_-----------O&.A------------Bedllner 'Charts

and Gear InspectionQ&A is your interactive gear forum.Send us your gear design, manufactur-ing, inspection or other fiefated ques-tions, and we '/I put them before ourpanel of experts. Questions may bemailed to Gear Technology, P.O. Box.1426,Elk Grove Village, Ii 60009,USA,faxed to {847} 43Ni61S or sent e/ectTon-ically to people@geartechnology.com.An expanded version of ll&A is alsoavailable at www.geartechnology.com.Hundreds of questions have alreadybeen posted and answered. Visitors are'welcome to post their own answers.

Doub!e R,nk Gill· TUllng

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Me-aslJre-s V'iinltionl in e.nter Distance MiUIJ:t1i' Rbtlltu)rllIl Motion.

Fig•.11 - Types lit com,I'0sita gear iinspectioll' ..

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Robed E. Sm'ithis the principal in R.E. Smilh &

Co., gear consultants ofRoehester; NY. and one of GearTechnology's technical editors.HI! ha oller 50 years of experi-

tinct! in gllaring and is Ihl! authorof numerous {JtIpersandanlcles.He: is also very active in AGMA

standards development.

2.4 GEAR TECHNOLOGY

Question submitted byRamiro C. SalinasCo.rpus Christi Army DepotCorpus Christi, TX

Q:What are redliner charts.and whostill does redliner charts?

Answer submitted by:Robert E. SmithR.E. Smith & Co.

A: For marty years, the terms "redliner" and "red line charts" have beenused by the Fellows Corporation in rela-lion to the:ir line of double flallk com-posite testers, For example, they madeIlle No.4 Fellows Fim~-Pllch Red Linerand the No. 12RL Red Liner. Doubleflank composite gear inspeetion isshown chematically in Figure I. Theseinstruments were in such common usethai. the term "red liner" became syn-onymous, w.ith double flank compositeinspection,

The tenn "red line charts" apparentlycame from the facl that early recordersused pens that wrote with red ink. Thesewere a constant maintenance problem,diue to dogging and spatter. Laterrecorder u ed thermal writing pens andpaper, thermal array printers. or evenprinter attached to PC computers.Double flank composite testers are madeby many different. companies and can usea variety of writing methods that do notproduce a "red line" on the chart.

To compound the confusion evenmore, the 'term "compo ite' inspectionhas been taken to mean double flankcomposite inspection beeau e it was insuch common use. As can be een inFigure I, there is another type of com-posite inspect jon, called single flankcomposite, tilat can be used. Today, bothtype appear in gear quality standardssuch as AGMA and ISO.

Double and single Hartle compositetesting results in charts such as thaishown in Figure 2. However, they meancompletely different things, As Figure Ibows, double flank composite test

measure center distance variation as thegears mil Ihrougb light mesh. Singleflank composite testing, however, mea-sures rotational motion variation, as thegears roll thrilugh mesh at standard cen-ter distance. with backlash.

One can see that the continued use ofthe term "red liine chart." is not a verygood idea. The terms "double flank com-posite chart" or "single flank compositechart" would be more accurate and pre-vem confusion as to what the data mean .

The 0000<1 part of the question askswho still doea redfiaer 'charts. Doubleflank composite inspection (to lise theproper terminology) is very common inhigh volume applications, such as auto-motiverransrnission gears and fine pitchgearing made by cutting, molding, andpowder metal processes. It is a good con-trol of functional tooth thickness (size)and runout under certain 'conditions.

Double flank: ccmposite inspectionCart. be a good C0l11)101 of runout beforeany sub equent fini hing operations suchas shaving and some grinding operation .However, after finishing, the chart maysbowvery little runout, but the parts callstill have a large accumulated pitch errorthat bas all the ill effects of runout sucha positional error or nonuniform onceper revolution velocity. This is some-times called "hidden runout." Singleflank: composite inspection win findthese problems. See AGMA Tech-nicalPaper 95FTM~, Detection of HiddenRunout, by R.E. Smith. et al. 0

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