I'm wondering if anyone else has tried printing and fitting out the Liberty Ship that John Buttery put up on Thingiverse? http://www.thingiverse.com/thing:688183 It's 1:144 Scale and sectioned for a consumer sized printer. I'm roughly half way done printing the hull sections. I did have to rescale the parts by about a factor of 10 and I've used slicer to cut away superfluous discs that seem to be in most of the parts, but it's printing surprisingly well on my I3 Pro. I can't wait to glue it up and see how she floats. I'm thinking a 550 brushed motor and the prop I posted up in the resource section should probably work well, but if someones already been there and done that, I'd love to hear how it went?
A smaller 380 can motor or similar would be more than adequate for a liberty. 550 is a bit overkill, but it will work.
interesting. hadnt seen that model. Those discs are odd. At first glance I thought they were to help with bed adhesion, but then I saw that they were floating free of the sections. Strange business. Definitely post pictures of how it turns out. Are you doing ABS, PLA or something else (PET, nylon, etc)?
@absolutek: Would a 1-3/4" prop be too big for this? @NickMyers: I started this in ABS but, even with an enclosed print chamber and a heated bed, the bow section warped and cracked : ( That one section is too thick and could use some discs to help the corners stick but, I still think the rest would be difficult too. There are some pretty big overhangs etc. I was amazed that my I3 pro could bridge them as nicely as it is printing it in PLA. I'm curious to see how it works as a simple RC model first. @Tuboat: I've printed some test pieces to see how well a 3mm thick piece of PLA with 4 layers on each side will handle BB gun hits. My son and I will be testing that later. I'm thinking that for a convoy ship, one could print it thin and replace sections that can't patched or print it thicker with thin penetrable walls where the windows would be. After a few battles it could be cut out and sheeted with balsa.
I'm currently experimenting with the heat-curable PLA... I need to finish building the oven that will be used to cure the parts (basically hold them at 60C for 4-5 hours and they're good). If they are indded much more warp-resistant after curing, I will be printing one of these Lib ships in PLA
While I knew that this hull was too thin to stand up to fast gun armament, it needed to be properly tested. For Science : P Here's the result: https://rcwarshipcombat.com/threads/3d-printed-liberty-ship-live-fire-test.444813/
I had a little time this weekend to get back to this. After seeing how the hull tore out in strips when fired upon, I wanted to improve the toughness. I did a series of tests with 2" round targets and my sons Red Ryder BB gun. Test sample #8 proved to be surprisingly tough and I think I've found a good balance of thickness and strength with PLA filament that is easy to print with. It is only 4mm thick but, it stood up to 50 BBs fired at a range of 4 feet with no significant damage. I was going to test it to destruction but, I got bored. I didn't actually do the math but, I believe that the distance of 4 feet gives the BBs enough time to slow down from 350 feet per second to somewhere in the neighborhood of 250 fps. Pictures will be forthcoming.
If you can bring it to Nats, we can check with my new chronograph. It is supposed to be able to detect BB's. Thanks for bringing V1.0 to Ming's Moat. It was great to see.
How are you progressing on the EQ? I'm interested to see how it does so I know if I was a fool to sell it, lol.
I had a few hours to spend on some more destructive testing. I realized that my successes, thus far, were only due to the fact that they were flying out of the Shatter Blast disc holders and much of the energy was wasted. I made some clamping blocks out of wood that hold them very solidly by the rim and leave a 2 square inch round area in the center unsupported so, the material is really taking the impact and all the stress. I re-tested some of the last batch of samples to failure. Samples #7, #8, & #9 all failed after about 100 shots from a range of 3 feet. That's probably acceptable, but I thought I could do a little better. Samples #10 & #11 were not good at all but, sample #12 is the best so far. It's only 4 mm thick but, it's taken 325 shots from my sharp shooter's Red Ryder at a range of 3 feet with no real damage. The top layer of the print is starting to peel away. This time I've got pics. One is the clamping blocks with sample #9 in side, after it failed. The other is a close up of the damage to sample #12.
interesting some thoughts.. I've long believed, without solid testing behind that belief, that into the layer tops represents the strongest, most resistant to failure, orientation. however, if you're trying to plan for things like printing ribs, I don't think you'll have a wealth of luck achieving that orientation, and suspect that the only place you could consistently plan parts accordingly would be if you unwrapped your super structure elements to print flat. It would be interesting were you to repeat your testing in an alternative orientation as people are most likely going to print parts in an orientation that will subject the layers to edge impacting fire. have you experimented with a heat treatment of your PLA or with other materials?
I'm certain that you are correct about the orientation I'm testing being stronger than the other way. So much in fact, that I'm not really willing to invest the time to gather the data, but I encourage anyone who'd like to compare notes to do so. You brought up that Ribs will be difficult. I agree but, I've got some ideas. I haven't tried anything beside regular PLA. I think Tugboat was going to experiment with a heat treatable PLA filament? I eagerly await that report : )
It is fairly well established that FDM printers have asymmetric material properties. By that I mean that the printed part is weakest along the layer lines and strongest along the printed lines. You can think of it as similar to a carbon fiber composite, strongest along the direction the fibers run and much weaker when subjected to force across the fibers as the binder has to absorb the energy instead. With FDM there is no resin binder but the layer bonds are normally weaker than the extruded filament and so the behavior is similar. Your test liberty ship shows this behavior as the BB impacts tore out large sections along the layer lines. However, this is probably the only practical orientation to print a ship with on a home printer. Thicker walls will help but the only way I see a 3D printed ship working will be with a slightly ductile material such as PETG or Polycarbonate so that the material has a little give allowing it to absorb energy. ABS and PLA just don't like impacts very much and a hull will get hit a lot. However sheeting with a flat printed part and then placing it over a window cutout would probably work fine so long as it isn't too many layers. The multiple flat layer orientation should prevent the catastrophic failures seen in the Liberty ship.
Jason, Finish your boat! Or you will see first hand, distructive testing. The pond is the real enemy not BB's.
Hehehe. Time is the real enemy... Anyway, I have a feeling both kinds of destructive testing are in my future : )
