Build Complete: Axial Wraith

[fyrstormer]

I finished my Wraith build. I did a whole bunch of stuff to this vehicle in a short amount of time:

- Replaced the motor
- Rebuilt the transmission with hardened-steel gears
- Replaced the 48-pitch pinion and spur gears with 32-pitch gears
- Replaced the stock driveshafts with MIP hardened-steel driveshafts
- Replaced the diff gears with Hot Racing hardened-steel gears (including an overdrive gear for the front axle, to improve "grab" when climbing and reduce "push" in corners)
- Replaced the front dogbones with RC4WD CVDs
- Replaced the stock plastic hubs with TopCAD aluminum hubs
- Replaced the stock plastic front bumper supports with RC4WD aluminum supports
- Replaced the stock wheels and tires with R35 Ripsaws mounted on Axial Walker Evans beadlocks (including Vanquish aluminum SLW spacers)
- Added 2oz. Axial clamp-on weights in the front wheels, to lower the center of gravity a bit
- Rebuilt the shocks with aluminum bodies, mounts, and spring collars
- Replaced the stock plastic suspension and steering linkages with titanium linkages from Blue Monkey RC
- Added bash guards from Blue Monkey RC
- Replaced the stock servo with a Hitec HS-7955TG titanium-gear servo (including an Axial clamping 24-spline servo horn)

This is a high-torque vehicle and I don't like breaking parts, so from the motor spindle to the wheel hubs, the only parts of the drivetrain that *aren't* made of hardened steel are the spur gear and the diff bodies -- everything else is rock-solid.

The suspension and steering linkages are titanium, because I know perfectly well they're going to get bashed into stuff and dragged over rocks, and neither plastic nor aluminum will hold up as well as I want. The lower suspension links are a high-clearance design, which helps a bit, but there are obvious scrape-marks on them already, so I'm confident I made the right choice in getting the more expensive titanium links.

Various people told me I didn't need bash guards for the diffs, but after seeing how quickly the diff covers were getting chewed up, I decided to get bash guards anyway. Blue Monkey RC makes a nice set that have a low profile and are made of steel instead of aluminum, so they can actually do the job that bash guards are supposed to do.

This is what they looked like new:

...and this is what they look like after a week of unapologetic bashing:

The rear bash guard doesn't look as bad, but it's got its fair share of scrapes on the underside. The important thing is, the replacement diff covers I got still look pristine, instead of having the fins bent and broken off, like the original pair had.

I don't like plastic shocks, but I didn't like the look of the Axial aluminum shocks, so I bought green and black aluminum parts from STRC, and rebuilt the stock shocks. They work a little smoother, just like metal shocks always do.

I opted to keep the speed of the stock motor, but I wanted more durability, and I didn't want to drop a bunch of money on a sensored brushless system, so I opted to install a name-brand rebuildable brushed motor. While it was originally intended for something more like a touring car or a go-fast monster truck, this Team Orion 20-turn motor is holding up great in my Wraith. It doesn't get too hot, the battery lasts forever, and it produces noticeably more torque than the original throwaway motor did. I added silver brushes to improve conductivity, and the next thing I noticed was I had to tighten the slipper clutch to keep the motor from spinning freely when I pegged the throttle, so that improved torque output as well.

In the three weeks I've had it, this vehicle has completely supplanted my go-fast vehicles as the vehicle I'm most likely to play with on any given day. It comes with lights, so I can run it in the dark after I get home from work, and the fact that it climbs over stuff instead of going fast means that I can actually have fun with it in the dark without worrying about destroying it against the side of a curb. This vehicle is one of my best RC purchases to-date.

 

[Ecranu]

Very nice! Did you also go with a steel spur gear?

 

[Duuuuuuuude]

I finished my Wraith build.

:ror:

No one is ever "finished" building.

Solid rig though. Nice work.

 

[fyrstormer]

Very nice! Did you also go with a steel spur gear?

No, I went with a Kimbrough nylon 32-pitch spur gear. It will prolong the life of the pinion, and there are enough reduction-gears between the spur and the wheels that the spur shouldn't be shocked too much when the wheels slam into something and stop rotating.

I did have one gear fail on me, though. The gear that failed was the idler gear in the transmission. The transmission was rebuilt with hardened-steel gears all around to keep that from happening again.

 

[fyrstormer]

:ror:

No one is ever "finished" building.

Solid rig though. Nice work.

True, but anything I do to the rig from now on will be the result of using it for months and either breaking stuff or realizing it has hidden deficiencies I didn't notice before. The initial build, i.e. working out all the bugs from the factory and customizing it to my personal driving style, is done at this point.

I will admit I'm already fighting the urge to build another vehicle, but I need to move in a month, so hopefully that will keep me distracted for the time-being.

 

[fyrstormer]

Wow, I totally forgot to update this thread.

- - -

I've made a few changes to this vehicle since I "finished" building it. I removed wheel-weights from the front wheels and replaced them with a big block of lead stuck on top of the servo. I also replaced the TopCAD aluminum steering knuckles with STRC steering knuckles, because the TopCAD knuckles weren't strong enough.

This is what a quarter pound of lead ballast looks like:

And here are the new steering knuckles:

I also installed the Dig kit for the gearbox; it's interesting, but I'm still deciding whether I want to keep it long-term. It's not doing any harm being installed though, so for the time being I'll leave it in there.

 

[fyrstormer]

More changes. I burned-out a second Team Orion 2x20T motor, so I switched to a Tekin 35T motor with much higher gearing, so I could get comparable top-speed while still limiting the maximum current that could flow through the motor when it stalls. I was unimpressed with the performance, so I replaced the motor again, this time with a Tekin 30T Pro Hand-Wound motor, and I found some old Trinity silver laydown brushes on eBay to use with the motor. I was pleased to see the Tekin Pro Hand-Wound motors also have lathed commutators; that made break-in a hell of a lot easier.

At the same time, I also concluded that I simply had no use for the Dig function that I'd added to the stock gearbox, and I really wanted to avoid burning out yet another motor, so I also replaced the stock gearbox with the RC4WD AX2 gearbox. Once I settled on suitable gearing (17/54), I was able to get the same as the original top-speed in high gear (about 12mph) while getting a decent 4mph in low gear -- as well as 3x more torque in low gear, which means now when grass and small vines get wrapped around the axles, the truck just tears them out by the roots instead of getting stuck.

I had to cut away some of the plastic on the top side of the center skidplate so the AX2 transmission could fit with the optional gear cover installed, but it was worth it. This transmission is rock-solid, and it gives me the flexibility I've been looking for without having to wedge a sensored-brushless ESC into the chassis. (there's not a lot of room in there, I'm sure you've noticed, and I hate sticking electronics inside the "passenger compartment" where they would be visible.)

Here, have a running video:

https://www.youtube.com/watch?v=9Mx2jeZA6gQ

 

[fyrstormer]

The Tekin 30T Pro Hand-Wound motor I'm now using works great, but I still saw operating temperatures higher than I'm comfortable with, so I added an endbell fan to the Tekin motor, using MuchMore Racing endbell fan screws that are nearly impossible to find anymore. The fan is a Sunon chipset fan with dual ball-bearings, and the deeper profile (15mm instead of 10mm) means the fan blades can be a little more efficient than they would be if they had to be shorter.

This involved adding a power tap to the ESC, because I wanted to run the fan on full battery voltage, instead of the weak 5V coming out of the BEC.

I tested various spots on the circuit board until I found one that provided full battery voltage, but was still switched by the main power switch, so the fan shuts off when the ESC shuts off.

The cutout that I made in the center skidplate a few weeks ago, to accommodate the fan, was almost perfect; it just required about 1mm of trimming to make sure the fan didn't actually touch the skidplate.

The cutout that I made to accommodate the AX2 transmission's spur gear cover is also nearly perfect, which I never noticed before. It's especially impressive because I totally just eyeballed it, I didn't measure anything.

There is officially no room left in the transmission tunnel on my Wraith. It's a wonder I can even manage to run wires through it anymore.

I ran it last night and never saw a temperature higher than 90F, which is about 75F lower than I'd seen before with this motor. (admittedly it was 32F last night, so the motor will get a bit warmer in the summer.) Hopefully I'll never burn out another motor in this truck.

 

[fyrstormer]

Thanks. The motor really needed some extra cooling; it's stuck in the transmission tunnel with basically no airflow at all, which might not be a problem for the stock motor which has a built-in fan, or for a brushless system which wouldn't run as hot in the first place, but for a mod brushed motor it's just stifling in there. The endbell fan helps a lot.

Maybe someday I'll build a vehicle with a sensored brushless system installed, and I can marvel at how glorious it is, but for now, this old-school setup is still fun.

 

[fyrstormer]

Tiny update: Ever since I installed the titanium steering links, I've been using a Jagwire bicycle brake cable holder to keep the main link and the drag link close together, so the drag link wouldn't flop around. (the brake cable holder snaps onto the two links and pivots in the middle.) It works great, except that it's slightly loose, and it slides back and forth on the links over the course of a run. If it slides too close to the point where the main link connects to the servo horn, it can pull the drag link upwards far enough that the drag link gets stuck behind the servo horn.

Well, today I finally realized I could keep this from happening by sliding tight-fitting O-rings onto the steering links, trapping the brake cable holder in a single position. Problem solved; the steering links don't flop around, and the coupler stays-put.

Also, here's a gratuitous flex shot from a recent run:

 

[fyrstormer]

A few more mods I just finished up:

Front fenders, to keep debris out of the "passenger compartment". I might install rear fenders too, eventually, but the fronts were such a pain to trim, test-fit, re-trim, repeat, that I won't be doing the rears any time soon.

I added extra screws to keep the fenders secure; 2 along the side and one at the top, on the underside of the spot where the front hood screw goes in. I had to shorten the screws sharing that screw-hole by about 1mm to make sure they wouldn't collide with each other. The rest of the screws I just drilled into convenient bits of rollcage where I knew other screws weren't passing through.

I also added extra screws to the roof, to keep the corners in-place. I put one at the front corner, and two at the rear corners. Now they won't get lifted-up and get debris jammed under them.

Due to recent changes in the suspension (lengthening the lower suspension links to tilt the axles to a more horizontal position), I realized I could now add more ballast to the front axle without having clearance problems. So I added another layer to the big lead block I had previously stuck on top of the servo, to bring it up to a total of 6 ounces (or 132 grams, if you prefer).

I thought I would be done with this build a long time ago, but the strange thing is, the Wraith keeps benefiting from incremental improvements almost endlessly, whereas my other vehicles hit a pretty clear point of diminishing returns where spending more time and money didn't accomplish much. It's an odd vehicle in that regard.

 

[Sevastra]

I thought I would be done with this build a long time ago, but the strange thing is, the Wraith keeps benefiting from incremental improvements almost endlessly, whereas my other vehicles hit a pretty clear point of diminishing returns where spending more time and money didn't accomplish much. It's an odd vehicle in that regard.

Never really thought about it like that, but you're absolutely right. It is.

One thing I'll suggest as your next mod is to pick up some metal bearing caps for your differentials and a pair of thrust bearings for your pinions. It's more of a preventive measure than anything else. The stock plastic caps will allow for a small measure of flex, and the thrust washers on the pinions will help prevent ring and pinion wear / improper mesh & binding.

Note: This really isn't too big of an issue until you start running high power setups. But even on a stock rig it'll help prolong component life.

 

[fyrstormer]

Ahh, so THAT'S why people buy those metal diff bearing caps.

I'm not sure what you're talking about with the thrust bearings for the pinions. Can you link to a product or a thread describing their use?

 

[Sevastra]

AR60 THRUST WASHER MOD - Super Shafty

You'd use these to keep the pinion from being jammed into the ring gear on the differentials. Hopefully the picture explains better than I did.

 

[fyrstormer]

I see. Under what conditions would the pinion gear be jammed into the ring gear?

 

[fyrstormer]

So, I bought a CellBlock from Crawler Innovations, for my Wraith to sit on to keep the tires off the ground. Basically it's a big cube of closed-cell foam that conforms to the underside of the vehicle sitting on it. It works nicely.

However, after leaving my Wraith sitting on it for a few days, I noticed it left imprints of the transmission-mount screws in addition to other features of the center skidplate. This gave me an idea: Attach magnets to the CellBlock so it will snap into the correct position and stay there, when I put my Wraith away.

Now it works even better.

 

[fyrstormer]

Well, after two months of not using this truck very much because of my failed attempts to sort-out the diff pinion bearing problem, I finally spent [redacted] dollars on Dlux Fab modified AR60 axles with 5x13 inner pinion bearings *and* a complete set of Boca ceramic bearings for the entire truck. That's 26 bearings, 10 of which were buried inside the RC4WD AX2 transmission, which I also disassembled, washed, and re-greased. That job took all evening and all night to finish. Oof.

Man, it sure rolls smoother now. I hadn't changed the bearings since I bought the truck, and some of them were definitely not happy about having been run through the local creek a bunch of times. (needless to say, the stock bearings are *not* stainless, unlike the ceramic bearings I just installed.)

My Wraith retains the title of "Truck That Can Survive The Most Savage Of Beatings" among all of my collection. My Summit probably wins overall though, because it comes close to the same durability but I didn't have to spend hundreds upon hundreds of dollars to upgrade it.

 

[lostonthetrails]

So, I bought a CellBlock from Crawler Innovations, for my Wraith to sit on to keep the tires off the ground. Basically it's a big cube of closed-cell foam that conforms to the underside of the vehicle sitting on it. It works nicely.

However, after leaving my Wraith sitting on it for a few days, I noticed it left imprints of the transmission-mount screws in addition to other features of the center skidplate. This gave me an idea: Attach magnets to the CellBlock so it will snap into the correct position and stay there, when I put my Wraith away.

Now it works even better.

 

[fyrstormer]

Heh, thanks.

 

[SCREAMER]

I had to cut away some of the plastic on the top side of the center skidplate so the AX2 transmission could fit with the optional gear cover installed, but it was worth it. This transmission is rock-solid, and it gives me the flexibility I've been looking for without having to wedge a sensored-brushless ESC into the chassis. (there's not a lot of room in there, I'm sure you've noticed, and I hate sticking electronics inside the "passenger compartment" where they would be visible.)

I run a Castle MMP in mine. It's sensored-brushless, has a built in fan (barely ever comes on even in 100* ambient temps), and fits between the front shock towers with room to spare. I'm running the battery and bec in front too. With as much money and time as you've spent on brushed motors, you shouldn't eliminate brushless as a possibility. This was by far the best thing I did to my wraith. I have butter smooth startup and torque and she still runs 17-18mph if I punch it, and gets there quick! It's such a good setup I'm switching my SCX10 over to brushless as soon as it's motor dies which I know will be soon in this heat.