---------------------------------------------------------- Europa-List Digest Archive --- Total Messages Posted Fri 09/14/18: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:14 AM - Re: Re: Mono tail wheel spring mounting bolt break (roddy kesterton) 2. 03:33 AM - Re: Mono tail wheel spring mounting bolt break (Nigel Graham) 3. 10:02 PM - Re: Re: Mono tail wheel spring mounting bolt break (NEEL Jean Philippe) ________________________________ Message 1 _____________________________________ Time: 12:14:49 AM PST US From: "roddy kesterton" Subject: RE: Europa-List: Re: Mono tail wheel spring mounting bolt break I agree that these are really good solutions, so thank you Eric and John. They address the issue that the bolt no longer has bending mode, but also the issue that both Barry and I had in that the bolt seems to have sheered due to fatigue, and on the ground. The bolt is not in compression on landing, or when stable on the ground, as the tailwheel arm is pivoted at the sternpost,. I think that most of the tension stresses causing the fatigue will come from weight on the bolt during flight, and mine actually broke after being bounced around on the ground during stormy weather. (I now also tied down the tailwheel when parked.) Roddy -----Original Message----- From: owner-europa-list-server@matronics.com On Behalf Of tennant Sent: 12 September 2018 11:56 Subject: Europa-List: Re: Mono tail wheel spring mounting bolt break --> Hi Eric & John, It looks as if you both came to the same solution with differing ways to do it. Both good and a great improvement on the standard design. Barry -------- Barry Tennant D-EHBT At EDLM - Germany Read this topic online here: http://forums.matronics.com/viewtopic.php?p=483138#483138 ________________________________ Message 2 _____________________________________ Time: 03:33:02 AM PST US Subject: Europa-List: Re: Mono tail wheel spring mounting bolt break From: "Nigel Graham" The bolt failures are the symptom of the problem not the cause! The problem is the plywood stack that the tail spring sits on. During the build, the plywood is sheathed in waterproof epoxy, but then you have to drill the hole for the bolt to pass through, exposing the wood to the atmosphere and THAT is the problem. In service, moisture wicks up the bolt and into the plywood end grain, where it sits unseen. Eventually the wood begins to rot and the structural rigidity is lost. At this point, the clamping force of the bolt is lost and the spring begins to rock from side to side during taxying. This allows the bolt shank to fret and eventually the fatigued bold will fail. I have attached a picture of a tail spring bolt that was replaced just in time (the ground handler noticed the tailwheel flopping from side to side during taxying). This shows everything; the deep pitted rust indicates that the plywood stack was wet, the fretting has worn away the blot shaft where is passes through the end of the tail spring, and you can see the fatigue crack developing nicely. Simply replacing the bolt will cure the symptoms, but it will eventually fail again in exactly the same way. To affect a lasting repair, the plywood should be thoroughly dried out and then impregnated with a thinned epoxy resin to restore the structural rigidity. To keep the bolt shank away from the wood, I over bored the mounting hole to accept a 5/16 bore 4041 sleeve, which was bonded permanently in place. The new bolt was then greased and inserted through the sleeve. I also made up a steel saddle bar that sits on top of the tail spring mount to prevent it from rocking (just like Jons). Nigel Read this topic online here: http://forums.matronics.com/viewtopic.php?p=483177#483177 Attachments: http://forums.matronics.com//files/tail_spring_bolt_110.jpg http://forums.matronics.com//files/tail_spring_bolt_201.jpg ________________________________ Message 3 _____________________________________ Time: 10:02:42 PM PST US From: NEEL Jean Philippe Subject: Re: Europa-List: Re: Mono tail wheel spring mounting bolt break Bonjour ErichCould=C2- you please send me a drawing with cotation of your interesting solution?MerciJean-Philippe NEELN=C2=B0 273 F-PSLHFrance Le Mardi 11 septembre 2018 22h54, Erich Trombley a =C3=A9crit : Hi Barry,=C2-Glad to hear you didn't sustain any damage to your plane. =C2- Typical of other Mono folks I too bent my tail wheel bolt which led me to creating the following mod I performed over 10 years ago.=C2- Never had a problem since.=C2- The original design relies on the AN5-21A bolt to counter the torsional load of the tail spring which isn't ideal as you c an attest too.=C2- I created a simple mod that takes the torsional load f rom the tail spring and transfers it to the XTW15 steel support plate rathe r than the AN5 bolt in bending.=C2- I installed an aluminum block with a channel milled down the middle (the width and height of the mounting end of the tail spring) with a through hole in the center to pass the AN5 bolt. =C2- As shown in the attached drawing the block captivates the end of the tail spring and transfers the load as described above.=C2- The AN5 bolt is now in double shear instead of single shear and bending.=C2- A longer bolt is required to replace the existing AN5-21A which is too short to pass through the block.=C2- That's it. And it works a treat.=C2- You may no t even require approval of the mod as it could be considered a really thick washer of sorts. :)=C2- The mod also prevents the through hole in the bo ttom of the fuselage in which the AN5 bolt passes from wallowing out.=C2- Also, regarding bonding of the tail spring to the rear stern post I deviate d slightly from the instructions.=C2- When I originally installed the tai l spring I was giving consideration to serviceability and realized if the s pring were bonded to the stern post I would need to deal with the Redux.=C2 - Realizing the benefit of having the additional bearing surface of the R edux I installed the tail spring per the manual, however, I applied a relea se to the tail spring such that the Redux wouldn't adhere.=C2- This allow s the tail spring to be easily removed without compromising the design.=C2 -=C2-=C2-Glad to answer any questions you may have.=C2-Regards,Eric hN28ET Classic Mono 914 ____________________________________________________________ Unbelievable German World War 2 Photo Shocks Americans pro.healthresponses.org http://thirdpartyoffers.juno.com/TGL3132/5b9829569b4262956084ast02vuc ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message europa-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Europa-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/europa-list Browse Digests http://www.matronics.com/digest/europa-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.