Chris' Punisher 4 L3 build

[PokerJones]

What is a "quick release pin?"

It's an attachment point on his machined bulkheads.

https://ape-rc.com/#!/4-Machined-Bulkhead/p/59245081/category=11909535

 

[ChrisAttebery]

Yep, originally I had wanted to use a 10-32 SHCS with an unthreaded shoulder, but I couldn't find any that had a long enough unthreaded section. I found the quick release pins on McMaster and decided that they should be plenty strong. I couldn't foresee the pin being pulled loose like it was. I'll have to come up with a more foolproof method.

 

[ChrisAttebery]

Here's the video from Sunday's flight:

[YOUTUBE]MCENpKaTClA[/YOUTUBE]

 

[Dad Man Walking]

Really sorry about the result on Sunday. But take heart in the fact that because you are willing test new ideas and boldly go where no man has gone before, you have taught us a whole lot about a whole lot of things:

(1) That Punisher is a crazy rocket. It's itching for you to rebuild it minimum diameter (since you you may have lost the motor case anyway).

(2) You have crazy build skills. Your motor mount looked better than my finished rockets!

(3) The way you are handling the setbacks is modeling the behaviors I would like to pass on to my kids...it's easy to be graceful when you're ahead. Grace under pressure is the real test of character. Thank you so much for that.

(4) On my own L3 project (just underway) I'll use different search terms for the hardware at McMaster-Carr. I'll search for "really freakin' hard to get off" pins instead of the QR ones (Sorry, I had to do that. It was a hanging curve...somebody had to swing at it.)

Good luck with the rebuild and next (successful) cert flight.

 

[kevinkal]

Excellent video. Love the data overlay. Dashware?

 

[djs]

Great video! (other than the whole "losing the booster" part). What did you use for your drogue chute?

 

[ChrisAttebery]

Cliff?

1. Thanks, but 98mm is way out of my budget right now. I really like the 75mm motors anyway.

2. Ahhh, you're making me blush. :blush:

3. I've just come to realize that in the end it's just a hobby. So I lost a booster and I didn't get my L3. That means I have to/get to build a new booster, have to/get to fly another M, and I didn't get a piece of paper that says I can fly more Ms. The only real letdown is that I may have lost the case and booster permanently.

4. Yes, do a search for PITA pins or something along those lines. :wink:

I have a couple ideas for replacing the pins. I'll dig into that soon.

Really sorry about the result on Sunday. But take heart in the fact that because you are willing test new ideas and boldly go where no man has gone before, you have taught us a whole lot about a whole lot of things:

(1) That Punisher is a crazy rocket. It's itching for you to rebuild it minimum diameter (since you you may have lost the motor case anyway).

(2) You have crazy build skills. Your motor mount looked better than my finished rockets!

(3) The way you are handling the setbacks is modeling the behaviors I would like to pass on to my kids...it's easy to be graceful when you're ahead. Grace under pressure is the real test of character. Thank you so much for that.

(4) On my own L3 project (just underway) I'll use different search terms for the hardware at McMaster-Carr. I'll search for "really freakin' hard to get off" pins instead of the QR ones (Sorry, I had to do that. It was a hanging curve...somebody had to swing at it.)

Good luck with the rebuild and next (successful) cert flight.

 

[ChrisAttebery]

Thanks Kevin. Yes, its DashWare.

Excellent video. Love the data overlay. Dashware?

 

[ChrisAttebery]

Thanks. It was a Fruity Chutes 15" elliptical drogue. I had used a 24" before and it fell too slow IMHO. The 15" chute let it fall at around 75fps.

Great video! (other than the whole "losing the booster" part). What did you use for your drogue chute?

 

[Worsaer]

I've just come to realize thatin the end it's just a hobby. So I lost a booster and I didn't get my L3. That means I have to/get to build a new booster, have to/get to fly another M, and I didn't get a piece of paper that says I can fly more Ms.

Being in the same boat, I realized there's nothing stopping me from buying more M's - it's just that I can only buy one at a time. Realistically, I don't see myself buying more than one at a time anyway...

 

[ChrisAttebery]

One other thing I've learned. Don't fly anything that you can't afford to lose. It's only a matter of time. This came from flying rockets and RC planes. There's only two types of each: those you've crashed and those you haven't crashed YET.

 

[HaackIt]

That was a bummer - it was a beautiful rocket and the up was awesome.


- Ryan R.

 

[ChrisAttebery]

Thanks Ryan.

 

[Reinhard]

4. Yes, do a search for PITA pins or something along those lines. :wink:

I have a couple ideas for replacing the pins. I'll dig into that soon.

Have you considered ball lock pins? They need a bit more room, but should be much harder to lose be accident.

Reinhard

 

[ChrisAttebery]

I looked at the bulkhead and pin this morning. I have a really hard time believing that the shock cord managed to pull the pin free. I think I just didn't get it seated all the way.

Anyway, I think I'm going to replace them with clevis pins that have a cotter pin on one end and a head on the other. It will be more secure and there shouldn't be any doubt that the pin will stay in place once the cotter is installed.

 

[farsidius]

I looked at the bulkhead and pin this morning. I have a really hard time believing that the shock cord managed to pull the pin free. I think I just didn't get it seated all the way.

Anyway, I think I'm going to replace them with clevis pins that have a cotter pin on one end and a head on the other. It will be more secure and there shouldn't be any doubt that the pin will stay in place once the cotter it installed.

View attachment 303676

I built my Punisher's alt bay using your aluminum bulkheads - i really like the low profile. It's flown 3 times and I think your original pins seem to stay put really well. While it's likely that yours didn't get seated all the way, using one of these with a cotter pin looks like it might be a bit more secure.

-brant

 

[NateLowrie]

I looked at the bulkhead and pin this morning. I have a really hard time believing that the shock cord managed to pull the pin free. I think I just didn't get it seated all the way.

Anyway, I think I'm going to replace them with clevis pins that have a cotter pin on one end and a head on the other. It will be more secure and there shouldn't be any doubt that the pin will stay in place once the cotter it installed.

View attachment 303676

Just out of curiosity, why won't a 10-32 screw that's threaded all the way through work? Are you worried about the thread abrading the harness?

 

[ChrisAttebery]

That was exactly my concern.

Just out of curiosity, why won't a 10-32 screw that's threaded all the way through work? Are you worried about the thread abrading the harness?

 

[patelldp]

That was exactly my concern.

Slipping some of this over the span that your shock cord bears on will alleviate that concern: https://www.mcmaster.com/#8527k335/=14oz86g

That said, remember that a 10-32 screw is much much much stronger axially than radially. The functional bearing material is the inner diameter of the cylinder (the valleys of the thread), not the 3/16" OD (the peaks of the threads). A pin arrangement will be much stronger.

 

[PokerJones]

That was exactly my concern.

The clevis pin looks like the easiest fix for a secure attachment point, although if you wanted to go with the 10-32 screw you could use an aluminum sleeve to protect the harness from the threads.

 

[NateLowrie]

That was exactly my concern.

I have mitigated that concern in the past by filling the spaces between the threads with thickened epoxy to essentially turn it into a shoulder bolt.

Two other options to try:

• A shoulder bolt like https://www.boltdepot.com/Shoulder_bolts_Allen_Stainless_steel_18-8_1_4_shoulder_(10-32_thread).aspx
• Using a nylon spacer over a standard 10-32 screw https://www.boltdepot.com/Spacers_Nylon_white_10.aspx

 

[ChrisAttebery]

The pins are stronger than a 10-32 screw and they are relatively cheap. They cost about 1/3 of what the quick release pins do.

 

[ChrisAttebery]

Here's the data from my flight on Sunday:

 

[kevinkal]

With that information, you could extrapolate where the booster with drogue landed... perhaps send this information to John before he departs to search for his twitch this weekend?

 

[ChrisAttebery]

I'm way ahead of you Kevin. The booster was falling slower than the payload bay. It should have been carried farther by the wind. In my opinion it is East of the wash in the red box on the picture. I sent this picture to James so he could forward it to Mr. Maddox. If it doesn't show up soon I might have to take a drive over there myself.

 

[kevinkal]

I'm way ahead of you Kevin. The booster was falling slower than the payload bay. It should have been carried farther by the wind. In my opinion it is East of the wash in the red box on the picture. I sent this picture to James so he could forward it to Mr. Maddox. If it doesn't show up soon I might have to take a drive over there myself.

View attachment 303800

Looks good. I hope it's found soon. I noticed that there was an upper layer of air that was blowing from the West South West, roughly 60 to 80 degrees to the winds nearer the ground which were blowing from the South. The position plots you have confirm that. Blue direction of winds aloft, and green direction nearer ground level.
Depending on how much slower the booster fell after the pin released, I wonder if it could be further East. Are you able to discern where in the tracking plot the separation occurred?
I almost didn't post this, as its adding complexity, but I thought it would make a good discussion.

 

[kevinkal]

View attachment 303796

View attachment 303794

View attachment 303800

From the video and data plot, it looks like the pin let go around 11,750'. In the tracking plot, the first bend downward of the blue trace looks to be at about 11,750'. At the point of separation, the payloads downward velocity and thus downward angle in the tracking plot increased. However, the booster section is now the only thing connected to your drogue. I'm guessing that the booster/drogue fell slower after the pin released the payload. (Sorry if I'm stating the obvious here!, just trying to be clear.) Thus, extrapolating a trajectory with less descent rate from the blue track where the separation occurred makes me wonder if it could be further east and north.

 

[ksaves2]

Shoot Chris, At least it was a component failure and not a "stupid" failure I managed to do like this:

[video=youtube;3JRnwRA6Wx0]https://www.youtube.com/watch?v=3JRnwRA6Wx0[/video]

Kurt Savegnago

 

[ChrisAttebery]

It was pretty close, I failed to ensure that the quick release pin was seated all the way through the lug.

 

[HaackIt]

It was pretty close, I failed to ensure that the quick release pin was seated all the way through the lug.

Want to know a secret? I brought my minimum diameter rocket back from the pad since my backup electronics weren't arming. As I set it down on the table to do the investigation I found the nuts/washers that hold my electronics bay together right there... on the table...

I've never been so happy to have problem with my electronics.