm spacer to get the right angle on the steering rod.

[Mad Ax 10785]

Now, I want to take a moment to talk about how well spec'd the Trailrunner is out of the box.  It comes RTR, with a neat little set of tyres that feel like they should be OK to get started with, a modern body with moulded door handles, wipers, arch extensions, lip spoiler, rear bumper and detailed front grill, and a chunky and what feels to be reasonably good radio system.  I can't vouch for the ESC, motor and servo as I haven't tried them yet.  And we know that the Element Enduro is a capable platform with loads of scope for upgrades and mods.  All this for just 250 of your British pounds.

But what you also get in the box is a spare axle tube, various spare rod ends, and the short body mounts in case you want to fit a pickup body.  Props to Element for not locking people into the 4Runner body.

And finally, you get some other cool moulded scale parts to fit at your own leisure.  A proper off-road style front bumper, a snorkel, wingmirrors, and a roof rack!

Everything is made from soft, pliable, bendy plastic, so it might look a bit wobbly when installed but it should handle the scrapes well.

The front bumper is a neat thing.  You can trim off the centre part of the lexan front bumper, and just install the centre section, or you can go full expedition and take off the lexan bumper entirely in favour of a full-width rock bumper.  The lexan bumper can be removed non-destructively, but the arch extensions need to be sawn off.

All of this is great, but unfortunately it makes the front axle look even more pushed back than it did before.  To make this rig work, I really need to move that axle forward.

And I really, really need to sort out those wheels!  

[Mad Ax 10785]

In fairness, much of the poor stance comes from having the wrong shocks installed.  They're too stiff, and there's no sag, so it looks like it's standing on tiptoes.  Once I've got some better shocks on and the wheels spaced out, it should look a lot better.

Here's where it was during today's lunchbreak - front axle sitting too far back under that big bumper:

The fix for this involved removing the 2 lower links and the upper link and replacing the cranked rod ends with RC4WD rod ends.  This adds a few mm to the overall length of the rods, and moves the axle forwards without having to cut any new parts.  That's better.

There is, however, one snag.  That panhard rod mount has come back to haunt us...

[Mad Ax 10785]

So - what are we going to do about that?  Well - it's a tricky one, and no mistake.  The obvious answer is to move the entire front assembly forwards - there's probably space in the chassis rails to do that.  but if I move the front shock towers, I have to redrill the body post holes - and I don't really want to do that.  I can't move just the panhard rod mount because it'll want to bolt up where the shock hoop goes.

It wouldn't be hard to make a new panhard rod mount (at least the metal part of it) which has the mounting holes angled further forwards, but I'll have to watch for clearance issues with the steering link.  Moving the servo means moving the servo mount, which is also the mounting point for the shock hoops, so I may need to make some more mods there.

So - this has now turned into a less trivial build than I expected, all because I swapped out the front bumper.

There's still loads of fun to have with this rig, though.  As well as shocks, I need some new shock mount plates that go into the shock hoops, and some new driveshafts.  I also need to mount the servo winch.  Yes - I bought a winch for it, too!  Having the right bumper and a neat mounting point already on the chassis is a major bonus, so it should be a quick job.

Then there's cosmetics.  This is technically my daughter's rig, but I'll get started with the stickers.  The kit includes some neat sport graphic options for the hood and sides, which should detract slightly from the bulbous sort of look it has now.  Maybe I'll sticker on some shut lines too.  I have an intense dislike for smoked windows, IMO they make it look like a cheap toy, so I'll have to try to pull them off without damaging the details around the wipers.  If I dared, I'd trim out the smoky parts with a scalpel and peel them off, but I'm sure it will score the lexan underneath and next time it has a heavy roll all the windows will drop out.  There is a company in the US that makes a clear decal kit, but for the cost of postage, it would make more sense to mask and paint the window trims back in.

Another job I should do - which might neatly go alongside the window trim paint - is put some solid paint behind the body.  There's too much light bleed right now, and it doesn't look right.  Silage tape (like duct tape but black) actually works really well and gives the body loads of protection, but won't make a neat window trim surround.

I'm not sure if I'll put more work into this over the next few weeks, or do what I promised and stick it in the display for a while until Revival is over.

[Badcrumble 4422]

Your panhard rod issues feel awfully reminiscent of my little Jeep. There is that ripple effect when you make a change to the set-up. 

Hope you get it sorted!

 

[Mad Ax 10785]

2 hours ago, Badcrumble said:

Your panhard rod issues feel awfully reminiscent of my little Jeep. There is that ripple effect when you make a change to the set-up. 

Yeah, these projects seem to cause that kind of thing.  The Enduro chassis is great for out-of-the-box customisability, and although it's on its longest setting, it would have been way easier to extend it at the rear than at the front.  But then the body posts would have been all wrong.

I had another look at it this morning, and I'm pretty sure if I make a new panhard rod mount to move it forward then it's going to interfere with the steering link.  I can't move the panhard rod mount on the axle, because it'll interfere with the shock.  So it looks like I'll have to move the servo mount forwards.  There may be enough space in the chassis using the standard servo mount, although I'll have to make a few other changes to accommodate that, but if there isn't enough space then I'll be making a custom servo mount.

It's a frustrating amount of work for what is supposed to be a simple nuts-and-bolts build.  I don't actually mind doing it - actually I enjoy it - but this one was supposed to be finished and on the trails soon.  Maybe even before our holiday to Wales in 2 weeks, it would be nice if my daughter and I could go trucking over some real mountains.  But I still need to get some new shocks and driveshafts before it can turn a wheel on the rough stuff...

[OldSchoolRC1 1090]

I've run into that as well building my EctoKeeper, that molded in truss can cause some issues. After puzzling a bit, I remembered the angle of the axle and the angle of the C-hubs is completely independent of each other. I rotated the axle back with a slightly shorter upper link to get that truss out of the way, then remounted the C-hubs a notch forward to keep the kingpin angles the same. I think I added a small spacer on the lower panhard mount too.  It took some finagling, but I got it all to clear. Think I ended up pushing the axle out about 8mm or so total. 

Completely non helpful pic - definitely not worth 1000 words! Can see the angle of the diff cover is slightly backwards at the top. Pinion angle out back is fine - slight tilt down, but no problem.  

[Mad Ax 10785]

@OldSchoolRC1 that's a neat idea, thanks for that!  It took me a while to see what you were doing - but now it makes perfect sense.

I literally just logged on here to say that I literally just realised I could drop the panhard rod and 4-link the front end.  I've got all the parts I need to do that in about 5 minutes.  Not sure how bad the bump steer would be though, I guess I'd just have to try it and see...

[Badcrumble 4422]

At least 4-linking would get you there for the holiday - you could re-visit it when you have more time.

[87lc2 2853]

I got fed up with that panhard and chassis mounted servo setup on my SCX10 II - ditched it for an axle mounted servo and 4-link setup.  Truck performs much better now.  I guess these setups can work when done right (my Redcat Gen8 isn't too bad), but overall seems like they're just overthinking it.  Causes all sorts of weird clearance and geometry issues. 

[Busdriver 6517]

Can someone explain what the advantages/disadvantages of 3 link + Panhard rod v 4 link font end are. The reason I ask is because I bought an Injora front axle with open diffs for my SCX10 ii and the Panhard rod fixing is on the wrong side so I can’t use it. The chassis mounted end is part of the shock mount and is handed so won’t fit the orher side! I had a spare upper link that came with the car so installed it as a 4 link and ditched the Panhard rod all together. I haven’t had a chance to drive it yet?

[87lc2 2853]

I honestly don't know?  I can't find anything positive about it on an RC but there had to be a reason.  Maybe its necessary when mounting the servo in the chassis?  Seems all trucks with that setup mount them there.  I'm sure someone here knows...

[BuggyDad 6368]

9 hours ago, Busdriver said:

Can someone explain what the advantages/disadvantages of 3 link + Panhard rod v 4 link font end are. The reason I ask is because I bought an Injora front axle with open diffs for my SCX10 ii and the Panhard rod fixing is on the wrong side so I can’t use it. The chassis mounted end is part of the shock mount and is handed so won’t fit the orher side! I had a spare upper link that came with the car so installed it as a 4 link and ditched the Panhard rod all together. I haven’t had a chance to drive it yet?

Interested in this too. If the servo is to be chassis mounted then the panhard parallel to the steering link is required to avoid bump steer. Is unsprung mass the main reason to go this route rather than mount the servo at the axle? Maybe ground clearance or other clearance issues too? I'd guess unsprung mass isn't much of a concern at crawling speeds? 

[Mad Ax 10785]

I think @BuggyDad has the right of it - if you chassis-mount the servo, the panhard rod keeps the axle moving on the same path relative to the servo, so bump steer is reduced.  I've not tried a chassis-mounted servo with a 4-link yet, I'll find out how bad it is in the next couple of weeks, maybe.

As for why chassis-mount the servo - I think it's a matter of scale realism, which has become so important in crawling over the last decade (although arguably it's fading now as LCG rigs seem to be the next big thing).  The chassis-mounted servo, and the panhard rod, are features of so many 1:1 trucks.  I'm not sure how many trucks outside of monster trucks and agricultural vehicles have steering mounted direct on the axles.

Clearance is another possible issue - having a bulky servo mounted on top of the axle means you have to leave a lot of space between the chassis rails.  I never really appreciated this until I tried fitting a servo winch to the CFX-W, which has an axle-mounted servo.  So many times I thought I'd got it done, then found another angle where the steering servo would catch something.

I don't know if I can axle-mount a servo on the Element axles, because of that same top rib that's causing problems with the panhard rod.  An alternative is to mount the servo back inside somewhere and mount a crank up front, but that's stretching into realms of custom-building that I was hoping to avoid on this project.

[Busdriver 6517]

Bit of a newbie’s comment but by bump steer you mean that if, with the wheels dead ahead, you compress the suspension the front wheels turn on their own, or at least without steering input?

[87lc2 2853]

I tried to run a chassis mounted servo with a 4-link and it didn't work.  Well, it didn't seem like it would work, never got the truck off the bench because the geometry seemed so poor.   Could have just been me though    I prefer the simplicity and function of a 4-link and axle mounted servo, as unrealistic as it may be it just works.  

[OldSchoolRC1 1090]

14 hours ago, Busdriver said:

Can someone explain what the advantages/disadvantages of 3 link + Panhard rod v 4 link font end are. The reason I ask is because I bought an Injora front axle with open diffs for my SCX10 ii and the Panhard rod fixing is on the wrong side so I can’t use it. The chassis mounted end is part of the shock mount and is handed so won’t fit the orher side! I had a spare upper link that came with the car so installed it as a 4 link and ditched the Panhard rod all together. I haven’t had a chance to drive it yet?

Mad Ax is spot on. 3 link and a panhard are used for a chassis mounted servo, and is strictly a scale thing. Basically it hides the servo up in the chassis giving a scale look. 

A 4 link is usually used with a servo mounted axle and is much better from a performance standpoint. But that big old servo on the axle isn't very scale of course. 

Some trucks do use a chassis mounted servo without a panhard bar - CC02, RC4WD Marlin/TF2, etc... they do have some bump steer for sure - can't be helped. It's usually not really noticeable out on the trail unless it's way, way off.  

[87lc2 2853]

True, the bump steer is usually not noticeable on the trail, but I never let a truck leave the bench when its that bad.  OCD at its finest, haha.  

[Busdriver 6517]

Have now found I can use the Panhard rod so can you have a 4 link with a Panhard or should I go back to 3 link 

[Mad Ax 10785]

8 hours ago, Busdriver said:

Bit of a newbie’s comment but by bump steer you mean that if, with the wheels dead ahead, you compress the suspension the front wheels turn on their own, or at least without steering input?

Yes, that is exactly right.  The distance between the steering arm and the servo pivot changes as the suspension goes through its full motion, so the steering angle changes as the suspension moves.

2 hours ago, Busdriver said:

Have now found I can use the Panhard rod so can you have a 4 link with a Panhard or should I go back to 3 link 

No - the Panhard rod will cause the axle to swing slightly outwards as it compresses (maintaining the same distance between steering arm and servo pivot throughout) but the 4-link will maintain a more "perfect" central geometry - if you connect a Panhard rod to a 4-link setup, the suspension will bind because the links are trying to pull the axle in conflicting directions.

[Mad Ax 10785]

Quick update - I had 30 minutes spare after doing all my other workshop today, so I spent 60 of them installing a 4-link to test the bump steer.  It's pretty bad - but would it be noticeable on the trails?  I don't really know.  However there is a corollary that you probably wouldn't notice on a full-size truck but is very apparent on a 1:10 scale - not only will suspension movement cause steering input, but steering input will cause suspension movement.  It's possible that the front suspension will be pretty useless in a tough scenario when there's lot of steering going on.

However, I tried @OldSchoolRC1's method of rotating the axle backwards, and it worked perfectly, meaning I can keep the Panhard rod.  All I had to do was replace one of the RC4WD rod ends with a standard Element rod end, and that gave it just enough clearance for the Panhard rod to miss the truss.  I rotated the steering hubs by one spline.  The axle input is now roughly parallel to the ground, which was pretty much the standard for crawlers until they started getting all technical with rotatable caster hubs anyway, so it should be fine.

I also found some better shocks for the F150 race truck, so I've now got the proper Element shocks back on this rig.  They're very good shocks, so I'm glad to have them back.

Still need to find some driveshafts and order some more shock mount plates but it's fairly close to being a runner now.  We'll be setting off on our holidays in a little over 2 weeks, but I'm racing next weekend and still have a lot of Revival stuff to sort out, so fingers crossed over this one being ready in time...

[Mad Ax 10785]

Bit more progress on this one over the last few days.  I found some GMade aeration dampers that should work well on the Raptor race truck, so I was able to take the RTR Trailrunner shocks off of it and fit them on this trailcrawler hybrid instead.  These AE shocks are pretty good, although the front springs are stiffer than stock as they were supplied to fit with the IFS setup on the Trailrunner.  I have some spare standard springs if they don't work right.

Also a set of aftermarket propshafts arrived off ebay.  They look tough enough and move freely.

Also, when I originally planned on building this truck for myself last year, I spent some spare cash on a decent setup for it - 25Kg servo, 1080 ESC and this Ruddog 16 turn 5-slot crawler motor.  I want this to be a capable rig, so my daughter gets the 5-slot.  Nothing but the best for my scwub.

Sadly I have no idea what I've done with the 1080 (it can't be lost, it was probably commandeered for another project that I've since forgotten about) so this truck gets an old Maverick crawler ESC that I've had lying around.

This rat's nest of wiring will be fixed before it hits the trails, although it did move under its own power for the very first time on Tuesday evening.