rharshberger
Well-Known Member
Balsa Machining Service C300-4, The T300 is the same as Estes 3" and the C300-4 is a 4" long coupler of the proper diameter.I was considering this mod. Who makes the appropriately sized coupler tube?
Balsa Machining Service C300-4, The T300 is the same as Estes 3" and the C300-4 is a 4" long coupler of the proper diameter.I was considering this mod. Who makes the appropriately sized coupler tube?
You can buy 3 inch tubes and couplers direct from Estes or Balsa machineI was considering this mod. Who makes the appropriately sized coupler tube?
My son and I did this with his Estes V2. Had no problem with the flight. I don't think the wrong spacer would cause the BD to lawn dart.I accidentally did this exact same thing a couple of weeks back. I have a old "D" BigDaddy and the new "E" model. Not thinking, i grabbed the newer "E" model and stuck a D12-3 in it and prepped it for launch. The flight went perfect with no issues. I didn't notice my mistake until I tried to remove the motor and it was stuck well up into the motor tube.... Oh well. No harm done but lesson learned.
The problem is, this formula does not take into consideration the VOLUME of the rocket body. If you have a body tube with an internal volume of 100 cubic inches, and one with an internal volume of 200 cubic inches, it takes a lot more BP in the ejection charge to pressurize the bigger tube to the same 15 psi. It's been noted the ejection charge in composite motors is easy to adjust. Not so much with what may be questionable amounts in Bp motors.I think you are on to the right track here, but maybe not for the reason you think.
I fool around with swaging bullets which involves a hydraulic press pushing lead and copper together in a hardened steel die. Even though the die is big, and the steel is strong, you can crack them if you don't know what you are doing.
The ejection charge in a rocket is not dissimilar from a hydraulic press system, main difference is the hydraulics in a rocket is powered by an explosion and the compression of air instead of an electric pump and hydraulic oil.
There is a formula that is used to describe this relationship. It is P=F/A, where P is the pressure inside the die, F is the force behind the tight fitting punch and A is the area of the punch. In our rocket case, the P, which is in pounds per square inch is the ejection charge pressure in the tube before the nose cone comes off, F is the force against the base of the nose cone and A is the area of the base of the nose cone. Since the ejection charge is set, say at 15 psi (or whatever reasonable number you want to use), we rearrange the formula to be F= P*A
Solving for the Big Daddy, the force on the nose cone would be 15(Pi*1.5^2) = 106 pounds
Solving for a rocket that is half that size, a 1.6" body tube would be 15(Pi*.8^2)= 30 pounds
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My son and I did this with his Estes V2. Had no problem with the flight. I don't think the wrong spacer would cause the BD to lawn dart.
For my next Big Daddy build I am going to lengthen the shock cord and then put 1/2 gram of BP in a tissue and drop on top of the motor. I have done this for a cluster rocket with a long air frame that flies on 4x D12 motors.
Try this, put a 1/2 a gram on a brick and light it with a torch. That small burst adds to the gas pressure.I have often wanted to test adding additional powder to Estes motors but I’ve never wanted to risk a rocket.
I feel like it would need to be under the clay cap to be compressed and actually explode
Try this, put a 1/2 a gram on a brick and light it with a torch. That small burst adds to the gas pressure.
Just make a pouch using masking tape or paper and put a little black powder and an Estes igniter in it. Seal it up tight. Set it on your driveway or other non-flammable surface. Hook it to a launch controller and back up. Push the button to see what happens.Try this, put a 1/2 a gram on a brick and light it with a torch. That small burst adds to the gas pressure.
I have not flown it yet, but decided to do a bulkhead disc on bottom of the nose cone, attached with JB Weld. I extended the motor tube to within ~1/16” of the disc, to allow recovery gear to be packed easily, and with no wadding.Bear in mind that Estes can't take all the credit for the nc design, north coast had a hand in it too. Big daddy uses the NC Patriot nose. Best mod I've seen was a ply bulkhead attached to the end of the nose
Now sure that I understand how that makes you not need wadding.I have not flown it yet, but decided to do a bulkhead disc on bottom of the nose cone, attached with JB Weld. I extended the motor tube to within ~1/16” of the disc, to allow recovery gear to be packed easily, and with no wadding.
The extension of the blast tube into the NC of my rocket eliminates the need for the dog barf, etc. to protect the chute. The nose cone slides over the extended blast tube so the initial blast should take the NC away. And once it clears the main body tube the gases will go into the atmosphere, not into the body tube. It did require I enlarge the hole in the NC some. In your setup the hot gases will hit the bottom of your disc.I have not flown it yet, but decided to do a bulkhead disc on bottom of the nose cone, attached with JB Weld. I extended the motor tube to within ~1/16” of the disc, to allow recovery gear to be packed easily, and with no wadding.
The extension of the blast tube into the NC of my rocket eliminates the need for the dog barf, etc. to protect the chute. The nose cone slides over the extended blast tube so the initial blast should take the NC away. And once it clears the main body tube the gases will go into the atmosphere, not into the body tube. It did require I enlarge the hole in the NC some. In your setup the hot gases will hit the bottom of your disc.
I do wonder how much of a suction inside the main body tube is created as the NC leaves the main body. But the fit of my disc is not exact and will allow some gases to bypass the disc as it travels up lessening the suction effect of an expanding volume with a set amount of gas. In my 1 launch it seemed to work as planned, although my choice of the C11 size rocket was not sufficient to carry it high enough for the chute to fully deploy. The next will be with the E12-6 motor.
I don't know if your setup will over time burn a hole into the disc or not. I'm interested in how it turns out for you though. Good luck and let us know please.
Don
after 195 replies, no big daddy for me
I have, and I thank those of you who have faced it for sharing your wisdom.Learn from our misfortune
Your statement about how effective the ejection blast will be is based on the cross section AREA of the ejection tube. But the cross sectional surface area is not the main factor that will move the NC off the main tube. It is the PRESSURE contained in the rocket before the NC separates from the Body Tube. And that pressure is not reduced by not having a solid seal between the NC hole and the ejection tube.If you assume that you have something approximating a seal between the interior of the nose cone and the main body tube, then you have reduced the effective area the gases can work against to the OD cross section of the stuffer tube. So that's a first approximation.
In reality, you don't have much of a seal between the interior of the nose cone and the main body tube, so you're just using the labyrinth between the interior of the nose cone and the main body tube as a kind of baffle. The pressure inside the nose cone is pushing against the OD cross section of the stuffer tube, and the gas that escapes is pushing against the donut between the ID of the BT and the diameter of the hole you cut in the bottom of the nose cone. Once the nose cone moves far enough to open up the wedge, it basically uncorks the BT at that point and all you have left is the reduced and rapidly bleeding down pressure inside the nose cone pushing against the OD cross section of the stuffer tube
I don't believe that will provide nearly as positive an ejection as simply making the shoulder of the nose cone full diameter all the way until it ends, so it has a "seal" as good as its friction fit in the BT all the way until it uncorks, and then it is separated.
I like mine- always a great flight on a D12.It really is a great rocket.
The recovery gear is down between motor tube and body tube, it never feels the direct effect of the blast. I’ve done this on another squat rocket, which had “typical“ full base on shoulder. Just leaves some soot on the nose cone base.Now sure that I understand how that makes you not need wadding.
I hope to test mine again with an E12-6 soon. I modded mine so that it is now a 40" rocket, a Bigger Daddy. A C11-3 motor didn't get it high enough so maybe the E size will do better. If it's too strong I'll try a D size.I like mine- always a great flight on a D12.
Have you done a sim for it? I wonder if 6 sec delay might be too long. I use D12-3 with mine but I've seen them launched with D12-5 so maybe 6 sec is ok. I think it will fly OK but might need a long rail or rod for launch.I hope to test mine again with an E12-6 soon. I modded mine so that it is now a 40" rocket, a Bigger Daddy. A C11-3 motor didn't get it high enough so maybe the E size will do better. If it's too strong I'll try a D size.
Don
I did an OPEN ROCKET sim and posted on the thread I started here. I was my first attempt at OR. I'm sure I did not do it correctly but I think it came out looking like my Bigger Daddy.Have you done a sim for it? I wonder if 6 sec delay might be too long. I use D12-3 with mine but I've seen them launched with D12-5 so maybe 6 sec is ok. I think it will fly OK but might need a long rail or rod for launch.
Not sure if you were responding to my last post or someone else. My Bigger Daddy used to be a Big Daddy kit. But after it took it on the nose so to speak, I cut off the damaged section and made it 40" long into my BIGGER Daddy.No Kit should require any mods to fly safely, that defeats the main benefit of buying a kit.
As you can see in the posts above, the E12 was too powerful so a D12-4 may be the ticket on my next launch.I like mine- always a great flight on a D12.
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