SCX-6 Honcho Conversion

Honcho Conversion

scx6, axial honcho, bfg km3, rccrawler, rock crawling

Axial Honcho out on the rocks testing a set of the BFG KM3's from Axial.

Honcho Conversion

Not long after we acquired the SCX-6 Jeep Rubicon, Axial released the SCX-6 Honcho. This is basically the same trail truck / rock crawler but featuring a “Toyota” styled front cab, bumpers, roll cage, and Falken Wildpeak MT tires. Under the hood, it’s the identical setup as the Rubicon.

In the past, Axial had offered the Honcho on the 1/10 scale, built on the SCX-10II platform, but no longer in their current 1/10 scale lineup.

As an interesting side note, the original 1:1 Honcho was actually the Jeep J 10 “truck”, released in 1974. The Toyota variant appeared out on the trail years later, mostly comprised of home-fabricated setups.

Aside from the 1:1 world and custom RC versions of the original Honcho, for this discussion we will point towards the Axial SCX-10II Honcho as the start of the RC Honcho linage.

With the reemergence of the Honcho in a larger 1/6th scale, we briefly kicked around the idea of ordering the complete truck for the shop. At $1100, the Honcho is no small investment, so it seemed like a better financial move ( as if there are any “good” financial moves in the RC world ) to purchase the unique Honcho parts and convert our Jeep Rubicon into the Honcho.

Once Horizon Hobbies had the Honcho bits and pieces up for sale on their website, we fired off an order and awaited the UPS driver’s arrival.

1974 Jeep J 10 Honcho. The OG of Honcho lore and a fantastic machine. Photo Credit: jdittrich

This order was surprisingly expensive with the parts nearing $200 in total, but we had a hunch the smaller Honcho body would be more suited for crawling in tight terrain, and I’m a Toyota nerd at heart.

Less than a week later the shipment arrived, and with a little bit of paint experimentation ( eh, not our best work ) and some wrenching, and our new 1/6th scale Honcho was ready for the trail.

The new Honcho body is much better suited for tight, technical rock crawling.

Unlike the large, square Jeep Rubicon body, the smaller Honcho truck body and tucked bumpers greatly improved the approach angles, allowing us to work through tighter terrain without hanging up on the bumpers or body.

The sliders designed for the Honcho sit narrower than the Jeep’s, allowing the rear tires to climb onto rocks without catching on the sliders.

Due to the low stance of our suspension setting, there was some trimming required of the front bumper as well as a bit of trimming of the front fenders.

To save on some top-heavy weight, we omitted the spare tire and tire mount on the rear cage. While it looks nifty and scale, it does you no favors if crawling steep lines is on your agenda.

With the changes complete, we spent the next year and a half cruising the trails at Badrock Ridge, as well as some excursions to Calico Basin and Valley of Fire. During that time, the Honcho became one of the most favored crawlers in the fleet. I attribute this to the visceral realism it brings when crawling, delivering a real-world feel to its performance that 1/10 scale trucks just don’t seem to capture. With the Honcho, hours-long adventures have become commonplace when this truck is out on the trail.

We reviewed the Pro-Line Racing Hyrax tires with this setup, and you can read more about those tires and their performance on our Honcho under the Crawler Tire Reviews tab.

Note the quiet hum of the Spektrum inrunner motor.

Electronics

Much like the Vanquish models in our collection, the SCX-6 had relatively few upgrades from the factory. We had mostly removed parts to shave weight and reorient the bits and pieces for optimal rock crawling performance. Upgrading the servo is a must on this beast, so I’m not counting that as really an option.

One of the things which surprised us about the SCX-6 was the quality of the OEM electronics (not counting the servo). The massive 1200 kV brushless motor provided plenty of power, and its sensored aspect provided for a smooth crawl at low speeds.

If there was a down-side, it’s that the unit is quite bulky with the motor alone weighing 740 grams. On the up-side, it’s mounted forward and as low as possible, so it’s not a terrible setup, but it’s a substantial amount of sprung weight.

While pleased with the performance of the Honcho, we had slowly been replacing our 1/10 scale brushed crawling motors with outrunner motors. Outrunner brushless motors offer far more torque per gram than inrunner brushless and brushed motors. Much like inrunner brushless motors, outrunner brushless motors are virtually maintenance-free.

Inrunner motors: inside of motor rotates, outside remains in a fixed position.

Outrunner motors: inside of the motor remains in a fixed position, outside of the motor rotates.

Here is an excellent breakdown of the differences between inrunner and outrunner motors: Motor Details.

Inrunner motors have their place in crawling, but it’s hard to go back once you’ve spent any time crawling with an outrunner motor. Eventually you end up replacing many of your brushed or even sensored inrunner motors with outrunner motors.

This Holmes Hobbies small outrunner motor provides plenty of crawling power for our 2.2" Capra.

Since our SCX-6 Honcho is specifically focused on rock crawling, it’s a perfect candidate for an outrunner motor. A properly designed outrunner motor for the SCX-6 should have much more power per gram than the factory unit, but at a fraction of the weight.

Side by side, you can see just how much larger the Spektrum inrunner motor is when compared to the 3BRC outrunner motor.

Unfortunately, at the time there weren’t really any options on the market. We had seen a few people install massive Castle inrunner brushless systems in their SCX-6, but it appeared that bashing was more of their direction rather than crawling.

After some digging around, we came across 3 Brothers RC, and they offer two outrunner motors specific for the SCX-6.

SCX6 Blackjacket 1280kv 14-pole sensored outrunner. ( 335 grams )

SCX6 Blackjacket 860kv 14-pole sensored outrunner. ( 430 grams )

The 1280kV is rated up to 6s and the 860kV is rated up to 8s. Both should work well for any stock SCX-6 platform, and unlike most outrunner motors, these two units are sensored.

The 1280kV Blackjacket motor is similar in kV to the OEM Axial 1200kV Spektrum brushless unit, and on 4s power, both motors will develop a similar RPM. That said, the 1280 Blackjacket is 335 grams compared to the 740 grams of the Spektrum motor, and most assuredly offers far more torque and drag brake simply by design. Again, reference the Holmes Hobbies videos for this, especially this one: Holmes Hobbies Video

So if nothing else, the 1280 kV Blackjacket motor is both lighter and delivers more torque than the Spektrum unit, and for our goal of improving crawling performance, that’s doubly awesome. Now what about that 860 kV unit?

The Blackjacket 860 kV will also run smoothly on 4s, but it will be slow. On 8s, guessing from a distance and based on our experience with outrunner motors at a fraction of the size, it most likely will have enough power to grenade the SCX-6 transmission and twist driveshafts like pretzels. But if you pair the 860kV motor with a 6s battery, you land in the "Goldilocks" zone with roughly 19000 RPM ( no load ), which depending on the source, falls just at the bottom of the optimal range of 20,000 to 40,000 RPM for outrunner motors. It's still plenty powerful enough to wreck your transmission and axles, so it's wise to adjust the slipper clutch accordingly. Also worth noting, the Spektrum 1200 kV generates 17280 RPM on 4s.

Our Honcho is all about rock crawling, and with our single-speed transmission, the 860 kV Blackjacket was the right choice. Since our game is all about going slow, this motor will have plenty of room to spin up if needed, but happily chug along at a creeping pace. This setup should run smooth, cool, and provide a massive amount of torque and drag brake. The 6s power will also run more efficiently than the 4s power, and we could probably get away with using lightweight 6s drone lipo packs.

Sorting out the electron flow through the system was a new Castle RC Mamba Monster X. 3BRC has an excellent video as to how to properly set up this ESC for their motor, and I suggest you follow it. It’s just a few specific selections on the Castle software, and you’re up and running.

As for the connectors, while I know this will give fits to the gang over at Castle RC, we soldered XT-60 connectors to the ESC. Since we are using drone batteries for crawling and they all come in XT-60 connectors, swapping the ESC connectors to XT-60 was a much simpler option.

Castle RC is well known for their quality, and a few bugs aside with the first-gen Copperhead 10 ESC’s, we haven’t had much to complain about with their products. Even so, one thing to be aware of is the large size of the Mamba Monster X ESC.

It’s nearly three times the weight of the Spektrum ESC, so we ended up adding some weight back into the Honcho setup with this Castle ESC.

Castle RC Mamba Monster X; overkill in many ways, but fully capable of handling the 6s power.

The result of weight change with motor, wiring, and ESC:

Axial / Spektrum combo: 870 grams
3 BRC / Mamba Monster X combo: 611 grams

With a net weight loss of 259 grams, or little more than half pound, we saved a bit of weight with the electronics swap, but it’s saved it on the sprung side of the equation, so it’s an overall benefit, be it a small one.

We ended up adding 6mm spacer blocks under the servo mounting tabs to clear the servo horn over the drag link.

Servo Mount

Knowing that the 6s battery and voltage limiter will need a bit more space upfront, I opted to move the servo to a bumper mount, and Treal RC offers a bumper mount which will work with the larger 1/5 servo we’d been running.

The first challenge was to sort mounting height in that the servo link would contact the drag link when the suspension compressed, so to avoid this we had to raise the servo on blocks high enough to clear a full suspension compression.

During this process, we made note that while this servo fits in the vertical position under the body, designing a lay-down mount was on the radar for a later date. For the time being, we will stay with the vertical mount in that it will get us on the trail quickly.

Once the servo height was established and the horn would clear the drag link, we measured for a new servo link length which would give us adequate steering range.

Not surprisingly, we needed a new servo link in that there isn’t one currently made for bumper-mounted servos for the SCX-6.

One thing to note is that the SCX-6 doesn’t have a great range of steering, so the vertical mount is fine in that it doesn’t hinder the total range of steering. The knuckles could use a redesign for additional steering.

After some testing, we found that a 100mm length, 6mm thread turnbuckle or all-thread was the correct setup, and you can find these on McMaster Carr for relatively cheap.

New 100mm servo link as well as new panhard link.

Supporting steering, we switched out to the Vitavon panhard mount because it comes with beefy aluminum link ends which are much more robust than the plastic Axial units. Our NSDRC servo puts out enough force that if you get the tires jammed up and try to turn, the servo will snap the factory plastic panhard link ends. We've done this a few times, and carrying back the SCX-6 to the truck is not much fun.

As mentioned earlier, the plan was to run the SCX-6 on 6s, we needed to step down the voltage to the NSDRC servo. While the 2500 unit is immensely powerful, it is only rated to 4s, so NSDRC sells a few different voltage limiters to protect the somewhat spendy servo.

In order to properly fit the battery and electronics between the two shock mounts, we removed the Axial pieces, including the lower brace and installed an aftermarket aluminum ESC tray.

These are on Ebay for about $30, and all you need are the two cross members; throw away the rest.

The aluminum cross members are rigid and machined to work with the OEM screw positioning. It’s cheaper to buy these than to make them. From there, a few basic spacers and two pieces of thin acrylic sheeting with carbon fiber stickers, and you have two flat plates for mounting. One tray is for the voltage limiter and the other for the battery. A bit of Velcro and a few zip ties, and the Honcho is ready to go.

Surprisingly, we saved a bit of weight with this change as well. The OEM electronics tray and Powerhobby 1/5th scale servo mount were relatively heavy when compared to the light-weight aluminum parts we used for the battery tray.

Motor Mount

This one surprised us, well not the OEM unit from Axial, but the aftermarket unit developed by Vitavon Racing and subsequently copied by a few other companies.

With the 3 BRC outrunner motor, we wanted to install an upgraded motor mount with the ability to finely tune gear mesh over a range of pinion gears. The Vitavon unit consists of a machined aluminum motor mount with aluminum sliding motor plate.

Commonly found on RC racing buggies, this setup allows for precise positioning across a wide range of pinion gears. Knowing that our base RPM was going to be a bit faster than the OEM brushless motor, figured there would be some experimentation to find the right pinion gear for our crawling needs.

From the description, the $120 Vitavon unit seemed ideal, but once we had the unit in hand, design problems became apparent.

Vitavon motor mount in the background.

The first oddity with the unit is that you must install the motor onto the motor plate, then attach the pinion, sandwiching the motor plate between the motor and pinion. The motor shaft hole is too small to pass the pinion gear, and it's not slotted on the side. Once the pinion gear is mounted, you must then slide the motor plate into the housing, before you can mount the outside half of the housing onto the other half which is bolted to the transmission.

Why you may ask? Well, there is no window or opening to clear the pinion gear on the aluminum housing. The pinion gear makes contact with the side of the housing, so you cannot insert the motor plate once the housing is attached to the transmission case.

The sliding motor plate cannot be removed without taking the front of the housing off.

Confused, we flipped the mount around just to be sure, and indeed there is only one way to mount the motor plate. This makes no sense.

Next issue to mention is that the Vitavon housing completely covers both the spur and pinion gears; it’s a sealed unit. While this may seem ideal to keep dirt and debris out, you can’t see the pinion gear to adjust the right positioning in terms of depth of the pinion on the motor shaft nor engagement to the spur gear. Simply put, you can’t see the spur gear in relation to the pinion gear.

Debris covers have been figured out by Element, Vanquish, and Traxxas for their crawlers and trail trucks, all without running into this problem.

This is a considerable oversight in the design, but it’s not the first time we’ve encountered a Vitavon part in our shop which seemed to be insufficiently tested.

We ended up using transfer blue on the spur gear to ensure we had the correct pinion gear depth. This was done by sliding the motor as far to the left as possible, jamming it into the spur gear for a moment and then sliding it away. We then pulled the front half of the housing back off and made the depth adjustment needed for proper alignment.

The final step was to reinstall the entire unit, jam the motor as far into the spur gear as possible, then slightly move the motor mounting plate to the right while we rotated the outrunner by hand, going by feel to set up the right gear mesh. I'm not sure how you would do this if you're using an inrunner motor. Ugh, what a terrible design!

So, for $120, you get an adjustable motor mount where you can neither see nor feel the pinion gear to spur gear engagement.

As a parting kick to this horse carcass, the aluminum housing is heavy. While we saved some weight on the motor swap, we tacked a decent amount back on with this motor mount, so until there is a better mount ( or we stick it in the milling machine to modify ), it’s what we have to work with.

Final Prep

With the wrenching and soldering complete, it was time to plug in a battery and make the final servo adjustments, calibrate the transmitter to ESC, and then check the initial throttle inputs.

Setting the trim and travel of the steering is quick work on the transmitter, but an important task when considering the power of the servo. ESC calibration to the transmitter is also straight forward.

As for the application of throttle for the first time, well, there’s something for us to discuss. Unique to outrunners, most ESC’s programming creates a frequency which is transferred to the motor, resulting in an audible “whine” on outrunner motors.

Think of the motor housing as the speaker, and the ESC as the radio. Interestingly, this does not occur with standard inrunner or brushed motors.

Current weight distribution of the Honcho as of 10/2/2024.

Some ESC / motor combinations are louder than others, and the 860 Blackjacket is loud to our ears. Companies such as Holmes Hobbies have solved this issue with their Crawlmaster V3 ESC, but at the time of this writing, Castle RC has not addressed this issue with their ESC software. It's hard to guess as to if this is even on their radar and unfortunately the Holmes Hobbies Crawlmaster V3 is not rated for 6s, nor is it sensored, thus not compatible with the 3BRC motor.

Continuing with the initial testing, the motor startup was exceptionally smooth and slow, noticeably more controllable on the bottom end than OEM Spektrum motor. Inside the shop, the large plastic Honcho body resonated loudly from the motor, and the shop dogs weren’t having any of it, trotting off to the backyard.

The new Honcho electronic upgrades happen to coincide with the start of a new tire review for the Axial BFG KM3’s tires. These tires are the OEM set from the SCX-6 Jeep Rubicon, so the timing was perfect for a bit of dual-purpose testing. Not only would we see if the electronics upgrade was worth the investment, but also to see what the KM3’s could do.

With more than enough power at our disposal, we could slow-creep these BFG KM'3 up the trail at a snail's pace.

Out on the Trail

Crunching along the trail as we headed into the upper section of Badrock Ridge, the powerful Blackjacket motor moved the Honcho along with surprising ease.

There was virtually no startup hesitation from the motor, and no bogging down as the Honcho rolled over the larger sandstone pieces.

Outside, the ESC whine wasn’t terrible, but it would take some getting used to in our quiet desert environment. The OEM electronic setup is much quieter, leaving the soft hum of the gears chugging along.

Now there is the ever-present outrunner whine that changes in pitch as the motor slows down or speeds up. It’s at the loudest level when starting from a dead stop, then softens somewhat as you get moving along.

Swinging around a tight corner, we headed up a steep and slick sandstone slab.

I was curious as to if the KM3’s would be able to stick to this difficult surface, but to my surprise, they hooked up rather well.

Because it’s a short section of the trail, we made a loop and ran this slab a few times, pausing to do a bit of filming.

In this take, we run up the slab about halfway and then stop. We do this to show a few things.

For this video, we muted the volume so there is no whine of the outrunner motor.

First, you will get a feel for how steep and slick the sandstone slab is by noticing the Honcho ever so slightly begin to slide down the slab with the tires fully locked in position by the drag brake.

Second is how strong the drag brake is on the Blackjacket motor; the wheels don’t move one bit. The Honcho tips the scales north of 11,000 grams, yet the Blackjacket had no trouble locking the wheels in place. Of course the transmission plays a role in this aspect, but the fact that a motor both smaller and lighter than the OEM unit, yet delivering a brag brake capable of handing the Honcho's considerable weight was impressive.

Third is the surprisingly good traction of the KM3’s. They are a tough, do-everything in the desert rubber compound, yet they can hold their own on slick, steep rock.

After a few moments, we gently ramp up the throttle, showing the smooth and controlled startup of the new electronics. This sensored outrunner motor perfectly suited for this kind of crawling.

Note the pitch of the motor whine changes with RPM.

We spent a few more hours on the trail that day, and then I followed that up with a few more months of testing the KM3’s, all while learning to accept the Blackjacket’s background noise.

On some of the videos reviewing the KM3’s, we opted to edit out the motor noise; it was just too distracting in the video.

What we did come to love was the improved performance of the Honcho, and the Blackjacket 860 kV was shown to be a perfect match for our slow, technical style of crawling.

I was also surprised at our run times with the small 6s lipo batteries. For a 1300 mAh 6s lipo battery, I was seeing a little over an hour of continuous crawling.

Periodically I would check the temperature of the motor and ESC, and not once did it feel past anything I consider to be warm. The ESC fan had yet to fire up at any point during the testing. This is a cool-running, powerful, and highly efficient setup.

Colorado

Taking a break from the desert sandstone, I headed out to Colorado to meet up with the other half of the MVRCA operation, going toe to toe with Kyle’s new RC Speedy SCX-6 moon buggy.

I was feeling pretty confident in the Honcho’s performance with this new setup, so I figured I’d bring my A-game and see what this RC Speedy SCX-6 moon buggy was all about.

Typically, once you change the chassis and body of a crawler, it’s pretty much a different platform, but since he was rolling with the stock Spektrum electronics and I had the new Blackjacket and Castle combo, I felt we would be close.

To help keep some things even, we ran the identical foam and tire setups on the two SCX-6 units, going with the JConcepts Landmines with Crawler Innovations two-stage foams and sidewall inserts.

scx6, axial honcho, jconcepts, rccrawler, rock crawling

The Honcho out on the rocks in Fruita, Colorado.

rc crawler, rc speedy, scx6, jconcepts, rock crawler, rc crawler, moon buggy

RC Speedy XXL stainless steel moon buggy chassis for the SCX-6.

Out on the lichen covered rocks, the low CG and lighter weight ( by over 1,000 grams ) of the RC Speedy moon buggy was noticeable, but not quite the advantage as one would think.

There was plenty of trash talk as Kyle favored tight spots and sharp transitions to take advantage of the narrow cage and no front bumper, but after two days of crawling, there was only a single spot on the trail where the moon buggy handled a tricky off-camber set of steps that the Honcho could not sort out.

In all other cases, the Honcho stayed right with the RC Speedy setup, although the moon buggy did make some things look pretty easy. I fully attribute that to the design of the buggy and not Kyle's crawling skills.

On the steep rock sections, the Honcho gave up nothing to the moon buggy, and the absolute monster control of the drag-brake made steep descents no problem.

Adding to the trash talk, Kyle would shout at me as if it were hard to be heard over the ESC whine, but I have a hunch he’ll be ordering this motor and ESC combo in the near future. Make this a quiet ESC, and this is a 10/10 setup.

The two days of crawling were good fun, and the large 1/6th scale platforms bring a unique feel and experience.

If asked, Kyle would probably say the RC Speedy had a greater edge in performance, but since he’s too busy engineering widgets and I’m the one doing the writing, the story goes that they were closer in performance than one would think.

I will also say I’m a big fan of the RC Speedy moon buggy chassis; it’s attractive, well made, and impressive out on the trail.

This was a tricky line.

rc crawler, rock crawling, jconcepts, scx6

JConcepts 2.9" Landmines are perfect on this rock surface.

Final Thoughts

At this point, I think it’s time to put the pencil down for this round of upgrades and call the Honcho complete, at least for the time being. Noise from the outrunner aside, we couldn’t be happier with the trail performance of the truck.

The Blackjacket outrunner motor delivers a substantial improvement in terms of torque, control, and drag-brake, but the upgrade wasn’t inexpensive.

For the cost of the ESC, it annoys me that this outrunner whine has not been addressed. I understand the Mamba is not a crawling ESC, so I pull punches here at some level, but Castle has some sharp engineers and I bet they could sort this out if so inclined to do so.

Looking at the numbers invested for the 3BRC motor, ESC, and voltage limiter, we were into the new electronics for around $400.00. That’s not including $120.00 we spent on a terrible Vitavon motor mount, nor the little bits and pieces we used to relocate the servo.

It’s easy to turn the SCX-6 into a money pit, and I’ve seen quite a few with far more dollars sunk into their builds than we have in this Honcho.

Thus, for dollar to dollar, I’m OK with what we’ve spent versus what we’ve gained in performance out on the trail, but the outrunner whine remains a bothersome detail.

In this video you can hear the outrunner's whine magnified by the rock walls on this trail. We do hope Castle RC sorts this issue out sooner than later.

This leaves the door open for more changes to the Honcho. The moment an ESC is released which will handle the 3BRC motor and solve the associated whine, the Mamba is getting replaced. If Castle gets to working on this issue, I'm more than happy to try out an updated ESC. As of the time of this writing, none of the Castle ESC's run silent with outrunner motors.

With the modifications complete, the total running weight of the SCX-6 dropped from 11748 grams to 11121 grams, saving us a total of 627 grams. We could probably shave a bit more weight from the Honcho, but I’m not sure it would result in any noticeable improvement out on the trail.

I feel that the only question remaining is do we start another SCX-6 moon buggy with portals and try out the 1280 kV Blackjacket? Portals and a Ti cage from RC Speedy? I’m not sure I can stomach the massive price tag, but it would be slick.

Lay-Down Servo Mount

While the Honcho is pretty much complete at this time, we wanted to refine the steering servo positioning with a properly designed servo mount. I've never been completely satisfied with the various mounting options in that the limited some of the steering travel or forced you to use an extra long servo arm which seems to interfere when the suspension is under full compressions.

This new servo mount ( light grey ) accomplishes a few things; moves the weight of the servo forward and lowers the weight by laying the servo down rather than having it standing up. The positioning of the servo provides the maximum range of travel of the steering linkage without binding on the drag link or axle housing.

The 3D printed mount utilizes 4mm hardware to secure the servo to the mount, and 3mm hardware to secure the mount to the Treal aluminum front bumper housing.

Parts Needed

Treal RC Bumper Mount: AXI251008
NSDRC RS-2500 Servo
NSDRC 1/5th Monster Servo Horn ( Short )
McMaster-Carr: Carbon Steel Turnbuckle-Style Connecting Rod, M6 x 1.00 mm Thread, 100 mm Overall Length
4mm hardware

We've been testing this out on the trail and the performance as been excellent.

With weeks of testing out on the trail, we have not encountered any issues or failures of the design.

The only modification of the truck needed was a small notch in the front bumper to clear the servo housing. This notch is hidden when you have the body closed.

The Honcho body has plenty of space under the hood to clear the servo and mount, and the front body mounting posts align properly with the lower mounting holes. We did not need to trim any of the Honcho's body.

Current Configuration

Motor: 3 Brothers RC Blackjacket 860kv 14-pole sensored outrunner, 15 tooth pinion.
ESC: Castle RC Mamba Monster X
Servo: NSDRC 2500
NSDRC: Voltage Limiter 5 amp - 54mm x 24mm
Battery: Ovonic 6s 1300 mAh ( 202 grams )

Additional Upgrades

Treal front shock towers
Power Hobby brass knuckles and C-hubs
Samix brass hubs ( +7 mm )
Soft shock springs

Links
https://www.3brothersrc.com/
https://rcspeedyfab.com/
https://jconcepts.net/large-scale.html
https://www.trealhobby.com/collections/scx6