Ye Olde Rocket Forum

Go Back   Ye Olde Rocket Forum > Work Bench > Building Techniques
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 11-26-2008, 05:17 PM
aeromoe's Avatar
aeromoe aeromoe is offline
Advanced Rocketeer...of sorts. :)
 
Join Date: Sep 2006
Location: Arid-zona
Posts: 74
Default How deep to "nest" tubes for strength (HPR)

I'm starting to build my quarter scale Nike Ajax (single stage) This is a 4" dia Nike booster to a 3" dia Ajax. The rocket should end up just over 8ft and fly on 54mm motors. The two components will separate for transport but I'm trying to decided how deep into the Ajax the central tube should extend. The 3" Ajax tube serves as recovery gear compartment for the whole rocket so I need as much volume as possible.

My question, is how deep, in calibers, should the 54mm tube extend up into the 3"Ajax tube? This is pretty much where the strength is but it is also where the rocket separates for transport. Recovery separation is at the nose cone.

To add more strength, the 54mm tube that extends out of the Ajax will have two centering rings and LOC coupler/stiffy that fits just inside the top of the 4" Nike booster. Screws/tee-nuts will hold the two together for flight. The 54mm tube has a very thick wall coupler that fits into the upper end of the 54mm motor tube proper in the Nike booster.

Rocksim 8.0 file included for perusal. OF course, it's a rough drawing at the moment.

Thanks for any advice or help

Moe
Attached Files
File Type: rkt NikeAjax_QuarterScale.rkt (102.4 KB, 75 views)
Reply With Quote
  #2  
Old 11-28-2008, 09:05 PM
Mick Kelly Mick Kelly is offline
Intermediate Rocketeer
 
Join Date: Nov 2008
Posts: 36
Default

I am a firm believer that at a minimum 1.5 calibers is minimum. I usually use at least 2 calibers for coupler length. Allot of this depends on how well and what techniques are used for the coupler. Is it plain cardboard, phenolic or reinforced with composite materials.

Mick Kelly

Last edited by Mick Kelly : 11-28-2008 at 10:00 PM.
Reply With Quote
  #3  
Old 11-30-2008, 12:26 AM
aeromoe's Avatar
aeromoe aeromoe is offline
Advanced Rocketeer...of sorts. :)
 
Join Date: Sep 2006
Location: Arid-zona
Posts: 74
Default

Hi Mick - thanks for the reply. All tubes involved are LOC heavy wall cardboard. For this project - the Nike Ajax, I'm probably going to go with 2 - 2.5 calibers for the 54mm tube nested inside the 3" tube. There is no coupler involved here - just a couple of 1/4" plywood centering rings. The coupler that phyisically joins the two rockets together is a LOC 6" long standard coupler with the "stiffy" inside and standard plywood centering rings at both ends to center the 54mm tube.

Moe
Reply With Quote
  #4  
Old 11-30-2008, 11:03 AM
sandman's Avatar
sandman sandman is offline
Custom Cone, Kit & Decal Maker
 
Join Date: Mar 2005
Location: Way North of Detroit
Posts: 5,048
Default

Moe, sorry i didn't get a chance to answer your email on this...I got a bit side tracked.

If the model is only going to seperate for transport and it doesn't have to seperate at that point from ejection, then longer, at least 2 calipers is better.

You probably should have some type of retension so it doesn't seperate at ejection.

I'm thinking some type of srews. Something metal so they don't act like shear screws.
__________________
"I'm a sandman. I've never killed anyone. I terminate runners when their time is up." Logan from "Logan's Run"

http://sandmandecals.com/
Reply With Quote
  #5  
Old 12-01-2008, 08:03 AM
aeromoe's Avatar
aeromoe aeromoe is offline
Advanced Rocketeer...of sorts. :)
 
Join Date: Sep 2006
Location: Arid-zona
Posts: 74
Default

No worries G - it was Thanksgiving weekend afterall...

The area where the nesting occurs is a solid bond... I'm thinking of 8 inches or so (over 2 calibers) for this area. The separation point for storage is at the top of the Nike booster and will have a LOC 4" diameter coupler plus six 10-24 threaed into tee nuts in the coupler to secure for flight.

I'm gonna be ordering that nose cone by the way...
Reply With Quote
  #6  
Old 12-01-2008, 08:07 AM
sandman's Avatar
sandman sandman is offline
Custom Cone, Kit & Decal Maker
 
Join Date: Mar 2005
Location: Way North of Detroit
Posts: 5,048
Default

Quote:
Originally Posted by aeromoe
No worries G - it was Thanksgiving weekend afterall...

The area where the nesting occurs is a solid bond... I'm thinking of 8 inches or so (over 2 calibers) for this area. The separation point for storage is at the top of the Nike booster and will have a LOC 4" diameter coupler plus six 10-24 threaed into tee nuts in the coupler to secure for flight.

I'm gonna be ordering that nose cone by the way...


Thanks for understanding. My grandaughter was here and at 10 months she's very mobile now and quite a handfull.

But fun!
__________________
"I'm a sandman. I've never killed anyone. I terminate runners when their time is up." Logan from "Logan's Run"

http://sandmandecals.com/
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 04:22 AM.


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