Cesaroni Case Question

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spence

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I am helping out a COllege team with their project , but only have experience with Aerotech Motors. Can you help out an answer the following inquiry that I got


"For Cesaroni cases, is it normal to epoxy the casing in? In the last rocket we glued threads onto a phenolic tube and then threaded on the casing. We are just confused and want to make sure."


Thanks in advance

Steve

 
I am helping out a COllege team with their project , but only have experience with Aerotech Motors. Can you help out an answer the following inquiry that I got


"For Cesaroni cases, is it normal to epoxy the casing in? In the last rocket we glued threads onto a phenolic tube and then threaded on the casing. We are just confused and want to make sure."


Thanks in advance

Steve


I am familiar with Cesaroni and Aerotech reloads up to 75mm, and your statement is rather confusing.

"Epoxy the casing in": The only thing I'm aware of epoxying are propellant Grains within a Liner for high performance reloads, and occasionally the 54mm plastic foreword closure onto the Liner.

"We glued threads onto a phenolic tube, then threaded on the casing": Please give some more detail about this.
 
What size diameter? 24mm thru 54mm come preassembled. You just adjust the delay, grease the liner, slide it in, and tighten the closure. Done.

75mm and up need to be built like AT and Loki motors. Some specific loads need the grains glued, but most don't.

Please get more details of what they are really asking.
 
Maybe they are talking about a threaded forward motor retainer, where you use a threaded forward closure allowing you to "thread" the motor into the motor mount? They may be referring to epoxying in that forward retainer with the all thread in it?

If so, then yes, you can get threaded forward closures for CTI motors if you are flying them plugged with flight computers for deployment events. But like others have said, there is no epoxy involved in assembling the actual motor unless you are gluing grains on a 75mm+.
 
AeroTech LMS motors have you epoxy in the forward threaded closure into a phenolic case. The question could be something along those lines.

Correct answer to all motor assembly questions is to read and understand the instructions. If there is confusion on the instructions, contact the manufacturer for further details.
 
Guys-

Here is some more information that should help clarify - Thanks in advance


"Our previous rocket we had threads as seen in the attached photos. The threads were attached to a phenolic We were then able to thread on the 38mm casing. When we look online at the Cesaroni casing (pasted below) we see no such threading.


Our basic question is how are we supposed to secure the Pro 98 casing into the rocket?

0



Also, how far should the motor mount tube extend below the lower centering ring?

We were given a phenolic tube with the rocket kit for the motor with roughly the same dimensions as the Pro 98 motor casing, also seen in attachment.



Any information to clarify would be helpful.

IMG_20180509_130114964.jpgIMG_20180509_130153458_HDR.jpgIMG_20180509_130203545.jpg
 
Guys-

Here is some more information that should help clarify - Thanks in advance


"Our previous rocket we had threads as seen in the attached photos. The threads were attached to a phenolic We were then able to thread on the 38mm casing. When we look online at the Cesaroni casing (pasted below) we see no such threading.


Our basic question is how are we supposed to secure the Pro 98 casing into the rocket?

0



Also, how far should the motor mount tube extend below the lower centering ring?

We were given a phenolic tube with the rocket kit for the motor with roughly the same dimensions as the Pro 98 motor casing, also seen in attachment.



Any information to clarify would be helpful.

If you want a specific answer to your situation you should provide the specific reload you are looking at. Not all same diameter reloads are prepped the same way. Specific to CTI 98mm here is a link to some additional info that may help to clear things up. https://www.pro38.com/pdfs/Pro98_notes_V1.6.pdf
 
It looks like they are asking how to build the rocket - not so much anything about the motor. Judging by "Our basic question is how are we supposed to secure the Pro 98 casing into the rocket? Also, how far should the motor mount tube extend below the lower centering ring?"

Concerns me these questions are being asked by someone with a Pro 98 case.
 
I think I understand now. You epoxied part of a threaded retainer onto the Motor Mount Tube.
Aeropack is a reputable commercially available retainer. You can alo serach for "kaplow clips" or "madcow style retainers" for alternative methods.

Please understand that the Motor Mount Tube (phenolic in your case) which transmits the motor thrust to the airframe, is very different from a Motor Case which contains the propellant grains (Metal for reloads, fiberglass for Disposable Motor Systems [DMS])
 
Steve,

Most if not all the members of this forum are members of TRA, NAR or CAR. If at all possible you should consider launching with a club and they can assist you in learning how to build and launch rockets. We have a set of rules and methods that ensures safety for all those concerned. Keep in mind that we also ensure that local and federal laws are followed.
 
Learn something new everyday. I've never even seen that method of retention. This is one of those questions that can be answered in 10 seconds in person, or by taking 20 minutes to craft a written response.

I agree. Stop by a club launch and there will be ample people who will want to show you how CTI retention works.
 
Guys-

Here is some more information that should help clarify - Thanks in advance


"Our previous rocket we had threads as seen in the attached photos. The threads were attached to a phenolic We were then able to thread on the 38mm casing. When we look online at the Cesaroni casing (pasted below) we see no such threading.


Our basic question is how are we supposed to secure the Pro 98 casing into the rocket?

0



Also, how far should the motor mount tube extend below the lower centering ring?

We were given a phenolic tube with the rocket kit for the motor with roughly the same dimensions as the Pro 98 motor casing, also seen in attachment.



Any information to clarify would be helpful.

View attachment 344297View attachment 344298View attachment 344299

That looks like an Aeropack retainer with an adapter. I can't tell the size from the pic, but that looks like a 54mm mmt/retainer with a 54-38 adapter.

I'm really guessing here because the questions are so odd and don't match the pics. But if they're asking if a CTI 98mm motor will work with an Aeropack retainer, it will. The CTI 98mm casing has a thrust ring that fits in the retainer. See https://aeropack.net/retainerdimensions.asp for dimensional info. The 98mm retainer isn't epoxied on to the motor mount tube. It's only available as a flanged retainer. The MMT is installed so the aft end is flush with the aft centering ring. The flange is attached to the centering ring with 12 screws.

I'm also a bit concerned these questions are coming from someone with a 98mm casing. Is there a mentor for this group?
 
Anyone else out there wondering what kind of guidance these students are getting?
 
The OP stated he was familiar with Aerotech motors, not Cesaroni.

It might have been an easy answer if the students hadn't submitted such confusing questions. Let's not jump to conclusions
 
What type of AT familiarity would lead someone to ask about how far the motor tube should extend past the bottom centering ring?

I'm cool with the here's a bag of parts, go make a rocket approach of teaching so long as the bag doesn't contain 98mm hardware. That approaches scary. Conclusions or not, still scary.
 
What type of AT familiarity would lead someone to ask about how far the motor tube should extend past the bottom centering ring?

I'm cool with the here's a bag of parts, go make a rocket approach of teaching so long as the bag doesn't contain 98mm hardware. That approaches scary. Conclusions or not, still scary.

I agree with you, Grouch. I’m all for students learning Rocketry, but those who entice them into this position need to insist on mentors with appropriate experience and knowledge. Most of us get that experience by rising through the ranks. To drop a 98 mm motor system onto a group of students who don’t know what to ask is flirting with danger.
I greatly appreciate their mentor bringing this question and I would not want our criticisms to extend to him. He’s trying to do the best he can.
Is there anyone experienced in high power motors nearby who can help?
 
Wise words Steve. As a hobby community, maybe we could do more to help the schools start out on the right track.

My personal biases come through all too often. I was at a launch where an engineering student who stated he has flown his rocket several times was asking me for help with chute packing, shock cords and how tight the nose cone should be. I started to get a little worried when he came back from the vendor table with a CTI 38mm reload and was trying to figure how to get it into the rocket. I gently suggested he needed a motor case for the reload and he said he never used one in the past and didn't want to buy anything else, just wanted to hurry up and get his cert flight in and leave. I explained that there would be no way he was going to cert if he stuck with his plans of putting the case less reload into the motor tube. I offered to loan him one of mine. He said he would figure it out on his own the left shortly after. I was befuddled, he not only did he not read the directions, he didn't listen or take the free advice and a borrowed case. What can you do?
 
Wise words Steve. As a hobby community, maybe we could do more to help the schools start out on the right track.

My personal biases come through all too often. I was at a launch where an engineering student who stated he has flown his rocket several times was asking me for help with chute packing, shock cords and how tight the nose cone should be. I started to get a little worried when he came back from the vendor table with a CTI 38mm reload and was trying to figure how to get it into the rocket. I gently suggested he needed a motor case for the reload and he said he never used one in the past and didn't want to buy anything else, just wanted to hurry up and get his cert flight in and leave. I explained that there would be no way he was going to cert if he stuck with his plans of putting the case less reload into the motor tube. I offered to loan him one of mine. He said he would figure it out on his own the left shortly after. I was befuddled, he not only did he not read the directions, he didn't listen or take the free advice and a borrowed case. What can you do?

I agree; what can we do.
 
Anyone else out there wondering what kind of guidance these students are getting?
Some colleges prefer for engineering students and professors to figure it out, by not providing a mentor. Anything L-1 multi to L-3 and expendable payloads. Having been in that boat I can tell you it sucks, nothing prepares you. You end up learning more about HPR while at the launch site. TRF became invaluable for my team. That Raven 3 highly recommended here, probably saved us from our own stupidity and lack of experience. Add a whole bunch of academia busy work and they don't have much time to go ask mentors or drive across states for mentors to help. If they are lucky to live near one then take advantage of the mentor's practical knowledge it will save much frustration.
 
Some colleges prefer for engineering students and professors to figure it out, by not providing a mentor. Anything L-1 multi to L-3 and expendable payloads. Having been in that boat I can tell you it sucks, nothing prepares you. You end up learning more about HPR while at the launch site. TRF became invaluable for my team. That Raven 3 highly recommended here, probably saved us from our own stupidity and lack of experience. Add a whole bunch of academia busy work and they don't have much time to go ask mentors or drive across states for mentors to help. If they are lucky to live near one then take advantage of the mentor's practical knowledge it will save much frustration.

That's a pretty stupid and dangerous approach, these colleges should be held to the same requirements that everyone else is in NAR, TRA, or CAR.
If no one on the team holds the appropriate certification, or they do not have an active mentor with the appropriate certification, then they can't acquire anything but a but a hobby level motor, case closed.

I mentored a team in the NASA SL and NASA requires a mentor with the appropriate certification to be part of the team and handle the motor, starters, and pyro charges, and help guide the team through the entire process of a high power design, build, and flight. NASA SL also requires extensive submittals before, during, and after construction, including simulations, plus a very rigorous pre-flight RSO inspection the day before the flight, along with all the same above requirements applied to an actual sub-scale model build and flight for real world proof of concept. Allowing someone to acquire a 98mm power plant that doesn't know how to install a motor retainer is not a good policy and will probably end up in a bad way.
 
Some colleges prefer for engineering students and professors to figure it out, by not providing a mentor.

...because this is how the real world works. Nobody is going to hold your hand. You need to learn how to learn - and to have the wherewithal to know when you need to seek a second opinion, read the manual, do more research, or find somebody who knows what they’re doing.

This does not mean “not following the rules is ok”... It means you need to seek out out the knowledge and people you need to succeed at your task - or you’ve fundamentally failed at one of the basic tenants of good engineering. One hopes, like the real world, that there are checks and balances before any of the dangerous things are lit on fire.
 
"That's not how the real world works..."

Not in my job.

Yes, we are expected to know how to learn, but schooling and mentoring are important part of learning the job. Students and rookies are expected to study and ask lots of questions while preceptor are expected to guide them and allow them to learn from those with more experience. Our responsibility and risks are high, mistakes can be fatal .
 
...because this is how the real world works. Nobody is going to hold your hand. You need to learn how to learn - and to have the wherewithal to know when you need to seek a second opinion, read the manual, do more research, or find somebody who knows what they’re doing.

This does not mean “not following the rules is ok”... It means you need to seek out out the knowledge and people you need to succeed at your task - or you’ve fundamentally failed at one of the basic tenants of good engineering. One hopes, like the real world, that there are checks and balances before any of the dangerous things are lit on fire.

I agree with this. I mean, this is how literally anyone starts doing anything. And that is what OP is doing here. If they glue an aft closure into a MMT with no motor retainer, an FSO should catch it. That's the process control here. Them asking what an Aeropack retainer is isn't inherently dangerous. Discouraging them from asking is dangerous.

OP, it looks like the first rocket they had came with an Aeropack in the kit. You just need to go buy one. A lot of kits don't come with a retainer so the builder can decide on retention method.
 
Guys - I Thought this was a rather innocent request - . When I started as a BAR and knew not much, I soaked in advice from fellow rocketeers at launches and on this forum.

I went up the learning curve ten times faster that way. I understand what many of you are saying about students, etc. I will keep future questions to my own fleet. I'm not making any judgments one way or another here, just acknowledging all the opinions and respect the different view points on this.
 
spence,

Please seek some in-peson assistance. There are skads of people with the required experience in the tri-states area that can help. Some might even do so with a smile on their face. Hopefully you can see the concern regarding a 98mm case in the hands of people lacking the basic skills to assemble a rocket. Nobody here wants to see your team fail and certainly nobody here wants to see the get hurt but that's a lot of power. Basic knowledge pulled from the High Power book or even assembly instructions to similar kits might be helpful. Things such as motor retainers are not part of the motor and are independent of CTI and AT or other manufacturers. A quick visit to a local launch (METRA comes to mind as they are a great bunch of guys) will put your team light years ahead of the curve. Heck, you might even have fun in the process. Just for reference, I have been flying for a long while and feel confident with my knowledge and skills and I wouldn't build a rocket powered by 98mm's without help and guidance from people who regularly fly them. My little J's while a L2 motor have not prepared me for the flight and recovery challenges of something in the 98mm range. Simple fact. Oh and sorry to get safety on you, at the level you are asking about...no question is innocent unless you are inquiring about the color to paint the thing.
 
I am helping out a COllege team with their project , but only have experience with Aerotech Motors. Can you help out an answer the following inquiry that I got


"For Cesaroni cases, is it normal to epoxy the casing in? In the last rocket we glued threads onto a phenolic tube and then threaded on the casing. We are just confused and want to make sure."


Thanks in advance

Steve


Steve,
I apologize if my answer seemed to be critical of you or these students. The question they asked, about gluing in a casing didn’t make sense to me and nomenclature is important.
I hope you never stop asking questions, whether they’re about student projects or your own.
A better answer from me might have been as follows:
The casing is not typically glued into the motor mount tube. What is depicted is an aero pack retainer male threaded portion which is epoxied to the motor mount tube when the rocket vehicle is built.
The CTI motor reload is assembled according to the accompanying instructions into a CTI motor case. That’s actually easier on the larger motors than on the small motors.
Then, the assembled motor is slid into the motor mount tube until the thrust ring on the case slides into the male retainer which was previously epoxied to the motor mount tube (MMT). Then the female half of the retainer (cap) is screwed to the male half, capturing the thrust ring and preventing the motor from sliding out.
At no point in this process is it advisable to epoxy the casing into the MMT.
Thanks,
Steve
 
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