Props H3 Fuel Rod Cannon build log / Large 3D Printed Prop Support Questions

OFiveTwo and anyone else who may be interested in printing this bad boy once all the files are squared away I wanted to list what little hardware I'm planning to use in advance. Assuming everything plays nice once I get the barrel printed there will be a 250mmX8mm rod (advertised as a 3d printer z axis guide on amazon) and a 305mmX14mm compression spring fitted inside the barrel to allowing it to extend. The rod is mainly to keep the spring from bunching up behind the barrel as it moves back and will offer minimal support. The bearings I plan to use are these and should only require 2. If all goes well I should have the barrel and enough of the middle printed by the weekend to say with confidence that the above mentioned rod/spring combo will work as intended. Primary supports for the barrel will be printed nubs or small googly eyes affixed inside the area the barrel will move in hopefully limiting side to side wobble. This is where I'm at after 2 weeks of daily printing.

13 more days to go!

Edit: The spring I got is WAY too hard to compress. Will look for alternatives that can work with the guide rod
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I might want to make myself one of these
I'm just about 3kg of PLA in at this point. Total length once its finished will be around 110 CM. I'd be curious to see how fast some of y'all would be able to paint this once I get the files wrapped up.
I was loosing a little faith on this project, worrying my math, scaling and/or 3D design was flawed somewhere. Some parts were ever so slightly misaligned, nothing a bit of sanding and bondo won't fix but just enough for me to panic that something had gone wrong somewhere. I now know this is 99% a printer issue with my Z axis screw. I had my first case of horrendous Z banding on this project early on that came out of nowhere after printing a plasma rifle and H3 weapon holder. Cleaned and oiled the screw and things a basically back to normal. What little faith I was clutching to has been restored with each part printed. Everything fits in its place!
Everything is still due for a good sanding but I'm very happy with how well all these pieces are going together. Seeing all the custom details come to life is also a really cool thing for me. What was once a mess of vertices and polygons is on the way to being a ( for the moment ) one of a kind prop! I'm very excited to be finishing the files so I can release them into the wild and watch others have the chance to show me how bad my painting skills are.
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2 more prints and the body will be done! Sanding this is going to be something else... it may be a year before I start painting this, no idea when ill get around to finishing my suit at this point either
oh my GOD this looks so cool!!! This is 1000% on my print list now.
Have you thought about what you're doing for the fuel rod ammo? Had an idea where you resin print some lime green capsules and and leave in some resin on the inside or maybe even some glow stick liquid
oh my GOD this looks so cool!!! This is 1000% on my print list now.
Have you thought about what you're doing for the fuel rod ammo? Had an idea where you resin print some lime green capsules and and leave in some resin on the inside or maybe even some glow stick liquid
I was considering something with a two part liquid resin cast. No real thought has been put to this yet but it would be fairly simple to make a cast of the rounds and go from there. I may have some "clear" PLA somewhere to see what filling a hollow print with resin or something colorful as a test might look like.

Part of why I stopped working on this project last year was due to issues detailing this section. I just wasn't able to figure out how to replicate the game textures and took a long, long break on working on everything. I actually forgot about the entire thing until last month! Only took me like 10 minutes to actually finish the details on the big nub. To think I practicality rage quit on the whole thing due to that is kinda embarrassing.
Scary part of the build starts tomorrow. Will the barrel be able to move like I want it to? I actually have no idea, but here's the plan.
These two guide rods, once locked in place, will keep the whole barrel assembly on track as it comes into the receiver and should add some extra support to the whole thing.
Inside I have a recess carved out for a plug that will fit down into an opening on the rear of the barrel. This will be the rear mounting point for the spring that will attach up front. Notice the top is cut out for maintenance access. A plate will be present once finished to cover it.
I originally wanted what in universe appear as two recoil/dampening spring housings similar to what can be seen on modern artillery to be functional. While they don't really do much after all this, hooks will be added for the spring so that as the barrel moves to the rear, tension will be stored. Assuming the button that locks everything into a compressed or extended state works, enough force should be be generated to move the barrel out. If I cant get things working Imma just fix everything in place. The bearing system to rotate the hood is drafted out but I'll be saying a little prayer when all that nonsense prints.
So the whole moving barrel things is gonna get pushed back semi permanently. Turns out I DID missmeasure something! The opening for the guide rods dont go far enough into the barrel so when it retracts it either won't go far enough or pushes the rods backwards instead, this is not as intended. For the moment I'm going to salvage what I have. This will at the very least allow the whole thing to be field stripped to a point for transportation. If at a later date I want to try again I would just need to print a spare barrel, something I really don't want to do at the moment. Rest of the build is still on track to finish the rest of the large parts by Sunday night and the remaining small bits Monday or Tuesday.

This thing is getting heavy and I am quickly running out of desk space. Help
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What you can't hear is the super villain esque laugh I let out after taking this picture.

Quite literally some trash and a small screw driver holding the front in place until tomorrow when the axel prints. I just really, really wanted to see the final shape take form before bed.

I can only do this once before having to take everything apart to reset the barrel. This will be solved by mounting a lock to the back of the guide rods so they don't slip from their mounts. I'm not sure if I plan to glue the inner axel in place so that there's a little gap between the hood and the two arches. It's It's minor game detail and assuming I think it's strong enough to hold itself up I will. I won't be too torn if I let everything rest on the arches as it actually acts like a track for the hood when it moves back.

I see now that is is a fantastic feature as there's much less worry about the barrel snapping while it's like this! Definitely how I will store/transport it.
Alright, here's the link to all the files on Thingiverse: Halo 3 Fuel Rod Cannon

I've done my best to be set everyone up for success if you choose to print this, just please read the notes. I know there's a lot but they will help. File names for some parts will also show specific connection points for parts so the pile of support blocks hopefully becomes manageable.

This is a slight update to the one I printed with minor mesh fixes and an improved barrel lock that should work while its retracted and extended.

There is still room for improvement in some spots but its a freaking fuel rod cannon! By far the coolest paper weight on my desk right now and in time I may see ways to improve things.

But for now, enjoy!
May fortune grant you clean prints and minimal hand cramps when sanding

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