Homemade Ematches

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Ryan S.

Well-Known Member
I am making some out of Chrismas lights. But I have a question; does this work with an RRC2?

o yes and should the BP be under some kind of pressure? or can is jsut be loosly put in with the broken bulb?

aksarben10

Well-Known Member
Yes they work fine. I have seen them used with a mirco-centerfuge container around them and one of our club members did a number of tests with them and just had a paper sleeve to contain the BP. He was very successful with the the paper sleeves.

I use the Pratt Ejection can, I believe that they are the same thing, with the centerfuge container, just that he has taken the time to build them. They are very reliable and have never failed to fire for me with my RRC.

I put a little dog barf on top of the BP to keep it from floating around the container.

Check out the web there a several web pages where tests have been performed on these.

Scott

aksarben10

Well-Known Member
You know, I saw a page done on this topic and I cannot find it anymore. So I guess I will just tell you what I remember about it.

If anyone knows any sites on this please post them here.

This person, lets call him Joe Rockteer or Joe for short had been testing designs for dual deployment ejection charges.

Joe decided that mini-christmas tree lights deserved a look since the price was right a were very available.

The hardest part is breaking the bulb without breaking the filiment. Joe scored the bulb near the top and then used pliers to snap of the top, leaving a couple of 1/4 or more of glass over the plastic rim.

Once this is done, take some regular copy paper and make a strip about an one to two inches high. Then cut the strips about 3-4 inches long. Use a glue like rubber cement, or what ever, and wrap the paper around the top of the bulb near the glass, careful of the filliment.

When this is done, you should have a bulb that is open at the top and a paper sleeve around the lamp. The width of the strip is what controls the amount of bp that can be put into the ejection charge.

Once dry, fill the bp in the tube and then crimp or twist the top of the paper closed in a manner that will not allow it to open.

Thats it, your done.

You can either wire it up that way connecting to the wires on the bottom of the lamp or take the light strand and mount the base of one of the lamps in the bulkhead of the avionics bay. This way you can just push another one in after the last one is used.

Like I said one of our club members tested and used this method with success.

The other way I have seen to use them is to put them in the micro-centerfuge canister.

I have read concerns that the filliment is not up to the rough ride that it will get from a rocket ride. However, my experiance is that they hold up fine.

Scott

Stymye

Well-Known Member
thanks for the posting, scott and mark,!

and just in time for the holidays!

Juerg

Well-Known Member
Well, I am affraid I have to make a clear statement on this:
<b>This is not a way to save money, but most likely to spend more money. </b>
I am astonished that a manufacturer like perfectflite publishes such stuff.
These bulps (the filament) are very fragile, even if you test "continuity" on the ground you will not know what is left of it after launch (remember the g's!).
You may have damaged the wire while loading the charge, and it happens just to be in contact with the other terminal by coincidence.
The BP load will shift throughout the flight, and at apogee there may be just NOTHING...
Safe $1 per flight for 50 successful flights and then dump$100 (your rocket) when the 51st bulp does not work. Not really a deal!

Use commercial e-matches! These are reliable and robust.

Take care

Juerg

MarkABrown

Well-Known Member
I have to agree with Juerg. I'm speaking from experience here. I tried to save some money by making my own ematches. The resistance on the ematches registered very low, however, when it came time for ejection, nothing. It cost me a scratch-built rocket, a Gwiz MC, and an RRC<sup>2</sup>. Paying a \$1.00-1.50 per flight is worth the insurance.

n3tjm

Papa Elf
I have to say the filiments in the bulbs I use appear to be very strong. I filled my ejection canister clear full of 4FG, and fired it... When the smoke cleared, not only was the filiment still connected to both terminals, the filiment was stretched several times its normal length. I use bulbs ever since. No failures yet.

I buy myh bulbs from Target, from those 50 string lights.

aksarben10

Well-Known Member
Originally posted by Juerg
Well, I am affraid I have to make a clear statement on this:
<b>This is not a way to save money, but most likely to spend more money. </b>
(snipped some to save bandwidth)
Use commercial e-matches! These are reliable and robust.

Take care

Juerg
I am not going to disagree with you on this point. But you know some people just like to experiment with things or know that they built as much of the rocket as possible. People also love to experiment and innovate thats what makes this hobby great be it new models or new ejection methods. I am very intrigued by the new CO2 options that are on the market and I am also waiting for Defy Gravity to start selling there tether again.

Also with the possibility that E-matches may/are being regulated by the BATF this is a valid avenue for individuals to pursue.

Scott

powderburner

Well-Known Member
If there are concerns with reliability of this approach, I must defer to you guys who actually build and fly these things to be the ones to quantify the level of that risk. Maybe they do fail once per hundred shots.

I would point out, however, that it would be a simple matter to greatly enhance the reliability of this type of ematch by simply using two (or even three) in parallel on the same firing circuit, or to use redundant timers each firing separate squibs (for even more reliability). Simultaneous failure rates (for two ejection squibs) change from one-in-a-hundred to one-in-ten thousand.

While these cheapo Christmas lights are indeed fragile after being used X,000 hours for the past few years, and burn out if you look at them, the brand-new ones are not. After all, these things (cheapo or not) have survived bouncing around for hundreds of miles in the cargo bed of a truck, being thrown around the stockroom behind the store (ever seen those guys at work?), and various other forms of abuse, and they still light up when you bring them home and plug 'em in. I suspect they are tougher than some of you think.

MarkABrown

Well-Known Member
I'm not trying to discourage anyone from trying however, after my experiences, I'll pay the small price for commercial quality control when it comes to ematches. I'll still make my own igniters but not ematches.

Ryan S.

Well-Known Member
but dont you need a LEUp for ematches?

by the way I tried this and it worked perfectly for My dual deploy V2 flight

thanks!

rstaff3

Oddroc-eteer
You also need it for the BP in the charges.

Ryan S.

Well-Known Member
SHHH!!!!

While this is true I can get the BP without one. I cant even get my hands on the ematches

aksarben10

Well-Known Member
Originally posted by Ryan S.
but dont you need a LEUp for ematches?

by the way I tried this and it worked perfectly for My dual deploy V2 flight

thanks!

Wrong, to purchase, transport and store e-matchs for private non-public use you must have as a minimum a LEUP and a TYPE 4 indoor magazine.

See the passages below from the Orange book subpart b. Some people will argue this and say ematch are not specificly outlined in subpart b, others say they fall under the squib catagory. The ATF could split hairs with you on them and call them squibs or ignitors. Also notice the catch all statement "The term includes, but is not limited to", you can drive a truck through that hole. Already Oxral and other manufactures will not sell to you without a permit. If you do not believe me call your local ATF agent to get their take on it.

Black Powder is a different story, you do and you dont have to have a LEUP depending upon you intended use. If you intend to use it for a gun, sure you can have up to 50lbs. If you want it for a deployment charge then you need the same as you do for the ematches a LEUP and a Type 4 magizine. Pyrogen is also an option for ejection charges, if you keep it contained it should work. Several people are testing it.

Orange book, Subpart B-Definitions:
Explosives. Any chemical compound, mixture, or
device, the primary or common purpose of which is
to function by explosion. The term includes, but is
not limited to, dynamite and other high explosives,
black powder, pellet powder, initiating explosives,
detonators, safety fuses, squibs, detonating cord,
igniter cord, and igniters.

https://www.atf.treas.gov/explarson/fedexplolaw/subpartb.pdf

(5) commercially manufactured black powder
in quantities not to exceed fifty pounds,
percussion caps, safety and pyrotechnic fuses,
quills, quick and slow matches, and friction
primers, intended to be used solely for sporting,
recreational, or cultural purposes in antique
firearms as defined in section 921(a)(16) of title 18
of the United States Code, or in antique devices
as exempted from the term "destructive device" in
section 921(a)(4) of title 18 of the United States
Code

https://www.atf.gov/explarson/fedexplolaw/explosiveslaw.pdf

This is a link to the whole and current copy of the Orange Book.
https://www.atf.treas.gov/explarson/fedexplolaw/index.htm

This link is not a bad one to look at either.
https://www.atf.gov/regulations/27cfr55.pdf

Scott

rstaff3

Oddroc-eteer
I was obviously referring to the use of BP for ejection. If there were as many rocketeers as gun owners we'd have our exemptions also.

I have successfully tested Pyrodex-P on the ground, but haven't flown it because only my HPR rockets are electonics-capable. If any vendors will sell Easy Access without a permit in the next flying season, maybe I'll flight test it too.