FRC 2023 jig

thingiverse

As part of the 2023 FRC competition, one of the game pieces is an inflatable cube. FIRST designed a jig that is used to calibrate the correct inflation level. The jig has precise internal measurements and weight. To use the jig, see https://youtu.be/55_o88WUCS8 The jig has to be exactly 20 ounces in weight, which is very heavy for 3-D printing materials, and hard to calibrate. To add weight and allow for calibrartion, my design includes four holders sized to hold US one cent pieces ("pennies"). I printed in PETG with 15% infill, and I found I needed a ballast of 136 pennies (34 per holder). You will need to print: * 1 x handle * 1 x left leg * 1 x right leg * 2 x front coin rack * 2 x back coin rack * 4 x lid You will also need 6 M3*12 countersunk bolts with hex nuts. Could probably use glue instead. The legs attach to the handle with dovetails, secured with nut and bolt. You'll see which side has the hex and which the countersink. The coin racks slot into the legs; again you'll see the countersink/hexnut pairs. The lids are a little fiddly to insert, but the end that prints uppermost is slightly tapered, so insert that end down; it's easier to insert the lids before assembly, and you can still get the coins in through the slot. Use a 6mm hex key to spin the lid onto the coins. Update: I have uploaded v2 versions of the legs and handle. These don't use a dovetail, but instead use a simpler half-lap joint (with filleting). This greatly increases the minimum cross-section area. My first version was eventually snapped at the narrowest part of the dovetail. V2 also uses two more bolts, and places the coin racks slightly closer to the bottom. I printed the new version in PETG with 15% infill as before, but this time I used 4 perimeters instead of 2 for additional strength. I required 125 coins for ballast (9 fewer than before).