Make sure that you have all of the following components for the Motor Mount and Wheel Kit. If not, please contact Parallax sales for replacement parts.
There are two motor assembly sets included in your kit. These assembly details generally depict only one of the motor assemblies. You will need to assemble both sets – one becomes a “mirror image” of the other.
When the drive shaft / bearing assembly is all the way on the square motor drive pin, it should look like the above image.
Although the axle is precision-machined to fit with the motor shaft, sometimes the axles may slide on effortlessly or they may require a gentle tap from a non-steel hammer to seat them. This is due to slight variations in the manufacturing tolerances of the motor drive shafts.
When you insert the axle on the motor drive shaft it may seem loose and wobbly…this is normal. Once you install the Bearing Block and screw the assembly together, any “wiggle” will almost entirely disappear. This is well within the drive system and encoder’s resolution design parameters.
The bearing blocks are interchangeable. Therefore, each block can be used with either the right or left motor-axle assembly..
The bearing should slide smoothly (yet tightly) into the bearing pocket on the block.
The bearing will completely seat itself after you have installed and tightened the (3) socket head screws and standoffs in Step 5.
Note that the motors are mounted at an angle to the bearing blocks as shown above. This is by design, and results in a larger usable surface area on the Arlo deck, by minimizing the cutouts (for the motors) on Arlo’s main platform. There is only one orientation of the motor with the bearing block that will allow the three particular holes to line up for the bolt and standoff assemblies. This orientation is shown in the above photo which depicts the left drive unit.
This will require some “gentle, yet firm” taps from a small steel hammer. The drive pin should be centered side-to-side through the axle as shown. Be careful to not damage the (soft) aluminum axle.
Once the drive pin is installed, it is very difficult to remove. Double-check your work to be sure that you’ve done everything correctly up to this point.
You may wish to use a small piece of wood to support the axle as you “tap” the pin through the axle (above). When you’re finished, the drive pin should be centered in the axle.
Using (3) 50 mm hex-head socket screws, and (3) 1” x 0.5” standoffs, you will now attach the motor/drive axle assembly to each of the motor bearing blocks. The screws go into three tapped holes in the motor frame. Although there are four bolt holes in the block, only three holes will be used to mount each motor.
Although there are (4) mounting holes on each of the motors (as well as the blocks), only (3) are used in each drive wheel system.
Each encoder must have a 6-pin connector soldered to its PCB. Both PCB’s are exactly the same - as are the connectors - but they are assembled in slightly different configurations.
This manner of assembly allows both sets of wires to go in the same direction from the gear head towards the back of each of the motors (as we’ll see during final assembly and mounting of the Motor Mount and Wheel assemblies).
Be sure to match the wire color with the B-R-W color-coding on the boards. The white wires will be adjacent to each other in the center of the connectors when properly attached.
Although it's not required, labelling your cables with a small piece of masking tape (close to the unconnected ends of the cables) will make it significantly easier to make the DHB-10 connections later on in the assembly guide. Be sure to orient your encoders correctly when labelling. Left (LA, LB) and right (RA, RB) labels should correspond to your left and right sides.
The encoder board has a very tiny slotted sensor that must have the encoder wheel (that has already been installed on the drive axle) centered within its slot.
You should position the encoder boards over the encoder discs such that the discs fit in the center of the slot on the encoder sensor. The Encoder Disc should be slid tight to the axle’s “shelf” (the slightly larger diameter of the axle), as shown below.
This completes the assembly of a single motor drive unit. Duplicate what you just did for the other motor drive unit, and when you’re finished the result will be two separate motor drive units that are mirror images of each other (below)—one for each side of your robot platform. Please note that the image shown below does not show the motor units in their actual mounted configuration.
Each of the two aluminum wheel assemblies is comprised of: (1) precision machined two-piece split-rim set, (1) inner-tube, (1) rubber tire, and (6) flat-head 4-40 x ½” screws.
Each rim set consists of: (1) main rim, (1) rim ring, and (6) flathead #4-40 x ½” long machine screws.
WARNING! Never, ever put your fingers through the holes in the rims once the wheels are assembled. It may be tempting to carry an assembled Arlo by the wheel, but this poses a grave hazard to your fingers should the motors accidentally move the wheels.
You can choose whether to have the valve stem easily accessible from the outside of the robot (not shown), which makes it slightly easier to fill the tires if they ever need it. However, we recommend the “cleaner looking” appearance of having the stem “tucked” behind the rim, as shown here.
If you ever need to add air (very rare, if ever), you can simply remove the single bolt that holds the tire onto the motor drive axle to access the valve stem. The rim set uses #4-40 x ½” long flat head machine screws which screw directly into tapped holes from the “inside” of the aluminum main rim section. This provides for a very clean look when mounted on the Arlo Base.
The rims are precision-machined to hold the tires securely. You may have to push firmly to get the rim to fully seat itself into the hub of the rubber tire. Repeat this step for the other drive wheel.
Unless your Arlo is going to be carrying very heavy loads, there is no need to inflate the tires to their full rated capacity. Even though the tire sidewall indicates “35PSI”, we recommend no more than 10 to 15 psi for optimum traction, load carrying capacity, and shock absorption. We HIGHLY ADVISE using a bicycle hand pump (instead of a powered air compressor) to inflate the tires since the tube capacity is so small. It is very easy (and dangerous!) to over-inflate the tire using a powered air compressor.
Secure the Rims: Rim assembly best practice is to get all of the screws started into their respective threaded holes without fully securing any of them. Then, tighten each one slightly and continue this around the circle progressively tightening each screw, which will bring the two rim sections together evenly. Also, be sure to not pinch or bind the inner-tube while bringing the assembly together.
You should now have two drive assemblies that are mirror images of each other:
This completes the assembly of the Motor Mount and Wheel Kit. Set the finished drive units aside for now and go on to Section 2.