Courk's large marble drop thing - Guide me! (please?)

[Courk]

Formerly: "How much work is involved in making a piston?"

A small piston with a motor attached.

Where would one get a suitable motor?

[Lepton*]

Maybe you should give us some context: how big, how fast, how strong?

You can buy small project motors from electronics shops; slower ones are rare, but sometimes you can get little attached gearboxes. If it's not spinning too fast, you could cut the rotor and piston out of hardwood. The piston needs to be precisely aligned inside the shaft... maybe you could find a hand water pump and use pieces from that.

[Courk]

Speed isn't the biggest issue. A cycle every second or so would be good.

Strong enough to hold up a 2-3 foot high column of marbles.

Size: The marbles would be no more than 2 inches in diameter, so the piston wouldn't need to be very big at all.

[Courk]

A piston to do this: http://www.sentex.net/~mwandel/marbles/pump.html

[RSA*]

have you tried emailing that guy? His address is on his homepage: http://www.sentex.net/~mwandel/index.html

[Courk]

I did. I just know you guys are good at explaining things in terms I can understand, so I tried y'all as well.

[Quailman]

When my kids were eleven they made an electric motor with a piston for the engineering merit badge.

[Courk]

So I'll have to be 22 to make this?

[The Ragin' South Asian]

There were at least 2 of them. 44.

[Courk]

And all I have are doll making skills...

[Jack_Ian]

Does it have to be a piston?

It seems an Archimedes Screw would suit you purposes and would be easier to build.
It should be possible to use an off-the-shelf drill-bit and motor.

[Chuck]

Or a cam. A properly shaped cam can do anything.

[Courk]

[Dented Ford]

So do you already have a tube for the marble column? What are the dimensions?

[Courk]

Woah, there. You're way ahead on step 2. We're looking at step 1. Or, 0.1

I want to use "marbles" (wooden balls) that are between 1.5-2 inches in diameter. I want the column to be 6 or 7 ft. high.

Edit: I like how big 1 3/4 inches looks. Probably that size.

[Jack_Ian]

Co-ordinating the 2 moving parts, as per your animation, might prove a little difficult to engineer.
You might be better using a spring to push the marbles up and then you just have to worry about moving the single piece with a marble hole to the position over the spring.

The piece on top of the spring and the piece holding the new marble would me tapered in such a way that it first forces the spring-loader down while pushing the marbles up a little in the column.
Once the hole containing the new marble is positioned under the column the spring pushes it up from below into the column.
The edges of the hole that holds each new marble also needs to be tapered to force the spring back down again and the new marble further up the column on its return journey.

Does that make sense?
I will provide a diagram if you need it.

[Dented Ford]

[Courk]

[See next post, it was hard to see on white]

[Courk]

It was my understanding that the two moving pieces were actually moved by the same rotating force.



The white rotatey thing makes the yellow thing go up and down and side to side. The yellow thing then makes the orange thing go side to side.

[Courk]

I don't actually know what a cam is. I need the column of marbles to take up as little space as possible.

[Samadhi]

[Dented Ford]

[Courk]

So what would I need to look for in a motor to move a column of 1 3/4" balls up 6-7 feet? I'd prefer an AC motor, but there's other numbers that come with motors that I don't know much about.

Also, what kind of slip clutch thingy would I need? I'd rather have the motor move slower than the video on the site I linked to (I'd be happy with a marble popping out every second), and, without any real knowledge of stuff like that, I'd think the slower speed would help reduce the number of jams. However, I'd like to be prepared just in case.

[marcusI]

motorwise, you are probably looking for something like this: http://www.grainger.com/Grainger/items/3M097

At one marble per cycle 50 rpm means one marble every 1.2 seconds.
It should also be strong enough. If you look to the right in the second picture here:
http://www.sentex.net/~mwandel/marbles/machine1.html
You will see he is using a similar motor.

Looking at his diagrams, the radius of rotation of the "white spot" is roughly 3/4 of a marble diameter. The above motor should be able to lift
4 pounds of marbles at that radius and still have some power for piston sliding.

[MatthewV]

A cam is a wonderful device that can replace nearly all linkages. The main advantage of a cam is that it can provide complex motion based on a simple input.

Here is the idea I thought of. With some work, I bet it could work well.

[Courk]

how is the ball pushed out?

[MatthewV]

That is what the link (with the slider) does.

[Dented Ford]

The balsa wood question reminded me of this thread, and prompted me to mention I had an idea about the track, and the upward tube. Given a wide enough internal diameter, then I thought about using clear pvc tubing for the track. With the braiding reinforcement it could look almost like it was meant to be decorative, and give a flexible track both up and down the tree. You wouldn't have to try and hide the upward column, you could make it part of the decoration.

For small internal diameters, the tube is pretty cheap, but gets horrendously expensive (and probably unworkable on the tree) for the larger internal diameters, so I'm not sure you'd want to use 1 3/4 inch marbles. You'd have to have very bright primary colours though, and accept some tradeoff in the diameter versus cost, as the diameter would have to be somewhat more than the diameter of the balls in order to allow them to pass down the tube without sticking.

[Courk]

Sadly, I went to the tree festival for 2007, and... it sucked. I don't want to put all the time and effort into making this tree if the festival is that bad.

I do love making things, though, so perhaps I'll find other things to do with this info. I do like the PVC tubing -- it's really pretty. And actually... it might be perfect. I'll have to see it in real life, but... it would probably work...

[Dented Ford]

Well, hope it's a useful idea anyway. Hope suggesting you might like to try PVC doesn't get misconstrued, too, after the balsa thread!

[Courk]

You've been a member here for over a year. Surely you know better than that by now.

[Dented Ford]