H242t-i357t??????

My dad and I got some H242Ts (4), and, looking through the plastic baggy, I saw that the proppelant grains said "use in H242T&I357T only". does this mean I can mix and match the grains, and put 3 grains in a 38/360 case, instead of 2 in the 38/240? I have had several reccomendations to use this motor, and if I have a chance to use it, I would really like to. has anyone tried this so far? Thanks for the advice.

This is all right to do -- the grains are sometimes shipped this way and assembled into reload kits -- as such, they are interchangeable. However, you would need the I357T nozzle to make sure you don't cato the motor... by increasing the length of the motor, you increase initial Kn, and therefore need a bigger nozzle to keep the chamber pressure down. So, yes it's possible, just not with the parts you have. You could order an I357T nozzle from RCS if you were desperate, although this would technically be an EX motor...

HTH!

Awwwwww man! oh well. I suppose an I161W is stil just as good. still fun to dream, though! I also noticed that the little paper tube you put the grains in would have to be a different lenth.

I love em I357 motors... I make reload kits out of fuel grains all the time. My most recent aventure occured when a guy gave me a box full of rocket stuff inside was a variety of propellant grains, liner tubes, nozzles, and a bunch of disposable plugged motors. After ordering some nozzles and liner tubes, I managed to put together a H123, H242, and I357 reload from that lot ... Today the only thing I have left is the H's, and one of the five E15-PW motors. If you order the parts directly from Aerotech, saying I need to buy a liner and nozzle for a H242 (like I did), then the load you create would still be certified.

interesting. I guess I will stick to the original plan, however, because there are only 7 days to the launch, and who knows how long it would take to get here. thinking it through again, I think that I should proabably just admit that my first HPR reloads are enough for one launch, not my first HPR rocket, my first HPR reload, my first border-line EX motor, etc. if we have any of them left after this launch, I will, though. is there a 38MM case that you only put 1 grain in? what kinda motor would that make??? Oh, yeah, that would probly be an EX motor. it does not say anything about using it in anything other that H242 and I357. oh well. still fun to think about.

cool, I need to get my AT 38mm cases so I can get some

When did you get your LEUP? I need to get one so I can buy my own motors instead of having to go through outher people

What do you use for a magazine?

o I forgot about the nozzle thing, I once saw a J420 with a I nozzle in it. BOOM the forward closure and nozzle got blown about a foot into the ground. it sucked for the guy but was cool to look at and I got a big redline gain

Pro38 has a 1 grain G motor. And Dr. Rocket made a 1 Grain G motor 38mm case for when Aerotech decides to make their G61 loads. I can't wait for that to happen... asuming they don't charge to much for them.

o yeah cause you could just take a bunch of the grains and make a J570 HAHAHAHAHAHHAHAHA

That won't work. The J570 grains are different then the others with its core size and formula. You try doing that, and the motor will blow up.

I was about to say "COOOOLLL" to ryan s. idea, but then I saw your reply, so I think I might just have to change my mind. what about a J350? would that work?

AT has two different flavors of WL and BT propellants -- slow and fast. Longer motors get slow propellants, shorter motors get faster propellants. The cutoff for the 38mm cases is 38/480 (for blue thunder) and 38/600 (for white lightning). I284Ws use a different propellant than I211Ws, and I300Ts use a different propellant than I357Ts -- you may notice the flames are different colors and/or shapes...

AT also drills different core sizes for their motors... e.g. a J350W has a 1/2" core (after that whole fiasco of J350W catos at LDRS XXI). An I211W only has a 3/8" core. So you'd have to make a lot of mods to the grains to make em work... and then you couldn't fly it at a commercial or EX launch.

And if you ever wonder what happens when you put Fast WL in a motor where Slow WL was needed... talk to Scott Binder about his 7.5" Thor at XPRS I...


HTH

OBTW, if you ever need more clarification of Fast vs. Slow BT... check out the BT 98mms! M2500T and M2400T are slow, while the L1500T and K650T are fast. No better verification than an 8 foot blue flame!

Yeowch. is he the guy who runs binder design? What happened at LDRS XXI? how many blew up, and why? core too small for the size of the motor? not enough room to vent the pressure? sounds pretty bad. first you have to go to the trouble to FIND a J350, then the one you get catos, the guy next to you has his rocket blow up, and then the guy next to HIM has a CATO..... maybe I should be glad I did not try to talk my dad into useing a J350 in his Hydra for L2..... hate to have it blow up. he really likes that rocket.

Scott Binder used to own Binder Design... he sold it. Now he owns BSD -- the company that makes the Thor. He built a 7.5" upscale of it to fly at XPRS I. The motors were an N2000W, 3x J570Ws, and 3x J350Ws. Unfortunately, the N2000W was shipped with FWL grains instead of SWL grains... as such, the motor overpressurized instantly on the pad and destroyed the vehicle. There's a great centerfold photo in the XPRS I issue of Extreme Rocketry, Dec. 2002.

As for the J350Ws, it was a combination of a touchy motor and bad grains. Since the fire, AT has had Bob Ellis manufacture some of their propellant to help ease demand. Ellis was working in a more humid climate than Aerotech was used to casting propellant in -- and that affected the propellant. The binder and curative used absorbed water during the cure process. The metals in the propellant then reacted with this water, and created gas bubbles. The propellant became very "gassy". When a J350W with this propellant was lit, the bubbles were compressed to a fraction of their size, causing tears to appear in the propellant. Under pressure and acceleration, these chunks of propellant then rushed down the core and got jammed in the nozzle throat, causing a CATO. AT remedied this problem by increasing the core size, therefore decreasing initial Kn and thus initial chamber pressure. The motors then performed as normal. AT hasn't had a problem with the J350W since then. I fly them all the time. Don't be afraid of em now!

It was at NYPower 2 last year that the J350W fiasco started, trust me, I was there, and so was my dad's level 2 Bull Pup, baboom!!! That weekend saw the discovery of the J350W CATO issue, and the PRO38 CATO issue, all in the same weekend. Rob Dehate and Joel Rogers had a J330 PRO38 drag race, both CATO'd on the pad! There were countless CATO's all over the place, it was horrible.

There was also an I435T CATO in Mark Hanna's BBII, tried to spit forward closure, but fractured the casing just below the threads of the fore closure. Youch is all he had to say after that one, and the odd thing was that my dad's blew the J350W, then the immediate next launch was athe I435T. Oh the humanity!

Jeez. glad they fixed THAT problem! sounds brutal! did people just stop flying AT motors at that launch after they started going boom, or what? what did AT have to say about it, anyway? did they give people thier money back and pay for the damage, or did they just say "Whoopsie-daisy, that was NOT supposed to happen! sorry people."?

Yeah... My L2 project suffered a Pro38 J285 cato... I also had a J350 in my possestion, but with the 3/8" core. So I gave Aerotech a call, and they sent me the 1/2" grains, and I ordered two I161 dry loads, and used the old grains to make two I161 reloads. The I161 is such a sweet motor.

FYI, I believe that the J570 uses the Regular White Lightning Formula... Aerotech told me that when I asked if I can use the grains from a J570 to make a J350. They said no... the J570 was REG while J350 was Slow. Interesting.

BUT, maybe if you used a J570 nozzel in a J350 case with J570 grains..... that'd be cool. proablably illegal, though. by the way, what can you guys tell me about tube fins? any good way to figure out if it is stable? what do you use for lugs? I just whipped up a rocket with 6 TP tubes for fins, 2 paper towel tubes joined by a TP tube that is slightly larger than the paper towel tubes, and then a paper cup glued to another of the bigger tubes, which slips over the second paper towel tube, making a wicked funky lookin rocket, I will proabably make the cup into a cone with a bit of thick paper in a few minutes. this will be interesting......

Then (if it worked), it would not be a certified motor. That would also beat the purpose. Some people may ask, why not just use the J570... well then my rocket will outfly the field.

So just come out west, Doug :kill:

One way to solve THAT problem, but it makes other problems. as to my knowlege, you cannot fly rocket stuff on airplanes, though I may be mistaken, then if you could, the ticket cost to get from east coast to west coast, and the food, and all the other stuff. I do not think it is really worth making a trip just to launch 1 rocket. if it were LDRS, maybe, but otherwise, probly not.

Hence the reason for the :kill: smiley

I admit I am not learned in the ways of smileys. my entry into HPR may have just been delayed either to the 25th or sometime next year! not good! booh hoo! but there is still hope. I guess I should not despair yet.

I flew a J570 at NARAM this year. All the grains had a sticker on it that said "Slow White Lightning for use in the J570 only." They had to use slow, because with the longer motors you get erosive burning.

Ahh yes... erosive burning... yet another exciting topic to discuss...

When the nozzle throat diameter is equal to the core diameter of the grains, hot gases can flow out the nozzle at the speed of sound or greater. These gases also flow down the core of the motor at the speed of sound or greater, since they can exit the nozzle faster than they can exit the core. Really hot, flaming gases moving over a burning surface can cause nasty side effects.

So some motor designers make the core just a little larger than the nozzle throat. That way, they can fit the most amount of propellant in the motor without causing this disruptive flow. But when the diameters of the throat and core are really close, you get erosive burning. It's basically when these gases are flowing fast enough to decompose the oxidizer and propellant faster than the usual burn rate and thus causes an increase in chamber pressure. This pressure increase is maintained until the core becomes a little larger, the gases are slowed, and the disruptive flow stops. Some people design motors this way to give a thrust spike off the pad and then taper off for the duration of the burn.

Erosive burning is usually seen in longer motors like the J570W because the gases have a longer core distance to cover before exiting the nozzle throat. They just gotta travel faster to get there. To combat this, a slower propellant can be used, and the previous example of P_c increase until dropoff is effective (notice the violent initial thrust spike and resulting oscillations in the J570W thrust curve -- very cool). Some experimenters use a stepped core to reduce the erosive burning, which seems to work quite well. Mike Fisher of Binder Design has a 38mm K motor with a stepped core which works extremely well. The AMW Green Gorilla load for the 75/7600 case is also designed this way.

Hmm, this is turning into a propulsion theory thread

HTH.

OK, scratch that. Mike's 38mm K motor has a straight core BATES. But you still get the idea

Hmm... Diane told me wrong then about the J570... maybe what she meant to say was the J350 slugs are reg formula...

He is right about the M2500 GG... I seen plenty of those loads in action at the AMW plant. Here is a video of a M2500 ground test.

38MM K motor??!!!!?? do tell..... how long is it? THAT would be a motor for my mach buster 1!!!! droooooool drooooooollll..... Where does he get them? how much do they cost and who makes em?

I think those are custom made motors. I don't think you can buy them. Did you see the M2500 video?