Thorp Air Command - T18.net http://t18.net/thorpforum/ |
|
Beefed up Tail spring attachment http://t18.net/thorpforum/viewtopic.php?f=2&t=7148 |
Page 1 of 1 |
Author: | stug [ Thu Nov 01, 2012 6:26 am ] | ||
Post subject: | Beefed up Tail spring attachment | ||
Hi all It's been suggested at some point that consideration be given to beefing up the tail spring attachment points. The 2 *4130 steel brackets on frames 576 and 575. I recall reading some accounts of modifications being being done in this area but not a detailed account. Attached is a drawing of the 583 fitting with one possible option for the bracket which would extend across the full width of the lower skin so it can be riveted onto the 580-4 longerons instead of just the frame. Any thoughts on the attached drawing, does it look like a reasonable option, striking the right balance between added weight and added strength? Stuart
|
Author: | fytrplt [ Thu Nov 01, 2012 7:58 am ] |
Post subject: | Re: Beefed up Tail spring attachment |
Stuart, That is exactly what I ended up doing after in-service cracking occurred in the fitting. So far, about 1500 hrs later, no cracking. |
Author: | Bill Williams [ Thu Nov 01, 2012 9:52 am ] |
Post subject: | Re: Beefed up Tail spring attachment |
Mine broke at 300 hours, so I copied Bob, no problems in 1000 hours. As for the weight, it helps in the S-18 with W&B. |
Author: | leewwalton [ Thu Nov 01, 2012 9:55 am ] |
Post subject: | Re: Beefed up Tail spring attachment |
I would think that the extra weight would help the T-18 more than the S-18. The reason the S-18(T-18CW) is limited to 0-320's and up is due to the extra length moving the CG aft. |
Author: | Bill Williams [ Thu Nov 01, 2012 9:59 am ] |
Post subject: | Re: Beefed up Tail spring attachment |
I have the 0-360 with CS prop , needed all the help I could get for the forward CG. I have the Dayton motor for trim and aft battery. |
Author: | stug [ Thu Nov 01, 2012 4:17 pm ] |
Post subject: | Re: Beefed up Tail spring attachment |
OK it seems like this mod is worthwhile and the additional time invested now will save some later Next question, is the heaver gauge steel recommended ? I assume that just distributing the stress loads to the longerons with the current gauge material will improve the resistance to fatigue cracking in the frame but if the steel fitting has a history of cracking then it might need beefing up as well? I like Fraser's approach, using bolts through the longerons into the fitting instead of rivets, I would have thought that has merit in this scenario. Stuart |
Author: | jrevens [ Thu Nov 01, 2012 4:36 pm ] |
Post subject: | Re: Beefed up Tail spring attachment |
I think it's definitely worth it, Stuart. Many of us have done additional reinforcing in that area. Just another little thing to keep in mind is the necessity to cleanly de-bur all holes and file smooth, or even polish the edges of the steel to eliminate stress risers. I've seen several pictures of cracked fittings in this area which obviously had poor/rough edge finish. I'm sure you're aware of that, but it doesn't hurt to mention. I'm also pretty sure that I increased the material thickness of the 583 fitting to .093" (same as the rear fitting), and did other mods as well to carry the loads over to the side skins and flanges of the frame. I also made a heavier bottom skin/plate in that area, again to distribute the loads more widely to the sides. I actually caught the tailwheel on something hard enough to deflect it up into the rudder once, but that's another story. 22 years - no signs of distress. |
Page 1 of 1 | All times are UTC - 6 hours [ DST ] |
Powered by phpBB® Forum Software © phpBB Group https://www.phpbb.com/ |