Aluminum can breadboard

John Klayer · Post by **John Klayer** » Fri Apr 23, 2004 1:05 pm

The interferometer tests on the breadboard went well. Now I want to build one twice as thick expecting even better stability. I've been experimenting with ways to glue two cans together - nothing is ever as simple as it seems it should be. Do any of you have an opinion as to what would be better for making the second layer - plate,can,can plate or plate,can,plate,can,plate?
It would more practical to use taller cans, but I want to use what is easily available.

Michael Harrison · Post by **Michael Harrison** » Fri Apr 23, 2004 8:42 pm

Colin would have more input on this but it seems to me that a thin sheet of steel between the layers would be a good idea.

I wonder if setting the cans in the second layer offset from the cans in the first would provide any benefit. Something like:

o o o o
o o o o

if seen from the side. Imagine that there aren't any gaps between the cans. They're in the drawing so I can demonstrate what I'm thinking.

I don't have any concrete reason for suggesting this, it's just a strong gut feeling that this would help.

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If someone says it can't be done but they haven't tried it, don't believe them.
http://www.dragonseye.com/Holography

Colin Kaminski · Post by **Colin Kaminski** » Fri Apr 23, 2004 10:01 pm

I imagined 1/8" ply.

John Klayer · Post by **John Klayer** » Fri Apr 23, 2004 11:45 pm

Colin, are you suggesting a 1/8 inch sheet of plywood between the cans like this: plate, cans, plywood, cans, plate?

John Klayer · Post by **John Klayer** » Fri Apr 23, 2004 11:47 pm

I'll think about that idea.

Michael Harrison · Post by **Michael Harrison** » Sat Apr 24, 2004 6:26 am

Naturally the forum would destroy the ascii artwork that I sweated hours over.

Here's a picture

The more I look at the picture and think about it, the less I believe the offset will have any benefit. But then, I didn't have a sound reason for suggesting it and I don't have one for discouraging it, so I'll just refer you to my signature.

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If someone says it can't be done but they haven't tried it, don't believe them.
http://www.dragonseye.com/Holography

Dinesh · Post by **Dinesh** » Sat Apr 24, 2004 10:03 am

I think you're right on the offset idea. As we were discussing at the PCGGI, you don't want to set up harmonic modes. If you do set them up, you want to set up higher energy modes (ones that are more difficult to easily drive into vibration - sounds odd, but you know what I mean.) In this case, I think two cans on top of each other is an easier system to drive into oscillation than two cans displaced - especially if the displacement is "off-center".

Colin Kaminski · Post by **Colin Kaminski** » Sat Apr 24, 2004 11:57 am

Yes, That is my thought The neutral axis is in the center. I don't see any need to have any real stiffness there as it is only loaded in sheer. My only concern is that the OD of the top side of the can and the OD of the bottom side of the can are different. This makes for a bending force on the ply. I don't have a can handy but if the difference is only 1/8" then all is good. If it is larger then perhaps 1/4" ply would be better.

Colin Kaminski · Post by **Colin Kaminski** » Sat Apr 24, 2004 11:58 am

From a strength standpoint I would vote against an offset. Mostly because you can not make a 1/2 of a can to fill in the ends.

John Klayer · Post by **John Klayer** » Sun Apr 25, 2004 3:59 am

I decided not to go with a sheet of metal or even the 1/8" plywood that Colin suggests between my layers of cans. It seems to me that if I'm stacking two layers of cans and the neutral axis is in the middle, i.e. where the top layer and bottom layer of cans meet, then the bonding strength and contact area between the top and bottom cans is not all that significant, but I will use the best epoxy I can find regardless. The contact area not being important, I choose the minimal contact area for the cans to meet at the neutral axis and the maximum area where the cans meet the top and bottom plates. What I'm trying to say is that I'm bonding the ends that you drink out of together.