Ye Olde Rocket Forum

Go Back   Ye Olde Rocket Forum > The Golden Age of Model Rocketry > Model Rocket History
User Name
Password
Auctions Register FAQ Members List Calendar Today's Posts Search Mark Forums Read


Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 08-02-2009, 10:57 AM
otis otis is offline
Intermediate Rocketeer
 
Join Date: Apr 2007
Posts: 62
Default Pro-Jet Motors

I was looking over a selection of old Composite Dynamics Pro-Jet motors the other day and noticed an interesting thing about them. 2 apparantly identical E-20 motors with different molded nozzles. Both nozzles appear to be made out of white plaster? (Plaster of Paris ??) but at any rate the same material. However, some of the motors have a clearly molded expanding nozzle while others just have a molded hole. (no expansion, just a straight hole). I was just wondering if anyone knows the story behind this. It seems it would be just as easy to mold one as the other. One would assume the expanding nozzle would give better performance????
I know Gary used to work for Composite Dynamics so if you would like to chime in please do. This is not an oddball motor as I have seen several different examples of this even in different size motors. (ie F-40's)
I have incuded pictures of the nozzles that hopefully can be seen. Motor on the left has a date code of 2/B with the year? 80 written below it. It clearly has an expanded nozzle molded into it. The one on the right has a code of 81-6 and it only has a straight hole for the nozzle.
Anybody have any thoughts on this?
Attached Thumbnails
Click image for larger version

Name:  pro-jrt 005.jpg
Views: 108
Size:  267.7 KB  Click image for larger version

Name:  pro-jrt 003.jpg
Views: 104
Size:  186.0 KB  Click image for larger version

Name:  pro-jrt 007.jpg
Views: 112
Size:  252.9 KB  
Reply With Quote
  #2  
Old 08-03-2009, 09:00 AM
Chas Russell's Avatar
Chas Russell Chas Russell is offline
Retired Missile Technician
 
Join Date: Mar 2005
Location: Fort Worth, TX
Posts: 1,076
Default

Gary owned Composite Dynamics, or as it was sometimes known "Composte Dynamite" (in the nicest way).

They simplified manufacturing by placing a washer over the propellant and the simple ceramic material over that. When the motor fired it generated its own nozzle. I have a bunch of these motors, but don't recall firing any of the "nozzleless" ones.

Chas
Reply With Quote
  #3  
Old 08-03-2009, 10:07 AM
ghrocketman's Avatar
ghrocketman ghrocketman is offline
President, MAYHEM AGITATORS, Inc.
 
Join Date: Jul 2005
Location: Nunya Bizznuss, Michigan
Posts: 13,443
Default

All of the ones I have have the simple hole with no visible "nozzle"
Actually launched an E20-7 last year and it flew perfectly in an old Maxi-Alpha 3; ejection actually happened ~7sec after burnout. I expected no ejection for a lawn dart !
__________________
When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL
, if you have to ask what is "NORMAL" , you probably aren't !

Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, and HAVOC !
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 03:34 PM.


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