motor eject powder levels

Anyone have a table of powder used for common reloads, or a rule of thumb? I understand 1.4g is common though I imagine bigger and smaller motors differ.

AT
.75 for Hobbyline [all]
1.75 for 29 & 38
None with 54 & larger

CTI
0.6 for 24mm
1.2 for 29
1.3 for 38
2.0 for 54 that are not plugged

Edit:
I just looked it up on CTI website.

Nice! Thanks much as usual.

CTI has amounts for each size on their website.

FYI, I flew Pro38s for years with no altimeter.
I would cut short sections of BT-20 (1/2"), they fit perfectly in the end of the delay/ejection module.
Peel off the seal disc and dump the BP into a cup.
Glue the tube piece to the module with 5 min epoxy in the field.
Fill it with the desired amount of additional BP needed, fill up to the top with some wadding.
Wrap masking tape around the tube, several wraps and fold it over to seal. More is better.
I had an old wRasp app that ran on a vintage Palm Pilot.
I would plug in the numbers, figure out the delay I would need.
I used this method to throw out laundry out of tubes up to 5.5"

OBTW, I still use this method with Pro38s when I when even use dual altimeters.
Pull out the PalmPilot, add 2 seconds to the delay time needed so as not to fire too early.
3rd backup for "just in case"
I like throwing out the laundry, not hoarding it!...LOL

Oh, was it hidden in the instructions PDFs? I definitely checked the motor page and specifications, sorry I missed them.

blackjack2564 said:

AT
.75 for Hobbyline [all]
1.75 for 29 & 38
None with 54 & larger

CTI
0.6 for 24mm
1.2 for 29
1.3 for 38
2.0 for 54 that are not plugged

Edit:
I just looked it up on CTI website.

Click to expand...

Agree with the CTI figures, but I got these figures from Aerotech in an email late last year:

Aerotech figures received via email:

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

https://www.rocketryforum.com/showt...able-motor-BP-ejection-charge-masses&p=739175

If you look on the AT motor assembly drawings for RMS and Hobbyline;
18/20 - 0.4g
24/40 - 0.5g
29/40-120 - 0.7g
29 - 54 mm HPR drawings just says FILLS WELL 3/4 FULL, or USER SUPPLIED.
Of course the 75mm and larger are all plugged.

Handeman said:

If you look on the AT motor assembly drawings for RMS and Hobbyline;
18/20 - 0.4g
24/40 - 0.5g
29/40-120 - 0.7g
29 - 54 mm HPR drawings just says FILLS WELL 3/4 FULL, or USER SUPPLIED.
Of course the 75mm and larger are all plugged.

Click to expand...

How about an Aerotech Mirage. With the hobbyline 40/120 and a G64 with the supplied .75g- Should I use the same amount for an H135dms in the same rocket if that .75g has been performing well and using stock separation point. ? Thought I might go 1g but I don't want to blow it up either.

If the 0.75g has worked well, I would stick with it. The H135dms is a larger motor than the Hobbyline so it should reduce your volume a little. Using the same 0.75g with that motor should up the ejection pressure slightly, although probably not enough to really notice.

Why are you considering going to 1g? Did you watch the ejection on 0.75g and it looked a little weak? If you didn't have any issues, I would stick with the 0.75g, although upping it probably wouldn't hurt anything, it could.

The amount bp supplied with the Aerotech G reloades has always worked well. I will be using an Aerotech H135-14W DMS next . Im not familiar with the motor but I understand I will use a delay tool for the delay adjustment and fill the ejection charge from the supplied 1.5g(I think)of bp. If I put .75g of bp in a well that can hold 1.5g- will the charge light even if its not in contact with the delay(if the rocket is pointed down at ejection)? does the plug go down to limit space in the well? BP is pretty flammable, maybe it would light regardless from the burning delay in such close quarters. Its something that's been on my mind that I would like to resolve before launch day

crazyed said:

The amount bp supplied with the Aerotech G reloades has always worked well. I will be using an Aerotech H135-14W DMS next . Im not familiar with the motor but I understand I will use a delay tool for the delay adjustment and fill the ejection charge from the supplied 1.5g(I think)of bp. If I put .75g of bp in a well that can hold 1.5g- will the charge light even if its not in contact with the delay(if the rocket is pointed down at ejection)? does the plug go down to limit space in the well? BP is pretty flammable, maybe it would light regardless from the burning delay in such close quarters. Its something that's been on my mind that I would like to resolve before launch day

Click to expand...

Put the powder into the well just like normal after drilling the delay and pack dog barf onto top tightly. Secure top with masking tape or whatever your preference is (Redcap is the factory method). Even just putting the BP into the charge well will work just fine as long as the charge well is capped of course. I just like making sure my BP is slightly compacted and unable to move around inside the charge well.

+ What Rharshberger said. A little dog barf to take up the unused space in the powder well doesn't hurt.

I'm not sure you will get good ignition if there is no powder against the delay grain when it burns through. I say that because I had a HobbyLine that didn't fire until the instant it hit the ground. The same motor and delay had worked perfectly in the same rocket the day before, but this time I think a hot/burning piece of the delay grain went through the well hole on impact and set off the delay that hadn't fired when the delay first burned through. I've made it a point to get powder down into the well hole and on the top of the delay grain ever since and I've never had the problem again. It seems that all it takes is a few BP grains on the delay grain and they will set off the rest of the charge even if the rocket is upside down after apogee.

With that said, a little dog barf to take up the extra space and keep the powder against the delay grain seems like a very prudent step to me. I've also seen people use the Estes wadding, plain tissues or paper towels and even grass or weeds picked off the ground. I know one guy that regularly uses green grass and weeds as wadding in his motor eject rockets. He claims it's even more biodegradable then dog barf and works just as well. I can't say as I'm able to argue with him since it's always worked on the flights I've seen.

I have only flown one DMS engine but its design is pretty flexible. The well the bp goes into is deep and plastic cap in included. Unlike other designs it is inserted upside down into the well and will hold the powder in place. The well is capable of handling more bp if it is needed. A little bit of dog barf might be needed if the cap does not contact the bp that was poured in (it can be pressed pretty far in so I do not think it will be an issue). The universal drilling tool is the easiest way to set the delay.