Help! Why would this happen?

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Evilash

Well-Known Member
Joined
Jun 24, 2014
Messages
320
Reaction score
1
I lawn darted an Estes Partizon a few launches ago and I did not think too much of it, just maybe too much wadding or something normal. Then photos were posted by a photographer that comes out and I see the nose cone has slid up right off the rod for some reason... Does anyone know why this happens so I can avoid the same mistake next time?

15856807745_bdd738f315_o.jpg15856163002_e4020ec58a_o.jpg15237150263_826a48007c_o.jpg
 
Last edited:
Guessing your motor leaked during startup but then sealed itself. Need more info about your settup. What motor? I assume this was recovery by motor ejection?
 
It was a Aerotech G64-7 in a Monster Motors 40/120 29mm casing. It was motor ejection. It was the first time I used that casing.
 
Even loose, coming off the rail the NC should be on. it's under full thrust so it's not drag sep and it's too low to have popped from pressure difference.

Only thing I can think is that the delay wasn't sealed and it blew by and ignited the charge. Being under thrust it wasn't enough to clear the NC from the tube.

Do you recall what steps you took in building the delay assembly?
 
I still follow the paper directions when loading one of those hobby reloads. I don't remember what I had for breakfast an hour later so I don't trust my memory to not forget a o-ring or something. The chute never deployed but the charge did go off. There was nothing fancy like bulkheads on this rocket and it had a proper sized pressure relief hole since I flew it on H's before without issue. Here is an after shot, it went down straight as an arrow.
DSC_0081.jpg
 
not necessarily anything you did, could just have been an oring failure. But other than the charge going off, I don't see anything forcing the NC off that low.

I could be very wrong too. I'm interested to see what others think.
 
This may bot pertain to you..but it is possible to leave the seal gasket or delay o-ring in the forward closure after dumping the spent motor remains.

On the black AT closures you really gotta look..when you clean the closure and when you are loading up too.

Having an Exacto in the range box is ideal for getting them out and also to round out the closure hole and nozzle.

They may not do the Hobbyline size motors with the RMS EZ replacements , but the welcone new style also eliminates cleaning the dirty closure when the flying is done.

Kenny
 
First, Tanks for helping everyone.

I guess there could have been an old O-ring in that casing, I honestly did not look that hard since it was given to me by someone who knew I needed another one for a 4 29SS but it is gold so unlike the black Aerotech one, it would be harder to miss. A failure in the O ring or user error is the most likely culprit from what you all are saying. I dont mind making mistakes, its how you learn, and I learn on a regular basis.

I could see myself not greasing the O ring enough... or just having a brain cloud and assembling it wrong.
 
I'd would want to check the casing very closely to make sure it was not damaged, but suspect not.

As for the chute not deploying, it may have been due to the nosecone not being on straight at liftoff and being jammed down from acceleration and drag.
 
The Partizon has a large sloping area on its nosecone's shoulder, which is there to allow the attachment point to be molded. One problem that the Leviathan and the Big Daddy has (similar shape to the shoulder) is that the pressure apparently can (occasionally) be insufficient to blow the nosecone clear before venting out of the sloped area. Thus lawndarts seem to be more frequently reported on the forums with those rockets. I wouldn't say that this caused the problem in the first place, but might explain why the nosecone didn't blow clear if the ejection charge went off prematurely.

For all my PSII builds, I'm now planning on modifying the nosecone's shoulder to reduce/eliminate this slope before launching them to prevent this from happening to me.
 
Last edited:
Interesting about the slope, what would you use to build that up? Good pics of darts in the thread link you included.

I never thought of the chute being shoved down due to the cone being off, that very well could have been the case. Too bad I somehow lost the memory card for the pen cam on that rocket, that may have been an interesting study.
 
Interesting about the slope, what would you use to build that up? Good pics of darts in the thread link you included.

I never thought of the chute being shoved down due to the cone being off, that very well could have been the case. Too bad I somehow lost the memory card for the pen cam on that rocket, that may have been an interesting study.

If the shoulder is long enough just cut off the sloped section and put a plywood bulkhead in NC just ahead of the shoulder with a eyebolt/ubolt/kevlar or nylon loop. John Coker has a video of modifying a NC this way, not only do you increase the area for chute storeage, but the NC is all the way off before ejection gases start escaping.
 
I found that video, cool idea! Thanks for pointing me in that direction.
 
Did the motor happen to have a hard chuff at ignition? I bet under the right circumstances it could jar a nose one loose like that......
 
Any chance that the way the chute was packed, especially using a stretchable shock cord, that the chute expanded inside the BT and popped the cone?

BTW, I don't think anyone asked -- could you life the assembled (i.e., motor in place) rocket by the nose cone without it coming out?
 
There was not a hard chuff, it lit flawlessly but yes, I agree that could have caused it.

I could lift it without it coming out as long as I was careful, it seemed to have the right amount of friction. The parachute was stuck in there pretty good but who knows if that happened due to the cone being loose on the way up or not.
 
Did you sim the rocket on this motor? Just wondering how many Gs you pulled off the pad and also how much the nose cone weighs.
 
I did sim it with open rocket, it is showing 10gs off the rod
SullyG_edited-1.jpg

I really wish my altimeter 2 was able to survive the lawn dart to see what kind of force it experienced at the end.
 
Back
Top