Dual deployment - ejection canisters...

I have read many articles about dual deployment on TRF, Rocketry Online, RMR and even Mark Canepa's book "Modern High Power Rocketry". I know you can buy ejection canisters made by SpaceTec (carried by Magnum Hobbies in the U.S.), Blacksky's E-jector, PML's Dual Charge Cylinder or make your own. Some people use 1/2" PVC or copper tubing end caps. Pratt Hobbies even has disposable ejection canisters - many, many choices.

Now my quesiton - what is the preferred method for connecting the e-match leads to your altimeter? Through your avionics bay bulkhead or via some connector/terminal block on the outside of the bulkhead? If through the bulkhead how do you seal the avionics bay from the ejection charge?

I'm sure there are many methods, but does anybody have any pictures? I'm a visual person.

Thanks!

I have seen it done with the terminals and that seems to be a very acceptable way. It did not appear that the terminals were worn from constant use.

And then there is Phil's way... I use the 1/2" PVC pipe epoxied to the bulkhead. A hole is drilled through the center to give access to the avionics bay. Then I went to a photo developer and asked for 20 or 30 empty film canisters. (they were free) A hole is drilled in the base of the canister on the side. The ematch is put in the canister and then bended to the bottom where the leads can go through the hole into the avionics bay. Then masking tape seals the hole in the bottom of the canister and it slips down inside the PVC pipe. This is the same method the PML CPR system uses so I'm pretty sure it is secure. Then I put the BP into the canister, followed by enough wadding to keep the BP in place. I then masking tape the top opening so the wadding and BP stay in place. This seems to work great.

Thanks Phil! Another question though - what type of film canister fits inside a 1/2" PVC pipe? I am trying to visualize...

I use the terminal block method. I bought some terminal blocks at Radio Shack and epoxy them onto the top of my bulkhead. Then I drill a hole thru the bulkhead and pass 2 wires thru. Those wires go to one side of the terminal block. The ematch wires go in the other side of the terminal block. The wires that go thru the bulkhead attach to the altimeter. The hole thru the bulkhead is sealed with some modeling clay that I picked up at a craft center. Sorry, I don't have the pictures available right now. I'll try to remember to post them when I get home tonight.

They are 35mm film canisters. You know the black canisters. Do you have a one hour photo or something like that near you? If so, go ask them for some. Don't pay anything for them though, most places will just give them to ya.

I like the banana jack binding posts that you can get at the 'Shack. The come individually or in pairs. Drill holes for the solder posts and then epoxy them on. They are fairly large so they wouldn't be idela for a rocket under 4" dia, tho.

I like the Pratt canisters, but haven't tried their new ones. BTW, you can get similar plastic canisters in various sizes from Aerocon.

On one rocket, I built the ejection system from a threaded PVC coupler. The canister itself is a PVC male plug with a hole drilled in the bottom. You slide thru the ematch, seal the hole with hot glue, add powder, etc. This allows you to insert the charge from the back side of the bulkhead. There are a couple of pics here.

Originally posted by rstaff3
I like the Pratt canisters, but haven't tried their new ones. BTW, you can get similar plastic canisters in various sizes from Aerocon.

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I bought a bag of 500 "Micro-Centrifuge Vials" on Ebay for about $10. They're the same thing as sold on Aerocon and Pratt but mine aren't clear. The ones I have are transparent purple and hold 1.5 grams of BP. I mix up a batch of ematches using my Ignitorman kit and then clip off the bottom of a vial. Then I hot-glue the ematch into the bottom of the vial and you have an ejection charge canister. Total invested is about $40. That works out to about $0.08/canister.

I had bought a stash of the Pratt units before I had an Igniterman kit or had even heard of those nice small vials. Your cost on Ebay is undoubtedly cheaper than Aerocon, but the Aerocon price is prolly not that much and you can get them immediately.

Anyway, I got a huge stash of vials for free from a Descon entry so my canisters would be cheaper than yours. Hmmm, the Igniterman kit was free too. And I'm a cheapskate who still will pick up a penny from the sidewalk, and who requisitions my e-match wires from the launch site. Cost per canister = the cost of the BP

However, unless Enzi prevails, I will be out of the BP business

For my L3 rockets, I use "Deans" connectors to route wires for power switches and charges if needed...here are pics of a plug I made from two Deans connectors (heavy duty gold pin plugs/sockets used for R/C aircraft) and a piece of brass tubing:

<a href="https://www.rocketryforum.com/amraam/research/bpics/wpics/w3.jpg">Socket</a>

<a href="https://www.rocketryforum.com/amraam/research/bpics/wpics/w25.jpg">Building the Plug</a>

<a href="https://www.rocketryforum.com/amraam/research/bpics/wpics/w4.jpg">Plug Complete minus Wires</a>

<a href="https://www.rocketryforum.com/amraam/research/bpics/wpics/w30.jpg">Plug to Socket Fit</a>

<a href="https://www.rocketryforum.com/amraam/research/bpics/wpics/w35.jpg">Wires with Kevlar Sleeves</a>

<a href="https://www.rocketryforum.com/amraam/success/s12.jpg">View of harness with wire ends going to switches</a>

Note that in the last pic, dead center is a Pratt Safe-Eject EXP canister with the BP charge installed and the front "masking taped" up. The "Blue" stuff around it's base is some of that "Tac n Stik" clay type putty, used to seal the chamber.

Hope it helps,

Carl

Thanks for everyone's input and I especially like the pictures (keep them coming). I guess the answer is there are as many ideas on how to do this, as there are people to think up those ideas.

Ignorance here but what do I have to do to make ematches with the Ignitorman kit. I have been making ignitors but never tried ematches.

Thanks for being kind to the ignorant(or too lazy to read the instructions)

First, in case your question came because of my use of the term e-match and Igniterman in the same post, I should point out that I used the term 'ematch' due to the application (ie for ejection purposes vs. motor ignition). This is not necessarily correct and I apologize. I have used an Igniterman pyrogen-dipped igniters successfully with my G-Wiz, but that is not to say they are appropriate for all electronics.

The Igniterman specs say you can get ignitor resistances of between 1.5 and 10 ohms. If you could hit the lower end of this scale you would probably end up with something that one might call an ematch. I typically get 4 -8 ohms by eyeballing the gap.

I'm sure Mark will add his experience with the Igniterman kit.

The only difference, at least in MY vocabulary, is that when making ematches with the ignitorman kit, you stop dipping after the conductive primer step. The pyrogen is unnecessary to light the BP.

Ahh, good point Mark. I have never stopped on that step as my igniters go into a bin and I use them for either purpose. You can always use a dipped one for ejection duties, but not vice-versa.

Changing the subject to electronics bays [and if this question has been answered elsewhere before, please point me to it]; are LOC's electronic bays worth the price, or am I better off gathering the parts individually and trying to fabricate one on my own [especially if I'm never done it before]?

I would highly recommend the LOC electronics bay. You could certainly do it yourself but, I think it is worth the cost to have everything measured and pre-cut for you. The "Stiffy" tube is a nice fit in a LOC coupler.

Originally posted by MarkABrown
I use the terminal block method. I bought some terminal blocks at Radio Shack and epoxy them onto the top of my bulkhead. Then I drill a hole thru the bulkhead and pass 2 wires thru. Those wires go to one side of the terminal block. The ematch wires go in the other side of the terminal block. The wires that go thru the bulkhead attach to the altimeter. The hole thru the bulkhead is sealed with some modeling clay that I picked up at a craft center. Sorry, I don't have the pictures available right now. I'll try to remember to post them when I get home tonight.

Click to expand...

Sorry it took so long to get to these photos. I thought I had already taken some but, found out it was my imagination. So, I went and took some pictures and uploaded them.

LOC 4" Electronics Bay

Originally posted by rstaff3
(snip)

On one rocket, I built the ejection system from a threaded PVC coupler. The canister itself is a PVC male plug with a hole drilled in the bottom. You slide thru the ematch, seal the hole with hot glue, add powder, etc. This allows you to insert the charge from the back side of the bulkhead. There are a couple of pics here.

Click to expand...

Dick,

I am really interested in seeing you setup for DD on a stubby rocket! I have couple on the shelf and have been toying with ideas. So far from what I can make out in the pics you have good thing going. Is there anyway you can post or send me some pitures with a little more zoom to them?

I'm printing off the page you referenced above right now.

Shane

Shane,

My Upscale Big Brute only supports single deployment, but it does probide for airstarts. I have higher resolution pics that I can email to you if you are still interested. I can't attach pics to the email thru TRF so if you email me your address, i'll send some your way.

Here's my email address: [email protected]


I'm definately interested. I still have DD in mind, but I see promise here.

Shane

Just sent you a few pics, hope they help. It may be a few minutes until they get out of my computer

Hey Shane - you might talk to Gary too. He did dual deploy on his upscale I-Roc that went up on an L. He used a clip from (I think) defygravity.com that allows for dual deploy from a single break in the rocket - i.e. from the top. Just a thought.

Loopy

Mark,

Were you there when we sent that puppy up for the first time? I don't remember seeing you there, but you're correct and this will be considered as well. It's a nifty little tool! Did you get to see it up close and personal that day?

Shane

see here how we solved the problem .

on the picture there is an RDas ,with battery mounted on a canister that will slip into a 38mm motor tube.

This way preventing the battery to come loose. If you use a smal piece of masking tape to seal the holes no gassed will damage the electronics.

https://www.cavemanrocketry.com/electronics/electronics.htm

I have never lost a rocket due to electronical failure since we started using these things.They realy work

Shane - Yeah, I saw it go on the L777. Beautiful! I was the guy with the two little boys in the big stroller. And yes, I was fortunate enough to have a "grand tour of the I-Roc" from Gary. That thing is flat out awesome!!!

Loopy

I would highly recommend the LOC electronics bay. You could certainly do it yourself but, I think it is worth the cost to have everything measured and pre-cut for you. The "Stiffy" tube is a nice fit in a LOC coupler.

Click to expand...

About the LOC electronics bay - be careful about the length. The standard bay is only 6" long. I have a Missile Works RRC2 which is 6" long and will not fit. But, I just found out that Barry Lynch does have a long 8" version of the same kit.

Thanks for everyone's input. I just finished my first altimeter bay using several of the ideas posted in this thread. I started with a "basic" kit from Giant Leap Rocketry and went from there. I have included a few pictures for your viewing pleasure.

Another picture of my altimeter bay for a Missile Works RRC2.

Top view of my altimeter bay.

Hey, where have I seen something like that before?