What is/are the reason(s) for doing this?
http://www.flickr.com/photos/aerotowrelease/8305308635/
Barrel Release, second from bottom.
I make my Barrel Releases a standard minimal length and then extend them from their mountings a desired or necessary length using some sort of Adjuster:
http://www.flickr.com/photos/aerotowrelease/8312203997/
http://www.flickr.com/photos/aerotowrelease/8312206905/
http://www.flickr.com/photos/aerotowrelease/8312208727/
http://www.flickr.com/photos/aerotowrelease/8312211409/
http://www.flickr.com/photos/aerotowrelease/8313263612/
To keep the front end of the Adjuster from getting damaged by the back end of the Barrel as a result of repeated hard pulls, I install a Stop - a short sleeve of vinyl tubing - over the leechline Body of the release aft of the Barrel.
If I fix the position of the Stop as far fore as possible while allowing the Barrel to fully clear the Pin in a slack line situation it makes it difficult - but not impossible - to close the Barrel over the Pin when it's been flipped - versus rotated - back to retain the Weak Link - as you have illustrated here:
http://www.flickr.com/photos/psucvollibre/5958248335/
The reason this works is because when you (properly) ROTATE the Pin it only extends back the length of its shaft. And when you (improperly) FLIP the Pin it extends back its OVERALL LENGTH - the length of the its shaft PLUS the length (diameter) of the its eye.
So limiting the allowable aft travel of the Barrel with the Stop DOES make the Barrel Release idiot resistant at no additional cost in materials, construction effort, complexity, weight, or drag. But that's not THE REASON for that aspect of the design. THE REASON is to protect the assembly from damage and wear. And if that reason didn't exist I wouldn't add the Stop Assembly just to cater to people too stupid to properly engage a barrel release.
And I never discuss the flipped pin "issue" unless somebody brings it up 'cause it's:
- not an actual issue anyway; and
- a really bad idea to show people how to do something wrong.
(On the latter... Like it's a really bad idea to teach people that hang checks and/or Aussie Methodist assembly procedures help prevent people from launching unhooked.)
Note that with the perpendicular pin loaded up:
http://www.flickr.com/photos/aerotowrelease/8312399698/
(to 400 pounds in that photo) the Body line (green and white) and Bridle Link line (red) are being mashed together, so damn near all the tension is going to trying to compress that area of the eye - which it can't do - and you're minimizing the vector of the tension going to torque the pin and thus distort it and jam its end into the Barrel wall. The tangent pin is is way less optimal in those regards.
Ok you lost me there...
In the 1997/02 issue of the magazine I've got a letter to the editor published which says, amongst a couple of other fairly obvious issues, that if you only have a weak link on one end of a long bridle and that end of the bridle wraps at the tow ring (after a release or weak link failure) you no longer have a weak link in your system. So you need weak links above and below or on both sides of a tow ring on any bridle long enough to wrap (and if it's a two point bridle the weak link at the bottom has gotta be stronger than the one at the top).
Then eleven months later Dennis and his evil idiot sidekick publish their evil idiot book. It DOES include descriptions and illustrations of configurations in which the weak link is installed at the downwind end of the towline. That's fine - the glider and any of its releases are protected at all times no matter what. But with respect to configurations in which there's nothing on the towline (like ALL aero in the US and Australia) try to find a single instance of a requirement for, reference to, illustration of a redundant or secondary weak link ANYWHERE between the covers.
Towing Aloft towing is safer than pushing the volume control button on your remote 'cause the safer it is the more people will do it, give their money to the Flight Park Mafia, join USHGA, buy copies of Towing Aloft, and tell all their friends how incredibly safe towing is.
In Towing Aloft towing the ONLY way a bridle end can fail to clear a tow ring is if someone were stupid enough to have installed on it a Tjaden Link - similar to the one illustrated on Page 60. So the ONLY reason one needs a "BACKUP" release is because it's beyond the capabilities of human engineering to design a primary release capable of functioning more than about three out of four tows and there's no danger whatsoever with using the backup as a primary 'cause - since there's no weak link on the bottom end of primary bridle - it's incapable of tying itself to the tow ring and leaving you instantly being towed by the keel with the full towline tension.
And on Page 291 you have:
Figure 7-16: Fixed Wing Tug Bridle and Release System
depicting a Dragonfly bridle/release system with the:
- weak link at the top end of the bridle engaging the tow mast and
- bridle running through an eye at the front end of the towline and back down to the
- Schweizer type release coming off the back end of the fuselage tube.
And there's the assurance that the:
Bridle slips through towline loop when released.
But meanwhile, back in the REAL world, a bit of which they advertently include on Page 349:
I witnessed a tug pilot descend low over trees. His towline hit the trees and caught. His weak link broke but the bridle whipped around the towline and held it fast. The pilot was saved by the fact that the towline broke!
we see that - especially when the shit hits the fan - the fucking bridle tends NOT to slip through the towline loop when released. Which is why the fucking regulations say to put the fucking weak link on the end of the fucking towline and why I've been saying that if you don't put a fucking weak link on the end of the fucking towline then have fucking weak links on BOTH ends of the fucking BRIDLE so there's no possibility of a 250 foot length of two thousand pound spectra becoming your fucking weak link.
I can't think of a more blindingly obvious illustration of a more blinding obvious common sense issue yet, here we are at the beginning of 2012 and all Dragonflies are still configured the way that one was. (Really wish Charles Darwin would get off his fat ass and do his job on these guys often enough to get the point made clearly enough for people to start getting it.)
Seven and a half years after my letter, on the Capitol club rag...
http://www.chgpa.org/forums/viewtopic.php?f=2&t=939
Weak link breaks?
Daniel Broxterman - 2005/08/26 14:28:42 UTC
While we're on this topic...at Wallaby in April the launch crew put a 2nd weak link in my system between the bridle and the Bailey. I fly with a two point, Wallaby-style release, with a single Bailey secondary. As I recall, here's the scenario they had in mind:
Pilot releases with primary, bridle catches on the tow line or release mechanism. If pilot becomes extremely out of position, the additional weak link would probably breaks prior to pilot finding and Bailey.
Does anyone else use two weak links, one on each release point?
Yeah Daniel, I said something like that - in English which would've gotten me through third grade and without the crap about catching on the release mechanism, getting out of position, and finding Baileys - seven and a half years before but nobody listened.
So at the 2006 ECC in early June at Ridgely Dennis is flying one point with a Bailey mounted on his (call it) right shoulder and an overly long spectra bridle connected to his left. Loop of 130 pound Greenspot engaging the Bailey. (His flying weight is 255 hook-in plus glider (and I was still a 130 pound Greenspot zombie at that point in history).)
I'm setting him up with a pair of my Barrel Releases. He's worried about engaging the somewhat bulky bridle end with the left Barrel Release. I tell him I'll just slap on another weak link. He has this huge lightbulb moment. Obviously such a bizarre idea had never occured to him.
Likewise...
Knowing nothing about hydraulic cylinders I was trying to gear up for some in-flight and bench testing.
Towing Aloft, Page 116:
The small, cheap cylinders manufactured by Boston Gear, Flair Line, Bimba, Humphries and other manufacturers work well. Diameters between 1 1/8 and 2 inches and strokes between 2 and 3 inches are appropriate.
I wanted to go as small and light as possible, had my eye on a Bimba 1 1/16 inch diameter cylinder with a one inch stroke, and wanted to know why two to three was being recommended. Could find no one who could tell me so when I finally crossed paths with Dennis I asked him. No freakin' clue. It was obviously just something somebody had told him so he just scribbled it down and published it. (I understand hydraulic cylinders now, by the way, and a one inch stroke is just fine.)
Sorry. Way too long an answer.
It's ESSENTIAL to have a weak link in your system at all times - even though you're probably not gonna have any need for it in a hundred lifetimes - but the Industry Standard idiots who are so insistent that the purpose of the weaklink is to increase the safety of the towing operation - PERIOD - are mostly loath to configure such that you actually HAVE one when you're MOST likely to NEED one.
