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||A History Of The Early Tire|
Since there seems to be no extant compilation of the thought processes, constructions and rubber compounding that went into what became the pneumatic tire, perhaps it behooves that one be attempted. This may be especially relevant since we who have sufficient age to attempt such a recapitulation are becoming few in number.
It is probable that solid rubber tires had been placed in operation for some select needs.
It is also possible that the use of reinforced rubber hoses had been explored.
But one, John Dunlop, is given credit for having produced the first pneumatic tyre (tire) for use on his daughter's tricycle. This was to provide better shock absorption and a smoother ride.
We are left to surmise about what he may have produced, and especially the techniques used to accomplish this.
One clue about the early tire still exists with the Ford Quadricycle. This first Ford automobile remains in existence, and since Ford still wishes to maintain the option of operating this machine, there has been an on-going demand to replicate its tires. Those tires utilize what was once called "Singletubed" construction. That term refers to the fact that the inner tube is integral within the tire, there are no beads, the cross-section is circular, and the downward component of the inflation pressure produces sufficient grip on the circularly shaped rim to resist circumferential slippage. Recent productions of those tires have utilized the bias principle. Since bias tires only became available near the start of World War 1(1914), the original tires would have been of the square woven cloth type.
Since Mr. Dunlop has also been credited (by some) with having introduced the first radial tire, we can add some confidence to these speculations. [It would seem logical for Mr. Dunlop to have experimented with processes for restraining circumferential growth in his products.]
The cloth-reinforced single tube tire would have had limitations to its life. The inherent "sawing" actions of interlaced cords during repeated deflections would have led to ruptures in the cloth, and blow-outs of the inner tubes. Since there would have been no practical way to repair the inner tube, costs to the users would have been high.
We speculate that the next iteration would have involved separating the inner tube from the tire. This would have led to the need for an improved grip of the tire to its rim. This had its form in the "clincher" concept. "Clinchers" had a hook shaped flanges on the each side of their rims. The hooks faced inward. The cloth tires had mating slots on the outward facing surfaces of their lower sidewalls. These regions were reinforced with cloth and stiffer rubber compounds. The clincher type could suffer from accidental dismounts and over-pressurization blow-offs. They continued to suffer the ill effects of the cloth structure problems, but tube maintenance could be successfully carried out. Clincher tires benefitted from the move to the bias concept in so far as carcass life was concerned, but continued to have the rim to tire interface weaknesses.
The "straight sided tire" with a bead wire reinforced lower sidewall was the next advancement.
Tires had continued to be constructed on cores that mirrored the inflated tire inner surface.
The adoption of the flat drum concept, which produced a cylindrical structure that required it be pneumatically changed, then maintained in a torus-like condition, before and while being placed in its curing mold, substantially ended the era of the early tire.
Some years ago, the president of a large "off the road" machinery maker requested at least 2 large tire makers to prototype for him a special tire-making process. The process would yield a radial tire carcass that could be ultimately inflated into an already cured belt/tread package. The outward pressure of the carcass would provide the necessary force, along with the friction of the two rubber surfaces to maintain alignment and avoid slippage. This would insure an easy way to "retread" a worn casing-it could be done in the field on a job site. The machinery maker would eventually be producing these components himself.
Both tire makers utterly failed in their efforts to produce a prototype tire carcass.
Both tire makers had forgotten their pasts.
What had been requested was a re-visitation of the "original" tire making process.
To produce the inflatable carcass, the following steps would have needed to be taken:
Based on the finished tires dimensions, a strip of sheet metal of appropriate length would be rolled into a hoop, and butt-welded to form a ring. A slot that was appropriate for the diameter of the inflation valve would be cut from one edge of the ring extending toward the centerline. The ring would need to be supported from beneath, and capable of being rotated, even if by hand.
A specification would need to have been calculated, based upon the mold dimensions, to predict the thickness, lengths and widths of inner tube compound, and radial fabric.
Construction would be as follows: (The materials are off-set from the centerline of the cylinder) [specification will specify amount of off-set]
Encircle the cylinder with the radial ply material and splice the ends together.
Encircle the center of the ply material with the calendered inner tube compound.
Dust the top surface of the tube compound with soapstone -exempting the extreme edges and ends.
At a point in line with the slot in the ring, position the tube valve, and cement its upward facing base area.
Lift one edge of the tube material and fold it toward the center toward the vertically extending valve stem. Slit the rubber to allow it to incorporate the valve. Continue the process until one entire edge has been folded. The opposite edge is then folded toward the previously folded edge, and a circumferential splice is to be accomplished. The valve area will need to be treated as was done in the first step. The ends spliced accordingly.
The fabric is now folded over the tube to accomplish the same result-that is circumferential splice on the outer surface-tube valve stem projecting through the spliced fabric.
The next step involves rolling the tube/fabric body to an inverted position. In line with the slot in the "drum/ring" rotate the structure so as to let the valve enter the slot. Continue the process until the entire composite is completely upside down from the way it was built.
Slide the unit off the ring, allowing the downward pointing valve to track through the slot.
The periphery of the structure will have been calculated to conform to the mold that is to be used.
The mold will not require a bladder, but will require an air hose to provide pressure for the innertube.
Pressure is applied to form the carcass as the mold is closed, and curing occurs.
The cured inflated product will maintain a constant circular diameter while exerting outward and downward pressures toward constraining surfaces.
Sometimes it is better to review history, than to try re-inventing the wheel.