Bandito: 8x8 SCX24

I've had a variety of RC cars since I was about 14 years old, which lately includes mostly rock crawlers. Playing Snowrunner has made me want to build a big fancy 10x10 1:10 RC with three steer axles and a two-speed gearbox. But my wallet said no and I am just me and not sponsored, so instead I'm building a less big and less fancy 8x8 1:24 with two steer axles and a bottom-dollar brushless motor.

When I was working a prior job where a coworker was also into RC, I got an Associated Element 24 1:24 crawler/trail truck, which turned out to not be a great crawler. The axles are really flimsy, and the driveshaft clearance is poor. I got it because it has front and rear 4-link and servo on frame, but it turned out to be irritatingly prone to high centering compared to the class-leading Axial SCX24 Deadbolt, and also to have poor support both from AE and third parties. I also wanted a more "scale" driving experience than the worm gear axles on the SCX24 provide, but there's enough slop in the drivetrain that I needn't have worried given that none of these small trucks have differentials and they're all therefore pretty similar to operate. Some of the more expensive examples among the larger trucks have locking open diffs.

The SCX24 is now an entire class in itself, with direct design copies coming from everything between major manufacturers like Injora and hobbyists with 3d printers or laser cutters, or just ordering parts online. These copies have the exact same dimensions, screw holes in the same locations, transmissions so identical they are interchangeable and so on. The copies are the same thing for all reasonable intents and purposes, with full parts interchangeability down to axle shafts and gear sets. Some are simple direct knockoffs sold to cannibalize sales, but they are also made with almost every conceivable customization; Copies are offered in alternate materials like aluminum or carbon fiber, with frames designed to lower the center of gravity or increase ground clearance, or even to add additional axles.

As mentioned I've been playing Snowrunner lately, and all of the best trucks in that game have at least three driven axles. One of my favorites despite some deficiencies is the Bandit, an 8x8 truck with two front steer axles, and a cab made from a shortened bus body. Making a "middle" or tandem drive axle to which you can connect another driveshaft to power another axle is pretty easy for the SCX24 as it only really involves drilling a hole in a "differential" cover and swapping the worm gear, though you don't have to actually do this yourself as you can just buy the parts.

Long story shorter, Aliexpress currently is selling an 8x8 SCX24 kit for around $150 shipped with typical discounts. It has a carbon fiber frame and Aluminum almost everything else. The center part of the truck between the middle axles is basically a "standard" super lightweight carbon fiber SCX24 knockoff, but then it keeps going in both directions with additional axles, and the middle axles have outputs which go on to run those axles. I'm not sure yet whether the shocks are supposed to be filled with oil or grease, but they are possibly functional if oversprung. The wheels are aluminum, beadlock and five-spoke, and some with some kind of decent tires. Unfortunately these are a little too big and get excessively close to one another in front, so they may have to go. The transmission has an aluminum case, but plastic gears. The driveshafts, which are all different lengths, are steel. The second and third axle covers and the 7mm wheel hexes are brass. It comes with a press-on pinion gear for a typical 1:24 scale motor, and a spare pair of frame rails. The axles are aluminum, but sadly the cheapest things possible. Plan for upgraded front axle shafts. Like the real SCX24, it does have ball bearings throughout. It also has aluminum high clearance (bent) links.

The kit is shipped as a roller (fully assembled with the wheels on) but it is only loosely assembled. Think of it as an assembled kit which serves as its own manual, because you won't get one. About those axles, they are where most of the money is in a crawler so they are important, and these are not great. The rear axles are adequate, so I have no meaningful notes there. The front axle bearings fall out if the pins are taken out (and good luck finding those if you ever drop one outside, but this is standard SCX24) and the axle joint is a cup and slider type. You get to choose between having it run very rough while turning if you run no lube, or using grease which will trap grit and having it still be rough. Luckily there are lots of aftermarket front axle shaft options, unfortunately you will need two sets.

Quality is minimal here overall. The longest screws have a noticeably different fit from the rest of them, and the worm wheel in the axle has a tight fit with the axle housing and I suspect it is likely to grenade. The axles come dry (which is reasonable at this price point) so I stuffed the worm drive with Super Lube. I've been using this literally since my first RC car, and it's always been a good product. It's got no coloring in it and is very clear, so you can easily see metal shavings or other contamination, and I expect some. I only hope that the worm gears themselves survive so I don't have to try to source more. The way the axles are mounted, some of them (especially #3) have really wrong driveshaft angles that will cause problems, but there's a lot of adjustment holes in the frame to make it possible to solve that. 

I'll do that once more parts arrive; I'm waiting specifically for the Injora skid which allows you to reverse your transmission, at which point half of the links on the #2 and #3 axles will have to be disconnected anyway. This is necessary so that I can have the DashRC brushless outrunner motor facing forwards. It's possibly the best of several low-cost options under $40. I will power this for now with a LittleBee 20A BlHeli_S ESC which I have already programmed for use as a crawler motor, but this motor will supposedly do peak 50A so I'm going to go with a 30A AF32 as that is the current vogue, and they are very cheap. I'm also exploring servo options, "buy once cry once" is easier advice to take when there's only one! The stock servo mounts also have very little depth available, so they may also have to be changed in order to run any kind of decent servo.

My first RC (a Futaba FX10) came as a parts kit, and I built that from bits on sprues and parts in bags including putting together a relatively complex gearbox, so I'm not exactly dismayed by having to do some work. I do find the low quality of the front axle shafts and nonfunctional default axle configuration to be slightly off-putting. These aren't really show stoppers, but the axle shaft situation does mean having to spend another twenty dollars or so just on the chassis before it is truly functional. The links for the #1 and #4 axles are kind of precarious, and I've ordered some parts to help me explore a fix for that for some of them which involves carbon fiber rod; there's also a clearance issue affecting #2 axle travel with how the kit is put together which is probably fixable, but looks like it will require some Dremel work. One of the front axles (I forget which, #2 I think) was kind of sticky at some points because the links rubbed on the servo mount, which I fixed by filing the mount. Steering for the front axle looks good (with the cross linkage above the arm on the knuckle) but I'm really not sure how the second axle is going to work out, as there's very little room for clearance between the horn and the drive shaft. I don't even have the servos yet, but that's going to be interesting.

As one of the link screw nuts was missing, I got a Rampcrab screw and tool kit for only around $13, which turned out to be pretty nice. It came with not only with a custom box containing a very comprehensive supply of the hardware including wheel nuts and pins, but also shock oil, gear grease, thread locker, and a couple of hex drivers and a hex nut driver. Because the screw heads used are different sizes even when they aren't supposed to be, this was really not enough tools to work on this model, although it's close. I also have some old Integy drivers, and one of them happens to fit the screws that the small driver in the kit doesn't. I should have thought ahead of time about a screw kit, which is just a good common sense thing to get when starting a project like this. It's sad that the screws used on this 8x8 aren't better quality, because they are in theory really nice with their sharply knurled heads.

In theory I have or will soon (depending on order fulfillment time) have everything to get this truck moving around and steering. I have been a bit cheap about it, but I am willing to do some work. While these front axles are a bit cheap, upgraded shafts should liven them up quite a bit, and hopefully eliminate all of the excess drag in the drivetrain. I have it in mind for this truck to pull a semi trailer, probably using 1/14 Tamiya style parts which are getting cheaply knocked off now as well. Therefore I either need to put the battery in the cab, or hang batteries on the frame alongside the skid. Also in the interest of being cheap, I have resisted buying any of the spendy model kits that I've been eyeing to provide a hard body, but I'm having a hard time finding anything inexpensive in just the right scale. I've seen several of these (and similar) using Kei truck bodies, which are extremely available on Aliexpress, but I want something more bus or van-like that will cover and protect the motor. It will be weeks before everything is here, so I have some time.