Wheeling Machine Wheels

Copyright © 2003 Dave Propst. All rights reserved.

Revised 4/17/2003

Introduction

Presented in this article are a few comments about sheetmetal wheeling machines in general and some specific setups in particular. Understand that some of what is presented here applies to certain specific tasks. None of the information presented is meant to suggest that the devices described are mandatory for doing basic, traditional work with a wheeling machine. In fact much of what is presented is a function of the choice to build panels in large sections. Building panels in multiple smaller sections is certainly a viable alternative as well.

For the benefit of those not familiar with all manner of coachbuilding tools, a wheeling machine is a device that forms curves and shapes in sheetmetal stock so as to create body panels. The sheetmetal is forced between two wheels which are mounted on a framework. The terms English wheel, e-wheel, and wheeling machine all refer to the same tool.

In reading the following text it is important to not subconsciously transpose the words 'diameter' and 'width' or the words 'upper' and 'lower'. Misreading these words will completely change one's mental image of what is being said. It is very easy to do this unless a conscious effort is made to not do so since these words are of necessity used many, many times in this article.

Wheeling Machine Upper Wheel Size

In the use of a wheeling machine, the concept of fine-tuning a multitude of lower wheels to specific tasks is universally accepted, even expected. On the other hand, much less development work is done on the upper wheel. The usual and long-standing assumption is that a single upper wheel of any arbitrarily chosen size will perform any and all operations with entirely successful results. On those occasions when the subject of much wider than normal upper wheels comes up, the need for and even the validity of such wheels is sometimes questioned.

Many comments made about the pro's and con's of extra wide upper wheels are not based on practical experience. It is wise to check whether or not a source making a statement about extra wide upper wheels a) has such a wheel, b) has ever used one, c) has any first-hand knowledge at all of one. In some cases the answers to these questions will be in the negative. Generalized, unfounded comments about wide wheels sometimes are heard and passed on repeatedly until they become accepted as fact. An even greater but not-so-obvious reason for confusion about this subject stems from the fact that many e-wheel users seldom perform tasks that to any great degree actually favor a wide upper wheel. This altogether 'eliminates' any pronounced advantages such a wheel could show in either theory or real-world comparison to an upper wheel of more typical width, leaving only the vague, generalized or suggested advantages/disadvantages spoken of. Given these factors, is it at all surprising some are of the opinion that wide upper wheels offer minimal, if any, advantage over standard width wheels? Would it not make sense to at least consider the opinion of those who do use such wheels before deciding whether or not they are of value?

While it's unlikely anyone would ever find need to experiment with as many different upper wheels as lower wheels, this is one more instance in which the idea that 'one size fits all' is short-sighted. This is true from both ends of the range of possible wheel widths. A wide upper wheel cannot perform some tasks as well as a narrow upper wheel. Conversely, a narrow upper wheel cannot perform some tasks as well as a wide upper wheel.

For the purpose of quantifying some values for differing widths of wheels, the use of some entirely subjective ranges in one-inch increments is helpful. This is not to suggest these are the only acceptable values. Its just a means of relaying some specifics for the sake of comparison.

A narrow wheel is 2.0 to 3.0 inches in width. (Many average-to-smaller machines are in this category.)

A standard wheel is 3.0 to 4.0 inches in width. (Probably most heavy duty wheeling machines for automotive work fall into this range.)

A wide wheel is from very slightly less than 5.0 inches to anything beyond that.

Please note that many English-wheel users would classify a four inch wheel as a wide wheel whereas here it is considered merely a standard size. This is because a 4.0 inch wheel is not wide enough to achieve some of the results that will eventually be described here. To this end, when reading through the ideas presented here it helps to visualize in extremes of width, i.e. 2.0 inches or less versus 5.0 inches or more instead of 2.0 inches versus 3.0 inches. Also consider that these sizes are relative to the shaping of normal automotive panels. Certainly panels for scale model cars, pedal cars, and other downsized applications would use a different standard of measurement. Yet another standard would apply to the other end of the spectrum, that being heavy duty applications such as industrial, some aircraft, etc.

This brings up an important point. When considering any aspect of a wheeling machine, whether it is upper or lower wheel size, bearing size, axle size, frame size, frame rigidity, or even technique it is wise to avoid the assumption that one size does fit all. It directly follows that when building a machine it is important to focus on what it will actually be used for instead of designing either to some worst case scenario that ends up never materializing or to underestimated force requirements. For example, it is not altogether uncommon to see wheeling machines with bearings (particularly on the upper wheel) capable of loads ten, twenty or even fifty times that which will actually occur in the application. The result is that for the entire work history of the machine, the operator, in the process of building panels of common 18 to 20 gauge mild steel, uses extra effort to overcome extra drag and extra inertia inherent in the overly large capacity bearings, axles and wheels. Yes the machine is 'loaded for bear' but the bear never comes! Meanwhile foot-pounds of manual labor energy are expended to no productive end. Even if the 'bear' does come at some point, does it not make more sense to design and build a machine for what will occur 99.9 percent of the time? Custom components can always be built, rented or borrowed to deal with the 0.1 percentile factor when it occurs. This isn't an indictment of 'overkill' of quality/strength/materials in equipment design. Its more a criticism of using a big hammer when a smaller one is better suited to the task. The reverse scenario, a light-duty e-wheel in a heavy-duty application can be less than enjoyable also.

With all of the above in mind, consider that the advantages of wide upper wheels are often described as follows:

Reduces effort required to run roughed-in panels through the machine. This is usually accompanied by an off-road tire analogy suggesting that the wider wheel will negotiate over the 'bag of walnuts' rough-in work with less effort on the part of the operator in the same way that wider off-road tires are able to travel over rough surfaces more easily.

Aids in guiding large, wide parts such as roof panels and large door panels through the machine.

Prevents crease-type damage to large, wide parts such as roof panels and large door panels especially in one-man operation. 

Please note that at this point in the discussion this is not an endorsement that any of these listed points is true. It is merely a list of the commonly claimed advantages.

The next sections will look at these concepts in detail.

The Off-Road Tire Analogy

Typical definition of the word 'analogy' : An argument or explanation based on the assumption that if two or more entities are similar in some ways, they are probably similar in other respects.

A realist's version of the definition: An argument or explanation based on the assumption that if two or more entities are similar in some ways, they are probably similar in other respects -- although they may well not be similar at all in which case a misleading 'apples and oranges' situation develops.

Using analogies to explain technical matters sometimes doesn't work as well as expected. This is because nothing is ever simple and the validity of the comparisons often falters on close examination. Before long the discussion is about the analogy instead of the subject at hand.

In general, using motor vehicle tire examples in an analogy for explaining wheeling machine wheel widths and diameters presents a couple problems.

1) To overstate the obvious, motor vehicles do not have and are therefore not influenced by small radiused mandrel wheels attached by a framework to the underside of the tires! Wheeling machines do have such mandrel wheels attached.

2) Most passenger car, race car, and SUV tires are not really all that unlike one another in diameter, so, dramatic and obvious real-world performance differences attributable to diameter are difficult to visualize.

With respect to problem number 1, the off-road tire analogy specifically is not without additional problems at least when used as it is most often presented. The suggestion made in this particular analogy is that a sheetmetal panel with roughed-in, 'bag of walnuts' irregularities equates to an irregularly bumpy, rock-filled off-road surface. The off-road scenario most similar to this is racing or driving on dry, rocky, rough, irregular terrain. Let's call this 'bumpy, dry off-road'. For this type of off-road driving, application specific tires are not inordinately wide. What they are is tall. Meaning large in diameter. This is in contrast to low-traction and flotation applications such as sand drags, sand hillclimbs, deep mud, deep hard-pack snow and similar conditions where tires are indeed wide, at least on the driven axle(s). These conditions are typically not all that bumpy so let's call this 'smooth flotation off-road'. These very points can be easily verified by simply paging through a couple of off-road/SUV magazines and observing pictures of tires in use. This is not to say there are not tires which are attempts at universal application, nor that sand tires can never be used for rock crawling or vice versa, but let's hold to designed-for purposes and application specific use of these specialty tires in this analogy.

In 'bumpy, dry off-road' travel, for any given width a tall tire's total potential contact patch is greater in length than that of a small diameter tire. Consequently, the taller tire's longer potential contact area spans across irregularities better than a smaller diameter tire's shorter contact area. The large diameter tire reduces the effect of obstacles in comparison to the smaller diameter tire. Top speed of the vehicle is therefore potentially higher because: a) Less horsepower and/or 'air time' is required for fighting the obstacles. b) The suspension has less work to do in the process of maintaining directional control. In this same 'bumpy, dry off-road' application, the wider a tire is the more obstacles it will hit compared to a narrow tire. The more obstacles the tire hits, the more horsepower required to achieve or maintain a given speed. The more obstacles the tire hits, the stronger, more durable and more effective the suspension needs to be in order to maintain control of the vehicle. To sum up... in this type of off-road racing or driving, the concept is for the tire to be narrow enough that it tends to slice through and between obstacles instead of hitting everything in the vicinity head-on with a super-wide section width as found on a flotation tire. At the same time, the tire needs to be reasonably large in diameter so it can better traverse those obstacles that it invariably does hit.

This all means that as far as tire/wheel width, even the stated axiom in the off-road tire/wheeling machine analogy IS IN ERROR! (Axiom: A statement accepted as true as the basis for argument or inference.) This since wider tires are, on average, not the first choice for bumpy, off-road surfaces. They do not make bumpy, off-road surfaces easier to negotiate. They make negotiation of such surfaces more difficult. Likewise the conclusion reached in the analogy on this point as it pertains to wheeling machines is in error. Wide upper wheels on a wheeling machine do not unconditionally create a circumstance in which planishing of roughed-in 'bag of walnut' panels requires less physical effort from the worker.

With respect to problem number 2, to illustrate the effect tire diameter has on performance, ideally two real-world examples having dramatically different tire diameters would be used. Unfortunately it is a struggle to come up with two such motor vehicles, off-road or any other, that are not also greatly different in weight. While a comparison of say, a small go-kart being driven off road with a large dump truck being driven off-road would provide the desired huge variable for tire diameter, vehicle weight would ruin the comparison unless tedious special conditions were described. Most off-road rocks or irregularities that would serve to very severely bounce the go-kart about would likely be summarily squashed into the earth by the hugely heavy truck. The large diameter of the truck tire would not always span the obstacle so much as the truck's weight would flatten the obstacle.

If an analogy must be used for the effect of diameter differences, one much more easily visualized or even demonstrated is that of indoor versus outdoor utility carts. An indoor cart with a hundred pound load on a smooth concrete floor will perform very well indeed with its small three-inch diameter wheels. Trying to pull that same cart across a gravel drive filled with ruts and potholes would be so tough as to cause one to wonder if it would not be easier to just pick the load up and carry it across the driveway. The same payload in a cart made for lawn and garden work, the style having very large diameter bicycle-like wheels/tires, could, entirely because of that larger wheel diameter, be pulled across the drive quite easily even though the tires may be similar in width to the indoor cart. (This analogy though, if applied to wheeling machines, still ignores the influence of the lower wheel of the machine.)

This commentary does not purport to be a thorough explanation of off-road tire performance. It is only meant to illustrate that the matter is very complex and that differing off-road conditions demand tire parameters at times contradictory even to parameters for other off-road conditions-- let alone wheeling machines. Broad, sweeping statements relating to wheeling machine upper wheels are far too generalized (if not even erroneous) to be helpful in deciding if a wide upper wheel would be of benefit for a given operation. So, although many analogies can be very helpful, it is best to avoid motor vehicle tire versus wheeling machine analogies as much as possible given their unrealistic nature... even when their axioms are true and stated correctly.

Upper Wheel Width and Stretching

Probably the most commonly suggested advantage of wider upper wheels is the idea that they provide more stability for a large, wide, low-crown panel such as a roof panel or large door skin while it is being wheeled (stretched) into a compound curve. This stability helps keep the panel on true horizontal instead of tipping to one side or the other. This reduces the likelihood of the edges of the upper wheel creasing the panel.

Upper wheel 'creasing' damage is a sharp, linear marring caused by the edge of the upper wheel. Prior to experiencing this firsthand it may be difficult to comprehend what is being said, especially with respect to an already highly crowned panel. When a panel is allowed to pivot on the lower wheel and fall downward on one side, the opposite side of the panel will be forced upward and into the edge of the upper wheel if the upper wheel is too narrow to prevent this from occurring. In the case of a wide wheel, the edge of the wheel protrudes beyond the zone into which the surface of a high-crown panel can be accidentally or intentionally maneuvered with enough force to cause damage.

Increased stability for wide, low-crown panels is especially advantageous in a one-man operation as opposed a two person team effort. However, in working this type of panel, if the operator or team is experienced, cautious, and conscientious, work done using a narrow upper wheel can be every bit as good in quality as work done with a wide upper wheel. Particularly with a two man team it is possible to carefully work the panel without tipping it into the upper wheel edges even when a narrow upper wheel is used. Since in these wide, low crown circumstances the narrow wheel can be made to work just as well as the wide wheel, some make the assumption that in all other circumstances as well, radiused wheel edges, care, skill and/or experience can, in combination with a narrow wheel, match the performance provided by a wide upper wheel. This opinion is often expanded to the point of suggesting that wide wheels are only a 'crutch' for use by the unskilled, unknowledgeable worker. This is emphatically not the case and this thinking can serve to deter one from ever leaving the security of the 'one size fits all' mind-set.

Relative to some other panels, roof panel/door skin type large low-crown panels are somewhat simple in their requirements. In comparison to some other panels they're also more productively worked by a two-man team since the required motions are linear and predictable. Little or no verbal communication or anticipation between the workers is needed. Contrast that scenario with say, wheeling a 36-inch x 54-inch x 18 gauge sheet into a fender having very high-crown areas possibly blending into reverse-crown areas, wheel openings, and any number of other complications. In this instance a two-man team can sometimes be counter-productive. Each movement requires multiple split second decisions and judgments as to what the panel needs. The team leader may not be able to verbalize fast enough to relay to the second man what it is he would like to do second-by-second. While on first impression it may seem that a wide, low crown panel would be more likely than high-crown panels to get into the upper wheel edges and thereby see creasing damage, this just isn't the case. Panel width, of and by itself, does not lead to creasing. Experience level has little to do with the problem. It is rather a matter of how awkward and unbalanced the panel is and some of the most awkward panels of all are not inordinately wide by comparison. Maintaining large, heavy, awkward, high-crown panels precisely in optimum position against the bottom of an upper wheel at all times is next to impossible. When working such a panel, if the upper wheel is not wide enough for the task at hand no amount of wheel edge radius, skill, or experience will completely eliminate the tendency for creasing the workpiece surface. To repeat what was mentioned previously, the problem can be eliminated by increasing the width of the upper wheel beyond that zone into which the panel can protrude. When this is done, the lower wheel relief area/edge radius then becomes the predominant 'limit stop', if you will, for the panel instead of the upper wheel's edge radius.

Having the lower wheel relief area and/or edge radius act as limit stop is not a problem-free, ultimate solution though since this can serve to cause unwanted bulges and irregularities also. This situation of unwanted panel motion and resulting unwanted shaping via lower wheel is more controllable than an upper wheel edge radius creasing problem however, and, these lower wheel induced irregularities are at least in the direction of desired shaping. Meaning, they are in the same direction as the developing crown instead of the opposite direction as is upper wheel creasing. Some even use this bulging constructively by leveraging against the lower wheel intentionally in order to help form either simple or compound curve contours. It can become a compromised effort however, since, whenever the panel itself is used as a lever against the lower wheel, an opposite force is applied to the upper wheel by the panel. This then can become a situation of the upper wheel immediately undoing, or, depending on direction of panel travel,  pre-undoing, if you will, what the lower wheel does except in the cases of either a non-compound simple curve or a compound curve in a very localized area. The latter of these exceptions is of course precisely how unwanted bulging occurs. A slight offsetting factor here is that the upper wheel is of greater surface area than the lower wheel and therefore potentially distributes the above mentioned opposite force over a greater area thereby allowing some net gain of forming to occur. There exists a very interesting way to 'cheat' and to have our cake and eat it too with lower wheel induced stretching but other explanations will have to come first and this particular method does favor if not require a very wide upper wheel.

Incidentally, if upper wheel induced creasing is occurring, more often than not merely radiusing the edges of the upper wheel will not entirely solve the problem. When working large, awkward panels, the creasing may well become more 'linear depression' and less 'sharply defined crease' if upper wheel edge radius is increased, but it will still be present. Radiused wheel edges are certainly helpful on even narrow upper wheels-- just not as helpful as on lower wheels. It could be argued that reasonably radiused edges are mandatory on upper wheels other than for specialty wheels that for any reason require a square (or nearly square) edge. For example, a much sharper wheel edge radius would be helpful in instances of attempting to work into the inside corner of a flanged edge.

Upper Wheel Width and Planishing

A second creasing scenario occurs when a wheeling machine is used to planish rough-in work. This rough-in work could be tucks, mallet and shot bag work or any shaping which leaves the 'bag-of-walnuts'. The narrow upper wheel will be more apt to 'plow through' localized highs whereas the wider upper wheel will be more likely to ride over the top of localized highs. In this circumstance the narrow wheel will be more likely to leave creases than the wide wheel.

In a planishing operation the wide upper wheel offers some additional but admittedly minor advantage over and above the reduced likelihood of creasing. When using the wheeling machine to planish rough-in of a compound curve, some degree of compound curve is lost, i.e. the e-wheel planishing undoes some of the existing compound curve, particularly in the direction of travel. This is because the planishing amounts to an 'averaging' of the highs and lows present from the mallet work. If the upper wheel is narrow and thereby in contact with less panel surface, more of the high is pushed down and less of the low is brought up than is the case with a wider wheel (in contact with more panel surface). Hence, with a wider wheel less of the desired curve is 'lost' in each planishing session although the tendency to lose curve is still present. It should be assumed that this observation is referring to instances of planishing only, i.e. using reduced force levels between the wheels. That is to say when planishing and stretching are not necessarily being attempted simultaneously. If stretching (high wheeling forces) is simultaneously involved, curve may well be increased with each planishing session.

It is sometimes assumed that one advantage in using a wide wheel in a planishing situation is that less effort is required for negotiating over the irregularities in the panel. The complication in this is that the (small diameter) lower wheel is simultaneously being forced head-on through surface irregularities. This means that if the wide upper wheel is riding higher on the panel because its greater surface area spans more of the irregularities instead of plowing through them-- it must follow that the lower wheel is bringing up those areas it does hit more than would be the case with a narrow upper wheel riding farther down in the panel irregularities because of its smaller surface area. When a wide upper wheel is used on a bag-of-walnuts surface, the lower wheel is being forced to do more work with each pass than would be the case with a narrow upper wheel. This means that the level of human effort per pass created by the lower wheel is greater when a wide upper wheel rather than a narrow upper wheel is used. However if a narrow upper wheel is being used, greater effort may be required to force it to plow through rather than ride over irregularities. It would appear to be 'a wash' or close to being one.

The author's experience is that as far as a comparison of how much effort is required in either scenario, this is indeed a 'wash'. Effort is about the same in either instance but some conclusions can be drawn:

Claims that a wide upper wheel leads to less effort while wheeling a panel are at times based only on the completely erroneous off-road tire analogy and its attendant overlooking of the wheeling machine lower wheel always being part of the equation. This instead of conclusions being reached through real-world first-hand comparisons of different upper wheel widths.

The overall level of effort required is usually masked by the stop/go, bumpy ride nature of using a wheeling machine when planishing a rough surface.

The smoothness and stability afforded by wider and/or larger diameter wheels is more noticeable than any differences in effort required.

Regardless of smoothness, stability or effort involved, the goal is to force the lower wheel to do work. If the wider upper wheel rides higher on the panel because it spans more irregularities, the lower wheel is doing more shaping/forming in the direction desired. More of the worker's effort is going towards forming curve in the desired direction.

If the upper wheel is 'plowing through' by virtue of being narrower, it is doing shaping/forming in the direction not desired, i.e. it is undoing some of what was gained in mallet work, undoing some of the desired curve and wasting worker effort in the process. In this circumstance the lower wheel is doing less work in the desired direction compared to the same lower wheel used in a wide upper wheel set-up. Therefore less of the worker's effort is going towards producing curve in the desired direction. More of the worker's effort is lost to the upper wheel's tendency to undo some of the curve formed by mallet work.

Real Numbers - Diameter

A large diameter upper wheel --large, that is, relative to the size of the mallet lumps in a panel-- causes the panel being worked to move more smoothly and consistently through the wheels than does a very small diameter wheel. A larger diameter upper wheel does not follow the panel's irregularities as closely as a smaller diameter upper wheel. To some degree it spans over the irregularities just like the tall-tired lawn & garden cart. So, strictly from a smoothness of performance standpoint, in the case of upper wheel diameter, bigger is better. However other factors enter the picture as upper wheel diameter increases.

This 'bigger is better for smoothness of performance' holds true for lower wheels as well, but of course the lower wheel must be small enough and of severe enough radius to clear the panel shape desired. The 'bigger is better' rule of smoothness cannot be applied to the lower wheel beyond the size of the panel's crown radius.)

Upper wheels larger than 8.0 inches in diameter result in rapidly diminishing net gains in performance. Increases in weight, inertia effect, framework design limitations, availability and expense occur, making diameters over 10.0 inches less common and diameters over 12.0 inches very uncommon. This increasing weight, inertia effect and expense combined with diminishing performance increases mean extremely large wheels are seldom used except in heavy duty applications. At the other end of the scale, upper wheels smaller than 6.0 inches are just that --too small-- relative to the obstructions involved and the stability desired. Again, scale of operation is a consideration. In building very small parts for pedal cars, model cars, and similar tasks a 6.0 inch wheel might be considered gigantic.

All of these points bring to light an interesting concept. There are practical design limits to upper wheel diameter compared to what would be theoretically preferred, i.e. bigger is better --but-- making the wheel wider can offset some of the disadvantage incurred by the diameter being smaller by necessity of design. In fact, especially with respect to panel support, increases in width of the upper wheel up to the point wherein it would be impossible for the panel to regularly contact any additional width, provide much greater real-world advantage than increases in diameter. This is because increasing the diameter of the upper wheel increases the effective area for panel guidance or for spanning irregularities (not to be confused with wheel-to-wheel contact zone) only slightly. Increasing the width of the wheel dramatically increases the 'guidance' area and the 'spanning' area. Although, for any given operation, once the required wheel width is attained, greater width will provide little further advantage. Another dramatic case of diminishing returns.

Guidance area, for lack of a better term, is that area of the upper wheel which the operator relies on for guiding the panel through the wheels. To make this more clear, visualize how very difficult it would be to guide a large or awkward panel through the wheels if the upper wheel was only 1/2 inch wide. Avoiding crease lines would be impossible. In fact the 1/2 inch wide wheel would not be far removed from 'V' wheels in either e-wheels or bead rollers that are used to deliberately crease or groove a panel. Any claim that an upper wheel for use in forming compound curves need be no wider than the wheel-to-wheel contact zone is erroneous, assuming one does not want a panel covered by creasing damage.

Incidentally, certain aspects of an infinitely large diameter upper wheel can be approximated by using a flat plate under the upper wheel. This subject will be covered in a future article.

Real Numbers - Width

For some of the operations performed when working large panels, a very wide wheel is all but mandatory. In these instances a 2.0 inch wheel is unsatisfactory. For progressively larger and more awkward panels, progressively wider wheels provide better results. A wheel of 4.0 inch width in these cases often will show better performance than the common 3.0 inch wheel. A 5.0 inch width wheel is far superior to the 3.0 inch wheel when working truly tough-to-handle panels. In testing different widths, the author has not seen much advantage in a width greater than 5.5 or 5.75 inches. It must be pointed out again that these performance results are relative to typical, large, high crown automotive panels such as fenders. These are the most difficult automotive panels to make in large sections. Low crown panels or smaller high crown panels that are much more controllable can certainly be successfully worked with narrower upper wheels.

So the bottom line is... if the upper wheel is causing creasing damage it can be eliminated by a) dividing the problem panel up into smaller and therefore easier-to-control sections or b) utilizing a wider upper wheel.

Extra Wide Upper Wheel

Moving on to some pictures of upper and lower wheel systems, note that an underlying theme is that building adjustability into both upper and lower systems allows individual wheels to do more tasks well, thereby hopefully reducing the total number of specialty wheels and brackets required.

To begin here is a picture of an inexpensive wheel set.

The narrow 8.0" D x 2.0" W upper wheel in this picture is often used when working small parts such as patch panels, or, very long narrow parts such as valance panels, or, localized, small areas of certain larger parts. An upper wheel such as this works well with small, lightweight parts because it has a low rotating inertia given its weight of only 8.5 pounds. It is easily and quickly started, stopped or reversed. If the wheel's edges are reasonably radiused, accidental crease marks are seldom a problem when working smaller panels. The chance of catching a thumb or finger between the wheels, which is no minor thing when it occurs, is reduced compared to chance of the same when using a wider upper wheel while working a very small panel. A final advantage is that this size wheel with bearings can be purchased new retail for very little money.

The lower wheel shown has fairly sharp, non-radiused edges. The reason being... when the picture was taken, this was a newly made wheel and no decision had not been made as to how much edge material to remove. This is mentioned in order to convey the concept that lower wheels are very frequently altered. They are all a work in progress subject to modification. Using the axle/bearing design described below, the lower wheels can be very rapidly knocked apart and reassembled repeatedly with no damage to the bearings. Quite literally in thirty seconds the wheel can be disassembled, installed on the arbor shaft and in the lathe. See the bearing/axle description below for details.

A potential problem with very wide upper wheels is their expense, weight and rotating inertia. There are ways to avoid this if desired. Much of the interior of a wheel machined from solid stock can be removed with no negative impact on its use as an upper wheel. 

The wheel below started life as an 8.0" D x 3.0" W cast wheel with roller bearing. This wheel weighed 12 pounds before any machine work. New retail cost is less than $40.00. Forged wheels or cast wheels wider and/or larger in diameter than this are much heavier and more expensive. Typically a 'cheap' four inch wide wheel will cost $100.00 or more and can weigh over forty pounds. Such wheels are designed for very heavy loads on concrete floors and similar applications. As such they are far stouter and possess stronger bearings than required for the comparatively light-duty task of rolling sheetmetal. Specific heavy duty applications would be an exception of course. Factors such as these should be considered if ease of use is one of the main attributes desired in a wheeling machine.

This wheel was modified as follows.

The roller bearing assembly was removed. The bore was resized for precision sealed ball bearings. Precision, sealed cylindrical roller bearings or even low-friction bushings can be used if greater load rating is desired.

The radiused edges of the wheel were removed to obtain very square, sharp edges. A recess was cut in the ID of this new outer edge. The outer circumference of the wheel was left as-is.

Aluminum plates were made with mating lip to fit in this recess. These plates mate to either side of the wheel.

Secondary plates, or any number of plates actually (to permit adjusting to any desired width), then attach to the first plates.

Smaller diameter aluminum hubs, again located by recess/lip machine work bolt to the secondary plates.

The aluminum plates and hubs are assembled with machine screws.

The hubs in turn locate nylon plates which act as outer radius edges to protect the sheetmetal surface being worked. These particular nylon plates have a radius of about 3/8 inch.

Note that the various hubs, lips and recesses serve to positively engage the many components together into a 'non-slip' assembly. A great deal of force can be applied (and in testing has been applied), even at the very outer edges of the wheel, with no ill effects.

White nylon is an extremely difficult material to photograph. A dark background was required in order to show the contours of the part. The interface between black and white on a circular or oval contour is sometimes not rendered very well in every web browser. Jaggies may appear around the perimeter of the object. This is a digital imaging condition not irregular machine work of the actual part.

Mounting hardware includes an adapter plate, yoke, and finally, a shaft, spacers and clamps.

Assembled wheel views.

Through-bolts running between the wheel's spokes retain the entire finished assembly, positively locking the recess/lip joints. The bolt style and pattern used on the hub may look random but does make sense after studying what is going on.

The result of all this work is an adjustable width wheel with no-mar edges weighing little more than a light three-inch wide wheel.

The most basic reason for doing this was to permit first-hand investigation of the performance of various wheel widths-- without having to actually make multiple wheels or multiple nylon side plates. By simply adding or subtracting aluminum plates, different wheel widths could be experimented with on real-world panels using actual work techniques. Thus, the wheel width comments in this article are based on real-world experience with numerous specific widths instead of being mere conjecture from someone who has never even used those wheel widths.

While anyone with access to a lathe and drill press would certainly be able to fabricate the parts for himself, this design would likely be considered by most to be prohibitively expensive if the machine work had to be hired out. On the other hand, the aluminum plates are not needed if one does not intend to perform detailed research on the effect of multiple wheel widths. Simply adding nylon (or other type of plastic) side plates of the desired width to an existing narrow wheel is a very inexpensive way to have a wide wheel. In this way those on a budget can avoid the need to purchase a very expensive chunk of large diameter alloy steel to make a hardened wide wheel. Plastic is cheap relative to the cost of 1045, 4140, etc.

Specialty Lower Wheel Device

The pictures that follow illustrate a lower wheel bracket that has been used quite successfully for some time, typically in conjunction with a narrow upper wheel.  Its main purpose is to provide a means to wheel a panel area adjacent to a flange, corner or any similar sort of restriction. While 'single shear' style mounting of lower wheels is not completely uncommon in lower wheel hardware, this bracket is far more than that. Most adjustable lower wheel brackets are adjustable for purposes of aligning the lower wheel to the upper wheel but this bracket is designed for purposely misaligning the wheels!

Usually, a selection of specially shaped wheels is needed to fully work the area adjacent to and even into a flange. This pivot mechanism, however, allows 'walking' the contact area from one side of this lower wheel to the other. Thus the contact area can be positioned anywhere from a good distance away from the panel's flange right up to the flange. The result is that just one asymmetrical wheel is able to accomplish what would otherwise require several different wheel contours.

As an aside, the components of this bracket are finished with the phosphoric acid/zinc phosphate/paste wax system the author has used with good results for many years. Admittedly these photos were taken right after application of this finish but it does indeed have very good durability, is very quickly applied with common, locally available supplies, is very easily renewed if worn away, does not interfere with machined tolerances or component interaction as paint often does, and is rust resistant. Aside from its performance, many prefer its appearance to that of paint on small machined parts.

The bracket can not only be pivoted a slight amount to achieve action right up to a flanged corner-- it can also be pivoted to an extreme angle of twenty, thirty, forty or whatever number of degrees required so as to actually wheel up into a radiused flange corner. This is helpful when smoothing existing flanges such as are found on '40's era rear fenders wherein a large radius flange corner wraps around the bottom curve of the fender.

When using these larger angles of operation, axial loads are being placed on the bearings. Expensive angular contact or deep groove bearings better able to handle the side loading were not used. Standard radial ball bearings have survived. This can possibly be attributed to a fortunate coincidence. As it turns out, in actual use the more extreme the angle used, the smaller the contact area... and therefore... the more likely a lighter setting is used on the e-wheel's force adjustment mechanism. Secondly, the rigidity of the larger-than-standard axle insures that the bearings are seeing radial and axial loads but very little if any angular misalignment. (For more on axles and bearings, see below.) 

In operation the mechanism is never pivoted to the 100 or so degrees seen in this picture though! This was done merely to photograph the assembly.

The adjustable slotted base allows aligning the lower wheel contact area to the center of the upper wheel even when the lower wheel is pivoted. The slotted adjustment also allows the narrow lower wheel to be positioned far off-center relative to the upper wheel so as to allow wheeling up close to a flange no matter whether the flange faces up or down. This lateral adjustment could be achieved with a more elaborate sliding mechanism or dovetail but the goals for this device were to retain simplicity and to be able to bolt it to any standard wheeling machine's lower yoke mounting plate.

This wheel does not have a flat work surface. In the picture below, the top of the wheel appears to be flat but this is caused by camera angle and lighting. The bottom of the wheel provides a more realistic view of the contact surface but it is exaggerated by the lighting shadow. A straightedge laid across the surface reveals that it is not quite flat, having a very slight radius for the purpose of precise placement of a contact area as described above.

Standard Lower Wheels

Here are some pictures of a standard lower wheel design (3 inch x 3 inch of 4140).

It is important to remember that the axle/bearings combination in a lower wheel are the weakest link in a wheeling machine as far as maximum force the system can exert. When working anything other than very soft material, some of the more inexpensive utility-grade sealed ball bearings that are physically small enough to be used in a lower wheel that has a good deal of edge relief are operating in an environment that might exceed their rated load capacity. On the other hand many high-quality bearings of the same size have a much higher load capacity.

Since wheels on a wheeling machine never see RPM of any consequence at all compared to motors, gearboxes and the like, a common assumption is they (the bearings that is) do not see as much wear as they would in say 1000 or 2000 RPM applications. While it is true that precision sealed ball bearings do have RPM limits while under load, this is not their Achilles' heel. Extreme loading under low-RPM or no-RPM is their real enemy to achieving a normal life-expectancy. Notice that in a detailed spec sheet of a quality bearing manufacturer's ratings, the bearing is rated in both static load and dynamic load maximums. The static load limit is usually dramatically lower than the dynamic load limit. When selecting bearings for a wheeling machine the static load limits, not the dynamic load limits, should be considered. Static loads or extremely low-RPM loads such as found in a wheeling machine are tough on ball bearings.

Because some lower bearings can be in danger of being overloaded, it only makes sense to insure that they are at least correctly loaded. In many instances this is not exclusively a bearing problem. It is the axle/bearing combination which is the weak link. If an axle is not amply rigid under load it will apply angular misalignment loads to the bearings thereby reducing their life expectancy. Don't confuse rigidity of the axle with strength of the axle and don't confuse true shear loads with bending loads imparted to the unsupported axle center section. It is usually difficult to ascertain whether this is a serious problem in a given system but if the axle is a small OD straight shaft and the machine sees high loads it is possibly a contributing factor if bearing wear is a problem. While either deep-groove bearings or double-row angular contact bearings can be purchased, keep in mind these types of bearings are more expensive, and, they do not actually run at misalignment angles like a spherical bearing. They merely are better able to handle loads in non-radial directions than are standard ball bearings. However, if the axle is deflecting, such bearings may not be invincible. For even more money though, self-aligning ball bearings can be purchased. This type of bearing does permit angular misalignment of axle and wheel. 'Trick' bearings sometimes come at a cost additional to the economic cost. Depending on design, such bearings can have lower radial static load limits, the very thing most needed for use in a wheeling machine. A better solution is to do away with most axle flex up front. This can be accomplished by using a stepped axle as shown.

This axle is made from 0.875 inch OD 4140 shaft although everyday CR would work well also. Aside from strength issues, using 4130 or 4140 when make such small parts may be preferable because it machines and finishes nicely, is a little more resistant to marring and can always be hardened for additional resistance to surface damage. The bearing ID and the axle step for the bearing is 0.625 inch. ( 0.500 inch ID bearings are not used.) Finally the axle's yoke mount step is 0.500 inch to maximize clearance for the panel being worked and allow the wheel to be used in many wheeling machines without changing yokes.

Even aside from performance issues this axle configuration is a good choice. The step on the axle for the bearing ID can be polished to a desired fit in the bearing instead of being a loose fit such as obtained by off-the-shelf 1/2 inch shaft in a 1/2 inch ID bearing. This bearing step and the larger OD center section of the axle retains the axle precisely centered side-to-side in the wheel. With careful machining of the ID of the hole in the wheel for the bearing's OD, it is entirely possible with this design to end up with an assembly that can be knocked together and back apart with a dead blow hammer instead of resorting to a press. At the same time, the bearings will stay seated in the wheel, the axle will stay centered and the axle will not spin in the bearing race (instead of turning the bearing), all without fasteners, retainers, or Locktite. Also, and perhaps most importantly, the large OD center portion of the axle acts as a drift for disassembly without risk of bearing damage. Striking one end of the axle with the dead blow hammer while holding the wheel in the other hand serves to drive the opposite bearing out of the wheel. Once that bearing is driven out, the axle can be struck with the dead blow from the other end to drive the remaining bearing out. Using a large dead blow hammer in this manner applies a good amount of 'push' to the bearing outer housing without transferring a great amount of potentially damaging impact loading to the sides of the bearing balls and races. To reassemble, two short lengths of tubing or appropriately machined cup-shaped drivers matching the diameter of the outer bearing shells are used. One bearing is driven into the wheel. One of the drivers or tubes is placed on the worktable table. The wheel, with the end with the inserted bearing facing down, is placed on the tube. The axle is inserted. The second bearing is placed in its bore with the axle's end protruding through the bearing ID. The second length of tubing is placed on the bearing and struck with the dead blow hammer to drive the bearing home.

Bearing failure would be very unlikely using the above guidelines, but, again, this applies to typical automotive panel work instead of specialty heavy duty applications. For extreme heavy duty applications, precision sealed roller bearings with integral inner race provide more load capacity than a ball bearing and yet offer better performance than full-width non-precision roller bearings designed to run directly on a shaft with no inner race.

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