New Release?

[Steve Davy]

My peanut brain just exploded!

[Tad Eareckson]

Glad I'm not the only one. Every now and then I start to understand a piece of it and then I collapse and hafta try to start over. This may take a while.

[Zack C]

Sorry...let me know if I can clarify anything in particular.

Zack

[Tad Eareckson]

Lemme drop back to peanut mode.

- This thing is a barrel release - like the ones you have on shoulders.

- It uses the same stainless steel pin that mine does.

- The barrel's about the same ID as mine but it's stainless instead of aluminum so it may slide a wee bit better under load but, basically, we're talkin' the same mechanism with the same range and about the same performance.

- My shoulder mounted barrel release has an internal brake device which keeps the thing from falling apart before it's loaded and totally disengages when the tension comes on.

- As you approach four hundred pounds with the release engaging something fat enough to handle four hundred pounds you run a risk of distorting the pin so keep it down to 350.

- The release has a load to actuation ratio of about 16.4 to one so at 350 you're pulling about 21.3 pounds. That's overkill for solo and good enough for tandem (and a lot better than those assholes are doing on their own now).

(If anyone is wondering the point of all this, I'm just trying to predict what kind of difference we could expect with a negligible spring resistance.)

- We know what it will do - to any degree of accuracy that matters - from my own tests on my stuff.

- Joe's heavy spring and required barrel travel are design defects. Rather than doing the testing and math to figure out what's going on with his release we need to:

-- swap in a spring which is appropriate for the job and - happily - of negligible importance in the performance and equations; and

-- chop down the barrel length so the fuckin' spring is of even more negligible importance in the performance and equations.

On Joe's release as it is...

However, this would mean the L/A with no spring resistance is ~37.

- Do we know that Joe ran the 150 kg test with the spring in the system?

- Any variation in the length of the Spectra body from copy to copy is gonna have a big influence on how much of an issue the spring is.

- You can determine a worst case spring factor by using your fish scale to fully compress the spring. So whatever's going on with a particular copy and/or loading it will be that number or - almost certainly - a lot less.

[Zack C]

Alright, fair enough. I'll be sending some feedback to Joe soon and I'll relay this to him then.

Regarding the length of the barrel, I noticed looking back that he addressed that also...

A weaker spring or a shorter outer barrel might make it seem even lower effort but I decided I didn't want a hair trigger device either.

Zack

[Tad Eareckson]

BOTH!!!

Neither the spring tension nor the barrel length have ANYTHING to do with hair trigger. Hair trigger is ENTIRELY lanyard play.

You make the spring just strong enough to reliably hold things together before they're loaded and you make the barrel just long enough to reliably hold things together when they're max loaded.

Look at a spinnaker shackle.

http://www.flickr.com/photos/aerotowrelease/8305428629/


It's not designed to do our job but it's beautifully engineered.

Look at the spring latch which secures the gate. That's analogous to the combination of Joe's barrel and spring or my barrel and bungee.

- The spring tension which holds it closed is 3.3 pounds and it comes with a lanyard installed which doubles the mechanical advantage. (I remove the lanyard and restore the mechanical advantage with a pulley.)

- And how far do you need to pull the latch back before the thing blows?

Whenever we design something we need to look at what's already out there, take the best of all the best features and parameters, and adopt, adapt, and/or improve on them. Otherwise we're just wasting our time trying to get square wheels to roll better - and endangering people in the process.

[Steve Davy]

There are six strands passing through the pin eye...

Oh, I didn't know that.

I didn't imagine that tiny bit of string would deflect the line to such a noticeable degree. Also I tend to forget how small this device is.

My shoulder mounted barrel release has an internal brake device which keeps the thing from falling apart before it's loaded and totally disengages when the tension comes on.

Wouldn't the internal brake device remaining engaged when tensioned reduce the probability of a release caused by contact with the base tube?

[Tad Eareckson]

I didn't imagine that tiny bit of string would deflect the line to such a noticeable degree.

That's actually not that tiny a bit of string. That's 3/32 inch 350 pound test Dacron leechline.

Also I tend to forget how small this device is.

I used to show all the Quallaby clones at Ridgely my release system. They were frequently unable to find it on their own.

Wouldn't the internal brake device remaining engaged when tensioned reduce the probability of a release caused by contact with the base tube?

No. In two point mode a barrel release is under 29 percent of the towline tension (and in one point - fifty) and if it gets dragged across the basetube you can count on it opening.

If you increased the internal resistance to try to keep it closed you'd also be keeping it closed when your life depended on prying it open.

If, however, it's used in conjunction with a Four-String emergency release - which is how I configure - you don't really need it as part of a two point configuration. You can take it out and throw it away.

In a one point configuration you want it 'cause the Four-String burns a little when it's released under load so you don't really wanna be using it as a regular primary non-emergency release.

You COULD, however, reasonably easily safety the barrel release by installing a pin or something just aft of the barrel which would prevent it from opening. Get to safe or release altitude and pull the pin.

But I'm not seeing incidents in the field which makes this an issue worth worrying too much about in a well configured system. We've got zillions of those idiot Bailey releases which are optimized for snagging on the basetube going up on virtually every aerotow and opening incidents are rare and consequential incidents are nonexistent (so far).