An English wheel is a device for shaping sheet metal. It has two wheels on either side of the metal. Typically, the upper wheel is "flat" (no radius or "crown" to the wheel face) and the lower wheel has a radius to the working surface. The wheel works by stretching the metal. The metal, as it stretches, moves into the free direction which is around the radiused lower wheel. By making many overlapping passes with very light pressure (heavy pressure leaves noticeable "tracking" marks in the metal) you can put shape into very large panels and have very little metalfinishing needed.
In the early 1990s my friend Craig Hanson and I built a pair of English wheels. The frames were made from 3" x 6" x 3/16" wall rectangular steel tube, and the post holder for the lower wheel was 2.5" OD x .100" wall round tube. Here are four photos of my wheeling machine.
That original wheel let me build several gas tanks, but I recently got a hankering for an improved version. Loaning the wheel to another friend who, when asked, agreed to buy it instead of dragging it back, helped to move that decision along.
I'd found the Metal Meet sheet metal shaping forum and I saw the Hoosier Pattern upper and lower wheel sets. They seemed to get very glowing reviews, so I bought a set for myself. I ordered the 3" OD by 2" width lower wheels, and an 8" by 3" wide upper wheel. They are VERY nice, nice enough that trying to make your own wheels by taking multiple cuts with the lathe compound and then filing/sanding the planar intersections a lost cause. It is a LOT less bother to just buy the Hoosier Pattern wheels, and you'll very likely end up with a much nicer set of wheels. If you tell them when you order that you learned about the wheels at Metal Meet they'll give a small discount that pretty well pays for the shipping.
Of course, a set of wheels without a frame doesn't do much good, so it was time to design a frame. I read through all the information I could find at Metal Meet and at other sites. One site that had what I thought was a lot of good information was Dave Propst's where he analyzed what the wheels actually did. I'd found that, as with motorcycling, metal shaping seemed to have a lot of "voodoo" concepts, so finding Dave's information in which he did a "what's the physics here?" kind of analysis was very much appreciated.
Most E-wheels have the wheels mounted at right angles to the frame, which with an angled lower arm as used on the Imperial Wheeling Machines wheels can allow a greater "reach" into a deep shape. However, this complicates the strains seen by the frame. If the wheels are "in line" with the frame then it largely sees fairly straight-forward bending loads, much like a C-clamp being tightened. With the wheels at 90 degrees to the frame you will also see torsion in the frame and sideways bending loads.
Most people build their E-wheel frames from rectangular tubing, and that can deal very well with the "C-clamp" types of bending loads. But rectangular tubing isn't as effective as round tubing for dealing with torsional loads, and many of the rectangular tube frames also seemed to not be overly concerned with the sideways bending loads. On the other hand, rectangular tube is much easier to cut/fixture than round tube. As with most everything else, there are trade-offs to be made.
I decided to make my E-wheel frame from round tube. Actually, I ended up using 8" Schedule 40 pipe, which is a nominal 8.625" OD by roughly .3125" wall. I decided on this size after using various information I found on Metal Meet that compared different wheels of various throat dimensions/tubing dimensions. Using the simplified model in the spreadsheet developed by Randy Ferguson I substituted the second moment of area information for different round tubes as calculated by Tony Foale's structural sections calculator, which is a truly invaluable resource for anyone wanting to compare the properties of different round or square section tubes or solid bars.
With a 29" throat my wheel should have a vertical "stiffness index" of 38 in Randy's spreadsheet, making it very stiff. However, the large OD round tube is also significantly stiffer in torsion and sideways bending than the commonly used rectangular tubing that is oriented to put the long axis of the tube cross-section to resist the "C-clamp" vertical loads.
I'm refining a design for an upper wheel carrier that has Bellville springs in it to allow the stiffness seen at the metal/wheel interface variable. I decided that having a very stiff frame and then varying "as needed" the stiffness at the wheel made more sense than building a frame of some unspecified flexibility and then hoping that it gave an appropriate stiffness for whatever metal/gauge I was trying to work. It does appear that thin aluminum and thick steel sheet will want a quite different stiffness at the wheels, so I've tried to accomodate that without compromising control of the wheel positions by the frame.
Tony Foale gave me sage advice on this project as he does on many of my projects that can benefit from advice from a degreed engineer with significant practial experience. He recommended mitered joints (instead of "fishmouthed" fittings) and suggested I put a bulkhead of roughly the same wall thickness of the tube in each joint to stabilize it. The local steel place didn't have 5/16" plate so I decided to use 1/4" as "good enough".
Since I've got a CNC milling machine I decided to get fancy with the bulkhead plates. In Alibre I drew up the ID and OD ellipsis that resulted from the 22.5 degree cuts. I made the ID ellipse just a little bit larger than the ID of the pipe. I also put a series of tabs on the ellipse. My thinking was that thick tube like this would normally need a good bevel on the edges of the pipe to ensure full penetration. By making the bulkheads in this fashion I have the tabs to ensure the sections of pipe would be well supported so they wouldn't be as prone to "pulling" when welding, and the gap between the sections made by the bulkhead eliminated the need to bevel the pipe. Having the ID of the pipe a little less than the small elliptical section of the bulkhead would hopefully keep the argon from my TIG welder from just falling out of the joint.
I must admit that I had a bit of a cock-up. The bandsaw cuts very straight, but the blade isn't exactly 90 degrees to the table. Since I had to reverse the pipe sections to get the opposed angle cuts that compounded the slight error. When I did the first two sections (with bulkhead between) I was focusing on getting a very good fit between them, and it did come out pretty much exactly to the 45 degree included angle (twice 22.5 degrees). I was very pleased! However, I forgot that the important thing was keeping the planes of both ends of the pipe normal to the frame fixture base. Reversing the cuts doubled the error, and I ended up having to make 90 degree cuts across the pipe on either side of the bulkhead on that first section so that I could "clock" the ends into squareness. So I got to do two more circumferential welds than originally planned. Oh well . . . . .
I'll also mention that my elderly but up to now reliable Miller Gold Star 330 A/B/SP TIG welder expired midway on this project. The high frequency as well as the argon flow control both started acting up, so I had some delay while I moved the old welder (repairable, but I didn't want to bother) to a new owner and waited for the delivery of my new Miller Syncrowave 250DX.
Here are some photos of how far I've gotten to date. They range from a pile of steel to a pretty complete basic frame. I've included a side view drawing that I'm working from.
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