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  #1  
Old 06-05-2005, 07:23 PM
Tweener's Avatar
Tweener Tweener is offline
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Default After the Fire

No this isn't about that '80's group that did an English language cover of Falcos's "Der Commissar". I'm finally settled into my new abode and organized well enough to build. One of my first projects is another Mean Machine bash of the Centuri Thunder Roc. I have decided to break from my previous opinion that a clone should be constructed as close to the original design as possible and take advantage of some of the other bits of tech available. One design mod will be to add an ejection baffle to eliminate the need for wadding. But I'm in need of some advice for the other. I'd like to put a 3 3/4" 24mm mount in the rocket to enable E power launches with Estes engines, and I have four questions.

1) If I choose to launch with a D, what do I use for a 1" spacer? (I'm thinking spent engine casing cut to size, cellophane taped to front of engine for ease of extraction.)

2) What E9 delay would be best for ejection at apogee?

3) Since an E9 doesn't have as high a thrust spike as the D12, will I need a longer rod than 36" for the rocket to become stable?

4) Will the 3/16" rod still be sufficient rather than 1/4"? ( I use 1 piece steel and not 2 piece aluminum, actually cheaper at the hardware store. )

I'm not rocksim literate, and when this is built it will be my first E power capable rocket. I don't want anyone to get hurt!
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  #2  
Old 06-05-2005, 08:40 PM
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A Fish Named Wallyum A Fish Named Wallyum is offline
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I built and flew a D-powered Thunder Roc a couple of years back. The only thing I used as a guideline was how the Mean Machines performed that I had seen fly. I'd seen several of them at club launches and none of them seemed to have even slight problems clearing the rod. As for the E flight, everything I've ever built to fly on an E has left the rod with plenty to spare. None have been as long as the Thunder Roc, but I've flown an upscaled Satellite Interceptor that was decidedly bulkier. I don't think the lack of initial punch is going to be much of an issue.
As for flying it on D motors after flying it on E's, do you really think you're going to come down the ladder? This isn't one for the local soccer field.
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  #3  
Old 06-05-2005, 09:19 PM
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CPMcGraw CPMcGraw is offline
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Exclamation ThunderRoc "E" conversion

Quote:
Originally Posted by Tweener
I'm in need of some advice... I'd like to put a 3 3/4" 24mm mount in the rocket to enable E power launches with Estes engines, and I have four questions.

1) If I choose to launch with a D, what do I use for a 1" spacer? (I'm thinking spent engine casing cut to size, cellophane taped to front of engine for ease of extraction.)


Two possibilities:

1 -- Get a 1" length of hard, black fishpaper "JT-50" coupler material.
2 -- Take two CR-2050 rings and a 1" length of BT-20. Glue the rings at each end.

Having said this, read on...

Quote:
2) What E9 delay would be best for ejection at apogee?


None. See question #3.

Quote:
3) Since an E9 doesn't have as high a thrust spike as the D12, will I need a longer rod than 36" for the rocket to become stable?


Much longer. Try 80". It doesn't become stable until it reaches 73". See the simulation file.

Quote:
4) Will the 3/16" rod still be sufficient rather than 1/4"? ( I use 1 piece steel and not 2 piece aluminum, actually cheaper at the hardware store. )


Should be, but you need to see the simulation file (attached) for the engine selection.

Quote:
I'm not rocksim literate, and when this is built it will be my first E power capable rocket. I don't want anyone to get hurt!


Don't sweat it, it comes with time. Just study the sim results carefully, and you'll get all the data you need.

This bird needs composite Aerotech motors (or their equivalents) to fly safely. The Estes BP motors just don't have the needed horsepower to kick this pig. The same applies to the Mean Machine, if you wanted to do the same thing with it.

Craig McGraw
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  #4  
Old 06-05-2005, 09:30 PM
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CPMcGraw CPMcGraw is offline
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Tweener,

You really don't need the "E" motor to get this rocket to fly well. On a D12, the simulator gives me 488', and it reaches flight velocity at 41", meaning you need a 48" rod.

The "E" motor gave me 934', but it needed an 8' rod to do it. That suggests more of a structural tower to keep it straight. Too much support tower for a one-bird project.

Craig McGraw
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  #5  
Old 06-05-2005, 09:34 PM
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A Fish Named Wallyum A Fish Named Wallyum is offline
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Default The Clone Wars - REVENGE OF GRIP IT AND RIP IT

Sounds like a challenge to me. I've spent the weekend halfheartedly gathering tubes for an E capable Thunder Roc rebuild. Now I've got some wind in my sails.
BTW, when I exhumed the corpse of my original Thunder Roc clone I found my missing 24" nylon chute.

Last edited by A Fish Named Wallyum : 06-05-2005 at 09:36 PM. Reason: Forgot the title
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  #6  
Old 06-05-2005, 09:54 PM
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CPMcGraw CPMcGraw is offline
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Quote:
Originally Posted by A Fish Named Wallyum
Sounds like a challenge to me. I've spent the weekend halfheartedly gathering tubes for an E capable Thunder Roc rebuild. Now I've got some wind in my sails.
BTW, when I exhumed the corpse of my original Thunder Roc clone I found my missing 24" nylon chute.


And to think, I just bought another Screamin' Mimi at the last HL sale...

I may have to do one of these myself...

Craig...
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  #7  
Old 06-05-2005, 10:14 PM
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Tweener Tweener is offline
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Quote:
Originally Posted by CPMcGraw
This bird needs composite Aerotech motors (or their equivalents) to fly safely. The Estes BP motors just don't have the needed horsepower to kick this pig.


(sigh) I had hoped to be able to fly on cheap (er) E power. How about the Aerotech E15-7W? Then I wouldn't even have to change the mount.
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  #8  
Old 06-05-2005, 10:55 PM
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CPMcGraw CPMcGraw is offline
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Smile

Quote:
Originally Posted by Tweener
(sigh) I had hoped to be able to fly on cheap (er) E power. How about the Aerotech E15-7W? Then I wouldn't even have to change the mount.


In the simulation drawing, I used a 6" motor mount, but installed the motor block at 3.5" from the rear of the tube.

The E15-7 is one of the motors I used in the list. The simulator hit 1518', and reached speed at 36.25". Still needs the 48" rod.

Best altitude was with the F24-7, with 1719'. Speed was reached at 27.2", meaning you can squeak by with a 36" rod here. I'd still use the 48" rod for the additional speed before free-flight.

Craig McGraw
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  #9  
Old 06-05-2005, 11:51 PM
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Tau Zero Tau Zero is offline
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Location: Twin Falls, Idaho, USA
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Talking "Kick a Pig!"

Quote:
Originally Posted by CPMcGraw
This bird needs composite Aerotech motors (or their equivalents) to fly safely. The Estes BP motors just don't have the needed horsepower to kick this pig.
"Kick a Pig." Now *there's* a name I'd like to see you use for one of your custom designs!

Cheers,

--Jay
(Who has both ATF and Falco versions of the following...)

"Don't turn around, woh-oh! (Ja, ja!) Der Komissar's in town..."
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  #10  
Old 06-06-2005, 12:16 AM
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CPMcGraw CPMcGraw is offline
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Quote:
Originally Posted by CenturiGuy
"Kick a Pig." Now *there's* a name I'd like to see you use for one of your custom designs!


OK, I've put the name into my list of "To Do Models". I've got to think about that one a bit first...

Craig
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