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Sheet Metal Tools


English Wheel

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.

A shot of thewheel - it stands 5' 4" high 

Detail shot 1 The big wheel is a cast iron caster - the little wheel we made from bar stock. 

Detail shot 2 

Detail shot 3 This shows how we worked the quick release on the lower wheel 

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 Profiles 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 Richard 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 (but any errors that happen are entirely my fault!) 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 (circa July 2007). 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.  Click on the thumbnail photo to get a larger version.

Pile o' steel (less the 8" pipe)




8"Schedule 40 pipe being hoisted onto my motorcycle frame fixture The 7 foot length of pipe should weigh about 180(ish) pounds. The "invalid hoist" is rated for about 400 lbf.


Scribing a center line on the pipe with my Mitutoyo height gauge



Setting the angle The cuts were at 22.5 degrees.



Saw time! Preparing to cut the tube on my Jet "Roll-in" style band saw.



Cuts in progress I didn't have an easy way of clamping such a large OD pipe, but it had plenty of weight so with some welding magnets to help my hand pressure I was able to keep it pretty firmly up against the angle plate.


The sections of pipe after cutting them.



Blanking the bulkheads I'd stacked and drilled pilot holes and then cleaned them up with a 1/2" end mill. Those are lengths of 1/2" round stock maintaining the alignement. The circles show the inside and outside of the tube.


A shot of the plates being contoured on my Tree 325 Journeyman CNC knee mill with Centroid control That's my MS850 Mori Seiki lathe lurking in the background.


A closeup of the contouring operation The flexible tubing are parts of the Trico MicroDrop lube system.



Finished bulkheads with pipe



Close-up of a bulkhead on a section of pipe




All of the pipe welded up - back view




All of the pipe welded up - front view A 180 lbf piece of steel gets VERY awkward to position for welding!!!




Basic plan for the wheel frame



Here it is mid-May 2009 and I haven't done much on the E-wheel project over the last couple of years. I've been getting back in the garage recently working on a new motorcycle frame project and that is going to need a gas tank so it got me thinking about the E-wheel and when I reviewed the page I fiound myself thinking "didn't I have more photos than this?" I did find a batch of photos that I hadn't posted yet, and they do include some activity from a year ago. Hopefully in the not too distant future I'll be able to show a completed project.


Arm and quill mounting plates Here's the one that will go on the top of the frame behind the quill. The center hole will have a 1" rod welded in that will fit into a matching hole in the outer quill tube, removing one degree of freedom when the quill is aligned prior to welding. I will try inserting a section of rod in one of the tooling holes and if the quill looks to be in good alignment I'll leave that in place.


Arm and quill mounting plates Here are a pair of mounting plates for the lower arm. The one on the left has 1/2-13 tapped holes around the periphery (bolt shown in a hole) and the other has through holes. As with the bulkheads there are two tooling holes either side of the middle of the plate. The 1" hole will be filled on one plate with a short piece of bar stock. That will help register the bolt-up plate for alignment.

Preparing for welding The plates are on each end of the frame and straight edges are aligned with the tooling holes. I then sighted along the inner edges of both bars and adjusted the plates until both bars were parallel.



Preparing for welding As above from another angle.




Preparing for welding As above from another angle.




Preparing for welding As above from another angle.

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Preparing for welding As above from another angle.




Oops! I got so involved with aligning things that I forgot that this bolt would not be able to be unscrewed once the plate was tacked in place. Out came the hacksaw to remove the head of the bolt.


Welding The new welder was getting some use. The circle on the weld on the arm was an area where the old one had acted up and it needed some remedial attention.



Welding The quill backing plate tacked in place.




Welding Another precarious balancing act.



Welding The quill backing plate fully welded.


Welding As above, another view.




Welding As above, another view.




Upper wheel yoke The lower plate will be welded to the quill with another of the ubiquitous 1" alignment rods (shown next to it, along with the spindle for the Hoosier pattern wheel). I want to maintain the option of rotating the wheel 90 degrees. I also want the plate to be clamped up SOLIDLY hence the multiple 1/2-13 fasteners.

Upper wheel yoke As above with the wheel spindle in place.



Upper wheel yoke The wheel installed.



Upper wheel yoke As above from another angle.




In July 2010 I  got serious about finishing this project.  Making some parts that came out satisfactorily helped to keep the enthusiasm levels up!

Here are the parts for the "head" of the wheel.  The housing is machined, I've made threaded bungs for the gib adjusting screws, I've cut the CR steel plates for the gibs (I tried UHMW-PE gibs but they seemed to give both a lot of drag as well as not much stability for the quill) and some bars to weld into the bottom of the square tube so the gibs don't fall out.


Here's a shot of other parts before the square tube was machined.  The aluminum steering wheel is a dune buggy part.  Below the square tube are the three bolts that attach the steering wheel to the round drive cap (note the square hole in it), a radial needle thrust bearing, the top cap that is bolted into the square tube, another thrust bearing, the lead screw and top nut, the upper quill spring block (with threads for the lead screw) and the lower block that gets welded to the quill.  That has four studs with stacks of Belleville springs.


Here is a different view of the above parts with the lead screw and lower blocks assembled.




Here is a close-up showing the screw assembly with the quill to the right waiting to be welded to the lower spring block.



This shows how the internals stack up.




Here's some more progress in mid to late September 2010:

Welding time again!  I've got the head assembly plugged onto the mounting plate and aligned for tack welding.





Another view from a different angle.





A side view.





I'm not very good at out-of-position TIG welding so after tacking I turned the thing upside down to run the top and bottom beads.  You can see several of the threaded bungs for the gib screws and the plates welded to the bottom so the gibs don't fall out.




Here I've welded the upper wheel mounting plate to the bottom of the quill.  Before I did the welding I milled a square frame into the top of the plate, deep enough to remove the mill scale from the hot-rolled plate.  This also gave me a nice square recess to make it easy to center the quill.



I didn't get any photos while I made the legs and the mounts for them so here are some quick photos of the machine once I got the legs bolted on.  Hmmm, in real life it is a lot taller than I was expecting.




This is the lower wheel holder and the "socket" that gets welded to the tool arm.  A set of spherical washers goes above and below the holder so that it can be clamped at different angles to ensure alignment with the upper wheel.  Both the holder and base are tapped for set screws to securely position the holder both in the block for sideways adjustment and axle alignment.


A different view.





A close up view.




Set screws installed.




The complete assembly.





Another view of the assembly.





Here is a Hoosier Pattern 2" wide by 3" OD by 6" radius lower wheel sitting in the assembly.  That's a transfer punch that was handy and the right size, and not an actual length of .5" rod that will be used as the wheel axle.



This shows the fixturing bar mounted in place.  The spherical washers have been removed and the wheel holder is clamped directly to the base.  The set screws in the base have been adjusted to center the wheel holder.




Here's a closer view.  A/N washers are used to space the bar from the right side and then that is clamped up.  The punch in the axle slots aligns that portion of the assembly.




This is the tool arm mounting plate on the chassis.  The white material on the chassis is "Must for Rust" surface prep.





The mounting plate the tool arm will be welded to is sitting on top.  The 1" bar sockets into the 1" hole to help alignment.





The surface of the mounting plate has been scuffed to remove the hot-roll surface.





Here the lower wheel mount assembly is hung from the upper wheel axle, giving me something to shoot for with the tool arm.





Another view of that.





To make the tool arm I recycled some 4" x 4" x .5" angle I had around from an earlier project.  I welded it together to make a 4" x 4.5" box.  It has a few holes drilled in the angle but I don't see them likely to make a significant difference, and it saved me going out and buying more material.  The arm weighs about 35 pounds and as has been the case with a lot of this project getting it positioned without hurting anything (other than some scuffs in the concrete floor) has been a challenge.


Here is a closer view.  That's a Honda CR125 engine sitting on the chair.





I had to do some filing/grinding at each end to get a good fit.  You can see one edge bead where the angles were welded together.





A closer view of the other end





Hooray!  All the welding is done!  You can see that I added a piece of plate as a tension member to help support the tool arm under vertical loads.





Another view of the completed machine.  I still need to make the locking bars for the spring-loaded quill, and during the next bit of warm weather I'll brush a coat of paint on everything.  I'll add a few more photos after that happens.




Here's the machine after painting.





A closer look.   I live near the beach and the upper wheel had already picked up a dusting of rust in several areas, thankfully none of them on the rolling surface.  I cleaned that up and I've wrapped the upper wheel, after spraying it with LPS3, with cling wrap.  I'd like to avoid removing the upper wheel between uses to store it away.  I'll also put a couple pieces of vapor barrier paper in a plastic bag and slip that over the wheel and  tie it off as an extra precaution.  The lower wheels will live in their ziploc bags inside the boxes when not in use.


An intermediate close up.





A different angle.





Here is a closeup view of the head.  You can see one of the two spring lock-out bars halfway inserted between the spring blocks.  When fully home they'll disable the springing in the quill.  The aluminum steering wheel is a dunebuggy part, and I wasn't aware when I ordered it that it had those funky rivets stuck on the underside.  Oh well . . . .



A closer view showing one of the numbers/lines I engraved at each quadrant on the round adjuster plate.  The white strip on the side of the tube is a bit of vinyl magnet.  That is easily moved to any location (front or side) that might be needed to align with a number on the adjuster.  With a 1mm pitch screw one turn of the wheel is roughly .040", so each number will indicate .010" movement of the quill.  I'll be able to easily interpolate to .001".  That does make for big adjustments in the wheel taking more turns, but I 'm not in a huge hurry, I thought the finer adjustment might be useful, and the 24x1mm leadscrew should hold up under more pressure than would be the case for a coarser pitch screw.

I think I'm done with building this project!
I've just done some testing to compare the sprung and unsprung modes on the wheel and it is pretty much what I'd expected.

The Belleville washers I'm using are: 0.750" X 0.255" X 0.0250" with .012" deflection and .049" height.  They are claimed to support a load of  76.9 lbf without any compression and will be flat at 114.3 lbf..    If you stack the washers so that large ends are next to large ends and the small end is next to a small end (they call this series) you maintain the spring rate but add each washer's deflection.  If you nest the washers inside each other (in parallel) you maintain the deflection of a single washer but the rates are added together.  I've got 4 stacks of 14 washers in seriesl so 14 X..012" = .168" total deflection.  They should take 4 X  76.9 =  307.6 lbf of pressure from the screw before they start to deflect and be flat after .168" of travel at 4 x 114.3 =  457.2 lbf of pressure.

Here's a link to a Wiki article on the Belleville washers:  http://en.wikipedia.org/wiki/Belleville_washer

I spotted the first design flaw.  I have the slots in the head for inserting the locking bars near the top of the quill travel.  The quill is actually at about 2.25" down when operating so to make a change with the locking bars I have to crank it back up nearly to the top to get access to the spring pack.  I should have continued milling the slots farther down the head tube to make for quicker access, or  milled an additional set of slots lower on the head.  I'm certainly past the point of doing anything like that now, but it may not be a big concern after having done some testing.

My test procedure was as follows:  I cut several 3" x 9" coupons from a sheet of .062" thick (16g) aluminum.  The sheet wasn't marked but it is either 100 or 3003.  I put a piece of duct tape across one short end and used that tape and my thumbs on the other end of the coupon as the travel stops.  I counted going from one end to the other and back again as being one complete pass.  I tried to put the track down the middle of the coupon, but as I'm not one of those people who can accurately space the tracks the overall path ended up being about .75" wide.  I used a 2" radius lower wheel.  I found the point where I could no longer push the metal sideways (no rolling) through the wheels and considered that as "zero" pressure.  That will actually be a few thousandths of an inch of "pinch" but it was an easy point to find.  I then took a small strip of  the vinyl magnet and put that on the adjuster wheel to mark it.  This ended up being at the .5 position but the starting number isn't important.
The metal should take some pressure before it hits the yield point.  .010" doesn't seem to provide much over that.

I checked both coupons and they'd thinned about .005-.006" in the track.  I'd expect similar thinning for similar shaping.

The conclusion I draw is that with a very flexible frame on your ewheel you will put a lot of effort into bending the frame instead of pinching the metal.  WIth the locked quill 200 passes with no more than 3/4 of a turn of the adjusting screw gives similar metal movement to up to 4 full turns of the wheel and 400 passes.

Keep in mind that this test was done with smooth coupons.  I have not yet hammered on some coupons and then compared how smoothing goes.  I suspect that it may be easier to push the dented metal through the wheels with the springs active but on the other hand that would seem to indicate less action taken to compress the metal -- instead of compressing the metal the springs will deflect.  On the gripping hand there may be some advantage to having some pressure all the time with the springs following the surface of the metal over the bumps instead of hitting just the high spots with no additional downwards travel of the quill when the springs are locked out.  And I may not be able to appreciate that difference if it is very small.  
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