Experimentation platforms

Posted by Scott Ellis (216.87.95.64) on November 21, 2002 at 00:55:20:

Hi All,
A little while ago Dave Roberts suggested that I include a section on the website about test platforms and construction designs. And he offered to help get the ball rolling by offering up his own suggestions. I think it's a great idea, but until I can find time to create a new area on the website, we can just use the discussion board to get started.

Dave sent me some pictures and text describing his setup, so I'll post those here and then follow-up with commentary about my own setup.

Dave’s comments and pictures:

As promised, attached are pictures of the wheel and stand that I work with. It is very crude, but rigid and balanced. My work area isn't neat, but is functional. The wheel itself is 5 feet in diameter. I tried smaller ones but need room to work and not be so precise. If anyone wants to copy, they can upsize or downsize accordingly. I am sure there are others out there who have more functional and neater designs and hope that they submit them. To make a wheel such as mine, I offer the following suggestions:

1. Center shaft: Using all thread or standard steel rod is not recommended as they do not support much weight before bowing. I used a 5/8" O.D. hardened precision shaft, 24" long from McMaster Carr. They have a website.
2. The center shaft will need to ride on bearings (of course) and I used a flange mount with set screw lock from McMaster Carr #6244K52. This lets you shim under the bearing to get good alignment.
3. To be able to connect the sides of the wheel to the shaft, I used a 1/2" pipe nipple and flanges available at any hardware store. Some nipples will slide right over the shaft, others have to be filed on the ends as they compressed too much in the threading operation. The flanges can be bolted to 1x4's or whatever. I also drilled and added a 1/4 bolt through the nipple and shaft so the shaft turns with the wheel.

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Scott’s comments:

As you can see from the pictures, Dave’s wheel is huge! It makes a great testing platform because Bessler said the wheel’s power was proportional to its size. This means that the "magic" principle might be revealed more easily at larger scales. But such a large test wheel may not be practical for everyone. I use a 1' diameter wheel for most testing, but will be moving up to a 2’ diameter wheel soon.

My test platform consists of 3 main parts:

• The axle
  
  • A 1/2" diameter dowel rod clamped down firmly on a workbench and protruding over the edge about 6 inches
    
  
  
• The wheel
  
  • A plywood disk with a 1" diameter hole drilled in the middle and a speed bearing press fit into the hole. The disks are available at Home Depot in 1’ and 2’ diameter sizes. If you don’t have a drill press (like me!) you MUST have the hole for the bearing drilled at a machine shop. If you try to drill the hole with by hand your wheel will wobble. My local machine shop charges about $25 dollars for the first hole, and just a couple of bucks for each one after that. So I usually have them drill 3 or 4 disks at a time. Be sure to give the machinist the outer dimension of your bearing and tell him you want a press fit.

    I buy bearings at my local specialty hardware store (you won’t find them at Home Depot). Use the Yellow Pages and ask for speed bearings. When you find a place that sells them, get the biggest one you can afford. They can be quite expensive! Be careful when pressing the bearing into the wheel (and getting it back out). It will be very tight, and it’s easy to accidentally damage the bearing. Some sanding helps but be careful... the tight fit is crucial to an even, wobble-free rotation.

• A fixed surface (Optional)
  • This is just another plywood disk with a smaller 1/2" diameter (hand-drilled) hole in the middle, that is fit over the axle, pressed against the edge of the bench, and attached with a small L-bracket. This provides a fixed "mirror image" of the turning wheel on which to affix elements like ramps, pegs, etc. which do not turn but can interact with the moving parts. We don’t know whether Bessler used such a scheme or not, but it is conceivable. Even in a spinning drum, a clever design might conceal a fixed element somehow attached to the axle.

The setup described above works great for quickly and easily testing most 2-dimensional schemes. Lever arms and pendulums can be attached anywhere on the wheel, using the following method:

1. Drill a small hole in the disk and push a long narrow screw through.
2. Tighten a nut down on the screw to secure it tightly to the wheel.
3. Cut a piece of balsa for the lever arm or pendulum, drill a hole for the pivot point (drill in the dimension of the balsa that makes the hole as long as possible), and push a brass bushing through the hole. Then slide the arm on the screw and you have a nearly frictionless pivot arm that will stay in alignment and won’t scrape the disk as it moves.

Lately, however, I’ve been more interested in 3-dimensional schemes than 2-dimensional ones. I’ve been especially curious about how a "wobble" effect might be applied. Testing these ideas will require a new platform apparatus which I have been working on. But more on that later…

If you’re still reading this and have done any experimenting of your own, I hope you will consider offering up your own experiences and suggestions.

Best,
Scott

Follow Ups:

• Re: Experimentation platforms Charity 12:37:10 04/17/03 (0)

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