Ye Olde Rocket Forum

Go Back   Ye Olde Rocket Forum > Semroc > SAM - Semroc Astronautic Modeler Team
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 08-28-2011, 12:07 PM
Carl@Semroc's Avatar
Carl@Semroc Carl@Semroc is offline
Junior ??? Rocketeer
 
Join Date: Mar 2005
Location: Knightdale, NC
Posts: 1,470
Default 10mm Engines

We started refitting "Mabellette" to produce 10mm engines just before we left for NARAM. Over the last few weeks we have been able to finish the tooling and make adjustments to the machine and program. Mabellette works great and the engines look very good. There is just one small problem...

At between 3 and 5 seconds into the delay, the casing burns through on many of the engines. We had never noticed before that the first 1/8" of the inner (beginning) wrap does not have any glue. The failure always occurs at the unglued seam just above the nozzle. It does not matter if the delay is a fast burning (10sec/inch) or slow burning (30sec/inch) type. It is still around 5-7 seconds of total time since ignition. Replacing the delay with BP gives a 2+ second burn with no case weakness.

This is disheartning. We were trying to get about a thousand ready to give to the FAI team at the Capital Cup next month to use as practice engines over the next year. I am sorry for the SAM members that were anticipating the 10mm engines.

Perhaps this is a manufactuing flaw or it may be a problem just associated with very small tubes. They were made by New England Paper Tube, the original engine tube company for Estes and others. The 18mm casings made at the same time do not have the problem. I will be following up with NE this week.

Bruce said the upside is that we have B14's quicker and 18mm engines work in most of our current kits. I still hope we can make the 10mm work.
__________________
Carl McLawhorn
NAR#4717 L2
semroc.com
Reply With Quote
  #2  
Old 08-28-2011, 12:21 PM
CPMcGraw's Avatar
CPMcGraw CPMcGraw is offline
BARCLONE Rocketry
 
Join Date: Mar 2005
Location: Mobile, Alabama
Posts: 5,357
Default

Quote:
Originally Posted by Carl@Semroc
We started refitting "Mabellette" to produce 10mm engines ... one small problem...

At between 3 and 5 seconds into the delay, the casing burns through on many of the engines ... It does not matter if the delay is a fast burning (10sec/inch) or slow burning (30sec/inch) type. It is still around 5-7 seconds of total time since ignition. Replacing the delay with BP gives a 2+ second burn with no case weakness...


Sounds like the delay grain burns a bit hotter than the propellant grain. If replacing the delay with BP doesn't cause a burn-through, then it must be a temperature issue. Are there any delay grains that burn at a lower temperature?
__________________
Craig McGraw

BARCLONE Rocketry -- http://barclone.rocketshoppe.com
BARCLONE Blogsite -- http://barclone.wordpress.com
BARCLONE Forum -- BARCLONE Forum

BARs helping BARs

SAM 0044
AMA 352635
Reply With Quote
  #3  
Old 08-28-2011, 12:23 PM
BEC's Avatar
BEC BEC is online now
Master Modeler
 
Join Date: Feb 2009
Location: Auburn, Washington
Posts: 3,026
Default

Even though I'm not a likely customer for the 10mm motors, I'm sorry to hear this.

And....I hope you and yours are not too wet from the storm. Obviously you have power you you wouldn't be posting right now. Do take care!
__________________
Bernard Cawley
NAR 89040 L1 - Life Member
SAM 0061
AMA 42160
KG7AIE
Reply With Quote
  #4  
Old 08-28-2011, 12:36 PM
Carl@Semroc's Avatar
Carl@Semroc Carl@Semroc is offline
Junior ??? Rocketeer
 
Join Date: Mar 2005
Location: Knightdale, NC
Posts: 1,470
Default

Quote:
Originally Posted by CPMcGraw
Sounds like the delay grain burns a bit hotter than the propellant grain. If replacing the delay with BP doesn't cause a burn-through, then it must be a temperature issue. Are there any delay grains that burn at a lower temperature?

It is hard to see since there is so much ash, but when the 1/8" flap moves away slightly from the tube, it appears that it causes a swirl or vortex at the joint where the glue starts.

The slow delay generates much less heat and gas, so it seems to be a time issue.
__________________
Carl McLawhorn
NAR#4717 L2
semroc.com
Reply With Quote
  #5  
Old 08-28-2011, 12:38 PM
Carl@Semroc's Avatar
Carl@Semroc Carl@Semroc is offline
Junior ??? Rocketeer
 
Join Date: Mar 2005
Location: Knightdale, NC
Posts: 1,470
Default

Quote:
Originally Posted by BEC
Even though I'm not a likely customer for the 10mm motors, I'm sorry to hear this.

And....I hope you and yours are not too wet from the storm. Obviously you have power you you wouldn't be posting right now. Do take care!

Yeah, the 10mm are definately a specialty engine. I know the market is very small, but we have really wanted to do something to help the FAI team be more competitive.
__________________
Carl McLawhorn
NAR#4717 L2
semroc.com
Reply With Quote
  #6  
Old 08-28-2011, 01:42 PM
STRMan's Avatar
STRMan STRMan is offline
Master Modeler
 
Join Date: Nov 2007
Posts: 871
Default

The only thing I picked up in this whole thread was "B14"
__________________
"AND I hope they are from the planet of the "Chunk spunky Mary-Lou Retton clones". - Ironnerd

"Those who trade liberty for security have neither" - Benjamin Franklin

"Semroc is almost always the answer" - Stefanj

www.paulsavia.com

www.soundclick.com/paulsavia
Reply With Quote
  #7  
Old 08-28-2011, 04:22 PM
Ltvscout's Avatar
Ltvscout Ltvscout is offline
Ye Olde Rocket Shoppe
 
Join Date: Jun 2004
Location: Milwaukee, WI
Posts: 5,990
Default

Quote:
Originally Posted by STRMan
The only thing I picked up in this whole thread was "B14"

Ya, me too. It was like, "Asdg dfgdfg f hf hfhfdhfg hfxg h fgh fgh f hfg hfgj B14 dfh fgfsg hfg hgh fg jfggdhj."
__________________
Scott D. Hansen
Ye Olde Rocket Shoppe - Your One Stop BAR Shoppe!
Ye Olde Rocket Plans - OOP Rocket Plans From 38 Companies!
Ye Olde Rocket Forum
WOOSH NAR Section #558
Reply With Quote
  #8  
Old 08-28-2011, 05:50 PM
Mark II's Avatar
Mark II Mark II is offline
Forest Sprite
 
Join Date: Dec 2006
Location: Back Up in the Woods
Posts: 3,657
Default

I would buy them for sport flying. They are something different. They would sent my BT-4 micro rockets into the stratosphere. Especially if I could stage them.
__________________
Mark S. Kulka NAR #86134 L1,_ASTRE #471_Adirondack Mountains, NY
Opinions Unfettered by Logic Advice Unsullied by Erudition Rocketry Without Pity
+09281962-TAK-08272007+
SAM # 0011
Reply With Quote
  #9  
Old 08-28-2011, 05:59 PM
Chas Russell's Avatar
Chas Russell Chas Russell is offline
Retired Missile Technician
 
Join Date: Mar 2005
Location: Fort Worth, TX
Posts: 969
Default

Carl,
Good to hear that you got through Irene alright. My daughter lives outside of D.C. and seemed disappointed...

Have you tried to make a few motors after running a swab with either CA or white glue down to tubes to verify that the loose flap is indeed the problem? I can appreciate that this might be a lot of work to verify the problem, but it would add some verification when you talk with the tube manufacturer.
Just a thought from a non-engineer missile technician.

Chas
__________________
Charles Russell, MSgt,USAF (ret.)
NAR 9790, Lvl 1
SAM "Balls Three"
Reply With Quote
  #10  
Old 08-28-2011, 06:19 PM
Carl@Semroc's Avatar
Carl@Semroc Carl@Semroc is offline
Junior ??? Rocketeer
 
Join Date: Mar 2005
Location: Knightdale, NC
Posts: 1,470
Default

Quote:
Originally Posted by Chas Russell
Carl,
Good to hear that you got through Irene alright. My daughter lives outside of D.C. and seemed disappointed...

Have you tried to make a few motors after running a swab with either CA or white glue down to tubes to verify that the loose flap is indeed the problem? I can appreciate that this might be a lot of work to verify the problem, but it would add some verification when you talk with the tube manufacturer.
Just a thought from a non-engineer missile technician.

Chas
Good thinking. I had thought of that briefly and since you did too, maybe it is time to try it. I just have not figured out the best way of doing it. The tab is tight against the tube. It would have to be very viscous to seep under the edge. First attempt will be CA using an insulin needle from one end. If it runs out the other end, it will probably be a good check.

I am not ready to give up yet and appreciate any more suggestions.
__________________
Carl McLawhorn
NAR#4717 L2
semroc.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 06:15 PM.


Powered by: vBulletin Version 3.0.7
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
Ye Olde Rocket Shoppe 1998-2021