Day four of our project begins, and with it the new challenge of the cherry dispensing mechanism. Our first idea and attempt is going to be a sort of “rack” of cherries with dowels through them. The dowels will be resting on two angled tracks, and a four-toothed gear attached to the motor will rotate to allow one cherry through at a time.
Prepare yourselves for a magnificent display of artistic prowess:
Our rough sketch of the idea.
This design doesn’t seem too hard to accomplish, but some potential problems are already apparent:
- As of right now, we have nothing to guarantee that the cherries will roll straight down the rack. They could possibly roll off to the side, though the size of the cherry should stop that.
- The size of the cherry might not be enough to separate the dowels individually.
- The rack may be intruding on the sprinkler shaker’s area.
We also did some work to stabilize the entire structure, since the very large weight of the sprinkler canister coupled with its height above the table made for an unstable system (see video from day 3!). Although we used a lot more pieces, it definitely seems more stable. Surprisingly, the cherry rack didn’t interfere with the sprinkles dispenser.
At first, the cherry rack seemed unusable because the cherry dowels wouldn’t fit. However, after a few slight adjustments we positioned the rack so that the dowels can be held in place and rotated through by the gear. Already we can see the main problem; when the dowel comes to rest on the gear, the other side continues down the rack and the whole dowel falls off. We may have to use another form of support to maintain a straight alignment.
Construction with four tooth gear.
After many different attempts at keeping the cherry dowel aligned, we concluded that we needed a different approach. The unbalanced nature of our four tooth gear simply couldn’t keep the dowels straight. We are replacing the gear with an impromptu paddle mechanism that should swipe one cherry through at a time.
Our dispenser immediately before addition of paddles.
Unfortunately, our paddle mechanism is just barely too long for one cherry, which results in it coming down on the next cherry and smashing it. We’re going to make a couple adjustments and then go for it.
Success! The cherry dispensing machine works well, contrary to our initial beliefs. Here is the video of the machine in action:
Movie on 2011-06-16 at 13.45
Sometimes the paddle gets stuck on two, but as of now the biggest problem we have with the dispenser is the fact that Maraschino cherry juice gets all over everything. We’ll most likely end up using plastic wrap to protect the rest of our structure.
Right now we’ve started the whipped cream dispenser, the last of our structures for condiments. The whipped cream canister is the heaviest of all toppings, but luckily we don’t need to move it around, only hold it still while we apply pressure to the nozzle. Unfortunately, as the chocolate sauce dispenser has proven, applying controlled pressure with these motors is quite difficult. Our two options are:
- Hold the canister still while we push on the nozzle
- Put a loop of some sort around the nozzle, and pull when we want to dispense
Just to keep a little variety in our constructions, we decided to choose a pulling device instead of a pushing device. That design seems like it would work better as well.
Construction on the whipped cream tower is going well, but the whipped cream container is going to have to be very high above the ground, which could cause problems. In addition, the container has to be very far out from the base. Hopefully we’ll be able to work around the limitations.
Initial construction of the whipped cream structure.
After contemplating a “garage” approach to the structure, we remodeled and put heavy support on the back of the structure so we could reach it out over the table. The large mass of the whipped cream can might cause a lot of tension on the structure and break it apart.
Day 4 Google searches:
- structures holding up heavy loads
Day 4 Conclusions:
Maraschino cherries are quite messy, but easily dispensed via lego motors. Even though we can only put two or three cherries on our machine, it works quite well and can be controlled pretty easily with sensors. Also, a whipped cream canister is extremely heavy, and very difficult to hold up with a Mindstorms kit. Additionally, we cannot allocate a smaller amount of whipped cream to a different container, like we could with the chocolate syrup or cherries.
To Do for Day 5:
- stabilize the whipped cream structure
- create a nozzle push/pull device
- brainstorm for the car/sundae carrier