Abstract: The present invention discloses a structure for mounting a coin-filter filtering foreign materials contained in hydraulic fluid on a fixing groove formed at an inlet side of an orifice without using O-ring. A coin-filter mounting structure according to the present invention comprises a body having a fixing groove formed at an inlet side of an orifice, and a holder supporting the border of a coin-filter filtering out foreign materials contained in hydraulic fluid flowing through the orifice, and fixed to the fixing groove through plastic deformation after being mounted on the fixing groove.

Abstract: An expandable tubular coupling (10) includes first and second thread portions (12,14) each comprising a plurality of inter-engaging teeth (20,22), wherein at least one tooth on the first thread portion (12) engages a corresponding tooth on the second thread portion (14) and the remainder of said inter-engaging teeth (20,22) define respective gaps (32) therebetween.

Abstract: A seat valve in a motor vehicle wheel slip control system includes a valve tappet acting as a valve closure member, where the valve tappet is movably guided and aligned with a valve seat member by a centering sleeve that guides the valve tappet. The centering sleeve is articulated at the valve seat member.

Abstract: A bushing (52) has two bushing parts (52, 58), each of which includes a tubular section (54, 60) and a radial flange section (56, 62) Tubular section (54) is inserted into an opening (38) in a work member (40), from one side of the work member (40). Tubular section (60) is inserted into tubular section (54) from the opposite side (44) of the work member (40). A mandrel (M) is moved through the interior of the tubular portion of the bushing to radially and circumferentially expand the tubular portion of the bushing and move the flange sections against the opposite sidewalls of the work member (40). The tubular portions (54, 60) of the bushing (52) is radially and circumferentially expanded an amount sufficient to introduce fatigue life enhancing compressive residual stresses in the work member (40) immediately around the opening (38) in the work member (40).

Abstract: A toothed or splined shaft having an external toothing is pushed with clearance into an internal toothing of a hub, tooth to space, and the external toothing of the shaft is pressed together with the internal toothing of the hub. In the push-in position of the shaft, the latter is deformed plastically out of a cavity of the shaft in a radial circumferential widening operation and, so as to provide freedom from clearance between the spaces of the external toothing of the shaft and the internal toothing of the hub, the internal toothing engaging into the external toothing is pressed against the hub in such a way that the hub is deformed elastically and a press fit between the shaft and the hub is produced.

Abstract: The invention relates to an expansion tool for expanding tube ends. The expansion tool has an expansion mandrel and a counter-support, said expansion mandrel consisting of a tow-bar and an elastic rubber expansion element surrounding it. The counter-support supports the expansion element on the base extremity and radially surrounds it at a distance. In order to improve an expansion tool of the above-described kind, the tow-bar is anchored in a bolt fastening element and the counter-support can be impinged upon via a pressure bar element that projects beyond the bolt fastening element in the longitudinal direction of the tow-bar.

Abstract: The invention provides an installation tool for use with a battery operated drill or a corded electric drill for repetitive installation of caulk-in anchors. The installation tool utilizes the mechanical advantage of a threaded shaft to improve consistency of the holding reliability of the caulk-in anchor and controls the anchor setting process to insure proper installation while reducing installation time. The installation tool does not rely on bottom setting or a hammer strike to set the anchor, but can be set at a depth independent of hole depth. In one embodiment, the tool can be used with a through hole in the substrate and uses a combination of a threaded shaft and a controlled sensing spring to insure a more uniform installation of the anchor within the substrate across the entire length of the sleeve portion of the anchor, along with a visual check of proper setting of the anchor.

Abstract: A method is provided of radially expanding a connector for interconnecting a first tube to a second tube, the connector including a pin member extending into a box member. The pin and box members have cooperating support means arranged to support the pin member so as to prevent radially inward movement of the end portion of the pin member relative to the box member. The method involves radially expanding the connector, and supporting the pin member so as to prevent radially inward movement of the end portion of the pin member relative to the box member.

Abstract: In the present invention, at least one tubular blank and at least one article such as a metal stamping, to be attached to a hydroformed part, are loaded into a die. The tube is hydroformed using typical methods. The article is positioned in the die such that, when the tube is hydroformed, the final hydroformed tube contacts the article at least at a point. Attachment means, such as a laser welder, are provided with access to the contact point between the article and the hydroformed tube so that a tack weld or other attachment can be made between the article and the hydroformed tube while still in the closed die. The hydroformed tube and attached article are then removed as a joint assembly from the die.

Abstract: A tube plug kit including a tube plug having a housing member and a locking member, the housing member having a smooth longitudinal bore communicating with a threaded portion, the locking member mounted on the housing member. An insert member having a first threaded end portion is received within the threaded portion of the bore, an enlarged portion positioned to be drawn within the smooth portion of the longitudinal bore in response to rotation of the insert member in the longitudinal bore and a drive portion configured to receive a torque applying tool in a rotationally driving manner. A torque limiting region is located in the insert member to limit an amount of torque the drive portion can transmit to the first threaded end portion.

Abstract: A wheel bearing device is provided to prevent loosening of a hub ring and an outer joint ring that are fitted together. An irregular portion treated with hardening is formed on a fit face of the hub ring on an inside periphery of which the outer joint member is fitted. A low hardness portion of the outer joint member formed with hardness lower than that of the irregular portion is expanded in diameter to make it bite into the irregular portion. In this way the hub ring and the outer joint ring are unitized together.

Abstract: Hollow shafts, and particularly camshafts, are produced using an internal high-pressure forming (IHF) process. Cams and/or machine elements are mounted at intervals onto the outer surface of the hollow shaft, depending on the use of the latter, by a non-positive and/or positive fit, in a position appropriate to their function when the hollow shaft is placed in the forming tool. An element with approximately the same external diameter as the internal diameter of the hollow shaft is placed in at least one of the hollow shaft, and the hollow shaft together with the cams and/or machine elements that have been pushed onto the same and the inserted element are placed in an IHF tool. Once the IHF tool is closed, the medium is caused to act under the required high-pressure in the hollow shaft. At the same time as the medium is acting internally, at least one ram is pressed axially against at least one front face of the hollow shaft.

Abstract: An arbitrary position of a pipe is clamped and a connector is engaged with the pipe. Then, an end portion of the pipe is expanded with a tool such as a diameter expanding punch so as to caulk the pipe to the connector from inside. As a pipe fluctuation-absorbing portion, which is a relief space of pipe material, is provided in a portion of an inner face of the connector, when the diameter-expanding portion is formed, an excess pipe material is absorbed there and the length of the pipe is reduced and adjusted to an appropriate value. A portion in which the pipe fluctuation-absorbing portion is formed is not limited to a forward end portion of the pipe but it may be formed on an inner face of the connector corresponding to an intermediate portion.

Abstract: A method of connecting a first pipe to a second pipe having an end part fitting into an end part of the first pipe, comprising arranging the end part of the second pipe within the end part of the first pipe, arranging a sleeve of a deformable material between said end parts, and radially expanding the end part of the second pipe towards the end part of the first pipe so as to bias the sleeve between said end parts.

Abstract: A method for manufacturing a fuel inlet having a good sealing property and a screw structure formed in a precise position involves expanding one end of a long-length stainless pipe (metal pipe) using a cored bar, the tip of the expanded portion which becomes non-uniform as a result of the expanding step is cut off, a screw structure is formed in the expanded portion by using a punch, the tip of the expanded portion which becomes non-uniform as a result of the screw structure forming step is cut off, and thereafter curl forming is conducted to the end of the expanded portion which becomes uniform by using a die so as to provide a seal portion.

Abstract: A conduit connection joint is formed to connect a tube and a fitting body in fluid tight relation. The joint is made by axially compressing the tube in a bore in the fitting body so as to cause formation of an outwardly extending tube bead and at least one inwardly extending tube bead. The engagement of the fitting body and the tube may be further strengthened by a retaining ridge. The retaining ridge may be formed in the fitting body to engage the outwardly extending tube bead to further hold the fitting body and tube in engaged relation.

Abstract: A system and method for expanding, joining or securing a plurality of tubes by electromagnetic expansion to a plurality of sheets in a tubular heat transfer system. The system and method involve the automatic sensing and positioning of a electromagnetic coil in operative relationship with at least a portion of a tube and an inner wall of a sheet and then energizing the electromagnetic coil to expand the portion of the tube to engage the inner wall of the sheet, thereby securing the tube thereto. A tubular heat transfer system tube expander and method are also shown.

Abstract: A method of attaching a head rest guide tube to a seat back frame having an aperture extending therethrough includes inserting the guide tube into the aperture, and swaging the guide tube to form a swaged portion engaged with the seat back frame to thereby secure the guide tube to the seat back frame.

Abstract: The headrest support tubes are secured to the seat frame member not by the usual welding, but by gripping the web of the member between two rings or lock-beads swaged into the metal of the tube. The first ring is swaged-out by compressing the tube. The tube, with the one ring, is then assembled into a through-hole in the web of the frame member. Then, the second ring is swaged into the metal of the tube, on the other side of the web, and the web lies gripped between the rings. The seat frame member may be an I-section extrusion, or a round tube with localised squeezed-flat areas, flanked by flanges.

Abstract: The method of the present invention is intended to be used in association with a headed fastener such as a tee nut, but not limited to a tee nut. The present method contemplates embodiments of a riveting pin having protuberances that cause the flared end of the shaft to be flared in one or more discontinuous portions of the circumference of the shaft, whereby “push out” and “spin-out” are deterred. Where the length of the fastener shaft is no longer than the thickness of the material through which it is inserted, a first design of flaring pin is provided. Where the length of the shaft of the fastener employed is greater than the thickness of the material through which it extends, a second embodiment of flaring pin is employed. In the former case, at least one discrete portion of the circumference of the shaft is flared into the wall of the passageway through which the shaft extends.

Abstract: A tool for producing expanded camshafts. The tool includes at least one modular die made up of segments that are joined together and that are provided with opposing slides for centering and aligning the cams around the axis of the shafts.

Abstract: A method for installing an expandable stiffener includes providing an assembly including a first sidewall and a second sidewall connected at a leading and trailing edge such that a cavity is defined therebetween, forming an opening extending through the first sidewall and the second sidewall, inserting a first expandable sleeve through the assembly opening such that the sleeve extends between the first and second strut sidewalls, and coupling the sleeve to the first and second sidewalls.

Abstract: The invention provides an installation tool for use with a battery operated drill or a corded electric drill for repetitive installation of caulk-in anchors. The installation tool utilizes the mechanical advantage of a threaded shaft to improve consistency of the holding reliability of the caulk-in anchor and controls the anchor setting process to insure proper installation while reducing installation time. The installation tool does not rely on bottom setting or a hammer strike to set the anchor, but can be set at a depth independent of hole depth. In one embodiment, the tool can be used with a through hole in the substrate and uses a combination of a threaded shaft and a controlled sensing spring to insure a more uniform installation of the anchor within the substrate across the entire length of the sleeve portion of the anchor, along with a visual check of proper setting of the anchor.

Abstract: A method is provided of radially expanding a connector (24) for interconnecting a first tube (18) to a second tube (20), the connector including a pin member (26) extending into a box member (28). The pin and box members have cooperating support means (26, 28) arranged to support the pin member so as to prevent radially inward movement of said end portion of the pin member relative to the box member. The method comprises radially expanding the connector (24), and supporting the pin member so as to prevent radially inward movement of said end portion of the pin member relative to the box member.

Abstract: A process for forming a metallic tubular connector of the type having a cylindrical shell which extends circumferentially about a tubular body for joining said tubular connector to a conduit. The process involves using a first forming machine to form a first peripheral bead in a first end portion of a tubular metallic body, having a substantially uniform diameter and wall thickness, reduce the outside diameter of a second end portion, and slope an intermediate surface portion. Then, a second end forming machine tool, carrying a metallic socket, freely receives the tubular body second end portion, contacts the sloped intermediate surface portion, forms a second peripheral bead adjacent the first peripheral bead, while an annular end surface of the socket is compressed and locked between the first and second beads. Further, the tubular body is manufactured from a 5000 series aluminum alloy material.

Abstract: Bushings (26, 52, 66, 86) are provided that have a tubular portion that fits within an opening (38) in a work member (40) and a radial flange at each end of the tubular portion. In a first embodiment, a first bushing part includes a tubular section (30) and a radial flange section (32) at one of its ends. When the tubular section (30) is within the opening (38), and the radial flange section (32) is against a first wall (46) of the work member (40), an end portion (42) of the tubular section (30) projects outwardly of the opening (38) beyond the second sidewall (44). A second bushing part (28) has an annular flange portion (34) with a center opening (36) in which the projecting end portion (42) of the tubular section (30) fits. The second bushing (52) has two bushing parts (52, 58), each of which includes a tubular section (54, 60) and a radial flange section (56, 62).

Abstract: The method of the present invention is intended to be used in association with a headed fastener such as a tee nut, but not limited to a tee nut. The present method contemplates embodiments of a riveting pin having protuberances that cause the flared end of the shaft to be flared in one or more discontinuous portions of the circumference of the shaft, whereby “push out” and “spin-out” are deterred. Where the length of the fastener shaft is no longer than the thickness of the material through which it is inserted, a first design of flaring pin is provided. Where the length of the shaft of the fastener employed is greater than the thickness of the material through which it extends, a second embodiment of flaring pin is employed In the former case, at least one discrete portion of the circumference of the shaft is flared into the wall of the passageway through which the shaft extends.

Abstract: Disclosed herein is an apparatus and method for manufacturing an exhaust emission control device, and the exhaust emission control device formed thereby. The method of manufacturing an exhaust emission control device, comprises: disposing a viscous-elastic material around at least a portion of a substrate to form a wrapped element. The wrapped element is compressed at a first compression rate and at a second compression rate that is slower than the first compression rate, and the wrapped element is introduced into a housing.

Abstract: A symmetrical self-attaching female fastener including a body having a bore, and identical integral tubular barrel portions extending from opposed ends of the body coaxially aligned with the bore. The installation method includes driving either barrel portion through an opening in a panel, which may be formed by piercing the panel with the barrel portion, and simultaneously deforming both barrel portions radially outwardly and inwardly, wherein one barrel portion entraps the panel and the other exposed barrel portion is folded at an acute angle relative to the bore to reduce the overall length of the assembly.

Abstract: After a rod 4 with a pre-formed annular groove 21 is fixed on a reception die 26, a collar blank 23 is fitted on the rod 4. Then the die 25 is advanced toward the reception die 26 along the rod 4, urging the collar blank 23 into its forming bore 27, causing the inner diameter portion of the blank 23 to enter into the annular groove 21 by a plastic flow. Subsequently by a further advancement of the die 25, an annular projection 29 formed at the bottom surface of the forming bore 27 is driven into the end surface of the collar blank 23 to cause the blank to 23 plastically flow further into the annular groove 21.

Abstract: A method of securely attaching a plate to a malleable metal rod includes forming an integral, generally annular projection on one end of the rod. An opening through the plate is configured to receive the annual projection on the rod. The annual projection is inserted through the opening in the plate and is permanently deformed radially outwardly to overlie and contact the plate at a plurality of spaced locations. The deformations in the annular projection securely attach the plate to the rod.

Abstract: A method of fabricating a driveline assembly including the steps of inserting a first member within a second member, heating the first member to a temperature greater than that of the second member and inserting both members into a die. The inner surface of the die includes an interlocking torque transferring profile. Fluid pressure is applied to the inner diameter of the inner member to expand both members into the profile on the inner surface of the die. The inner and outer members are then removed from the die and cooled such that both members are at a common temperature. Because the inner member was at an elevated temperature, and thereby expanded a greater amount than the outer member, cooling of the members results in a clearance between the members that provides for relative axial movement between the inner and outer members.

Abstract: A method for connecting a headrest guide tube in a vehicle seat frame comprises the steps of forming a hole in the seat frame, inserting a headrest guide tube into the hole, axially compressing the tube to form a pair of rings on opposite sides of the frame wall, and then axially crushing the rings to form a pair of beads tightly clamping the headrest guide tube to the seat frame. During the crushing process, a portion of the headrest guide tube is bulged into a notch in the hole in the seat frame to prevent the guide tube from rotating with respect to the seat frame.

Abstract: The invention relates to a method and apparatus for the production of double-walled hollow sections by means of internal high-pressure forming, a first hollow section being inserted into a second hollow section, after which the double-walled hollow section thus formed is subjected to high internal fluid pressure in such a way in an internal high-pressure forming die that the double-walled hollow section is expanded. During this process, an air gap is formed between the first, inner, hollow section and the second, outer, hollow section.

Abstract: A fuel rail formed by hydroforming. The hydroforming process includes applying a seal onto a fuel tube, and installing fuel injector blocks, including fuel injector ports, onto the tube in desired positions. The fuel tube assembly is placed in a die assembly, and pressurized fluid is supplied to the interior of the tube. The pressurized fluid causes the tube to expand outwardly into engagement with the blocks, and to pierce holes through the tube within each of the blocks to provide fluid communication with the associated fuel injector and other ports.

Abstract: A process and system for manufacturing a built-up camshaft by which the operational safety of the camshaft is ensured in a simple manner in any engine operation and the camshaft can arbitrarily be adapted to abutments which have different positions because of the individual engine construction. At least one cam is pushed onto a hollow shaft, after which the hollow shaft is expanded between the two faces of the cam which extend transversely with respect to the longitudinal course of the hollow shaft and at the respective bearing point by means of a highly pressurized pressure fluid. This fluid is delivered by a lance-shaped probe introduced into the hollow space of the shaft. On the one hand, a press fit occurs between the cam and the hollow shaft and, on the other hand, a bulging of the bearing point of the hollow shaft occurs which bridges the distance between the hollow shaft and the abutment.

Abstract: Process for producing a tubular component which comprises sections which are intentionally different from one another with regard to one or more aspects selected from the group consisting of aspects including material, thickness, size, more specifically circumference or diameter, and the like, and hydroforming of the component, in which process the component is produced by rolling up a substantially flat sheet, which flat sheet substantially corresponds to a flat blank of the tubular component.

Abstract: A method of hydroforming a reinforced tube comprising providing a metal tubular blank having an interior defined by an inner surface and an exterior defined by an outer surface. A metal reinforcing member is provided and inserted into the interior of the tubular blank. The reinforcing member is engaged with the inner surface of the tubular blank and is attached to the inner surface of the tubular blank. The tubular blank and reinforcing member welded thereto are placed into a hydroforming die having die surfaces defining a die cavity, and pressurized fluid is provided within the tubular blank so as to conform the tubular blank with the die surfaces of the die cavity.

Abstract: A conduit connection joint is formed to connect a tube and a fitting body in fixed fluid tight relation. The joint is made by compressing the tube in a bore in the fitting body so as to cause formation of at least two beads in the tube during the engagement of the tube to the bore wall. A retaining ridge may be formed in the fitting body to further hold the fitting body and tube in engaged relation.

Abstract: The present invention relates to a system and a process for assembling a tube in a connecting element, and a housing for a braking assistance servomotor, in a device for controlling braking including such a system. The system for assembling a tube (10) with a female connecting element (11) comprising a longitudinal bore (14) provided with a transversal shoulder (14a), system in which a hollow end portion (18) of the tube is inserted in the said bore in abutment against its shoulder, is characterized by the fact that the longitudinal wall of the said end portion comprises a zone (23) deformed by compression between the said shoulder and the remainder of the tube and deformed transversally within the internal wall of the bore to provide mechanical connection and tightness between the tube and the connecting element.

Abstract: A tool for forming an armature guide eyelet. The tool having a body with a working end, a support end and at least one sizing rib disposed along a longitudinal axis. The at least one sizing rib has a perimeter having a first portion and a second portion. The first portion has a substantially constant distance Dc, from the longitudinal axis. The second portion has a varying distance Dv from the longitudinal axis. Also, a method for forming the armature guide eyelet with the tool. The method including aligning at least one non-uniform sizing rib and an armature guide eyelet having a constant inner diameter along a longitudinal axis and forming the constant inner diameter of the armature guide eyelet into a non-uniform inner diameter with the at least one non-uniform sizing rib.

Abstract: Process for manufacturing a metal can with a threaded neck on which a removable head can be fitted, includes the steps of forming a can with a closed bottom end, a cylindrical wall and an open top end, forming a neck at the open top end, obtaining a ring with a spindle hole of known diameter and a threaded external surface, sleeve fitting the ring by driving the spindle hole over the neck, and plastically expanding the neck by an amount sufficient that its outer diameter exceeds the diameter of the spindle hole when unstressed.

Abstract: A method for manufacturing an air-gap-insulated exhaust pipe having a branch stub, as well as an exhaust pipe produced according to such a method and a tool for forming such an exhaust pipe. Two tubes are inserted into one another to form a double tube. The double tube is placed in a first internal high-pressure shaping tool, and exposed to internal high pressure fluid such that it expands to match the contours of the engraving of the first shaping tool, and a double-walled branch stub is blown out of the double tube. The partially formed double tube is then placed in a second internal high-pressure shaping tool, with the double tube being surrounded, between the two ends including the branch stub, circumferentially and throughout by a corresponding design of the engraving, by an expansion chamber.

Abstract: A method for connecting a headrest guide tube in a vehicle seat frame comprises the steps of forming a hole in the seat frame, inserting a headrest guide tube into the hole, axially compressing the tube to form a pair of rings on opposite sides of the frame wall, and then axially crushing the rings to form a pair of beads tightly clamping the headrest guide tube to the seat frame. During the crushing process, a portion of the headrest guide tube is bulged into a notch in the hole in the seat frame to prevent the guide tube from rotating with respect to the seat frame.

Abstract: A vertical pipe expander to be used to expand the pipes assembled with fins of finned heat exchangers comprises, on a supporting frame, supports for rods of pipe expanding cones, performing vertical translational motion and arranged above a seat for a heat exchanger to be subjected to pipe expansion. At least one cone supporting rod magazine is further provided that is arranged vertically with the cones directed downward, for arrangement, during machine setup, at the seat, the supports for the rods being constituted by a rod engaging and supporting device. The rod engagement and support device is associated with a device for selecting the rods of the magazine to be engaged or released.

Abstract: In the present invention, at least one tubular blank and at least one article such as a metal stamping, to be attached to a hydroformed part, are loaded into a die. The tube is hydroformed using typical methods. The article is positioned in the die such that, when. the tube is hydroformed, the final hydroformed tube contacts the article at least at a point. Attachment means, such as a laser welder, are provided with access to the contact point between the article and the hydroformed tube so that a tack weld or other attachment can be made between the article and the hydroformed tube while still in the closed die. The hydroformed tube and attached article are then removed as a joint assembly from the die.

Abstract: A method of manufacturing a sleeve mechanism without the use of machines by using a hydroforming process. The method includes the steps of providing an inner sleeve, an intermediate sleeve, and an outer sleeve concentrically within one another. The concentric sleeves are then expanded by using a hydroforming process such that an external thread is formed on the inner sleeve and an internal thread is formed on the outer sleeve. After the hydroforming process, the intermediate sleeve is removed by using any desired manner, such as melting or chemical dissolution. The relatively small space remaining between the inner and outer sleeves allow them to freely rotate about each other to ensure smooth operation of the screw and sleeve mechanism. Alternatively, the inner and outer sleeves may be hydroformed in separate operations.

Abstract: A method of manufacturing a collapsible driveshaft assembly includes the steps of disposing an end of a first tube within a forming die having a non-circular cross sectional shape, expanding the end of the first tube into conformance with the die cavity, inserting an end of a second tube is inserted within the deformed end of the first tube, and expanding the end of the second tube into conformance with the end of the first tube. As a result of this expansion, outwardly extending regions and inwardly extending regions of the second tube extend into cooperation with outwardly extending regions and inwardly extending regions of the first tube so as to cause the first and second tubes to function as cooperating male and female splined members. As a result, a rotational driving connection therebetween to form the driveshaft. When a relatively large axial force is applied to the ends of the telescoping driveshaft, the second tube will move axially within the first tube, thereby collapsing and absorbing energy.

Abstract: Guide-tubes for supporting the headrest of an automobile seat are lock-beaded into the top-rail of the seat-frame. The guide-tubes are formed from pieces of sheet metal, folded over to form cylindrical tubes. The edges of the sheet are interlaced, by means of dovetailing tabs and sockets, which are stamped into the side-edges of the sheet. The interlacing tabs and sockets are not present over the middle portion of the guide-tube, where the lock-beads are formed.

Abstract: A process for forming an elongate structural element of desired shape being of large and small cross-sectional dimensions at spaced locations along its length, the process including the steps of: (i) selecting a first tube for forming a first selected length of the element having cross-sectional dimensions within a first range of relatively small cross-sectional dimensions within the hydro-forming-elongation ratio capabilities of the material from which the first tube is formed, said first tube being of a first constant cross-sectional dimension along its length, (ii) selecting a second tube for forming a second selected length of the element adjacent to the first length, the second length of the element having cross-sectional dimensions within a second range of relatively large cross-sectional dimensions within the hydro-forming elongation ratio capabilities of the material from which the second tube is formed, said second tube being of a second constant cross-sectional dimension along its length which is