Ye Olde Rocket Forum

Go Back   Ye Olde Rocket Forum > Work Bench > Projects
User Name
Password
Auctions Register FAQ Members List Calendar Today's Posts Search Mark Forums Read


Reply
 
Thread Tools Search this Thread Display Modes
  #21  
Old 04-05-2011, 08:49 AM
Bill's Avatar
Bill Bill is offline
I do not like Facebook
 
Join Date: Sep 2008
Location: North Tejas
Posts: 3,087
Default

Quote:
Originally Posted by Randy
[QUOTE=Earl]
>Anyone else confirm this general rule? You don't hear folk talk much about the ol' Krushnic effect anymore.

I think it's not talked about too much because 99% of the rockets being flown all have the engines at or below the bottom of the bt. I have only seen it happen once to another flyer who set his rocket about a half inch off the blast plate. It didn't go anywhere and burned about 75% of the rocket before it was extinguished.



It is somewhat surprising that does not happen more with The Launch Pad kits. Most of their motor mounts are recessed.


Bill
Reply With Quote
  #22  
Old 04-05-2011, 10:09 AM
DaveR's Avatar
DaveR DaveR is offline
Master Modeler
 
Join Date: Apr 2006
Location: North MS
Posts: 836
Default

Quote:
Originally Posted by Earl
I seem to recall a very general rule of thumb on preventing the Krushnic effect by recessing the motor (i.e., specifically the exit plane of the nozzle) to NO MORE THAN one body diameter. In the case of the Saturn V, that'd be just about 4 inches, so a 3 and 3/8", it would seem by that general rule you'd be ok.

Anyone else confirm this general rule? You don't hear folk talk much about the ol' Krushnic effect anymore.

Earl

That's the rule I remember, but I didn't know how big the tube was on a Sat V. Even so, 3 3/8 seems like a lot.

I've never seen the Krushnic effect occur, but it might be cool to see. (In a twisted rocket destroying sort of way. )
__________________
Dave
Fire is the leading cause of fire.
Was once SAM#0132
Reply With Quote
  #23  
Old 04-05-2011, 10:27 AM
JumpJet's Avatar
JumpJet JumpJet is offline
Master Modeler
 
Join Date: Apr 2008
Location: Pueblo Colorado
Posts: 1,307
Default

It has happened to me with my Upscale Centuri Point which is nothing more then a big paper cone. Nothing better then seeing a D12 motor thrusting away while the rocket sits on the pad turning brown from the inside out. The only thing left was the nose cone.

John Boren
Reply With Quote
  #24  
Old 04-05-2011, 02:40 PM
tbzep's Avatar
tbzep tbzep is offline
Dazed and Confused
 
Join Date: Mar 2005
Location: TN
Posts: 11,610
Default

Quote:
Originally Posted by JumpJet
It has happened to me with my Upscale Centuri Point which is nothing more then a big paper cone. Nothing better then seeing a D12 motor thrusting away while the rocket sits on the pad turning brown from the inside out. The only thing left was the nose cone.

John Boren


Sounds funny to watch in person....unless it happens to me.
__________________
I love sanding.
Reply With Quote
  #25  
Old 04-05-2011, 03:25 PM
hcmbanjo's Avatar
hcmbanjo hcmbanjo is offline
When Pigs Fly!
 
Join Date: Sep 2005
Location: Orlando, FL
Posts: 1,102
Default

Quote:
Originally Posted by JumpJet
It has happened to me with my Upscale Centuri Point which is nothing more then a big paper cone. Nothing better then seeing a D12 motor thrusting away while the rocket sits on the pad turning brown from the inside out. The only thing left was the nose cone.

John Boren


That happened to my (regular sized) Centuri Point in the mid 1970s.

If I remember correctly, the Semroc instructions said to raise it above the blast deflector.
The Centuri instructions didn't mention this.
Mine was set down flat on an Estes round blast deflector, the deflector diameter was a little wider than the base of the Point.
It was almost like there was "suction" holding it down to the launcher.
The Centuri blast deflector was angled, not flat.

My mother would take me to the ranch to fly rockets back then.
I can still hear her laughing when it caught fire.
She sarcastically said: "Well, that was different".

The Point -
"Build it - Watch it fly - And wonder why!"
Then go home
__________________
Hans "Chris" Michielssen
Old/New NAR # 19086 SR

www.oddlrockets.com
www.modelrocketbuilding.blogspot.com
http://www.nar.org/educational-reso...ing-techniques/
Your results may vary
"Nose cones roll, be careful with that."
Every spaceman needs a ray gun.
Look out - I'm the Meister Shyster!
Reply With Quote
  #26  
Old 04-05-2011, 03:41 PM
Bill's Avatar
Bill Bill is offline
I do not like Facebook
 
Join Date: Sep 2008
Location: North Tejas
Posts: 3,087
Default

The Point -
"Build it - Watch it fry - And wonder why!"
Reply With Quote
  #27  
Old 04-05-2011, 06:17 PM
Scott6060842 Scott6060842 is offline
Master Modeler
 
Join Date: Sep 2010
Location: NW Pennsylvania
Posts: 665
Default

I bought a Semroc point (never knew the history of it till recently) to round out my Xmas order. Im going to pull it down and build it. I find the FRY potention appealing in a weird sort of way.
Reply With Quote
  #28  
Old 04-06-2011, 04:21 PM
cas2047's Avatar
cas2047 cas2047 is offline
Master Modeler
 
Join Date: Jun 2006
Location: MA, NH
Posts: 1,532
Default

I made some progress on the build.

The third stage components have been assembled. The only change I made was that I used Kevlar cord on the third stage centering ring instead of a doubled up piece of line called for in the instructions. I'm filling spirals now.

The L.E.M. components have been assembled. I'm filling spirals now.

The nozzles have been assembled, primed, and are being painted. I figure anywhere I can get a jump on any of the painting I'm going to do that along the way.

All wraps have been cut out, and that took a LONG time... I still have to do a bit of sanding before I apply them to the tubes.

Now I just need to pickup the glues I need to attach the wraps so I glue them in place.
Attached Thumbnails
Click image for larger version

Name:  Third stage and L.E.M.jpg
Views: 158
Size:  129.6 KB  Click image for larger version

Name:  Test Fit.jpg
Views: 166
Size:  112.1 KB  Click image for larger version

Name:  Wraps.jpg
Views: 135
Size:  115.7 KB  
__________________
I plan ahead that way I don't have to do anything right now.

Oh by the way, I'm not here just for the "olde" rocket discussions.
Reply With Quote
  #29  
Old 04-06-2011, 06:34 PM
jeffyjeep's Avatar
jeffyjeep jeffyjeep is offline
Old Submariner
 
Join Date: Jan 2009
Location: Home of Wayne & Garth
Posts: 7,760
Default

Looking good! Are you going to put Sandman's SM wrap on it?
__________________
Never trust an atom. They make up everything.

4 out of 3 people struggle with math.

Chemically, alcohol IS a solution.

NAR# 94042
SAM# 0078
Reply With Quote
  #30  
Old 04-06-2011, 06:58 PM
Bill's Avatar
Bill Bill is offline
I do not like Facebook
 
Join Date: Sep 2008
Location: North Tejas
Posts: 3,087
Default

What did you finally decide to do with the motor mount position? If you are concerned about burning, consider taping a protective strip of printer paper or even aluminum foil around the inside the tube.


Bill
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump



All times are GMT -5. The time now is 01:01 PM.


Powered by: vBulletin Version 3.0.7
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Ye Olde Rocket Shoppe © 1998-2024