In this tutorial we are going to assemble our 2WD Metal Chassis. These are a bit more complex than some of our other robot chassis so a visual guide is a must. The chassis features a variety of different hardware so pay careful attention to which screws are required in each step.
About The Chassis:
This chassis is a little different than most we offer – rather than independently driven wheels, which allows for direction and speed control through individual control of wheel speeds, this chassis uses a single powerful drive motor and a steering rack similar to the drivetrain of a typical car.
While this kit does include a couple tools to help with assembly, we do recommend a few additional tools to make assembly a little easier. Screws this size are quite delicate and using the wrong sized screwdriver can cause them to strip out or wreck the finish.
We are going to start by assembly the rear motor and driveshaft assembly. The motor mounts to a very nice bracket that houses the rear axle bearings and hubs. If this sounds a bit complex: not a worry! We will be going through this step by step.
First start by finding the motor, the motor mount, and a small bag with two tiny screws. These screws differ from most of the kit as they have a countersunk head.
First we are going to insert the two bearings into their cutouts in the motor bracket. These are a tight fit and should be pressed from the outside in, so the flange is on the outside of the bracket as pictured.
Next, we can insert the axle. Pay careful attention to the design of the axle as one side has a much larger flatted edge; this larger flatted side is used for the final drive gear. Slide the axle through the two bearings.
Now we are going to install the final drive gear. This gear is held in place by a set screw that impacts the flatted part of the driveshaft. Having the set screw and flatted shaft will prevent the gear from simply spinning on the shaft, rather than spinning the wheels.
Slide the gear on to the shaft and align it with the motor gear. You will want to ensure the set screw is on the flat side of the shaft. Once it is aligned, carefully tighten the set screw using the small Allen key included with the kit.
Finally, we are going to install the wheel hubs. The two hubs are different lengths so be sure to install them on the correct sides. The shorter hub is used on the side with the gear, while the longer one is used on the opposite side.
Your assembled motor and axle should look just like the photo.
The next step will be the front steering knuckles and stub axles. These are the components that hold the wheels and allow the wheels to turn. We will need the two plastic molded knuckles and the bag containing the stub axles, inner and outer bearings, locking pins, and front wheel hubs. All of the bearings, pins and hardware should be in one bag.
Ensure the chassis is in the correct orientation – the front bumper mount should curve up and away from the base. Start by placing screws through the correct holes in the base and thread on the standoffs. Next, align the caps and lightly thread the screws. You will need a little flexibility to get the knuckles slide in, so don’t fully tighten them just yet!
Continuing where we left off in the last step, we will now add the knuckles. We will need both of the assembled knuckles from Step 3 and 4 x M2x10mm screws. In the next few steps, we will be using these M2 screws to cut threads into the smaller holes in the knuckles.
Important: install the knuckle in the correct orientation for each side! Line up the top hole of the knuckle with the remaining hole in the piece we just attached in the last step. These will take a bit of effort to get through, so be sure to use the correct sized screwdriver to avoid stripping the head of the screw.
To create the steering rack, we will first need to connect the knuckles to one another. This is done with a tie rod. The kit has two tie rods, for this we will be using the larger of the two. It will be attached using 2 x M2x10mm screws.
Tie rods can be adjusted in length by twisting them to unthread the middle bar. This is one parameter that is adjusted during a wheel alignment on your car. Imagine looking down from directly overhead – the toe is the amount the front of the wheels point towards (or away) from each other.
We want to have very minimal toe angle, so get both wheels lined up facing forward as straight as possible and adjust the tie rod to match the length as close as you can.
Since we are installing this tie rod below the knuckles, it is easier to flip the chassis over and install it. The end result should match the photo.
Start by installing the mounting brackets and ensure the servo orientation matches that of our photo. The shorter side of the “L” bracket mounts to the servo, while the longer side is used to bolt it to the frame. It is best to leave these untightened until the assembly is mounted to the chassis – it will ensure the holes line up without too much trouble on the chassis!
Finally, we will need to mount the servo horn to the servo. Pay careful attention to the orientation of the servo and the horn.
The servo brackets will align with the two holes on each side (immediately behind the steering mounts). The servo mount has M3 tapped holes, so carefully thread each through. Once all of the screws are started, tighten all 4 screws, followed by all 4 on the servo that we left untightened before. The servo should not move – once completed it should match our photo.
The upper tie rod connects the servo to the steering rack to the servo. We will need 2 x M2x10mm screws, 1 x M2 nut, and the remaining tie rod. The included nut driver tool will also be required.
To start, orient the tie rod as we have in the photo. You will want the ends offset by 90 degrees from one another. The length of this rod can be adjusted as well, so if you find it too short, it is a good time to make that adjustment. Ideally the wheels should point straight with the servo horn vertical once this is installed.
Insert one of the M2 screws through one end of the tie rod and thread it into the remaining hole on the steering rack (the right side of the steering rack when facing forwards).
Now, insert the other M2 screw through the hole in the servo horn and then through the tie rod. The M2 Nut can now be threaded onto the screw, completing the assembly. Do not tighten the nut too much, it should be able to rotate without binding, but not be so lose that it slides around.
Next, we will install the motor cover / rear mounting plate. We will need 4 x 35mm Standoffs, 8 x M3x8mm screws, and the rear cover plate. This is a great place to mount electronics, sensors, and other parts!
We will be using the 4 corner holes of the cover plate, so start by placing screws through the cover plate from the top (the top orientation can be seen in the photo). Thread but do not fully tighten the standoffs to each of the screws.
The final piece of the chassis itself can now be attached – the bumper! To attach it we will need 4 x M3x8mm screws, 4 x M3x5mm screws, 4 x 16mm standoffs, 4 washers, and the bumper. This bumper is made of a high density foam – so start by removing the cut-outs in the bumper foam to make room for the hardware.
Last but not least, let’s get those beautiful wheels installed! The fronts and rears used different hardware to attach to their axles. For the front wheels we will need 2 x M3 nuts and the included nut driver tool. For the rear, we will simply remove the screws already in the hubs, and install the wheels with the screws.