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I received clarification from Charlie. If the rocket is one that will be subjected to high acceleration, glue bonding the grains makes sense. For rockets with a lower acceleration gluing the grains is not necessary. I'll talk to the rest of the board to see what, if anything, needs to be added to Paul's announcement.


Steve Shannon

My question would be what counts as "high acceleration"? >20G? >60G? The famous (in my area at least) Nike Smoke K2045 drag race seems to be around 50G's, with the K2045 hard-to-get it was recommended to use the K2050ST instead, and the loads showed the day the race was supposed to happen (though the race was changed last-minute due to the fact that these motors turned out to be plugged when it was advertised they'd be -14A's). And are there instructions on how to do the bonding? I haven't flown anything that required bonding before, though I have a K2050ST waiting to go in my Nike Smoke.
 
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My question would be what counts as "high acceleration"? >20G? >60G? The famous (in my area at least) Nike Smoke K2045 drag race seems to be around 50G's, with the K2045 hard-to-get it was recommended to use the K2050ST instead, and the loads showed the day the race was supposed to happen (though the race was changed last-minute due to the fact that these motors turned out to be plugged when it was advertised they'd be -14A's). And are there instructions on how to do the bonding? I haven't flown anything that required bonding before, though I have a K2050ST waiting to go in my Nike Smoke.

Aerotech has a nice grain bonding PDF at the very top of their instructions page. I bonded my first bonding-necessary motor, an M650, last September and it was terrifying, but it didn't need to be; I was just nervous. It was easier than I thought and flew great.

Personally, I would consider the entire range you listed as high acceleration, but there are much more aggressive flyers than me.


Steve Shannon
 
Aerotech has a nice grain bonding PDF at the very top of their instructions page. I bonded my first bonding-necessary motor, an M650, last September and it was terrifying, but it didn't need to be; I was just nervous. It was easier than I thought and flew great.

Personally, I would consider the entire range you listed as high acceleration, but there are much more aggressive flyers than me.


Steve Shannon

Here's a link to the instructions:
https://www.aerotech-rocketry.com/u...201d9280_Grain Bonding Instructions Small.pdf



Steve Shannon
 
Aerotech has a nice grain bonding PDF at the very top of their instructions page. I bonded my first bonding-necessary motor, an M650, last September and it was terrifying, but it didn't need to be; I was just nervous. It was easier than I thought and flew great.

Personally, I would consider the entire range you listed as high acceleration, but there are much more aggressive flyers than me.

Yeah, it's an extremely subjective term, so it seems like a bad phrase to throw around, it has no meaning. :) I guess the other question would be what flight with a K2050ST isn't high-acceleration? Seems like any motor that only burns for ~0.7s is probably going to be "high-acceleration", or else fail to get the rocket safely off the pad. :)

And those instructions expect there to be spacer o-rings, which I think someone else already noted aren't supplied with this motor. So where is one supposed to get those? Really seems like AT didn't think this one through.
 
And those instructions expect there to be spacer o-rings, which I think someone else already noted aren't supplied with this motor. So where is one supposed to get those? Really seems like AT didn't think this one through.

That is where I am at a loss as well... Charlie, please chime in here set this straight... :)
 
Yeah, it's an extremely subjective term, so it seems like a bad phrase to throw around, it has no meaning. :) I guess the other question would be what flight with a K2050ST isn't high-acceleration? Seems like any motor that only burns for ~0.7s is probably going to be "high-acceleration", or else fail to get the rocket safely off the pad. :)

And those instructions expect there to be spacer o-rings, which I think someone else already noted aren't supplied with this motor. So where is one supposed to get those? Really seems like AT didn't think this one through.

This is a case of Aerotech being damned for offering helpful information. Charlie specifically said that people flying the K2050 in minimum diameter rockets might want to consider bonding the grains. I'm the person who translated that to mean high acceleration flights.

I would think that anyone who intends to fly a minimum diameter rocket on a motor with an average thrust of 460 lbs. would have enough experience to make some of these decisions. If you want specific thresholds separating low, medium, and high acceleration, you're expecting too much.

Other posts have pointed out the the size of the o-rings is not crucial. They're just there as grain spacers while gluing the grains into the liner to prevent the grains from moving under high acceleration, so a trip to the nearest hardware store and a Mark 1 eyeball should be considered.


Steve Shannon
 
Other posts have pointed out the the size of the o-rings is not crucial. They're just there as grain spacers while gluing the grains into the liner to prevent the grains from moving under high acceleration, so a trip to the nearest hardware store and a Mark 1 eyeball should be considered.

Steve Shannon

However, this begs the question: Is there enough room to add the spacer o-rings? If too much space is taken up in the liner, one runs the risk of not being able to get the forward seal disc in. I assume a dry fit or two might be in order...
 
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The dry-fit is step 2 in the bonding instructions. :) It may not clearly state to dry-fit with the spacers, so if you don't realize until later on that spacers are even required you might miss that in the dry-fit step and realize you're screwed only after the glue is in place. But it certainly seems like the size of the spacers should be very important, not a "don't-care". Would be much better if AT just provided the necessary parts, they do with every other motor, don't they? Or do customers usually have to source their own spacers?
 
However, this begs the question: Is there enough room to add the spacer o-rings? If too much space is taken up in the liner, one runs the risk of not being able to get the forward seal disc in. I assume a dry fit or two might be in order...
I think that shows excellent sense! I would buy the smallest thickness O-rings that fit into the liner without bunching up. RCS Rocket Motor Parts Company (Aerotech's parent company I believe) sells O-rings separately. I tried to see what size of O-rings were packaged with the 75 and 98 mm reloads which require O-rings, but failed.

And I want to point out that at no time did Charlie say that glue bonding the grains was required, so feel free to fly without gluing the grains.
 
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As long as we are putting in requests, I would love a non-hazmat reload for the 38 480 case (which is suspect is the practical size limit for the smaller grain size required).

Thanks for the reminder Terry! I forgot to mention we will be further developing the US mailable line of HP motors to include the 38/480 up to the 38/1080 which would produce a US mailable J motor. Look for this around the middle of the year.
 
The dry-fit is step 2 in the bonding instructions. :) It may not clearly state to dry-fit with the spacers, so if you don't realize until later on that spacers are even required you might miss that in the dry-fit step and realize you're screwed only after the glue is in place. But it certainly seems like the size of the spacers should be very important, not a "don't-care". Would be much better if AT just provided the necessary parts, they do with every other motor, don't they? Or do customers usually have to source their own spacers?

When spacers are required they are included.
The reason the size of the o-rings is not crucial is because they're only there to keep the grain ends from touching when they are glued into the liner. They don't seal anything. If the grain ends end up touching that could inhibit them from burning, thus changing the thrust curve of the motor. Almost any gap is enough.
 
Good morning Charlie,

I recently took delivery of (2) K-2050's. Based on posts in this thread, the grains need to be bonded to the liner. Question is, does the K-2050 get bonded to the liner WITHOUT grain spacer o-rings? Both of the K-2050's did not include said O-rings, so I wanted to make sure long before I glue one of these rascals together. If they DO require grain spacer o-rings, what is the dash number please?

Thank you sir,

View attachment 309152

Justin,

Good question that I have been asked recently by a few others. The K2050ST does not require bonding or grain spacing o-rings. I think the TMT announcement may have used the 98mm Super Thunder announcements as a template and just forgot to remove the last sentence. That being said, bonding will not hurt and you will get the max performance from the motor this way. Hope this clarifies things a bit.
 
Yeah, it's an extremely subjective term, so it seems like a bad phrase to throw around, it has no meaning. :) I guess the other question would be what flight with a K2050ST isn't high-acceleration? Seems like any motor that only burns for ~0.7s is probably going to be "high-acceleration", or else fail to get the rocket safely off the pad. :)

And those instructions expect there to be spacer o-rings, which I think someone else already noted aren't supplied with this motor. So where is one supposed to get those? Really seems like AT didn't think this one through.

I see what you are saying, however the K2050ST is just a different motor that does not use spacer o-rings. I have been told "there isn't enough burn time for spacing the o-rings to matter" :wink:

The new AT RMS instructions are now "generic" and have been updated to include the spacer o-rings which most of them do take, but the K2050ST is the exception here.
 
I think that shows excellent sense! I would buy the smallest thickness O-rings that fit into the liner without bunching up. RCS Rocket Motor Parts Company (Aerotech's parent company I believe) sells O-rings separately. I tried to see what size of O-rings were packaged with the 75 and 98 mm reloads which require O-rings, but failed.

And I want to point out that at no time did Charlie say that glue bonding the grains was required, so feel free to fly without gluing the grains.



I believe that in any dia motor the grain spacer o-rings are 1/16" thick. The correct grain spacer o-rings for the 54mm. motors are 1/16"x 1-7/8" dia., same rings as the forward seal disk takes.
 
I'd like to give a shout out for AT customer service. I acquired a M2400BT motor but the nozzle seemed to be off, the throat was very small for a 3 grain M motor. Sent an email and got immediate response from Karl. He pointed me in the right direction on what nozzle I needed to purchase and in the end he even bored it out to the correct throat size for me.

Awesome customer service, Thanks AT!
 
I'd like to give a shout out for AT customer service. I acquired a M2400BT motor but the nozzle seemed to be off, the throat was very small for a 3 grain M motor. Sent an email and got immediate response from Karl. He pointed me in the right direction on what nozzle I needed to purchase and in the end he even bored it out to the correct throat size for me.

Awesome customer service, Thanks AT!

They made you buy a new nozzle ?
 
They made you buy a new nozzle ?

This was from a motor that I obtained from someone going out of the hobby. It was out of the package, mixed with parts and pieces from many different motors. Me not having the correct nozzle was not the fault or error of Aerotech. Karl with AT asked a few question to enure the grain geometry was correct for the M2400T and then told me which nozzle I needed and what the throat should be. I sent him a couple pictures of the grains and from the dates hand written on the them he figured these could have been some of the first Blue Thunder 98mm grains cast.

Thanks again AT, keep up the good work!
 
This was from a motor that I obtained from someone going out of the hobby. It was out of the package, mixed with parts and pieces from many different motors. Me not having the correct nozzle was not the fault or error of Aerotech. Karl with AT asked a few question to enure the grain geometry was correct for the M2400T and then told me which nozzle I needed and what the throat should be. I sent him a couple pictures of the grains and from the dates hand written on the them he figured these could have been some of the first Blue Thunder 98mm grains cast.

Thanks again AT, keep up the good work!

Well that makes a world of difference . I thought ( and I guess miss understood ) that you purchased a new load and it had the wrong nozzle. My apologizes to you and aerotech .

Eric
 
I flew an old AT 24mm G46W today. All I can say is, PLEASE MAKE THESE AVAILABLE AGAIN. Please, pretty please. If not this exact one then some other 24 mm single use Gs.
 
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