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Posted: 2/21/2017 11:31:25 PM EDT
I have a SolidDoodle 2 3D printer and I've been meaning upgrade some of its parts. I'm CNC machining new parts to help add some more precision to the to printer as it shipped with 3D printed parts that had poor tolerances. The biggest issue it has is with printing round objects.
I thought making 66mm model rocket might be an ideal project to get me motivated. Does anyone know of a firearm spring .etc that is like the AR15 hammer spring but thinner and as strong? I need them to deploy the fins and the AR hammer spring is likely too powerful and bulky. The AR trigger spring would be more ideal but it doesn't have enough range. 
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Posted: 2/21/2017 11:40:31 PM EDT
[#1]
Ost
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Posted: 2/22/2017 2:46:48 AM EDT
[#2]
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Posted: 2/22/2017 3:05:15 AM EDT
[#3]
Quote HistoryI was thinking of a very lightweight replica that used the smallest motor possible lol. Likley a short duration E motor.
I'm trying to print a nosecone segment now after installing one of the newly machined parts to the 3D printer, its already printing smoother. Will be another 3 hours before it finishes. |
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Posted: 2/22/2017 6:16:41 PM EDT
[#4]
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Posted: 2/23/2017 2:23:47 AM EDT
[#5]
What CNC are you using? I'm saving up for a Tormach. When I got my Bridgeport I thought I was done. Buuut...
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Posted: 2/23/2017 3:55:16 AM EDT
[#6]
Quote HistoryQuoted:
What CNC are you using? I'm saving up for a Tormach. When I got my Bridgeport I thought I was done. Buuut... |
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Posted: 2/23/2017 5:40:25 AM EDT
[#7]
I made a replica out of PVC pipe once, it worked like a charm. WAY more accurate than I expected.
IMO I'd make two kinds of rockets, ones that look like the real deal, and a second set (and more of) ones that are just simplified to be fun to shoot. On the one I makes I just used D rockets and did fins that fit the tube diameter Set of 4 up front and 4 in back with enough space for decent balance. Was darn near POA/POI at 50 yards. 
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Posted: 2/23/2017 6:05:05 AM EDT
[#8]
Quote HistoryQuoted:
I made a replica out of PVC pipe once, it worked like a charm. WAY more accurate than I expected. IMO I'd make two kinds of rockets, ones that look like the real deal, and a second set (and more of) ones that are just simplified to be fun to shoot. On the one I makes I just used D rockets and did fins that fit the tube diameter Set of 4 up front and 4 in back with enough space for decent balance. Was darn near POA/POI at 50 yards. |
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Posted: 2/23/2017 9:01:58 AM EDT
[#9]
LOL I wouldn't even know where to find it, made i a long time ago.
Anyways, looking at the link put up above, looks like you can also buy re-loadable engines, and different solid fuels to fill them with. Also... on a lark I looked up what the LAW used for propellant... get this; " The smokeless propellants used in shoulder-launched ordnance are typically double base formulations of nitrocellulose and nitroglycerin. SMAW and M72 LAW use a well-known MIL-SPEC formulation called M7, which is widely used in various weapons systems." 54.6% NC (13.15% N)35.5% NG 7.8% POTASSIUM PERCHLORATE 1.2% CARBON BLACK .9% DIPHENYLAMINE So... LOL there you go, just got to find a model rocket propellant that comes in around those percentages (if they make it, it's basically super bangy gun powder) Reading some patent application stuff, the LAW is like the AT4 where all the propellant is burnt up before leaving the tube. (at4 is a recoiless rifle in function, the M72 just has a huge nozzle) which is why the backblast is so significant. Especially for the AT4 due to it's larger diameter. |
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Posted: 2/23/2017 9:15:05 AM EDT
[#10]
Quote HistoryQuoted:
LOL I wouldn't even know where to find it, made i a long time ago. Anyways, looking at the link put up above, looks like you can also buy re-loadable engines, and different solid fuels to fill them with. Also... on a lark I looked up what the LAW used for propellant... get this; " The smokeless propellants used in shoulder-launched ordnance are typically double base formulations of nitrocellulose and nitroglycerin. SMAW and M72 LAW use a well-known MIL-SPEC formulation called M7, which is widely used in various weapons systems." 54.6% NC (13.15% N)35.5% NG 7.8% POTASSIUM PERCHLORATE 1.2% CARBON BLACK .9% DIPHENYLAMINE So... LOL there you go, just got to find a model rocket propellant that comes in around those percentages (if they make it, it's basically super bangy gun powder) Reading some patent application stuff, the LAW is like the AT4 where all the propellant is burnt up before leaving the tube. (at4 is a recoiless rifle in function, the M72 just has a huge nozzle) which is why the backblast is so significant. Especially for the AT4 due to it's larger diameter. |
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Posted: 2/23/2017 10:48:21 AM EDT
[#11]
If your going to consider working with reloadable motors (Ammonium Perchlorate Composite Propellant), I would make sure to use one of the shareware programs for checking stability of you rocket design.
Depending on weight and of your rocket and size of the motor, it may approach or exceed Mach (probably not in your case though). |
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Posted: 2/23/2017 12:08:51 PM EDT
[#12]
Quote HistoryQuoted:
The formulas used in Estes motors are not considered explosives, where that particular mixture would likely be a big no no lol. Quote HistoryQuoted:
Quoted:
snip The next thing down the chart it's close to is mortar propellant charges LOL. It's just funny to think "rocket launcher" and you think the model rocket engines with some fancy solid propellant, yet the real LAW rocket is basically a big piece of ammo with the bullet pulled belching the "explosion" out the back. |
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Posted: 2/23/2017 12:21:10 PM EDT
[#13]
Quote HistoryQuoted:
Probably. I was surprised that it had a lot in common with some smokeless gun powders though. Way differnt ratios. The next thing down the chart it's close to is mortar propellant charges LOL. It's just funny to think "rocket launcher" and you think the model rocket engines with some fancy solid propellant, yet the real LAW rocket is basically a big piece of ammo with the bullet pulled belching the "explosion" out the back. Quote HistoryQuoted:
Quoted:
Quoted:
snip The next thing down the chart it's close to is mortar propellant charges LOL. It's just funny to think "rocket launcher" and you think the model rocket engines with some fancy solid propellant, yet the real LAW rocket is basically a big piece of ammo with the bullet pulled belching the "explosion" out the back. |
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Posted: 2/24/2017 5:11:15 AM EDT
[#14]
Some of the dimensions are off because I've determined the side-profile schematic isn't accurate, I'm going back and reworking some of the parts. I made the tail-fin holders a little beefier as well, I'll slowly reduce them in size until I get an ideal balance between being robust and authentic.
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Posted: 2/24/2017 7:36:01 AM EDT
[#15]
Ok, you have my attention.
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Posted: 2/24/2017 8:56:53 AM EDT
[#16]
Not for nothing but for some reason I was browsing a lot on the rocketry forum and there have been a fair amount of catastrophic explosions with the refillable motors. There is the same risk with the cardboard and plaster motors but when they explode they don't have the metal shell for
Containment. |
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Posted: 2/26/2017 3:40:15 AM EDT
[#17]
Believe I am satisfied with the motor housing and nozzle design. Going to print them now. Still need to find appropriate torsion springs for the fins.
Since the proportions on the drawings were a little off I am using the one seen in this photo for cross-reference 
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Posted: 2/26/2017 8:35:26 AM EDT
[#18]
Would it help if I let you borrow a real tail fin assembly?
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Posted: 2/26/2017 3:02:16 PM EDT
[#19]
Quote HistoryQuoted:
Would it help if I let you borrow a real tail fin assembly? |
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Posted: 2/26/2017 5:03:46 PM EDT
[#20]
Here is what I have now. Everything pieces together and had proper rocketry design for parachute deployment .etc
Likely will make some more adjustments to the nozzle area to help with 3D printing, but the warhead should be finished since it is based on the actual M72 tube diameter that I am able to measure. 
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Posted: 2/26/2017 7:10:24 PM EDT
[#21]
Quote HistoryQuoted:
If you could get me the diameter measurements of the motor tube, the widest part of the nozzle, and the base of the nozzle where it is narrowest I bet I'd be all set. Here you go, I opened up a new one for you: 
The tube diameter is 1.658", the nozzle is 2.285" at its largest opening, and the base of the nozzle where it is narrowest is 1.265". If you need any other measurements, just let me know. |
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Posted: 2/27/2017 5:11:18 AM EDT
[#22]
Quote HistoryQuoted:
Here you go, I opened up a new one for you: http://i302.photobucket.com/albums/nn115/kkrad_photo/5145beba940518e0e96495b1b216218d.jpg http://i302.photobucket.com/albums/nn115/kkrad_photo/57a1f0fd41950440bf3f635d9f0b8f62.jpg http://i302.photobucket.com/albums/nn115/kkrad_photo/3509d1297a177951f8e7dbf6d60cec79.jpg The tube diameter is 1.658", the nozzle is 2.285" at its largest opening, and the base of the nozzle where it is narrowest is 1.265". If you need any other measurements, just let me know. |
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Posted: 2/27/2017 5:39:57 PM EDT
[#23]
Really cool project! I'd be a bit concerned with an E engine, but that's without knowing the weight and if you were doing this vertically or horizontally, etc etc. We had a rocket design project in college and even with B engines we got quite a bit of altitude with some rather heavy rockets.
Quote HistoryQuoted:
True man portable rockets don't ignite until they are thrown by a separate charge well ahead of the user. Are you sure? I know some of them (RPG-7, Panzerfaust 3, MBT LAW, ERYX) do that, but I'm fairly certain that the M72, AT4, SMAW, and the RPG-29 fire off the main rocket inside the tubes. |
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Posted: 2/27/2017 6:21:42 PM EDT
[#24]
Quote HistoryQuoted:
Really cool project! I'd be a bit concerned with an E engine, but that's without knowing the weight and if you were doing this vertically or horizontally, etc etc. We had a rocket design project in college and even with B engines we got quite a bit of altitude with some rather heavy rockets. http://www.ar15.com/forums/manageReply.html?a=squote&b=3&f=123&t=709984&r=7392790&page=1# Are you sure? I know some of them (RPG-7, Panzerfaust 3, MBT LAW, ERYX) do that, but I'm fairly certain that the M72, AT4, SMAW, and the RPG-29 fire off the main rocket inside the tubes. |
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Posted: 3/2/2017 4:59:41 AM EDT
[#25]
The warhead is finished with the exception of smoothing and painting. It is made up of 4 assembled parts, but I will reduce this to 3 parts on the next run. The two large segments have tabs for the rubber band retention and parachute strings. With the exception of finding suitable fin springs everything else is now up to how long it takes my 3D printer to make each part. These parts took about 8 hours to print.
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Posted: 3/2/2017 9:04:09 PM EDT
[#26]
Those springs looks sorta like clothes pin springs.
Just sayin'. 
Definitely not the same by any stretch but just pointing out the similarities. |
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Posted: 3/2/2017 9:46:48 PM EDT
[#27]
Quote HistoryQuoted:
Those springs looks sorta like clothes pin springs. Just sayin'.
Definitely not the same by any stretch but just pointing out the similarities. |
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Posted: 3/2/2017 11:09:45 PM EDT
[#28]
Checkout Lee Springs torsion springs. I got some springs from them before for my 607 project, and was really happy with them.
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Posted: 3/4/2017 1:04:22 AM EDT
[#29]
Neat idea, BUT...
This COULD violate several laws depending on where you live. This in many states will be regulated by NFPA 1122. Make sure you aren't inadvertently "crossing the line". One item of concern under NFPA 1122 is the distance you must be from the launch vehicle when firing. |
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Posted: 3/12/2017 6:39:59 PM EDT
[#30]
If anyone has photos of the actual warhead I have a question about what appears to be some tooling tabs on the nose and tip. Wondering how many there are. Looks like 4 on the tip and maybe 2 on the nose.
Here is what I have now. 
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Posted: 3/12/2017 10:56:52 PM EDT
[#31]
Quote HistoryQuoted:
If anyone has photos of the actual warhead I have a question about what appears to be some tooling tabs on the nose and tip. Wondering how many there are. Looks like 4 on the tip and maybe 2 on the nose. Here is what I have now. http://www.ar15.com/media/mediaFiles/226828/IMG-9364-164458.jpg Here you go, there are four evenly spaced indentions on the nose cone, and three evenly spaced indentions on the body; 
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Posted: 3/12/2017 11:00:41 PM EDT
[#32]
Cool Thread.
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Posted: 3/12/2017 11:34:29 PM EDT
[#33]
Quote HistoryQuoted:
Here you go, there are four evenly spaced indentions on the nose cone, and three evenly spaced indentions on the body; http://i302.photobucket.com/albums/nn115/kkrad_photo/13d60b70c8264ac318063f186df43c8a.jpg http://i302.photobucket.com/albums/nn115/kkrad_photo/39d991909a6f926160f5a672204d49e2.jpg http://i302.photobucket.com/albums/nn115/kkrad_photo/06ea5a3f53856763d73c64505fc92753.jpg I wasn't sure I was going to even model them, but I decided I would because one of them can be used for a guide rod hole. |
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Posted: 3/14/2017 1:01:39 PM EDT
[#34]
I modeled the tabs into the nose cone and also added a guide rod tube hole
Next I'm looking for the following dimensions to get it perfect. 
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Posted: 3/14/2017 2:56:12 PM EDT
[#35]
Quote HistoryQuoted:
I modeled the tabs into the nose cone and also added a guide rod tube hole http://www.ar15.com/media/mediaFiles/226828/nose-repetier-2-165633.jpg Next I'm looking for the following dimensions to get it perfect. http://www.ar15.com/media/mediaFiles/226828/img-3758-165171.jpg http://www.ar15.com/media/mediaFiles/226828/img-3755-165170.jpg B= 1.37" C= .90" D= 1.275" E= 1.175" Please note that the top of the nose cone is NOT flat, but rather it is CONCAVE. |
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Posted: 3/14/2017 3:50:38 PM EDT
[#36]
Quote HistoryQuoted:
B= 1.37" C= .90" D= 1.275" E= 1.175" Please note that the top of the nose cone is NOT flat, but rather it is CONCAVE. Quote HistoryQuoted:
Quoted:
I modeled the tabs into the nose cone and also added a guide rod tube hole http://www.ar15.com/media/mediaFiles/226828/nose-repetier-2-165633.jpg Next I'm looking for the following dimensions to get it perfect. http://www.ar15.com/media/mediaFiles/226828/img-3758-165171.jpg http://www.ar15.com/media/mediaFiles/226828/img-3755-165170.jpg B= 1.37" C= .90" D= 1.275" E= 1.175" Please note that the top of the nose cone is NOT flat, but rather it is CONCAVE. |
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Posted: 3/15/2017 1:27:21 PM EDT
[#37]
Once I finish this nose cone my new warhead will be ready. Time to go print this.
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Posted: 3/15/2017 1:56:13 PM EDT
[#38]
Quote HistoryQuoted:
Thanks a ton! That is exactly what I needed. Now all I need is to find some springs. |
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Posted: 3/15/2017 1:58:28 PM EDT
[#39]
Nice modeling. What software are you using? A 3D printer is a valuable tool.
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Posted: 3/15/2017 2:22:38 PM EDT
[#40]
Quote HistoryQuoted:
Nice modeling. What software are you using? A 3D printer is a valuable tool. I used to make my living working on Expansion Packs for flight simulators. My old company and website is www.skyunlimited.net |
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Posted: 3/16/2017 3:15:41 PM EDT
[#41]
@M16indiana
Do you think you could measure the width and length of one of the fins for me? I just modeled them based on drawings and they just don't seem right. The Diameter of the rear launcher tube is 2.54" And we know the main tube is 1.66" That means the fins must be less than .44" wide? Another measurement I might find useful is from the nozzle to the beginning of the threads, and to the end of the threads (overall length of motor) I'll be able to print you out something to fit your spare motors this way :-) 
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Posted: 3/16/2017 8:39:15 PM EDT
[#42]
Quote HistoryQuoted:
@M16indiana Do you think you could measure the width and length of one of the fins for me? I just modeled them based on drawings and they just don't seem right. The Diameter of the rear launcher tube is 2.54" And we know the main tube is 1.66" That means the fins must be less than .44" wide? Another measurement I might find useful is from the nozzle to the beginning of the threads, and to the end of the threads (overall length of motor) I'll be able to print you out something to fit your spare motors this way :-) http://www.ar15.com/media/mediaFiles/226828/fins-1-167023.jpg |
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Posted: 3/16/2017 9:08:07 PM EDT
[#43]
Quote HistoryQuoted:
I really don't mind taking measurements for you, but would it not be easier if I just let you borrow one? |
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Posted: 3/20/2017 11:02:02 AM EDT
[#44]
I'm not sure if it would help you out much, but a guy over at the rpf made one for a Vietnam display including the rocket. I'll see if I can dig
Up that link. I am in the process of scratch building a Carl G. Non firing of course. |
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Posted: 3/20/2017 7:25:15 PM EDT
[#45]
This has been a fun thread to watch. Thanks for showing all the work you have done.
I got a law tube last fall to go with my collection and could not find a replica rocket anywhere to go with it. I found one company that made display rockets for training purposes, but did not make this rocket. |
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Posted: 3/21/2017 12:23:54 PM EDT
[#46]
I'll likely do a test launch in the next day or two. I'll be sure to record a video.
I'm also working on different methods to smooth up the 3D printed parts as I want the final product to look very realistic. This is a very heavy rocket compared to most model rockets weighing nearly a pound with engine. The Schedule 40 1-1/4" PVC tube I am using adds a good bit of weight but saves a lot of 3D printing time. Interesting thing is that the 1-1/4" PVC is the exact diameter of the real 66mm rocket motor tube. Here is current launch performance calculations for vertical flight. This is using an Estes D12 Motor. In comparison an Estes E9 could get 200ft and 70mph in vertical flight. 
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Posted: 3/21/2017 7:04:23 PM EDT
[#47]
It turned out very nice looking. Very cool. Looking forward to the video.
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Posted: 3/21/2017 7:58:32 PM EDT
[#48]
 M72 LAW Light Anti-Tank Weapon 3D Printed Estes Model Rocket |
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Posted: 3/21/2017 10:45:38 PM EDT
[#49]
If you'd be willing to sell these I'd be interested in snagging one for display use at the military museum I work with. Any idea how much one would run someone if you did sell a completed one?
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Posted: 3/21/2017 10:54:04 PM EDT
[#50]
Nice job
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