<div>Earl,</div> <div> </div> <div>Good information. However, this is a static test. I think the real failure mode might be fatigue in a dynamic (vibration) environment. This is what usually causes threaded-rod type control horns to fail.</div> <div> </div> <div>Bob R.</div> <div><BR><BR><B><I>Earl Haury <ejhaury@comcast.net></I></B> wrote:</div> <BLOCKQUOTE class=replbq style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #1010ff 2px solid"> <META content="MSHTML 6.00.6000.16527" name=GENERATOR> <STYLE>v\:* { BEHAVIOR: url(#default#VML) } o\:* { BEHAVIOR: url(#default#VML) } w\:* { BEHAVIOR: url(#default#VML) } .shape { BEHAVIOR: url(#default#VML) } </STYLE> <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" /><o:SmartTagType name="PersonName" namespaceuri="urn:schemas-microsoft-com:office:smarttags"></o:SmartTagType> <STYLE> st1\:*{behavior:url(#default#ieooui) } </STYLE> <STYLE> <!-- /* Font
Definitions */ @font-face {font-family:Tahoma; panose-1:2 11 6 4 3 5 4 4 2 4;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {margin:0in; margin-bottom:.0001pt; font-size:12.0pt; font-family:"Times New Roman";} a:link, span.MsoHyperlink {color:blue; text-decoration:underline;} a:visited, span.MsoHyperlinkFollowed {color:blue; text-decoration:underline;} p {mso-margin-top-alt:auto; margin-right:0in; mso-margin-bottom-alt:auto; margin-left:0in; font-size:12.0pt; font-family:"Times New Roman";} span.EmailStyle18 {mso-style-type:personal-reply; font-family:Arial; color:navy;} @page Section1 {size:8.5in 11.0in; margin:1.0in 1.25in 1.0in 1.25in;} div.Section1 {page:Section1;} --> </STYLE> <DIV> <DIV><FONT face=Arial>The Al arms are quite resistant to twisting - but you're correct that the nylon wheel is plenty strong and the Al wheel stronger than either. </FONT></DIV> <DIV><FONT
face=Arial></FONT> </DIV> <DIV><FONT face=Arial>A few years back I tested the strength of the JR 8411 Al spline and the equivalent nylon spline coupled to stock & H9 Al arms. The test involved making an adaptor to set over a single arm and position an inch-lb torque wrench directly over the shaft. An output gear / shaft was clamped in a vise and the torque wrench used to measure the "give" point and the failure point with different combinations. All exceeded the torque rating of the servo.</FONT></DIV> <DIV><FONT face=Arial></FONT> </DIV> <DIV><FONT face=Arial>Nylon shaft & arm: "Give" @ 320 oz in and failure @ 480 oz in - the spline shaft twisted and slipped, arm spline damage (yet there was enough binding to retain some control transfer).</FONT></DIV> <DIV><FONT face=Arial></FONT> </DIV> <DIV><FONT face=Arial>Nylon shaft & Al arm: "Give @ 320 oz in and failure @ 560 oz in - shaft spline total failure.</FONT></DIV> <DIV><FONT
face=Arial></FONT> </DIV> <DIV><FONT face=Arial>Al shaft & nylon arm: No "give" point. Crisp failure @ 560 oz in - arm spline total failure.</FONT></DIV> <DIV><FONT face=Arial></FONT> </DIV> <DIV><FONT face=Arial>Al shaft & Al arm: No "give" point, Crisp failure @ 1600 oz in - no spline damage, shaft broke below spine.</FONT></DIV> <DIV><FONT face=Arial></FONT> </DIV> <DIV><FONT face=Arial></FONT> </DIV> <DIV><FONT face=Arial>Earl</FONT></DIV></DIV> <BLOCKQUOTE style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px"> </BLOCKQUOTE></BLOCKQUOTE>