JL Chute Release - latest improvements?

[jahall4]

Got it - Looking back at the photos you posted I see that now.

Interesting that in the two photos in post #58 above you have the shock cord going thru the nomex blanket in the middle of the sled. In post #39 there is also a picture where the nomex is on the cord separate from the sled.

Which do you recommend? Either/or?

Generally you are going want the blanket as "free flapping" as possible as long as it can't reef the chute. The rigging pictured here was "creatively specific" to a large cute and JLCR in a BT-60 size tube.

 

[Pinetree]

Well, I ordered one.

We shall see how it goes.

 

[4regt4]

Well, I ordered one.

We shall see how it goes.

Follow the instructions, keep it simple, and try to make the chute bundle as tight as you can.

You'll be impressed.

Hans.

 

[pwrwgnwalt]

Two things I noticed during my preflight JLCR testing in the house…

1. the pin was only released when there was a fair amount of tension on the rubber band (not an extreme amount, just needs tension to pull the pin out during the one-second, or so, release of the capture rod).

2. the parachute needs to be very solidly folded; providing enough tension for the first point above, and to prevent the rubber band from ‘digging into’ the chute and creating a situation where it could fouled by the air folding the chute around the rubber band. A compact chute folding, with an appropriately-sized rubber band stretched around the chute, produced a definite ‘pop’ release, clean of the chute.

On my first in-flight use (for my Level 2 certification), it performed flawlessly with a 400’ release on a 3,861 ft flight (the JLCR-bundled main chute deployed at apogee and rode ~3,461 down before deployment, acting almost like a drogue, as planned).

 

[Pinetree]

Ordered on Friday night (free shipping option).. got it Monday morning.

And I'm on the other side of the country.

Bravo.

 

[rcktnut]

I still see the word rubber used after all the threads about using alternatives. Ditching the rubber and using something else will eliminate at least one form of failure.

 

[jahall4]

I still see the word rubber used after all the threads about using alternatives. Ditching the rubber and using something else will eliminate at least one form of failure.

4 letters: EPDM

 

[OverTheTop]

Ditching the rubber and using something else will eliminate at least one form of failure.

and making sure the sharp ends on the ring the rubber band attaches to are covered or filed off will fix another. The sharp ends can catch on the chute and not release in some circumstances.

 

[Pinetree]

I also want to add that one of the bands was defective (I know, nobody uses the bands), so I sent a pic in an email, and Mr. Beans is mailing me a few extra.

Being a long haired guy with a ponytail, I have plenty of hair ties to use, but this is customer service at its best.

 

[TRWXXA]

and making sure the sharp ends on the ring the rubber band attaches to are covered or filed off will fix another. The sharp ends can catch on the chute and not release in some circumstances.

How about a strip of tough cloth (maybe from a worn out nomex chute protector) about 1.5 to 2 inches wide, that's wrapped around the bundled chute, between it and the JLCR? That would help keep the rubber band from digging into the bundle, and protect the chute from the sharp ends of the ring.

It would be sacrificial and fly away at release, but maybe someone could work out a way of keeping it attached to the JLCR without it being a tangle hazard for the chute.

 

[John Beans]

Also one bit of advice I would add: unbeknownst to some Chute Release has a swivel that the pin is inserted into that swivels from side to side. Always make sure you make sure your pin is being pulled straight out by your band.

After manufacture the swivel is rather stiff, so it might not naturally swivel towards the direction the pin is being pulled and you might need to turn it yourself.

If for instance the pin is pointing straight up and not to the side and slightly down, it can release and the band will actually hold the pin in the swivel. No bueno.

Hope that description makes sense?

 

[jmasterj]

Also one bit of advice I would add: unbeknownst to some Chute Release has a swivel that the pin is inserted into that swivels from side to side. Always make sure you make sure your pin is being pulled straight out by your band.

After manufacture the swivel is rather stiff, so it might not naturally swivel towards the direction the pin is being pulled and you might need to turn it yourself.

If for instance the pin is pointing straight up and not to the side and slightly down, it can release and the band will actually hold the pin in the swivel. No bueno.

Hope that description makes sense?

Yup, definitely noticed that when I was practicing with my first chute release.

 

[jahall4]

Also one bit of advice I would add: unbeknownst to some Chute Release has a swivel that the pin is inserted into that swivels from side to side. Always make sure you make sure your pin is being pulled straight out by your band.

After manufacture the swivel is rather stiff, so it might not naturally swivel towards the direction the pin is being pulled and you might need to turn it yourself.

If for instance the pin is pointing straight up and not to the side and slightly down, it can release and the band will actually hold the pin in the swivel. No bueno.

Hope that description makes sense?

It does John, but I have never noticed one acting this way. Probably a very small number exhibit that behavior and one would almost have to try to make it happen.

 

[Sooner Boomer]

Also one bit of advice I would add: unbeknownst to some Chute Release has a swivel that the pin is inserted into that swivels from side to side. Always make sure you make sure your pin is being pulled straight out by your band.

After manufacture the swivel is rather stiff, so it might not naturally swivel towards the direction the pin is being pulled and you might need to turn it yourself.

If for instance the pin is pointing straight up and not to the side and slightly down, it can release and the band will actually hold the pin in the swivel. No bueno.

Hope that description makes sense?

Good advice. I've seen this with people not used to using the JLCR. This is one reason why you **always** ground test before flight! The direction the swivel needs to point depends upon the diameter of the chute bundle.

 

[Johnly]

Reviewing projects for NASA SLP provides the opportunity to examine other deployment strategies. Using JLCR in high power flights with rubber band retention of the parachutes has an increased occurrence for the parachute working free during descent. One team opted to replace the rubber band with a zip tie, which worked perfectly. Lightly compressing the parachute with the zip tie allows for release of the parachute as designed, with the parachute material elastic material. A new zip tie for each use lets the flier adjust the retention compression as needed and eliminates the compression variation caused by aging rubber bands.

 

[jahall4]

Reviewing projects for NASA SLP provides the opportunity to examine other deployment strategies. Using JLCR in high power flights with rubber band retention of the parachutes has an increased occurrence for the parachute working free during descent. One team opted to replace the rubber band with a zip tie, which worked perfectly. Lightly compressing the parachute with the zip tie allows for release of the parachute as designed, with the parachute material elastic material. A new zip tie for each use lets the flier adjust the retention compression as needed and eliminates the compression variation caused by aging rubber bands.

Most any technique will work if done properly, but I suspect that John would advise against using only a zip tie and relying on the chute to provide the elasticity, as it would encourage over tensioning . Instead, EPDM rubber bands appear to be the best solution. However, they are not as “stretchy” as a common rubber band, and have to be carefully sized. Otherwise, too much tension can be created, resulting in the JLCR NOT releasing at all. John has explained that some users are repeatedly testing their JLCRs under with hihg tension, leading to the opposite failure mode where the pin won’t clip in because the sear mechanism has been worn out.

The solution to mitigating the parachute (or its shroud lines) working free during descent is to immobilize the chute pack relative to the harness. In 2016 the “recovery sled” or chute sled was developed to do just that.

Backstory… After a failed inflation, that could not be explained, on a 72" chute at SEARS in Oct. 2016 I started investigating. Flight video from test flights showed that the shroud lines could pull out of the pack even on much smaller rockets, using much smaller chutes. Apparently, the pack thrashing about in the air stream could twist pulled lines fouling the chute. This is more of an issue on larger chutes given the JLCR’s lesser ability to compress the pack. The pack gets bigger, but of course the JLCR does not scale up with the pack.

It seemed reasonable that if the chute could be kept immobile relative to the harness that could not happen. The recovery sled does just that when properly configured, because the chute pack cannot move independent of its harness attachment point. They must move together until the JLCR releases. This can be readily inspected when packed. The chute pack is held to the sled by the JLCR, the sled is fixed along the harness at each end so where the harness moves so does the pack, and vice-a-versa.

Whether you purchase one of our sleds, heat formed from nearly indestructible polycarbonate, or fashion your own you’ll find your deployments are far more reliable even with larger chutes.

Facebook Shop (e.g. 8” x 3” pack): https://rb.gy/zrouz

 

[edpolakoff]

4 letters: EPDM

What's the best source for EPDM bands and what sizes are you using? I'm tired of the factory ones breaking after 1 use.

 

[jahall4]

What's the best source for EPDM bands and what sizes are you using? I'm tired of the factory ones breaking after 1 use.

EPDM should not be breaking.

Any source is probably fine. You'll need to purchase based on length needed for pack size and cut the width down to achieve the desired elasticity and hence tension, little bit of alchemy to this.

 

[John Beans]

You can also use really long rubber bands that constrain the bundle from all directions, like putting a ribbon on a package, where the ribbon goes around the box in a crossed fashion and Chute Release is the knot and bow.
Of course: with that added length comes added ground testing caution that the entire band will reliably fall from the bundle.
Also: if you do constrain the bundle with a very long band, you probably can use a lighter band since you are relying on geometry rather than brute force to hold it closed.

 

[John Beans]

Reviewing projects for NASA SLP provides the opportunity to examine other deployment strategies. Using JLCR in high power flights with rubber band retention of the parachutes has an increased occurrence for the parachute working free during descent. One team opted to replace the rubber band with a zip tie, which worked perfectly. Lightly compressing the parachute with the zip tie allows for release of the parachute as designed, with the parachute material elastic material. A new zip tie for each use lets the flier adjust the retention compression as needed and eliminates the compression variation caused by aging rubber bands.

I'd rather see folks experimenting with sleds and longer bands than ever relying on zip ties.

Zip ties are super wicked strong, stronger than the mechanism of Chute Release itself. Zip ties are "brute force" tools. You solve one problem (weakened bands) at the potential expense of the entire device. Yes, you can get away with using them, but someone seeing your solution is likely to misapply them, as are you in the future with a weak battery or gimpy servo.

For those of you in the mood to ruminate more about this, I would gently suggest that Chute Release is (in a sense) an exercise in reducing activation force. In other words, we are trying to transition from explosions (lots of energy to blow the chute from a closed tube) to very little (a tiny battery and servo that holds something folded).

The natural extension of this—"try to use the least amount of energy possible to accomplish the task"—would be to use the slightest tension possible to do the job. Imagine a very thin rubber band that criss-crosses in several directions around a rather large bundle as it tumbles. There's no giant force trying to pull the bundle apart, we are just keeping the edges tucked in and preventing it from being blown open in the slipstream as it tumbles.

The lower you can keep the activation force, the more likely you are to have plenty of energy to make it happen. You want a tiny hill to jump over, not an incredibly steep one.

Hopefully that all makes sense.

 

[Starfire73]

The best way we have found to mitigate failure is to use a “Recovery” or chute sled. A success rate of near 100% should be expected when rigged properly. Whether you make your own or buy one from us don’t launch another rocket w/o one. I know I sound like a marketing hack, but here is the story…

After a failed inflation, that could not be explained, on a 72" chute at SEARS in Oct. 2016 I started investigating. Flight video from test flights showed that the shroud lines could pull out of the pack even on much smaller rockets, using much smaller chutes. Apparently, the pack thrashing about in the air stream could twist pulled lines fouling the chute. This is more of an issue on larger chutes given the JLCR’s lesser ability to compress the pack. The pack gets bigger, but of course the JLCR does not scale up with the pack.

It seemed reasonable that if the chute could be kept immobile relative to the harness that could not happen. The recovery sled does just that when properly configured, because the chute pack cannot move independent of its harness attachment point. They must move together until the JLCR releases. This can be readily inspected when packed. The chute pack is held to the sled by the JLCR, the sled is fixed along the harness at each end so where the harness moves so does the pack, and vice-a-versa.

Even use them for Triunal Deployment (back up mains):

I see you are bundling your shock cord. Does that painters tape stay on for the launch? If so, have you ever seen it where the ejection force, weight of the rocket, etc., wasn't strong enough to break the tape? I had a chute failure to fully open recently because it was all in tangled mess with the shock cord. That't bundling (or whatever you call it) looks like it would significantly improve parachute deployment.

 

[Pinetree]

I use blue tape on the shock cord and it comes right off during deployment.

 

[jmasterj]

And on the off chance it doesn't break (I've had it happen with MPR birds), that just means your ejection event was gentle!

 

[Pinetree]

In the interest of clarity, I have 20 ft of Kevlar shock cord and a fiberglass nose cone... but the tape hasn't been a problem.

 

[4regt4]

I've bundled the cord with tape, tiny rubber bands, and braiding. All seemed to work. The OCD in me wonders if one method is better, but I have no evidence one way or another.

Recently I've stopped braiding the cords because as they get a bit covered in BP soot, they get a little sticky. So I'm concerned about friction in the unraveling process that could eventually abrade the cord. Again, no evidence....

Hans.

 

[jahall4]

I see you are bundling your shock cord. Does that painters tape stay on for the launch? If so, have you ever seen it where the ejection force, weight of the rocket, etc., wasn't strong enough to break the tape? I had a chute failure to fully open recently because it was all in tangled mess with the shock cord. That't bundling (or whatever you call it) looks like it would significantly improve parachute deployment.

I cringe when you say bundle because it is the farthest thing from it . Since the "coils" are wound around their own centers it is impossible for them to bind with themselves. While there is strong anecdotal evidence that it does increase reliability of deployment it's primary purpose is getting as much harness in the airframe as possible. And no in a HPR rocket, the tape is going to break. Keep in mind the only purpose of the tape is to keep the coil together. For smaller coils just use more narrow tape.

 

[jmasterj]

Taping z-folded shock cord bundles together works well for a lot of people. It's not as compact as those rolls, but often that's not an issue.

 

[mtnmanak]

Sorry, I blended together two different points about the JLCR. Yes, weird things can happen with unfurling a bound parachute, but two or more JLCR chained together won't fix the problem. Better chute packing techniques are needed.

Clearly, you are missing the point. I like to daisy 4 or sometimes even 5 JL chute releases and ditch the expensive rubber bands altogether.

Solution brought to you by the US government - "Never underestimate the power of over-engineering and over-budgeting a solution that makes no sense to begin with!"

 

[Angel_of_the_Skies]

Well, I ordered one.

We shall see how it goes.

Have you launched any rockets with it yet ?

I don’t want to get into HPR yet, and hope to be able to launch MPR higher than 1k without being scared of rocket drifting away

 

[4regt4]

Have you launched any rockets with it yet ?

I don’t want to get into HPR yet, and hope to be able to launch MPR higher than 1k without being scared of rocket drifting away

They work very well. Probably the biggest issue is folding the chute. It needs to be in a tight bundle so that the rubber band (actually, I use a hair pony tail thingy) doesn't dig into the chute and get caught and it needs to be folded such that the chute doesn't sneak out of the JLCR's grasp. A bit of practice and experience goes a long way. I've combined ideas from the various chute folding threads here to come up with something that has had no failures in perhaps 50 launches.

Hans,