How to hold motor case to body tube?

[FA_95]

What other ways can I attach an aluminum motor case to the body tube? Is it through engine retainers along with bulkheads? or just use shear pins?

 

[BrAdam]

Maybe go to a couple local launches first and talk to some people about the hobby. Then come back here and ask some questions.

 

[Andrew_ASC]

You can friction fit the casing to a body tube by wrapping it in tape. Roll the tape around the outer diameter of the casing near the aft closure. Keep shoving the casing in until it won’t come out by hand. You may have to adjust tape layers.

Aeropac also makes engine retainers which you screw to rocket bulkhead or something I’ve always done friction fit with masking tape since it’s cheap.

 

[Christopher D Shramko]

https://www.apogeerockets.com/Advanced_Construction_Videos/Rocketry_Video_17
https://www.apogeerockets.com/Advanced_Construction_Videos/Rocketry_Video_83

 

[Bat-mite]

All motors need aft and forward retention: forward retention keeps the motor from shooting up through the airframe and out thru the nose cone. Aft retention keeps the motor from being blown out of the airframe backwards when the ejection charge fires, as well as simply falling out.

I've yet to meet a commercial or even an EX motor casing that doesn't have a thrust ring of some kind. This provides forward retention.

There are a number of ways to do aft retention. IMO, the best is to use an aluminum retainer which you epoxy onto the motor mount tube. Aeropack, MAC Performance, and GLR Slimline are popular. You could also use screws and washers, pipe clips, etc., any kind of hardward that can be slid into and out of place and locked down.

Or, as mentioned above, friction fit with tape. I don't like using tape. It is labor-intensive and can leave a residue over time. But it's cheap.

 

[dr wogz]

Aeropac also makes engine retainers which you screw to rocket bulkhead or something I’ve always done friction fit with masking tape since it’s cheap.

Actually, they glue on (JB Weld recommended). A few of the larger ones come with a drilled flange in which you are supposed to screw it to the aft CR..

 

[jlabrasca]

Maybe go to a couple local launches first and talk to some people about the hobby. Then come back here and ask some questions.

Yes. Do this.

What other ways can I attach an aluminum motor case to the body tube? Is it through engine retainers along with bulkheads? or just use shear pins?

It would also probably be worth your time to build a kit or two, to learn what the parts are called and to understand how things go together.

 

[David Schwantz]

Boy I have answered the "how high', "how far", and "how much" questions for 40 years now from kids and their parents. If we would have had attitudes like yours our RC hobby would have died LONG ago. What a way to turn off a new guy.

 

[grouch]

Really?? The answers he seeks take all of three minutes to find. I think advising to attend a local launch is the best advice that could be given. Not only will an interested person learn all sorts of things including motor retention but they can also get exposed to rockets they may have not know about such as saucers and pyramids. Everyone likes minimum diameters and that tends to be reflected in build threads but there are plenty of other types they may enjoy watching more. How is telling someone to see all this real life a slight???

 

[solid_fuel]

"how high', "how far", and "how much"

these are not questions that are likely to lead to dangerous acts either. This question along with his other post lead one to believe this guy has never built even an A motor rocket and he wants to make a high power rocket his first build? that's how people get hurt or property gets damaged and this hobby gets regulated out of existence. Start small and work your way up to the big stuff.

 

[Andrew_ASC]

He needs a NAR or Tripoli membership to proceed safely. That way whatever he does is insured.

 

[cherokeej]

He needs a NAR or Tripoli membership to proceed safely. That way whatever he does is insured.

That couldn't be further from the truth.

Membership will provide insurance only if all safety procedures and rules are followed at a sanctioned launch. It will not insure "whatever he does."

And there is no need to have a membership "to proceed safely." But a desire to keep all senses and extremities intact helps a lot.

 

[David Schwantz]

It is how you said it! Actually the both of you. Have a great day.

 

[Dad Man Walking]

David, welcome to the forums. Please don't hold some of the attitude on display in this thread against the entire community. We do get a few inquiries from noobs who are obviously trying to do things that are stupid and/or dangerous, and those questions deservedly get a good keyboard-lashing. We work very hard to make sure the hobby is conducted safely, so as to not attract too much attention for the wrong reasons. And some dumb-ass trying to go from zero to Mach 2, knowledge-wise and experience-wise, is not the type of person we want to encourage.

But I read none of that in your original question. Seemed to me you were asking "how do you retain motors in an MD rocket?" But that was just a guess, because of how you asked the question. So what I would have done had I gotten here earlier was to say something like this:

I'm not sure if I understand what you are trying to accomplish. Are you asking about motor retention for minimum-diameter (MD) rockets? That can be done with retainers on top of the motor, or at the aft end, or with nothing more than tape (something I've never tried so I can't be any help there). Shear pins aren't used for motor retention.

Tell us more about what you are trying to do (or just learn more about) and there's lots of people here who will be happy so share their experience."​

If you declared yourself to be a dumb-ass in your reply to that message, well then, let the keyboard lashings begin. But I don't think that would have happened.

To a few of the members here...if you were worried about David's experience and intentions based on his question and low post count, you might have taken a minute to look at his other posts, including this one:

https://www.rocketryforum.com/threads/first-loc-4-phoenix.147224/

You would have seen that he had built (and presumably flown) other rockets, has probably been to launches, probably has some crazy skills base on the way that large RC plane in the background looks, and is just interested in how things work as he moves up. He's not asking how to put a BP rocket into orbit, or what motors he should use for his flying Iron Man suit, or anything like that. Switch to decaf, man!

 

[solid_fuel]

That’s all well and good if FA_95 and David Schwantz are the same person. Are they? I’m going with no. Since one is listed as a 22 year old and the other one is 58.

 

[Andrew_ASC]

I mis-typed something rather important and David corrected my mistake. No need for lashings here. I do worry FA_95 is over his head and needs guidance by a mentor. I remember starting with scratchbuild competition multistage L-1 rockets for an engineering class without a mentor and only Estes LPR experience: it was rather intense. Much like FA_95 I was doing a bunch of Internet research all that I could in a team for a semester while playing with open rocket and cad. Then we had to build it and fly it.

The struggle is until you fly it the danger is underestimating forces involved and screwing up the build process in a bunch of little mistakes that someone else with more experience would catch. Stuff that isn’t in books or technical manuals. Field experience. Knowledge that people pass down by verbal or lectures at launch sites from experience they gained flying high power rockets. It’s all the recovery rigging details. The epoxies and materials. The interstage design concepts. Staging concepts if multistage. Everything matters. Motor selection. Electronics settings. Deployment charges. Parachute packing techniques. It all matters.
The practical flight side is the scary side that will bite a noob hard having been there. Motor selection I would call the hard part. You want a motor with moderate burn time and low acceleration below electronic limits on the rocket. Don’t pick a Extreme short burn motor high thrust for minimum diameter rockets.

When you realize you are attempting a higher risk activity and approach it in a safe cautious manner where you ask every question you can think of you are reducing risks. We started with minimum diameter rockets. It’s not impossible to go from zero to Mach 2. It is very risky however. And I don’t recommend it. They told us we would fail a year of college if we didn’t do it. So we figured it out and it took two launches to get it to work.

I think FA_95 is doing the right thing by asking the forum. This forum I called invaluable. It became a mentor away from a mentor. Sorry for the side rant. Apogee has wonderful articles on stability. FA_95 has posted multiple inquiry threads and is doing no harm by researching. Zero to Mach 2 on a single stage L-1 is a lot easier than a first scratch multistage. A stable safe rocket will cause no harm to hobby no matter it’s mach number. Just respect it more as Mach goes up please. There’s my big old wall of text. People may disagree with my views here.

 

[Dad Man Walking]

That’s all well and good if FA_95 and David Schwantz are the same person. Are they? I’m going with no. Since one is listed as a 22 year old and the other one is 58.

My mistake, for some reason I thought that David was the original poster. Does not change my intent of my message. Seek to understand what the poster is asking and why before basically saying they don't belong here...

 

[solid_fuel]

I never said FA_95 doesn’t belong here. I said he shouldn’t be starting with a high power minimum diameter as his first ever rocket. He most certainly does belong here. Here is where he can learn to start small with some low/mid power kits and work his way up to the big/fast/high stuff. He will have a much better/cheaper experience if he learns the basics first.

 

[DM1975]

For what it’s worth my son used friction fitting for his L1 motor, an Arrotech H283ST single use.

 

[Andrew_ASC]

It all started with a minimum diameter Wildman Blackhawk 29 on a CTI Pro 29-4G. Single deploy and motor eject. This was what our professor’s first ever choice to L-1 cert on as a first rocket. It worked the first time without a tracker. The casing was friction fitted for the naysayers. This was the baby step into the scary multistage MD shark tank of a pool. Dr. Elliot is in the blue shirt, I’m to the immediate left first row.

Just because you shouldn’t start with one doesn’t mean you can’t. There rants off.

 

[David Schwantz]

Hi Dad, as you saw, I am NOT the OP. All I was stating was that is not, IMO, how to treat someone. New guy or not.
Our RC hobby membership is dwindling. That is the start of the end. RC is now being governed by the FAA, we need to register with them in order to fly my toy airplanes. It has happened due to some drone fliers doing what they should have not. And not flying safely.Now we all are grouped in with them. You do not want that with rocketry. Think of having to register your rockets with NASA. But, as we get older and no longer fly, for whatever reason, this sport will end if new guys do not get involved. And just think, we all were new guys at some point.
Safety is the main concern, you do not know if someone does not teach you. I happen to be a JPO certified turbine pilot in both rotary and fixed wing, and am also an AMA large aircraft inspector and contest director. But I am a new guy in HPR. Have flown rockets for over 50 years, all hobby stuff. I am looking forward to advancing with my grand kids getting into it now as my son did with me many years ago. I cannot think of what I would have done for hobbies all these years if someone would have been rude to me that first day.

 

[Andrew_ASC]

These people can be mean on the forums. In nature they can be extremely competitive at launch sites. Everyone pitches in and helps a new flyer do an L-1 when you actually show up in person they are nice. Literally I’ve had people loan me over a hundred dollar motor cases in person and bring rocket motor reloads from other states when vendors weren’t an option for a second certification flight. Random people on the internet that just love this hobby, lol. People want to show you the right things to do in this hobby, but in person it works better.

 

[DM1975]

These people can be mean on the forums. In nature they can be extremely competitive at launch sites. Everyone pitches in and helps a new flyer do an L-1 when you actually show up in person they are nice. Literally I’ve had people loan me over a hundred dollar motor cases in person and bring rocket motor reloads from other states when vendors weren’t an option for a second certification flight. Random people on the internet that just love this hobby, lol. People want to show you the right things to do in this hobby, but in person it works better.

I agree with this. I’ve never met a more helpful group of people than at a rocket launch.. period! That’s not to say we don’t have our few “winners” but it’s an exception and not the rule in my experience. Even people I bump heads with regularly on line are actually very helpful and friendly. I believe that social media changes who we choose to be and how other see us due to the nature of the environment. Not always on purpose, but mainly from the lack of visual and tonal cues that we use in person to convey our points.

 

[Bat-mite]

Let's keep in mind that we are always one accident away from an FAA or an ATF crackdown on our hobby. Safety is of utmost concern, and I think there is an oversensitivity to the occasional post that sounds like an immature person getting in way over his head. We've all seen it:

"Hi. I'm 16 and I am interested in rocketry. What do I need to buy in order to launch a rocket to $100,00 feet with tumble recovery? Oh, and I have $100 to spend. Thanks."

Mr. Schwartz, I would value your opinion on how to answer this poster. Usually, our response is, "Go to a launch, learn about rocketry, and then come on back with specific questions." I don't see the rudeness in that, personally, but I would genuinely like to know what you would consider the right way to answer. Thanks.

 

[grouch]

View attachment 360848 View attachment 360847
It all started with a minimum diameter Wildman Blackhawk 29 on a CTI Pro 29-4G. Single deploy and motor eject. This was what our professor’s first ever choice to L-1 cert on as a first rocket. It worked the first time without a tracker. The casing was friction fitted for the naysayers. This was the baby step into the scary multistage MD shark tank of a pool. Dr. Elliot is in the blue shirt, I’m to the immediate left first row.

Just because you shouldn’t start with one doesn’t mean you can’t. There rants off.

Andrew, you have to understand that many launch sites are not like the one you posted. It would be relatively easy to find a rocket such as your team rocket there, it would be just a function of time and knowing the winds aloft. You would not have recovered that flight in the North East. Also, more than a few launch sites have a prohibition on friction fitting. It because nay sayers or anything like that but because the sites are located on active farms and the last thing a property owner wants is a motor case laying out in their pasture to damage something of theirs. Simple rules to follow unless you are 15 and insist on flying minimum diameters. I normally would agree with your last statement but lost flying sites don’t come back. We have lost two in the last few years in North Texas and it sucks. Willy Nilly attitudes play heavy sometimes.

 

[Andrew_ASC]

We drove to UROC, a three day trek by car. They had the waivers high enough.

 

[grouch]

No joke Sherlock.

 

[DM1975]

Even with friction fitting on a HPR I still use a secondary retention method. And that’s only if I can’t find a suitable fix such as aeropack retainers or screen clips to work properly for the rocket. I don’t think I’d ever use just friction fitting unless it was a single use motor possibly. Just because it happens to work most of the time does not mean that it will work every time. Too many variables such as no real consistency on how much tape is used. You may get it right 99% of the time but it’s that 1% that will bite you in the a**.

 

[GRIFFIN]

If the recovery harness is attached to the motor, I don’t see an issue. If for ANY reason the motor comes loose, it will still be connected to the cord and the rocket will be stuck in between that. I just flew a 36,000’ flight with a piece of masking tape holding in an N motor in place. Friction fit will work 100% of the time if done properly.

 

[grouch]

Well if the motor squirts out the back before ejecting the chute then you got problems.