Update on Design / Home Stretch Schedule

With the lockup date only nine days away, Chaos Theory is hard at work fixing problems that were realized during the 8th Milestone and completing the chute module.

The car module suffered from a lack of traction, so we are adding rubber bands to the outsides of the wheels. If that doesn't help, we will be reducing the gearing on the double gearbox that drives the wheels. The front gate proved to be a bit jerky and rotated too fast to be controlled, so we are reducing the gearing on the planetary gearbox that controls the gate as well as adding a pillow block to the end of the motor shaft to ensure that the drive gears stay meshed. Additionally, we will be raising the front chute slightly so that it does not catch on the carpeting.

Over Thanksgiving, the wooden superstructure of the chute module was cut and glued. This afternoon we milled the delrin sliders (to which the chute will be attached), and tomorrow we will be machining the rails which the sliders ride in. The chute itself will be bent as soon as we can get a waterjet appointment to have the metal cut.

Schedule: 
Tuesday, Nov 30: Finish installing pillow block on gate, begin working on drive motors, machine chute rails
Wednesday, Dec 1: More work on drive motors, preliminary assembly of chute, (waterjet?) cut the chute metal
Thursday: Dec 2: Tweak gate action, practice driving, (waterjet?) cut the chute metal if not already done
Friday, Dec 3: (waterjet?) cut the chute metal if not already done, bend the chute, practice driving
Saturday, Dec 4: Final assembly of the chute, test & tweak chute
Sunday, Dec 5: Rest
Monday, Dec 6: Practice with both modules on field, make any necessary adjustments
Tuesday, Dec 7: Practice with both modules on field, make any necessary adjustments
Wednesday, Dec 8: Bot lockup
Thursday, Dec 9: Competition!

Milestone 8: Final Chute Design

We've been thinking about the chute design a lot over the past several weeks, and decided to make some significant changes to it for our Milestone 8 presentation. The new design will attack the gap at the base of the lever from a more vertical angle, and will have an adjustable angle of attack so we can fine tune the interaction. The chute will be held above the starting zone by a pin, which will be pulled out by the six-speed gearbox. The chute will be gravity driven, although the configuration would allow us to add a tension spring assist if needed. The vertical chute will collide with the small slot, wedging itself deeply in and opening it wider. A detachable horizontal chute will allow for balls to be pushed from the tabletop into the vertical chute, where they will fall into the lever slot.

Here's a slow motion video of how the chute will deploy once the pin is pulled.

Progress on Car Parts

Today, we cut the acrylic parts for the car module on the Laser Cutter, as shown below at 2x speed. We will be cutting the Delrin parts for the car shortly.

 

First Week in the Shop

During our first week in the shop we focused on completing our wheel assemblies because we were in the process of slightly modifying most of our other parts in order to accept modifications made to the "gate."



To start, we cut and faced our wheel shafts to be 2.25" in length. Then we used the lathe to drill a hole in the center of two of them to accept the output shaft of the double gearbox. After making a slot for an E-clip and milling/tapping a 4-40 cross hole in the shaft we were ready to complete the assemblies. First, we pressed the custom bushings into the wheels. Then we used a quarter inch reamer to make the hole the correct size for press fitting.







Next, is where we ran into some problems. When pressing our machined shafts into our wheel/bushing assemblies the shafts failed under the compressive force of the arbor press. At first, we thought it was because of the cross hole, as that is where it failed, but upon machining two new shafts with the exception of this hole, we tried again with one. It failed again.

We seemed to have been the first group to try pressing anything, so we talked with Bob, John, Mike, and Toby to see what we could do. After measuring the machined shafts with a micrometer it was found that small imperfections brought on by holding them in the lathe or in a vice caused too much friction.

To solve this problem we used sand paper and a file to smooth out the part of the shaft that would go into the bushing. It worked great. So we decided to do this to our spare shaft that still had the cross hole which also worked. We were left with only one thing to do. Mill this hole out of the shaft that already had a wheel on it. We did this and now have four completely assembled wheels.