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Copper or PVC BP Canisters? Horizontal or Vertical Mount?

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Peter

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This may be a bit simplistic of a question but here I go...Thanks to hints / help from you fellow TRF'ers I'm assembling my electronics bay for installation into a PML 4" AMRAAM. PVC is bit easier to work with than copper so will that be adequate or stick to copper and avoid a potential for shattering?
Finally, horizontal or vertical mount of the canister, does it even make a difference? Thanks in advance. - Peter
 

rstaff3

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I have used PVC a few time, both for a fixed and free-hanging applications. By 'fixed' I mean that I had a threaded coupler installed in a bulkhead and the charge is in a male cap that threads into the coupler. I don't think PVC will shatter, just don't cap the end with, say, epoxy ;)

I don't think the orientation makes much difference. I wouldn't wedge the cannister right up against the airframe wall. In many of my apps I have the cannister rest against the top CR, without caring about the orientation.
 

cls

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I've been wondering about this, too.

Dick, could you post some pictures of your cannisters?

do you always leave the end open, or did you ever try a baffle arrangement, like maybe a threaded cap with a bunch of holes in it?
 

Missileman

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Another option is disposable canisters.
A package of BT5 tubing from the hobby shop will make dozens of canisters cut to the exact length you need.
 

rstaff3

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Originally posted by cls
I've been wondering about this, too.

Dick, could you post some pictures of your cannisters?

do you always leave the end open, or did you ever try a baffle arrangement, like maybe a threaded cap with a bunch of holes in it?
There are couple of pics in this EMRR review:
http://www.rocketreviews.com/reviews/scratch/upscale_big_brute.html
Near the top is a pic showing the coupler installed in a bulkhead, and near the end of the review is a pic of the charge cannister. Description of their use are buried in the text.
 

DynaSoar

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Originally posted by Peter
This may be a bit simplistic of a question but here I go...Thanks to hints / help from you fellow TRF'ers I'm assembling my electronics bay for installation into a PML 4" AMRAAM. PVC is bit easier to work with than copper so will that be adequate or stick to copper and avoid a potential for shattering?
Finally, horizontal or vertical mount of the canister, does it even make a difference? Thanks in advance. - Peter
Take into consideration the radio transparency of your bay in case you choose to use any Tx and/or Rx capability.
 

kgholloway

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Personally I do not use cannisters for my ejection charges. My altimeter bays are constructed with european style terminal strips mounted on the bulkheads. These are used for the connections to the electric matches.

To make up a deployment charge I take an ordinary rubber or vinal glove and cut off one finger per charge. I measure the charge, pour it into the finger, and insert the end of an electric match into the powder. I then twist the upper end of the finger to tighten it around the body of the match and secure it with several wraps of masking tape.

To use the charge I insert it into the rocket so that it will lay on top of a bulkhead or on the top of a Nomex chute protector when the rocket is under accelleration. I then cut, strip, insert, and tighten the leads from the electric match into the appropriate terminal strip.

Just a suggestion for a simple method that works for me.

Ken Holloway, NAR #78336
 

hokkyokusei

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Spent estes motors can also be used as ejection canisters.
 

rstaff3

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Methinks this poor cat has lost all its skin :)
 

Reed Goodwin

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Thread Ressurection!! So, has anyone ever thought of using a film cannister for an ejection cannister? Snap on lid that should contain the explosion until it has a fair bit of force, shouldn't be able to shatter, relatively light. Any ideas whether it would work?
Thanks,
Reed
 

nialloswald

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So, has anyone ever thought of using a film cannister for an ejection cannister?
I believe they have. However, my thoughts are that they might be a bit on the large size unless you're trying to pressurise a huge volume of tube. You might be able to use wadding to keep the BP at the bottom, but it seems like asking for trouble, ending up with no BP near the e-match. That wouldn't be pretty!
 

hokkyokusei

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Originally posted by Reed Goodwin
Thread Ressurection!! So, has anyone ever thought of using a film cannister for an ejection cannister?
In the UK, a film canister full of BP is known as "a Jarvis". Sorry Ben.
 

Smokin' Rockets

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Ken has the right idea.

Fingers from rubber gloves or the corner of a baggie make the best charges. Burns evenly and is non directional.

Canisters tend to blow some of the powder out without burning it fully. They are also directional and dont create even pressure.

I have seen horizontal cannister charges blow holrs through couplers and airframes.

....Bill
 

Reed Goodwin

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Well, I have bought some PVC parts today and they should make some great ejection cannisters. One is a 1/2" end plug and the other is a 1/2" end cap. The force required to pop the end cap off can be varied by how hard you push the cap on. Here's a picture. Any ideas on how best to mount it, considering there is no room on the bulkhead of my ebay? I understand that it should be facing out, but how can I be sure it stays that way? Attach it to the U-bolt on the bulkhead?
Thanks,
Reed
 

bobkrech

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Reed

It's probably not a good idea to use a PVC cap. It could easily become a projectile and blast through your rocket.

If you really want to use the cap, drill a large (3/8") hole in it, pour the BP over the e-match in the well, put some wadding or sponge foam in the well to prevent the BP from moving, put a piece of electrical or masking tape over the well and then place the cap on.

Doing this will insure the e-match stays incontact with the bp, and when it ignites, it will burn through the tape and pressurize the rocket without creating shrapnel or shooting the cap through the rocket.

Bob Krech
 

edwardw

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I use latex surgical tubing - similar idea to the latex glove. I cut a 12" length, at one end put an e-match in and zip tie it tight. Pour the BP in the other - tap down. Then I cut the tubing about 1/2" above the end of the bp and zip tie shut. Easy and works.

Edward
 

Reed Goodwin

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Hmm, I have my doubts as to whether it would blast throught the QT airframe, but I could be wrong. If I did not use the cap, how could I seal it well? Masking tape over the end?It would seem like that would blow off before all the BP was burned. Also, here's the picture I forgot.
Thanks,
Reed

EDIT: I have requested that my mom bring me a letex glove from her work, so I should have a number of options for ejection charge holders.
Reed
 

tnrocketman

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I used some little copper end caps from Lowe's, drilling a small hole thru the capped end to screw mount to the bulkhead and ran the e-match thru to the bottom before packing with BP, dog barf, then capping with black electric tape
 

Mark Palmer

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Voice of experience here....

Aluminum and copper homemade canisters - I have put each of these through airframes (glassed Phenolic and Quantum). They basically become projectiles....IF you decide to use either of these....Secure them to the Bulkheak...FACE UP.

PVC...tested a large charge for a really big project and basically destroyed the canister....and almost an altimeter as well.

My Choice....Estes BT5...sealed at one end with hot melt glue...Ematch fed through open end to the bottom of the canister, BP gets poured in, packed lightly with Wadding and sealed with tape. No problems todate after many flights....learned this trick from Art Upton of BoosterVision...Works like a charm.

BTW...I also subscribe to the "blow it up or blow it out" methodology...especially when it comes to the Back Up Charge.....


Mark A Palmer
 

fyrechaser

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Just a suggestion here.....You might try quickburst's EZ canisters. Thats all I use, and have 100% success with them. They are just a cardboard tube with an e-match sealed on one end and plenty of wire. I just pour in my measured BP, pack in a little estes recovery wadding to keep the BP in contact with the e-match, and seal with masking tape. Painless...easy to prep...and very reliable. They come in two sizes.
 

bobkrech

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Originally posted by Reed Goodwin
Hmm, I have my doubts as to whether it would blast throught the QT airframe, but I could be wrong. If I did not use the cap, how could I seal it well? Masking tape over the end?It would seem like that would blow off before all the BP was burned. Also, here's the picture I forgot.
Thanks,
Reed

EDIT: I have requested that my mom bring me a letex glove from her work, so I should have a number of options for ejection charge holders.
Reed
Look how Aerotech seals their BP in reloadable motors and single use motors. Plastic caps, tape, etc. works just fine.

Bob Krech
 

Reed Goodwin

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Well I did some ground tests today. I used some homemade igniters and a 3/4" PVC cap about 3/4 of the way full of Pyrodex P and sealed with masking tape. This may seem like overkill, but at the TRF reunion launch the .8g of BP in a latex glove all wrapped in masking tape didn't blow the paraachute out.

The first test was just the cap in a small hole in the ground just to see what would happen before I put it in the rocket. I hit the button and there was a pop and a large puff of smoke. I went and looked and it had burned all the charge and had burned through the masking tape, releasing the pressure. It seemed to work.

Next I put a similar cap in the rocket, not attached to anything but pointing in the general direction. I set the rocket up in a lawn chair but did not attach it to anything. In retrospectt, it would be something to do next time to make it safer. Anyhow, I pushed the button and "poof!", the rocket seperated and the whole thing went flying into the air. It landed, unharmed with the inside all dirty. I went and checked and it was perfectly fine, everything had deployed nicely, though the parachute had not had time to open. Again, all the charge ahd been burned and there was a hole in the masking tape where it had burned through. According to PML this chute should not fit in this tubing, but it does and with enough of a charge, it comes out.

I did not get any pictures because I left my digital camera at my mom's house. Next time, the cap will be a 1/2" PVC cap filled 3/4 of the way to the top and sealed with maksing tape. I would attach the cap to something, but there is just no room on the 2" diameter bolkheads.
Anyway, that was my excitement for the day.
Reed
 

Reed Goodwin

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Well, I got a picture of the cap last night. The one that I used for the ground tests is the dirty one. The other one is a 1/2" cap that I will use later on.
Reed
 

Reed Goodwin

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Well, I did another test with the Pyrodex P yesterday but this time I used the 1/2" cap. The scale I was using said it was about 1g, but then again, it only measures to a gram so the actual amount may have been closer to 2g. Anyhow, it ejected and this time I took a movie of it. I will compress it and post it this evening. For all intents and purposes, this seems to do the trick. I will be getting some 2-56 nylon screws sometime soon so I will do some tests with those installed. That's all for now.
Reed
 

FredA

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I always use PVC pipe caps.
I drill a small hole in the bottom and use a 4-40 screw to screw and glue them to the top of my Ebay bulkheads.
I put a dab of epoxy on the screw-head and nut to secure them and to cover the screw head so it won't short the ematch.
I fold a ematch so that it lays flat on the bottom and the wire dresses up over the side and down the outside.
I fill the cup with a measured amount of BP.
Stuff a bit of wadding in to take up the spare room and then tape it shut with masking tape.

Never had one fail.
I have broken them off if I just try to epoxy them in place - thus the reason for the screw.

I usually use two different sizes so I know which is the main charge and which is the backup, which is usually a larger charge.

Attached is a picture of a past ebay build.
 

blackjack2564

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I have my own little unique solution..... I leave the protective sleeve on the e-match.....slide a section of plastic soda straw half way onto the sleeve and tape it..[different length straw sections for different charges].....fill with powder stuff with some wadding and tape shut.....the straw melts or shatters giving a pretty unifor and unidirectional charge...also you can measure the size charge you need and after pouring into the straw you can see the charge ...most are translucent......I have a small reference gauge I made......took a section of straw, put in 1gram marked the exterior....then added another gram, marked the exterior again..... did so for up to 6 grams.....now I keep my little reference straw with markings in the range box....to make up charges just hold my "gauge " next to the fresh straw like a ruler mark it and fill up.... no more guess work...no more looking for those little gram scoops that due to size, alway seem to be misplaced when you need them the most....works for me !!!!
 

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