ejection for a 38mm minimum dia rocket

[rocketman4h]

I have a Madcow 38mm Mongoose minimum diameter rocket. I hope to fly it in a few weeks. my question is how you all house the bp and igniter in a small rocket like that. All of the cannistors I have found mount to the av bay cap. it is already busy with the holes for the sled, hole for the shocke attachment point and another hole for the ejection wire. It is starting to look like swiss cheese. I also want to keep the weight to a minimum. to boot the charge calculators call to start with a 0.14 grams of bp. That is not much

 

[spigalau]

Some of our locals use heat shrink tube. Seal an end, fill with BP & Igniter, seal other end... end up with a very small parcel.

 

[rocketman4h]

Some of our locals use heat shrink tube. Seal an end, fill with BP & Igniter, seal other end... end up with a very small parcel.

Nice Idea

 

[mbeels]

Other options include glove tips and centrifuge canisters.

 

[watheyak]

A latex gloves tip works great. Cut it off the glove, add the BP and the match and zip-tie it tightly around the match leads.

Very popular and reliable.

 

[Titan II]

Glove tips here too. I use dental floss to tie them. Do the same with all my rockets from 29 mm to 5.5".

Video about it.....

https://www.apogeerockets.com/Advanced_Construction_Videos/Rocketry_Video_95

 

[n27sb]

Try this thread much was discussed

https://www.rocketryforum.com/threads/spent-brass-as-ejection-charge-wells.160339/

 

[n27sb]

charge calculators call to start with a 0.14 grams of bp. That is not much

Small amounts of BP can be hard to measure unless you have a powder scale for reloading. Since I already use centrifuge vials I measure by volume.
I use around .3ml on my 24mm rockets and more like .5ml on my 29mm rocket. You always need to ground test for your rocket. Remember to take into account the volume the ematch takes up.

https://www.amazon.com/Tegg-Centrif...=1593985001&sprefix=centrifuge,aps,242&sr=8-3

 

[rocketman4h]

I have a powder scale I use it mostly for measuring small amounts of epoxy like .1g per a and b.... great for fin roots. I will use this to start with then go with volume

n27b Thanks for the link on the centrifuge vials on amazon... this looks like a winner!

 

[n27sb]

Once you test a few you will find that you can insert your match in the vial and top it off with powder to the level you have tried. You may have to go up to the next size vial for your 38 mm. If you take small bits of dog barf you can pack and compress the powder before you tape it off. This keeps it from sifting out and gives gives a better pop. You will usually use less powder if it is tightly packed in a hard plastic vial than in something soft.
BTW, I only use real FFFF Black Powder. Pyrodex or other substitutes are very corrosive and dirty.

 

[mbeels]

I also like to drill a small hole in the bottom of the vial and run the ematch wire through it. Then stuff the top with dog barf as n27sb described, and you can close to lid to make a neat package. Just ground test whatever you do, then copy what you did for the actual flight.

 

[rocketman4h]

mbeels and n27sb, you are on point I am glad I have a few weeks to test all this stuff and get better at it. The first time I tried it (15 years ago I failed due to not testing now with your advice and getting to it earlier I believe this will help me keep my first flight to 2500ft a great on with the best recovery. Thank you guys. When I get it all together I will post the pics on this thread.

 

[Handeman]

I've just used duct tape. Tear off a 4" piece, lay the match head in the center from one end. Pour powder over the match and fold the tape lengthwise sealing it. I usually mismatch the folds enough I can fold it a little smaller and stick it into a smaller package.

 

[o1d_dude]

Small amounts of BP can be hard to measure unless you have a powder scale for reloading. Since I already use centrifuge vials I measure by volume.
I use around .3ml on my 24mm rockets and more like .5ml on my 29mm rocket. You always need to ground test for your rocket. Remember to take into account the volume the ematch takes up.

https://www.amazon.com/Tegg-Centrif...=1593985001&sprefix=centrifuge,aps,242&sr=8-3

A set of graduated scoops specifically designed for powder measurement is what I have always used. They’re graduated in .cc’s.

Lee Precision Powder Measure Set is what I have. Most likely available online or at your local sporting goods store.

I think mine came from Big 5.

Amazon price is $11.99.

 

[Handeman]

I measure out my Bffff powder into all the vial's I've collected from AT motor reloads. I load them with 1, 1.25, 1.5, 1.75, and 2g amounts. I then put a piece of masking tape on the vial (don't cover the graduations so I can reload the vial with the same amount) and write the amount in large black sharpie. I grab what ever combinations I need from 1g to 6g and load charges in the charge cups.

All my ground testing is done measuring by volume so all my charges are done that way. The preloaded vials work great even when prepping at home for the next day.

 

[o1d_dude]

I measure out my Bffff powder into all the vial's I've collected from AT motor reloads. I load them with 1, 1.25, 1.5, 1.75, and 2g amounts. I then put a piece of masking tape on the vial (don't cover the graduations so I can reload the vial with the same amount) and write the amount in large black sharpie. I grab what ever combinations I need from 1g to 6g and load charges in the charge cups.

All my ground testing is done measuring by volume so all my charges are done that way. The preloaded vials work great even when prepping at home for the next day.

I use the Aerotech reload vials also but fill them to the line and seal them. I adjust the load by pouring out a set amount according to the marks on the vial.

“Blow it out or blow it up!”

 

[Handeman]

I use the Aerotech reload vials also but fill them to the line and seal them. I adjust the load by pouring out a set amount according to the marks on the vial.

“Blow it out or blow it up!”

Oh NO! Personally I consider that the worse advice you can give. It leads to longer shock cords, heavier recovery gear, over building, and more problems as you try to compensate for the oversized ejection charge and the extra stresses it applies to everything.

But that's just me.... but I suspect you know that already!

 

[o1d_dude]

Oh NO! Personally I consider that the worse advice you can give. It leads to longer shock cords, heavier recovery gear, over building, and more problems as you try to compensate for the oversized ejection charge and the extra stresses it applies to everything.

But that's just me.... but I suspect you know that already!

True. It’s just something you hear at launches. I probably should have added that disclaimer

Personally, with reloads I always ground test my ejection charges to make sure they’re in the ballpark and to verify any adjustments.

 

[David Schwantz]

centrifuge canisters.
https://www.midwayusa.com/product/1022388264?pid=317785
https://www.midwayusa.com/product/1022388264?pid=317785
and to scoop with
https://www.target.com/p/kitchenaid...VBNvACh1IOAz-EAQYAyABEgJ50PD_BwE&gclsrc=aw.ds
https://www.midwayusa.com/product/1012948067?pid=755866

 

[manixFan]

Using scoops is just as accurate and much easier than using a scale. I've seen folks trying to use a scale outdoors at a launch in the wind and it just seems problematic. Scoops cost less and they don't need batteries.

I've flown many 38mm MD rockets (mostly at BALLS) and have found .45 ACP and .45 Long Colt cases to be perfect for that size rocket. I used to knock out the primer and run the e-match thru the hole but that made them hard to mount. Now I either run a screw through the hole into the bulkhead to hold them in place or leave the primer in place and just tape them down. I fill the empty space with wadding and tape them over and around with electrical tape.

I have flown my 38mm CF mongoose to about 15,000' feet and even had redundant dual deploy in it. You don't need much BP since the volume is so small. If you are unsure, ground test. The amount you list seems low if you are using any kind of shear pins.


Tony

I don't have a picture of my 38mm Mongoose, but here's the same setup in my 54mm CF Mongoos using .45 Long Colt cases as a charge holder: