eliminating ejection

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watermelonman

watermelonman

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I want to try a series of low power experiments without ejection charges. I will need the delay and tracking portion of motor burn, so sadly the simple solution of buying booster motors is no good.

Could I try plugging the tops of motors with epoxy? This might require motors with enough of a gap up top to get the epoxy in, but should that suffice for the amount of force? Would the charge simply spew out the nozzle or could it get more destructive than that?
 
That force is going to go somewhere. With what you are proposing, I think you have the potential of creating an epoxy bullet or a bomb. I guess the force could be directed out the nozzle if the epoxy plug holds and the motor wall holds.

Without knowing the nature of your experiments, would it be possible to vent the force of the ejection charge and still be able to find out what you need to?
 
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Venting would be perfect! Except, all the ways I think of offhand would kind of mangle the rocket and leave a big open port on the side. What were you thinking?
 
What about an internal baffle where the upper chamber has 3 or 4 vent holes through the side. The holes are shrouded on the exterior by a reinforced skirt. Or if you could find a hollow-conical nose cone where the base of the cone was larger than the shoulder and body tube, you could drill vent holes in the base and glue the nose cone in place. I don't know is such a NC exists. Just a couple of thoughts.
 
If you're using a body larger than minimum diameter, punch a few holes in the centering rings of the motor mount or if you are using the 2050 rings (the green ones in typical Estes kits), just cut out a couple of sections of the ring and the charge will vent out the back.
 
Is this a glider of some sort? Or are you just planning on spiking them into the ground?
 
Just to state the obvious (like any stick in the mud would do), paragraph 2 out of the NAR safety code:
Motors. I will use only certified, commercially-made model rocket motors, and will not tamper with these motors or use them for any purposes except those recommended by the manufacturer.
Click to expand...
An epoxy plug would constitute "tampering". If you're testing on your own and not at a sanctioned club launch, you're free to do whatever you want. If anything goes awry, though, you won't be covered by insurance (that's if you're a NAR member).

Let us know more of what you're trying to do and there may be some other solutions. So far, some sort of vent seems to be the best option.
 
If you are referring to Estes motors, just scrap out the clay cap and BP. I do it all the time for saucers. I have poured epoxy into where the clay cap was and never had any issues.
 
+1 on venting out the back, unless it is MD

I think kicking the case out the back is also now against NAR. Could you use rear ejection, and have the motor mount come down on a separate streamer? Guess it depends on what you are trying to accomplish, as others have questioned.
 
It may be more in the mid power range, but what about Aerotech 18mm and 24mm reloads and just don't put in the ejection charge?

-Hans
 
Mr Rocket said:
+1 on venting out the back, unless it is MD

I think kicking the case out the back is also now against NAR.


Absolutely NOT TRUE! motor casings can be ejected at any sanctioned NAR sport Launch. The practice is ONLY banned in NAR Competition Contests.

I'll also second the fact the adding epoxy to a motor is a violation of the NAR SAFETY Code, "Altering a motor". if your flying alone on your own property you can do what you will, but if flying on public property or at any NAR range it practice is forbidden.

I'll third Venting out the rear of the model by adding holes to the centering ring or cutting out parts of the centering rings.

That Said; I'd also like to know what you type of model you are "testing" as some form of recovery is required by the safety code. If your not flying under the safety code whatever your doing shouldn't be done in the first place.
Please don't endanger the rest of the hobby by attempting to flying something that obviously should not be flown. Think before you fly!
Click to expand...
 
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Ya know, if you don't destabilize the rocket (since no ejection charge or you eject the casing out the back) or provide for some sort of safe recovery, then you have a stable missile heading straight down, nose cone first. Again :facepalm::facepalm:
 
HHaase said:
It may be more in the mid power range, but what about Aerotech 18mm and 24mm reloads and just don't put in the ejection charge?

-Hans
Click to expand...

I love that idea but the weakest reloads available in 18mm are still D class, which will send these experiments way too high.
 
Micromeister said:
Mr Rocket said:
+1 on venting out the back, unless it is MD

I think kicking the case out the back is also now against NAR.


Absolutely NOT TRUE! motor casings can be ejected at any sanctioned NAR sport Launch. The practice is ONLY banned in NAR Competition Contests.

I'll also second the fact the adding epoxy to a motor is a violation of the NAR SAFETY Code, "Altering a motor". if your flying alone on your own property you can do what you will, but if flying on public property or at any NAR range it practice is forbidden.

I'll third Venting out the rear of the model by adding holes to the centering ring or cutting out parts of the centering rings.

That Said; I'd also like to know what you type of model you are "testing" as some form of recovery is required by the safety code. If your not flying under the safety code whatever your doing shouldn't be done in the first place.
Please don't endanger the rest of the hobby by attempting to flying something that obviously should not be flown. Think before you fly!
Click to expand...

Of course! This is for testing recovery without motor events. I am still bringing it down with a parachute but I want much finer control than stabbing around at the number of seconds after thrust. I will post more details and results as I get further along.

R2RAllan said:
Ya know, if you don't destabilize the rocket (since no ejection charge or you eject the casing out the back) or provide for some sort of safe recovery, then you have a stable missile heading straight down, nose cone first. Again :facepalm::facepalm:
Click to expand...

Yes, I realize that. No need for the face palms.
Click to expand...
 
watermelonman said:
Of course! This is for testing recovery without motor events. I am still bringing it down with a parachute but I want much finer control than stabbing around at the number of seconds after thrust. I will post more details and results as I get further along.

Yes, I realize that. No need for the face palms.
Click to expand...

Glad you have it covered! :cheers:

Sounds interesting. Looking forward to reading/seeing the details and results.
 
watermelonman said:
I want to try a series of low power experiments without ejection charges. I will need the delay and tracking portion of motor burn, so sadly the simple solution of buying booster motors is no good.

Could I try plugging the tops of motors with epoxy? This might require motors with enough of a gap up top to get the epoxy in, but should that suffice for the amount of force? Would the charge simply spew out the nozzle or could it get more destructive than that?
Click to expand...


Why don't you just buy a plugged motor rather than trying to do it yourself?

SO.
 
KidShelleen said:
What about an internal baffle where the upper chamber has 3 or 4 vent holes through the side. The holes are shrouded on the exterior by a reinforced skirt. Or if you could find a hollow-conical nose cone where the base of the cone was larger than the shoulder and body tube, you could drill vent holes in the base and glue the nose cone in place. I don't know is such a NC exists. Just a couple of thoughts.
Click to expand...

good idea the venting, if the centering rings are large enough you could drill holes in them to release the charge pressure or just make the motor mount out of four strips of balsa between the motor tube and body tube. approximatly the same area as the motors opening is needed to easily vent the gasses.
 
rharshberger said:
good idea the venting, if the centering rings are large enough you could drill holes in them to release the charge pressure or just make the motor mount out of four strips of balsa between the motor tube and body tube. approximatly the same area as the motors opening is needed to easily vent the gasses.
Click to expand...

Oh, that is a good idea but the nose cone definitely still needs to come off to release my parachute. I would like to keep the motor compartment sealed to as low as possible on the rocket, to leave more payload room for my electronics and various recovery mechanisms.

The side vents with shrouding definitely have potential. How big should vents be, and how much should the shrouding affect flight?
 
watermelonman said:
I had no idea they existed! Who makes them in what sizes?
Click to expand...

Assuming this is what you are looking for (that is, I understand your requirement), here is a link to a UK website that sells them.

https://www.modelrockets.co.uk/shop/motors-consumables/klima-composite-motors-c-28_151.html

I've ordered some but haven't used them yet so can't comment on them. Also, have a look at the aluminium cans that as far as I can see are effectively plugs for motors without a delay.
We had a debate on here recently about these motors. They are new to the UK, I'm not sure they are available in the US though may have been in the past re-labelled as Quest motors.

As you can see the plugged versions are suffixed "-P". For example C6-P, D3-P, D9-P, etc.

Hope that helps.

SO.
 
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Is there some reason why you couldn't let the ejection charge (or booster motor blow-through) separate the rear of the rocket? You could design what would basically be a two-stage rocket with motors in the first stage and just leave the motor mount out of the upper stage (replace with a solid disc bulkhead). You would still need fins on both first and second stages to keep them stable. Just let the upper stage continue coasting upward until your new system takes over. This way you could go ahead and conduct your "new deployment" tests with motors that are probably already available to you?

And about this new deployment system....you have my curiosity peaked, you darned well better come back here and post some test results!!!!! (pretty please!!!!) Is this new system small/light enough to use in low-power rockets like BT20 or BT50? Can it be set up for dual deployment, with an altitude trigger or timer for the second event?
 
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watermelonman said:
I love that idea but the weakest reloads available in 18mm are still D class, which will send these experiments way too high.
Click to expand...

There is a C reload in the 18mm size, no ejection charge. It is designed for boost gliders, so it is a relatively low thrust, long burn motor. It may not work to loft your "experiment."
 
powderburner said:
And about this new deployment system....you have my curiosity peaked, you darned well better come back here and post some test results!!!!! (pretty please!!!!) Is this new system small/light enough to use in low-power rockets like BT20 or BT50? Can it be set up for dual deployment, with an altitude trigger or timer for the second event?
Click to expand...

Hah, do not worry about that! I will definitely be posting pictures and results as it starts coming together. I want it as small as possible but I will have to see what is realistic. I will try working with both altitude and acceleration data.
 

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