I'm going to try Triple 7 .50 cal. pellets to ignite 38mm AT motors, sort of like Cesaroni Pro38's. Should I use 30 or 50 grain pellets. My guess is 30 would be enough because they weigh 1.77 grams, about the size of my ejection charges. What think you? Larry Lobdell Jr.
I am assuming you are talking about the pressed quick load pellets. That is a lot of quick burning black powder to put into a motor. That should make a nice boom. Hope you don't mind buying new motor hardware after each ignition. The pellet will burn so fast it will overpressure your motor and "Boom". I've never tried it of course (I value my hardware and rockets) but I have shot a lot of black powder muzzle loaders. I am fairly confident that your motor will act much like the muzzle loader and expel the fwd and aft closures. My muzzle loaders only expel the fwd closure (Thank goodness).
KT
Yes I mean the quick-load pellets. So why don't the Cesaroni Pro38 motors go "boom"? They have an ignition pellet. The e-match ignites the pellet and the pellet ignites the motor. A motor core will disipate pressure much faster than confined pellets used in a muzzle loader. Besides, a motor has an open nozzle to disipate the pressure while again, the muzzle loader has no pressure relief opening. Also, powders burn at a much faster rate when confined in a muzzle loader than when in open air in a rocket motor. Seems to me the only way the motor would go "boom" is if the nozzle was plugged.
If I remember right, others on this forum suggest a similar method of motor ignition, so what am I overlooking? Larry Lobdell Jr.
Yes I mean the quick-load pellets. So why don't the Cesaroni Pro38 motors go "boom"? They have an ignition pellet. The e-match ignites the pellet and the pellet ignites the motor. A motor core will disipate pressure much faster than confined pellets used in a muzzle loader. Besides, a motor has an open nozzle to disipate the pressure while again, the muzzle loader has no pressure relief opening. Also, powders burn at a much faster rate when confined in a muzzle loader than when in open air in a rocket motor. Seems to me the only way the motor would go "boom" is if the nozzle was plugged.
If I remember right, others on this forum suggest a similar method of motor ignition, so what am I overlooking? Larry Lobdell Jr.
Most, but not all, AeroTech 38mm reloads have a 1/2" core. A 50 caliber pellet is 1/2" wide. One 30 grain pellet is enough for a 38mm motor.
I've used this method for many years with 29mm, 38mm, and 3" motors. I also always use plugged forward closures and an altimeter for deploying the parachute(s). I do not know how using a pellet for motor ignition will affect a delay grain.
Ignore the person who says it will blow the hardware apart.
snipped-for-privacy@pacbell.net wrote in news:MOlUg.12575$ snipped-for-privacy@newssvr27.news.prodigy.net:
Wouldn't burn rate and case pressure limits determine nozzle diameter?
BTW,IIRC,those pellets are not "black powder",but a smokeless substitute. Someone else here mentioned that smokeless propellants are used in military rocket motors.
Yes you can ignore me. Like I said I have never tried it. But apparently you have so I should be ignored. Sorry for the spastic reaction I gave. I just thought it might blow up.
KT
The typical operating pressure of an amateur rocket motor (commercial or experimental) is on the order of 300-500 psi, and the hardware is designed with an appreciable safety margin. The safety margins for Loki, Kosdon and AMW casings are even higher due to the thicker walls. It is highly unlikely that an ignition pellet would cause a pressure spike to the point that the motor would CATO.
"Brian McDermott" wrote in news: snipped-for-privacy@c28g2000cwb.googlegroups.com:
Why not just paint the proper area of the grain with homemade igniter dip,perhaps the sort with ground-up sparklers? Maybe use it to 'glue' the igniter to the grain.
Use 30 gauge Nichrome wire as a filament, put your sparkler powder in ping pong ball lacquer and triple dip the igniters? Should work for
38's.Alternatively, get aluminum powder and copper oxide off of Ebay, Mix
4.22 CuO to 1 Al by weight, put in the lacquer and use it without an oxidizer. There is usually a 1 to 2 second delay before the copper oxide thermite lites off but it is plenty hot to ignite a 38mm motor.The Pyrodex pellet will not CATO the motor. People do this all the time.
A 30 grain pellet will be plenty for a 38 mm motor. Ignition and liftoff will be quick.
James
Well, that depends. T7 is not very friendly. Unlike BP which has a very low pressure curve, T7 can and does develop mush higher pressures. As to whether or not it would blow the casing would depend on how large the igniter was in relation to the nozzle opening, the amount of grain ignited at one time, and the actual amount of pellet grain used. It could be nothing or it could be a disaster.
Oh boy, Pyrodex is not Triple 7 ....way different.
According to the Hodgdon website it seems Pyrodex has the same power as an equivalent volume of black powder and Triple 7 is approximately 15% more powerful per unit volume. Why do you believe that 15% difference is as significant as your posts imply? Given the high burst pressure safety ratings of commercial motor cases it is hard to believe a 15% increase in power of a relatively small (at least compared to the propellant in say an I211W) 30 grain pellet used for motor ignition would have any noticible effect.
I have the feeling I'm overlooking something here, so what is it? I really don't want to buy new motor cases (and rockets) if they CATO. I'm looking for a more reliable way to ignite motor clusters, and I just happen to have a box of .50/30 Triple 7 pellets. Larry Lobdell Jr.
Sorry it took so long to reply, I don't come here so often any more. T7 is entirely a different formula with different burning and pressure characteristics than Pyrodex. For example, while Pyrodex is frequently compressed when loaded, T7 must never be compressed. Pyrodex has some very low pressure limitations that make is safe for all types of antique arms. This is most definitely NOT true with T7. T7 will develop pressures 2 to 3 times as great as Pyrodex. Further, T7 is much less corrosive under most circumstances but, if cleaned with an ammonia based solvent, it will create some of the most wicked and aggressive corrosion you can imagine in just a few short hours.
The big deal is with the burning rate and the pressure curve. Pyrodex is much milder and less prone to over-pressure.
Have you tried it, Larry?
This past weekend I used three 50 grain 777 pellets and a Daveyfire N28F to ignite an AeroTech M1550. Instant ignition. No chuff. No wait for satisfaction.
No, I haven't tried it yet, but I will at the next launch in 2 weeks. After what I've read here I had thought about just buying some Pyrodex pellets, but your post inclines me to try the 777 and see what happens. Where did you get the N28F? Must be leftovers? Larry
I used 777 pellets because I have some. I've run out of Pyrodex pellets. Either will work.
I've only seen 777 pellets sold in a box of 100. Pyrodex pellets are sold that way, too, but also in blister packs of 30.
I know a person who knows a person who ...
So does that mean now I know a person who knows a person who knows a person who...:) Larry
SUCCESS! Yesterday I tried a static test of an AT H242T with a 777 pellet and a simple e-match (Oxral) for ignition. Since the pellet (.50cal/30 grain) is slightly bigger than the motor core I used a drill bit (by hand) to enlarge the top of the motor core so the pellet would fit. The rest of the motor was assembled normally. When I pushed the button the motor lit instantly. The first flame out the nozzle was a bit orange, likely the pellet burning, followed by the normal blue flame and roar of a BT motor. From what I saw in this test about how quickly the motor lit, I'll use this method for all future clusters, air-starts, and staging. AT probably could solve its igniter problems and make ignition more reliable if it would make something like this a standard for its RMS motors. The 777 pellets are less than $0.30 each. Larry Lobdell Jr.
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