US 2368651 A
Description (OCR text may contain errors)
Feb. l6, 1945. 1 R FLANNERY 2,368,651
sTAYBoLT' Filed May 9, 1940 Patented Feb. 6, 1945 UNITED STATES PATENT OFFICE STAY BOLT John Rogers Flannery, Pittsburgh, Pa. Application May 9, 1940, Serial No. 334,184
v claims. (o1. s55-1.5)'Y l My invention relates to staybolt assemblages, particularly for locomotive re box boilers; and it is particularly directed to -the construction of a staybolt, and to methods of testing a staybolt while it is in service.
In a locomotive boiler the water compartment is formed between two steel sheets that serve as the walls of the compartment. The two sheets arey held in pre-determined spaced relationship by a large number of staybolts extending through the space between the sheets, and suitably anchored to the sheets at both ends of the bolts.
The inner sheet is usually arch-shaped and covers the fire-box or combustion chamber. The outer sheet is also generally arch-shaped.
In order to provide a certain degree of adjustability between the two Yboiler sheets, so they may adjust themselves according to the relative temperatures existing under ambient temperature conditions, and under elevated operating temperature conditions, someof the bolts are so disposed as to provide a certain amount of pivotal movement' at one end. That end has been selected as the head end of the bolt which is mounted for pivotal movementat the outer sheet of the boiler. t
Two types of flexible bolts have been employed. One type is a bolt having a solid shank. The other type is a bolt having a passage of small diameter, on the order of three-sixteenths of an inch, extending axially throughout the length of the bolt shank, and slightly into, but not through, the head of the bolt. I
In each case, the bolt is provided with a slightly enlarged head having asubstantially spherical under surface which can pivotally adjust itself against a correspondingly shaped surface formed either in a hole in the outer sheet through which the bolt extends, or in a sleeve or cup that is welded or threadedl to the outer sheet at the hole through which the bolt extends.
In each case that opening through the sheet is hermetically sealed. In the case Where the bolt head rests in a concavity in the sheet itself, that opening is closed-by al simple capy which is completely welded to the sheet around the opening in which-the bolt head is seated. In the case of the sleeve that is welded or threaded to the sheet, the top of the sleeve, which is essentially a cup-shaped supporting element for the bolt head, is suitably closed, either by a threaded plug, or by a cover that is welded to the t'op 'of the sleeve.
correspondingly threaded hole in theiire. box. That end of the bolt in each case is stationary. In order further to anchor that end of 'the bolt at the re sheet, vthe end of the bolt is peenedover or riveted where it extends slightly through the re sheet. t
The rules of the Interstate Commerce Commission require locomotive boilers to be tested once every year. Thatv test is .performed by raising steam in the boiler, vwhile it isl otherwise lled with water, thereby to subject the boiler and the bolts to hydro-static pressure. When solid flexible bolts are used as staybolts to hold the two sheets, the rules of the Interstate Commerce Commission requireremoval of all of the caps covering the exible bolts, and a subsequent hammertesting of all of the heads of those solid staybolts every two years.
When -exible tell-tale bolts having tell-tale holes are in service, the bolts are tested every year at the` time that thel hydro-staticV test is applied tothe locomotive boilers. If any of the tell-tale flexible bolts are fractured, water will be forced throughv those fractures during the hydro-static test, and into the rtell-tale holes. That water will then come out through the end of the tell-tale hole at the re sheet,r and will indicate that the bolt is defective.
During operation, the hollow passages in these tell-tale flexible bolts frequently accumulate a great deal of dirt and rust or scale. In order therefore to procure aproper test of the bolts, the Interstate Commerce Commission rules require that the tell-tale holes be cleaned out so there 'v will be no impediment to the free flowof any This operation of cleaning out each one of theV bolts is an expensive one. Moreover, it has frequently resulted in destroying the -operativeness of a bolt, because the drilling or reaming tool used to clean out the bolt was sometimes operated deeper into vthe'head of the'bolt than th original passage, and thereby lengthened the passage more than was necessary.'I .i If, by chance, successive cleaning operations: in? any particular bolt were attended by Iexcessive drilling', the lpassage would be open clear out through the head of the bolt and the bolt "was thenrendered unfit for service, and'therefore had to be removed, even though the' bolt shank or body was otherwise sound.'
The innerend of the bolt is threaded into a 55 One of the primary objects of my invention,
therefore, is to provide atesting system that will simplify and make certainthe testing operation and thus reduce the extremely high costs and inefectiveness of the present testing method.
Another object of my'inventionis to provide a bolt and a testing system that will not only obviate the necessity for cleaning out the tell-tale hole, but that will utilize, and take advantage of any rust or scale that may be formed in a telltale hole.byV water entering througha fracture in the bolt body'.
Another objectA of my invention is to'provide a staybolt as a unit combination so that it may be tested while in position and in service, to deter-v mine whether the boltis sound and may there? fore be continued in service, or whether it fractured and must be removed and replaced.
Another object of my invention is to provide a bolt embodying a testingelement as a permanentv part thereof, so that the bolt may be easily and readily tested whilevin position and inservice.
Another object of my invention is to provide a flexible staybolt having an axial tell-tale hole, extending, from the riveted end into, butv not through, the head at the Kother end, with an element in the tell-tale hole, to serve as an electrode for an external testing circuit, while the boltA is in position and in service..
l A further object of my invention, therefore, is
Ato provide a new bolt -constructiorrin which a testing electrode is permanently sealedin the central passage. ofy the bolt', referred to as the telltale hole, and in electrically insulating this electrodefrom the bolt, while permitting the external end of the electrode at the riveted end of the bolt tov be so located as to permit an electrical connection vto be. made thereto by atesting instrument.
Another object of my invention, is to provide a new testingelectrode, .asa new article of manu. facture, that may be applied to the many' flexible tell-tale boltsnow in service, to take advantage of the-benefits of my presenttesting system as d'escribedherein,v and thereby reduce the cost of supervising and testingy those many' bolts now in service in the Nations locomotives.
My invention may also be applied to rigid bolts, which are xedlysecured at both ends to the two sheets. In that case, a tell-tale holemay beA provided at one end only, orat vboth ends but not clear through, orI it may extendcl-ear through the bolt. Q
The manner in which the bolt disposed in' its assemblage with its testing electrode'is illustrated in the accompanying drawing in which, l
Figure 1 is a vertical sectional view through a portion of two sheets of a locomotive re-box held by a rigid bolt; v l
Figure 2 is a similar view showing the two sheets held byV a flexible bolty with: a' cap: over the bolt head;
Figure 3i is'. a similar view of a flexible bolt em- I ploying a. sleeve for bolt'head; l
Figure 4 is; al view' similar to Figurey 2, with an insulated electrode disposed the: bolt in aclto. form the plug.;
Figure 6 is an end elevational view of the riveted end of the bolt in Figure 5, showing how the anchoring washer is spot-welded on the bolt;
Figure '7 is a View similar to Figure 5, except that the bolt is provided with a recess to interlock with the plug .material as formed, or With a bonding material on a'preformed plug;
Figure 8 is a side elevational view of an electrode of one form embodying my invention;
Figure 8d is an enlarged view of a .portion of an electrode *of anotherwform embodying my invention;
`Figure 9 is a view of the riveted end of a bolt, whetherrig'id or exible, provided with a short interlocking recess to receive some material of the molded plug or some of the bonding cement on a preformed plug;
Figure-l0.y isa. View of the bolt in Figure 9, after thevapplication of theplug, or of the material that forms the plug;
Figure .ll is avie-w similar to Figure 1.0 with a small cup to limit. the .amount'of plastic,v material that may be Vinserted. in the tell-tale hole Figurev 12 isA a view, similar tov Figure Lotarigid bolt provided with a testing electrode at each end of the bolt; and f v Figurev 13 is-v a view of therivetedend of` a bolt in which a removable plug is provided to entirely enclose the outer end. ofthe. testing electrode..
As shown in Figure 2, two sheets` IB and.y I I of a boiler surrounding a locomotive re box,lare
arranged' to be held togetherby a pluralityoi spaced staybolts I2 which are .usually threaded into the fire-box sheet II- and;d`sposed for flexf ible movement in the outer sheet III.
yThe bolt IZVisprovidedwith a shank. or body I3', threaded at one '.end. I4', and. provided with an enlarged head. I5. at vthe other end. The bolt is further providedwitha centralaxial passage, or tell-tale hole I5, extending throughout. the length of the b0dy,or shank, ofthe bolt, and
v slightly into the enlarged portion or head I5 of the bolt. The ypurpose of this tell-tale hole I6 is to enable a `iracttue in thebolt body to be readily indicated and detected by the presence and observation -of. any Water that might. seep through the fracture inthe bolt body, from the water chamberlbetwe'en sheets. .Ill and II, int'o f and. through ythe tell-tale hol'e IB, and then out through the end of the tell-tal'ehole. l
- The head of` the bolt I5 rests in an opening I1 in the outer sheet I0, that is4 usually of partspherical shape to receive thev enlarged portion or head II5 which is also preferably shaped on its under surfaceV to be part-spherical, to permit maximum freedom of adjustability. The head I5 .is covered by a cap I8 that is ywelded around its contacting edge to the ,sheetv I0, to provide a, complete closure and hermetic seal around the head I5 andthe opening I1, in the outer sheet I0. As explained above, the rules of the Interstate Commerce Commission require each boiler to be tested once 'each year' while in service. vvAtthat time, all flexible tell-tale staybolts arev also tested. This test is 'performed by heating the Water in the boiler compartment contained' between the two sheets I0 and II to Y'a pressure about twentyrive per cent above normal operating pressure.
If `any bolt is.` fractured, the hydrostatic pressure should forcecthewater to seep through from the waterchamber or space 2i!V through the fracture and into the tell-tale hole of the bolt.y In order to permit such seepage to flow freely to the open endof the tell-tale hole vfrom which theA tured bolt still has its outer structure that .mayf-v give way during service and establish a dangerousr usual plug 2| i's removed during this test, it is also a rule, of the Interstate Commerce Commission, that all tell-tale holes I6 must be clean and free of any obstruction throughout'their entire length. It is therefore customary, before testing each locomotives water chamber, to clean out all of the tell-tale holes of the flexible bolts, to insure free passage for any water seepage.
It is necessary to clean out those tell-tale holes for'the test, since, in the case of a broken bolt, any water that might have seeped through a fracture in the bolt, during operation, might also have caused sufficient rust to close the tell-tale hole against further free flow of water that would.
otherwise still seep through the fracture. When each tell-tale hole is reamed out and cleaned throughout its entire length, the subsequent hydrostatic pressure that is 'generated during the test should -be suflicient to cause the water to seep through the fracture into the tell-tale opening and then flow freely'out of the hole into the fire-box, at the inner end of the bolt, to indicate thefractured condition of that bolt. Although this cleaning-out operation may be necessary for the bolts, to insure free passage for any water that ight be forced through a fracture in the bolt, so that such fractured condition' can be indicated, such cleaning operation with its incidental cost is but one undesirable thing that my invention is intended to eliminate. ifs
Another undesirable condition that may =be even more disadvantageous, and even possibly harmful, under some instances, is the possibility of an accumulation of a hard sediment on 'the outside peripheral surface of a bolt and adjacent to the fracture, in such mannerv as to completely seal the fracture against water seepage, and thereby to indicate a false condition of soundness in the fractured bolt, by preventing seepage during the hydrostatic test. It is to prevent such a false indication of soundness in a defective bolt that is another of the objects of my present "invention. Thus, a defective condition dueA to a fracture'in a bolt may first permit sufficient preliminary seepage of water through the fracture to rust operating condition. f
This condition of the fracture in the bolt shank, f
. or body, is indicated in Figure 3 in Whichthe body of the bolt I2 has a fracture 23 whose origin 1 24 on the outer surface of the bolt is completely covered and sealed by a hardened caked mass 25 of the mineral or salt ingredients of the water usually supplied to the locomotive boiler. This mass 25 takes theform of a hard and solid rock formation, which adheres closely to the .outer surface of the bolt, and, in many instances, is
sufficiently adherent to establish a complete seal that would prevent seepage of water to the fracture 24. y 1
Thus, while the tests heretofore employed as required by the Interstate Commerce Commisi sion rules have provided a safety measure, `that test did not necessarily completely indicate the defective condition of bolts that might actually have been in fractured condition during the test period.
The rusty condition in the tell-tale hole, that' might have been caused by seepage through the fracture, and that should be available as tangible l evidence `of the defective condition of the bolt,
is thus destroyed without serving any useful purl the necessity that heretofore obtained, of clear-l ing out the tell-tale hole for testing.
In order to detecta first break down condition that results from a fracture and the consequent seepage of water through the fracture into the tell-tale hole, I propose to insert a metallic con' ductor 21 as an electrode into the tell-'tale hole and seal it in that position in the tell-tale hole as a permanent electrode, initially completely electrically insulated from the bolt itself.
the inside of the tell-tale hole of the boltfand the rust would then act as a plug or barrier against further seepage during normal operation,
although the bolt was unsound. Thereafter, during the time interval between the occurrence of the fracture and the time of testing, suicient ,sediment from the water in the boiler might accumulate on the outside surface ofthe bolt, at, and around, the fracture, to prevent further seepage.
Consequently, even though the tell-tale hole would be cleaned out prior to the hydrostatic test, the sediment on the outside of thebolt might be suiiicient in quantity to prevent any seepage through the fracture during the test. Thus, the actual defective conditionof the bolt would be hidden, and the dangerous condition in the defective bolt would continue to exist for possibly another year until the subsequent test.
By means of my invention, however, when afractured condition occurs, the first results of the water seepage into thetell-tale hole are utilized to establish an electric circuitl condition which rcan then be tested and detected without requir ing the cleaning out of the tell-tale hole. At'the same time, the danger is obviated, of the possi` bility that the fracture may be externally covered sufficiently to prevent seepage, and a sound condition still indicated, even though the frac As shown in Figure 8, the electrode consists of an electrical conductorV which is shown as a wire 28, covered by spaced insulating beads 29.r The electrodeis of any heat-resisting metal, such as,
for example, Nichrome lhea-ting element wire.'
The electrode should be self-sustaining, but small enough to fit into the tell-tale hole when covered S by the beads 29. The beads 29 are of any suitable material which will space and insulate the conductor 28 from the side walls of the tell-talehole, and those beads may be mlade of clay or of other equivalent refractory insulating material..
The sections of the conductor 28A between the beads are not insulated, but are left to be enby an insulating bead to prevent electrical con' tact with the body of the bolt at the headed end f of the tell-tale-hole. The outer end of the electrode 28 is preferably anchored is provided at the outer end of the electrode;A
to .serve as a terminal to permit the connection of external testing circuit to the'electrode, toV determine whether the insulated condition be-.'
and supported 3 Y ment.
tween .theelect'rode' and' theboltfha'sf beeii'broken downand changed 'to a conducting conditiona- The plug 30 may be made o.t:ajrefractoryzma terialftobe shapedI asindicated as atruncated cone. Y Inv that case, theplugi iszshaped ofproper,
size to fit into the conicalsopeniiig 22` that is usua'lly formedv at the outer vend of the tell-tale hole at the fire-box or .riveted end of the bolt.:
That conicall opening is usually formed at 'the' endv .of the tell-tale hole when that end of the.. boltis' peened-over, as indicated inseveral of the drawings.
In order to hold the plug 30 of .the velectrode in position at the .end of the bolt,"=I may 'resort tothe arrangement shown in Figure 5, accord` ing to Which an annular Washer 35 is spot-Welded,
or tacked to the endsurfa'ce of the vbolt on the outside of the plug, after the electrode and the'l plughave been placed in position. Theiwasher 3.5 is arranged to be concentrically located so that' the terminal 32 of .the electrode will be' spaced and insulated from the Washer,.and avail-z able for contactthrough the opening inthe washer.' v
-In Figure?, I have shoWnanotherarrange-j ment, whereby the plugl for the ele'ctrodemay'v be.' anchored in position. With -this arrangement, after the end of the bolt has -beeny peenedover.- as atl 3B, and the. conical' end of vthe operiing 22 formed at the end of the bolt, anaddi` tional annular groove ,31 is formed 'inthe bolt near the outer end of thetell-tale hole'. The. plug 30 may then be formed of a moldable puttylke fire-resisting material andpressed `into po-V sition so that someofthe' plug material will en.v ter the groove 31, and there harden and'become interlockingly anchored; or Aa vportion of selfhardening bonding or cementing materialmay be added to the outer peripheral surface of the plug .to bepressed into the groove 31 when the plug is forcedinto position, so that the bonding', material, upon hardening, Will form ay key' to lock:
the plug into position against casual displacee completely circular. Any recess fto receive the bonding or plug material Will suice.
When the electrode is to lne-'positioned in', an assembled with, the bolt, after the bolt has been' placed in position, the electrode isI out to proper size to fit into the tell-tale hola-so' that the electrode vwill occupy substantiallyv the entire lengthofthe tell-tale hole, and insulated from the. headed end, when the plug is pressed into its tightest possibleposition to whichit :is to beanchored. The plug is `then -anchored either'A by' some such mechanical arrangement as is 'shown'- in Figure '1, or by a self-interlocking arrange-y ment -such as sh'own in Figure 6.v l
When this electrode is disposed in the bolt,v it. may be left there for the life of the bolt .Thereafter, it is unnecessary tovremovethe electrode to clean out the tellftale hole,l as is the,v
present practice in. conformity .Withlnterstate Commerce Commission rules. ".Il'lus,4 a great..sav...
ing may be madeby eliminatingl .andobvi'ating the necessity'for such periodiccleaning.out of,
theV tell-tale holes. A
A further advantagefjof the electrode o f this type, that is permanently disposed in the telltale hole, is that immediatelyj uponl the occur-l rence of a fracture and the' ensuing 'seepage'o'f i Water through the `fracture into the 'tell-tale' hole, the insulated .'conditionbetweenthe elec trode and the bolt is disturbedar'id` it isvchanged. to an electrically. conducting .;condition;;due to.;
Thegroove 31 need'not, ofcourse, be.
presence of "Water the `first instance', or
dueto 'the presence of :any vrustfthat may .be .gen-g erated by-the water :in `the ltell-tale hole.. In eithercase', the Waterorthe rustwill provide aiconduct'or between the electrode'andv the bolt. which: will set up an electric short-circuit that able casing 44.. The electrodes 4i) and 4I are connected in series with the 'battery 42 and the-lamp 43, 'so that when the circuitl between 40 and 4l is closed, the lamp will be lightedv by the Voltage ofthe battery to indicate a closed circuit. Thus, when the tester is applied to a bolt, the electrode llt' engages theterminal 32 of the bolt electr-ode,
and-is then turned throughia slight angle to permit the scratcher electrode 4'! to scratch the sur--y face of the peened-over edge'of the bolt. If'the tested bolt is sound, the main electrode 21 will be insulated from the bolt, ancthe circuit beftween electrodes 40 and 4l of the tester Will not be electrically completed, and the lamp willV not light. j Howeven'if the bolt is defective because of the presence of a fracture, suiicient to have pennittedwater toseep through and establish electrical contact between the/electrode 21 and the bolt, the circuit-Will becompleted between.
the electrodes dll and 4l of the tester by the Water orby the rust between the electrode and the boli;l body, and the lamp 43 will' be energized to light andl indicate a closed circuit and therefore a defective bolt.
As .I have already described above, the inner end -of the electrode should be suitably covered inorder'to be insulated against electrical contact v with the head of the ibo-1t. InFigure 8,. I have illustrated the electrode insulated by means oi one of the long cylindrical beads by adding a cement or bonding material to that bead, kor to any-of the beads on the body of the electrode. I-he electrode may be anchored in position upon `the drying of the bead and its consequent adherence to the engaged portion of the Wall of thetell-tale hole. ,Thus the electrode may be anchored by suitable anchoring means other than .the outside :plug orl washer at the riveted end of the bolt.-
Incidentally, although specification and the claims, that Word does not necessarily limit the invention to a single solid pre-formed closure for the riveted end of the tell-tale hole. The Word plug is intended to' be broad enough to include any type of a closure' for the tell-tale hole with orv Without additionalmaterial for closing oft -or sea-ling'the end of the tell-tale. hole at the rivetedI end ofthe bolt. Thev closure materialmay be integral vWith the elec-l4 trode before gitis inserted in the .tell-tale hole, or, vas described above,fis pressed into' place as a plastic material, Which hardens and anchors itself'- upon drying. v To form theplug, or the plug'ma.v teriaL. I -have utilized a high-temperature-resist' antvcement. A plug form'ed'of 'Such cement, `'or l anchored bysuch cement, resists the temper'al' tures of the'ames inthe re box, and also forms l a Water-'proof seal atl the riveted end of the telltale'hole.
1n-Figure' 8,-1 have-:shown the beads 'hem in" v have used the Word' I plugv for the-sake of simplicity, throughout the apagan position, against axial sliding'by lugs -3'5pinch'ed or crimped on the wire at yboth sidesv of the beads. In Figure 8a, the wire section is slightly reduced at zones 36, and a mass 31 of refractory material, such as the above-mentioned cement, is molded on the wire 28 at those zones. i YUpon drying,
-those masses 31 become anchored in position. I
In Figure 9, I have shown the electrode in position where a plugr or closure is to be formed from plastic material such as the lire-resistant refractory cement. A short recess is formed in the bolt near the end of the tell-tale hole to receive a small amount of the plastic material, which will form a key upon hardening, to anchor the closure against casual displacement.
In Figure 10, the plastic material is shown in position with a tip of the electrode extending beyondv a small recess in the plug material. Y
In Figure 11, I have illustrated an arrangement in which a small cup 50 is employed to limit the amount of plastic material that may be pressed into the end opening to prevent the pressure of that material, when inserted, from distorting the electrode 21.
In Figure 13, I have shown an arrangement whereby the plug may be preformed to serve as a complete closure for the end of the bolt without initially touching the electrode. In this case, the closure 4l is provided with an internal depression 52 to encircle, but not touch, the outer end of the electrode 21.
In Figure 1, I have 'shown a rigid bolt illustrated with two short tell-tale holes extending a short distance into each end of the bolt to a region beyond the thickness of the sheet. According to present practice, the tell-tale opening is provided in only one end of the bolt, at the lire sheet end. I contemplate, however, that the advantages of the present electrode, and the method of testing possible therewith, will make it advantageous to provide a tell-tale bolt from each end of the bolt, as in Figure 1, or even extending all the way through the bolt. When the hole extends only a part distance into the body or shank of the bolt, an electrode may be inserted at each end as in Figure 12. If the tell-tale hole is provided extendingthrough the entire length of the rigid bolt, an electrode may be disposed to extend through the entire bolt, so a terminal of the electrode may be available for testing purposes at either end of the bolt. Each end of the tell-tale hole may then be sealed by any form of plug or closure shown in the various modiiications illustrated.
My invention is thus applicable to all types of stay-bolts, whether of the rigid type or of the ilexible type. With the testing electrode as I have described herein, it becomes unnecessary to clean out the tell-tale hole for testing purposes. In fact, the rust that results from water seepage through a fracture in the bolt Ibecomes the medium whereby the insulated condition of the electrode is disturbed, so that a test of that condition of the electrode may be utilized to provide an immediate indication of the condition of the bolt.
My invention is not necessarily limited to any of the detailed arrangements or construction that have been shown, since they may be variously modied vwithout departing from the spirit or scope of the invention as set forth in any of the appended claims.
I claim as my invention:
l. A new article of manufacture, for use with flexible staybolts having central axial tell-tale holes, consisting of afmetallic Aconductor having spaced-insulating means integrally secured thereon, said means having anexternal dimension small enough to permit the wire and insulating means to be inserted into the hole, with the inner end of the wire insulated from the ,corresponding end ofthe staybolt, and a closureon one end of .the Ametal conductor. to anchorthe metal con'- ductor from the open end of the bolt hole.
z'. A flexible s'taybolt provided with a concentric axial tell-tale hole, and having a metallic electrode insulatingly supported in the full length oi' the tell-tale hole by spaced beads on and secured to the electrode, 'with the inner end of-the electrode insulated from the corresponding end of the staybolt, the electrode being anchored at the open end of the hole by an insulating closure through which a portion oI' the electrode extends to serve as a terminal ior an external testing circuit.
43. The combination lwith a exible bolt having a tell-tale hole, of a metal electrode disposed in the tell-tale hole and insulated from the bolt body and head by spaced means along and around the electrode, an insulating closure tting into the outer end of the tell-tale hole to close the hole and supporting the outer end of the electrode with a. short portion of the electrode extending beyond the closure to serve as a terminal for an external testing circuit, and means integral Iwith the bolt for holding the closure in position.
4. The combination with a flexible bolt having a tell-tale hole, of a metal electrode disposed in the tell-tale hole and insulated from the bolt body and head by spaced means along and around the electrode, an insulating closure fitting into the outer end of the hole to close the hole and supporting the outer end of the electrode in a manner to permit the latter to serve as a terminal for an external testing circuit, and a recess near the end of the bolt for receiving and anchoring the closure in position.
5. A staybolt comprising a flexible bolt having a tell-tale hole, a metal electrode in the length of the hole and spaced and insulatingly supported from the wall and head end of the tell-tale hole by spaced insulators on the electrode that establish small spaces to hold any water that might enter the hole through a fracture in the bolt body, a closure to close the open end of the hole and to support the outer end of the electrode, in a manner that will provide access to the terminal of the electrode by a testing instrument, and means to secure the closure against casual displacement.
6. A ilexible staybolt assemblage, comprising the combination with two spaced sheets; of` a bolt with an enlarged head anchored in a concavity in one sheet and threadedly anchored in and riveted to the other sheet; a cap covering the enlarged head and hermetically sealed to the sheet to enclose the head 4and the concavity; a tell-tale hole in the bolt extending from the riveted end through the bolt shank and into, but..
.eleetrede Sveeed ,from theibolt sumoiently to en- @ble eleetreel eontaet to lbe made thereto for .an external testing circuit; and e Water-proof ,and ire-proof eloeure at the end o f the telletale 5 hole, Ier sealing the hole algainst'foreign matter exgept auch as might enter through a. fracture in the bolt along the length of the telletale hole.
JOI-IN ROGERS FLANNERY.