Document aDeEJmed6dp5wZEomX1Qp2RqB

LIA24418 LEAD INDUSTRIES ASSOCIATION 2a MADISON AVINUI a NEW YORK 17, N. Y. Kovenber 21, i960 SUBJECT: REPRIOT3 CCWCCTTOW HEW LEAD BEARDiGS To Hashers of the lead Industries Association: Ve are attaching reprints of tvo recent articles that 4 appeared In the trade press, one In "Materials in Design Engineering* and the other In "Design Kevs." Both deal vlth nev developments in hearings, and both developments Involve the use of lead. In on' Instance litharge and In the other lead povder. These articles appeared as the result : of cooperation between the LXA staff and w. rotors of the respective publications. Additional copies in quantities up to 25 are available free of charge aa long aa our United supply lasts. Very truly yours. KLZ:JBS Act. Secretary "7 > "WJ* LI A2 4A19 lUlMIII- nii ^ >*mi o 0 pjCSIO^ DESIGN IDEAS REPRINT MATERIALS APPLICATIONS Dry Bearings Reduce Helicopter's Rotor Hub Maintenance Victor W. Wtf*cjkf, tMini 140* Brock** (mouni* to Subtle**) Oiliest, lead-" l'cllon" bearings reduce mainte nance in the rotor assembly of a turbinepowered helicopter. These bearing* require no lu brication during the service life of (he hub. The design goal of a maintenance-free rotor hub it complicated by heavy loading of non-ro tating components subjected to vibration, inter mittent motion, weight limitations and corrosive environment!. Normally, articulation uf the ro tor hub is accomplished by meant of anti-lrictiou and; or bron/c bearings, both of which re quire frequent lubrication. The recently avail able otllevs lead Tcllon'* beatings are now used to eliminate the lubiication need of helicopter's rotor damper assembly. Material consists of a mixture of lead powder, tin percent by weight, and TFE. fluorocatUm resin impregnated into a sintered bronre matrix. High structural rigidity is imparted to this com posite by a tin-plated steel backing. A thin sur face layer (O.OOflg imh) of lead-TF E. covers tlte sunned bHi/c suifaic to prostdc material fur the "bedding in" piocess. IV of tl*e>e beatings in the critical damper assembly permits elimina tion of (0 grease fittings which would have re quired daily lubrication. Tailed l>l\ the Ix-arings are markelrd excluvnely in (he I'.S. by Spiul products Dept of Carlnck, Iik .. Camden. N. J. The dry hearings air used in the Navy's I1SS2 (win gas-turbine brli<ojitcr dt\rlojed by Sikorsky Ai'craf* Dlv <4 l'mietI Aircraft Cnrp, Stratford. Conn. MX OI ROTOK ntMPU mukli Im4 u 4 Uf mmtim 4 bl4 T tftlH btMhlAfC >uK local Mr* *4 ***4 q Ui wu* klittiuX mntfn| laX 4 in# A *mk 4 3tt n<L ftrt atimitr. (MipMr and imh rrwX I IIXMK U4 lub^li brMm(i im *o(i cwX<iM. Om bM* 4 <ty mmu h ImI irwJtt abuiin* (no bkUw< Mrll rioalHr t**m i*>4WU*s <Wn* 4tf WartAfi bi< Vn Uk mj t w MiX ( pXwlli* tuet MmT it AnMk m Ntb Aifl *4 bo*i^| to pto**4t Iui4 to#tM* (t Wntn|. Ktokrt iw iu u mh tfUt Vr*4-"Tr<Wo" Wifnof Art MUibo 4opt to bak Reprinted frm 0FS10.N NEWS Vol. IS No, SI IxUwiJr Coverage uf Teckaical Nf ** aad f Agiaeeriag Idea* More tbaa ifl.QOO copies every other Mowdty Ml WICTtlUt HUKnflll, f--it4 W* tUi | imSUt rwgliw*, (M UmiIm tMlwbaurix s m(v xapom *im. ftviaf lM K4I fMWn M m fsoV I>m sun, ImU m ilwM *) witwt. OtSTklHOrtO KVl ItAO t* OUST KISS A**OOI At I0K, r*a UAixaoN av k ic u k . * v o v k if, votnt. -JWj.1.1 11 ) u "i'w j.t*a i ,,* y tyiu N 1697.01 'wvr.y -g-g LIA24420 u."'1 o/jp .- .,0--. s t 1 jO Low Friction Coating Works Best at 600-1200 F Lead monoxide provides high temperature bearing surface 3 A new bearing development stainless steel (types 440C and makes u m of the lubricating prop 304) and to Inconel X. One of the erties of lead monoxide (PbO) to better coatings, combining excel provide a low friction coating lent adherence with low friction which can function from room properties, contain.- abo'Jt 6% sili temperature up to 1250 F. Lead con dioxide and 5% n->n oxide ab monoxide coating* were developed sorbed from the s*etl curing the at the NASA Lewis Research firing operation. Center, Cleveland. The coatings are applied as a Applied like porcelain enamel dry powder or sprayed on aa a Effective lead monoxide coat water slurry, then fired in the ings of aevera) compositions have range 1650 F to 1800 F, Such We successfully applied. In the fired-on film* provide lower fric ra.noer of porcelain enamels, to tion coefficients at temperatures exceeding 600 F than commercial resin-bonded molybdenum disul ; osaS ---------------- ,--------------- j-- ft* *4 **/-* t+M. 1 -------- S-M r+4 e>4w **>f -- 5.. I X 02 V ** (mMSK 0t 4JO fpm _srl - ---------- /-4-hi^jassist fide coatings (see Fig 1). High temperatures help Unlike conventional lubricating systems w hich function best when lew surface temperatures are maintained at the bearing inter * -i - * face, the NASA coatings lubricate O 200 400 SOO 000 COO 1200 best under conditions that tend to promote high bearing surface 1--Efpct e/ <c t yrctwra *w Aeer- temperatures, l.e, high ambient fx# Jv^ftcelbtf preperStM. temperatures and high sliding velocities. At sliding velocities ranging from 2400 to 10,000 fpm (Fig 2) friction coefficients were within the range 0,05 to 0.08 at aQ temperature* studied. Reason for such performance la probably the formation of a glared or vitreous surface promoted by the lead monoxide (n the cone of sliding. Sliding then takes place by plastic or viscous shear rather than by shear along crystal planet. Endurance life and temperature Endurance life of the lead mon oxide coating seems to be sensi tive to temperature, approaching a maximum at 1000 F, then de creasing slightly at 1250 F as shewn in Fig S. Although these coatings were designed to operate in the 600 to 1200 F range, the data show that both life expect ancy and friction coefficient are goed enough in coot operation to recommend them--even when tha bearings must be started or cycled through room temperature 0 200 400 600 000 (000 (200 1400 Tfgeretvrt F 2--r/cf / ttlm# eefeetty #a JwArictig / PtO-SiO, Jttm. I-Kiw (emysm/wee e/eefe Uf* */ Dbfrt^t9tod Ay UAS WMITIUI AMOttAOM tft SUOiSOW AV1NM MW tea ir, MW YOM eeeHsgs, **.>- -fT- .'tm A u^f^nypir N 1697.02