The first John Miller patent to address the issue of wheel and track structure is US # 979982 "Railway car for pleasure railways" filed 4/1910 and issued 12/1910. This was evidently invented while John Miller was working for Frederick Ingersoll, as the witnesses listed are Ingersoll and Charles L. Alexander.
The patent shows a side friction car having guide wheels directly over the flanged road wheels. Several quotations from the patent indicate that this arrangement is designed to reduce the chances of derailment:
"It is essential to provide some auxiliary means to prevent the traction wheels from leaving the tracks, especially at the curves."
"The flanges of the traction wheels tend normally to keep said wheels to the track but the swaying and vibrations of high speed of travel are such that there is a constant tendency of said flanges to climb off the rail."
"The present invention has for its object the provision of simple and improved means to aid in resisting the end thrust of the car axles, whereby the tendency of the wheels to climb off the rail is prevented."
The next Miller patent addressing this issue is US # 1038174 "Pleasure railway structure" filed 11/1911 and issued 9/1912 (shown in Panel 1 of the illustration below).
This arrangement simplifies track construction considerably, as described in the patent:
This arrangement was presumably standard on John Miller's coasters for several years, since no other patents address this issue until 1919.
Illustrations modified from patents 1038174 (1), 1319888 (2), and 1373754 (3). Continuous wooden rail structures are shown in brown. Metal rail plates are shown in red. Road wheels are shown in blue. Guide and upstop wheels are shown in green.
Patent US # 1319888 "Pleasure railway structure" filed 7/1919 and issued 10/1919 shows the still-standard arrangement used on wooden coasters, with road wheels, guide wheels, and upstop rollers all engaging the same wooden rail structure (Panel 2).
This patent could be considered the invention of airtime on roller coasters:
It should be noted that the track structure itself is not quite the same as that used on existing wooden roller coasters. The main structural support is a separate sleeper beam connected by crossties to the rails upon which the wheels run. A more modern track structure used in combination with the three-wheel arrangement is illustrated in US # 1613118 "Pleasure railway structure" filed 5/1925 and granted 1/1927 (see Panel 8 below).
A subsequent patent US # 1373754 "Pleasure railway structure" filed 11/1920 and issued 4/1921 appears at first glance to represent a regression, since it uses upstop wheels engaging a separate structure (Panel 3). However, it turns out that this patent is for retrofits to older equipment employing the 1912 patent. The track structure is identical to that of the older patent (Panel 1), except that the sleepers now become guard beams engaging the upstop rollers.
I doubt that this structure was used by John Miller for the following reasons: First, although this conversion would have been less expensive than rebuilding the entire track structure, it would only work if the sleeper beams were of the correct height and position to function as guard beams. Second, coasters built using the older track structure would have been designed without deep dips that required upstops. If they were re-profiled to incorporate deep dips, the entire track structure would have been rebuilt anyway. When the track was rebuilt, it would have been simpler to switch to the standard three-wheel configuration.
I suspect that the main function of this patent was to prevent others from using this sort of arrangement as a way to evade the claims of Miller's 1919 patent.
An attempt at simplification is shown in patent US # 1415187 "Pleasure railway structure" filed 11/1920 and issued 5/1922 (not shown here). This illustrates flanged wheels running on a rail with a C-shaped structure, either wooden or metal, such that the road wheel serves also as its own upstop wheel.
A significant simplification and variation on the 1919 patent is shown in US # 1448763 "Pleasure-railway structure" filed 12/1922 and issued 3/1923 (Panels 4 and 5). In this patent, the guide wheels function also as upstops by engaging either an overhanging portion of the rail (Panel 4) or an angle iron attached to the rail (Panel 5).
Illustrations modified from patents 1448763 (4, 5) and 1501060 (6). Color code as described above.
A further variation is found in patent US # 1501060 "Pleasure railway structure" filed 2/1924 and issued 7/1924 (Panel 6). This patent uses a Z-shaped rail as the running surface for both the road wheels and guide wheels. As in the previous patent, the guide wheels also function as upstops.
In patent US # 1501061 "Pleasure railway construction" filed 2/1924 and issued 7/1924, an I-beam rail is mounted on top of a resilient wooden structure (not illustrated here). The guide wheel is in the channel between the upper and lower portions of the I. This structure seems to me to combine the worst features of both wooden and steel rails. The patent appears to make the assumption that the flexibility and resilience of the wooden part of the rail structure is necessary to its proper function, an assumption that clearly does not apply to modern coasters having rigid steel tracks.
Patent US #1536122 "Pleasure railway structure" filed 11/1924 and issued 5/1925 (Panel 7) continues the use of guide wheels as upstops, but now uses a metal T-bar mounted on the edge of the wooden rail structure. This structure is also illustrated in US # 1827162 "Brake structure" filed in 5/1928 and issued 10/1931. A minor variation is found in US # 1562036 "Pleasure-railway structure" filed 5/1925 and issued 11/1925. This is identical to the arrangment shown in Panel 7, except that an overhanging steel flat plate replaces the top of the 'T' to serve as the surface for the running wheel and to limit the vertical motion of the guide wheel. The lateral surface for the guide wheel is protected with an angle iron. The horizontal portion of the angle iron in this arrangement appears to serve no function.
The later patent US # 1605369 "Truck for pleasure railway cars" filed 11/1925 and issued 11/1926 (not illustrated here) shows an oddly flanged wheel running on a wooden rail topped with an overhanging steel plate. The plate functions as the running surface and also engages an upstop bar.
Patent US # 1629520 "Pleasure railway structure" issued 5/1927 has flanged wheels and outboard upstop rollers engaging an extension on the rail (not illustrated here).
Illustrations modified from patents 1536122 (7), 1613118 (8), and 1825468 (9). Color key as above.
Miller's 1927 patent US # 1613118 illustrates the standard three-wheel arrangement in the context of a standard laminated track structure. (The depiction in this patent is incidental to the improvements claimed.)
Patent US # 1825468 "Pleasure railway structure" filed 5/1929 and issued 9/1931 appears to be another attempt at simplifying the track structure (Panel 9). An angle iron attached to the inner surface of the wooden rail structure provides the running surface for the guide wheel. There is no upstop wheel, but an upstop bar engages the projecting part of the angle iron.
Other roller coaster builders were also inventing improvements in track structures.
The Frederick Church patent US # 1410374 "Roller coaster railway" filed 8/1921 and issued 3/1922 uses a subtrack made of laminated boards, a layer of cross ties, and upper track layers composed either of laminations (Panel 10, used on curves) or boards (Panel 11, used on straight track). The track is built for flanged wheels, with an upstop bar below the overhang in the track (Panel 11).
Illustrations modified from patents 1410374 (10, 11), 1741286 (12), and 1755030 (13). Color key as above.
An improvement patented by Church, patent US # 1741286 "Laminated construction for roller coaster tracks" filed 5/1925 and issued 12/1929 uses multiple layers of square stock for laminations in the track layers (Panel 12). The square stock allows bending in both lateral and vertical planes. The upper layers are still boards, since they must function as upstops.
In the Herbert Schmeck patent US # 1755030 "Track construction" filed 3/1927 and issued 4/1930, the track incorporates upper and lower laminations of rectangular stock, with overhanging solid boards in the middle layers (Panel 13). The wheel arrangement illustrated has road wheels and guide wheels above the flange, and an upstop bar below the overhang.
The patent illustrations from the Church and Schmeck patents suggest that other coaster makers attempted to avoid making use of John Miller's patents whenever possible. Miller's 1919 patent would not have expired until 1936. I am not sure on what terms Miller licensed his patents to other builders. It is not clear to what extent he profited directly by licensing his inventions, and to what extent he denied others the use his inventions as a way of retaining more coaster designing and building business for himself.
An interesting question is how coaster tracks on existing coasters were modified over time as new technology was developed or as patents expired. Some of the tracks with overhanging laminations in the middle might have been adapted to work with upstop rollers. However, it seems clear that those rollers would have to be positioned much lower in relation to the car than for the more conventional track with the overhang at the top.