MPR/HPR reloadable motor BP ejection charge masses?

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Winston

Lorenzo von Matterhorn
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Figures found so far:

Pro24 ejection charge - 0.6 gram of FFFFg (official)
Pro29 ejection charge - 1.2 grams of FFFFg (official)
Pro38 ejection charge - 1.3 grams of FFFFg (official)
Pro54 ejection charge - 2.0 grams FFFFg (official)

Aerotech 29mm ejection charge - 1.4 grams (unofficial, measured by user)
Aerotech 29/40-120 ejection charge - 0.7 grams (unofficial, measured by user)
Aerotech 24/40 ejection charge - 0.2 grams (unofficial, measured by user)

Official Aerotech figures received via email:

24-29mm single use - 0.7 grams (official)
29-38mm reloads - 1.4 grams (official)
54mm reloads - 2.1 grams (official)

Any to add or to correct?

Charge masses provided to plug into this:

Ted Apke's On-line Ejection Charge and Shear Pin Calculator

https://www.info-central.org/?article=303
 
Last edited:
Thanks - I was just wondering about this very thing.


Sent from my iPhone using Rocketry Forum
 
The instructions that come with CTI ProX motors list the BP charge and are identical to your posted figures.
 
All CTI charges are correct as per CTI's published data on the sizes mentioned.


Later!

--Coop
 
A similar, but different question.. Does anyone know the mass of the BP provided with the AT J425R DMS?? I'll end up weighing it out, but doesn't hurt to ask here...
 
Aerotech 29mm ejection charge - 1.4 grams (unofficial, found in forum post)

29/40-120 is 0.7 g (the subject line does say MPR..)
24/40 is .5 g

BTW, while I love the Calculators, I disagree with the accompanying statements that smaller rockets need higher and higher pressures.
 
A similar, but different question.. Does anyone know the mass of the BP provided with the AT J425R DMS?? I'll end up weighing it out, but doesn't hurt to ask here...

If I recall correctly, 2 grams (full cylindrical centrifuge tube) came with the J270 I flew last summer. I don't know if they would change that.
 
I flew a AT D15T (24/40) this morning. The ejection charge seemed really weak for .5g. I went home and measured out a .6g charge and flew the same rocket again. I should have weighed a stock charge before I made that second flight. The ejection charge was so strong that it tore out the bottom of the nose cone and blew out the side of the upper body tube.

I got home and measured the last charge I had from that package and it was only .2g. :facepalm:

29/40-120 is 0.7 g (the subject line does say MPR..)
24/40 is .5 g

BTW, while I love the Calculators, I disagree with the accompanying statements that smaller rockets need higher and higher pressures.
 
I measured the ejection charges on three different AT 24/40 motors today(D15T, E18W, F24W). All three contained .2g.
 
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