Plugged Closure and Delay Element

[FredA]

Whoever your mentor is, they don't know jack. You ALWAYS put the delay grain in a reload, failure to do so voids any and all warrantees.

Yes - time for new mentor.
Choose carefully.

 

[cwbullet]

Whoever your mentor is, they don't know jack. You ALWAYS put the delay grain in a reload, failure to do so voids any and all warrantees.

Dude, reading is fundamental. It is not my mentor. My mentor taught me right. The person t=with the CATO was a student. The mentor for the students taught them to leave it out.

 

[manixFan]

In addition to grease on the top of the delay grain, I was also told to fill the delay well with wadding and then tape over it with electrical tape - an X over the top and then a piece around the circumference to hold it in place well. (Pretty much like if had powder in it.) That would help minimize any flame from shooting out the touch hole.

It would be interesting to video a motor and see how much flame comes out the charge well. I know that with the old-style drilled delays the amount of flame could be considerable, especially with short delays that had a lot of the delay element burning after the ejection charge. But since reload delays don't really break through until they are nearly done burning I suspect there is not a lot of flame.


Tony

 

[ksaves2]

In addition to grease on the top of the delay grain, I was also told to fill the delay well with wadding and then tape over it with electrical tape - an X over the top and then a piece around the circumference to hold it in place well. (Pretty much like if had powder in it.) That would help minimize any flame from shooting out the touch hole.

It would be interesting to video a motor and see how much flame comes out the charge well. I know that with the old-style drilled delays the amount of flame could be considerable, especially with short delays that had a lot of the delay element burning after the ejection charge. But since reload delays don't really break through until they are nearly done burning I suspect there is not a lot of flame.


Tony

I agree but one would have to clamp the motor securely to a heavy weight and test fire it upright. The research guys usually dig a hole and put the nozzle end up for a test fire and use a plugged closure. I agree with using wadding and tape. I like to use a delay grain for the smoke that it provides and I just order the longest burning one in the flights I use electronics for deployment. The extra smoke can be helpful. I can't see myself flying without a smoke grain.
Kurt

 

[Rocketjunkie]

If not using the ejection, assemble normally including the O-rings, etc. Leave out the BP ejection charge. This will work for ANY motor and remains certified. I have a few closures where I have tapped the touch hole 6-32 and inserted a screw and filled the well with epoxy. For research motors only. Can fill the plugged closure with epoxy. These are permanent closures and you don't need smoke grains or closures.

 

[Dugway]

You could always use the Aerotech endburning forward closure. Has no hole for the delay grain or black powder.

 

[manixFan]

I agree but one would have to clamp the motor securely to a heavy weight and test fire it upright. The research guys usually dig a hole and put the nozzle end up for a test fire and use a plugged closure. I agree with using wadding and tape. I like to use a delay grain for the smoke that it provides and I just order the longest burning one in the flights I use electronics for deployment. The extra smoke can be helpful. I can't see myself flying without a smoke grain.
Kurt

I've video taped dozens of motor tests, but always the other end. I don't see why it would have to be fired upright - the flame will be visible from any direction. The issue is modifying the stand so the front of the motor is visible - it's normally enclosed in a motor tube.


Tony

 

[beeblebrox]

Issues with AeroTech LMS motors occur too from not following directions. These motors seal up the same way as a reload with regard to the position of the delay element. There was a CATO Sunday at MDRA due to an LMS motor assembled with the delay spacer forward of the delay element. The delay element MUST be flush against the yellow forward closure in order to seal. Inspection of another motor purchased by my friend made the problem clear. (These were assembled when he purchased them...) You can leave out the black powder on these as well if you are using them in a cluster or using electronic ejection. The delay element is there, might as well get the smoke.

 

[jimzcatz]

Apologies Chuck, I misunderstood.

 

[cwbullet]

Apologies Chuck, I misunderstood.

No biggie. I was grumpy from a day on the field. Good news is I had 5 flights. Most in one day in 3 years.

 

[Sandy H.]

I feel for the RSO/LCO in this situation. How are you supposed to catch this issue without asking a million questions or watching assembly for each rocketeer. Not possible/practical.

I know nothing of the actual events, but one that seems to lead to a logical scenario of small changes leading to the failure would be:

Seasoned flier L1 and L2, many flights. Decided to add to the challenge by adding electronic deployment to the toolbox for the first time. While focusing on the electronics, someone mentions that the electronics are so good now that you don't need to rely on redundant motor deploy, so just leave that out, as it could be another point of failure. Flier sees the logic and misinterprets what that means and leaves the delay out, not just the BP, as they were focusing on the new aspect of the flight with electronics and just took a passing suggestion from a seasoned flier about leaving the motor ejection out at face value, not really thinking about it and understanding what they really meant. I imagine about 0.5 seconds after the go button got pushed, the flier saw the issue in their prep. . .

Again, I hope the rocket is easily repaired and the case cost (assuming total loss there, except for aft closure) isn't a problem.

I hope the Sunday winds were more favorable and glad to hear you got 5 rockets up. I'm betting you used 5 igniters as well. . .I'm hoping to bring my igniter usage vs. flights flown closer to unity next launch. . .

Sandy.

 

[FredA]

Perhaps it was a simple mistake as Sandy portrays.
But it should be obvious NOT TO CHANGE anything INSIDE a certified motor.

 

[cwbullet]

I hope the Sunday winds were more favorable and glad to hear you got 5 rockets up. I'm betting you used 5 igniters as well. . .I'm hoping to bring my igniter usage vs. flights flown closer to unity next launch. . .

Sandy.

Yes. I tossed 5 Aerotech igniters aside and used 5 of mine with 5 lit and fit motors fired. Great thing.

 

[cwbullet]

Perhaps it was a simple mistake as Sandy portrays.
But it should be obvious NOT TO CHANGE anything INSIDE a certified motor.

I do not think it was nefarious. The "mentor" was also a flier and reported success doing this in the past with smaller motors. The CATOs I have seen were all with 38mm motors and I-J range. I was serving as LCO and a witness for certifications. It was a TRA launch.

I have inserted a few questions for our RSOs that I will probably ask to be asked in check list fashion....."in assembling your motor, were there any extra parts or parts left over such as the delay grain?".

 

[Banzai88]

I have inserted a few questions for our RSOs that I will probably ask to be asked in check list fashion....."in assembling your motor, were there any extra parts or parts left over such as the delay grain?". And if it's a CTI 38mm, did you put the reload in the case BEFORE installing it in the rocket?

Don't forget the case, too!

Been a loooooong time since I was at a launch where the RSO sign off was functionally anything more than a 'shoot the $*#&@ about how cool me and my rocket are' type of speed bump, instead of the safety toll gate that I've always thought that it should be.

 

[dhbarr]

Don't forget the case, too!

Been a loooooong time since I was at a launch where the RSO sign off was functionally anything more than a 'shoot the $*#&@ about how cool me and my rocket are' type of speed bump, instead of the safety toll gate that I've always thought that it should be.

I definitely get a pretty standard list of questions: did I build it, is it a kit, where's the CG, where's the CP, what's the weight, what's the motor, usually while tugging on my fins and retainer. Not sure anyone's ever asked me about building the motor, put presumably if I told them it was a Warp or whatever they'd probably ask me about the delay and electronic situation.

 

[FredA]

a flier and reported success doing this in the past with smaller motors.

This is a BIG problem in this hobby, IMHO.
Not understanding and doing something because "it worked in the past", "it worked in smaller motors", or "I read/heard somebody did it that way and it worked for them."

I see it with motor building and a lot with ejection charge / sheer-pin sizing.

That's not a good operative mode for our hobby.

 

[cwbullet]

This is a BIG problem in this hobby, IMHO.
Not understanding and doing something because "it worked in the past", "it worked in smaller motors", or "I read/heard somebody did it that way and it worked for them."

I see it with motor building and a lot with ejection charge / sheer-pin sizing.

That's not a good operative mode for our hobby.

That is a great reason for ground testing. I had a rocket that was unstable this weekend. It was a design that was impossible to model in rocksim. I started small - BT70 and not high power to to test the design. If I had done this with a high power motor, it could have hurt someone bad. Now, I know I need more nose weight. I am not sure why people go off words and do not ground test or start small with flights.

I found a blind spot in our questioning at the RSO level (not a person) as a club. It can be rectified with a single question. We assume the certified mentor witnessed the motor being built. That is not always the case.