Gearbox & motor mount
The kit version of the SCX10-II comes with the 2-speed gearbox housing, but doesn't include the 2-speed guts. Every axle has ball bearings which is good, but the fit of the bearings is a bit tight, so I had to make sure they had to be aligned perfectly or they wouldn't seat properly. Again, the instructions are perfectly clear so pay attention to the bearings, use plenty of grease and building the main gearbox will be a breeze. Here too the hardest thing is screwing the fairly long screws into unthreaded plastic components. The same goes for the transfer case and motor mount.
Once those were in place it was time to install the spur with its slipper clutch. And again, everything went as expected. The usual setup for the slipper spring (screw all the way down, unscrew 3 half turns) seems to work just fine. This part of the instructions also covers the installation of the motor as well. My cheap chinese Surpass Hobby motor fits perfectly. I ignore the advice to put a piece of paper between pinion and spur, as my experience is that this usually ends in less than perfect meshing, so I just do it by hand.
With the motor installed it's time to put on the spur gear cover. It looks ok and it keeps dirt and debris away from the gears, but Axial could have designed it to allow for a bigger spur. The included gears are 32 pitch and with big teeth like that, there won't be a lot of options to change the gearing as just a couple of teeth extra would make the spur too large to fit under the cover. In addtition to that, the design of the gearbox and the position of the motor limit the adjustability of the distance between pinion and spur, even further limiting the grearing options. All while I'd expect people to gear down further to improve crawling performance. But as this is my first crawler build, I'm not going to worry about this too much now.
What does worry me, is that while screwing on the spur gear cover, the screw hole on the motor mount cracks. <insert powerful terms of mild annoyance here> One email to the vendor of the kit and I get a reassuring answer: "Send us the part number, we'll send you a replacement part". Great service. As the crack isn't really going to affect the working of my rig, I decide to continue the build and replace the motor mount later.
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| Cracked screw hole |
Central driveshafts
Building the driveshafts does require a little attention, as they are different lengths for front and rear and additional parts are included for when you want to shorten the wheelbase of the kit. But other than that, it's just a matter of sticking to the right order of things. The driveshafts are pretty sturdy, but they are plastic, so I'll have to see how long they will last.
Once they're assembled, they get mounted to the output shaft of the gearbox.
Chassis part 1
Now it is almost time to put everything together. There's some preparation to be done first, like mounting the skid plate and "motor mounts" on the gearbox and fitting the servo- and batterymounts together. Also the servo is installed. I recomment that if you build this kit for yourself, you make sure that at this stage, you pop in the battery you plan to use and adjust the battery positioning tabs accordingly. This will save you a bit of a hassle trying to adjust them later on.
With the preparations done, we can start mounting everything on the left chassis rail. For parts like the bumper mounts this is simple. For other parts it's a little more tricky as multiple parts are held on by the same screw. Like front shock hoops and battery/servo mount or side plates and skid plate. It's not really a big deal, but if you use standard L-shaped hex keys (like I did), you're going to need a little patience. Also pay attention to how you run your servo cable. If you don't pay attention now (like I did) you're going to have to go through all the frustration of the L-shaped hex keys vs. side plates all over again.
Once everything is mounted to the left chassis rail, the right one is pretty easy, as everything is already supported.
Next up are the axles. The links are bolted to the skid plate, which isn't very complicated, unless you count more of the L-shaped hex keys vs. side plates frustration. Man, maybe I should invest in a set of decent hex key drivers. And don't forget to connect the driveshafts during this process.
With the links attached, it's time to install the shocks. Right away I notice the adjustment rings on the shocks binding on the shock hoops. As I plan on rebuilding the shocks anyway, I leave it like this and make sure to find some shims for when I do the rebuild.
After installing the axles and shocks, all that remains is connecting the steering rod to the servo and the chassis is ready to have its electronics installed.
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| The assembled chassis |
The electronics
Well, what's left anyway. It's just the receiver and the ESC. There's a water resistant receiver box on the left side plate. The receiver box has silicon seals for the lid and where the cables pass through. As positioning the cable in the seal is a bit finicky, I connect the servo and ESC cables to the receiver first. Then put the cables through the silicone seal and slide the seal into its designated slot. For the servo cable its a tight fit, but as the ESC will be stuck on the side plate right next to the receiver box, there's plenty of cable to spare. For now I just pull the excess cable throug the seal and wrap it up inside the receiver box.
There's space for an additional cable in the seal, there's even a part to plug that up included in the kit. Nice touch Axial!
Now that all electronics are present, it's time to connect the motor to the ESC and check if everything does what its supposed to do. So I hook up a small battery and check if everything works. Once that is done, I close up the lid of the receiver box.
Chassis part 2
The last few finishing touches are now mounted on the chassis. Bumpers, body posts and rock sliders are installed in this phase. Nothing special here, just make sure the parts are correctly aligned and fasten the screws. Next!
Click here for Part 1
Click here for Part 3
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