248 replies to this topic

[dr thrust]

found a use for old mastic tubes from work ideal for cylindrical headers

Edited by chris m, 13 April 2008 - 10:00 PM.

[dr thrust]

yeah! "they say" that a 3lb rocket motor should be "10 inches long" so heres a couple i knocked up today the one on the left is using an urbanski german rocket rp 60/25/15 sulfur , which seems quite a high sulfur content so we will see, the next is using 58/33/9 , both headed with 3inch plastic shells filled with d1, rice hulls and flash booster, video to follow the motor,s weigh in at 340 grams! taking about 140 grams of fuel, and with the headers this goes up to about 439 grams

Edited by chris m, 30 March 2008 - 09:24 PM.

[pudi.dk]

Nice rockets chris m


18 mm Burdick blue rocket from tonight

Man that thing is funny sounding! And from what I see, I can conclude it does not actually strobe, just like everyone else confirms. The strobes that are visible on the video are just some branches getting in the field of view.

I remember an article saying that the ammonia-smelling GE silicone will not work, but I used glass silicone that smelt horrobly like ammonia!

[sui]

Nice rocket, pudi !

It sounds indeed like a fart-rocket , but man thats fun ! Can you give some details of the construction ?


Keep the vids comin´

Sui

[dr thrust]

heres the urbanski number, hard to track it went up fast and high getting there!

ps , nice job on the rocket pudi, are you going to make some more?

[Pretty green flames]

How does Kaolin clay compare to straight Bentonite in regards to nozzle erosion, i've been getting some pretty devastated nozzles when using bentonite so i'm looking for alternatives, i've heard it can be used for nozzles but that's pretty much all the information I was able to find.

Thanks, PGF

[dr thrust]

hmm, cant find any reference to it in nozzles, try adding 5% powdered graphite to your bentonite, ive found this to help so much so, that my tubes side wall burnt through with heat deflecting back, and i had to alter my tooling ( steeper chamfer on the first rammers end )

[Sambo]

I made a simple test stand for measuring the thrust of my rockets, tested a short cored bp 1" id x 6" long motor on it earlier it was surprising..
Rocket testing
3.3kg on the scale! it bottomed out there so it might be a bit more.
My question is, how is this related to how much weight the rocket can lift?

Edited by Sambo, 07 May 2009 - 08:45 PM.

[seymour]

The general rule is a rocket will have a stable flight if the mass is no more than one fifth of the thrust.

So you can lift at least 660g, including the weight of the motor and stick.

[Sambo]

Thanks Seymour

[knackers]

I made a simple test stand for measuring the thrust of my rockets, tested a short cored bp 1" id x 6" long motor on it earlier it was surprising..
Rocket testing
3.3kg on the scale! it bottomed out there so it might be a bit more.
My question is, how is this related to how much weight the rocket can lift?

your motor seemed to expire prety quick for a 6" length i thought, what were the specs, (core length and diameter), i would have thought it should have stayed in the thrust curve for a bit longer,

[Sambo]

Yea the propellant burn time was about 1 second, excluding the delay.
The dimensions for spindle are;
Length - 80mm
Diameter at base - 8mm
Diameter at top - 6mm

I use a 65/25/10 ratio ball milled for ~ half hour

[seymour]

That's the burn time that I always got with my coreburners of very similar dimensions.

I usually used less charcoal though. What wood is it from?

[Sambo]

Its just regular pine from the builders merchants, specifically CLS from B&Q lol.

[shadowpyro]

Hey Guys,

Was just reading into the whole using a QM for fusing so that ignition starts at the core of the engine, rather than the nozzle end. (If that makes sense).

Was wondering if there's actually any marked different between those two, as i was doing some testing earliar with using just visco or with QM to the engine core. Composition ratio used was 70:30:10 (hot! but the 60:30:10 was too slow, so i opted to add more KNO3), made with pine charcoal, milled for 30min for even mixing, though all components had already been pre-milled.

Both engines seemed to fly to a good height, with a very fast ascent! So I personally didnt notice any particular difference, although I would suspect that the flame front would spread in similar ways up from the nozzel or down from the core?

Perhaps It'll be more noticeable with a slow comp like 60:30:10 (or weingarts 55:30:10)? Has anyone had a play with this?

Cheers

Edit: Also just realised I've just ressurected a year old thread, but didn't want to start a new thread on something thats possibly so trivial!

Edited by shadowpyro, 04 August 2010 - 01:09 AM.