Wild Child Build - Test Round
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GregGleason
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That's a good idea, Rex.
After I placed the retainer on, I think I gave it a little twist to spread it some. Hopefully what I did was good enough for it work reliably.
Greg
blackjack2564
Crazy Jim's Gone Banana's
GG...you seem to be having a lot of fun trying new ideas & experimenting with stuff on this build. Good for you! That's what it's all about, having fun.
By the way... one of the best looking versions I've seen.
By the way... one of the best looking versions I've seen.
GregGleason
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Thank you CJ, for the kind words!
This is a fun kit to try things on, even if they don't work out, the design is very forgiving.
Greg
GregGleason
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On for more work on the PVC.
Time to tap the holes for 1/4"-20. I used good ol' 3-IN-ONE as the cutting fluid for the tapping process.
The tapping process went pretty quick, as PVC is a fairly soft material. I didn't take too much care on guiding it during tapping, but more on that later.
It was time time to cut the 1/4"-20 threaded Delrin.
I cut six pieces to about 9mm lengths. I just used a razor saw and the hobby miter box, and this process went fairly quickly as well.
I added the first piece of threaded Delin into the tapped PVC, and it seemed like it fit well enough.
Then the rest of the pieces were added to the PVC.
I then placed the unit on the scale to see what the unit weighs.
It came in at 23.9 grams.
Greg
Time to tap the holes for 1/4"-20. I used good ol' 3-IN-ONE as the cutting fluid for the tapping process.
The tapping process went pretty quick, as PVC is a fairly soft material. I didn't take too much care on guiding it during tapping, but more on that later.
It was time time to cut the 1/4"-20 threaded Delrin.
I cut six pieces to about 9mm lengths. I just used a razor saw and the hobby miter box, and this process went fairly quickly as well.
I added the first piece of threaded Delin into the tapped PVC, and it seemed like it fit well enough.
Then the rest of the pieces were added to the PVC.
I then placed the unit on the scale to see what the unit weighs.
It came in at 23.9 grams.
Greg
GregGleason
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Yes, Mason, I suppose that does need a bit of an explaination.
I am somewhat of a piston advocate, since I have had more than one recovery issue that could have likely prevented the parachute not quite leaving the airframe. Pistons provide a positive force, usually making sure everything ahead of it will indeed leave the airframe. Usually. Pistons, typically have a down side, in that they are prone to bind or seize up in the airframe.
So, I began thinking about how to mitigate that possibility. I began to rethink the whole piston idea, and see if I could improve upon the classic design. Early on, I considered tracks or guides that a piston could perhaps ride, but that seemed too much trouble and not very practical. What was needed was a way to not be so prone to binding. Well, what if there was a way to minimize the points of contact inside the airframe? In addition, what materials are available that have a low coefficient of friction, yet robust enough to be literally shot out like a bullet. In addition, it would help if the system were adjustable, at least to some degree as well.
So after a lot of thought, I came up with this idea. It involved 3-point contact at each end. The "contacts" chosen were made of Delrin, which are already used in rocketry as rail buttons. Delrin has a low coefficient of friction, and has proved its usefulness on thousands of rocket flights. It is threaded so that it can be adjusted in or out fairly easily. PVC is useful in that it is easily tapped and strong enough under compression for this test. In the future I would like a lower density material so that it isn't as heavy, but it should work well enough for a "proof of concept" application. But once that mass gets moving, it's going to go like a freight train and push the recovery system out.
What is depicted is not the finished product. It will have a fore and aft cap, along with a place to connect to the recovery harness.
So what you see is the Piston-inator Mark 1 (which I hope will catch on in the entire tri-state area). Will it work? I hope so, but it's the Test Round, so we shall see.
Greg
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cbrarick
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What about adding a little extra BP if it's marginal? Of course, there's the "don't make it too tight of a fit" and "always ground test" things...
If you like it, go for it, but it seems like an uber-complicated and heavy fix to a fairly minor problem.....
BTW, how does your little slice of heaven effect the CP-CG of your rockets?????
If you like it, go for it, but it seems like an uber-complicated and heavy fix to a fairly minor problem.....
BTW, how does your little slice of heaven effect the CP-CG of your rockets?????
GregGleason
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Fair questions. Let me see if I can take these one at a time.
I could add more BP, but the whole point is that with a piston you can use less BP, with a higher margin of success.
It may seem like a minor problem. But if the recovery system doesn't come out, that's potentially bad news for the rocket. Then there is what the rocket may hit at landing. Which is potentially bad news for folks on the ground. I have had recovery failure on rockets without pistons, but I have never had a deployment failure on rockets with them. We pick and choose where we move the risk mitigation points on our rockets.
As far as the level of complication goes, the complexity was more in the thinking it through. And I'm still thinking it through. It is a challenging mental exercise. The device itself is certainly less complex than designing an av bay. This is essentially a slug in a barrel, and all I'm doing is thinking about ways to further improve performance and reliability.
I expect no real change. Since the CP is affected by the external rocket geometry, there is no real change there. The Piston-inator is planned to "sit" at the nominal CG of the rocket or a little higher up in the airframe. There will be small wires that extend from the bottom of the piston that will rest on the forward CR.
I hope that addresses some of your questions.
I understand that this is not for everyone. For most it will be filed under, "Whatever floats your boat", and that's ok by me. But for me it is something I want to explore.
Greg
I could add more BP, but the whole point is that with a piston you can use less BP, with a higher margin of success.
It may seem like a minor problem. But if the recovery system doesn't come out, that's potentially bad news for the rocket. Then there is what the rocket may hit at landing. Which is potentially bad news for folks on the ground. I have had recovery failure on rockets without pistons, but I have never had a deployment failure on rockets with them. We pick and choose where we move the risk mitigation points on our rockets.
As far as the level of complication goes, the complexity was more in the thinking it through. And I'm still thinking it through. It is a challenging mental exercise. The device itself is certainly less complex than designing an av bay. This is essentially a slug in a barrel, and all I'm doing is thinking about ways to further improve performance and reliability.
I expect no real change. Since the CP is affected by the external rocket geometry, there is no real change there. The Piston-inator is planned to "sit" at the nominal CG of the rocket or a little higher up in the airframe. There will be small wires that extend from the bottom of the piston that will rest on the forward CR.
I hope that addresses some of your questions.
I understand that this is not for everyone. For most it will be filed under, "Whatever floats your boat", and that's ok by me. But for me it is something I want to explore.
Greg
GregGleason
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At the club launch yesterday, I was finally able to put Test Round into the air. But it wasn't easy.
I was out of my homebrew initiators, so I had to make a new batch. I made my last batch almost two years ago (between the Texas drought and other commitments I hadn't been flying much). They had a +90% success rate. So I made a new batch, following the old recipe (or so I thought). I did a non-motor test on one of them, and it lit.
So I loaded it with an AeroTech 24mm RMS E18-4W, using an Aero Pack 29/24 adapter. It fit like a glove. I chose the E18 because I wanted to get an idea of how high this will fly before I started to amp up on the thrust and impulse.
With hope in my heart for a successful maiden launch, it was at the pad with a launch weight of 575 grams.
When it came time to launch, there was continuity, the button was pressed. Nothing. No sound. No smoke. Nothing. I took it off the rod and went back to swap out the initiator. Take 2. Same result. Out of desperation, I found a Copperhead and placed it at the top of the propellant grain. Racked it and waited for the RSO's countdown. Tell-tale smoke started from the bottom and then all of sudden took off. It was a nice ride up. Then it came down. And down, and down (the red cap was on, right?). Finally, the event happened and the 18" Top Flight chute deployed. It landed in the soft grass about 50 to 75 yards away from the pad. Woohoo! I then sent one of my children out to recover it.
A cursory post-flight inspection revealed no damage.
So, I need to go back to "Initiator School", and do some delay grain surgery to trim a second or two off of the delay.
I wish I had some pictures of the flight. Maybe next time.
Greg
I was out of my homebrew initiators, so I had to make a new batch. I made my last batch almost two years ago (between the Texas drought and other commitments I hadn't been flying much). They had a +90% success rate. So I made a new batch, following the old recipe (or so I thought). I did a non-motor test on one of them, and it lit.
So I loaded it with an AeroTech 24mm RMS E18-4W, using an Aero Pack 29/24 adapter. It fit like a glove. I chose the E18 because I wanted to get an idea of how high this will fly before I started to amp up on the thrust and impulse.
With hope in my heart for a successful maiden launch, it was at the pad with a launch weight of 575 grams.
When it came time to launch, there was continuity, the button was pressed. Nothing. No sound. No smoke. Nothing. I took it off the rod and went back to swap out the initiator. Take 2. Same result. Out of desperation, I found a Copperhead and placed it at the top of the propellant grain. Racked it and waited for the RSO's countdown. Tell-tale smoke started from the bottom and then all of sudden took off. It was a nice ride up. Then it came down. And down, and down (the red cap was on, right?). Finally, the event happened and the 18" Top Flight chute deployed. It landed in the soft grass about 50 to 75 yards away from the pad. Woohoo! I then sent one of my children out to recover it.
A cursory post-flight inspection revealed no damage.
So, I need to go back to "Initiator School", and do some delay grain surgery to trim a second or two off of the delay.
I wish I had some pictures of the flight. Maybe next time.
Greg
