Hydraulic Ram Research Articles

A rig for measuring the forces on a towed wheel

A tractor-drawn rig is described for measuring the forces on a towed wheel in normal agricultural conditions. The test wheel is mounted on an internal framework connected to the main frame (a balanced four-wheel trailer) by transducer links. A vertical load of up to 35 kN can be applied by a hydraulic ram to the test wheel, which can be between 711 mm and 940 mm in diameter. The rig is towed at constant speed and all forces on the test wheel, the ground speed, and the test wheel rotational speed are recorded. The test wheel can be angled to the direction of travel (slip angle) up to a maximum of 45° in 5° increments to enable steering forces generated by the wheel to be measured.

The American Water Ram, Part II

The American Water Ram, Part II

Ice forces on vertical piles : Nevel, D E; Perham, R E; Hogue, G B US Army Cold Regions Research and Engineering Lab report CR 77-10, April 1977, 9P

The amount of force that an ice sheet can apply to a vertical pile was tested by lowering a hydraulic ram device into a hole cut in an existing ice sheet. The device had a large base and shoved a relatively narrow vertical pile in a horizontal direction. Test variables were: pile widths - 1. 5 in. to 36.7 in.; pile shapes--flat, round 45 degree and 90 degree wedges; ice thickness--2.6 in. to 8.8 in.; and ram speed--0.07 in. sec. Air temperature was-6. 7 degree C. Forces and displacements were measured electronically. The findings are presented as a table of test results and as bar graphs of the resultant ice pressures versus the pile width-to-ice-thickness ratio, pile width and shape combination and pile velocity.

On the Release of Sperms in Atrichum

An antheridium of Atrichum contracts when it opens. This contraction rapidly ejects much of the mass of sperms because a fluid present in the base of the antheridial chamber acts as an hydraulic ram. The residue of sperms is slowly extruded as the same fluid takes up water. Photographs allow the construction of time courses that directly demonstrate the existence of two phases (rapid vs. slow) in sperm release. Antheridia open as quickly in 1 m sucrose as they do in water. Molar sucrose allows only the rapid phase of sperm release, caused by the contraction of the jacket, and the antheridia remain only partly emptied. This behavior in sucrose solution provides a convenient test for similarities among antheridia. The mechanism of sperm release that occurs in Atrichum occurs in Polytrichum and Mnium as well.

Indentation Tests to Investigate Ice Pressures on Vertical Piers

Abstract Controlled field and laboratory tests were performed to investigate the relationship between ice strength and the maximum ice pressures on vertical piers. The apparatus used in the field tests consisted of a flat indentor (75 cm wide) which was pushed through the ice by hydraulic rams. 27 tests were conducted on lake ice up to one metre thick. Ice pressures in the range 2.5 to 5.0 MPa were obtained for ice in good initial contact with the indentor. The ice pressures exhibited little sensitivity to variations in temperature, ice thickness and strain-rate for the range 7.5 × 10-7 to 4.4 × 10-3 s-1. The average unconfined compressive strengths obtained in the laboratory were about 20% higher than the average field ice pressures. In addition, the laboratory strengths were found to be sensitive to temperature, and to strain-rate in the range 1 × 10-7 to 1 × 10-3 s-1. The confined compressive strength was two to three times the unconfined strength. The failure modes observed in the indentation tests were similar to those predicted (before the tests) by an upper-bound plasticity model. The ability of the model to relate small-scale ice strength to field ice pressures is discussed.

Indentation Tests to Investigate Ice Pressures on Vertical Piers

AbstractControlled field and laboratory tests were performed to investigate the relationship between ice strength and the maximum ice pressures on vertical piers. The apparatus used in the field tests consisted of a flat indentor (75 cm wide) which was pushed through the ice by hydraulic rams. 27 tests were conducted on lake ice up to one metre thick. Ice pressures in the range 2.5 to 5.0 MPa were obtained for ice in good initial contact with the indentor. The ice pressures exhibited little sensitivity to variations in temperature, ice thickness and strain-rate for the range 7.5 × 10-7 to 4.4 × 10-3 s-1.The average unconfined compressive strengths obtained in the laboratory were about 20% higher than the average field ice pressures. In addition, the laboratory strengths were found to be sensitive to temperature, and to strain-rate in the range 1 × 10-7 to 1 × 10-3 s-1. The confined compressive strength was two to three times the unconfined strength.The failure modes observed in the indentation tests were similar to those predicted (before the tests) by an upper-bound plasticity model. The ability of the model to relate small-scale ice strength to field ice pressures is discussed.

Large electrodialysis stack development

In connection with the 100 MGD Yuma Desalting Plant to be built by the U.S. Bureau of Reclamation (Bu Rec), the U.S. Office of Water Research and Technology (OWRT) in 1975 contracted with Ionics, Inc. to design, build and field test a large electrodialysis (ED) stack. The Mark IV stack which evolved from this program has five to six times the desalting capacity of the standard commercial Ionics MK III stacks. The prototype MK IV stack contains 960 cell pairs, three hydraulic and electrical stages and has a nominal capacity of 250,000 GPD on 3000 ppm water at over 80% salt rejection and. over 70% water recovery . Lower desalting costs will result from the use of the large, tall Mk IV stack because of reduced floor space, reduced stack hardware costs and shorter hydraulic and electrical runs. Stack improvments include side entry to save space and fittings, a hydraulic ram to compress the stack and save assembly time, and the ability to remove any of the three stages independently from the stack for maintenance. The stack is serviced by an Ionics Aquamite XX skid. As is the case for all Ionics Aquamite units, the Mk IV/Aquamite XX combination utilizes the concept of polarity reversal to eliminate chemical feed. The stack has been successfully field tested at the OWRT Roswell Test Facility in New Mexico. Desalting data on water blended by the OWRT to simulate 1981 Yuma pre-treated feed water is presented. At 75° F the D.C. energy consumption was approximately 5.0 KWH/gal product water when desalting 170,000 GPD from 3000 to 550 ppm TDS, at 70% water recovery . The stack and the skid have been moved to the Bu Rec Yuma Desalting Test Facility where testing is expected to be initiated in October, 1976.

Research on the damage to aircraft composite material fuel tanks due to penetrating projectiles (hydraulic ram) at the naval postgraduate school

Research on the damage to aircraft composite material fuel tanks due to penetrating projectiles (hydraulic ram) at the naval postgraduate school

Vulnerability of advanced aircraft fuel to ballistic and simulated lightning threats

The Advanced Fuel Vulnerability program is aimed at assessing relative vulnerability and identifying hazards associated with advanced (all but natural petroleum) fuels to determine their feasibility for use in military aircraft. Although primarily concerned with military aircraft, these hazards would also apply in limited degree to commercial aircraft. The initial advanced fuel selected for testing was Liquid Hydrogen (LH 2). In addition to assessing it as a candidate petroleum fuel alternate, these tests with LH 2 (the coldest fuel under consideration) could reveal problems associated with a cryogenic fuel. Initial survey tests reported herein compared the response of confined LH 2 and JP-4 to ballistic impacts and lightning strikes. The reaction of LH 2 results in less severe hydraulic ram and reduced fire. The responses of LH 2 to lightning strikes indicate that strikes through vented gas external to the structure does not pose a serious problem. However, the internal arcing effect is a more complicated phenomenon and requires further investigation.

High pressure–low temperature apparatus for electrical conductivity measurements

Equipment is described for electrical measurements under hydrostatic pressures to 30 kilobar over the low to room temperature range. The piston and cylinder type pressure vessel of the high-pressure cryostat is actuated directly by a hydraulic ram at room temperature. Thermal isolation is achieved through use of long tension and compression members. Details about the self-stressing, double-walled cylinder are provided. Both the Bi I–II transition and an n–InSb manometer have been used for pressure calibration.

An Analysis of the Hydraulic Ram

An hydraulic ram is a pump in which the momentum of a driving stream of water undergoing a small head drop is used to pump a small portion of the stream to a head considerably greater than that of the supply. An attempt has been made to identify the features of the ram; the drive head and flow, the discharge (or pump) head and flow, the cycle frequency, and the system efficiency. Analytical results are expressed in terms of the ratio of the maximum drive velocity at drive valve closure to the maximum steady state velocity with the drive valve wide open. This ratio is always less than one. Comparison of the analysis with experimental results gives a numerical correlation of heads and flows. The cycle frequency and system efficiency are not predicted with great accuracy, but the trends are predicted correctly.

Large-Scale Model Test of Drilled Pier in Sand

A technique is presented for assessing the magnitude of skin friction for pier foundations in sand. The technique employs the results of interface direct shear tests between sand and the construction material; the results are presented in hyperbolic equation form. The test pier was 16 in. (407 mm) in diameter and 15 ft (4.6 m) long. The test pier was heavily instrumented with Carlson stress meters, electrical resistance strain gages, and calibrated hydraulic rams on the top and bottom of the pier. Comparisons of predicted and measured values of skin friction showed agreement within 5%. Bonded resistance strain gages on the vertical steel reinforcement are the most reliable instrumentation method. The magnitude of skin friction for point bearing piers in sand in prototype installations may approach 20% - 30% of the total load capacity. /ASCE/

Retraction system for multi-anvil presses

A hollow guide-pin system is described for retraction of the hydraulic rams of multi-anvil presses that saves weight and machining costs and improves mechanical proportions. The system also unclutters the anvil region, providing more access. The use of inverted rams and right/left-hand thread tie-bars and bases further reduces weight and cost.

A Theoretical Study of the Elastohydrodynamic Lubrication of Reciprocating Rubber Seals

This paper describes a method for calculating the pressure distribution, film profile, leakage rate and friction of a rectangular section rubber seal as used in hydraulic rams and jacks. The two basic equations, those describing the hydrodynamic pressure generation and the deflections of the seal surface have been solved simultaneously by numerical techniques. A solution was obtained which predicted film profiles qualitatively similar to those obtained experimentally. Solutions for outstrokes were obtained over ranges of variables as follows: sealed pressure (lbf/in2)…200–1,500500500sliding speed (ft/min)….150.5–25.015rubber hardness (IRHD).858555–85 Presented at the 29th Annual Meeting in Cleveland, Ohio, April 28–May 2, 1974

The Introduction of the American Water Ram, ca. 1843-1850

The Introduction of the American Water Ram, ca. 1843-1850

A potato harvester delivery conveyor with automatic discharge height control

A proportion of the damage sustained by potatoes at harvest time occurs during transfer from the potato harvester delivery conveyor to the trailer. A prototype delivery conveyor, designed to reduce this damage, was built and tested under commercial harvesting conditions. The conveyor has an automatic discharge height control consisting of a sensor ball mounted on the end of the conveyor and actuating an airswitch which causes a solenoid valve to operate a hydraulic lifting ram. The conveyor is in two parts, the distal part being capable of swinging sideways in the event of impact against the trailer tailboard. Results of tests show that the mean drop height can be held within the range 116–199 mm. This is an improvement on the mean drop heights of 390–780 mm measured under typical farm conditions on harvesters without automatic control of the delivery height of the discharge conveyor.

Apparatus for neutron diffraction at high pressure

Powder neutron diffraction data have been obtained on cesium metal above the two transitions at 42.5 and 43 kilobar using a piston cylinder apparatus. A Lucalox cylinder (high density Al2O3) (35.4 mm o.d., 6.35 mm i.d.) is radially supported by compressing two steel plates with a hydraulic ram leaving a neutron window between the plates ∼6 mm high. A 17° included angle was used between the cylinder and support plates. A tungsten carbide piston, driven by a second hydraulic ram, raised the pressure on the sample at three times the rate of increase of the support pressure.

L/2 (1) Cavity Growth and Collapse Phase of Hydraulic Ram

l/2 (1) Cavity Growth and Collapse Phase of Hydraulic Ram

Cavity growth and collapse phase of hydraulic ram

Cavitation begins almost immediately after a liquid-filled container is penetrated by a projectile travelling at ballistic speeds. The cavity grows to a maximum size, at which time it is approximately spherical, and then collapses. This process of growth and collapse is repeated several times, with a pressure pulse being generated at each collapse, as in the underwater detonation of an explosive. It is shown that the formulas developed for analyzing underwater explosions can be adapted to projectile penetration and used to predict the relationships between the period of the cavity growth and collapse cycle, the energy required to produce the cavity, the maximum size of the cavity, and the peak pressures generated by its collapse. The predictions are then compared with the results of previously conducted experiments. Observed and predicted maximum cavity radii are found to be in agreement and the predicted energies are compatible with the energy deposited per unit length of projectile travel by drag. Indirect evidence suggests that the magnitude of the peak pressure is also predicted satisfactorily.

Fuel tank wall response to hydraulic ram during the shock phase.

THIS Note outlines some preliminary work accomplished in a research program at the Naval Postgraduate School to study the effects of hydraulic ram in fuel tanks upon aircraft survivability and vulnerability. The problem of predicting the interaction of a high speed projectile with a liquid filled tank (hydraulic ram) is a complex but necessary study if kill probabilities are to be predicted for this type of event. Furthermore, to design survivable fuel tanks, it is necessary to understand hydraulic ram in detail. The hydraulic ram phenomenon may be divided into two phases: 1) the shock phase where the projectile exchanges some of its energy with the fluid by the production of a strong, nearly hemispherical shock wave originating from the entry wall, and 2) the cavity phase where further energy is imparted to the fluid by the production and collapse of a vapor filled cavity formed by separation of the fluid from the surface of the projectile as it moves through the tank. This Note considers the shock phase and examines the structural response of the entry wall during this phase.