248 replies to this topic

[al69]

i was wondering what type of rocket would be best for lifting headers. i have made two types.
one type is where the rocket is long burning and continues to accelerate throught the burn but stops rising right after the rocket has finished burning
the other type is a fast burning rocket that burns very quickly but continues to rise a while afterwards, obviosly when its rising without propulsion its less stable.

so which one do you guys think is the best to use with a header?.
thanks

[minalth]

I have no experience, but would assume that the slower one would be better, and they look nicer too

[Jerronimo]

Coreburning rockets are the type to use, when designed right they are able to cary huge payloads.
For example: I make 17mm I.D. rockets with 33 grams of green powder
and they are able to carry a 150 gram payload(3'' shell) to a very respectable height.

[al69]

both are core burning. the only difference is that one has a large diameter core and nozzle and the other one has a smaller nozzle size and smaller core. should i just go with the first type? the large core and large nozzle (burns v fast rises for a while after) as this should be able to lift more

[Maineiac]

I'd use the longer cored/bigger nozzled motors for lifting assuming your propellant is up to the task. In a one-off 1# motor (tubes are slightly longer than is standard) we use a BP style mix @ 58/33/9 with a core about 7.25" long and a nozzle diameter of .375". C is 80 mesh, nitrate is very fine (milled). Moving the nitrate up to 60% invites catos. Dampen comp with .5% (No More!) H2O to reduce dust These pop when ignited with quickmatch and leave the pipe vigorously. Note that these motors are pressed in a pneumatic press @ around 1200 psi. So far with this design we've been able to loft 370 gram payloads to a pleasing height.

[JamesH]

Is that rocket based on Tom Rebenklau's design using an 8" long tube? What type of charcoal are you using?
370g is a very respectable payload! Do you have any pictures or videos of that particular rocket?

[Maineiac]

These are very much based on Tom's work. The motor cases are 8" long and came from his stock. The charcoal is mixed hardwood 80 mesh from Skylighter. Nothing fancy. There is no percentage of smaller mesh or even airfloat in these as it is not necessary. Unfortunately I have no video immediately at hand. I may have some from the spring shoot but the fall shoot was quite wet and the camera stayed at home.
You can see a mess of Toms rockets in action in the video section at www.osff.net
Tom is a very good mentor I must say and I'm very lucky to have him as a fellow club member.

Edited by Maineiac, 31 October 2005 - 10:55 AM.

[JamesH]

I am currently machining a set of tooling for making those rockets myself, after buying his crossette rockets dvd. You can see it here - http://photobucket.c...onstruction.jpg
Its not finished yet, just a few more things to do. I'm also waiting for two extra long drills to arrive so I can bore out the last two rammers (not in photo).

I'm thinking about using 70 - 80mesh spruce charcoal since i dont have access to commercial 80mesh.

I having trouble viewing your website, I get a "sorry this image is temporarily unavailable" message.

Your a lucky guy to have Tom as a mentor! His work really is fantastic!

[Maineiac]

That site was a pain so I got rid of it. I'll see what I can cobble together later on today. Regarding the spruce charcoal, it seems that it will burn much hotter than what we use. Some adjustments to formula may be necessary.
You tooling is looking quite good! Losing my machine shop access has been a bummer! One change that I would make is shorten the base on which the tube is set. I can't remember the exact dimension Tom used to make that to but I believe it was in the neighborhood of .375". This has been shortened drastically to about .125". This has allowed for more core length as we drill them out with a flat ground drill beyond what the spindle forms. I'll have to measure a motor this evening and see just what those dimensions end up being. Bear in mind there is a .500" delay of Winokur 39 on the top of these. This is drilled back only slightly after the passfire has been formed in the top plug. Nothing fancy for clay either, just straight Bentonite. Like Tom always says, there are no secrets.

[JamesH]

The dimensions i used came from the paper that came with tom rebenklau's crossette rocket video. Did he change them since then?
Do you have any suggestions for a formula using spruce charcoal? How much should i reduce the percentage of KNO3 as a starting point?

cheers

Edited by JamesH, 31 October 2005 - 11:38 AM.

[Maineiac]

James,
I've got some measurements for you finally. The dimension which was .300" (spindle base) is now at .0625" thus moving the nozzle closer to the end of the tube. The core is now 6.750" long (from end of tube) with the extra length coming from drilling excess comp out after pressing. A long .1875" drill works fine for this. Simply turn a quick bushing to fit into the end of the motor (centers drill in core)and afix a drill stop bushing to allow .300" travel into the core. Remember to regrind your drill point to a flat profile. The passfire is drilled down approx. .750" to the Winokur 39 delay(from top of tube). Mind you this is just starting to show the delay so from this you can extrapolate the grain length etc.
I don't believe there are any other changes. The shortening of the spindle base could be overcome by simply turning down the base. A quick fix is to make a simple bushing to adjust the height.
If I can answer any other questions about these motors let me know and I'll see what I can do.

[JamesH]

How thick is the clay nozzle and top plug and at what pressure are they pressed?
Thanks for digging up those dimensions for me!

Edited by JamesH, 02 November 2005 - 02:30 AM.

[Maineiac]

Nozzle is .500" thick, one would have to trig out the angles to find the actual "bite" of clay to the tube wall. The top plug is a bit harder to measure as the passfire is so small. From my figures it appears to be about .6875" thick. These are both pressed at approx. 1200 psi as are all the increments of comp in the grain. I checked the clay and comp scoop dimensions that are given on the sheet from the dvd and they are all still valid as of this past June anyway. Motors are pressed in a sleeve which is snug at the outset. Motors are removed via a small air cylinder mounted below vee blocks. Neat little rig as is the press itself.

[JamesH]

I intend to machine a split block type support sleeve from aluminium since I haven't been able to find any stainless steel tubing of the correct I.D.

[raiderzone]

I'm glad members are posting videos of their projects. I'll continue the momentum with.....

2 Oz BP Coreburner with canister payload of pumped Conkling KP Organic Blue stars. Keep the rocket vids coming!

http://raiderzon.pyr...nkling_blue.wmv

Working on getting nicer symmetrical breaks. Nothing comes easy