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  #1  
Old 05-08-2019, 09:39 AM
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timorley timorley is offline
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Default Pershing 1A Maxi-Brute Clone 3D Printed

In the 70s I remember being at Service Merchandise and they had all the Maxi-Brutes, but I had only enough money to buy one. At the time it felt like the hardest decision of my life. I finally settled on the Honest John, but I always wanted the Pershing 1A too. I do have a TLP Pershing on the workbench, but it's just not the same. Then back at the end of March I decided to get a small 3D printer to give it a try, rocketry parts was one of the reasons. After a few weeks, I realized how useful 3D printing was and decided to buy a bigger better 3D printer, which opened up all kinds of possibilities. Then early last week I stumbled onto this thread by Leo Nutz on TRF https://www.rocketryforum.com/threa...a-clone.150742/.

Holy smokes!

Leo has done a really good job putting together the 3D files and making them available for the rest of us to use.

This is my first large 3D project I've attempted, plus I decided to use PETG since it can be way tougher and tolerate heat (aka Sun) than PLA. But PETG can be a challenge, especially with stringing. I had several fails at first printing the nose cone, but finally it came together. Leo recommended spiral/vase mode, which is single wall, but I couldn't get 0.8mm wall thickness Leo's parts are designed for, it was always too thin. Switching from a 0.4mm to 0.8mm nozzle would likely solve it, but I don't have one. So I printed mine double wall in Standard mode, combined with slower printing speed for PETG, my print time was a little over 30 hours combined for the 3 nose cone sections! So yeah, like Leo I can't offer to print these for anyone either, sorry. The results turned out great!
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"You know, it, uh, won't fly unless somebody pushes the button." From the movie October Sky.

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  #2  
Old 05-08-2019, 09:40 AM
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Here are the 3 sections that comprise the nose cone.
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"You know, it, uh, won't fly unless somebody pushes the button." From the movie October Sky.

I am SAM # 0167
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  #3  
Old 05-08-2019, 09:42 AM
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Here are the section dry fitted. My caliper measures my wall thickness as 0.80mm, and the combined weight of the nose cone parts dry fitted is 113 grams in total. Wow, it's huge!
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Tim

"You know, it, uh, won't fly unless somebody pushes the button." From the movie October Sky.

I am SAM # 0167
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Old 05-08-2019, 09:46 AM
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Last night I printed one of the lower fins. Took about 2 and a half hours. Leo provided 2 versions of the upper and lower fins, one version is larger for flight like the Estes fins, and the other is scale. I'm printing the larger for the lower fins, although I might print the smaller scale fins for the the upper to help stability. The weight of the fin is 10 grams. 5 more to go!
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"You know, it, uh, won't fly unless somebody pushes the button." From the movie October Sky.

I am SAM # 0167
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Old 05-08-2019, 09:54 AM
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At what point does it become less expensive to buy your own printer and plastic stock than to buy from Shapeways, Boyce, etc.

I'm seriously considering a printer, but only if the quality of home printed stuff is good enough and cheap enough to justify the effort.
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Old 05-08-2019, 10:34 AM
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Quote:
Originally Posted by tbzep
At what point does it become less expensive to buy your own printer and plastic stock than to buy from Shapeways, Boyce, etc.

I'm seriously considering a printer, but only if the quality of home printed stuff is good enough and cheap enough to justify the effort.


That is a hard question with personal preferences mixed in. I'd liken it to changing your own oil versus taking it to a shop. I think it really comes down to how much of your time you are willing to put into it, how many uses you might have for 3D printing, and the personal satisfaction you can get from the I made that feeling. If you don't have a lot of time and much use for one, going the Shapeways/Boyce route is likely for the best. It can be a real time suck, especially if you also design your own parts. For this project I'm using the Amazon Basics PETG, which was $17.99 for a 1kg spool. So the nose was about $2.03 of material and the one fin about 18 cents. Your printer choice sort of depends on the quality you want coupled with how much time you are willing to invest in tuning the printer, versus having an out of the box experience. If you are willing to put the time into tuning the printer and printing parts to enhance it, you can get great results from the lower end printers versus a multi thousand dollar unit. My printer is a Creality CR-10S Pro, it was $650, but you can get decent printers like the Ender 3 that requires some assembly for a couple hundred. You just can't expect an out of the box experience like you can get with something like a MAKERBOT. I can't stress enough that if you buy one take the time at the beginning to learn how to level the print bed and how to make sure your prints stay adhered to the print bed during the printing process, it will save you a lot of frustration. The CR10S has been a much better experience than my MonoPrice in this respect. And there is the learning curve of how to setup your print settings and work with different kinds of plastics, but that you are going to encounter despite the printer. I did have a lot of frustrating failures are first trying to print this project, but now I think I have it down. I think my print at home results for quality is really good and the PETG is really tough stuff if printed properly. But then there is all that time waiting for the part to finish printing.......argh! On the flip side, my teenage daughter and I have had fun printing some non-rocketry projects too. I've also discovered several people here at work that have recently bought 3D printers, so we're sharing tips and experiences.
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Tim

"You know, it, uh, won't fly unless somebody pushes the button." From the movie October Sky.

I am SAM # 0167
NAR 98303 Southwestern Ohio Rocketry Association (SWORA) #624
https://www.rocketryohio.com

Last edited by timorley : 05-08-2019 at 11:02 AM.
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  #7  
Old 05-08-2019, 11:36 AM
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It seems that unless 3D printing becomes a hobby within the hobby, one would probably be better off purchasing finished parts, at least until prices, quality, and ease of use start falling into line. Thanks for your perspective. Looking forward to the finished model!
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Old 05-08-2019, 02:11 PM
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Tim (morley)-

Thanks for sharing your experiences here with the rest of us. I have wondered where Leo had run off to in recent years...sounds like he is spending his time on that OTHER forum....

Anyway, yes, your first-hand expereinces are just the kind of reports I have been wanting to read before jumping in myself. As tbzep said, I've been waiting for ease of use and, frankly, quality of output, to improve before jumping in. Even some of the stuff offered for commercial purposes, while improving, is still just a bit on the rough side for my personal tastes; but that is just me. But...it is getting better for sure. The photo of your Pershing fin looked great.

I really need to just purchase a commercial kit or part or two and do some full finish work on them to see just how much sanding, filling, and priming are necessary to get a good, quality finish on these parts.

Share more as you go, if you so desire. I suspect there are many here who want to learn and see more.

Thanks again.

Earl
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  #9  
Old 05-08-2019, 02:31 PM
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Here is a closeup of the fin surface. I haven't sanded anything yet, the pictures are as they came off the printer. I printed at a 0.1mm resolution and the surface is very smooth, you can barely feel any of the layering.
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Tim

"You know, it, uh, won't fly unless somebody pushes the button." From the movie October Sky.

I am SAM # 0167
NAR 98303 Southwestern Ohio Rocketry Association (SWORA) #624
https://www.rocketryohio.com
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  #10  
Old 05-08-2019, 03:05 PM
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I'm wondering where I'll wind up in total weight for the final rocket. The Estes catalog lists the Pershing 1A at 11.5 ounces (326.03 grams). Anybody have any real world weights for a finished Pershing? My BT-101 tube for this project weighs 88 grams. I'm going to set this up to accept the Estes E12-4, so I know that will require more nose weight than a D12-3 would. I believe there is roughly a 17.1 gram difference between a D12-3 and the E12-4 according to NAR data sheets.
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Tim

"You know, it, uh, won't fly unless somebody pushes the button." From the movie October Sky.

I am SAM # 0167
NAR 98303 Southwestern Ohio Rocketry Association (SWORA) #624
https://www.rocketryohio.com
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