This is not strictly Rotary related, but I thought it might be of interest. http://www.cozybuilders.org/Desert_Center/Prop_Bolt_Retention.html Brian Trubee He did it wrong. You don't need that much deflection. One or two springs would have done the job in parallel instead of some in series. Paul Lamar ...No rotor no motor. The Rotary Engine NewsLetter. Powered by Linux. ACRE NL web site. http://www.rotaryeng.net Youtube key word UTUBPLEASE Copyright 1998-2008 All world wide rights reserved.