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Tuesday, April 9, 2013

Marble Machine Goes Modular - The Elevator Column

Yesterday we built the pump to handle pushing the marbles, but now we need to get them on some kind of upward mobility. Marble machines work from gravity and momentum keeping the marbles moving through it's course. So they have to start high. So today I built the elevator column. In this first photo, you see the elevator column sitting beside the pump.
I took a closer shot so you can see that we added pins to the top of the pump that line up with holes on the bottom of the elevator column. This assures the elevator gets placed in the exact location every time. If it did not, there is a good chance that marbles could get hung up.
Speaking of things getting hung up, after I built the elevator it was time to test the pump and elevator assembly. I test each and every part as it's built. Besides being fun, it is a necessity. It is best to catch any problems exactly as they arise instead of later having to isolate a single problem within a conglomerate of parts.

I realized I had a problem with the pump. It worked fine yesterday while feeding one marble at a time. Now though, with the elevator in place, I was able to try feeding a steady stream of marbles by setting up a temporary trough. It would take one marble fine, then would catch the next marble between the piston and lower part of the cover hole and jam up instantly. That just would not do. So I investigated the issue.
What I determined was that the piston was dropping down just a hair too low, allowing following marbles to drop down into the hole on top of the piston before the slider had a chance to move the assembly aside. This was like throwing a monkey wrench into a gear assembly. It simply caught in the sum of parts and jammed.
I thought about scrapping the pump and starting over. Before doing so though, I took a coffee break and thought of an easier solution. I used a micrometer and measured the difference between the marble at it's lowest point and the top of the slider assembly, and determined that it was only an eighth of an inch difference. So I sliced off an eight inch section of three quarter inch dowel on my table saw sled and carefully glued it in place flush with the bottom of the slider assembly.
Of course this required another extended coffee break while I waited for the glue to set up. I wasn't sure how it would work and kept thinking of an old saying I remembered from the Emergency Broadcast System, "this is a test, this is only a test". That scares me. I think I'm showing my age too much remembering these things and my kids haven't a clue what I'm talking about when I say things like that.

After the glue dried though, luckily, this fixed the issue and I could move on. We were cooking with grease now. Then I wasted about an hour just playing with the whole assembly. No, I don't play. It's testing. Yea, that's the ticket, testing.
So here is the whole assembly of the pump with the elevator column attached. As I showed with the pins earlier, the elevator column is removable. The reason for this is that later, when everything is done, the machine breaks down for all the parts to be stored in the base.
At the top of the elevator column is a turnout that directs the flow of marbles outwards, or inwards in this case, toward the base that all this will reside in. As the marbles reach the top and are pushed outward, the shape of this piece, along with the metal rod you see in the center of it, helps direct the marbles where they need to go.
Here was part of the "testing" process. I like how you can actually see the marbles as they rise through the elevator column.
Here is a closer view of it.
I got a message yesterday with a question about my using plywood on this machine and about the species of other wood I've been using.
Some people who know me or read my blogs know that I have a hatred for plywood. Whenever possible, I use nothing but solid wood. However, as much as I hate to admit it, plywood does have it's place. In some situations, such as the ones you'll see during the construction of this project, the stability of plywood just can't be matched with solid wood. Solid wood moves with weather changes. It doesn't matter what it may be sealed with. That movement is always present.
For example, you'll notice the base mount on the elevator column and the top and bottom of the pump  are plywood. This is a critical area where the placement of the parts always have to be perfectly the same as they were designed to be. In cases such as this, plywood allows the possibility to make it and rest assured that the wood will not move enough to make that future joining of parts a problem.
You'll see me using a variety of woods in this project, as I like to do in a lot of my projects. So far, except for the plywood, all the wood I've used has been sycamore. I chose it because it is a very stable wood for these moving parts. While it is not as stable as plywood, it has less movement with weather changes than some other wood choices I've tried in the past.
I will try to remember to state the species of woods I'm using in future installments of this build.


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