3D printable 38mm motor retainer and 38 to 29mm motor adapter

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Here is .stl file of the design. Hatchbox black ABS printed at 230°C, and bed at 100°C. 100% infill. Speed was 40 mm/s. No supports but I do use a 6mm brim though. 0.4mm nozzle, and 0.2mm layer height. First layer and brim at 30mm/s.

I might add, that I insulated the underside of the heat bed with cork, so I can get very consistent bed temperature there.

I use an enclosure, and pre-heat that. If I can get chamber to 40°C by bed and extruder heat alone, I call it OK. I use a glass build surface cleaned with isopropyl alcohol and then sprayed with Aquanet Extra Super Hold hairspray. I usually get tenacious bed adhesion at build temperature, and when it cools to room temperature I can usually just lift the print off by hand.

View attachment 38mm Motor Retainer.zip
 
I was doing a bit more investigation on using ABS 3D printed parts for high power rocket components. I came across this Thingiverse page, where the contributor made nose cone, motor mount, rail buttons, and even the fins from ABS. The fins slide into the motor mount through slots in the tube. He states that the rocket has flown 7 to 8 times with no apparent issues reported. I find this very interesting. There is also a linked video of the rocket flying, as well as an .ork file embedded in the download.

I can see more of my ABS filament being consumed in the coming weeks.

https://www.thingiverse.com/thing:2472771
 
3D printing is great. I have transitions and a 4" NC on my Nike Apache. Our work printer uses ABS. Build thread here is you are interested. https://forum.ausrocketry.com/viewtopic.php?f=6&t=5019

I should get the STL files and post on Thingiverse one day.

I have also done a 3" conical NC to suit the other conifguration for the NA. It takes the same sled.
 
What I find most interesting in the thingiverse link I posted, is that the motor mount has the motor retainer integral with it. The cap threads onto that, much like the standard two piece epoxy bonded type does. 7 to 8 flights with 38mm motors, and not one word about "melting" of any parts.
 
Yup. Machinist told me we couldn't have NaCA65A airfoils. Said impossible to CNC. And I got someone to SLS print what I designed. Because NASA doesn't think the general public should have NACA65A airfoil generators. NASA underestimates the general public of engineering students on coffee and excel yo with a copy of Solidworks... UTC SEDS competitions yo..

After placing third. NASA spokeswoman at SEDS SpaceVision says "I can not comment on that at this point in time." Screw NASA and it's you shouldn't have NACA65A airfoil generator attitude. NASA meet Excel..
 
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They don't want you or North Korea making supersonic zero lift airfoils. Lol.
 
Curve by equation and import by X,Y,Z points are the best things for rocketry with 3D programs.
 
Nytek1200CF by Stratasys has a good thermal load for 3D printable plastics. I was a tad disappointed in its strength. It is expensive. You could have a 6061T6 aluminum bar machined cheaper. Nylon itself is alright too. I dislike ABs outside of an AV bay. Low thermal load.
 
Machinist was impressed about printed airfoils. Guy is a metal snob. He had worked on tomahawks before being university machinist. He knew all about its jig process. But those tactics don't work for such small scale models. It starts with cones then retainers and soon you're trying airfoils like flavor of the month.
 
What's funny is you can't CNC based on a tool bit size and that's where the 3D print excels. A real dork would cast something from the print to save money in long haul or use better material.
 
If part size is too small the tooling itself has radius too large.
 
My upscale Quinstar has a 38mm upscale of the thingiverse retainer printed in PLA, as pictured above. Doesn't seem to have thermal problems with 38mm Gs. Cracks on landing :-(

I've also downscaled those retainers all the way to 13mm.
 
I don't know why more people don't print with PETG. Prints at 255°C, no toxic fumes, MUCH stronger than PLA, food and dishwasher safe. It's (almost) all I print any more. It doesn't bridge as well as PLA or it would be perfect!
 
Does anyone print in nylon? I was looking at a couple printers this weekend as a possible Christmas gift to myself, and I thought nylon might be interesting for our high-temp applications.
 
I print aerodynamic rail buttons in Nylon 910. A bit fiddly to work with, any strings are like trying to break mono-filament fishing line, but very strong and somewhat flexible. The biggest issues are that it absorbs moisture like a sponge, not a huge deal where I live, and no colors.
 
Nylons tend to be expensive, and a higher heat setting is typically needed (~250°C). And, I've never used / printed with it.

One thing a lot of seem to forget, is that we're building things quickly, out of a layered & deposited strand of plastic. These plastics were meant to be molded; heated to 'liquid' temperatures and injected into fully enclosed molds, then quickly cooled & removed. So that the part is one solid piece. It's "cool" 'cuze we can build something '3D' without pricey molds and 40+ tonne injection presses. But expecting it to replace established methods and materials in foolish.

Can I print a 54mm retainer, sure. I can design one too. (and put it thru our FEM lab if so inclined). Would I? No, I'll stick with a proven machined aluminum part. it's one solid piece, not plastic, and I don't have to futz with it. Would I print a camera shroud? Sure. An altimeter sled, probably. The scale model of the P&W J75? definitely..
 
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I print nylon, it's a pain sometimes. It warps easily, requiring an enclosure. It also needs very high temperature compared to PLA etc, and bed heating. PETG is a favorite of mine. Strong, easy to print, no fumes, lots of color options... For most things, nylon creates more problems than it solves. Same with Polycarbonate.
 
I print Nylon for Rail buttons, PETG for everything else. So far so good. Even the 54mm retainers. :) I will say to get a strength I'm comfortable with, I make them thick. They come in at nearly 4 Oz.
20171108_200106.jpg
 
I've flown my PETG + LOC 29mm MMT adapters in multiple rockets multiple times with DMS motors (e.g. H115DM). I guess I should share the design (this weekend)!

Also having good luck with 24mm and 29mm motor retainers. Looks like the Estes ones but I can print a set in a couple hours (0.1mm layers) for about 50 cents versus about $5 + S&H.

No melting on any of this, just white PETG turning gray from exhaust. Very happy with them!
 
I have used the 24 and 29mm screw retainers. I now just print one (PETG) for every new build.
I don't think they suffer much heat damage. No reason a 38 should be any different just epoxy the the threads to the base.
I have heard there are problems with PLA if its left in the sun, so suggest you use PETG or ABS just in case.
 
I have used the 24 and 29mm screw retainers. I now just print one (PETG) for every new build.
I don't think they suffer much heat damage. No reason a 38 should be any different just epoxy the the threads to the base.
I have heard there are problems with PLA if its left in the sun, so suggest you use PETG or ABS just in case.

PLA is also brittle if the retainer hits a hard surface. I've scaled them from 13mm to 38mm.
 
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