Much preliminary work was accomplished between 1932-35 at Sacaton, Arizona. The ginning engineers and cotton technologists, in fiscal year, 1936 conducted an intensified series of informative roller ginning tests on. both cleaned and uncleared Pima cottons, during which the roller and crank speeds were varied from 110 to 150 and from 650 to 840 respectively, and other ele- ments were investigated. Cleaner feeders, an MEF (Lummus master extractor feeder), and 3 cylinders of cleaning were employed in combinations.
In general, cleaned cotton and higher roller and crank speeds gave the best overall results.
Four cottons were ginned with each of three crank speeds (650, 930, and 1200 rpm) with each of three 6-inch rollers having different types of roller covering (semi-self-grooving, half walrus and half packing, and spool-wound all-packing) at each of three speeds (100, 125, and 150 rpm) or 27 tests per cotton. Seven and 8-inch spool-wound all-packing rollers were also tested against the 6-inch roller with these cottons at a speed of 125 revolutions per minute and at the same periphery speeds as the 6-inch roller operated at 150 revolutions per minute, or 4 tests per cotton.
The optimum crank speed, as determined in the tests appeared to be between 800 and 900 revolutions per minute, preferably about 900 revolutions per minute if a long life, trouble-proof crank mechanism for high speed could be devised. Further development work involving long time mechanical engineering work was found to be necessaryto achieve practicable high speed crank mechanisms.
As compared to a crank speed of 650 and roller speed of 125 revolutions per minute, the tests showed that a crank speed of 930 and a roller speed of 150 revolutions per minute ginned an average of 34 percent more cotton, or increased ginning capacity 34 percent. Increased roller speed was a• contributor to increased capacity, but the increased crank speed was the main factor. The grade of the cotton was not affected by these increased speeds, and staple lengths was seldom appreciably or significantly influenced as brought out in classifications made at Phoenix, Arizona.
During 1941 new gins in the El Paso area and Pecos Valley of Texas, in the Mesilla Valley of New Mexico, and in the Gila and Salt River Valleys of Arizona operated successfully at crank speed of 800 to 840 revolutions per minute on a 24-hour day basis, and in some instances at 930 revolutions per minute where the ginning volume was small.
The 7-inch and 8-inch laboratory rollers were found in the tests to be at least a third slower in ginning capacity than the conventional 6-inch roller, even when operated at the same speeds, and therefore, proved to be less satisfactory. Grade and staple length of the cotton was not affected by variations in roller size.
Spool - wound all-packing gave slightly better ginning capacity than the semi-self-grooving roller or the half walrus and half-packing roller, but the grade advantages appeared to be barely in favor of the half walrus and half packing roller. The semi-self-grooving roller appeared to produce fewer neps and naps in the cotton than the other rollers.
Along with testing the rubber flap doffer and lint flue devised at the U. S. Cotton Ginning Laboratory, it was proposed to test various methods of overcoming or killing static, the effects of which, if severe, generally prevent the use of the doffers. A jet to place moist air on the cotton on the seed
grid was tried, but it did not function satisfactorily. All other efforts to devise methods of moistening the roller, except steam jets under the roller, were in vain. The series of tests was therefore reduced to 24 tests (6 cottons x 4 tests) or the following:
1. Brush stick for doffing.
2. Rubber flap doffer for doffing.
3. Rubber flap doffer and lint flue.
4. Wooden roller and gin roller and lint flue.
Some very valuable data and observations resulted from these tests. It was found first that the lint flue will work. The present design should be changed however. The piping should be altered to provide adequate air velocity without excessive fan power. When lumps of lint that hang on the knife are finally drawn through by the roller, the air suction at the nozzle is not strong enough to pull the cotton into the lint flue.
Test observations indicated that with a lint flue, the doffer is not necessary because the air pulls the cotton from the roller and straightens out the fibers in a manner comparable to the effect of the mechanical doffer.
A new engineering design of lint flue nozzle with a large adjustable throat to fit partially over a wooden roller riding on the conventional gin roller and partially over the gin roller has been built by the engineers for shipment to Sacaton for testing.
Very little static occurred at Sacaton during the time that the 1941 crop ginning tests were made, and steam lines were, therefore, not hooked up to the gins in an effort to overcome the static; but a number of observations were made and data were collected at commercial gins on the effects of steam devices in controlling static. It was found that steam made it possible for the ginner to use rubber flap doffers which improved the grade from one-third to one-half over the conventional brush stick doffer. The steam also materially increased ginning capacity. The application of steam in its present form has some objections, namely that the steam rusts the gin stand and makes a messy condition with dirt and trash under it.
For this reason some Arizona ginners discontinued the use of steam, although most of the ginners in the El Paso area still employ it as a static eliminator in order to use the doffers and also to obtain as high grade lint as possible. In the El Paso area the ginners aimed to turn out grades as high as. No. Z in order to command good prices. When the grades drop to No. 3, the value of the cotton is generally $25. per bale less than cotton of No. 2 grade. Girmers are therefore making every effort to keep the grades up, and this method of making the use of the doffer possible is one of the severalmeans employed for improving the grade of the cotton.
The tests at Sacaton showed that on 6 cottons, the average grade was 1.7 with the doffer as compared to 2.3 with the brush stick. When the lint flue was used, the grade was aboutthe same as whenthe doffer was used alone. Tests at commercial gins showed that the doffer improved the grade on an average of almost one-half grade on six cottons at one gin and one-third grade at another gin on six other cottons. When steam was used in these tests to make the doffer function better, the ginning capacity was increased 10 percent and the moisture of the lint cotton 1 percent.
There were 56 tests made on cleaning, drying, and conditioning which were completed on 7 cottons and involved the following:
1. No cleaning (control).
2. Once through. Mitchell.
3. Twice through Mitchell.
4. Once through Mitchell with 160 degrees F.
5. Twice through Mitchell with 160 degrees F. and 120 degrees F. respectively.
6. Once through Mitchell with after cleaning cylinders of Lumrnus.
7. Twice through Mitchell with after cleaning cylinders of Lurnmus.
8. Once through Mitchell with moist air.
The result of these tests indicated that when the cotton was passed through a double extractor unit, its grade was improved to an average grade of 1.6 from an average of 2.4 where no cleaning equipment was employed in cleaning the cotton. The cotton on hand was generally too dry to show any further favorable effects of artificial drying. By cleaning the cotton the ginning capacity was increased 12 percent. The average foreign matter content of the cotton was reduced from 2.8 to 0.8 percent by cleaning with a double extractor unit. While the passage of the cotton through two double extractor units and a cylinder cleaner reduced the foreign matter content only 0.2 percent below the average for the cotton after its passage through one double extractor unit, the average grade was improved 0.2 grade.
Tests on the conditioning of cotton in extractor units indicated that it was necessary to clean the cotton thoroughly before conditioning it in such units prior to ginning. When steam was applied to the extractor unit, the staple length of the cotton was increased, but the grade improvements were lessened, and additional tests were made to determine the benefits of conditioning the cotton after cleaning it. The results of these tests are not here reported.
Moisture determinations were made at Sacaton on the seed cotton and ginned lint samples involved in the tests there and in commercial gin tests. Foreign matter determinations were made of the seed cotton sample before and after cleaning, conditioning, and drying by the various methods. Fiber length distribution studies were made on samples selected to represent ex-
treme ginning and handling conditions.
All of the lint samples were classed at Phoenix, and some samples representing important tests were also classed at El Paso to provide a double check on the conclusions to be made based on classification.
The 24 roller gin establishments in operation in the West in 1940 previously mentioned were resurveyed by T. C. Walton in 1941 along with the 13 new gin outfits installed in 1941. The new gins had a total of 143 rollers. The other gins had a total of 346 rollers, bringing the total number in 1941 up to 489 as compared to 328 in 1940. In 1940 the roller gin plants ginned an average of 100 bales per stand; in 1941 approximately 150 bales per stand due to the expansion of SXP production in new areas of growth. Six of the new gins were installed in the El Paso Valley of Texas, 4 in the Mesilla Valley of New Mexico, and 1 in the Gila Valley and 2 in the Salt River Valley of Arizona. All except one of the plants were installed with doffers, but the doffers were used only when steam was successfully used in eliminating static.
While very good progress was made in the American-Egyptian cotton ginning investigations in 1941; there remain three unsolvedproblems especially in engineering developments. The engineers concluded that efforts should be made (1) to devise suitable crank mechanism for satisfactorily running the gins at high speeds, and better grids for shedding the seed faster; (2) to concentrate on the improvements to the lint flue system for higher efficiency and economy; and (3) to develop acceptable methods for controlling or eliminating static. Unless the latter is accomplished, the lint flue may not be completely successful. Therefore, the main objectives of the program must involve further developmental work by the ginning engineering staff.
Lint Flue Research, 1936-45
Lint flue studies which began in 1936 continued to 1945 and included first, the series A or round lint flue shown in drawing fig. 54 and depicted in photo fig. 61, on page 77.
When roller ginning problems again demanded attention, in 1941 much of the research work was conducted at the Pirna Indian Agency roller gins, Sacaton, Arizona, where cooperative work of the Department was then being handled in the production of Pima Cotton. Figure 61 shows one phase of this work.
In the second or series B types of suction lint flue studies, a graduated rectangular supplanted the previous round flue as was shown in fig. 62. Several nozzles with 4 x 4-inch take-offs were tested between the gin stands and graduated rectangular lint flue. The best nozzle is shown in fig. 63.
The series A and B types, illustrated in previous figs. 61 and 62, of lint flues were superseded by the series C overhead systems developed by Agricultural Engineer Gerald N. Franks in 1943. This new system marked a radical departure from previous studies. All trunks were rectangular and graduated in size, each stand take-off being 6 x 6 inches square, with dampered suction regulators, U-tube water gauges, and hinged nozzles. Figure 64a is an interior photo taken at the SanCarlos roller gin, Casa Grande, Arizona, (Courtesy Western Cotton Products Co.) and fig. 64b gives nozzle details.
In the tests at the San Carlos gin from 1943 to 1945, 12 McCarthy type 40-inch roller gin stands were employed, grouped in threes per gin flue for delivery tothe condenser main intake trunk. Cranks operated at 807, pushers at 165, rollers at 100, line shaft at 360, and counter shaft at 400 revolutions per minute. A type C size 45 fan wheel in a size 50 Boardman fan casing operated at 1614 rpm. This fan drew 8356 cubic feet of air per minute at 6" water gauge static pressure, 2. 7" velocity pressure, and 33 horsepower load.
A total of four gin trunks increased in size from 6-5/8 inches square to 9-1/4 inches square to 11-1/2 inches square for each three stands andthen delivered into a 46 x 11-1/2 inch rectangular overhead main duct to the suction condenser.
During the operations on August 19, 1943, air volumes of 760 to 700 cfrn per gin stand handled the roller delivery satisfactorily. The regulated air nozzles below the rollers showed static pressures on the roller hood ranging from 0.7 inch to 0.3 inch. On September 12, 1945, Western Cotton Products Co. reported ginning 70 bales of SXP cotton for the 1944 season. U-tubes were attached below the hinges of the nozzle hoods, and adjustable dampers enabled the operator to maintain uniform suction on all rollers. This usually averaged 1/2 inch on the individual U-tubes.
The principal value of these developments resided in the fund of practical information obtained by the Ginning Laboratory and the proving that ginned lint from roller gins could be pneumatically conveyed to the press without damage and considerable saving in hand labor. It was found that 700 cubic feet of air per gin stand was desirable for the design here described, but lesser volumes are possible with minor changes in the nozzles. Fan horsepower per gin stand, as shown on special power readings taken August 19, 1943, ranged from 2.75 to 3.17 horsepower per stand, and air volumes ranged as above stated. Full construction details are on file at the Southwestern Cotton Ginning Research Laboratory.
The final conclusions, reached from these extensive experiments with roller ginning suction lint handling systems, were dual. First, the system used at the San Carlos gin proved that roller ginned long staple cottons, such as Pima and sea-island varieties, could be pneumatically handled in lint flues without damage to quality or smoothness of the sample and that minor change of the Franks' design, in the light of information provided by the tests, would make the system feasible for commercial use. Second, that objections to heavy power consumption and first cost of construction involved in the test designs could be largely overcome by using a single larger lint flue, a double box press with improved suction condenser, smaller nozzle areas at the ginning rollers, and careful redesign of dimensions in the major elements.
"Cooperative Tests and Results at San Carlos Roller Gin, Casa Grande, Ariz. "
Note: The Western Cotton Products Co. (throughtheir. Mr. Tom RoLlow, Mgr. and L. A. Brewster, Master Mechanic) arranged informally with Young for a series of trial tests of the crankassembly at the San Carlos Gin. Twenty-four stands were in the San Carlos ginxtery and the test one with Government crank assembly was operated at 840 crank speed; 110 rpm roller speed, and without doffer.
"After 500 hours of almost continuous operation, the #6 tapered pin shown in photo No. 1910 was sheared. For this, the ginner first substituted a 7/16-inch straight bolt, but within 100 hours of operation a 1/2-inch straight bolt was inserted. After 640 hours, one wooden bearing of a crank leg went out at the top, and the experimental apparatus was removed from the stand. Main bearings, oil housing, felt seals, cross rail all showed O.K. Wear on
* Government file photos #1910 and 1011, not here reproduced.
crankshaft was . 0003; on crank legs . 0005; on wrist pins . 004; on crank leg oil sleeve .007. It was noted that the crank rail should have a center support.
"In the San Carlos Gin at Casa Grande, other roller gin stands were fitted with ball-bearing eccentrics developedby Mr. Brewster, whose estimated costs have never been given to us. These required new steel framing under the stands made of 6" x 3" I-beams. Mr. Brewster's eccentrics have been very good, but they also go out of service from time to time. He has been operating these at 807 to 980 rpm at San Carlos Gin with rollers at 100 and pushers at 165.
"Lubrication of roller gin. crankshafts, crank legs, and wrist pin bearings is one of the greatest problems in roller ginning, and especially in the modernization and maintenance of the older McCarthy type gins. Oil-soaked wooden bearings on crank legs have been used in the Southeastern states and in the Southwestern irrigated regions for many years, but the speeds of the cranks have had to be held down to about 600 rpm, and very frequent oiling has been required. Brewster's use of Micarta wedge blocks (a bakelite composition) against steel pins for the upper bearing of the crank legs (wrist pin bearing) has proved satisfactory to the Western Cotton Products Co., and his development of large size ball-bearing eccentrics, sealed in with Zerk fittings for greasing, have been used in many of the company gins.
"Armour of Phoenix produced bronze crank legs with hollowed reservoirs, but these have been rather clumsy and heavy. Ha.rdwicke-Etter. Co. , and Murray Co. , on their newest roller gins have employed both ball and bronze bearings.
"In the 1942 design of crank and crank legs here reported, the main bearings probably required lubrication every 1000 hours of operation. The wrist pins on this equipment required lubrication every 24 hours.
"Feeding oil into the main cranks in an improved design may be a forward step on the part of the Department. In this improvement, oil would be supplied to a hole in the end of the main crank shaft, thence through an oil hole to the pin where centrifugal force would assist in the lubrication. This method would simplify construction of the oil housings and seed guards now needed.
"For lubrication of wrist pins at the top of the crank legs, a real improvement over old unsatisfactoryznethods could be made by using oil-bearing bronze bearings which go under trade names such as 'Oilite' and 'Compol to indicate that they are oil retaining. Use of these materials would probably necessitate only minor changes in present designs. The wrist pin design employed by the Laboratory on these FY 1942 tests gave sood service and appealed to the operators. It was lubricated with grease, however, and if an oil reservoir could be utilized along with oil retaining bronze pins inserted into the wrist pin, it should be superior.
"Auxiliary Research Activities: In addition to the assignments on the crank shaft, crank legs, and bearings, several other research assignments were given attention at Sacaton, Arizona, during the period here covered.
"A high-potential static eliminator was installed about 1-1/2 inches above the roller and doffer on one of the stands in the main gin. No difference was observed in its action when placed over either roller or doffer, and when it was positioned between the two, it worked well in any of those positions, and if the commercial cost of such static eliminator is not excessive, they could be installed in the commercial gins with satisfactory results. When the static eliminator was connected to the electric supply, thus giving a 14, 000 volt high-potential de-ionizing effect in that area of the main tube or eliminator, the effect upon the cotton fiber was noticeable at once. The fibers did not carry back beneath the knife (backlash), nor did they adhere to the doffer or metal surfaces of the gin. During static conditions, when the eliminator was shut off, the cotton began at once to cling to the roller and to metal surfaces, rendering the doffers ineffective and giving other operating troubles. With this type of static eliminator, the lint flue and doffers seem to be given better chances for successful operation.
"Desert type of air conditioners were installed in the windows of the roller gin by the engineers, and these raised the humidity of the ginning room appreciably. It is possible that since the roller gin rollers heat up during operation, and may hereby increase the static trouble, that the rollers could be cooled by some system which uses moist air. ASsistance of the engineering physicist is necessary in such devices.
"Seed grids on roller gins are also needing improvement and development. At Stoneville, three test grids were made up from bar steel and 3/ 16 inch fingers welded thereto. Spacings of these fingers were 5/16, 3/8, and 7/16-inch apart respectively, giving a smooth rounded discharge port which J.S. Townsend recommends for such work. Several ideas on seed grids have come to mind in this work. First, a seed grid might be made with 3/8-inch spacings and with alternating fingers bent down so that the ends of the seed grid would give more space for the seed to fall through. Such a grid should be placed quite close to the moving knife, and the amount of the depression of alternate fingers found out by testing, bringing the bending to a point where seed cotton leakage through the space was imminent. A horizontal belt with barbs could be placed below the grid so as to return any cotton that had leaked through. Possibly no barbs would be necessary if a vertical lift belt had them and the horizontal belt merely carried the cotton over to it. Several other seed grid ideas could also be tried.
"The tests will show what results were obtained from the desert fans. Since the lint flue withdraws a large volume of air from the ginning room, this exhaust air would pass through an airwasher and be returned again or be us e d to condition incoming seed cotton. It is now difficult to meet the extremely dry conditions at these cotton gins, when atmospheric conditions tend to produce static electricity and when conditioned air is not used over again.
"Conclusions and Comments: From the findings and experiences of these FY 1942 tests, the Laboratory can make up better cranks and crank legs. The heavy duty bearings of ring-oiling type appear to be satisfactory. New guards and simpler oiling for the cranks are needed, and are being devised. Better wrist pins and improved lubrication for them is also being worked on. "(End of Report).
In October 1943 at Las Cruces, New Mexico, in cooperative tests at the Las Cruces Roller Gin which has since been dismantled, engineering staff member Ray C. Young began a series of static elimination studies on roller gins, using the two methods of high voltage static eliminator bars and moistening systems.
Plans of high voltage static eliminator bars as setup by Young and Harmond at San Carlos Roller Gin, Casa Grande, Arizona, and also at Las Cruces, New Mexico, during September and October 1943; A, floor plan at San Carlos Gin,.
As an alternative to applying moisture for eliminating static electricity at roller gins, the cotton ginning research engineers resorted to the use of
high voltage static neutralizer bars. In the fall of 1943, Messrs. Young and Harmond made tests of these neutralizer bars at Casa Grande, Arizona, and Las Cruces, New Mexico. Figures 65a and 65b respectively show gin building floor plan of stands and wiring at the San Carlos Gin at Casa Grande and partial side elevation of cotton condenser installation at Las Cruces. In the light of more recent tests than those of 1942, it has been found that such installations are not adequate under all ginning conditions.
Several moisture setups were also used in which Hardwicke-Etter Co. , assisted with some of their steam and water spraydevices as delineated in fig. 43. The Department's steam vaporizer layout for the gin stands is outlined in figure 66.
Plans for high voltage static eliminator bars as setup by Young and Harmond at San Carlos Roller Gin, Casa Grande, Arizona, and also at Las Cruces, New Mexico, during September and October, 1943; B, condenser wiring where static bars were placed in vicinity of a doffing roller at the discharge.
When substitutes for expensive walrus hide and other leathers were being sought in the early '30s, the Department's research engineers and technologists turned to plied packings. The plied canvas - rubber packings at first employed from 11 to 15 alternating layers of heavy canvas and natural black rubber as discussed in connection with figures 39 to 41. Spool windings of this material frequently produced objectionable stains in the lint because heavy
knife pressures peeled the rubber from between the canvas layers more readily than was possible with spiral winding. About 1948 white synthetic layers began to replace the black natural rubber.
It may be appropriate at this point to say that during the 1930 -44 renewal of roller ginning activities in the Southwestern States of this Nation, a number of makes and models of roller gins were employed, among which were the following: Platt Bros. & Co., Ltd.; Dobson and Barlow; Liberty; Sultry; Coats; Talley; Armour; Continental; Murray; Hardwicke-Etter; Foss; and Middleton. Many of these were further improved by the late L. A. Brewster, whoinstalled ball bearing cranks and durable wrist pins for the moving knives. These foregoing gins used rollers from 6 to 8 inches in diameter, operating at 100 to 125 rpm, and principally covered with walrus hide or packing material.
In this same period, crank speeds for the moving knives ranged from 650 to 800 revolutions per minute; and the ginned lint turnout was from 1 to 1- 1/2 bales per gin stand per 10 hours. Ginning Laboratory tests in the Southwestern states showed at this time that a crank speed of 930 rpm and a roller speed of 150 rpm on 6-inch diameter rollers turned out 34 percent more ginned lint than did speeds of 650 and 125 respectively. It was also found that spool-wound rollers ginned somewhat faster than did spiral wound, but 7- and 8-inch diameter rollers were almost 1/3 slower than 6-inch rollers when operated at the same roller and crank speeds. In other words, the smaller diameter rollers appeared to have greater capacity.
OTHER ROLLER GINNING DEVELOPMENTS, 1930-58
Several roller gin designs of promise have been tendered to the Government Ginning Research Laboratories for study. Among these have been the. Cox cone-type roller gin, the Pettit roller gin, and several others. Each has had features of merit, but the trade in general at that time did not see its way clear to pay for higher priced units because of the uncertainties of long staple cotton crops.
Double box presses at roller gins have been slowly replacing the older single box presses. With these have come lint cleaners as well as pneumatic and belt lint handling systems previously mentioned. So far as is known, the U. S. Department of Agriculture's ginning engineers were the first to use lint cleaners on a roller ginning setup, and this was accomplished very, success•• fully in 1952 at Mesilla Park, New Mexico.
Seed handling improvements, common to saw gins, have also gradually found their place in modern roller gins, so that small-pipe pneumatic seed handling may be cheaply and effectively employed.
From 1955 to 1957, the USDA Cotton Ginning Research Laboratories did much experimental work on swastika type revolving moving knives for roller gins, both at Mesilla Park and at Stoneville. Cooperative runs were made also by the White Gin Association at Canutillo, Texas on this type of moving knife. Figure 67 shows the principal features of this idea in which the speed of the rotary or swastika knives ranged from 23.0 to 500 rpm in the tests.
Reports in detail have been issued by the Laboratory and are not repeated here. Suffice to say, however, that while this design had several good features in, an increased capacity and simplicity of construction there was a constant hazard of seed cracking and a wide variability of samples from very good to poor.
Other investigations toward improved roller ginning are constantly in progress, and the Government Laboratories have been trying out a series of new ideas advanced by staff members. Among these ideas is a public patent applied-for invention by Agricultural Engineer James M. Williams, Jr., and associates, which is of interest because of its extremely high capacity, namely up to 20 pounds of ginned lint per hour per inch of roller length, or over 400 pounds per hour on a 20-inch roller gin. Figure 68 affords a simple line diagram of the Williams' idea, wherein an endless chain of bar moving knives, having suitable gaps, travels at high speed over the upper surface of the ginning roller and fixed knife. Ginned seed and some unginned locks travel beyond the end of the fixed knife to one point of disposal and reclamation, while the ginned lint travels from the ginning roller downwards in conventional style. Williams has increased the ginning roller size to approximately 12 inches diameter and has worked on other elements toward perfection of the unit. A more detailed description of the Williams' flight-bar gin is to be found in the Cotton Gin and Oil Mill Press issue of August 9, 1958.
