Turing Tumble Progress Update #9: The Second Sample
There's a lot to cover in this update. I'll start by walking you through the second iteration of the plastic parts that arrived on Monday. Then I'll explain the next steps and timing, there's an update on the Virtual Pack, and I'll save some juicy technical details for the end.
The Second Sample
It took significantly longer than expected to receive the second iteration of the plastic parts, but they finally arrived on Monday. We had about 50 things for LongPack to fix from the last sample. We were more than a little anxious, particularly about the ball release system. Last time it released multiple balls at a time. With our changes, would it work reliably this time?
The ultra-low friction of these injection molded parts is a blessing and a curse. I'm not sure how you can model their behavior before you make injection molds. CNC milled parts get you close, but not all the way there.
The package arrived on Monday afternoon:
It came in one of the old magnet boxes - this round was just to test the plastic parts, not the box. We'll get a final sample of the box in the next round.
And here's the board. Last time, remember how there was too much warp? The molders made a tool that puts pressure on the board immediately after it's molded to reduce the warp. You can see there still is warp there, but it does appear to be reduced. Also, remember the parts aren't made in their final color. They just used whatever plastic was already in the machine.
I took the board out and tried to put it together, but ran into the first problem right away:
It's missing a lip on the bottom that makes it snap into the other parts. Here's how it's supposed to look:
LongPack will fix that in the next round. In the meantime, I used my CNC milled standoffs to put the board the rest of the way together.
If you remember last time, the parts were really loose on the pins and wiggled around too much. This time they fit just right. Not too tight, not too loose. Also, it turns out the warp was reduced just enough to not cause any problems. It doesn't interfere with the board's operation anymore.
I put some parts on the board, held my breath, and ran it for the first time. Here's what happened:
The ball release mechanism worked! The crossover worked! The ramps worked!
Er...until a ramp fell off the board. In the video, I said that the ramps must still be too loose, but that actually isn't quite the problem. I spent a long time yesterday taking slow motion videos and trying to figure out what's really happening. It's a more complicated problem, but I figured it out and it should be fixed in the next round. I'll explain the problem and the fix for anyone who's interested in the technical details section below.
Then I tried a different setup involving bits. Last time, I couldn't even test the bits because the molders forgot to cut a section out of the arrow on top that's critical for them to function:
They worked perfectly! But what on Earth happened on the bottom? I've never had a ball get stuck there before. After messing around more with the board, I found that it happens only rarely, but frequently enough that I'll see if we can make a modification to stop that from happening.
So, as it stands:
The Board: The ball release mechanism works reliably, the parts fit well and turn smoothly. The warp is still there, but it doesn't interfere with its operation. We'll see if we can fix that rare problem where a ball gets trapped under one of the levers.
Ramps: Every once in a while they fall off the board, but they should be ok in the next round after a few changes (see Technical Details section below).
Crossovers: Every once in a while they fall off the board, but they should be ok in the next round after a small change (see Technical Details section below).
Bits: Good to go.
Interceptors: No problems, but this was a pretty easy one. :)
Gear bits: Last time there was a lot of sink near the teeth of the gear - so much that it left voids in the plastic. I made a modification to the part, adding little indentations in the places where the plastic was thickest, and it seems to have solved the problem. No more sink!
But, like I said before, the lower friction is both a blessing and a curse. It means we can connect 6+ gear bits together in a line and a single ball can flip them all. But it also means that if only two gear bits are connected together, they flip too fast. Sometimes that means they bounce back the other way a little, which can mess up the operation of the computer.
I'm not sure that's a problem we'll be able to fix without making some serious modifications to the part. And anything we do to make it work with two gear bits would make it stop working with larger numbers of gear bits. Fortunately, there's an easy way to make it work - if you only have two gear bits connected to each other, you can just add a third gear bit to the chain anywhere you want and it slows them down enough that they work reliably again.
Next Steps and Timing
Last time we had 50+ changes for LongPack to make. This time we have only 6 changes. We think there's a good chance everything will be ready to go in the next sample. So we asked LongPack to add the final texture to the parts and they're going to make them with the correct colors.
This last iteration took a lot longer than we expected. We were expecting 10 days and it took a little under a month. We were told the next iteration would take 5 days + 2 days for shipping, so if all goes well, we're hoping to get this into production next week or the week after that. If we begin production mid-December and production takes 4-5 weeks, we'll have the games on boats by the end of January. Unfortunately, that means our timeline is pushed back another month. Instead of February, we'll probably have the game in your hands some time in March.
The real key is to have our production finished before Chinese New Year begins. China shuts down for about a month starting a week into February. If we don't have it on a boat by then, it will be another month of delay while we wait for Chinese New Year to end. Fortunately, LongPack thinks there's a good change they'll be able to get it on a boat before then.
Virtual Pack Update
There was a request to add STP files to the virtual pack, not just STL files, so I created a new version of the virtual pack that includes the STP files. You can find it at the same link: https://turingtumble.backerkit.com/backer/digital_rewards
Also, if you haven't had a chance yet, take a look at community.turingtumble.com. jesusaurus has been working to make a version of the game that can be printed on home 3D printers. He cut up the board into 16 sections and posted the STL files so others can print them. It looks promising!
I thought some of you might be interested in more details on two key problems with the parts and how we're going to solve them.
The problem with the ramps:
I thought I'd start by explaining why the ramps are falling off the board and how we're going to fix them. It's a riveting tale of momentum and friction.
The ramps fall off the board now because they can rock back and forth too much. See the picture below showing the top side of a ramp placed on the board and the direction of the rocking that's causing the problem:
Here's how it falls off the board: After the ramp is pushed down by a ball, the counterweight returns it back to its original position. It stops returning when the pin running through the "smile" hits the end of the smile. When the pin hits the end of the smile, the whole part rocks - in the above picture, it rocks so the left side of the ramp moves toward the board and the right side of the ramp (the side with the counterweight) moves away from the board. When the counterweight gets pushed away from the board, it sometimes gains enough momentum to push the whole part off the pin (or at least it pushes it way down close to the end of the pin so that the next ball to hit it knocks it off the board).
The 3D printed parts and the CNC milled parts don't come off the board because they are not as smooth and the extra friction stops the parts from sliding off the pin. I don't think there's a good way to add friction to our injection molded part, so we're going to solve the problem a different way.
Right now, most of the ramp sits about 1 mm off the surface of the board due to the small, circular protrusion right here:
I put that protrusion there to reduce friction as the part turns. It used to help, but now it's the source of the problem. It acts like a fulcrum, and the part rocks back and forth over it. So to get rid of the rocking, we're going to remove the protrusions so that the parts sits flush against the board surface. If it sits flush against the surface of the board, it can't rock anymore. I tested this theory by sanding off the protrusions from a couple ramps and it did indeed solve the problem. We're also going to make the ramp slightly wider to keep it about the same width as it was with the protrusions. Here's a picture of the top of the ramp with those changes:
The problem with the crossovers:
Friction (or lack thereof) is once again the problem. In the case of the crossovers, the lack of friction makes it possible for crossovers to fall off the board when a ball hits them at just the right angle. Before, friction with the pin would keep them in place. Not anymore.
We're adding more material to the "smile" on the back of the crossovers. We're pretty sure this will stop them from being able to come off the board unless they are pulled straight off.
That's all for today. Hopefully we'll have another update for you next week or the week after that. If all goes well, the title will be "Turing Tumble Progress Update #10: We're in production!"
Paul and Alyssa