r- _— - . . . ——

I

., ‘‘ ,:4 S :jqll~l:J ;: ,, .,, . ..A ‘“i’194.> ..—=-. . .

NATIONAL ADVISORY COMMITTEE FOR AERONAUTIC

wAmIm Iuwom”ORIGINALLY ISSUED

April 1942 asConfidential Bulletin

CONSTRUCTION OF FINNED ALUMINUM MUFFS FOR

AIRCRAFT-ENGINE CYLINDER BARRELS

By Langley Memorial Aeronautical Laboratory

Aircraft Engine Research Laborato~Cleveland, Ohio

.

NACA WARTIME REPORTS are reprints of papers originally issued to prcvide rapid distribution ofadvance research res~ts to an authorized group requiring them for the war effort. They were pre-viously held under a security status but are now unclassified. Some of these reports were not tech-nkally edited. All have been reproduced without change in order to expedite general distribution.

3 1176013s47970.—. . —___ .. —- .—.

IIATIDSTA3 ADVISORY 00M1(IT~EZ F03 ~OMAU!!!IOS

00NBIDE17TIAL BULLIWIX

‘ 00NSTRU”OTIOE 0~ iIl!TliEIDALUMINUM litl~l%POE

AIEOEA~%-UlWIl13 OYLXMDm BARRrnLS

Langley Memortal Aeronautical Laboratory

Summary.- This report describe~ the material, cuttlng-tool development, and maehlning procedure used in oon-etructing an air-~ooled oyllnder barrel having a ooolingmuff with 2-inch fins epaeed 1/8 inoh. Details of twotypes of thread form utaed for the barrel to head assemblywith the ooollng muff are aleo presented,

Introduotlon.- In the aonstruotion of aluminum-finnedairoraft-engine cylinder barrels, the MACA has used analuminum muff slipped over and shrunk to the barrel be-fore aaeemBly with the cylinder head. This prooedure 1sthe ourrent Pratt & Whitney practiae on the E-2800 engine.It is of historical interes% to note that the originalLawrence air-cooled engine utaed a form of aluminum cool-ing muff. The cooling muff of the Lawrence engine was anextension of the aluminum-alloy cylinder head into whiohwas shrunk a steel liner.

Cylinder-barrel muff.- The oylinder-barrel muff ismachined from an aluminum-alloy forging. The forging mayeither be of the pieroed or solid type. One muff machinedfrom an aluminum-alloy casting was used, but experienceindloates that the forging has a higher thermal oonduo-tivity and considerably better physioal oharacterlstios.The forged material used was 17S-T, a dural alloy. Thehardness of this material is of considerable importanceIn the successful machining of the fins. It was foundthat machinability improved “with hardness although noattempt was Wade to determine the limits on either endof the hardness range. In general, it may be stated thatwhen the hardness was less than Eookwell 90-~ the forging

2 . .. .. . .

vaa too soft to machine. Good machinability was obtainedup to the maximum hardness triad, Rookwell 1OO-B. Thehardness of the forging was tested before machining andwhen it was fouad to be below Rockwell 90+7 the following -heat treatment wae used: The forging was heated to 930° ~and held for approximately 1 hour; then the. hot forgingwae plunged Into oold water. The quantity “of water waesuch that Its temperature did not rice above 110° 3’.

Ae dural is an age-hardening allo7, it oannot bemaohined for several daye after the heat treatment. Im-:m~dfately after heat treating it was softer than. before.treating, but the subsequent age hardening increased its

initial hardness. The muff wata desigued to have fins .2inahes”deep and 0.050 inch thick with a spacing of 0.125ino.h (fig. 1). .. .

Cutting tools--- ~he most difficult part of the proj-ect was the development of cuttirig tools for machiningfins of this depth and epaoing. The thickness of the .gang outter:e blades limited the desired minimum ”spacebcztween fins; however, the bladee ootild be epaced.to &ive

, ar.y decired fin thickness. Six blades were us”ed in thecutter elthough poeslbly more could be ueed. Two gang .cuttere were ueed; ‘the firet get of cutters ”wae used ”fora roughing operatt.on “and the eecond eet .wae used for thefinishing “operation.. The blades were made fromB. & S. “ .ground stock; a sketch of the form round bcist is shownin figure 2. The cnly difference in the roughing andfinishing tcol wae a few thoueauilths inch in the bladewidth which allowed the chips to oome out. of the work “more, freely. . . ..

The procedure. for machining the fins after the inl+tia.l”rough turning. operation was to take the firet out “‘with the rcughing tool- t~ a depth of 1/2 inoh. The oroughing tool was then used alternately with the flnish-Ing tool making outsmof equal depth with eaoh tool until”the desired depth of the fins was obtained. A aingle-blade tool was ueed for the ra~ius at the root of thefins. (See fig. 3 for,photogr~ph Of finished muff.)After the fins we~e out, the muff vae finished bcred togive the desired shrink fit on the cylinder barrel. Theuuff was heated to abcut 450° I’ for this assembly. Thesteel barrel (fig. 4) was machined tc a true cylindricalform leaving approximately 0.135 inch wall thiokness for .a oylinder of 63i~ inohes bore. The finieh IS comparableto that of the best turned finish found in commercialpraotlce.

-.

3

ghread forms.~ In .the.firet few oylinders assembledby the NACA the ‘iAerofithread was used (fig. 6). Thistype of assembly ls.identioa~ with that used by the Pratt& Whttne-y Company, except that t~ey use an e-pltoh thread;whereas the MACA used. a 12-p~toh thread. The reason forthe change in thread plteh.vaa tomgi~e a shallower threadIn”the steel barrel and thereby. increase the strength ofthe barrel at this point. . . “

The ‘Aero~ type of thrqad as”applied to oylindere isa fQrmed wire of bronso ~r steel wrapped into suitablespiral groovee of the deeired pitch maohlned on the bar- - “rel. The upper end of the fqrmed wire is peened into a@mall hole in the top of the barrel;. the trailing end lefree to oreep during assembly. Ustng an 8-pitch threadit may be possible to make the aasembly with the formed . “wire held to the barrel by sweating With soft solder.Both peening and sweating were used for the 12-pltah.thread.

. .Later ~~CA oylinder “assemblies have been made

a thread oonstruotion of MA5A Lesign. This deBigna sptral groove on the “barrel stmilar to that Ut3edthe ‘AeroU thread dealgn. However, no formgd-wireis uBed. That part of the thread corresponding torounded part of the formed wire of the ‘Aero” typeis out dl.reatly in the aluminum head with a formed

usingu6eeininsertthethreadtool.

The detailB of this thrpad oonatruction are BhOVn in fig-ure 6. Several GylizIderB uslngmthis oonetruotion havebeen power teBted up to 1500 pounde per Bquare inohoylinder preeeure with no elgne of failure.

The objeot of the MA(IA thread design was to obtaina eimple thread eaey to aeeemble.

ShdJuLam - With either thread form the oylinderhead Ie heated to approximately 650° E and upon removalfrom the oven ie quiokiy sorewsd onto the barrel olamP-Ing the muff between the head and the ehoulder whloh waeprovided on the barrel. The bend has a ehr5nk fit on thebarrel of 0.019 inoh. Thle ehrink ohokeB the bore of thebarrel at the top of the oyllnder by about Q.016 Inoh.After aeeembly the hold-down Btud holoe are drilled inthe oyllnder flange in their proper relation to the head.

In the llAOA aetaemblies, the muff $B designed to havean 0.008-inch ehrink fit on tbe barrel. The effeot ofthie ehripk.on the barrel bore eeeme to depend on a number

4

of factors which have not yet been segregated. In someassemblies, ae little ae 0.00& to 0.003-lnoh reductionIS obtained in the nominal bore size beoause of theshrinking on of the muff. In other aoeemblies, as highas 0.006- to 0.008-inoh reduotion has been obtained. Ifthe reduat~on In bore else is from 0.002 to 0.003 Inoh,only light honing IS required to plaoe the oyllnder InmerViOOm If the reduction in bore Is larger than 0.002to 0.003 Inoh, It should be honed to the nominal sise.Some undermize im permitted with the oyllnder cold sothat under operating eonditiotne a true bore will be ob-tained.

,

General remarks.- Buokling of the fine on the muffimmediately after maohining may be oorrected by insertingsteel spaoers of the oorreot thiokneee between the fiuoand heating the assembly to 800° F and allowlng to 0001E1OW179 Staggered notohlng of extremely wide fins 1ssuggested as a means of preventing buckling in servioe.I’or equivalent weight of fin material, the oooling usingthe aluminum muff is approximately twioe that for steelftns turned direetly on the barrel. This basis of com-parison only holds when optimum fin dlmensione are usedoa both aluminum muff and eteel barrel.

Langley Memorial Aeronautical Laboratory,Uat$onal Advisory Oommittee for Aeronautlos,

Langley Field, Va.

.

,

to.375-Q10.33/ QIoav @_/0076 Q9.948 QS?w Q969+ Q23ZLQ-4?4EL”LMLL!2*E

8= DR

fM%2-8.s97 gaA-

p#-U , [

; 5 “D— 1 1 r 7

k- I qTOLERANCES ON ~—~.m $.-5 ff~ FIMWSM?OTH 4THESE DIMENSIONS

* . ot528 FINS 707@L /M4z DUML

EiQEw SA!4W axwws A ~

FIGURE 1.-72Lr&R6wcS i.010 UiWESS~

J+Taper0.008 inch

.12511

J

per inch depth

l-1/4~t R. Fin dimensions-‘#idth 2tt

Thickness o.050nSpace 0.1251~

~5/8!l

1-3/4’1for blade

minhtun depththickness of l/8~

, v

12°L

Figure 2.- Gang-cutter %lade.

w(E’.(u

Figure 3,- Aluminum muff, 2-inch fins, l/6-inch space between fins.%1

&.CA

‘g

!2

/..— ——-. --- —__ -———--—- -----

~84

— — .

7------ ---

— . .

~.ow, ,-- .y.otw5 n

~D =CTZW- KFf7W ~se&E. Jb”-=r’

USE 7C?2 lWTFI!JtiM%W

FIGURE 4,- A.C.C.1. ENG.

7ZXEIWWEwv F~ CW#i S.17S2. 0/0 UNESS IW7W

IJACA rig. 6

-7

1-1/

Cylinder barrel assembled in head,9M wire insert, 8 pitch, 8 completethreads.(Scale- 5 times size)

ziczxA+----

%%4~.001 Dia.

6.113-6.121 Dia.

6.033-6.037 Dia.

6.005-6.010 Dia.

T.125

I

*

Sk-ink fitdimensionsare .017-.021tight.

.O1>.014R.

f/-B Region of gas tight

fit and three topmost

.>threads on head beforeassembly.(Scale-10 tties size)

Wire and barrel to be tinned forsolderhg top end of insert tobarrel with copper soldering iron.Do not use torch.

Hotes-Unless otherwise specifiedbreakall sharp edges. Knowable variationson finished dimensions, fractions~.010, decimals ~.005, angles=2-1/2°

Copy-Aircmft Screw Products Co.,Inc.Fi=gure5.- Cylinder be.rrelto head connection-8pitch A-T

D-3

J \ ~0G4(/+O&5) ~s

‘L+SECTION SHO W/N6 h!ACA THREAD FORM

I

*FIGURE 6.- SECTKW WOWING CYLINDEH A.5SEMBL Y m

TITLE: Construction of Finned Aluminum Muffs for Aircraft-Engine Cylinder Barrels

AUTHORS): ORIGINATING AGENCY: National Advisory Committee for Aeronautics, Washington, D. C. PUBLISHED BY: (Same)

AYO- 7208 MYKION (None)

PUIUIK1NO AGENCY NO. (None)

DAT!

April'42 Unclass. LANGUAGE

Eng. IUUSTIAT10M

photos, diagrs- ABSTRACT:

Material, cutting-tool development,, and machining procedure used in con- struction of an air-cooled cylinder barrel having a cooling muff are discussed. Muff is machined from aluminum alloy, and forging may be either of pierced or solid type. Cylinder-barrel muff was designed to have fins 2 in. deep and O.050 in. thick with a spacing of 0.125 in. Results show that staggered notch- ing of extremely wide fins Is suggested as a means of preventing buckling. Machinability of muff improved with hardness.

DISTRIBUTION: Request copies of this report only from Originating Agency DIVISION: Power Plants, Reciprocating (8) SECTION: Components (11)

ATI SHEET NO.: R-8-11-18

SUBJECT HEADINGS: Cylinders Cylinders - Design (28483)

Manufacture (28494);

Air Document* Division, IntelliaoMo Doportmont Air Materiel Command

AIR TECHNICAL INDEX Wright- Patterson Air Fore a Beta Dayton, Ohio

~7~r-

TITI& Construction oi Pinned Aluminum Muffs for Aircraft-Engine Cylinder Barrels

AUTHOR : (Nottmoun) OEUS. AGB&Y : Longley Aeronautical Laboratory, Longley Air Force Base, Yo. PUCUSHH) OY : National Advisory Commltteo for Aeronautics, Washington, D. C.

ATI- 8Q879

GlesaL. tt=o. acz^CT CO.

(WlWl)

(Nono)

XMIM* CpnfdM HA Bngllnh - IUBJTOA HCS3

nhnto. drnrcn ADSTBACT:

The material, cutting-tool development, andmaching procedure used In constructing an air-cooled cylinder barrel bavins » cooling muff ulth 2-lnch fins spaced 1/8 Inch Is described. The muff is machined from 178-T aluminum forcing, ohich has proved superior to cast alloys In thermal con- ductivity and machlnabllity. The muff Is shrlnh-fltted to the barrel using a thread. For equiva- lent uoight of fin mntocdal, the cooling using the aluminum muff Is approximately tulco that for steel flno turned dlroctly on the barrel.

DcTTRCUTtOM: BPreciflJU All mmnntn for galon nmnt pa pddronned to: PubUBhliw Atoncr, DJVISJOX': Porar iPlacto, Reciprocating j S£CTK»fc CooUngUf

• - / SlH ATI SHEET KOL: / 7

PHc^Poreatxa Atf Cfcro Ccca, Daycsv Ofclo

SU3JECT KEAKXS5: Cylinders, Pinned - Cooling (28530) Cylinders - Manufacture (28494) Engine Compounds - Metallurgical analysis (32830.23)

IKBIBt !AL

L -

CADO CONTROL NO:

- K'-JtW-OS

US CLASSIFICATION:

3H22- ( W<ii;.o TITLE: <^ot?V.

net,ion of 5'innod Alum xuminmn Muffy for-1 nr£pcr&F!— sSW^. Clg, /fr7A yzti&c^&t £*»

3 AUTHOR(S> PI

5 r

^ine Cylinder Barrela ^g -£•£*<&

•U»k&©jj&}- 3 0RI6

SBrV^e^Winaruil Asronjiutio&l lab., o FOREIGN Tl

Suti|o RrtfirL Cy3iywJ«jc« « tfanul'aoturei Cylind '""" S©s4gsr

r,aai-

Puf^iD.B%; Rations:. Advisory ComroStte Aaronautioa, WaoriingMior). 1? -e^—wsi—6

PUBLISHING NO:

^Ift&L'i TRANSLATED BY L'ATION NO:

PREVIOUSLY CATALOGED AS: