1/2” end burner efforts

[brad224]

every once in a while i go crazy and want to build rockets.  i’ve got the 60/30/10 core burners in 4oz and 1pound working well, but sometimes i get even crazier and want to fly a couple of 4oz end burners.  i have not had similar success.  i recently bought one of Caleb’s gauges (bought a MUCH too strong one) and also made one using Ned’s tutorial.  the gauges and the arbor press have helped tremendously with consistency.  beats heck out of trying go do it with a mallet.

so the ones i made with the press and the gauge have WORKED without blowing up! (of course j have only done TWO so far but hey, batting 1000.

in order to get everyone going and to open myself up to ridicule and abuse, here’s my process:

waxed the tube with a 45 caliber pistol brush coated in canned turtle car wax, let it dry and wiped it again.  used straight finely ground kitty litter for the nozzle (homemade rammers and base.

pressed 1/2” fuel increments (but only to 2200 psi calculated on the composition as instructed by Ned’s excellent tutorial.  i have no clue how you guys press 6 or 7000 psi on the composition.  i tried all kinds of tubes from homemade to NEPT tubes, multiple kinds of tube supports, moistened composition, waxed and unwaxed tubes with different types of wax, and multiple charms, incense and spells, but could not get above 3800 - 4000 without blowing out.  finally gave up and did the 2200 psi out of pure fristration, and doggone if it didn’t work.

the video is one from tonight with BP mill dust, non-moistened, but with 5% added titanium sponge just for fun.

feel free to criticize.  i hope you like the spark trail.

 

[DavidF]

That was great! For a 4oz. (1/2" ID) motor, 6500psi would read 1275 pounds on the PtoF gauge. That's the 'standard' pressure, per Wolter. For whistle rockets, 8800psi on a 4 oz. motor would be 1724 pounds. If you're pressing to 2200 pounds on the gauge, that's around 11,000 psi on the comp area. Love the Turtle Wax idea

[gizmothegecko]

Brad 224, 

Have you tried tube supports from WoodysRocks? They are pricey, but you definitely get what you pay for. That is, I have never had a blow out, CATO, or rupture of the tube after I got one of them for my 4 oz and 1 lb rockets.

[brad224]

not yett, but if my homemade ones end ip not working i may need to go that route.  i usually launch round and can shells from mortars, and don’t shoot many rockets, but every once in a while, …..

[gizmothegecko]

Sounds good. Making your own tools is a rewarding process.

[Mumbles]

If you don't make a ton of rockets, I can fully understand how it can be difficult to justify the cost of nice tube supports.

A suggestion may be to look into the work DavidF and others have done with mylar or brass shim stock tube supports. They're going to be a less expensive alternative with a good track record of success. Below is a link to a forum search for mylar. The process should be described in there a few times. If you can't find it, let me know, or maybe he'll see this and grace us with his experience and process again.

https://www.amateurpyro.com/forums/search/?&q="mylar"&quick=1&search_and_or=or&sortby=relevancy

 

[DavidF]

Thanks for the kind words Mumbles! My brass supports have been used to produce hundreds of rockets from 1 pound to 3 pound. I have quit mentioning them because they are a PITA to cut to length and finish, and take a bit of a knack to use. The exception is the ones 'made' from a piece of brass shim stock 6" wide and about 10 feet long, used as purchased, except for cutting a radius on the outer edge. They are good for 3 pound strobe rocket motors. A couple of rubber bands and a piece of tape and they're good to go. Brass thicker or thinner than .005" is no good. Brass is no good for motors smaller than 1 pound. There's a video on my YouTube channel about the brass supports.

The link Mumbles provided answers most questions about the mylar (Dura-lar brand) that anybody might have. Frank Rizzo made some alterations that work well for him. The mylar I bought on Amazon was the .005" thick, 20"X 12' long, matte both sides. The clear stuff doesn't slip on itself as nicely as the matte stuff. They don't seem to have the matte stuff in the size I bought any more on Amazon.

Personally, I think the OP's root problem may be due to interpreting the pounds of force reading on Caleb's gauge as PSI, when it's just reading P.                                            A 4 oz. (1/2"ID) tube has an internal area of only .196 square inches. A reading of 2200 on the P to F gauge is over 11,000psi on the comp area. If lower pressure was used, the supports he already has might be just fine.

With any kind of BP rockets, I use dampened mix. That's what Estes does, and they make the most reliable motors. I copy their success. I use waxed tubes for all my rockets. IF I was going to press end burners with dry 75-15-10, I'd 'micro granulate' my propellant to make it much easier to load. The video description has the details on how the powder is prepared.

Dampened BP propellant (2-3% water) including mill dust propellant, is not as easy to load in small motors, but it compresses WAY better than dry powder. A propellant grain made with dampened BP is as hard as stone. I would never use dry powder again, once I tried the dampened stuff. Another benefit of using the damp powder is that the force used to press the motor can be cut by almost half. The damp powder will have a greater tendency to pull the tube down, but not if it's waxed. 

Anyway- I ramble. The way I make rockets is not the usual way it's done, but it has served me well. There are a LOT of different ways to make rockets, and no one way is the only 'right' way. Hopefully something in this post is helpful