Another enduro pre-runner (idea)

[Cuiken]

Minor update:

Best laid plans and all that. So, a delightful idiosyncrasy of the element RC chassis/Stealth X trans is that the motor needs to run CW for the truck to move forward. Naturally, CCW is the 'norm'.

Ordinarily no issue. You'd just swap the motor wires on a brushed/sensorless brushless rig or program the ESC in a sensored rig. But wait... the 10BL120 has no motor polarity reverse function. So, turns out, not really an ideal choice for this project. That said, there's not a lot of other choice out there without importing a MambaX from the US. I'm also not a huge fan of the AXE combo's for non-crawling applications. Tried one in my Wendigo and it was terrible.

So, to make this work I 'think' I can just lift out the whole trans, and drop it back in rotated 180 degrees. This should reverse the motor direction. Unfortunately this leaves me with overdrive on the rear axle (very bad) but I have some spare gears that I can use to convert the trans to have no overdrive (which I think makes more sense on a pre-runner anyway). If I want to add overdrive later, there's a conversion shaft that Element sell. Thanks to those who helped me figure this out in a separate thread.

Only question is, if this works, why Element didn't make this the stock orientation in the first place? It would save quite a few headaches down the line for the truck to run with a standard motor direction.

[Cuiken]

Utterly pointless update:

The car and 90% of parts should arrive today. I can then start trying to figure out if this thing is going to fly at all.

First port of call, can I reverse the trans etc to get the motor to run the way I need....

[Cuiken]

Okay, I think I can now promote this from 'idea' to 'proof of concept'. Parts arrived and I managed to get a few hours over the weekend.

Main job was to measure up and fabricate some new suspension arm and shock mounts. The aim here was to do something a lot like the Extreme RC approach where a set of Axial Yeti trailing arms are slung below the belly of the truck.

Why not use the Extreme RC kit? Well, the stock part from them only covers the 313mm wheelbase and I need ~333mm. I did chat to them and they suggested they could do a custom part but the cost/lead time were starting to get a bit high (like more than half the price of the original RTR car). I also needed to build a mock up to figure out all the required measurements. In the end I did the whole job in ~ 2 hours with some aluminium sheet I found in the garage.

First job, cut down the sheet to make 2, 20mm2mmx110mm bars (for the record, yes, those are my steel toe cap safety slippers just in shot):






Next was to drill the mounting holes (these line up with the 6 holes in the chassis rail) and one hole to which I attached the trailing arm.




Okay, it's not pretty but it did work. If Extreme RC are producing the 'Rolls Royce' version, these would probably belong to the British Leyland school of engineering 🙂

FYI, the tools I used were an small angle grinder, drill and a bench grinder. Really took very little time.

Here they are mounted up:






To get the wheelbase the correct length I found I could simply use the original lower links in place of the upper links and move them back 'one hole' in the chassis rail.

All slung back together:






Some simple mounts knocked up to which I attached the stock shocks:




And finally with the shell mounted. Really happy with the wheelbase. The wheels also fit perfectly inside the wheel arches with zero rubbing.




I set the rear shock height so that the chassis sits level under full compression and the resultant rear droop looks pretty good as a result:




Lastly, check out the insane articulation! Again, no rubbing:




To be honest, I don't think that much articulation is going to be a good thing. If you're eagle eyed you may have spotted that I've already mounted, but not yet connected, a rear sway bar. This will definitely tame the amount of articulation on offer. For a pre-runer though, I think that will work way better.


Ohh yes, and last job was to rebuild the transmission with 0% overdrive and swap it round in the chassis:




Not yet test run it to find out if this actually works.

Lastly, bit of a tip on that rear drive shaft. I bought the 'wheelbase extender' kit from Element as it's a fairly cheap option. Unfortunately, it's only intended to get you from 313mm to 325mm. In order to get all the way out to 333mm I've had to order a whole new drive shaft kit (Element again) from which I can salvage the longer sleeved 'outer'. Combined with the extender kit this will get me a long enough drive shaft. Arguably though, there are better options out there.

[Cuiken]

Mounted the motor and ESC last night and gave it a test run around the kitchen. Still only front wheel drive until the new driveshaft parts turn up but really just wanted to check it runs in the right direction.

Good news (for me at least). Forward runs forwards. Given how easy this was, and that it didn't seem to affect the weight distribution at all, why is this not the stock orientation? Strange.

Anyway, what I gleaned was that it basically runs fine. I only ran 2S, and it was wheel spinning all the time, but I'm still concerned it might be a bit slow. This probably makes sense given it's a 3040kv motor. My actual crawler runs 2800kv in more or less the same chassis and it's not exactly flying.

I'll see how it does once there rear wheels are driven. There's probably some scope for pinioning up a bit but I'll need to be careful of temps. Any tips on getting a bit more safe speed out of this thing gratefully received.

Otherwise though, it's looking good. I still haven't booked up the sway bar and it is delightfully leery in its handling. Really moves like a big old truck. On 3S though I'll probably need to reduce roll a bit so I'll hook it up later on today for another test.

[Cuiken]

Got the driveshaft extension today and took it out for a quick test run (no body shell) on 3S and with a 22T pinion instead of the stock 18T one.

I've also hooked up the sway bar. This was a bit of a fiddle so I'll post pics later.

Anyway, test run was pretty successful. The suspension works an absolute treat. With a heavy 3S 6000mah battery on board, the truck glided over bumpy stuff at full speed and cornered without too much body roll.

Couple of minor 'jumps/whoops' showed the landing to be incredibly plush and properly damped.

Really impressed by how it's working out.

Top speed was still a fraction low but the motor was only a little warm so I'm hoping that I'll be able to get to the speed I want by running a 24T pinion and 72T spur (vs stock 87T). This should get me an extra 30% speed topping out around 13mph (vs 10mph at the moment). I'll give that a bash later.

If that still doesn't do the trick I might spring for a 10.5T (3600kv) motor instead (should give another 20% speed).

So, bit of tidying up to do and then on to the body work!

[Cuiken]

Okay, sway bar fitting:

Since the axle sits ~2cm further back than stock, I needed to move the sway bar mount as far back as practical. This was easily done by attaching the rear mount offset by one screw hole and then drilling an additional mounting hole in the plastic bumper mount.




The upshot is that you get a decent drop to the trailing arm's second mounting hole and the sway bar arms don't foul against the body mounts.




As you can see I made up some drop links from 3mm threaded rod and some spare link ends. I had to do this because the drop links that came with the sway bar were too short to accommodate the new full drop of the rear axle. FYI, the stock drop links are 4.2mm eye to eye and the new ones are 6.2mm. This length of drop link allows for full droop on the rear axle without overextending the sway bar and doesn't foul the body mount under full compression:






With all that installed, you end up with a really nice level of control on the back axle (using the lightest sway bar from the kit).

Appreciate I'm adding tons of detail to this thread. Hope it's not too dull.

From the test drive yesterday I have to say the end result is really pleasing. I reckon this is going to be a top notch fast trail truck and I can recommend building one of these up. There's not much else out there quite like it.

[B-MOW71]

Great job on the fab work to get the trailing arms attached! Nice idea and looks like it will work out great!

Following along to see how it all comes out!

[Cuiken]

Okay, a wet weekend meant loads of time indoors. Perfect opportunity to apply 20 (yes 20) coats of paint to the shell.

The last complex paint job I did was on pretty much the same shell (see below). So, emboldened by previous success, I thought I'd go more complex again (5 colours instead of 3, lots more fine line masking).

Masking took a while.




6 coats of Tamiya PS-2 Red (it's really transparent so needs more coats than other colours I find).




4 or 5 coats each of Yellow and Orange (PS-6 and PS-7).




You'll notice a couple of spots where paint managed to get under the tape. I found it much tougher to prevent this happening with the really fine tape and so many coats of paint. Room for improvement but the overall effect is still fine.


After that I did 4 coats of Tamiya PS-1 white (it covers much better than the other colours), 4 coats of Tamiya PS-12 silver leaf (as backing and for the rear bed, front bumper and tailgate trim) and then, lastly, a coat of matt clear coat on the outside of the shell over the front bumper and rear bed:




The front grill that comes with this body is black (not chrome). It did not look great so I masked and sprayed it with Tamiya Silver Leaf TS-30. I was really surprised by how well that came out. It only took one coat and I was left with a sort of old chrome/aluminium finish. Looks perfect on this truck and matched the other silver areas well too.

I also added the usual cheesy £11 interior which fits this shell particularly well (with a bit of trimming).

With all that, the roll bar and minimal decals applied, it ended looking like this:




I was fairly happy but thought the wheels looked too small. Maybe try some class1 tyres on 1.9" wheels I thought?

Before diving into that though I thought I'd try moving the side bars back out (they were fully retracted) and use their runners to cinch the body in slightly around the middle (I had to trim ~3-4mm off the bottom of the body to do this).

Aesthetics are weird, this minor mod made all the difference. Not sure if it comes across in the pics but, somehow, the wheels look spot on now. I might want to move the rear ones out by ~3mm or so per side but, otherwise, I think it looks great:










I have to say, I think this shell is the bees knees. Absolutely delighted with how it ended up sitting on the chassis with really very little fuss.

I'm not quite done with the build yet though. The extra weight of the battery and shell means the back suspension is now too soft. So, heavier springs are on order. I'm also waiting for a 72T spur gear and the last part of the rear drive shaft extension.

Beyond the basic mechanicals, I want to extend the rear bumper mounts so that the rear Vanquish bumper sits just inside the shell (rather than ~2.5cm inboard as it does right now). This won't end up being visible but should provide a bit of protection for the shell when it tumbles. I have some brass tube on order to help with that.

Looking forward to seeing how it handles once I've sorted the gearing (and this constant bl**dy rain stops for a couple of days).

[smc-93]

That paint job looks amazing. Nice job.

Would you ever consider offering your paint services? I don't have nearly enough patience for a nice clean paint job like that. Especially a complex 5-color paint job.

Sent from my LM-V600 using Tapatalk

[ScaleLifeNewbie]

Originally Posted by smc-93

That paint job looks amazing. Nice job.

Would you ever consider offering your paint services? I don't have nearly enough patience for a nice clean paint job like that. Especially a complex 5-color paint job.

Sent from my LM-V600 using Tapatalk

I would be interested in his service as well! I can never get lexan bodies to turn out good, meanwhile I love doing hardbodies.


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[Cuiken]

Thanks guys, that's very flattering but I think my family would 'divorce' me if I spent any more time in the garage huffing paint fumes

Todays update is simpler. I swapped in the 'blue' springs on the rear and think they feel about right. The shock oil (350CST I believe) might be a wee bit stiff though as the rebound is a bit slow. Easy fix later on.

Irritating miscalculation on my part though is that when I fitted the 72T spur and 24T pinion I found that there's not enough range of adjustment to get them to mesh (about a 1mm gap between them). So, ordered a 75T spur with some 26T and 28T pinions.

As to my concerns about heat, it occurred to me that my TRX6 runs a 3300KV AXE combo and is geared for ridiculous speed in it's 'high gear'. No heat issues there. Pretty sure I'm running the stock 45T spur with a 9T pinion and, I believe, the transmission reduction (inc diffs) is 6.32 in high gear. That would give a theoretical top speed of ~16.5mph which feels about right because it really shifts.

I don't think I can get anywhere near the same final transmission ratio out of a truck using the StealthX box (even with a smaller spur) so I'm guessing it shouldn't be too hot. Again, a quick calc suggests that a 28T pinion and 75T spur should only give 14.7mph which is a good chunk slower than my heavier TRX6 is running. I'm going to be optimistic

[Cuiken]

So I fitted some Class1 tyres onto an old set of Element RC rims and tried them out last night. I'm really not sure which I prefer. Help me out with some opinions...











They give the truck a really different look. In both cases, the back wheels sit a bit too 'inboard' but, to me, the wee 1.55" ones have a sportier appearance. I think it's maybe just that they look chunkier because they're slightly wider than the Class1 tyres.

Meanwhile, the Class1 wheels/tyres, to me, look great in gold and have a more 'off road' kind of vibe.

Polling for opinions on this!

[smc-93]

+1 for the gold wheels/tire combo

IMO, the ERC 1.55 wheels look to small, maybe it's the relatively big tire they wrapped it with but it doesn't look right to me. I thought they looked a little silly even on the Knightrunner

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[Cuiken]

So the 75T spur and 26T pinion turned up on Saturday and I was able to put the whole thing together and take it out for a quick run.

First thing's first, the speed was spot on. 13.5T (~3000kv) motor with the gearing above and class1 tyres (~105mm). Theoretically ~14mph and I'd say that was about right. Right on the edge of what the chassis can handle (especially with a large body shell). No heat issues at all with the motor or ESC and low speed control was surprisingly decent. Handling wise, loads of body roll when corning (to be expected) but also tons of torque twist and loads of torque steer.

Took me a while to figure the latter out but basically it's the bump steer from the IFS interacting with the torque twist from the rear axle under acceleration. As the chassis twists, it loads one of the front wheels causing additional toe in on that side so truck swerves off in the opposite direction. Without the sway bar, I suspect it would become very difficult to drive. I was almost thinking a gyro might be a plan but ultimately went for the Bowhouse IFS upgrade (N2R IFS Steering Rack V2). Cheap shipping from the US with Amain.

Additionally, I needed to make a wee mod to the battery tray to accommodate the larger wheels. With the larger tray in place, the wheels would rub on its corners under full lock and compression. To be honest it already rubbed with the wee 1.55" wheels but it got pretty bad with the class1 wheels. Easy mod with a Dremel as below:




You still get some contact but it doesn't 'grab' the tyre now.

Ultimately, I'm really pleased with the truck. I got a chance to run it on some snow and ice on Sunday morning and it was brilliant fun. The rear suspension is fantastic and it just glides over bumpy stuff in a way that my traditional crawler doesn't. Once I've sorted the bump steer, added a rear bumper mod and, possibly, stepped the wheels out by a couple of mm, I'm looking forward to trying it out on some proper trails.

Just as a very general observation, I'm a bit of a fan of the Element stuff (this is my second and I'm thinking about a third truck based around the gatekeeper kit). You can generally pick up a bargain somewhere and the key components are fairly solid. They are really easy to mod either with home made parts or aftermarket stuff (which suits me). And, they are really nice to drive. There's something very realistic about the way they move over terrain (especially with a bit of added wheel weight). All that said though, they seem to make odd mistakes with all their kits. Just a few irritating features I've noted:

1. On my original crawler (Enduro Sendero) the wheelbase of the truck is too short for the body. In the end I bought the club5 links to sort it out. How'd they miss this?

2. Again, on my Sendero, the wheel rub on the body shell was terrible. Even with smaller tyres you get a load of rub on full lock. In the end I did a load of cutting before the wheels did it for me.

3. On the IFS trucks, you will get the wheel rub on the battery tray (as mentioned above).

4. The IFS has the well known issue with bump steer and over extension that you can sort with the Bowhouse kit.

All this is the sort of stuff (body fit, wheel rub etc) you expect if you're modding an RTR or doing a 'ground up' build. It seems odd from an RTR out of the box. You just don't get any of these issues with a TRX4. It's a shame as these are not issues that you might associate with 'cost reduction' they are just design flaws. You can sort most of them one way or another but it's a bit weird that they don't just work properly out of the box.

Anyway, I'll update fully once it's properly finished.

[Cuiken]

Just a few more wee updates on the build. My Bowhouse parts arrived along with an Artful Dodger skid plate. As mentioned, the Bowhouse kit was to improve the bump steer and comes with a pair of the bump stops to prevent over extension of the steering. The skid plate was because the truck runs a lot faster than probably intended and bottoms out on larger bumps. The stock skid was already looking pretty scarred after just a couple of test runs.



I considered trying to make these parts up myself from aluminium (as I did with the trailing arm mounts) but, ultimately, I decided to consider my own 'hourly rate' when figuring out whether self fabricating was going to be worthwhile. With cheap shipping from Amain, the Bowhouse kit was a definite no brainer and the Artful Dodger skid is stainless steel which I think will work much better than the aluminium sheet I have to hand.



So, here are a few pics of the finished chassis.




I cut out a piece of scale checker plate to make an insert for the front bumper. It hides the mess I made when drilling holes to mount the front spots. It's funny the stuff you get most satisfaction from 🙂



Bowhouse kit installed:



I added a brass tube with threaded rod to better brace the shock mounts. It's really stiffened up the chassis too:



I also used some short pieces of brass tube to extend the Vanquish bumper mounts. The tube I bought had an ID of 7.5mm and the bumper mounts fitted really nicely with just friction fit.



Viewed with the shell on, you can see the bumper now sits really neatly inside the shell:





Shot showing the installed skid and a clearer angle on the checker plate:



And, lastly a totally unnecessary shot of the rear diff cover after I painted it silver. Like I say, it's daft the stuff you take most satisfaction from but this looks awesome with the shell on.



No pics but I also shimmed the front and rear axles to reduce the usual Enduro axle slop and rebuilt the shocks(!?).

Which leads me to that last wee update. All four shocks leaked right out of the box. I was surprised as my other RTR Enduro never did this. Seems that some do and some don't. Either way, I filed a ticket with Element RC support on a Sunday night and had a full shock rebuild kit on Tuesday! You can't really fault the service.

Interesting feature of the rebuild kit is that it includes additional washers that are not included in the Trailrunner, Trailwalker or Sendero but which are included in the Gatekeeper. They fit after the two shock shaft silicon O-rings and add a bit more compression and support to the o-rings. Looks like they have been added to help prevent leaks:




So, only outstanding tasks are to shim the rear diff itself (to help with the higher power) and then add a few more decals.

Spring seems to be coming so I should be right on time.

[Cuiken]

And I think it's done. Decals applied (too much?) and shimmed the rear diff (just a 0.1mm shim behind the pinion). Pics below:












And one last shot showing the painted rear diff cover (which I'm still far too pleased with).




How does it drive?

Well, the weekend was pretty wet (and rather busy) so I was limited to back yard bashing. That said, I had a good blast with it ion the time I had available. Now, I'm bound to be a bit biased but I'd say it's a properly great RC truck. The handling is incredibly realistic, even better than my Kyosho Outlaw Rampage Pro and the top speed of ~13mph is spot on. The truck uses the entirety of its suspension travel over our very bumpy lawn and the IFS adds a degree of higher speed control that you don't get on a solid axle crawler. Sure, you can get it to tip over very easily but then so would a real truck if you turned the steering to full lock at full throttle. That's the charm. Damping with the stock oil is pretty much where you'd want it to be, just the right side of controlled (just).

All in, probably the most successful build I've done so far (given the original aim to build a realistic scale pre-runner). As far as I can tell there is no RTR or kit quite like this which also makes it a bit special. Given you can still get the base truck (trailrunner) at discounted prices right now, I'd definitely recommend building one up if you have the inclination.

P.S. I should acknowledge not all went well though. After 20 minutes of driving the threaded pin that holds the drive shaft onto the transmission output somehow came loose (I swear I threadlocked it). The construction of the Element drive shafts is such that the whole universal joint came apart and I lost some bits of it in the lawn. At £30 for replacement parts I have to say that stung a bit. I'll be gluing the pins in next time.

[durok]

I could definitely see this selling like the proverbial hotcakes as an RTR - it really came out wonderfully!

Element should take note!

Two thumbs WAY up...

[Cuiken]

Thanks!

Yeah, it's a really different type of truck and, honestly, the way it handles is incredible. Super realistic with just the right amount of torque twist etc to make it a challenge to drive. This realism of the chassis means you get proper 'on the edge' handling at scale(ish) speeds. Means it's a blast to drive even in small spaces. Testimony to the basic Enduro chassis I guess.

Not trying to big myself up here (the original idea was not mine) but I could definitely see it selling well.

Not sure what it is but the Enduro chassis just seems to behave a bit more realistically than the TRX one. Definitely my favourite platform for 'as is' crawling or modification.

[Mopar man]

Looks great nice work. I second a kit or rtr should be available.

[B-MOW71]

If I didn't know any better, I'd totally believe this is a newly released or soon to be released Element rig! ...Or maybe it is!!

Excellent work on making this just look cool and bada$$!

Originally Posted by Cuiken

Not sure what it is but the Enduro chassis just seems to behave a bit more realistically than the TRX one. Definitely my favourite platform for 'as is' crawling or modification.

I definitely agree! Driving my Element rigs is always a joy! Has been my favorite since their release.