Big Daddy became a Lawn Dart

KenECoyote · Jul 31, 2015

How about just adding on a round flat bulkhead/disc? You can epoxy or screw it on, drill two holes for the shock cord attachment (or screw eye) and it negates the problem of ejection gases escaping through the shoulder and should make the nose cone act like a piston. Seems like a simple, easy, quick fix (if the angled shoulder is the problem) and you take up very little space and don't reduce the shoulder.

Bat-mite · Jul 31, 2015

KenECoyote said:
How about just adding on a round flat bulkhead/disc? You can epoxy or screw it on, drill two holes for the shock cord attachment (or screw eye) and it negates the problem of ejection gases escaping through the shoulder and should make the nose cone act like a piston. Seems like a simple, easy, quick fix (if the angled shoulder is the problem) and you take up very little space and don't reduce the shoulder.

Simplest method I can think of. Nice.

rharshberger · Jul 31, 2015

Bat-mite said:
Check out the picture here: https://rocketrycenter.com/showthread.php?tid=104&pid=862#pid862

Better yet even, I took the picture originally (thanks for posting the link Bat-Mite), the BMS nose cone has about a 2" shoulder with the sloped section cut off and the Estes shoulder minus the sloped section is about 1-1/8"

sheepdog · Jul 31, 2015

KenECoyote said:
How about just adding on a round flat bulkhead/disc? You can epoxy or screw it on, drill two holes for the shock cord attachment (or screw eye) and it negates the problem of ejection gases escaping through the shoulder and should make the nose cone act like a piston. Seems like a simple, easy, quick fix (if the angled shoulder is the problem) and you take up very little space and don't reduce the shoulder.

This week end I will start working on this...This appears to be an easy fix...I will cut it directly at the top of the slant on the aft of the nose cone, epoxy a bulkhead with Eye screw, and I should be good to go....

Once I modify this kit I will let everyone know what happens on the launch....Again Thanks everyone for the suggestions.

sheepdog · Jul 31, 2015

John,
DO you go to the NARHAMS launches in Mt. Airy? If so we may have met. I noticed your in Maryland I am in Clarksburg.

Thanks

Nick@JET · Aug 1, 2015

Sorry if this has been asked,
Has anyone tried adding some BP to the top of an D or E motor, barfing and taping it for more ejection pressure?

rharshberger · Aug 1, 2015

Nick@JET said:
Sorry if this has been asked,
Has anyone tried adding some BP to the top of an D or E motor, barfing and taping it for more ejection pressure?

The problem with that is the clay cap, which when it bursts will scatter much of the additional BP. The extra BP will mostly ignite, but it won't be in a concentrated mass so it can produce a large volume of gas quickly, it will produce some gas but not enough to be significant, IMO. The better way to do it would be to remove the clay cap, add the BP, barf it and tape it, then it would function like any other ejection charge, HOWEVER this definitely constitutes modifying a motor which is against the Model Rocket Safety Code.

ksaves2 · Aug 1, 2015

rharshberger said:
The problem with that is the clay cap, which when it bursts will scatter much of the additional BP. The extra BP will mostly ignite, but it won't be in a concentrated mass so it can produce a large volume of gas quickly, it will produce some gas but not enough to be significant, IMO. The better way to do it would be to remove the clay cap, add the BP, barf it and tape it, then it would function like any other ejection charge, HOWEVER this definitely constitutes modifying a motor which is against the Model Rocket Safety Code.

Ok, so join Tripoli and only fly it at a TRA launch. You are 100% correct. It's a motor modification so therefore not flyable at a NAR launch. On the other hand, if one has "no" scruples, do the mod, don't tell anyone and go fly it. :facepalm:

If the motor catos, it's just another cato. If there's a stability problem, that's not the motors fault. An ejection charge mod is not likely to cause an issue but if you're easily guilt ridden, join TRA. Kurt :wink:

ttbit · Aug 2, 2015

Whoa. I thought this was my thread re-born, at first. Almost exactly a year ago, I ran into these issues. Extending the engine tube through the nose cone does not work as good as you would expect either. As soon as that cone gets to the shoulder, the good gases escape and the fire stays inside making a good mess of things. Adding more black power should cause more melt and issues.

I have 2 replacements here that I have not built yet. I plan on getting rid of the shoulder. My issues were using D12-3.

I took my air compressor nozzle and aimed it through a spent engine for testing of ejection. An obvious problem exists. I can blow through my BT-80 rocket of 24" w/baffle with almost no air pressure and the cone goes flying. 80 psi is not enough to get the BD nose going. Gets to the shoulder and stops.

Use some air for testing before launching after mods.

KenECoyote · Aug 2, 2015

I've had mine for half a year, but finally got to launch it today. Scheme is similar to the Quest Lil' Grunt (I figured this can be "Big Grunt" and I was thinking of using a MDRM kit for a Mega Grunt!

). Used a D12-3 and it went up nice, event was early and chute had a bit of fusing near the anchors, but it recovered fine. Of note is that I used a fiberglass heat shield...maybe that helped push everything out.

Tiny Daddy pics...

K'Tesh · Aug 3, 2015

ttbit said:
Whoa. I thought this was my thread re-born, at first. Almost exactly a year ago, I ran into these issues. Extending the engine tube through the nose cone does not work as good as you would expect either. As soon as that cone gets to the shoulder, the good gases escape and the fire stays inside making a good mess of things. Adding more black power should cause more melt and issues.

I have 2 replacements here that I have not built yet. I plan on getting rid of the shoulder. My issues were using D12-3.

I took my air compressor nozzle and aimed it through a spent engine for testing of ejection. An obvious problem exists. I can blow through my BT-80 rocket of 24" w/baffle with almost no air pressure and the cone goes flying. 80 psi is not enough to get the BD nose going. Gets to the shoulder and stops.

Use some air for testing before launching after mods.

Perhaps a Youtube video of someone doing this experiment would be useful. Might make a good Science Fair project for a kid. Might even be enough to get the Estes to recognize the problem and modify the nosecone. They do respond to customer concerns. My issue with the PortaPad E was addressed.

JERRYR708 · Aug 3, 2015

K'Tesh said:
Perhaps a Youtube video of someone doing this experiment would be useful. Might make a good Science Fair project for a kid. Might even be enough to get the Estes to recognize the problem and modify the nosecone. They do respond to customer concerns. My issue with the PortaPad E was addressed.

I just upgraded to the PortaPad E when my standard Electron Beam pad burned up. What changes did they make to improve the PortaPad E?

K'Tesh · Aug 3, 2015

JERRYR708 said:
I just upgraded to the PortaPad E when my standard Electron Beam pad burned up. What changes did they make to improve the PortaPad E?

There's now a brace that is glued the underside of the base that prevents the legs from folding under the weight/pressure of a larger rocket, and they created legs to stand the blast plate off of the base to prevent melting issues, as well as having the swivel now located underneath the blast plate instead of on top of it (fire/melting problem).

ttbit · Aug 3, 2015

K'Tesh said:
Perhaps a Youtube video of someone doing this experiment would be useful. Might make a good Science Fair project for a kid. Might even be enough to get the Estes to recognize the problem and modify the nosecone. They do respond to customer concerns. My issue with the PortaPad E was addressed.

I'll do that when testing the changes for a comparison. Not exactly sure when that will be.

jqavins · Aug 10, 2015

dgreger said:
I fly mine exclusively on CTI 24mm, it has 4oz of lead in the nose, and I cut the bottom of the NC off and epoxied a bulkhead in creating more space for the chute/nomex blanket. It has 12 flights on it so far including 7 on the F240 Vmax, worst thing to happen to it so far is a tangled chute.

I built my first one stock, then did almost the same as you on my second one, except that it flies on CTI 29mm 3 grain. I did my L1 flight with it.

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