Waterjet Files and Modifications
The parts “disk hub”, “disk cover”, “encoder plate”, “body plate”, “battery holder” and “roof plate” are all made using the water jet. Included in the WaterJet ZIP are files with the same names as above and the .DXF extensions. These files are to be used to cut the parts. The Bill of Materials lists which sheet metal is used for each part. The only water jet part that needs modification is the battery holder. The battery holder will need to be bent into a “square U shape” with a brake in the machine shop. See image below. Additionally, there is a piece of velcro(loop side) that is adhered to the base of this squared off shape in order for the battery to stay in place. The other side of the velcro needs to be attached to the battery.
There are a few parts that need modification. Namely, the “encoder disk” and the various standoffs.
- The encoder disk needs the three aligning holes cut into it. To do this, find a circular object in the lab that will fit in the center hole of the disk hub. With the piece in the hole, place the encoder disk on the hub so that it is centered on the disk as well. The alignment piece will help ensure concentricity. Once lined up, use the holes on the the disk hub (or disk cover if you wish) to determine where the holes on the encoder disk should be cut. You can then use a drill to make the holes. Personally, I drilled holes that were only slightly bigger than the screws used for attaching, but wound up enlarging them and manually tuning the encoder disk location to align it. Smaller holes on the encoder disk means tighter alignment, but needs more accurate placement of the holes, relative to the disk hub. Larger holes allow for more slop in the hole location, but increase the need for manually adjusting the concentric alignment of the disk.
- The supports also need brought to the right size. As can be seen from the BOM, there are two different standoffs. The back support will need cut to the correct length. The bottom support will need washers attached between the support and the plate to bring it to the right height. (This was the largest stock length available.) The top support, if used, should be close enough to the right height.
- In addition to the encoder parts, there is also some basic soldering that needs to be done in order for the PicoPSU power supply to attach as we wish. The power input cable needs to be cut approximately mid-way between the power supply and the end of the cable. Then, a male EC3 connector needs to be soldered to the “board” side of the cut cable. If this seems unclear, then see the image below. Additionally, a female EC3 connector needs to be soldered to the other end of the cable that has just been cut. This setup allows for a simple setup to switch between battery power and the AC adapter
The CAD files for these parts can be found here Waterjet_files
The encoder disk is assembled using three parts. A diagram of the assembly is shown below. Use three of the M3x16 screws to attach the disk hub, encoder disk, and disk cover to the gear, as shown in the diagram. The three holes on each piece will align all the parts together. In addition, make sure the encoder disk is flat and not warped when assembling the encoder. This can happen when the three M3x16 are tightened too much.
Use the included diagram to assist with assembly. First, attach the head to the plate with 3-48 screws and nuts. The head should attach on the inside of the plate, meaning between the plate and the plastic gear housing of the car.Then, use the two (or three) supports to attach the plate to the gear box of the car. The M3x35 screws run through the plate, through the supports, and screw into the gear box. There are three holes already there that will be used for attaching. The screws currently in the holes will need removed. Note that you may also need to use a few washers on the bottom support to bring the plate level. Also note that the bottom, back, and top designations for supports refer to relative position when looking at the gear thatthe encoder disk is attached to.