CTI reload question

Exactimator

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I'm not familiar with the CPR, but you can modify the CTI charges. What's your goal?
 

dhbarr

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Yes, you can downsize or remove the CTI charge and / or use a Piston w/w/o Altimeter as appropriate.
 

Keisling

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I do it all the time. I just remove the paper disk and dump the powder (sometimes takes some scraping to get it all). Then I squirt a blob a grease in the powder well, fill the rest with dog barf and top it off with a strip of masking tape.
 

manixFan

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I do it all the time. I just remove the paper disk and dump the powder (sometimes takes some scraping to get it all). Then I squirt a blob a grease in the powder well, fill the rest with dog barf and top it off with a strip of masking tape.
I do exactly the same thing, although I omit the grease. The disc covering the bp can sometimes be hard to remove since it's a bit slippery but the point of an exacto blade makes it easy to grab. Save the bp in a film can or other small container for future use.

You can also augment the ejection charge by simply adding extra powder on top of the paper disc and then covering securely with several layers of tape. I've done this when I had long body tubes or weighted nose cones and need extra oomph to get the laundry out.


Tony
 

JimJarvis50

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Since there can occasionally be an early burn-through of the ejection grain, I pot the charge well with epoxy. Oh yes, and I put in a penny. It's kind of difficult to blow that out.

And if it's a 54mm motor, be sure to glue in the forward closure. That'll save a rocket at some point too.

Jim

IMG_1249.jpg
 

jrkennedy2

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Since there can occasionally be an early burn-through of the ejection grain, I pot the charge well with epoxy. Oh yes, and I put in a penny. It's kind of difficult to blow that out.

And if it's a 54mm motor, be sure to glue in the forward closure. That'll save a rocket at some point too.

Jim

Will a penny work well enough? I am concerned that zinc will melt too quickly. Maybe a dime would be tougher?
 

GrouchoDuke

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Since there can occasionally be an early burn-through of the ejection grain, I pot the charge well with epoxy. Oh yes, and I put in a penny. It's kind of difficult to blow that out.
Is the penny really needed? I've only used their smaller motors, but epoxy alone has worked well so far for me. Ya know...cuz pennies are expensive. :wink:
 

JimJarvis50

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Is the penny really needed? I've only used their smaller motors, but epoxy alone has worked well so far for me. Ya know...cuz pennies are expensive. :wink:

I suspect that epoxy alone would be fine. But pennies just fit so nice. This has to be the literal definition of cheap insurance.

But seriously, don't forget to glue in the forward closures in CTI 54mm motors. Use a nice red epoxy fillet, per the pic. More likely to save you a rocket than the penny.

Jim

Fillet.png
 

BDB

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I suspect that epoxy alone would be fine. But pennies just fit so nice. This has to be the literal definition of cheap insurance.

But seriously, don't forget to glue in the forward closures in CTI 54mm motors. Use a nice red epoxy fillet, per the pic. More likely to save you a rocket than the penny.

Jim

Jim, What's the issue with CTI 54 mm motors? Do you do this for all 54 mm CTI motors or just for the ones that you remove the ejection charge from?
 

Nytrunner

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Jim, What's the issue with CTI 54 mm motors? Do you do this for all 54 mm CTI motors or just for the ones that you remove the ejection charge from?

There's been some burnthrough around the top end of the liner reported on Pro54's.

(unrelatedly, an SLI team just lost a booster to an L2200 burnthrough under the forward closure Saturday. 2nd year in a row they've had that trouble)
 

JimJarvis50

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Jim, What's the issue with CTI 54 mm motors? Do you do this for all 54 mm CTI motors or just for the ones that you remove the ejection charge from?

Yes, gas gets past the forward closure and either causes a bulge in the tube at that point, or a burnthrough. I've seen this happen maybe 8 times? I haven't seen it in a while now, possibly because most people in the club know to glue the closure on, and our local motor vendor gives folks a heads-up when they buy a motor.

I glue all of my Pro54 motors.

Jim

DSCF0868.jpg
 

Dad Man Walking

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...Use a nice red epoxy fillet, per the pic...

Jim, this is the first time i've heard of this. Are you using a special epoxy ("red"?) that I've not heard of, or are you just highlighting the fillet in your diagram?

It looks like the epoxy is bonding the grain, the liner and the forward closure. Seems like that would burn up pretty fast. is there any data on how much more pressure the closure can hold with this technique?
 

JimJarvis50

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Jim, this is the first time i've heard of this. Are you using a special epoxy ("red"?) that I've not heard of, or are you just highlighting the fillet in your diagram?

It looks like the epoxy is bonding the grain, the liner and the forward closure. Seems like that would burn up pretty fast. is there any data on how much more pressure the closure can hold with this technique?

Just regular epoxy. Red referred to the diagram. The idea is to buy just a little extra time before the closure fails. I have no idea how to quantify the effectiveness, except that I'm not aware of any failures for motors prepared this way. I was discussing this issue and this fix with CTI around the time of the accident. They acknowledged an issue, but there was no way to resolve it. Best I can do is try to periodically give folks a heads up.

Jim
 

wighty44

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Jim,
Would you please describe how best to create this internal Pro54 closure fillet? Do you apply a bead of epoxy to the aft edge of the delay, insert into the closure, and then stand it up to allow the epoxy to adhere to the case insulator? Do you lightly abrade the insulator , and/or the delay end for improved epoxy adherence?

Thanks...
 

JimJarvis50

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Jim,
Would you please describe how best to create this internal Pro54 closure fillet? Do you apply a bead of epoxy to the aft edge of the delay, insert into the closure, and then stand it up to allow the epoxy to adhere to the case insulator? Do you lightly abrade the insulator , and/or the delay end for improved epoxy adherence?

Thanks...

Sure. I lightly sand the end of the liner and the matching surfaces of the closure. Then, I clean those surfaces with a little alcohol. If there's an o-ring, I just leave it on. I apply a little epoxy to the closure and then a little heavier layer on the inside edge of the liner. This will become the fillet when the closure is inserted. If necessary, I arrange for the pieces to be held tightly together while the epoxy sets up. I try not to forget to set the delay time, since this can't be adjusted after the closure is glued in.

Jim
 

wighty44

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Thank you! BTW, do you wait for the epoxy to cure before inserting the propellant grains, or do you insert them (as would be done when normally building the motor) while the epoxy is still curing?
 

JimJarvis50

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Thank you! BTW, do you wait for the epoxy to cure before inserting the propellant grains, or do you insert them (as would be done when normally building the motor) while the epoxy is still curing?

It seems to me like the lower closure it typically already glued in. I don't know if that is always the case, but it has been on all of the motors I have recently assembled. Therefore, the grains have to be installed at the point where you glue in the forward closure. I'm not sure it matters if the glue is in contact with the grains or not.

Jim
 

wighty44

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It seems to me like the lower closure it typically already glued in. I don't know if that is always the case, but it has been on all of the motors I have recently assembled. Therefore, the grains have to be installed at the point where you glue in the forward closure. I'm not sure it matters if the glue is in contact with the grains or not.

Jim
Ok. As I recall, the 3 Pro54s I've used (K2045, K650, & I150) were not glued-in. Perhaps that is not the case for larger Pro54s. Nonetheless, it's nice to get your input and experience on this - Thank you.
 
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OverTheTop

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For bonus safety points you can use a sharp piece of wood (skewer?) to remove the sticker over the top of the BP. Best to use only non-sparking tools around BP. Don't forget safety glasses either way.
 
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