"E" Engine Ejection Charge in a BT-80

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

flaperon

Active Member
Joined
Sep 3, 2021
Messages
43
Reaction score
38
Hello all, relative newbie here. After getting back into building and flying since the younger years (35 years ago), I've built about 15 Estes kits this year and have about 60 launches to date. Now, I'm scaling up my favorites. I'm doing a 200% Nike X with 36 inch long BT-80 tube with an "E" engine mount. I'm looking at all of the area in that tube wondering if the ejection charge power will be used up fill all of the volume and be enough to pop the cone. I suppose the solution would be to create and "inner" ejection tube with less volume to help things along. So, is the "E" engine ejection charge up to the task?

Thanks,

Kip
 
I'd put in a stuffer tube and ejection baffle in a coupler; but that's me and the stated opinion has no mathematical or scientific explanation. With a 24mm mount, it's easy to just use a longer length of BT50 and a centering ring farther forward.

Doing something to keep the laundy up front will be a good thing too; or all that mass can shift back on launch, and make for some stability excitement.
 
I'd put in a stuffer tube and ejection baffle in a coupler; but that's me and the stated opinion has no mathematical or scientific explanation. With a 24mm mount, it's easy to just use a longer length of BT50 and a centering ring farther forward.

Doing something to keep the laundy up front will be a good thing too; or all that mass can shift back on launch, and make for some stability excitement.


All good information, thanks. It seems that I have enough tubing and couplers on hand to rig something up.
 
The other option is to have the rocket separate in the middle by putting a bulkhead on/in the bottom of the coupler.
This would also require the laundry to be in the lower portion of the BT, which could cause instability. Best to play with the configurations in a simulator and see what works.
 
Set it up for a mid-body separation with a baffle. A good example for you to look at is the Klima Andromeda rocket on the Apogee Rocket website.
 
I built a QModeling upscale Nike-X kit and flew it at NARAM-49.

It used BT-80 for the body tube and had a complex thru-the-wall fin alignment system.
As I recalled it's mass was 14-16 oz.
The kit had a 24mm motor mount which I thought too small for a model this size.

I used an AeroTech E15-4W motor which gave the model a pretty good flight and the ejection charge was enough to deploy the recovery system.

Launch of Bob Sanford's Q Modeling Mega Nike-X on an AeroTech E15-4W motor.JPG
 
I had the thought that you might want to go with a 29mm mount. I suspect that you are thinking a 24mm Estes black powder motor for it? I don't think that will work too great unless you build very light. I think that you will most likely have to use composite 24mm motors for safe and satisfactory flights.

With 29mm motors you wouldn't have to worry so much about how much extra weight you add by filling spirals, using papered balsa, basswood or ply for fins, changing the coupler to a baffle, using a nylon chute, etc, etc

BTW, LOC has a 2.26 Nike Zeus kit that comes with a 29mm mount and they offer an optional 38mm Mount Zeus – LOC Precision / Public Missiles Ltd.

Just my 2 pennies,
-Bob
 
I had the thought that you might want to go with a 29mm mount. I suspect that you are thinking a 24mm Estes black powder motor for it? I don't think that will work too great unless you build very light. I think that you will most likely have to use composite 24mm motors for safe and satisfactory flights.
I would agree completely with everything above. Put a 29mm mount in it; you can always adapt down to 24mm to use an Aerotech E20 or E30 or something.
 
Hello all, relative newbie here. After getting back into building and flying since the younger years (35 years ago), I've built about 15 Estes kits this year and have about 60 launches to date. Now, I'm scaling up my favorites. I'm doing a 200% Nike X with 36 inch long BT-80 tube with an "E" engine mount. I'm looking at all of the area in that tube wondering if the ejection charge power will be used up fill all of the volume and be enough to pop the cone. I suppose the solution would be to create and "inner" ejection tube with less volume to help things along. So, is the "E" engine ejection charge up to the task?

Thanks,

Kip

Kip,

With 36 inches of body tube you're going to need a stuffer tube. If it were my build, I'd add a Stuffer that was 15 inches long. The stuffer tube would stop 3 inches from the top of the first tube. From there I would use a 4 inch coupler and create a baffle. With the 4 inch baffle inserted to the midpoint, you would have 1 inch between the top of the stuffer tube and the bottom of the baffle. Below is an example of what I'm describing.

If you are going to want to fly this on black powder Estes motors, you should consider going to 29mm. If you plan to fly composites then the E30 and F44 will give you tons of power in 24mm.

Demo.jpg
 
Hello all, relative newbie here. After getting back into building and flying since the younger years (35 years ago), I've built about 15 Estes kits this year and have about 60 launches to date. Now, I'm scaling up my favorites. I'm doing a 200% Nike X with 36 inch long BT-80 tube with an "E" engine mount. I'm looking at all of the area in that tube wondering if the ejection charge power will be used up fill all of the volume and be enough to pop the cone. I suppose the solution would be to create and "inner" ejection tube with less volume to help things along. So, is the "E" engine ejection charge up to the task?

Thanks,

Kip
,
You know , I agree just use a long motor mount tube with a extra forward centering ring.
 
Hello all, relative newbie here. After getting back into building and flying since the younger years (35 years ago), I've built about 15 Estes kits this year and have about 60 launches to date. Now, I'm scaling up my favorites. I'm doing a 200% Nike X with 36 inch long BT-80 tube with an "E" engine mount. I'm looking at all of the area in that tube wondering if the ejection charge power will be used up fill all of the volume and be enough to pop the cone. I suppose the solution would be to create and "inner" ejection tube with less volume to help things along. So, is the "E" engine ejection charge up to the task?

Thanks,

Kip
,
You know , I agree just use a long motor mount tube with a extra forward centering ring.
 
Thanks everyone for your input. I have reluctantly decided to cut out the 24 mm mount and install a 29 mm.

I'll install a stuffer tube and baffle also. Stay tuned for a flight report.

Regards,
Kip
 
Thanks everyone for your input. I have reluctantly decided to cut out the 24 mm mount and install a 29 mm.

I'll install a stuffer tube and baffle also. Stay tuned for a flight report.

Regards,
Kip
The stuffer tube to limit the total area is the way to go in larger BT tubes. When I use a BT 80 I keep no larger than 12“ of open space (from the motor mount tube/stuffer tube forward centering ring to the bottom of the nosecone). Plenty of room for up to a 24” chute and still enough eject pressure yo push everything out.
 
I built a Big Bertha with BT80 tubes. I added a baffle at the coupler. I do not have a stuffer tube to reduce internal volume and have successfully launched the rocket with D12 and E9 motors. No problems with ejection. If I ever build another one, I would add the stuffer tube just to be safe.
 
I have an Executioner built stock, similar dimensions to what you are talking about. The last time I launched it on a D12 it did not blow out the chute- the nose cone came off but the chute was left half in the tube. I think this kit should have come with a stuffer tube. I will build one to retrofit into my rocket.

And BTW the Executioner is fairly large and light and with the nose cone dragging along it will fall almost as slowly without a chute as it does with a chute, and if it lands in tall grass it won't have any damage.
 
I have an Executioner built stock, similar dimensions to what you are talking about. The last time I launched it on a D12 it did not blow out the chute- the nose cone came off but the chute was left half in the tube. I think this kit should have come with a stuffer tube. I will build one to retrofit into my rocket.

And BTW the Executioner is fairly large and light and with the nose cone dragging along it will fall almost as slowly without a chute as it does with a chute, and if it lands in tall grass it won't have any damage.

Mine came with a stuffer tube but I didn't feel it was long enough. I extended it to just above the coupler and haven't had any issues in about 8 flights of the Executioner.
 
Mine came with a stuffer tube but I didn't feel it was long enough. I extended it to just above the coupler and haven't had any issues in about 8 flights of the Executioner.
I went out in the garage and looked at my Executioner. It does have a stuffer tube so I don't know why I had an ejection problem recently, maybe a D12 with less than the full ejection charge. I wouldn't trust that much empty volume without a stuffer tube and with stock ejection charge.
 
Throw away any baffles. A single D12 is sufficient to eject a 4" payload rocket. I have done it hundreds of times Loc Ultimate
 
Thanks for all of the input. I did have a successful deployment...at about 100 feet. The total altitude was only about 300' on an E16-4. 585 grams liftoff weight. Total pig. I'm upping my Newton Seconds and learning a lot.
Here's the video with cameraman fail (me). I know to always track it regardless of event but this thing was heading into fenced area and I was distracted.

 
Thanks for all of the input. I did have a successful deployment...at about 100 feet. The total altitude was only about 300' on an E16-4. 585 grams liftoff weight. Total pig. I'm upping my Newton Seconds and learning a lot.
Here's the video with cameraman fail (me). I know to always track it regardless of event but this thing was heading into fenced area and I was distracted.


Thanks..nice flight.
 
I have asked this same question a dozen times and got nothing but snide comments back saying depends on everything. Not very helpful, All I need is the largest volume one can safely use with a 18mm and 24mm motor.
 
I ended up using an extended motor mount tube that runs all the way up to the baffle. One caveat is don't get the 29mm "heavy wall" tube. That stuff is HEAVY.
Here's the X with an F20-4W. Much better performance but I'll be upping the power...
 
Back
Top