WLToys 12428 Crawler Conversion Assembly (SCX10 Clone Assembly)

 

This is an assembly guide for my WLToys 12428 crawler conversion project (SCX10 clone).  If you have questions about a standard SCX10, you can download the Axial manual from their website.

One important note, friends.  Most people who build a crawler want to make it their own.  That's the thinking behind this project, so you're probably going to want to do a bit of tweaking to get this thing just the way you want it.  My thought was that this would be a cheap way to make a crawler for a person with a WLToys 12428 or a bunch of parts kicking around.  If you are starting from scratch, you may want to order a cheap Injora crawler chassis or buy something like a Redcat Gen 8 (the Redcat is a bargain where I live but lots of other crawlers are decent).  Personally, I think a lot of crawlers are kinda pricey for what you're getting, but without any drive train parts you can't really build a reliable RC car of any kind (IMO).  3D printed gears are a big waste of time unless you have access to some killer printing tech.  Chassis parts and whatnot do work pretty well unless you want to bash your car.  I've posted a bunch of videos talking about this project, so give them a look if you're trying to decide what to do.

Guys, winter is the best time to get deals, so if you're a bargain hunter, figure out what parts you need to buy to build your project and keep an eye on Amazon and EBay for good deals.  If you spend a few months with your eyes open you can usually get the stuff you really need cheap and then build your rig when spring comes along.  Hopefully the noobs in the crowd learn enough from this and other resources to figure things out without too much trial and error.

Before we get into it, a few cautions are in order.

A few cautions:

• If you don't know what you're doing and feeling nervous, get help from someone more experienced in the ways of DIY.
• Take apart your RC vehicle at your own risk.
• Follow these instructions at your own risk.
• Use common sense and review instructions before you follow them.
• Knives can cut you.  Use caution.
• Hot glue can burn you.  Use caution.
• Brad nails can stab you.  Use caution.
• Rubber bands can shoot you in the eye.  Use caution.  Please tell me if this happens to you, I can always use a laugh.  It's funny if you aren't the victim.  That goes for just about everything on this list but a rubber band in the eye is the funniest.
• Screw drivers can stab you.  Use caution.
• Drills can drill you.  Use caution.
• Soldering irons can solder you.  Use caution.
• Molten solder is like lava from a volcano.  Use caution.
• Fast spinning wheels or drills or rotary tools can tear the skin right off you.  Use caution.
• Forcing something that doesn't fit can cause damage to property or personal injury.  Use caution.
• Connecting electronics incorrectly can release the smoke.  The smoke can't be put back in.  Use caution.  Take pictures if you don't know by heart how parts are connected.
• Batteries can cause fires when not handled properly.  Use caution.
• Some parts are not very durable.  Screw holes may not survive taking a screw out and putting it back in.  Disassemble your RC car at your own risk.

Some useful links:

You can find the part files on my Thingiverse.

Parts list.

Axle Build Guide.

3D printing guide.

Simple back half build guide.

Cooler back half build guide.

Notes:

1. The only place you  can waste much time during this build is the transmission/suspension area because some of the screws also hold on the floorboards.  Pay attention, use common sense and save yourself some time.
2. Test fit all parts prior to assembly.
3. Tap holes (cut threads) with a screw prior to assembly.
4. If using a power screwdriver to cut threads, go slowly to avoid overheating the plastic because the threads will be brittle if too much heat is created.  If the screw feels hot, the plastic got hot.
5. The 3D printed transmission mounts the same as an Axial clone transmission.
6. Use common sense when selecting screws.  My instructions are created from memory and I do check when in doubt, but sometimes memory is a fickle beast that tells you lies.
7. When it comes to support, you get what you pay for.

Part 1:  Transmission Assembly

1. Attach Gr_Gearbox (10) to Gr_Skid_V2 (8) using 2xM3x8mm screws (2, 12).
2. Install the spur gear and bearings from your WLToys 12428 into Gr_Gearbox (10) and test the fit with the bearing caps (11, 13).
1. If the bearing fit seem loose, use a bit/dab of rubber cement, B-7000 glue or similar to fill the gap.
3. If the fit is good, install the bearing caps using 4xM2x8mm screws (6, 15, 14x2).
4. Install the WLToys motor and mount (7) using 4xM3x8mm motor mount screw (9).
1. If you use an adjustable motor mount and different pinion, adjust the play so that there is approx 0.1-0.25mm of space between the gear teeth.  You can use a piece of paper to test, or eyeball the gap.  Turn the spur through a complete revolution to make sure it is not tighter in one spot.
2. This is a great time to pop in a cheap 45T (turn) 540 crawler motor because the stock setup is geared pretty high.
1. If you're running a clone axial gearbox I'd try a 27T or 35T motor (see my vid using a 45T).
5. Check the fit of the dust cover and grind/sand/file as needed (it should fit with the stock motor and mount).
6. Attach Gr_Dust_Cover_Mount (5) to Gr_Dust_Cover_W_Supports (1) using 1 M2x6mm screw.
7. Attach the dust cover assembly to the gearbox assembly using 2xM3x10mm screws (3, 16)

SCX10 Clone Transmission Orientation

Part 2:  Chassis Assembly

1. Loosely install the gearbox assembly (19) between the chassis rails using 2xM3x12-15mm screws (13).
2. Loosely install the left and right Ch_Front_Shock_Mount_V2 (12) and Ch_Bat_Tray_Mount (10) between the chassis rails using 4xM3x15mm screws (11).
3. If you are using a standard 3-wire servo, loosely install the servo mount (5) between the chassis rails using 2xM3x10mm screws (9).
1. If you are using the stock 12428 servo it is installed lengthwise between the cross brace and the bumper mount with the business end forward (WLToys has no servo reversing, so be sure to get it right).
2. The panhard bar should be installed parallel(ish) to the steering link (when viewed from the front the panhard bar and steering link should NOT make an "X"), so check your servo install.  If you do not have servo reversing you can mirror the panhard bar mount if necessary so that it can be installed on the proper side of the chassis.
4. Loosely install the Ch_WL_Front_Bumper_Mount (4) using 2xM3x12mm screws (9).
5. Loosely install the Ch_Bumper_Mount (18) using 2xM3x12mm screws (9).
6. Have a good look and see if we've missed anything that can't be installed easily later...  If not, snug up the screws so that the assembly is solid.
7. Loosely Install the left (mirrored) and right Ch_Floorboard_Rt (1) using 1xM2.5x12mm screw (2) and 1xChassis_Nut (14).
1. Only install the front screw for now because the rest also secure the transmission and suspension links.
2. Not too tight because the frame rails curve in and the floor boards do not.  This is not a big deal once more screws are installed.
8. Add two more M3x12mm screws to the transmission area to secure the floorboards, but DO NOT use the upper suspension link holes.
9. Install the servo with the horn to the right using the screws that came with it.
10. Attach Ch_Panhard_Mount_V2 (8) to Ch_Bat_Tray_Mount (10) using 2xM2.5x12mm screws (7).
11. Install 2x Ch_Rear_Shock_Mount (15) using 4xM2.5x12mm screws (16) and 4xChassis_Nut (14).
12. The battery tray that I initially included is for a shorty pack and mounts in the front.  I would not recommend using it in the front because I later discovered that the truck crawls better with the battery in the back.

The chassis should be done now and you should have a set of axles, links and shocks ready to install.

Part 3:  Suspension Assembly

1. Attach the links to the axles.
2. Attach the drive shaft ends to the axle and transmission respectively.
1. Be sure to use loctite on the drive shaft grub screws because they vibrate loose easily.
3. Test fit the axles/links assembly to the chassis to see if everything fits as it should.
1. Does everything line up?
2. Do the links move loosely?
3. Is the drive shaft angle good?  This is the limiting factor in raising the chassis.
1. With the suspension all the way down (running position, max extension), is the axle so low that the u-joint binds?  This is bad.
2. Lengthen the upper links or shorten the lower links or both so that the u-joint is free as the drive shaft rotates.
4. Attach shocks and test articulation.  You might want to wait on this until the truck is fully assembled because the weight of electronics, battery and body will make a difference.
1. If the shocks are too firm (poor articulation) use a mount point that gives more angle (make the shocks less vertical).
5. Once you get everything pretty solid, tighten up the screws.
1. You remembered to install the drive shafts, right?

Part 4:  Electronics

If you want to play in the mud, you'll need to put in a bit more effort than I did if you want your new rig to last.  In the pick above, the only real problem is the receiver (4) because the servo (3) and ESC (2) are waterproof.  The WLToys electronics are suspect out of the box if waterproof is what you're after.  Generally, submerging an RC car is going to kill it eventually... just so you know.  If you get something wet and it starts twitching, unplug the battery and let everything dry out (tub of rice, just like a cell phone) and there's a good chance you'll be ok.  Keep running it and it'll probably die for good.  Twitching is often a wet receiver issue and I have not personally had one fail completely when I removed power and let a twitchy one dry out.

I simply used two sided tape to stick the Power Switch (1), ESC (2) and receiver (4) to the floor boards.  This works great for testing.  You can also use hot glue and have a solid result that isn't permanent.

The battery tray (5, not included in the files initially, I made it for something else) is attached to the bumper mount and cross brace using zip ties.  I drilled holes in it as needed.  I found that running the battery in the back made for the best crawling performance so far (better than a front mounted battery).  Remember that getting a LIPO battery that is not well sealed wet can result in a fire.  

The cab body mounts are quick and dirty, but the front one works well, while the back one (tall thing screwed to the floorboards) has lasted longer than I even remotely expected.  You can also use a second front mount as a rear mount/brace between the shock mounts.

Check out my back half build guides to see what I did about body/cage installation.

That is all.

Wrench to drive or drive to wrench?